REVIEW article

Front. Cell Dev. Biol., 29 May 2020

Sec. Cell Growth and Division

Volume 8 - 2020 | https://doi.org/10.3389/fcell.2020.00416

A Survey of Essential Genome Stability Genes Reveals That Replication Stress Mitigation Is Critical for Peri-Implantation Embryogenesis

  • Genome Integrity Unit, Children’s Medical Research Institute, The University of Sydney, Westmead, NSW, Australia

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Abstract

Murine development demands that pluripotent epiblast stem cells in the peri-implantation embryo increase from approximately 120 to 14,000 cells between embryonic days (E) 4.5 and E7.5. This is possible because epiblast stem cells can complete cell cycles in under 3 h in vivo. To ensure conceptus fitness, epiblast cells must undertake this proliferative feat while maintaining genome integrity. How epiblast cells maintain genome health under such an immense proliferation demand remains unclear. To illuminate the contribution of genome stability pathways to early mammalian development we systematically reviewed knockout mouse data from 347 DDR and repair associated genes. Cumulatively, the data indicate that while many DNA repair functions are dispensable in embryogenesis, genes encoding replication stress response and homology directed repair factors are essential specifically during the peri-implantation stage of early development. We discuss the significance of these findings in the context of the unique proliferative demands placed on pluripotent epiblast stem cells.

Introduction

Overview

Pluripotent cells in early mammalian embryos proliferate at a phenomenal rate. This is necessary to maintain embryo growth and reach critical developmental milestones within defined temporal windows. Because all somatic tissues are derived from these early pluripotent precursors, it is critical that genome integrity is maintained during early development. Embryonic pluripotent stem cells are thus subjected to unique challenges to maintain their DNA health. To elucidate which genome stability pathways are essential for early development we probed the Mouse Genome Informatics Gene Ontology Project (MGI-GO) database (Bult et al., 2019). Within MGI-GO we identified 347 genes grouped within the ontologies of major DNA repair pathways (MGI-GO designations: DNA damage checkpoint, nucleotide excision repair, mismatch repair, base excision repair, homologous recombination, and non-homologous end joining). Of these genes, we identified 297 with a validated mouse knockout. From these 297 murine models, only 108 gene knockouts were lethal during embryonic development (Supplementary Table S1). Within the grouping of 108 embryonic lethal genes, 10 knockouts were lethal during preimplantation development prior to E4.5 (Table 1), and 36 knockouts were lethal during somite stages from E8.5 (Supplementary Table S1). Notably, most of the targeted genes that conferred embryonic lethality, 62 genes, did so specifically during the period of rapid cell proliferation occurring with peri-implantation development (E4.5 to E8.5) (Table 2). Below we briefly review pre- and peri-implantation murine development before considering the function of essential genome stability factors across the early stages of embryonic development. Finally, we discuss why the unique cells of the peri-implantation embryo appear to specifically require replication stress response factors for cell viability.

TABLE 1

Targeted geneLethal atPhenotype detailsGene FunctionReferences
Ercc2 (Xpd)E1.5Mutant embryos do not implant. In vitro culture indicates embryo failure at the 2-cell stage.NER*de Boer et al., 1998
DtlE2.5Embryos develop to the morula stage but do not form blastocysts.CC, DDRLiu et al., 2007
PcnaE2.5Embryos do not survive to the blastocyst stage.Rep, BER, NER, MMRRoa et al., 2008
Rpa1E2.5Morula form but do not progress to blastocysts.Rep, HDR, NER, BER, MMRWang et al., 2005
Wee1E2.5Morula form but do not progress to blastocysts.CC, DDRTominaga et al., 2006
Nop53 (Pict1)Before E3.5Mutant embryos develop morphologically typical morula, but do not form well-structured blastocysts.CC, DDR*Sasaki et al., 2011
Cdk1Before E3.5Morula form but do not progress to blastocysts.CC, DDRDiril et al., 2012
Plk1E3.5Mutant embryos develop to the morula stage but do not form viable blastocysts in vitro.CC, DDRLu et al., 2008
Xab2E3.5Mutant embryos form morula and show some signs of compaction, but do not form blastocysts.NER*Yonemasu et al., 2005
Pot1aAfter E3.5Morula are recovered and can be cultured but do not form blastocysts.TelomereHockemeyer et al., 2006

Genome stability factors essential for preimplantation development.

Key: (E) = Embryonic day; DDR = DNA damage response/damage sensing; CC = cell cycle control; Rep = DNA replication and/or replication stress; HDR = Homologous directed repair; EJ = End joining pathways; BER = Base excision repair; NER = Nucleotide excision repair; MMR = Mismatch repair; Telomere = telomere protein. Gene functions are cross-referenced with the literature and may diverge from the MGI-GO categorization. Factors labeled with * indicate when the gene encodes a protein with additional functions outside genome stability that likely contribute to embryonic lethality.

TABLE 2

Targeted geneLethal atPhenotype detailsGene functionReferences
Zfp830 (Omcg1)E3.5Knockouts blastocysts form but fail to outgrow and do not induce an implantation response in vivo.CC, Rep, DDR*Artus et al., 2005
Actr2After E3.5Lethal after blastocyst stage.HDR*Zhang et al., 2007
Cdc7After E3.5Blastocysts form and can hatch. Outgrowth assays demonstrate with in vitro culture knockout embryos have a small ICM population by E5.5.CC, Rep, DDRKim et al., 2002
Chek1After E3.5Blastocysts form in vivo but are resorbed following implantation. In vitro cultured blastocysts have elevated apoptosis in ICM populations.Rep, DDRTakai et al., 2000Zaugg et al., 2007
AtrE4.5Blastocysts form, hatch, and show evidence of initiating implantation in utero. ICM outgrowth assays are consistent with wildtype embryos, but ICM populations succumb to apoptosis with continued culture.CC, Rep, DDR, HDRde Klein et al., 2000Brown and Baltimore, 2000Murga et al., 2009
Cdc25AE4.5Blastocysts form but suffer from impaired hatching ability.CC, RepRay et al., 2007
Ctip (Rbbp8)E4.5Embryos form blastocysts but fail to form an egg cylinder. Cells appear to suffer from reduced DNA synthesis.Rep, HDRChen et al., 2005
Recql4From E4.5Outcomes are dependent on the genetic manipulation. Deletion of exons 5–8 are lethal during gastrulation, deletion of exon 13 results in lethality just after birth.Rep, HDRHoki et al., 2003
Rint1From E4.5Null embryos implant in vivo but are severely developmentally delayed and resorbed from E6.5. The ICM and trophoblasts initially outgrow in vitro, but proliferation fails after 6 days.HDR*Lin et al., 2013
Thoc1From E4.5Embryos form a blastocyst, hatch, and attach in in vitro, but suffer from reduced proliferation of the ICM after several days in culture. No embryos are recovered in vivo before E8.5, but decidua are present, suggesting the embryos die during gastrulation.CC, HDR, DDR*Wang et al., 2006
Apex1After E4.5Blastocysts form and attach but die soon after.Rep, BERXanthoudakis et al., 1996
Cdc45After E4.5Blastocysts form and can hatch. Blastocyst outgrowth assays demonstrate that after several days of culture the ICM mass is smaller or not present.CC, RepYoshida et al., 2001
Cdk7 (Cdks)After E4.5Decidual resorption at peri-implantation stages in vivo. In vitro cultured embryos demonstrate increased apoptosis in the blastocyst and severely reduced ICM proliferation.CC, RepGanuza et al., 2012
Fen1After E4.5Blastocysts form and hatch but are compromised during peri-implantation.Rep, EJ, BER,Larsen et al., 2003
Gins4 (Sld5)After E4.5Embryos form blastocysts that hatch and implant. Development is compromised after implantation as embryos do not form egg cylinders. Embryos attach in outgrowth assays, but after 2 days of culture the ICM becomes compromised.RepMohri et al., 2013
HinfpAfter E4.5Knockout blastocysts can form, hatch, and attach, but embryos do not survive past E6.5.CC, Rep*Xie et al., 2009
Mdm2After E4.5Embryos can implant but are quickly resorbed.DDRJones et al., 1995
Mnat1After E4.5Blastocysts form that are indistinguishable from wildtype littermates, but no embryos are found after gastrulation.CC, Rep*Rossi et al., 2001
Pold3After E4.5Blastocysts form, hatch, and attach in vitro but show reduced outgrowth compared to wildtype embryos. In vivo, no embryos are recovered at E7.5 consistent with embryo failure during gastrulation.Rep, NER, TLSZhou et al., 2018
Prpf19After E4.5Same as above.CC, Rep, DDR, HDRFortschegger et al., 2007
Ptpn11After E4.5Same as above.CC*Yang et al., 2006
Topbp1After E4.5Blastocysts form and hatch but are unable to attach to the tissue culture dish in vitro.CC, Rep, DDR, HDRJeon et al., 2011
Yy1From E5.0Knockout blastocysts, form, hatch, and outgrow normally in vitro. However, in vivo, embryos fail to form and egg cylinder and die during gastrulation.DDR, HDR*Affar El et al., 2006
Rad51Before E5.5Blastocysts appear normal, but post-implantation embryos fail to properly develop an amniotic cavity, display no discernible mesoderm, have a reduced proliferation rate, and elevated apoptosis.Rep, HDRLim and Hasty, 1996Tsuzuki et al., 1996
Thoc5Before E5.5Embryos are not recovered from the uterus from E5.5 suggestive of death during preimplantation or gastrulation.CC, HDR, DDR*Mancini et al., 2010
TimelessFrom E5.5Embryos display severe cellular disorganization during gastrulation.RepGotter et al., 2000
Brca1E5.5Growth arrest and impaired proliferation resulting in resorption.Rep, HDRHakem et al., 1996Ludwig et al., 1997
Mre11AE5.5Embryos compromised during gastrulation.Rep, HDR, DDR, EJXiao and Weaver, 1997Theunissen et al., 2003Buis et al., 2008
Nbn (Nbs1)E5.5Blastocysts form and hatch, but embryos are smaller after implantation and are resorbed around gastrulation.Rep, DDR, HDR, EJZhu et al., 2001
Ube2NE5.5Embryos are never recovered, and timed mating suggests that embryos die during gastrulation.HDRFukushima et al., 2007
Rad50Before E6.0Embryos are abnormal from gastrulation onset and are resorbed.Rep, DDR, HDR, EJLuo et al., 1999
Fh1E6.0Embryos do not appear to grow past the early egg cylinder stage.NHEJ*Pollard et al., 2007
BlmE6.5Reduced embryo size, epiblast population and mesoderm population. The primitive streak forms but there is increased apoptosis throughout the embryo.HDR, RepChester et al., 1998
Cops5E6.5Gastrulating embryos are smaller and cannot develop all germ layers. Embryos display elevated apoptosis.CC, DDR*Tomoda et al., 2004
Kdm1AE6.5Blastocysts form, hatch, and attach in vitro, but are developmentally stunted from E6.5.DDR, HDR*Foster et al., 2010
Usp7E6.5Embryos die during gastrulation due to reduced proliferation.Rep, NERKon et al., 2010
Xrcc1E6.5Epiblast cell numbers are reduced in early gastrulating embryos due to apoptosis and slow proliferation, which impacts lineage specification.EJ, BERTebbs et al., 1999
Pold1Before E7.5Knockout embryos form blastocysts at E4.5 but no embryos are retrieved at E7.5.Rep, BER, NER, MMRUchimura et al., 2009
Cul4ABefore E7.5Embryos form blastocysts in vitro that hatch from the zona pellucida with no ICM or trophoblast compromise. No characterization of lethality presented.CC, Rep, DDR, NERLi et al., 2002
Dna2Before E7.5No embryos retrieved after E7.5. The cause of lethality was not investigated further.Rep, HDR, BERLin et al., 2013
Rif1From E7.5Null embryos are lethal from gastrulation in some genetic backgrounds but are viable in different mouse strains. Dimorphism in embryo survivability observed where male knockouts survive but female knockouts do not.Rep, HDRChapman et al., 2013
Bard1E7.5Embryos do not develop past egg cylinder stage.Rep, HDRMcCarthy et al., 2003Shakya et al., 2008
Brca2E7.5Reduced embryo size and persisting Oct4 positive egg cylinder indicates retarded dermal commitment of epiblast cells.Rep, HDRSharan et al., 1997
Hus1E7.5Gastrulating embryos appear normal but are smaller than wildtype littermates. Development becomes severely delayed from mid-gastrulation.Rep, DDR, BER, NERWeiss et al., 2000
Ino80E7.5Knockout embryos implant as deciduas are found at E7.5, but embryos are resorbed during organogenesis.Rep, DDR, HDR*Min et al., 2013
Lig3E7.5Embryos are smaller from gastrulation onset and do not develop past mid-gastrulation.Rep, EJ, BER, NERPuebla-Osorio et al., 2006
PtipE7.5Gastrulating embryos display increased apoptosis. Embryos can be recovered in the early stages of organogenesis but are poorly formed.Rep, DDR, EJ, HDRCho et al., 2003
Rad51B (Rec2)E7.5Knockout embryos implant, but do not develop pro-amniotic cavities and are resorbed by E7.5.HDRShu et al., 1999
UvragE7.5Knockout mice die by E7.5 but no additional data is provided as to the cause of the lethality.EJ*Afzal et al., 2015
Wdr48 (Uaf1)E7.5Knockout mice die during gastrulation.Rep, HDRPark et al., 2013
Ercc3 (Xpb)Before E8.5No healthy embryos are recovered by early organogenesis. Embryos may be compromised earlier but no additional details are provided.NER*Andressoo et al., 2009
Ddb1Before E8.5Same as above.CC, Rep, DDR, NERCang et al., 2006
Palb2E8.5Embryos are developmentally retarded after gastrulation and die during organogenesis.Rep, HDRBowman-Colin et al., 2013
Rad51CE8.5Knockout embryos implant but are developmentally delayed, resulting in impaired gastrulation and resorption from E8.5.Rep, HDRKuznetsov et al., 2009
Rev3LAfter E8.5Blastocysts form but do not thrive in vitro. Embryos are smaller than wildtype littermates during gastrulation.HDR, TLSBemark et al., 2000
PnkpAfter E9.0Embryos are not recovered from the onset of organogenesis. No further details are provided as to the cause of lethality.EJ, BERShimada et al., 2015
Nipbl (Scc2)Before E9.5No knockout mice are recovered from the onset of organogenesis, but no additional data is provided.Rep, DDR, HDR, EJSmith et al., 2014
SrpqBefore E9.5Knockouts cannot be recovered from the start of organogenesis, implying that embryos die during gastrulation.HDR*Takeuchi et al., 2018
Ppp4CBefore E9.5Same as above.HDRShui et al., 2007
Rnaseh2BFrom E9.5Knockouts are smaller than littermates at gastrulation conclusion and die early in organogenesis.Rep, DDRHiller et al., 2012
Syf2E9.5Knockouts do not survive organogenesis. Embryos can implant but gastrulation does not proceed normally.CC, RepChen et al., 2012
Nsmce2Before E10.5Knockout mice are not recovered from the uterus by E10.5. Embryos recovered at E2.5 appear normal but do not thrive in vitro. The cause of embryonic failure is not reported.HDRJacome et al., 2015

Genome stability factors essential for peri-implantation development.

Key: (E) = Embryonic day; DDR = DNA damage response/damage sensing; CC = cell cycle control; Rep = DNA replication and/or replication stress; HDR = Homologous directed repair; EJ = End joining pathways; BER = Base excision repair; NER = Nucleotide excision repair; MMR = Mismatch repair; Telomere = telomere protein; TLS = Translesion synthesis. Gene functions are cross-referenced with the literature and may diverge from the MGI-GO categorization. Factors labeled with * indicate when the gene encodes a protein with additional functions outside genome stability that likely contribute to embryonic lethality.

Early Murine Development

Embryonic development consists of a series of events occurring in chronological progression. Murine development takes 19 to 20 days depending on mouse strain (Figure 1; Murray et al., 2010). Preimplantation development occurs between fertilization (E0) and the initiation of embryo implantation in the uterine wall (around E4.0). Following fertilization, embryonic cells are uniformly totipotent and identical until formation of the morula at E2.5 (Condic, 2014) (see Box 1 for a detailed explanation of cell potency). Within the morula cells undergo polarization and compaction (Humięcka et al., 2017). By E3.0 the embryo forms a blastocyst structure containing two distinct cell populations; an outer layer of multipotent trophectoderm cells that eventually derive the placental tissues, and an inner group of pluripotent inner cell mass (ICM) cells which primarily serve as precursors for the embryo proper (Morris et al., 2010).

FIGURE 1

FIGURE 1

Graphical representation of the early stages of murine development. At embryonic day 2.5 (E2.5) totipotent cells within the preimplantation morula are encased within a protective zona pellucida shell. From E3.25 the blastocoel cavity opens, and the embryonic cells differentiate into the inner cell mass (ICM) (pink) and the outer trophoblast (blue). By E3.5 the hypoblast (orange) has developed. During peri-implantation the zona pellucida shell is lost by E4.5 and the ICM are now termed “epiblast cells” (pink). The outer trophoblast cell layer continues to encapsulate the embryo and expands to form the ecto-placental cone that is the precursor for placental tissues. From E5.0 a pro-amniotic cavity opens and elongates. By E6.5 the embryo has implanted, the primitive streak (green) emerges, and the primordial germ cell populations form (yellow). The primitive streak continues to elongate and is accompanied by the formation of the distal node at E7.0. At E7.5 the primitive streak derived mesoderm extends around the embryo and divides the pro-amniotic cavity into the exocoelom cavity and the amniotic cavity. At E8.5 the exocoelom becomes the yolk sack. Between E8.5 and E9.5 the embryo turns, resulting in complete envelopment of the embryo within the supporting extraembryonic tissues. Embryo depictions are not to scale.

FIGURE 2

FIGURE 2

Lethality onset in embryos deleted for genome stability factors relative to developmental stage. Spatiotemporal heat map illustrating the timing of lethality for embryos lacking genome stability factors essential for early development. Genes are listed above and organized temporally relative to the reported timing of embryo compromise. Graphical depiction of normal embryo structure at the time of lethality is shown below and key developmental periods are highlighted. Gene functions according to the literature are color coded as follows: cell cycle regulation (CC, yellow); DNA replication and/or the replication stress response (Rep, orange); DNA damage response (DDR, red); Homology directed repair (HDR, pink); canonical and alternative non-homologous end joining (EJ, purple); telomere biology (Telomere, blue); base excision repair (BER, cyan); nucleotide excision repair (NER, green); mismatch repair (MMR, brown) and translesion synthesis (TLS, gray). Embryo depictions are not to scale.

Box 1.

Potency states. Totipotent cells are present in the embryo between fertilization and morula formation. They can give rise to any cell type from any stage of the animal’s life, including germ and placental cells. Pluripotent cells exist in the inner cell mass (ICM) and epiblast region of the developing embryo from the blastocyst stage to immediately prior to organogenesis. Pluripotent cells can give rise to any cell of dermal lineage (mesoderm, endoderm or ectoderm) but not placental or germ cells. Multipotent cells exist in newly formed tissues or organs and can develop into a limited number of cell types within their original dermal lineage.

Peri-implantation is the developmental period from implantation to organogenesis (E4.0 to E8.5). Implantation begins at E4.0 when the free-floating embryo contains 64 cells (Behringer et al., 2014). At this point, the embryo loses its glycoprotein zona pellucida shell and the outer trophoblast attaches to the uterine wall. Single cell transcriptomics demonstrate that at E4.0 the ICM has differentiated into two pluripotent cell types: the primitive endoderm (PrE, sometimes referred to as the hypoblast) and the epiblast (Mohammed et al., 2017). Peri-implantation development is associated with exceptionally rapid cell proliferation during “gastrulation,” which begins at E5.5 as the embryo elongates and a luminal pro-amniotic cavity opens in the center of the epiblast cell mass (Snow, 1976). At E6.5 the primitive streak emerges from the epiblast, and from the epiblast all three dermal lineages of the conceptus will arise (Tam et al., 1993). These are the ectoderm (nervous system and skin precursor), endoderm (gut precursor), and mesoderm (precursor for all other tissues) (Watson and Tam, 2001). Because continued gastrulation requires a critical mass of 1000 cells, delays in epiblast proliferation at E6.5 may result in the embryo forming a small primitive streak but developing no further (Snow and Tam, 1979; Tam, 1989; Power and Tam, 1993).

Between E6.5 and E7.5 the rate of epiblast proliferation is exceptionally pronounced, with some cell cycles completed in 2.2 h (Snow, 1977). Elongation of the primitive streak between E6.5 and E7.0 is associated with the first evidence of epithelial to mesenchymal transition (EMT) (Carver et al., 2001). EMT mobilizes epiblast cells to form the endoderm and mesoderm lineages, while cells that do not undergo EMT become the ectoderm (Acloque et al., 2009). At E7.5 the mouse embryo contains over 14,000 cells derived from epiblast progenitors. Proliferation slows at this point resulting in an increased average cell cycle duration of 8.1 h (Snow, 1977). There is evidence to suggest a that a specialized “proliferative zone” with sub 4-h cell cycles is maintained within the primitive streak after E7.5, however, definitive evidence remains to be substantiated (Tam et al., 2013).

Genome Instability Differentially Impacts Cell Viability in Pre- and Peri-Implantation Embryos

Embryonic lethality implies that one or more cell populations are compromised during development at the time of embryo failure. This may arise through DNA damage or genome instability, with multiple lines of evidence indicating that preimplantation embryos are more resistant to genome perturbations than peri-implantation embryos. For example, gamma irradiation-induced DNA damage at E6.5 or E7.5 confers apoptosis specifically within the epiblast (Heyer et al., 2000). Conversely, apoptosis levels are low in preimplantation embryos irradiated between E3.5 and E5.5, or during organogenesis from E8.5. It is therefore the epiblast that is particularly sensitive to these types of DNA lesions. Similarly, despite tetraploidy driving additional chromosomal instability in preimplantation cells (Paim and FitzHarris, 2019) chimeric mouse embryos with a mixture of diploid and tetraploid cells will develop through preimplantation before dying during peri-implantation (Horii et al., 2015). Notably, tetraploid sensitivity in vivo appears to be specific to the epiblast as embryos with tetraploid trophoblast cells and diploid epiblast cells can generate live pups (Wen et al., 2017). Mouse embryos containing a mixture of diploid and aneuploid cells will also develop to peri-implantation before the aneuploid cells are specifically depleted in the epiblast through apoptosis (Bolton et al., 2016).

As with somatic tissues, the tumor suppressor TP53 (p53) plays a central role regulating stem cell outcomes following genomic insult. p53 orchestrates growth arrest or apoptosis following activation of the DNA damage response (Mello and Attardi, 2018). Concordantly, inhibiting p53-dependant signaling pathways enables chimeric embryos made from tetraploid preimplantation murine embryonic stem cells (mESCs) to survive until birth (Horii et al., 2015). Deleting TP53 also reduced apoptosis levels in irradiated E6.5 embryos (Heyer et al., 2000) and extended the survival of embryos co-deleted for essential DNA repair factors (Jones et al., 1995; Haupt et al., 1997; Ludwig et al., 1997; Kim et al., 2002; McCarthy et al., 2003; Cang et al., 2006; Reinhardt and Schumacher, 2012). Not surprisingly, TP53 was identified as a critical mediator of apoptosis in the gastrulating epiblast (Laurent and Blasi, 2015). However, when activated in pluripotent stem cells, p53 also influences the expression of pluripotency factors to regulate differentiation (Lin et al., 2005; Li et al., 2012; Akdemir et al., 2014; Jain et al., 2016). p53 therefore functions through canonical and unique pathways in early development to regulate cellular outcomes. This highlights that our classic understanding of genome stability pathways may not strictly apply to early development or certain pluripotent cell types (Zaveri and Dhawan, 2018).

DNA Damage Response and Repair Pathways

Replication Stress Response

Somatic mammalian cells prepare for DNA replication in G1 phase by licensing replication origins and loading inactive Cdc45-MCM-GINS replicative helicase complexes (Bleichert, 2019; Miller et al., 2019). Cyclin dependent kinase activity promotes E2F transactivation to initiate replication at the G1/S transition (Kent and Leone, 2019). Replication then proceeds throughout the S-phase with origins firing in temporal coordination and DNA synthesis occurring across the entirety of the genome (Burgers and Kunkel, 2017; Limas and Cook, 2019). Intrinsic and extrinsic factors may disrupt replication fork processivity: a phenomenon known as “replication stress” (Zeman and Cimprich, 2014). Replication stress is sensed through the accumulation of RPA binding to its single strand DNA (ssDNA) substrate (Bhat and Cortez, 2018). When replication stress stalls DNA synthesis the replicative helicase continues to unwind its substrate exposing ssDNA for RPA coating (Byun et al., 2005). ATR kinase is the master regulator of the replication stress response (Saldivar et al., 2017). RPA coated ssDNA recruits ATR and its associated protein ATRIP (Cortez et al., 2001) to stalled replication forks through parallel pathways mediated by TopBP1 and ETAA1 (Kumagai et al., 2006; Bass et al., 2016; Haahr et al., 2016). Once localized to the stalled fork, ATR is activated and propagates a signaling cascade resulting in engagement of the replication stress response. This includes activation of the downstream effector CHK1 kinase to arrest S phase until replication stress is resolved (Zhang and Hunter, 2014). During the replication stress response, stalled replication forks are often remodeled into a four-way structure and protected before engaging one of many diverse repair mechanisms dependent upon the underlying stress the fork encountered (Quinet et al., 2017; Cortez, 2019).

If replicative stress is unresolved, arrested replication forks may collapse into one-ended double strand breaks (DSBs) (Ait Saada et al., 2018). Additionally, persistent replication stress can result in under-replicated DNA persisting through S-phase, the second growth (G2) phase, and into the mitotic (M) phase of the cell cycle (Mankouri et al., 2013). Specialized repair mechanisms address replication defects carried into mitosis (Minocherhomji et al., 2015), during which time the canonical DSB repair pathways are inhibited (Orthwein et al., 2014). Replication defects passed into mitosis can confer chromosome segregation errors resulting in aneuploidy (Burrell et al., 2013; Wilhelm et al., 2019), or if severe mitotic death (Masamsetti et al., 2019). If a replication stressed cell escapes mitosis this is often evident in the daughter cells where the under-replicated DNA is present as a scar in the first growth phase (G1) that is repaired in the subsequent S phase (Lukas et al., 2011; Spies et al., 2019).

Double Strand Break Repair

DSBs are a major threat to genome stability because a failure in repair may result in loss of an entire chromosome arm (Scully et al., 2019). Additionally, chromosome segregation errors resulting from inadequate DSB repair are rife with implications for genome instability, including chromothripsis and kataegis (Maciejowski et al., 2015; Ly and Cleveland, 2017). DSBs are sensed by Ku70/80 (Gottlieb and Jackson, 1993; Ochi et al., 2015), PARP1 (Ali et al., 2012; Liu C. et al., 2017), and the MRN (MRE11, RAD50 and NBS1) complex (Lee and Paull, 2005; Stracker and Petrini, 2011). MRN facilitates recruitment of the ATM kinase to DSBs (Uziel et al., 2003) while Ku70/80 recruits a related kinase DNA-PKcs (Hnizda and Blundell, 2019). Once recruited to the break, ATM is activated and engages downstream DDR pathways (Dupre et al., 2006; Maréchal and Zou, 2013). This includes phosphorylation of the histone variant H2AX (termed γ-H2AX when phosphorylated) within the break adjacent chromatin and assembly of factors at the break locus to facilitate repair (Rogakou et al., 1998). ATM activation also results in growth arrest, including activation of the p53 pathway (Banin et al., 1998). Subsequent repair of DNA breaks is then orchestrated by homology directed repair (HDR) or end-joining (EJ) pathways.

Homology directed repair utilizes the homologous sister chromatid as a template for repair and is thus limited to the S and G2 cell cycle phases (Hustedt and Durocher, 2016). HDR initiates with resection at the broken DNA end to provide a 3′ ssDNA overhang for insertion into homologous regions of the sister chromatid (Symington, 2016). Once resection occurs at a canonical two-ended DSB, a series of enzymatic steps facilitate strand-invasion of the broken end into the sister chromatid, formation of a displacement-loop, template copying from the invaded DNA end, potential formation of a “Holliday Junction,” and resolution of strand invasion (Scully et al., 2019). HDR factors also function within the replication stress response though diverse mechanisms including the remodeling and stabilization of stressed replication forks into four-way structures prior to repair (Neelsen and Lopes, 2015). Additionally, HDR factors participate in resolving one-ended DSBs that arise from collapsed replication forks to restart replication (Ait Saada et al., 2018). HDR is thus intrinsically linked to the replication stress response.

Conversely, EJ involves the covalent ligation of broken DNA ends to repair DSBs and thus does not require an additional chromatid template. End-joining mechanisms function in S and G2, but notably are the only DSB repair pathway available in G1 (Chang et al., 2017). Classical non-homologous end joining (c-NHEJ) directly ligates DNA ends, and if unregulated can also drive chromosome translocations (Ghezraoui et al., 2014) or telomere fusions (Celli et al., 2006; Van Ly et al., 2018). Cells can also engage alternative non-homologous end joining (alt-NHEJ), where DNA resection creates 3′ overhangs to align the DNA ends for repair through microhomology (Sfeir and Symington, 2015). This often requires a fill-in reaction by the error prone polymerase Pol θ which can introduce errors into the repaired sequence (Mateos-Gomez et al., 2015; Mateos-Gomez et al., 2017).

Nucleotide and Base Damage

In addition to DNA breaks, cells must also contend with damage to nucleotide bases, base mismatches, and bulky DNA lesions that distort the DNA double helix. Base excision repair (BER) mends small non-distorting DNA lesions such as oxidized DNA bases (Wallace, 2014), while nucleotide excision repair (NER) corrects bulky lesions such UV-induced pyrimidine dimers (Schärer, 2013). BER is mediated by DNA glycosylases that cleave and remove the damaged bases at the lesion. A correct base is then inserted by specialized DNA polymerases (Wallace, 2014). In NER, a 25–30 nucleotide patch of ssDNA containing the bulky lesion is excised from the double strand helix before specialized DNA polymerases fill in the ssDNA gap (Schärer, 2013). Mismatch repair (MMR) proofreads the newly replicated DNA to identify mis-incorporated bases (Liu D. et al., 2017). When a mismatch is identified, the newly synthesized strand is nicked and resected creating a patch of exposed ssDNA for fill in by a high-fidelity DNA polymerase.

Essentiality of DNA Repair During Embryogenesis

Not all DNA repair activities are essential for early development (Supplementary Table S1). The most striking example is the dichotomy between the major DSB repair pathways. While many HDR factors are essential, the core c-NHEJ factors are either dispensable for development [Ku70 (Ouyang et al., 1997), Ku80 (Nussenzweig et al., 1996; Gu et al., 1997), Prkdc (DNA-PKcs) (Kurimasa et al., 1999), Nhej1 (XLF) (Li et al., 2008)] or only required for organogenesis [Lig4 (Frank et al., 1998), Xrcc4 (Dickinson et al., 2016)]. Some alt-NHEJ components are required for early development. Alt-NHEJ is promoted by the polymerase Pol θ which primes the DNA ends for repair by removing RPA from exposed ssDNA regions (Kent et al., 2015; Mateos-Gomez et al., 2017). Alt-NHEJ is also dependent on PARP-1, XRCC1 and LIG3 (Audebert et al., 2004), with PARP-1 having a critical role in synapsis, and XRCC1 and LIG3 mediating DNA ligation (Audebert et al., 2004). While Lig3 and Xrcc1 knockout embryos die during gastrulation (Tebbs et al., 1999; Puebla-Osorio et al., 2006), both genes encode factors that have functions in other DNA metabolic activities outside EJ (Wallace, 2014). Conversely Pol θ knockout mice are viable (Shima et al., 2004; Masuda et al., 2005), as are Parp1 knockouts (Wang et al., 1995), suggesting that alt-NHEJ is not essential for embryogenesis.

Preference for HDR over NHEJ is further evident in mechanistic studies of DDR engagement within embryonic stem cells (Tichy et al., 2010). Following DSB induction, ATM-dependent γ-H2AX phosphorylation at the break locus recruits the scaffolding protein MDC1 (Stewart et al., 2003). MDC1 subsequently recruits the ubiquitin ligases RNF8 and RNF168 that signal downstream recruitment of 53BP1 (Jackson and Durocher, 2013). 53BP1 then establishes a physical domain at the repair locus in coordination with RIF1 to inhibit end resection and HDR in favor of c-NHEJ (Chapman et al., 2013; Zimmermann et al., 2013; Lou et al., 2019; Ochs et al., 2019). Notably, many factors that promote c-NHEJ are dispensable for embryonic development, including Atm (Barlow et al., 1996; Xu et al., 1996), H2ax (Celeste et al., 2002), Mdc1 (Lou et al., 2006), Rnf8 (Valnegri et al., 2017), Rfn168 (Zong et al., 2019), and Trp53bp1 (53BP1) (Ward et al., 2003). Additionally, multiple reports demonstrate that 53BP1 does not localize to DSB foci in the ICM of preimplantation embryos or mESCs grown in culture (Ziegler-Birling et al., 2009; Kafer et al., 2016). In vivo, 53BP1 localizes to damage in E5.5 embryos, but only in the epiblast cells and not the endoderm or trophoblast cells (Laurent and Blasi, 2015). While Trp53bp1 expression is unchanged in early development, Rnf168 expression is limited prior to the epiblast stage which may explain differential engagement of DDR pathways in pre- and peri-implantation cells (Laurent and Blasi, 2015).

Genes Essential for Preimplantation Development

Consistent with a greater tolerance of genome instability in preimplantation cells, only 10 knockouts of genome stability factors that we reviewed were lethal during preimplantation (Table 1 and Supplementary Table S1). Factors encoded by many of these preimplantation essential genes also possessed critical functions outside DDR or repair. Additionally, preimplantation embryos commonly survive to the morula stage even if a targeted gene is essential for viability. This is because embryonic genomes are not immediately active following fertilization while the inherited maternal mRNA guides protein translation (Jukam et al., 2017).

Multifunctional Factors Essential for Preimplantation Development

Of the 10 genome stability factors required for preimplantation development, only Ercc2 deletion did not permit morula generation. Ercc2–/– embryos fail to develop past the 2-cell stage in vitro and there is no evidence of embryo implantation in vivo (de Boer et al., 1998). Ercc2 encodes the XPD helicase that functions both in NER and as a core component of the general transcription factor IIH (TFIIH) complex. TFIIH opens DNA and anchors the cdk-activating kinase (CAK) complex to facilitate transcription (Egly, 2001). Given that Ercc2 knockouts are compromised during embryonic genome activation (EGA), a reasonable conclusion is that preimplantation lethality is associated with a loss of XPD transcriptional activity. Likewise, Xab2 is a TFIIH and NER component and Xab2 deletion is lethal prior to the blastocyst stage (Yonemasu et al., 2005). However, Xab2 null embryos survive past the 2-cell stage suggesting Xab2 is not required for EGA.

Pcna and Rpa1 both function in multiple genome maintenance pathways and deleting either gene confers preimplantation lethality (Wang et al., 2005; Roa et al., 2008). PCNA (proliferating cell nuclear antigen) forms a homotrimeric sliding clamp that encircles DNA. The protein clamp travels with the replication fork to promote replicative polymerase processivity and mediate diverse functions in DNA replication and the replication stress response (Mailand et al., 2013). PCNA also functions in NER and MMR (Strzalka and Ziemienowicz, 2011). Rpa1 (Replication Protein A 1) codes for the 70 kDa subunit of the heterotrimeric RPA ssDNA binding complex that participates in replication, but which also functions in ATR activation, replication fork repair, HDR and NER (Bhat and Cortez, 2018). Analysis of Pcna mRNA showed a significant reduction of maternal transcripts from the zygote to the 2-cell stage consistent with the observed early embryonic lethality (Hamatani et al., 2004; Roa et al., 2008; Bult et al., 2019). Rpa1 null embryos form blastocysts at E3.5 that are smaller than their heterozygous littermates and which fail in blastocyst outgrowth assays, indicating Rpa1 is required for trophectoderm and ICM growth (Wang et al., 2005). While both Rpa1 and Pcna function in diverse aspects of genome maintenance, both genes are also required for DNA replication. Preimplantation failure of Pcna or Rpa1 null embryos likely stems from an inability to polymerize nascent DNA coupled with simultaneous attenuation of multiple DNA repair pathways.

Two additional genes classified as DNA repair factors in the MGI-GO database are also essential during preimplantation. Nop53 encodes a nucleolar protein with suggested roles regulating p53, DNA repair, and the cellular response to mitochondrial stress (Lee et al., 2012; Yoon et al., 2014). Nop53 null embryos fail to develop past the blastocyst stage, while Nop53–/– mESCs are viable, suggesting that Nop53 functions in morula to blastocyst maturation (Sasaki et al., 2011). In somatic cells, Pot1a encodes a telomere specific ssDNA binding protein that suppresses ATR and p53 activation by the chromosome end (Hockemeyer et al., 2005, 2006; Denchi and de Lange, 2007). Loss of Pot1a likely confers robust ATR activation which explains the failure of Pot1a–/– embryos to form an ICM (Hockemeyer et al., 2006).

Cell Cycle and Checkpoint Factors Essential for Preimplantation Viability

In the event of replication stress or DSBs, checkpoints slow the cell cycle to provide time for DNA repair. Deletion of several genes that encode checkpoint regulatory factors confer preimplantation embryo failure at the morula stage. These include Wee1 (Tominaga et al., 2006), Cdk1 (Diril et al., 2012), and Plk1 (Lu et al., 2008; Wachowicz et al., 2016). CDK1 promotes the G2/M transition through interaction with cyclin B, and CDK1-cyclin B activity is regulated by WEE1 (Harvey et al., 2005; Gavet and Pines, 2010). ATR and CHK1 activate the G2/M checkpoint by stimulating WEE1 to inhibit CDK1 (O’Connell et al., 1997; Nigg, 2001). Polo-like kinase 1 (PLK1) controls numerous mitotic activities, participates in the G2/M transition, may function in DNA replication, and is implicated in HDR through phosphorylation of RAD51 (Watanabe et al., 2004; Mandal and Strebhardt, 2013; Yata et al., 2014; Pintard and Archambault, 2018). Dtl is also required for preimplantation development (Liu et al., 2007). Dtl encodes a component of the CUL4A-DDB1 E3-ubiquitin ligase complex that degrades the replication licensing factor CDT1 to stimulate replication and S phase progression (Nishitani et al., 2001; Li and Blow, 2005). Because these essential cell cycle genes function in DDR-regulated checkpoints and normal cell cycle transitions, the mechanism of embryonic lethality following their deletion likely involves deregulation of both the DDR and normal cell cycles.

Genes Essential for Peri-Implantation Development

Peri-implantation is the period of embryonic development most associated with lethality following deletion of genome stability factors. Within the MGI-GO derived gene list, it stands out that 54 of the 62 genes essential for peri-implantation development have direct or indirect functions in DNA replication, the replication stress response, and/or HDR (Table 2 and Supplementary Table S1). Below we focus specifically on these pathways.

Genes Regulating Replication Initiation, DNA Polymerization, and the Replication Stress Response Are Essential for Peri-Implantation Development

Because of the rate of cell proliferation in peri-implantation embryos, it is perhaps unsurprising that factors which regulate the G1/S transition and initiate DNA replication are essential for peri-implantation development. This includes Cdc7 (Kim et al., 2002), Cdc45 (Yoshida et al., 2001), Cdk7 (Ganuza et al., 2012), Mnat1 (Rossi et al., 2001), Gins4 (Mohri et al., 2013), Cul4A (Li et al., 2002), and Ddb1 (Cang et al., 2006). Additionally, the Pold3 subunit of the replicative polymerase Polδ is required for peri-implantation development (Uchimura et al., 2009; Zhou et al., 2018), as is Fen1, which plays a central role in processing Okazaki fragments on the lagging strand of DNA synthesis (Larsen et al., 2003). Lethality following deletion of most of these genes occurs on or near E4.5 and is associated with proliferative failure within the ICM after blastocyst formation but prior to gastrulation. A likely explanation is that peri-implantation development is rapidly compromised when fundamental functions necessary for cellular proliferation and/or DNA replication are dysregulated.

Even in the absence of exogenous threats to replication, the exceptionally fast cell cycles within the developing epiblast are expected to confer intrinsic replication stress. For example, blastocyst derived mESCs display replication stress in unperturbed cultures in vitro (Ahuja et al., 2016). mESCs appear to manage this replication stress by effectively coupling replication and repair activities to facilitate near continuous DNA synthesis punctuated by brief G1 and M phases (Ahuja et al., 2016). Epiblast cell cycles in vivo are more rapid than cell cycles in cultured mESCs (Snow, 1977; Mohammed et al., 2017) suggesting that a similar reliance on efficient coupling of DNA replication and the repair activity is required to manage replication stress in peri-implantation embryos.

The replication stress response begins when ATR/ATRIP localizes to RPA-coated ssDNA, and ATR is activated through TOPBP1 and the RAD9-RAD1-HUS1 (9-1-1) protein complex (Kumagai et al., 2006; Navadgi-Patil and Burgers, 2009; Choi et al., 2010). 9-1-1 is a sliding clamp loaded onto DNA (Bermudez et al., 2003). TOPBP1 bridges ATR/ATRIP and 9-1-1, thereby stabilizing ATR at the fork. Once stabilized at the site of replication stress, ATR regulates downstream replication stress repair and cell cycle arrest via CHK1 kinase and CDC25A (Liu et al., 2000; Xiao et al., 2003; Delacroix et al., 2007). TIMELESS, a component of the replication fork protection complex (Kemp et al., 2010; Couch et al., 2013; Buisson et al., 2017), and the ubiquitin ligase PRP19 (Prpf19) (Maréchal et al., 2014), also function in ATR and CHK1 activation. Embryos null for Atr (Brown and Baltimore, 2000; de Klein et al., 2000; Murga et al., 2009), Topbp1 (Jeon et al., 2011), Hus1 (Weiss et al., 2000), Chek1 (CHK1) (Takai et al., 2000; Zaugg et al., 2007), Cdc25A (Ray et al., 2007), Timeless (Gotter et al., 2000), and Prpf19 (Fortschegger et al., 2007) are all compromised during peri-implantation.

In somatic tissues, ATR or CHK1 inhibition coupled with replication stress induces replication catastrophe and S-phase apoptosis (Myers et al., 2009; Toledo et al., 2013; van Harten et al., 2019). Similarly, Atr null embryos form blastocysts that in vitro display widespread apoptosis within the ICM but not in the trophoblast, and which are eventually compromised by day three of culture (Brown and Baltimore, 2000; de Klein et al., 2000; Murga et al., 2009). ATR activity is therefore essential in the pluripotent and rapidly proliferating epiblast cells that will become the embryo proper, but not in the multipotent placental precursors. Chek1 null embryos also form blastocysts, but unlike Atr null embryos, are unable to attach to the culture vessels in outgrowth experiments (Takai et al., 2000). The more severe embryonic response to a loss of CHK1 activity compared to ATR inhibition is consistent with observations in somatic cells (Buisson et al., 2015).

HDR Genes Are Essential for Peri-Implantation Development

Common HDR factors manipulate DNA substrates at two-ended DNA breaks and stressed replication forks (Ait Saada et al., 2018). During replication stress, this entails regressing and protecting stalled forks in 4-way DNA structures to facilitate repair (Quinet et al., 2017). HDR factors essential for peri-implantation that function in canonical DSB repair and replication fork protection include: Brca1 (Hakem et al., 1996; Ludwig et al., 1997; Taglialatela et al., 2017), Brca2 (Sharan et al., 1997; Lemaçon et al., 2017; Mijic et al., 2017), Rad51 (Lim and Hasty, 1996; Tsuzuki et al., 1996; Zellweger et al., 2015), Bard1 (McCarthy et al., 2003; Shakya et al., 2008; Daza-Martin et al., 2019), Palb2 (Bowman-Colin et al., 2013), and Rad51C (Kuznetsov et al., 2009; Somyajit et al., 2015). Similarly, common factors promote resection during HDR repair of canonical two-ended DSBs and at stalled replication forks (Ait Saada et al., 2018). This includes the essential peri-implantation genes: Ctip (Chen et al., 2005; Przetocka et al., 2018); Ptip (Cho et al., 2003; Ray Chaudhuri et al., 2016); Dna2 (Lin et al., 2013; Thangavel et al., 2015), and the MRN complex [Mre11, Rad50, and Nbs1 (Xiao and Weaver, 1997; Luo et al., 1999; Zhu et al., 2001; Theunissen et al., 2003; Buis et al., 2008; Schlacher et al., 2011).

Homology directed repair activity in replication fork remodeling and protection is an emerging topic in the DNA repair field, and it remains unclear which HDR functions are essential for cell viability. However, lethality in Brca2 null mESCs is rescued when fork protection is facilitated by inhibiting PARP activity to protect replication forks from MRE11 nuclease (Ding et al., 2016). For BRCA2, fork protection may be the essential function. In vivo, deleting factors that participate in both canonical HDR-dependent DSB repair and fork remodeling or resection, typically confers reduced cell proliferation and embryo failure during gastrulation. For example, Brca1–/– embryos are severely malformed with an underdeveloped pro-amniotic cavity and mesoderm (Hakem et al., 1996; Ludwig et al., 1997). Concordantly, Brca1 null embryos display a significant reduction of DNA synthesis by E6.5, increased p21 [a factor induced by p53 transactivation to mediate cell cycle arrest (Georgakilas et al., 2017)], and a high incidence of G1 arrested cells (Hakem et al., 1996). Similarly, Rad51 null embryos suffer from reduced proliferation and begin to degenerate during gastrulation by E7.5, but development can be extended to E9.5 in TP53/Rad51 double knockouts (Lim and Hasty, 1996). Loss of HDR factors therefore appears to primarily confer proliferative failure through p53-induced growth arrest and subsequently through accumulated genome instability if p53 function is compromised.

Additional Peri-Implantation Genes Linked to HDR or Replication

Peri-implantation development additionally requires several genes that are functionally linked to HDR or replication stress mitigation. Such genes include Apex1 (Xanthoudakis et al., 1996), Rnaseh2B (Hiller et al., 2012), Rif1 (Chapman et al., 2013), Blm (Chester et al., 1998), Rev3L (Bemark et al., 2000), Usp7 (Kon et al., 2010), and Ino80 (Min et al., 2013). Apex1 does not directly function in replication, but is critical for the repair of abasic DNA sites that if left unresolved confer replication stress (Boiteux and Guillet, 2004). Similarly, Rnaseh2B resolves RNA within RNA-DNA hybrids, including mis-incorporated ribonucleotides, which if not resolved can impede replication (Pizzi et al., 2015). In addition to functioning in DSB repair pathway choice, Rif1 also coordinates replication timing (Yamazaki et al., 2012; Foti et al., 2016). Blm encodes a helicase that functions in homologous recombination, the replication stress response (Davies et al., 2007; Machwe et al., 2011), promotes replication at telomeres (Barefield and Karlseder, 2012), and participates in a specialized form of break induced replication at chromosome ends (Sobinoff et al., 2017). Rev3L encodes the catalytic subunit of POL ζ which facilitates translesion synthesis to enable replication forks to negotiate lesions within DNA without stalling (Bhat et al., 2013). Usp7 is a deubiquitylating enzyme that promotes efficient DNA replication (Lecona et al., 2016) and Ino80 encodes a chromatin remodeling factor that functions in both replication and HDR (Poli et al., 2017).

Maintaining Genome Stability During Peri-Implantation Development

While HDR and replication associated genes are not the only genome stability factors required for peri-implantation development, their predominance on the list of genes essential for this developmental window is compelling. Conditions enabling in vitro culture of peri-implantation murine epiblast stem cells are now established (Brons et al., 2007; Tesar et al., 2007). However, there are no published studies focusing on genome maintenance in isolated epiblast cells. It is thus necessary to extrapolate from studies of other rapidly dividing cells why HDR and replication factors may be essential during peri-implantation development.

Replication Stress in Peri-Implantation Cells

The fastest cell cycles in the lifetime of a mouse are likely during the brief window of epiblast development. Outside of the embryo, rapid proliferation contributes to replication stress in hematopoietic and cancerous tissues by robbing cells of the time to properly execute DNA polymerization (Pilzecker et al., 2017). For example, during a somatic G1-phase replication is facilitated by increasing the abundance of MCM proteins and loading these factors at replication origins in preparation for S-phase (Boos et al., 2012). Late G1 cells also upregulate dNTP production for the oncoming burst of DNA synthesis (Hirschi et al., 2010; Dick and Rubin, 2013). When origins are not established properly, or dNTP production is dysregulated, cancer and aging hematopoietic cells are susceptible to replication stress (Flach et al., 2014; Aird and Zhang, 2015; Alvarez et al., 2015; Garzon et al., 2017).

Pluripotent cells in the early embryo display almost non-existent G1 phases and appear to use unique mechanisms to ensure S-phase progression is not impeded. For example, human ESCs counter G1 brevity by loading MCM proteins faster than cultured non-pluripotent cells (Matson et al., 2017). Retinoblastoma protein is also constitutively hyperphosphorylated in mouse and human ESCs (Conklin et al., 2012; Ter Huurne et al., 2017), which maintains high E2F transactivation to promote unperturbed dNTP synthesis (Hirschi et al., 2010; Dick and Rubin, 2013). To ensure rapid S-phase progression, mouse ESCs also license more dormant origins than non-embryonic progenitor cells (Ge et al., 2015). This increases the ability of ESCs to complete replication during a short S phase (Courtot et al., 2018). ESCs also demonstrate an increased ability to restart stalled replication forks (Ahuja et al., 2016; Zhao et al., 2018). Human induced pluripotent stem cells (iPSC) also license replication origins rapidly in their abbreviated G1 phase (Matson et al., 2017), and dormant origins are critical to maintain rapid proliferation in hematopoietic stem cell pools (Alvarez et al., 2015). Although not yet directly tested, we anticipate that epiblast cells employ similar countermeasures to expedite DNA synthesis.

Despite these efforts, human and mouse ESCs display endogenous replication stress in unperturbed cultures (Ahuja et al., 2016; Lamm et al., 2016). It is not clear why replication is stressed in pluripotent cells, however in proliferating cancer cells transcription commonly drives replication stress through collisions between RNA and DNA polymerases, or persistent RNA/DNA hybrid molecules termed R-loops (Crossley et al., 2019). Primary somatic cells mitigate transcription and R-loop interference by temporally coordinating transcription and replication during S-phase (Meryet-Figuiere et al., 2014). It is probable that peri-implantation epiblast cells facilitate rapid genome duplication by simultaneously engaging large numbers of origins. Such activity could increase the probability of replisome and transcriptome collisions and/or R-loop induced replication stress.

Under-replication due to endogenous stress is described in mESCs and human iPSCs (Ahuja et al., 2016; Vallabhaneni et al., 2018). Lengthening the G1 phase reduces replication defects in mESCs consistent with the notion that replication stress is driven by rushed cell cycles (Ahuja et al., 2016). Pluripotent cells are reported to have enhanced DNA repair capacities and it is possible this translates to highly effectively management of inefficient replication in embryos (Maynard et al., 2008; Luo et al., 2012). Alternatively, pluripotent blastocyst cells persist for a limited number of cell divisions in vivo, and it is feasible that pre-implantation embryos simply tolerate under-replication for this brief period. Tolerance of replication defects is consistent with observations that preimplantation embryonic cells are more resistant to genomic insult than peri-implantation cells. Compromising the replication stress response should confer similar DDR activation, chromosomal segregation errors, and aneuploidy in both pre- and peri-implantation cells. However, cells with supernumerary chromosomes persist in the blastocyst before elimination during peri-implantation (Bolton et al., 2016). This may explain why many genome stability factors become essential specifically during peri-implantation development. In vivo, activating p53 through deletion of its negative regulator Mdm2 leads to lethality during peri-implantation (Jones et al., 1995). This suggests that p53 signaling during peri-implantation is a conduit to remove genomically unstable cells in vivo.

Additionally, it is important to recognize that genome stability factors may possesses cryptic essential functions during early development. For example, PARP1 is DDR factor involved in multiple aspects of genome integrity (Ray Chaudhuri and Nussenzweig, 2017). However, in mESCs, Parp1 has roles preventing the trans-differentiation of extraembryonic trophoblast cells (Nozaki et al., 1999; Hemberger et al., 2003). This pluripotency-specific function is linked to the DNA binding ability of PARP1 which confers an epigenetic-like regulation of pluripotency (Roper et al., 2014). Additionally, pluripotency-specific repair factors may provide essential functions in early development. The Filia-Floped protein complex is abundantly expressed in pluripotent but not somatic cells, and is suggested to increase the abundance of essential repair factors including BLM and promote ATR activation to encourage fork restart (Zhao et al., 2015; Zhao et al., 2018; Zheng, 2020).

Essential Roles for HDR Factors During Peri-Implantation

It is possible the canonical G1-phase c-NHEJ DSB repair pathway is dispensable during peri-implantation because cells rapidly transition through their brief G1 phase and engage alt-NHEJ or HDR in S-phase. Conversely, c- and alt-NHEJ remain active in HDR-deficient embryos, and in principle EJ functions could provide redundant DSB repair activity. An explanation why c- or alt-NHEJ cannot rescue HDR during peri-implantation may stem from the diversity of substrates repaired by HDR. While two-ended DSBs are readily repaired by EJ, collapsed replication forks present as one-ended DNA breaks which c- or alt-NHEJ cannot process (Feng and Jasin, 2017; Scully et al., 2019). One-ended breaks, however, can be repaired through a specialized HDR mechanism termed break-induced replication (BIR). During BIR, the exposed DNA end is resected, and following strand-invasion to form a displacement loop on the sister chromatid, DNA is polymerized from the invaded strand in a conservative manner (Kramara et al., 2018). While BIR is commonly studied in yeast, the analogous mechanism in vertebrates remains poorly defined. Notwithstanding, Blm promotes BIR at chromosome ends in human cancer cells that maintain telomere length through the alternative lengthening of telomeres mechanism suggesting that Blm may promote BIR elsewhere in the genome following replication stress (Sobinoff et al., 2017). Additionally, Pold3 is also implicated in vertebrate BIR (Costantino et al., 2014). Conversely, the non-essential gene Rad52 also functions in vertebrate BIR casting doubt on the requirement for BIR in early development and indicating the need for future studies (Sotiriou et al., 2016).

Multiple HDR factors essential for peri-implantation also play central roles in replication stress management. This includes HDR factors that regress, stabilize, or resect stalled replication forks including Brca1/2, Bard1, Rad51 and Rad51C, Ctip, Ptip, Dna2, and genes encoding the MRN complex. Interestingly, the helicases and translocases that promote fork regression, including Smarcal1, are not essential for peri-implantation (Baradaran-Heravi et al., 2012). This may reflect redundancy in the mechanisms that drive formation of 4-strand structures at stalled replication forks (Quinet et al., 2017). Given the essentiality of the replication stress response for epiblast development, it stands to reason that replication fork remodeling and protective functions encoded by HDR factors play a role in the viability of peri-implantation embryos. Failure to facilitate these activities would confer genome instability, chromosome segregation errors, and molecular outcomes consistent with unrepaired replication stress. As described above, this would activate p53 surveillance systems during peri-implantation. In the future it will be interesting to determine which specific HDR functions are essential for embryogenesis.

Conclusion and Future Directions

While most DDR and repair factors are non-essential, this does not exclude non-essential genome stability pathways from playing an important role in healthy development. Deletion of non-essential DDR and repair genes commonly results in the birth of live pups exhibiting a wide array of deleterious phenotypes (Supplementary Table S1). Additionally, cancer predisposition and a reduced lifespan are common in mice lacking non-essential genome stability factors (Supplementary Table S1). The difference between essential and non-essential genome stability genes is likely derived from the necessity of the targeted repair pathway to resolve lethal genome instability that arises during a specific window of development.

The critical genome stability pathways required for cell survival are determined by the type of genomic lesions the cell encounters and when in the cell cycle those lesions arise. Early embryonic development is largely protected from exogenous influence. Preimplantation embryos are wholly contained, and maternal blood supply begins at E9.5 (Behringer et al., 2014). The critical early stages of development likely benefit from sequestration from external threats to genome stability. We suggest the imminent threat to genome stability in early development stems from the need to mitigate endogenous replication stress within the epiblast to sustain rapid cell cycles. If left unresolved, replication stress drives genome instability, chromosome segregation errors, growth arrest and/or cell death. Dwindling cell numbers of epiblast cells that fail to effectively replicate their genome will progressively lead to embryo compromise. This premise is supported by the timing of embryo failure associated with deletion of essential DDR and repair genes. Consistent with systemic proliferative failure, deletion of factors required for basal DNA replication, or up-stream signaling in the replication stress response, typically induce an early embryonic demise (E5.0 or before). Whereas deleting HDR factors induces death at a subsequent time (E5.5 or later), potentially as the additive outcome of progressive genome instability.

Another caveat of reports reviewed here is that many were pioneering studies that utilized the newly developed technology of gene targeting in mice. In the intervening decades, our understanding of early development and experimental capability has blossomed. Development of new stem cell culture technologies now enables mechanistic study of peri-implantation development within three-dimensional gastrula structures in vitro. Co-culture of ICM derived ESCs, trophectoderm derived trophoblast stem cells, and extraembryonic endoderm stem cells results in the spontaneous self-assembly of a structure remarkably like the gastrulating embryo. These structures, termed “ETX embryos” will enable directed gene deletion within specific embryonic cell types (Sozen et al., 2018). Coupled with precise mechanistic investigations, ETX embryo models will reveal new insights on the mechanisms of cell compromise during embryogenesis. It will be exciting to learn in the coming years why a limited number of DDR and repair pathways are essential for development, and the underlying reasons for their importance within the peri-implantation embryo.

Statements

Data availability statement

MGI-GO designations discussed in this review can be found at the following. DNA damage checkpoint: http://www.informatics.jax.org/go/term/GO:0000077; nucleotide excision repair: http://www.informatics.jax.org/go/term/GO:0006289; mismatch re- pair: http://www.informatics.jax.org/go/term/GO:0006298; base excision repair: http://www.informatics.jax.org/go/term/GO:0006284; DSB repair via homologous recombination: http://www.informatics.jax.org/go/term/GO:0000724; DSB repair via non-homologous end joining: http://www.informatics.jax.org/go/term/GO:0006303.

Author contributions

GK and AC conceived of the review manuscript. GK compiled the information presented in Tables 1, 2 and Supplementary Table S1 from the MGI-GO database as indicated. GK made the figures. GK and AC composed the manuscript.

Funding

The Cesare laboratory is supported by grants from the Australian National Health and Medical Research Council (1162886 and 1185870) and The Neil and Norma Hill Foundation.

Acknowledgments

The authors thank members of the Cesare and Tam laboratories at the Children’s Medical Research Institute for their helpful discussion.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fcell.2020.00416/full#supplementary-material

References

  • 1

    AcloqueH.AdamsM. S.FishwickK.Bronner-FraserM.NietoM. A. (2009). Epithelial-mesenchymal transitions: the importance of changing cell state in development and disease.J. Clin. Invest.11914381449. 10.1172/JCI38019

  • 2

    Affar ElB.GayF.ShiY.LiuH.HuarteM.WuS.et al (2006). Essential dosage-dependent functions of the transcription factor yin yang 1 in late embryonic development and cell cycle progression.Mol. Cell. Biol.2635653581. 10.1128/MCB.26.9.3565-3581.2006

  • 3

    AfzalS.HaoZ.ItsumiM.AbouelkheerY.BrennerD.GaoY.et al (2015). Autophagy-independent functions of UVRAG are essential for peripheral naive T-cell homeostasis.Proc. Natl. Acad. Sci. U.S.A.11211191124. 10.1073/pnas.1423588112

  • 4

    AhujaA. K.JodkowskaK.TeloniF.BizardA. H.ZellwegerR.HerradorR.et al (2016). A short G1 phase imposes constitutive replication stress and fork remodelling in mouse embryonic stem cells.Nat. Commun.7:10660. 10.1038/ncomms10660

  • 5

    AirdK. M.ZhangR. (2015). Nucleotide metabolism, oncogene-induced senescence and cancer.Cancer Lett.356204210. 10.1016/j.canlet.2014.01.017

  • 6

    Ait SaadaA.LambertS. A. E.CarrA. M. (2018). Preserving replication fork integrity and competence via the homologous recombination pathway.DNA Repair71135147. 10.1016/j.dnarep.2018.08.017

  • 7

    AkdemirK. C.JainA. K.AlltonK.AronowB.XuX.CooneyA. J.et al (2014). Genome-wide profiling reveals stimulus-specific functions of p53 during differentiation and DNA damage of human embryonic stem cells.Nucleic Acids Res.42205223. 10.1093/nar/gkt866

  • 8

    AliA. A. E.TiminszkyG.Arribas-BosacomaR.KozlowskiM.HassaP. O.HasslerM.et al (2012). The zinc-finger domains of PARP1 cooperate to recognize DNA strand breaks.Nat. Struct. Mol. Biol.19685692. 10.1038/nsmb.2335

  • 9

    AlvarezS.DiazM.FlachJ.Rodriguez-AcebesS.Lopez-ContrerasA. J.MartinezD.et al (2015). Replication stress caused by low MCM expression limits fetal erythropoiesis and hematopoietic stem cell functionality.Nat. Commun.6:8548. 10.1038/ncomms9548

  • 10

    AndressooJ. O.WeedaG.De WitJ.MitchellJ. R.BeemsR. B.Van SteegH.et al (2009). An Xpb mouse model for combined xeroderma pigmentosum and cockayne syndrome reveals progeroid features upon further attenuation of DNA repair.Mol. Cell. Biol.2912761290. 10.1128/MCB.01229-08

  • 11

    ArtusJ.Vandormael-PourninS.FrodinM.NacerddineK.BabinetC.Cohen-TannoudjiM. (2005). Impaired mitotic progression and preimplantation lethality in mice lacking OMCG1, a new evolutionarily conserved nuclear protein.Mol. Cell. Biol.2562896302. 10.1128/MCB.25.14.6289-6302.2005

  • 12

    AudebertM.SallesB.CalsouP. (2004). Involvement of poly(ADP-ribose) polymerase-1 and XRCC1/DNA ligase III in an alternative route for DNA double-strand breaks rejoining.J. Biol. Chem.2795511755126. 10.1074/jbc.M404524200

  • 13

    BaninS.MoyalL.ShiehS.TayaY.AndersonC. W.ChessaL.et al (1998). Enhanced phosphorylation of p53 by ATM in response to DNA damage.Science28116741677. 10.1126/science.281.5383.1674

  • 14

    Baradaran-HeraviA.ChoK. S.TolhuisB.SanyalM.MorozovaO.MorimotoM.et al (2012). Penetrance of biallelic SMARCAL1 mutations is associated with environmental and genetic disturbances of gene expression.Hum. Mol. Genet.2125722587. 10.1093/hmg/dds083

  • 15

    BarefieldC.KarlsederJ. (2012). The BLM helicase contributes to telomere maintenance through processing of late-replicating intermediate structures.Nucleic Acids Res.4073587367. 10.1093/nar/gks407

  • 16

    BarlowC.HirotsuneS.PaylorR.LiyanageM.EckhausM.CollinsF.et al (1996). Atm-deficient mice: a paradigm of ataxia telangiectasia.Cell86159171. 10.1016/s0092-8674(00)80086-0

  • 17

    BassT. E.LuzwickJ. W.KavanaughG.CarrollC.DungrawalaH.GlickG. G.et al (2016). ETAA1 acts at stalled replication forks to maintain genome integrity.Nat. Cell Biol.1811851195. 10.1038/ncb3415

  • 18

    BehringerR.GertsensteinM.NagyK. V.NagyA. (2014). Manipulating the Mouse Embryo.Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press.

  • 19

    BemarkM.KhamlichiA. A.DaviesS. L.NeubergerM. S. (2000). Disruption of mouse polymerase zeta (Rev3) leads to embryonic lethality and impairs blastocyst development in vitro.Curr. Biol.1012131216. 10.1016/s0960-9822(00)00724-7

  • 20

    BermudezV. P.Lindsey-BoltzL. A.CesareA. J.ManiwaY.GriffithJ. D.HurwitzJ.et al (2003). Loading of the human 9-1-1 checkpoint complex onto DNA by the checkpoint clamp loader hRad17-replication factor C complex in vitro. Proc. Natl. Acad. Sci. U.S.A.100, 16331638. 10.1073/pnas.0437927100

  • 21

    BhatA.AndersenP. L.QinZ.XiaoW. (2013). Rev3, the catalytic subunit of Polzeta, is required for maintaining fragile site stability in human cells.Nucleic Acids Res.4123282339. 10.1093/nar/gks1442

  • 22

    BhatK. P.CortezD. (2018). RPA and RAD51: fork reversal, fork protection, and genome stability.Nat. Struct. Mol. Biol.2518. 10.1038/s41594-018-0075-z

  • 23

    BleichertF. (2019). Mechanisms of replication origin licensing: a structural perspective.Curr. Opin. Struct. Biol.59195204. 10.1016/j.sbi.2019.08.007

  • 24

    BoiteuxS.GuilletM. (2004). Abasic sites in DNA: repair and biological consequences in Saccharomyces cerevisiae.DNA Repair.3112. 10.1016/j.dnarep.2003.10.002

  • 25

    BoltonH.GrahamS. J. L.Van Der AaN.KumarP.TheunisK.Fernandez GallardoE.et al (2016). Mouse model of chromosome mosaicism reveals lineage-specific depletion of aneuploid cells and normal developmental potential.Nat. Commun.7:11165. 10.1038/ncomms11165

  • 26

    BoosD.FrigolaJ.DiffleyJ. F. (2012). Activation of the replicative DNA helicase: breaking up is hard to do.Curr. Opin. Cell Biol.24423430. 10.1016/j.ceb.2012.01.011

  • 27

    Bowman-ColinC.XiaB.BuntingS.KlijnC.DrostR.BouwmanP.et al (2013). Palb2 synergizes with Trp53 to suppress mammary tumor formation in a model of inherited breast cancer.Proc. Natl. Acad. Sci. U.S.A.11086328637. 10.1073/pnas.1305362110

  • 28

    BronsI. G.SmithersL. E.TrotterM. W.Rugg-GunnP.SunB.Chuva De Sousa LopesS. M.et al (2007). Derivation of pluripotent epiblast stem cells from mammalian embryos.Nature448191195. 10.1038/nature05950

  • 29

    BrownE. J.BaltimoreD. (2000). ATR disruption leads to chromosomal fragmentation and early embryonic lethality.Genes Dev.14397402.

  • 30

    BuisJ.WuY.DengY.LeddonJ.WestfieldG.EckersdorffM.et al (2008). Mre11 nuclease activity has essential roles in DNA repair and genomic stability distinct from ATM activation.Cell1358596. 10.1016/j.cell.2008.08.015

  • 31

    BuissonR.BoisvertJ. L.BenesC. H.ZouL. (2015). Distinct but concerted roles of ATR, DNA-PK, and Chk1 in countering replication stress during S Phase.Mol. Cell5910111024. 10.1016/j.molcel.2015.07.029

  • 32

    BuissonR.NirajJ.RodrigueA.HoC. K.KreuzerJ.FooT. K.et al (2017). Coupling of Homologous Recombination and the Checkpoint by ATR.Mol. Cell65336346. 10.1016/j.molcel.2016.12.007

  • 33

    BultC. J.BlakeJ. A.SmithC. L.KadinJ. A.RichardsonJ. E.Mouse Genome DatabaseG. (2019). Mouse Genome Database (MGD) 2019.Nucleic Acids Res.47D801D806. 10.1093/nar/gky1056

  • 34

    BurgersP. M. J.KunkelT. A. (2017). Eukaryotic DNA Replication Fork.Annu. Rev. Biochem.86417438. 10.1146/annurev-biochem-061516-044709

  • 35

    BurrellR. A.McclellandS. E.EndesfelderD.GrothP.WellerM. C.ShaikhN.et al (2013). Replication stress links structural and numerical cancer chromosomal instability.Nature494492496. 10.1038/nature11935

  • 36

    ByunT. S.PacekM.YeeM.-C.WalterJ. C.CimprichK. A. (2005). Functional uncoupling of MCM helicase and DNA polymerase activities activates the ATR-dependent checkpoint.Genes Dev.1910401052. 10.1101/gad.1301205

  • 37

    CangY.ZhangJ.NicholasS. A.BastienJ.LiB.ZhouP.et al (2006). Deletion of DDB1 in mouse brain and lens leads to p53-dependent elimination of proliferating cells.Cell127929940. 10.1016/j.cell.2006.09.045

  • 38

    CarverE. A.JiangR.LanY.OramK. F.GridleyT. (2001). The mouse snail gene encodes a key regulator of the epithelial-mesenchymal transition.Mol. Cell. Biol.2181848188. 10.1128/MCB.21.23.8184-8188.2001

  • 39

    CelesteA.PetersenS.RomanienkoP. J.Fernandez-CapetilloO.ChenH. T.SedelnikovaO. A.et al (2002). Genomic instability in mice lacking histone H2AX.Science296922927. 10.1126/science.1069398

  • 40

    CelliG. B.DenchiE. L.De LangeT. (2006). Ku70 stimulates fusion of dysfunctional telomeres yet protects chromosome ends from homologous recombination.Nat. Cell Biol.8885890. 10.1038/ncb1444

  • 41

    ChangH. H. Y.PannunzioN. R.AdachiN.LieberM. R. (2017). Non-homologous DNA end joining and alternative pathways to double-strand break repair.Nat. Rev. Mol. Cell Biol.18495506. 10.1038/nrm.2017.48

  • 42

    ChapmanJ. R.BarralP.VannierJ. B.BorelV.StegerM.Tomas-LobaA.et al (2013). RIF1 is essential for 53BP1-dependent nonhomologous end joining and suppression of DNA double-strand break resection.Mol. Cell49858871. 10.1016/j.molcel.2013.01.002

  • 43

    ChenC. H.ChuP. C.LeeL.LienH. W.LinT. L.FanC. C.et al (2012). Disruption of murine mp29/Syf2/Ntc31 gene results in embryonic lethality with aberrant checkpoint response.PLoS One7:e33538. 10.1371/journal.pone.0033538

  • 44

    ChenP.-L.LiuF.CaiS.LinX.LiA.ChenY.et al (2005). Inactivation of CtIP leads to early embryonic lethality mediated by G1 restraint and to tumorigenesis by haploid insufficiency.Mol. Cell. Biol.2535353542. 10.1128/MCB.25.9.3535-3542.2005

  • 45

    ChesterN.KuoF.KozakC.O’haraC. D.LederP. (1998). Stage-specific apoptosis, developmental delay, and embryonic lethality in mice homozygous for a targeted disruption in the murine Bloom’s syndrome gene.Genes Dev.1233823393. 10.1101/gad.12.21.3382

  • 46

    ChoE. A.PrindleM. J.DresslerG. R. (2003). BRCT domain-containing protein PTIP is essential for progression through mitosis.Mol. Cell. Biol.2316661673. 10.1128/mcb.23.5.1666-1673.2003

  • 47

    ChoiJ.-H.Lindsey-BoltzL. A.KempM.MasonA. C.WoldM. S.SancarA. (2010). Reconstitution of RPA-covered single-stranded DNA-activated ATR-Chk1 signaling.Proc. Natl. Acad. Sci. U.S.A.1071366013665. 10.1073/pnas.1007856107

  • 48

    CondicM. L. (2014). Totipotency: what it is and what it is not.Stem Cells Dev.23796812. 10.1089/scd.2013.0364

  • 49

    ConklinJ. F.BakerJ.SageJ. (2012). The RB family is required for the self-renewal and survival of human embryonic stem cells.Nat. Commun.3:1244. 10.1038/ncomms2254

  • 50

    CortezD. (2019). Replication-Coupled DNA Repair.Mol. Cell74866876. 10.1016/j.molcel.2019.04.027

  • 51

    CortezD.GuntukuS.QinJ.ElledgeS. J. (2001). ATR and ATRIP: partners in checkpoint signaling.Science29417131716. 10.1126/science.1065521

  • 52

    CostantinoL.SotiriouS. K.RantalaJ. K.MaginS.MladenovE.HelledayT.et al (2014). Break-induced replication repair of damaged forks induces genomic duplications in human cells.Science3438891. 10.1126/science.1243211

  • 53

    CouchF. B.BansbachC. E.DriscollR.LuzwickJ. W.GlickG. G.BetousR.et al (2013). ATR phosphorylates SMARCAL1 to prevent replication fork collapse.Genes Dev.2716101623. 10.1101/gad.214080.113

  • 54

    CourtotL.HoffmannJ. S.BergoglioV. (2018). The protective role of dormant origins in response to replicative stress.Int. J. Mol. Sci.19:E3569. 10.3390/ijms19113569

  • 55

    CrossleyM. P.BocekM.CimprichK. A. (2019). R-Loops as Cellular Regulators and Genomic Threats.Mol. Cell73398411. 10.1016/j.molcel.2019.01.024

  • 56

    DaviesS. L.NorthP. S.HicksonI. D. (2007). Role for BLM in replication-fork restart and suppression of origin firing after replicative stress.Nat. Struct. Mol. Biol.14677679. 10.1038/nsmb1267

  • 57

    Daza-MartinM.StarowiczK.JamshadM.TyeS.RonsonG. E.MackayH. L.et al (2019). Isomerization of BRCA1-BARD1 promotes replication fork protection.Nature571521527. 10.1038/s41586-019-1363-4

  • 58

    de BoerJ.DonkerI.De WitJ.HoeijmakersJ. H.WeedaG. (1998). Disruption of the mouse xeroderma pigmentosum group D DNA repair/basal transcription gene results in preimplantation lethality.Cancer Res.588994.

  • 59

    de KleinA.MuijtjensM.Van OsR.VerhoevenY.SmitB.CarrA. M.et al (2000). Targeted disruption of the cell-cycle checkpoint gene ATR leads to early embryonic lethality in mice.Curr. Biol.10479482. 10.1016/s0960-9822(00)00447-4

  • 60

    DelacroixS.WagnerJ. M.KobayashiM.YamamotoK.KarnitzL. M. (2007). The Rad9-Hus1-Rad1 (9-1-1) clamp activates checkpoint signaling via TopBP1.Genes Dev.2114721477. 10.1101/gad.1547007

  • 61

    DenchiE. L.de LangeT. (2007). Protection of telomeres through independent control of ATM and ATR by TRF2 and POT1.Nature44810681071. 10.1038/nature06065

  • 62

    DickF. A.RubinS. M. (2013). Molecular mechanisms underlying RB protein function.Nat. Rev. Mol. Cell Biol.14297306. 10.1038/nrm3567

  • 63

    DickinsonM. E.FlennikenA. M.JiX.TeboulL.WongM. D.WhiteJ. K.et al (2016). High-throughput discovery of novel developmental phenotypes.Nature537508514. 10.1038/nature19356

  • 64

    DingX.Ray ChaudhuriA.CallenE.PangY.BiswasK.KlarmannK. D.et al (2016). Synthetic viability by BRCA2 and PARP1/ARTD1 deficiencies.Nat. Commun.7:12425. 10.1038/ncomms12425

  • 65

    DirilM. K.RatnacaramC. K.PadmakumarV. C.DuT.WasserM.CoppolaV.et al (2012). Cyclin-dependent kinase 1 (Cdk1) is essential for cell division and suppression of DNA re-replication but not for liver regeneration.Proc. Natl. Acad. Sci. U S.A.10938263831. 10.1073/pnas.1115201109

  • 66

    DupreA.Boyer-ChatenetL.GautierJ. (2006). Two-step activation of ATM by DNA and the Mre11-Rad50-Nbs1 complex.Nat. Struct. Mol. Biol.13451457. 10.1038/nsmb1090

  • 67

    EglyJ. M. (2001). The 14th Datta Lecture. TFIIH: from transcription to clinic.FEBS Lett.498124128. 10.1016/s0014-5793(01)02458-9

  • 68

    FengW.JasinM. (2017). BRCA2 suppresses replication stress-induced mitotic and G1 abnormalities through homologous recombination.Nat. Commun.8:525. 10.1038/s41467-017-00634-0

  • 69

    FlachJ.BakkerS. T.MohrinM.ConroyP. C.PietrasE. M.ReynaudD.et al (2014). Replication stress is a potent driver of functional decline in ageing haematopoietic stem cells.Nature512198202. 10.1038/nature13619

  • 70

    FortscheggerK.WagnerB.VoglauerR.KatingerH.SibiliaM.GrillariJ. (2007). Early embryonic lethality of mice lacking the essential protein SNEV.Mol. Cell. Biol.2731233130. 10.1128/MCB.01188-06

  • 71

    FosterC. T.DoveyO. M.LezinaL.LuoJ. L.GantT. W.BarlevN.et al (2010). Lysine-specific demethylase 1 regulates the embryonic transcriptome and CoREST stability.Mol. Cell. Biol.3048514863. 10.1128/MCB.00521-10

  • 72

    FotiR.GnanS.CornacchiaD.DileepV.Bulut-KarsliogluA.DiehlS.et al (2016). Nuclear Architecture Organized by Rif1 Underpins the Replication-Timing Program.Mol. Cell61260273. 10.1016/j.molcel.2015.12.001

  • 73

    FrankK. M.SekiguchiJ. M.SeidlK. J.SwatW.RathbunG. A.ChengH. L.et al (1998). Late embryonic lethality and impaired V(D)J recombination in mice lacking DNA ligase IV.Nature396173177. 10.1038/24172

  • 74

    FukushimaT.MatsuzawaS.KressC. L.BrueyJ. M.KrajewskaM.LefebvreS.et al (2007). Ubiquitin-conjugating enzyme Ubc13 is a critical component of TNF receptor-associated factor (TRAF)-mediated inflammatory responses.Proc. Natl. Acad. Sci. U.S.A.10463716376. 10.1073/pnas.0700548104

  • 75

    GanuzaM.Sáiz-LaderaC.CañameroM.GómezG.SchneiderR.BlascoM. A.et al (2012). Genetic inactivation of Cdk7 leads to cell cycle arrest and induces premature aging due to adult stem cell exhaustion.EMBO J.3124982510. 10.1038/emboj.2012.94

  • 76

    GarzonJ.RodriguezR.KongZ.ChabesA.Rodriguez-AcebesS.MendezJ.et al (2017). Shortage of dNTPs underlies altered replication dynamics and DNA breakage in the absence of the APC/C cofactor Cdh1.Oncogene3658085818. 10.1038/onc.2017.186

  • 77

    GavetO.PinesJ. (2010). Progressive activation of CyclinB1-Cdk1 coordinates entry to mitosis.Dev. Cell18533543. 10.1016/j.devcel.2010.02.013

  • 78

    GeX. Q.HanJ.ChengE. C.YamaguchiS.ShimaN.ThomasJ. L.et al (2015). Embryonic Stem Cells License a High Level of Dormant Origins to Protect the Genome against Replication Stress.Stem Cell Rep.5185194. 10.1016/j.stemcr.2015.06.002

  • 79

    GeorgakilasA. G.MartinO. A.BonnerW. M. (2017). p21: a two-faced genome guardian.Trends Mol. Med.23310319. 10.1016/j.molmed.2017.02.001

  • 80

    GhezraouiH.PiganeauM.RenoufB.RenaudJ.-B.SallmyrA.RuisB.et al (2014). Chromosomal translocations in human cells are generated by canonical nonhomologous end-joining.Mol. Cell55829842. 10.1016/j.molcel.2014.08.002

  • 81

    GotterA. L.ManganaroT.WeaverD. R.KolakowskiLFJrPossidenteB.SriramS.et al (2000). A time-less function for mouse timeless.Nat. Neurosci.3755756.

  • 82

    GottliebT. M.JacksonS. P. (1993). The DNA-dependent protein kinase: requirement for DNA ends and association with Ku antigen.Cell72131142. 10.1016/0092-8674(93)90057-w

  • 83

    GuY.SeidlK. J.RathbunG. A.ZhuC.ManisJ. P.Van Der StoepN.et al (1997). Growth retardation and leaky SCID phenotype of Ku70-deficient mice.Immunity7653665. 10.1016/s1074-7613(00)80386-6

  • 84

    HaahrP.HoffmannS.TollenaereM. A.HoT.ToledoL. I.MannM.et al (2016). Activation of the ATR kinase by the RPA-binding protein ETAA1.Nat. Cell Biol.1811961207. 10.1038/ncb3422

  • 85

    HakemR.De La PompaJ. L.SirardC.MoR.WooM.HakemA.et al (1996). The tumor suppressor gene Brca1 is required for embryonic cellular proliferation in the mouse.Cell8510091023. 10.1016/s0092-8674(00)81302-1

  • 86

    HamataniT.CarterM. G.SharovA. A.KoM. S. H. (2004). Dynamics of global gene expression changes during mouse preimplantation development.Dev. Cell6117131. 10.1016/s1534-5807(03)00373-3

  • 87

    HarveyS. L.CharletA.HaasW.GygiS. P.KelloggD. R. (2005). Cdk1-dependent regulation of the mitotic inhibitor Wee1.Cell122407420. 10.1016/j.cell.2005.05.029

  • 88

    HauptY.MayaR.KazazA.OrenM. (1997). Mdm2 promotes the rapid degradation of p53.Nature387296299. 10.1038/387296a0

  • 89

    HembergerM.NozakiT.WinterhagerE.YamamotoH.NakagamaH.KamadaN.et al (2003). Parp1-deficiency induces differentiation of ES cells into trophoblast derivatives.Dev. Biol.257371381. 10.1016/s0012-1606(03)00097-6

  • 90

    HeyerB. S.MacauleyA.BehrendtsenO.WerbZ. (2000). Hypersensitivity to DNA damage leads to increased apoptosis during early mouse development.Genes Dev.1420722084.

  • 91

    HillerB.AchleitnerM.GlageS.NaumannR.BehrendtR.RoersA. (2012). Mammalian RNase H2 removes ribonucleotides from DNA to maintain genome integrity.J. Exp. Med.20914191426. 10.1084/jem.20120876

  • 92

    HirschiA.CecchiniM.SteinhardtR. C.SchamberM. R.DickF. A.RubinS. M. (2010). An overlapping kinase and phosphatase docking site regulates activity of the retinoblastoma protein.Nat. Struct. Mol. Biol.1710511057. 10.1038/nsmb.1868

  • 93

    HnizdaA.BlundellT. L. (2019). Multicomponent assemblies in DNA-double-strand break repair by NHEJ.Curr. Opin. Struct. Biol.55154160. 10.1016/j.sbi.2019.03.026

  • 94

    HockemeyerD.DanielsJ.-P.TakaiH.De LangeT. (2006). Recent expansion of the telomeric complex in rodents: Two distinct POT1 proteins protect mouse telomeres.Cell1266377. 10.1016/j.cell.2006.04.044

  • 95

    HockemeyerD.SfeirA. J.ShayJ. W.WrightW. E.De LangeT. (2005). POT1 protects telomeres from a transient DNA damage response and determines how human chromosomes end.EMBO J.2426672678. 10.1038/sj.emboj.7600733

  • 96

    HokiY.ArakiR.FujimoriA.OhhataT.KosekiH.FukumuraR.et al (2003). Growth retardation and skin abnormalities of the Recql4-deficient mouse.Hum. Mol. Genet.1222932299. 10.1093/hmg/ddg254

  • 97

    HoriiT.YamamotoM.MoritaS.KimuraM.NagaoY.HatadaI. (2015). p53 suppresses tetraploid development in mice.Sci. Rep.5:8907. 10.1038/srep08907

  • 98

    HumięckaM.SzpilaM.KłośP.MaleszewskiM.SzczepańskaK. (2017). Mouse blastomeres acquire ability to divide asymmetrically before compaction.PLoS One12:e0175032. 10.1371/journal.pone.0175032

  • 99

    HustedtN.DurocherD. (2016). The control of DNA repair by the cell cycle.Nat. Cell Biol.1919. 10.1038/ncb3452

  • 100

    JacksonS. P.DurocherD. (2013). Regulation of DNA damage responses by ubiquitin and SUMO.Mol. Cell49795807. 10.1016/j.molcel.2013.01.017

  • 101

    JacomeA.Gutierrez-MartinezP.SchiavoniF.TenagliaE.MartinezP.Rodriguez-AcebesS.et al (2015). NSMCE2 suppresses cancer and aging in mice independently of its SUMO ligase activity.EMBO J.3426042619. 10.15252/embj.201591829

  • 102

    JainA. K.XiY.MccarthyR.AlltonK.AkdemirK. C.PatelL. R.et al (2016). LncPRESS1 is a p53-Regulated LncRNA that safeguards pluripotency by disrupting SIRT6-mediated de-acetylation of histone H3K56.Mol. Cell64967981. 10.1016/j.molcel.2016.10.039

  • 103

    JeonY.KoE.LeeK. Y.KoM. J.ParkS. Y.KangJ.et al (2011). TopBP1 deficiency causes an early embryonic lethality and induces cellular senescence in primary cells.J. Biol. Chem.28654145422. 10.1074/jbc.M110.189704

  • 104

    JonesS. N.RoeA. E.DonehowerL. A.BradleyA. (1995). Rescue of embryonic lethality in Mdm2-deficient mice by absence of p53.Nature378206208. 10.1038/378206a0

  • 105

    JukamD.ShariatiS. A. M.SkotheimJ. M. (2017). Zygotic genome activation in vertebrates.Dev. Cell42316332.

  • 106

    KaferG. R.LiX.HoriiT.SuetakeI.TajimaS.HatadaI.et al (2016). 5-Hydroxymethylcytosine Marks Sites of DNA Damage and Promotes Genome Stability.Cell Rep.1412831292. 10.1016/j.celrep.2016.01.035

  • 107

    KempM. G.AkanZ.YilmazS.GrilloM.Smith-RoeS. L.KangT. H.et al (2010). Tipin-replication protein A interaction mediates Chk1 phosphorylation by ATR in response to genotoxic stress.J. Biol. Chem.2851656216571. 10.1074/jbc.M110.110304

  • 108

    KentL. N.LeoneG. (2019). The broken cycle: E2F dysfunction in cancer.Nat. Rev. Cancer19326338. 10.1038/s41568-019-0143-7

  • 109

    KentT.ChandramoulyG.McdevittS. M.OzdemirA. Y.PomerantzR. T. (2015). Mechanism of microhomology-mediated end-joining promoted by human DNA polymerase θ.Nat. Struct. Mol. Biol.22230237. 10.1038/nsmb.2961

  • 110

    KimJ. M.NakaoK.NakamuraK.SaitoI.KatsukiM.AraiK.-I.et al (2002). Inactivation of Cdc7 kinase in mouse ES cells results in S-phase arrest and p53-dependent cell death.EMBO J.2121682179. 10.1093/emboj/21.9.2168

  • 111

    KonN.KobayashiY.LiM.BrooksC. L.LudwigT.GuW. (2010). Inactivation of HAUSP in vivo modulates p53 function.Oncogene2912701279. 10.1038/onc.2009.427

  • 112

    KramaraJ.OsiaB.MalkovaA. (2018). Break-induced replication: the Where. The Why, and The How. Trends Genet.34518531. 10.1016/j.tig.2018.04.002

  • 113

    KumagaiA.LeeJ.YooH. Y.DunphyW. G. (2006). TopBP1 activates the ATR-ATRIP complex.Cell124943955.

  • 114

    KurimasaA.OuyangH.DongL. J.WangS.LiX.Cordon-CardoC.et al (1999). Catalytic subunit of DNA-dependent protein kinase: impact on lymphocyte development and tumorigenesis.Proc. Natl. Acad. Sci. U.S.A.9614031408. 10.1073/pnas.96.4.1403

  • 115

    KuznetsovS. G.HainesD. C.MartinB. K.SharanS. K. (2009). Loss of Rad51c leads to embryonic lethality and modulation of Trp53-dependent tumorigenesis in mice.Cancer Res.69863872. 10.1158/0008-5472.CAN-08-3057

  • 116

    LammN.Ben-DavidU.Golan-LevT.StorchovaZ.BenvenistyN.KeremB. (2016). Genomic instability in human pluripotent stem cells arises from replicative stress and chromosome condensation defects.Cell Stem Cell18253261. 10.1016/j.stem.2015.11.003

  • 117

    LarsenE.GranC.SaetherB. E.SeebergE.KlunglandA. (2003). Proliferation failure and gamma radiation sensitivity of Fen1 null mutant mice at the blastocyst stage.Mol. Cell. Biol.2353465353. 10.1128/mcb.23.15.5346-5353.2003

  • 118

    LaurentA.BlasiF. (2015). Differential DNA damage signalling and apoptotic threshold correlate with mouse epiblast-specific hypersensitivity to radiation.Development14236753685. 10.1242/dev.125708

  • 119

    LeconaE.Rodriguez-AcebesS.SpecksJ.Lopez-ContrerasA. J.RuppenI.MurgaM.et al (2016). USP7 is a SUMO deubiquitinase essential for DNA replication.Nat. Struct. Mol. Biol.23270277. 10.1038/nsmb.3185

  • 120

    LeeJ. H.PaullT. T. (2005). ATM activation by DNA double-strand breaks through the Mre11-Rad50-Nbs1 complex.Science308551554. 10.1126/science.1108297

  • 121

    LeeS.KimJ. Y.KimY. J.SeokK. O.KimJ. H.ChangY. J.et al (2012). Nucleolar protein GLTSCR2 stabilizes p53 in response to ribosomal stresses.Cell Death Differ.1916131622. 10.1038/cdd.2012.40

  • 122

    LemaçonD.JacksonJ.QuinetA.BricknerJ. R.LiS.YazinskiS.et al (2017). MRE11 and EXO1 nucleases degrade reversed forks and elicit MUS81-dependent fork rescue in BRCA2-deficient cells. Nat. Commun.8:860. 10.1038/s41467-017-01180-5

  • 123

    LiA.BlowJ. J. (2005). Cdt1 downregulation by proteolysis and geminin inhibition prevents DNA re-replication in Xenopus.EMBO J.24395404. 10.1038/sj.emboj.7600520

  • 124

    LiB.RuizJ. C.ChunK. T. (2002). CUL-4A is critical for early embryonic development.Mol. Cell. Biol.2249975005. 10.1128/mcb.22.14.4997-5005.2002

  • 125

    LiG.AltF. W.ChengH. L.BrushJ. W.GoffP. H.MurphyM. M.et al (2008). Lymphocyte-specific compensation for XLF/cernunnos end-joining functions in V(D)J recombination.Mol. Cell31631640. 10.1016/j.molcel.2008.07.017

  • 126

    LiM.HeY.DuboisW.WuX.ShiJ.HuangJ. (2012). Distinct regulatory mechanisms and functions for p53-activated and p53-repressed DNA damage response genes in embryonic stem cells.Mol. Cell463042. 10.1016/j.molcel.2012.01.020

  • 127

    LimD. S.HastyP. (1996). A mutation in mouse rad51 results in an early embryonic lethal that is suppressed by a mutation in p53.Mol. Cell. Biol.1671337143. 10.1128/mcb.16.12.7133

  • 128

    LimasJ. C.CookJ. G. (2019). Preparation for DNA replication: the key to a successful S phase.FEBS Lett.59328532867. 10.1002/1873-3468.13619

  • 129

    LinT.ChaoC.SaitoS.MazurS. J.MurphyM. E.AppellaE.et al (2005). p53 induces differentiation of mouse embryonic stem cells by suppressing Nanog expression.Nat. Cell Biol.7165171. 10.1038/ncb1211

  • 130

    LinW.SampathiS.DaiH.LiuC.ZhouM.HuJ.et al (2013). Mammalian DNA2 helicase/nuclease cleaves G-quadruplex DNA and is required for telomere integrity.EMBO J.3214251439. 10.1038/emboj.2013.88

  • 131

    LiuC.VyasA.KassabM. A.SinghA. K.YuX. (2017). The role of poly ADP-ribosylation in the first wave of DNA damage response.Nucleic Acids Res.4581298141. 10.1093/nar/gkx565

  • 132

    LiuC.-L.YuI. S.PanH.-W.LinS.-W.HsuH.-C. (2007). L2dtl is essential for cell survival and nuclear division in early mouse embryonic development.J. Biol. Chem.28211091118. 10.1074/jbc.M606535200

  • 133

    LiuD.KeijzersG.RasmussenL. J. (2017). DNA mismatch repair and its many roles in eukaryotic cells.Mutat. Res.773174187. 10.1016/j.mrrev.2017.07.001

  • 134

    LiuQ.GuntukuS.CuiX. S.MatsuokaS.CortezD.TamaiK.et al (2000). Chk1 is an essential kinase that is regulated by Atr and required for the G(2)/M DNA damage checkpoint.Genes Dev.1414481459.

  • 135

    LouJ.ScipioniL.WrightB. K.BartolecT. K.ZhangJ.MasamsettiV. P.et al (2019). Phasor histone FLIM-FRET microscopy quantifies spatiotemporal rearrangement of chromatin architecture during the DNA damage response.Proc. Natl. Acad. Sci. U.S.A.11673237332. 10.1073/pnas.1814965116

  • 136

    LouZ.Minter-DykhouseK.FrancoS.GostissaM.RiveraM. A.CelesteA.et al (2006). MDC1 maintains genomic stability by participating in the amplification of ATM-dependent DNA damage signals.Mol. Cell21187200. 10.1016/j.molcel.2005.11.025

  • 137

    LuL. Y.WoodJ. L.Minter-DykhouseK.YeL.SaundersT. L.YuX.et al (2008). Polo-like kinase 1 is essential for early embryonic development and tumor suppression.Mol. Cell. Biol.2868706876. 10.1128/MCB.00392-08

  • 138

    LudwigT.ChapmanD. L.PapaioannouV. E.EfstratiadisA. (1997). Targeted mutations of breast cancer susceptibility gene homologs in mice: lethal phenotypes of Brca1, Brca2, Brca1/Brca2, Brca1/p53, and Brca2/p53 nullizygous embryos.Genes Dev.1112261241. 10.1101/gad.11.10.1226

  • 139

    LukasC.SavicV.Bekker-JensenS.DoilC.NeumannB.PedersenR. S.et al (2011). 53BP1 nuclear bodies form around DNA lesions generated by mitotic transmission of chromosomes under replication stress.Nat. Cell Biol.13243253. 10.1038/ncb2201

  • 140

    LuoG.YaoM. S.BenderC. F.MillsM.BladlA. R.BradleyA.et al (1999). Disruption of mRad50 causes embryonic stem cell lethality, abnormal embryonic development, and sensitivity to ionizing radiation.Proc. Natl. Acad. Sci. U.S.A.9673767381. 10.1073/pnas.96.13.7376

  • 141

    LuoL. Z.Gopalakrishna-PillaiS.NayS. L.ParkS. W.BatesS. E.ZengX.et al (2012). DNA repair in human pluripotent stem cells is distinct from that in non-pluripotent human cells.PLoS One7:e30541. 10.1371/journal.pone.0030541

  • 142

    LyP.ClevelandD. W. (2017). Rebuilding chromosomes after catastrophe: emerging mechanisms of chromothripsis.Trends Cell Biol.27917930. 10.1016/j.tcb.2017.08.005

  • 143

    MachweA.KaraleR.XuX.LiuY.OrrenD. K. (2011). The Werner and Bloom syndrome proteins help resolve replication blockage by converting (regressed) holliday junctions to functional replication forks.Biochemistry5067746788. 10.1021/bi2001054

  • 144

    MaciejowskiJ.LiY.BoscoN.CampbellP. J.De LangeT. (2015). Chromothripsis and Kataegis Induced by Telomere Crisis.Cell16316411654. 10.1016/j.cell.2015.11.054

  • 145

    MailandN.Gibbs-SeymourI.Bekker-JensenS. (2013). Regulation of PCNA-protein interactions for genome stability.Nat. Rev. Mol. Cell Biol.14269282. 10.1038/nrm3562

  • 146

    ManciniA.Niemann-SeydeS. C.PankowR.El BounkariO.Klebba-FarberS.KochA.et al (2010). THOC5/FMIP, an mRNA export TREX complex protein, is essential for hematopoietic primitive cell survival in vivo.BMC Biol8:1. 10.1186/1741-7007-8-1

  • 147

    MandalR.StrebhardtK. (2013). Plk1: unexpected roles in DNA replication.Cell Res.2312511253. 10.1038/cr.2013.130

  • 148

    MankouriH. W.HuttnerD.HicksonI. D. (2013). How unfinished business from S-phase affects mitosis and beyond.EMBO J.3226612671. 10.1038/emboj.2013.211

  • 149

    MaréchalA.LiJ.-M.JiX. Y.WuC.-S.YazinskiS. A.NguyenH. D.et al (2014). PRP19 transforms into a sensor of RPA-ssDNA after DNA damage and drives ATR activation via a ubiquitin-mediated circuitry.Mol. Cell53235246. 10.1016/j.molcel.2013.11.002

  • 150

    MaréchalA.ZouL. (2013). DNA damage sensing by the ATM and ATR kinases.Cold Spring Harb. Perspect. Biol.5:a012716. 10.1101/cshperspect.a012716

  • 151

    MasamsettiV. P.LowR. R. J.MakK. S.O’connorA.RiffkinC. D.LammN.et al (2019). Replication stress induces mitotic death through parallel pathways regulated by WAPL and telomere deprotection.Nat. Commun.10:4224. 10.1038/s41467-019-12255-w

  • 152

    MasudaK.OuchidaR.TakeuchiA.SaitoT.KosekiH.KawamuraK.et al (2005). DNA polymerase theta contributes to the generation of C/G mutations during somatic hypermutation of Ig genes.Proc. Natl. Acad. Sci. U.S.A.1021398613991. 10.1073/pnas.0505636102

  • 153

    Mateos-GomezP. A.GongF.NairN.MillerK. M.Lazzerini-DenchiE.SfeirA. (2015). Mammalian polymerase θ promotes alternative NHEJ and suppresses recombination.Nature518254257. 10.1038/nature14157

  • 154

    Mateos-GomezP. A.KentT.DengS. K.McdevittS.KashkinaE.HoangT. M.et al (2017). The helicase domain of Polθ counteracts RPA to promote alt-NHEJ.Nat. Struct. Mol. Biol.2411161123. 10.1038/nsmb.3494

  • 155

    MatsonJ. P.DumitruR.CoryellP.BaxleyR. M.ChenW.TwaroskiK.et al (2017). Rapid DNA replication origin licensing protects stem cell pluripotency.eLife6:e30473.

  • 156

    MaynardS.SwistowskaA. M.LeeJ. W.LiuY.LiuS. T.Da CruzA. B.et al (2008). Human embryonic stem cells have enhanced repair of multiple forms of DNA damage.Stem Cells2622662274. 10.1634/stemcells.2007-1041

  • 157

    McCarthyE. E.CelebiJ. T.BaerR.LudwigT. (2003). Loss of Bard1, the heterodimeric partner of the Brca1 tumor suppressor, results in early embryonic lethality and chromosomal instability.Mol. Cell. Biol.2350565063. 10.1128/mcb.23.14.5056-5063.2003

  • 158

    MelloS. S.AttardiL. D. (2018). Deciphering p53 signaling in tumor suppression.Curr. Opin. Cell Biol.516572. 10.1016/j.ceb.2017.11.005

  • 159

    Meryet-FiguiereM.Alaei-MahabadiB.AliM. M.MitraS.SubhashS.PandeyG. K.et al (2014). Temporal separation of replication and transcription during S-phase progression.Cell Cycle1332413248. 10.4161/15384101.2014.953876

  • 160

    MijicS.ZellwegerR.ChappidiN.BertiM.JacobsK.MutrejaK.et al (2017). Replication fork reversal triggers fork degradation in BRCA2-defective cells. Nat. Commun.8:859. 10.1038/s41467-017-01164-5

  • 161

    MillerT. C. R.LockeJ.GreiweJ. F.DiffleyJ. F. X.CostaA. (2019). Mechanism of head-to-head MCM double-hexamer formation revealed by cryo-EM.Nature575704710. 10.1038/s41586-019-1768-0

  • 162

    MinJ.-N.TianY.XiaoY.WuL.LiL.ChangS. (2013). The mINO80 chromatin remodeling complex is required for efficient telomere replication and maintenance of genome stability.Cell Res.2313961413. 10.1038/cr.2013.113

  • 163

    MinocherhomjiS.YingS.BjerregaardV. A.BursomannoS.AleliunaiteA.WuW.et al (2015). Replication stress activates DNA repair synthesis in mitosis.Nature528286290. 10.1038/nature16139

  • 164

    MohammedH.Hernando-HerraezI.SavinoA.ScialdoneA.MacaulayI.MulasC.et al (2017). Single-cell landscape of transcriptional heterogeneity and cell fate decisions during mouse early gastrulation.Cell Rep.2012151228. 10.1016/j.celrep.2017.07.009

  • 165

    MohriT.UenoM.NagahamaY.GongZ.-Y.AsanoM.OshimaH.et al (2013). Requirement of SLD5 for early embryogenesis.PLoS One8:e78961. 10.1371/journal.pone.0078961

  • 166

    MorrisS. A.TeoR. T.LiH.RobsonP.GloverD. M.Zernicka-GoetzM. (2010). Origin and formation of the first two distinct cell types of the inner cell mass in the mouse embryo.Proc. Natl. Acad. Sci. U.S.A.10763646369. 10.1073/pnas.0915063107

  • 167

    MurgaM.BuntingS.MontañaM. F.SoriaR.MuleroF.CañameroM.et al (2009). A mouse model of ATR-Seckel shows embryonic replicative stress and accelerated aging.Nat. Genet.41891898. 10.1038/ng.420

  • 168

    MurrayS. A.MorganJ. L.KaneC.SharmaY.HeffnerC. S.LakeJ.et al (2010). Mouse gestation length is genetically determined.PLoS One5:e12418. 10.1371/journal.pone.0012418

  • 169

    MyersK.GagouM. E.Zuazua-VillarP.RodriguezR.MeuthM. (2009). ATR and Chk1 suppress a caspase-3-dependent apoptotic response following DNA replication stress.PLoS Genet.5:e1000324. 10.1371/journal.pgen.1000324

  • 170

    Navadgi-PatilV. M.BurgersP. M. (2009). A tale of two tails: activation of DNA damage checkpoint kinase Mec1/ATR by the 9-1-1 clamp and by Dpb11/TopBP1.DNA Repair89961003. 10.1016/j.dnarep.2009.03.011

  • 171

    NeelsenK. J.LopesM. (2015). Replication fork reversal in eukaryotes: from dead end to dynamic response.Nat. Rev. Mol. Cell Biol.16207220. 10.1038/nrm3935

  • 172

    NiggE. A. (2001). Mitotic kinases as regulators of cell division and its checkpoints.Nat. Rev. Mol. Cell Biol.22132. 10.1038/35048096

  • 173

    NishitaniH.TaravirasS.LygerouZ.NishimotoT. (2001). The human licensing factor for DNA replication Cdt1 accumulates in G1 and is destabilized after initiation of S-phase.J. Biol. Chem.2764490544911. 10.1074/jbc.M105406200

  • 174

    NozakiT.MasutaniM.WatanabeM.OchiyaT.HasegawaF.NakagamaH.et al (1999). Syncytiotrophoblastic giant cells in teratocarcinoma-like tumors derived from Parp-disrupted mouse embryonic stem cells.Proc. Natl. Acad. Sci. U.S.A.961334513350. 10.1073/pnas.96.23.13345

  • 175

    NussenzweigA.ChenC.Da Costa SoaresV.SanchezM.SokolK.NussenzweigM. C.et al (1996). Requirement for Ku80 in growth and immunoglobulin V(D)J recombination.Nature382551555. 10.1038/382551a0

  • 176

    OchiT.BlackfordA. N.CoatesJ.JhujhS.MehmoodS.TamuraN.et al (2015). DNA repair. PAXX, a paralog of XRCC4 and XLF, interacts with Ku to promote DNA double-strand break repair.Science347185188. 10.1126/science.1261971

  • 177

    OchsF.KaremoreG.MironE.BrownJ.SedlackovaH.RaskM. B.et al (2019). Stabilization of chromatin topology safeguards genome integrity.Nature574571574. 10.1038/s41586-019-1659-4

  • 178

    O’ConnellM. J.RaleighJ. M.VerkadeH. M.NurseP. (1997). Chk1 is a wee1 kinase in the G2 DNA damage checkpoint inhibiting cdc2 by Y15 phosphorylation.EMBO J.16545554. 10.1093/emboj/16.3.545

  • 179

    OrthweinA.Fradet-TurcotteA.NoordermeerS. M.CannyM. D.BrunC. M.StreckerJ.et al (2014). Mitosis inhibits DNA double-strand break repair to guard against telomere fusions.Science344189193. 10.1126/science.1248024

  • 180

    OuyangH.NussenzweigA.KurimasaA.SoaresV. C.LiX.Cordon-CardoC.et al (1997). Ku70 is required for DNA repair but not for T cell antigen receptor gene recombination in vivo.J. Exp. Med.186921929. 10.1084/jem.186.6.921

  • 181

    PaimL. M. G.FitzHarrisG. (2019). Tetraploidy causes chromosomal instability in acentriolar mouse embryos.Nat. Commun.10:4834. 10.1038/s41467-019-12772-8

  • 182

    ParkE.KimJ. M.PrimackB.WeinstockD. M.MoreauL. A.ParmarK.et al (2013). Inactivation of Uaf1 causes defective homologous recombination and early embryonic lethality in mice.Mol. Cell. Biol.3343604370. 10.1128/MCB.00870-13

  • 183

    PilzeckerB.BuoninfanteO. A.Van Den BerkP.LanciniC.SongJ. Y.CitterioE.et al (2017). DNA damage tolerance in hematopoietic stem and progenitor cells in mice.Proc. Natl. Acad. Sci. U.S.A.114E6875E6883. 10.1073/pnas.1706508114

  • 184

    PintardL.ArchambaultV. (2018). A unified view of spatio-temporal control of mitotic entry: Polo kinase as the key.Open Biol.8:180114. 10.1098/rsob.180114

  • 185

    PizziS.SerticS.OrcesiS.CeredaC.BianchiM.JacksonA. P.et al (2015). Reduction of hRNase H2 activity in Aicardi-Goutieres syndrome cells leads to replication stress and genome instability.Hum. Mol. Genet.24649658. 10.1093/hmg/ddu485

  • 186

    PoliJ.GasserS. M.Papamichos-ChronakisM. (2017). The INO80 remodeller in transcription, replication and repair.Philos. Trans. R. Soc. Lond. B Biol. Sci.372:20160290. 10.1098/rstb.2016.0290

  • 187

    PollardP. J.Spencer-DeneB.ShuklaD.HowarthK.NyeE.El-BahrawyM.et al (2007). Targeted inactivation of fh1 causes proliferative renal cyst development and activation of the hypoxia pathway.Cancer Cell11311319. 10.1016/j.ccr.2007.02.005

  • 188

    PowerM. A.TamP. P. (1993). Onset of gastrulation, morphogenesis and somitogenesis in mouse embryos displaying compensatory growth.Anat. Embryol.187493504. 10.1007/BF00174425

  • 189

    PrzetockaS.PorroA.BolckH. A.WalkerC.LezajaA.TrennerA.et al (2018). CtIP-mediated fork protection synergizes with BRCA1 to suppress genomic instability upon DNA replication stress.Mol. Cell7210.1016/j.molcel.2018.09.014

  • 190

    Puebla-OsorioN.LaceyD. B.AltF. W.ZhuC. (2006). Early embryonic lethality due to targeted inactivation of DNA ligase III.Mol. Cell. Biol.2639353941. 10.1128/MCB.26.10.3935-3941.2006

  • 191

    QuinetA.LemaçonD.VindigniA. (2017). Replication fork reversal: players and guardians.Mol. Cell68830833. 10.1016/j.molcel.2017.11.022

  • 192

    RayD.TeraoY.NimbalkarD.HiraiH.OsmundsonE. C.ZouX.et al (2007). Hemizygous disruption of Cdc25A inhibits cellular transformation and mammary tumorigenesis in mice.Cancer Res.6766056611. 10.1158/0008-5472.CAN-06-4815

  • 193

    Ray ChaudhuriA.CallenE.DingX.GogolaE.DuarteA. A.LeeJ. E.et al (2016). Replication fork stability confers chemoresistance in BRCA-deficient cells.Nature535382387. 10.1038/nature18325

  • 194

    Ray ChaudhuriA.NussenzweigA. (2017). The multifaceted roles of PARP1 in DNA repair and chromatin remodelling.Nat. Rev. Mol. Cell Biol.18610621. 10.1038/nrm.2017.53

  • 195

    ReinhardtH. C.SchumacherB. (2012). The p53 network: cellular and systemic DNA damage responses in aging and cancer.Trends Genet.28128136. 10.1016/j.tig.2011.12.002

  • 196

    RoaS.AvdievichE.PeledJ. U.MaccarthyT.WerlingU.KuangF. L.et al (2008). Ubiquitylated PCNA plays a role in somatic hypermutation and class-switch recombination and is required for meiotic progression.Proc. Natl. Acad. Sci. U.S.A.1051624816253. 10.1073/pnas.0808182105

  • 197

    RogakouE. P.PilchD. R.OrrA. H.IvanovaV. S.BonnerW. M. (1998). DNA double-stranded breaks induce histone H2AX phosphorylation on serine 139.J. Biol. Chem.27358585868. 10.1074/jbc.273.10.5858

  • 198

    RoperS. J.ChrysanthouS.SennerC. E.SienerthA.GnanS.MurrayA.et al (2014). ADP-ribosyltransferases Parp1 and Parp7 safeguard pluripotency of ES cells.Nucleic Acids Res.4289148927. 10.1093/nar/gku591

  • 199

    RossiD. J.LondesboroughA.KorsisaariN.PihlakA.LehtonenE.HenkemeyerM.et al (2001). Inability to enter S phase and defective RNA polymerase II CTD phosphorylation in mice lacking Mat1.EMBO J.2028442856. 10.1093/emboj/20.11.2844

  • 200

    SaldivarJ. C.CortezD.CimprichK. A. (2017). The essential kinase ATR: ensuring faithful duplication of a challenging genome.Nat. Rev. Mol. Cell Biol.18622636. 10.1038/nrm.2017.67

  • 201

    SasakiM.KawaharaK.NishioM.MimoriK.KogoR.HamadaK.et al (2011). Regulation of the MDM2-P53 pathway and tumor growth by PICT1 via nucleolar RPL11.Nat. Med.17944951. 10.1038/nm.2392

  • 202

    SchärerO. D. (2013). Nucleotide excision repair in eukaryotes.Cold Spring Harb. Perspect. Biol.5:a012609. 10.1101/cshperspect.a012609

  • 203

    SchlacherK.ChristN.SiaudN.EgashiraA.WuH.JasinM. (2011). Double-strand break repair-independent role for BRCA2 in blocking stalled replication fork degradation by MRE11.Cell145529542. 10.1016/j.cell.2011.03.041

  • 204

    ScullyR.PandayA.ElangoR.WillisN. A. (2019). DNA double-strand break repair-pathway choice in somatic mammalian cells.Nat. Rev. Mol. Cell Biol.20698714. 10.1038/s41580-019-0152-0

  • 205

    SfeirA.SymingtonL. S. (2015). Microhomology-mediated end joining: a back-up survival mechanism or dedicated pathway?Trends Biochem. Sci.40701714. 10.1016/j.tibs.2015.08.006

  • 206

    ShakyaR.SzabolcsM.MccarthyE.OspinaE.BassoK.NandulaS.et al (2008). The basal-like mammary carcinomas induced by Brca1 or Bard1 inactivation implicate the BRCA1/BARD1 heterodimer in tumor suppression.Proc. Natl. Acad. Sci. U.S.A.10570407045. 10.1073/pnas.0711032105

  • 207

    SharanS. K.MorimatsuM.AlbrechtU.LimD. S.RegelE.DinhC.et al (1997). Embryonic lethality and radiation hypersensitivity mediated by Rad51 in mice lacking Brca2.Nature386804810. 10.1038/386804a0

  • 208

    ShimaN.MunroeR. J.SchimentiJ. C. (2004). The mouse genomic instability mutation chaos1 is an allele of Polq that exhibits genetic interaction with Atm.Mol. Cell. Biol.241038110389. 10.1128/MCB.24.23.10381-10389.2004

  • 209

    ShimadaM.DumitracheL. C.RussellH. R.MckinnonP. J. (2015). Polynucleotide kinase-phosphatase enables neurogenesis via multiple DNA repair pathways to maintain genome stability.EMBO J.3424652480. 10.15252/embj.201591363

  • 210

    ShuZ.SmithS.WangL.RiceM. C.KmiecE. B. (1999). Disruption of muREC2/RAD51L1 in mice results in early embryonic lethality which can Be partially rescued in a p53(-/-) background.Mol. Cell. Biol.1986868693. 10.1128/mcb.19.12.8686

  • 211

    ShuiJ. W.HuM. C.TanT. H. (2007). Conditional knockout mice reveal an essential role of protein phosphatase 4 in thymocyte development and pre-T-cell receptor signaling.Mol. Cell. Biol.277991. 10.1128/MCB.00799-06

  • 212

    SmithT. G.LavalS.ChenF.RockM. J.StrachanT.PetersH. (2014). Neural crest cell-specific inactivation of Nipbl or Mau2 during mouse development results in a late onset of craniofacial defects.Genesis52687694. 10.1002/dvg.22780

  • 213

    SnowM. H.TamP. P. (1979). Is compensatory growth a complicating factor in mouse teratology?Nature279555557. 10.1038/279555a0

  • 214

    SnowM. H. L. (1976). “Embryo Growth during the Immediate Postimplantation Period,” in Embryogenesis in Mammals: Ciba Foundation Symposium 40 - Embryogenesis in Mammals, edsElliottK.O’ConnorM. (Amsterdam: Elsevier), 5370.

  • 215

    SnowM. H. L. (1977). Gastrulation in the mouse: growth and regionalization of the epiblast.Development42293303. 10.1111/dgd.12568

  • 216

    SobinoffA. P.AllenJ. A.NeumannA. A.YangS. F.WalshM. E.HensonJ. D.et al (2017). BLM and SLX4 play opposing roles in recombination-dependent replication at human telomeres.EMBO J.3629072919. 10.15252/embj.201796889

  • 217

    SomyajitK.SaxenaS.BabuS.MishraA.NagarajuG. (2015). Mammalian RAD51 paralogs protect nascent DNA at stalled forks and mediate replication restart.Nucleic Acids Res.4398359855. 10.1093/nar/gkv880

  • 218

    SotiriouS. K.KamileriI.LugliN.EvangelouK.Da-ReC.HuberF.et al (2016). Mammalian RAD52 functions in break-induced replication repair of collapsed DNA replication forks.Mol. Cell6411271134. 10.1016/j.molcel.2016.10.038

  • 219

    SozenB.AmadeiG.CoxA.WangR.NaE.CzukiewskaS.et al (2018). Self-assembly of embryonic and two extra-embryonic stem cell types into gastrulating embryo-like structures.Nat. Cell Biol.20979989. 10.1038/s41556-018-0147-7

  • 220

    SpiesJ.LukasC.SomyajitK.RaskM. B.LukasJ.NeelsenK. J. (2019). 53BP1 nuclear bodies enforce replication timing at under-replicated DNA to limit heritable DNA damage.Nat. Cell Biol.21487497. 10.1038/s41556-019-0293-6

  • 221

    StewartG. S.WangB.BignellC. R.TaylorA. M.ElledgeS. J. (2003). MDC1 is a mediator of the mammalian DNA damage checkpoint.Nature421961966. 10.1038/nature01446

  • 222

    StrackerT. H.PetriniJ. H. J. (2011). The MRE11 complex: starting from the ends.Nat. Rev. Mol. Cell Biol.1290103. 10.1038/nrm3047

  • 223

    StrzalkaW.ZiemienowiczA. (2011). Proliferating cell nuclear antigen (PCNA): a key factor in DNA replication and cell cycle regulation.Ann. Bot.10711271140. 10.1093/aob/mcq243

  • 224

    SymingtonL. S. (2016). Mechanism and regulation of DNA end resection in eukaryotes.Crit. Rev. Biochem. Mol. Biol.51195212. 10.3109/10409238.2016.1172552

  • 225

    TaglialatelaA.AlvarezS.LeuzziG.SanninoV.RanjhaL.HuangJ. W.et al (2017). Restoration of replication fork stability in BRCA1- and BRCA2-deficient cells by inactivation of SNF2-family fork remodelers.Mol. Cell68414430.e8. 10.1016/j.molcel.2017.09.036

  • 226

    TakaiH.TominagaK.MotoyamaN.MinamishimaY. A.NagahamaH.TsukiyamaT.et al (2000). Aberrant cell cycle checkpoint function and early embryonic death in Chk1(-/-) mice.Genes Dev.1414391447.

  • 227

    TakeuchiA.IidaK.TsubotaT.HosokawaM.DenawaM.BrownJ. B.et al (2018). Loss of Sfpq Causes Long-Gene Transcriptopathy in the Brain.Cell Rep.2313261341. 10.1016/j.celrep.2018.03.141

  • 228

    TamP. P. (1989). Regionalisation of the mouse embryonic ectoderm: allocation of prospective ectodermal tissues during gastrulation.Development1075567.

  • 229

    TamP. P.WilliamsE. A.ChanW. Y. (1993). Gastrulation in the mouse embryo: ultrastructural and molecular aspects of germ layer morphogenesis.Microsc. Res. Tech.26301328. 10.1002/jemt.1070260405

  • 230

    TamP. P. L.NelsonJ.RossantJ. (2013). Mammalian Development.Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press.

  • 231

    TebbsR. S.FlanneryM. L.MenesesJ. J.HartmannA.TuckerJ. D.ThompsonL. H.et al (1999). Requirement for the Xrcc1 DNA base excision repair gene during early mouse development.Dev. Biol.208513529. 10.1006/dbio.1999.9232

  • 232

    Ter HuurneM.ChappellJ.DaltonS.StunnenbergH. G. (2017). Distinct cell-cycle control in two different states of mouse pluripotency.Cell Stem Cell21449455.e4. 10.1016/j.stem.2017.09.004

  • 233

    TesarP. J.ChenowethJ. G.BrookF. A.DaviesT. J.EvansE. P.MackD. L.et al (2007). New cell lines from mouse epiblast share defining features with human embryonic stem cells.Nature448196199. 10.1038/nature05972

  • 234

    ThangavelS.BertiM.LevikovaM.PintoC.GomathinayagamS.VujanovicM.et al (2015). DNA2 drives processing and restart of reversed replication forks in human cells.J. Cell Biol.208545562. 10.1083/jcb.201406100

  • 235

    TheunissenJ. W.KaplanM. I.HuntP. A.WilliamsB. R.FergusonD. O.AltF. W.et al (2003). Checkpoint failure and chromosomal instability without lymphomagenesis in Mre11(ATLD1/ATLD1) mice.Mol. Cell1215111523. 10.1016/s1097-2765(03)00455-6

  • 236

    TichyE. D.PillaiR.DengL.LiangL.TischfieldJ.SchwembergerS. J.et al (2010). Mouse embryonic stem cells, but not somatic cells, predominantly use homologous recombination to repair double-strand DNA breaks.Stem Cells Dev.1916991711. 10.1089/scd.2010.0058

  • 237

    ToledoL. I.AltmeyerM.RaskM. B.LukasC.LarsenD. H.PovlsenL. K.et al (2013). ATR prohibits replication catastrophe by preventing global exhaustion of RPA.Cell15510881103. 10.1016/j.cell.2013.10.043

  • 238

    TominagaY.LiC.WangR.-H.DengC.-X. (2006). Murine Wee1 plays a critical role in cell cycle regulation and pre-implantation stages of embryonic development.Int. J. Biol. Sci.2161170. 10.7150/ijbs.2.161

  • 239

    TomodaK.Yoneda-KatoN.FukumotoA.YamanakaS.KatoJ. Y. (2004). Multiple functions of Jab1 are required for early embryonic development and growth potential in mice.J. Biol. Chem.2794301343018. 10.1074/jbc.M406559200

  • 240

    TsuzukiT.FujiiY.SakumiK.TominagaY.NakaoK.SekiguchiM.et al (1996). Targeted disruption of the Rad51 gene leads to lethality in embryonic mice.Proc. Natl. Acad. Sci. U.S.A.9362366240. 10.1073/pnas.93.13.6236

  • 241

    UchimuraA.HidakaY.HirabayashiT.HirabayashiM.YagiT. (2009). DNA polymerase delta is required for early mammalian embryogenesis.PLoS One4:e4184. 10.1371/journal.pone.0004184

  • 242

    UzielT.LerenthalY.MoyalL.AndegekoY.MittelmanL.ShilohY. (2003). Requirement of the MRN complex for ATM activation by DNA damage.EMBO J.2256125621. 10.1093/emboj/cdg541

  • 243

    VallabhaneniH.LynchP. J.ChenG.ParkK.LiuY.GoeheR.et al (2018). High basal levels of gammaH2AX in human induced pluripotent stem cells are linked to replication-associated DNA damage and repair.Stem Cells3615011513. 10.1002/stem.2861

  • 244

    ValnegriP.HuangJ.YamadaT.YangY.MejiaL. A.ChoH. Y.et al (2017). RNF8/UBC13 ubiquitin signaling suppresses synapse formation in the mammalian brain.Nat. Commun.8:1271. 10.1038/s41467-017-01333-6

  • 245

    van HartenA. M.BuijzeM.Van Der MastR.RooimansM. A.Martens-De KempS. R.BachasC.et al (2019). Targeting the cell cycle in head and neck cancer by Chk1 inhibition: a novel concept of bimodal cell death.Oncogenesis8:38. 10.1038/s41389-019-0147-x

  • 246

    Van LyD.LowR. R. J.FrolichS.BartolecT. K.KaferG. R.PickettH. A.et al (2018). Telomere loop dynamics in chromosome end protection.Mol. Cell71510525.e6. 10.1016/j.molcel.2018.06.025

  • 247

    WachowiczP.Fernández-MirandaG.MarugánC.EscobarB.De CárcerG. (2016). Genetic depletion of Polo-like kinase 1 leads to embryonic lethality due to mitotic aberrancies.Bioessays38 (Suppl. 1), S96S106. 10.1002/bies.201670908

  • 248

    WallaceS. S. (2014). Base excision repair: a critical player in many games.DNA Repair191426. 10.1016/j.dnarep.2014.03.030

  • 249

    WangX.ChangY.LiY.ZhangX.GoodrichD. W. (2006). Thoc1/Hpr1/p84 is essential for early embryonic development in the mouse.Mol. Cell. Biol.2643624367. 10.1128/MCB.02163-05

  • 250

    WangY.PutnamC. D.KaneM. F.ZhangW.EdelmannL.RussellR.et al (2005). Mutation in Rpa1 results in defective DNA double-strand break repair, chromosomal instability and cancer in mice.Nat. Genet.37750755. 10.1038/ng1587

  • 251

    WangZ. Q.AuerB.StinglL.BerghammerH.HaidacherD.SchweigerM.et al (1995). Mice lacking ADPRT and poly(ADP-ribosyl)ation develop normally but are susceptible to skin disease.Genes Dev.9509520. 10.1101/gad.9.5.509

  • 252

    WardI. M.MinnK.Van DeursenJ.ChenJ. (2003). p53 Binding protein 53BP1 is required for DNA damage responses and tumor suppression in mice.Mol. Cell. Biol.2325562563. 10.1128/mcb.23.7.2556-2563.2003

  • 253

    WatanabeN.AraiH.NishiharaY.TaniguchiM.WatanabeN.HunterT.et al (2004). M-phase kinases induce phospho-dependent ubiquitination of somatic Wee1 by SCFbeta-TrCP.Proc. Natl. Acad. Sci. U.S.A.10144194424. 10.1073/pnas.0307700101

  • 254

    WatsonC. M.TamP. P. (2001). Cell lineage determination in the mouse.Cell Struct. Funct.26123129.

  • 255

    WeissR. S.EnochT.LederP. (2000). Inactivation of mouse Hus1 results in genomic instability and impaired responses to genotoxic stress.Genes Dev.1418861898.

  • 256

    WenB.LiR.ChengK.LiE.ZhangS.XiangJ.et al (2017). Tetraploid embryonic stem cells can contribute to the development of chimeric fetuses and chimeric extraembryonic tissues.Sci. Rep.7:3030. 10.1038/s41598-017-02783-0

  • 257

    WilhelmT.OlzierskyA.-M.HarryD.De SousaF.VassalH.EskatA.et al (2019). Mild replication stress causes chromosome mis-segregation via premature centriole disengagement.Nat. Commun.10:3585. 10.1038/s41467-019-11584-0

  • 258

    XanthoudakisS.SmeyneR. J.WallaceJ. D.CurranT. (1996). The redox/DNA repair protein, Ref-1, is essential for early embryonic development in mice.Proc. Natl. Acad. Sci. U.S.A.9389198923. 10.1073/pnas.93.17.8919

  • 259

    XiaoY.WeaverD. T. (1997). Conditional gene targeted deletion by Cre recombinase demonstrates the requirement for the double-strand break repair Mre11 protein in murine embryonic stem cells.Nucleic Acids Res.2529852991. 10.1093/nar/25.15.2985

  • 260

    XiaoZ.ChenZ.GunasekeraA. H.SowinT. J.RosenbergS. H.FesikS.et al (2003). Chk1 mediates S and G2 arrests through Cdc25A degradation in response to DNA-damaging agents.J. Biol. Chem.2782176721773. 10.1074/jbc.M300229200

  • 261

    XieR.MedinaR.ZhangY.HussainS.ColbyJ.GhuleP.et al (2009). The histone gene activator HINFP is a nonredundant cyclin E/CDK2 effector during early embryonic cell cycles.Proc. Natl. Acad. Sci. U.S.A.1061235912364. 10.1073/pnas.0905651106

  • 262

    XuY.AshleyT.BrainerdE. E.BronsonR. T.MeynM. S.BaltimoreD. (1996). Targeted disruption of ATM leads to growth retardation, chromosomal fragmentation during meiosis, immune defects, and thymic lymphoma.Genes Dev.1024112422. 10.1101/gad.10.19.2411

  • 263

    YamazakiS.IshiiA.KanohY.OdaM.NishitoY.MasaiH. (2012). Rif1 regulates the replication timing domains on the human genome.EMBO J.3136673677. 10.1038/emboj.2012.180

  • 264

    YangW.KlamanL. D.ChenB.ArakiT.HaradaH.ThomasS. M.et al (2006). An Shp2/SFK/Ras/Erk signaling pathway controls trophoblast stem cell survival.Dev. Cell10317327. 10.1016/j.devcel.2006.01.002

  • 265

    YataK.BleuyardJ. Y.NakatoR.RalfC.KatouY.SchwabR. A.et al (2014). BRCA2 coordinates the activities of cell-cycle kinases to promote genome stability.Cell Rep.715471559. 10.1016/j.celrep.2014.04.023

  • 266

    YonemasuR.MinamiM.NakatsuY.TakeuchiM.KuraokaI.MatsudaY.et al (2005). Disruption of mouse XAB2 gene involved in pre-mRNA splicing, transcription and transcription-coupled DNA repair results in preimplantation lethality.DNA Repair4479491. 10.1016/j.dnarep.2004.12.004

  • 267

    YoonJ. C.LingA. J.IsikM.LeeD. Y.SteinbaughM. J.SackL. M.et al (2014). GLTSCR2/PICT1 links mitochondrial stress and Myc signaling.Proc. Natl. Acad. Sci. U.S.A.11137813786. 10.1073/pnas.1400705111

  • 268

    YoshidaK.KuoF.GeorgeE. L.SharpeA. H.DuttaA. (2001). Requirement of CDC45 for postimplantation mouse development.Mol. Cell. Biol.2145984603. 10.1128/MCB.21.14.4598-4603.2001

  • 269

    ZauggK.SuY. W.ReillyP. T.MoolaniY.CheungC. C.HakemR.et al (2007). Cross-talk between Chk1 and Chk2 in double-mutant thymocytes.Proc. Natl. Acad. Sci. U.S.A.10438053810. 10.1073/pnas.0611584104

  • 270

    ZaveriL.DhawanJ. (2018). Cycling to meet fate: connecting pluripotency to the cell cycle.Front. Cell Dev. Biol.6:57. 10.3389/fcell.2018.00057

  • 271

    ZellwegerR.DalcherD.MutrejaK.BertiM.SchmidJ. A.HerradorR.et al (2015). Rad51-mediated replication fork reversal is a global response to genotoxic treatments in human cells.J. Cell Biol.208563579. 10.1083/jcb.201406099

  • 272

    ZemanM. K.CimprichK. A. (2014). Causes and consequences of replication stress.Nat. Cell Biol.1629. 10.1038/ncb2897

  • 273

    ZhangY.HunterT. (2014). Roles of Chk1 in cell biology and cancer therapy.Int. J. Cancer13410131023. 10.1002/ijc.28226

  • 274

    ZhangY.ZolovS. N.ChowC. Y.SlutskyS. G.RichardsonS. C.PiperR. C.et al (2007). Loss of Vac14, a regulator of the signaling lipid phosphatidylinositol 3,5-bisphosphate, results in neurodegeneration in mice.Proc. Natl. Acad. Sci. U.S.A.1041751817523. 10.1073/pnas.0702275104

  • 275

    ZhaoB.ZhangW.CunY.LiJ.LiuY.GaoJ.et al (2018). Mouse embryonic stem cells have increased capacity for replication fork restart driven by the specific Filia-Floped protein complex.Cell Res.286989. 10.1038/cr.2017.139

  • 276

    ZhaoB.ZhangW. D.DuanY. L.LuY. Q.CunY. X.LiC. H.et al (2015). Filia Is an ESC-Specific Regulator of DNA Damage Response and Safeguards Genomic Stability.Cell Stem Cell16684698. 10.1016/j.stem.2015.03.017

  • 277

    ZhengP. (2020). Maintaining genomic stability in pluripotent stem cells.Genome Instabil. Dis.19297.

  • 278

    ZhouZ.WangL.GeF.GongP.WangH.WangF.et al (2018). Pold3 is required for genomic stability and telomere integrity in embryonic stem cells and meiosis.Nucleic Acids Res.4634683486. 10.1093/nar/gky098

  • 279

    ZhuJ.PetersenS.TessarolloL.NussenzweigA. (2001). Targeted disruption of the Nijmegen breakage syndrome gene NBS1 leads to early embryonic lethality in mice.Curr. Biol.11105109. 10.1016/s0960-9822(01)00019-7

  • 280

    Ziegler-BirlingC.HelmrichA.ToraL.Torres-PadillaM.-E. (2009). Distribution of p53 binding protein 1 (53BP1) and phosphorylated H2A.X during mouse preimplantation development in the absence of DNA damage.Int. J. Dev. Biol.5310031011. 10.1387/ijdb.082707cz

  • 281

    ZimmermannM.LottersbergerF.BuonomoS. B.SfeirA.De LangeT. (2013). 53BP1 regulates DSB repair using Rif1 to control 5′ end resection.Science339700704. 10.1126/science.1231573

  • 282

    ZongD.AdamS.WangY.SasanumaH.CallenE.MurgaM.et al (2019). BRCA1 haploinsufficiency is masked by RNF168-mediated chromatin ubiquitylation.Mol. Cell7312671281.e7. 10.1016/j.molcel.2018.12.010

Summary

Keywords

early development, embryology, pluripotency, DNA damage response, DNA repair, DNA replication, replication stress response

Citation

Kafer GR and Cesare AJ (2020) A Survey of Essential Genome Stability Genes Reveals That Replication Stress Mitigation Is Critical for Peri-Implantation Embryogenesis. Front. Cell Dev. Biol. 8:416. doi: 10.3389/fcell.2020.00416

Received

10 February 2020

Accepted

05 May 2020

Published

29 May 2020

Volume

8 - 2020

Edited by

Liz Caldon, Garvan Institute of Medical Research, Australia

Reviewed by

Fumiko Esashi, University of Oxford, United Kingdom; Yibo Luo, The University of Toledo, United States

Updates

Copyright

*Correspondence: Anthony J. Cesare,

This article was submitted to Cell Growth and Division, a section of the journal Frontiers in Cell and Developmental Biology

Disclaimer

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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