REVIEW article

Front. Endocrinol., 04 May 2022

Sec. Reproduction

Volume 13 - 2022 | https://doi.org/10.3389/fendo.2022.876370

Proteolysis in Reproduction: Lessons From Gene-Modified Organism Studies

  • 1. Research Institute for Microbial Diseases, Osaka University, Suita, Japan

  • 2. PRESTO, Japan Science and Technology Agency, Kawaguchi, Japan

  • 3. The Institute of Medical Science, The University of Tokyo, Tokyo, Japan

  • 4. CREST, Japan Science and Technology Agency, Kawaguchi, Japan

Abstract

The physiological roles of proteolysis are not limited to degrading unnecessary proteins. Proteolysis plays pivotal roles in various biological processes through cleaving peptide bonds to activate and inactivate proteins including enzymes, transcription factors, and receptors. As a wide range of cellular processes is regulated by proteolysis, abnormalities or dysregulation of such proteolytic processes therefore often cause diseases. Recent genetic studies have clarified the inclusion of proteases and protease inhibitors in various reproductive processes such as development of gonads, generation and activation of gametes, and physical interaction between gametes in various species including yeast, animals, and plants. Such studies not only clarify proteolysis-related factors but the biological processes regulated by proteolysis for successful reproduction. Here the physiological roles of proteases and proteolysis in reproduction will be reviewed based on findings using gene-modified organisms.

Introduction

Although a simple peptide bond between two amino acids in water at room temperature has a half-life of several years (), the hydrolysis of a peptide bond is significantly accelerated under the presence of proteases. As well as mediating non-specific protein hydrolysis, proteases also act as processing enzymes that perform highly selective, limited, and efficient cleavage of specific substrates. As many biological processes are influenced by this irreversible post-translational protein modification, dysregulation of the expression and/or function of proteases underlie many human pathological processes and have therefore been an intensely studied class of targets for drug discovery.

By searching Saccharomyces cerevisiae, Drosophila melanogaster, and Caenorhabditis elegans genome databases with a gene ontology term “peptidase activity” (GO:0008233), 51, 506, and 448 genes encoding proteases, respectively, can be identified (). In the mouse and human genome, 628 and 553 protease genes exist, respectively (). In Arabidopsis thaliana, 723 protease genes were reported (). Based on catalytic mechanisms, proteases can be divided into five classes: cysteine proteases, serine proteases, metalloproteases, threonine proteases, and aspartic proteases. After activation of the amide, cysteine, serine, and threonine proteases utilize the namesake residue to attack the amide carbonyl group, whereas metalloproteases and aspartic proteases use an activated water molecule as a nucleophile. As proteases bind their substrates between the substrate side chains and well-defined substrate-binding pockets within the active site, they have their own preference for substrate amino acid sequence proximal to the cleavage site (). There are some enzymatically inactive pseudoproteases encoded in the mammalian genome in which the amino acid residues indispensable for catalytic activity are substituted. As proteases are potentially toxic, their activities are strictly regulated as such by pH, specific ion concentrations, posttranslational modifications, and spatiotemporal expression of protease inhibitors.

The contribution of proteases depends on their intracellular or extracellular localization where they act on substrate proteins. The ubiquitin-proteasome system (UPS) is a complex but sophisticated intracellular proteolytic system in eukaryotes; this complex system degrades unneeded or damaged proteins by proteolysis. When target proteins are post-translationally labeled with ubiquitin, a protein of 76-amino acid residues exhibiting high sequence conservation among eukaryotes, they will be recognized and degraded by the proteasome.

Proteolytic processing events are fundamental in reproductive processes including gametogenesis, fertilization, and embryonic development. Recent advances in generating gene-modified animals have identified many proteases and their regulators associated with reproduction in various species including yeast, invertebrates, vertebrates, and plants. In the following sections the physiological importance of proteolysis in reproduction will be overviewed based on findings obtained by gene-modified organism studies. Proteolysis-related genes essential in reproduction identified by gene-modified animal studies are listed in Table 1. Few proteins are known to be proteolytically processed under certain reproductive situations. They are, however, not included in this review as the physiological roles of such processing in reproduction are not fully clarified at present.

Table 1

GeneProtein featureProtein localizationGene-modified organismFertilityPhenotypeRefs.
S. cerevisiae
ste24Prenyl protein-specific endoproteaseIntracellular membraneEthylmethane-sulfonate (EMS) mutagenesisSterileMAT a-specific sterility. ()
axl1MetalloproteaseIntracellularUV exposureSterileDefect in a-factor pheromone secretion. ()
C. elegans
cpi-2aCystatin-like cysteine protease inhibitorExtracellularDeletion mutantSterileOocyte-specific sterility. ()
gon-1MetalloproteaseExtracellularEMS mutagenesisSterileGonadal developmental defect. (, )
timp-1Metalloprotease inhibitorExtracellularTrimethylpsoralen (TMP)–UV-mutagenesisSterileGonadal growth defect. ()
dss-126S proteasome subunitIntracellularDeletion mutantSterileDefects in oogenesis. ()
dpf-3Serine proteaseIntracellularDeletion mutantSterileImpaired spermatogenesis. ()
sup-17; adm-4ADAM metalloproteasesCell membraneEMS mutagenesis; TMP)–UV-mutagenesisSterileAberrant spermathecal function. ()
pam-1MetalloproteaseIntracellularRNAi
knockdown
SubfertilityDecreased brood size. Expanded pachytene. ()
try-5Serine proteaseExtracellularDeletion mutantFertiletry-5 functions in parallel to spe-8 for male fertility. ()
swm-1Trypsin inhibitor-likeExtracellularEMS mutagenesisReduced male fertilityEctopic sperm activation within the male reproductive tract. Failure of sperm transfer to hermaphrodite. ()
gcna-1MetalloproteaseNucleusDeletion by CRISPR/Cas9Fertility defectsDecrease of fertility in later generations because of genomic instability ()
T12E12.6MetalloproteaseIntracellularRNAi
knockdown
SubfertilityDecreased brood size. ()
zmp-2MetalloproteaseExtracellularRNAi
knockdown
SubfertilityReduced offspring production. ()
D. melanogaster
CG9000; CG9001; CG9002Yeast ste24p ortholog proteasesIntracellular membraneEnds-out gene targetingMale fertility defectsAbnormal spermatid maturation. ()
Prosalpha6TProteasome subunitIntracellularKOMale infertilitySpermatogenic defects in sperm individualization and nuclear maturation. ()
DubaDeubiquitylating enzymeIntracellularImprecise P-element excisionMale infertilityDefects in spermatid individualization. ()
DroncCysteine proteaseIntracellularTransgenic expression of dominant-negative DRONCUncertainDefects in spermatid individualization. ()
DreddCysteine proteaseIntracellularEMS mutagenesisFertileDefects in spermatid individualization. ()
DarkCaspase activatorIntracellularEnhancer trapMale infertilityDefects in spermatid individualization. ()
Htra2Serine proteaseMitochondriaP element mobilizationMale infertilitySperm were completely immotile ()
EMS mutagenesisMale infertilityDefective spermatogenesis. ()
S-Lap1-8Leucylamino-peptidaseIntracellularClassical mutant, CRISPR/Cas9Male infertility or subfertilityDeficient accumulation of paracrystalline material in mitochondria. ()
SemsTrypsin-like proteaseExtracellularKnockdownMale subfertilityFemales laid fewer number of eggs when mated to Sems knockdown males. Sperm remained in storage in the seminal receptacle. ()
Nep4Metalloprotease
Mmel1 ortholog
Cell membraneKOMale infertilityMutant sperm are quickly discarded
by females.
()
Dcp-1Cysteine proteaseIntracellularFemale carrying germline   KO cloneFemale infertilityDefective oogenesis. ()
mhMetalloproteaseNucleusEMS mutagenesis,
P element mobilization
Female infertilityThe integration of paternal chromosomes in the zygote was specifically affected. (, )
AnceAngiotensin-converting enzymeExtracellularEMS mutagenesisMale infertilityCompound heterozygotes for two different lethal alleles are male sterile. ()
SlfcSerine proteaseExtracellularRNAi
knockdown
Male infertilityDetails are unknown. Females also show slightly decreased fertility. ()
omeSerine proteaseCell membraneEMS mutagenesisMale subfertilityDetails are uncertain. ()
Mmp2MetalloproteaseExtracellularRNAiFemale subfertilityOvulation was blocked. ()
A. socius
ejac-spSerine proteaseExtracellularRNAi knockdownMale subfertilityReduced ability to induce a female to lay eggs. ()
Bombyx mori
OspSerine proteaseCell membraneKOFemale infertilityMutant females laid fewer eggs than wild-type females and eggs did not hatch ()
Ser2Serine proteaseExtracellularKOMale infertilityWild-type females mated with mutant males laid eggs normally but the eggs did not hatch. ()
Spodoptera litura
OspSerine proteaseCell membraneKOFemale infertilityMutant females laid fewer eggs than wild-type females and eggs did not hatch. ()
Plutella xylostella
Ser2Serine proteaseExtracellularKOMale infertilityMutant sperm morphology is normal but they do not enter eggs. ()
Hyphantria cunea
Hcser2Serine proteaseExtracellularRNAi knockdown,
KO
Male infertilityThe growth, development, mating behavior, or egg laying was not affected. ()
Bactrocera dorsalis
Bdcp-1Cysteine proteaseIntracellularRNAi knockdownFemale infertilityImpaired ovary development. ()
M. musculus
Psma8Proteasome componentNucleusKOMale infertilityArrested spermatogenesis at spermatocyte stage. ()
Psme3Proteasome
activator
IntracellularKOMale subfertilityDecreased sperm number and motility. ()
Psme4Proteasome
activator
NucleusKOSevere male subfertilityDefective spermatogenesis. ()
Psme3;
Psme4
Proteasome
activator
IntracellularDouble KOMale infertilityMorphologically normal sperm with motility defect. ()
Cops5Metalloprotease IntracellularKOMale infertilityMale infertility. Germ cells undergo significant apoptosis at a premeiotic stage. ()
Usp2Ubiquitin-specific proteaseNucleusKOMale subfertilityDefects in sperm motility. ()
Usp9xUbiquitin-specific proteasecytoplasmVasa-cre; Usp9xfl/YMale infertilityApoptosis of spermatocytes. ()
Usp26Ubiquitin-specific proteaseIntracellularKOSevere male subfertilityUnsynapsed chromosomes in pachynema and defective chiasma formation in diplonema, apoptosis of metaphase spermatocytes and decrease of spermatids. (, )
Usp1Ubiquitin-specific proteaseNucleusKOMale infertilityImpaired spermatogenesis. ()
Apaf1Caspase activatorIntracellularKOMale infertilityDegeneration of spermatogonia resulting in the absence of sperm. ()
Agbl5MetalloproteaseIntracellularKOMale infertilityDefective spermatogenesis (, )
GcnaMetalloproteaseNucleusKOMale infertilityNearly devoid of sperm. ()
Tasp1EndopeptidaseNucleusKOMale infertilityRelease immature germ cells. ()
Tysnd1Serine proteasePeroxisomeKOMale infertilityGlobozoospermia, no acrosomal cap. ()
Spink2Serine protease inhibitorExtracellularKOMale infertilityOligoasthenoteratozoospermia in heterozygotes, azoospermia in homozygotes. ()
Serpina5Serine protease inhibitorExtracellularKOMale infertilityAbnormal spermatogenesis due to destruction of the Sertoli cell barrier. ()
Adamts2MetalloproteinaseExtracellularKOMale infertilityMarked decrease in testicular sperm. ()
AcrSerine proteaseAcrosomeKOMale subfertilityDelayed fertilization. (, )
Pcsk4Serine proteaseAcrosomal membraneKOMale subfertilityPutatively due to impaired fertilization. (, )
Tmprss12Serine proteasePlasma membraneKOMale infertilityDeficient sperm migration into oviduct. ()
Prss55Serine proteasePlasma membraneKOMale infertilityDeficient sperm migration into oviduct. (, )
Tryx5Serine proteasePlasma membraneKOMale infertilityDeficient sperm migration into oviduct. ()
Prss37PseudoproteasePlasma membraneKOMale infertilityDeficient sperm migration into oviduct. ()
AceMetallo-carboxypeptidasePlasma membraneKOMale subfertilityDeficient sperm migration into oviduct. ()
Adam1aPseudoproteasePlasma membraneKOMale infertilityDeficient sperm migration into oviduct. ()
Adam2PseudoproteasePlasma membraneKOMale subfertilityDeficient sperm migration into oviduct ()
Adam3PseudoproteasePlasma membraneKOMale infertilityDeficient sperm migration into oviduct. (, )
Adam6PseudoproteasePlasma membraneKOMale infertilityDeficient sperm migration into oviduct. ()
Cst8; Cst9; Cst11; Cst12; Cst13; Cstdc1; Cstdc2; Cstl1Cystatin-like inhibitorExtracellularMultiple KOMale infertilityDeficient sperm migration into oviduct. ()
Ovch2Serine proteaseExtracellularKOMale infertilityDeficient sperm migration into oviduct. ()
Mmel1MetalloproteaseExtracellularKOMale infertilityNormal spermatogenesis but reduced egg fertilization. ()
Prss21Serine proteasePlasma membraneKOMale subfertility, decreased in vitro fertilityMutant spermatozoa possessed decreased motility, angulated and curled tails, and fragile necks. Decreased in vitro zona pellucida binding and acrosome reaction. (, )
CpeMetalloproteaseExtracellularSpontaneous mutationMale subfertilityAbnormal sexual behavior. Abnormal testis morphology in older mutant males. ()
Adam24PseudoproteasePlasma membraneKOMale subfertilityPolyspermic fertilization. ()
Adam7PseudoproteasePlasma membraneKOMale subfertilityDecreased cell height in caput epididymis, spermatic granuloma, kinked sperm flagellum and reduced sperm motility. ()
Cst3Cysteine protease inhibitorExtracellularKI
(Leu68Gln)
Male subfertilityReduced viability of spermatozoa and large agglutinated clumps. ()
Serpine2Serine protease inhibitorExtracellularKOMale subfertilityInadequate semen coagulation and deficient vaginal plug formation upon copulation ()
Tmprss6Serine proteasePlasma membraneKOFemale infertilityMarked retardation in ovarian maturation. ()
AmbpSerine protease inhibitorExtracellularKOFemale subfertilityDefective cumulus matrix expansion. (, )
Psen1Aspartic proteaseEndoplasmic reticulum, Golgi, endosome, plasma membraneKI
(Leu166Pro)
Female infertilityPrimordial follicles near the ovarian cortex and consisting largely of ovarian stromal elements. ()
Adamts1MetalloproteaseExtracellularKOFemale subfertilityFewer numbers of mature follicles in ovary, thick and convoluted uterus. (, )
LonpSerine proteaseMitochondriaGdf9-cre or Zp3-cre; Lonp1fl/flFemale infertilityImpaired follicular development, progressive oocyte death, ovarian reserve loss. ()
FurinSerine proteaseGolgi, endosome, plasma membrane, extracellularGdf9-cre or Zp3-cre; Furinfl/flFemale infertilityArrest of early secondary follicles. ()
PappaMetalloproteaseExtracellularKOFemale subfertilityReduced litter size and reduced ovulatory capacity, probably because of decreased bioavailability of ovarian insulin-like growth factor. ()
AstlMetalloproteaseExtracellularKOFemale subfertilityNo ZP2 cleavage after fertilization. ()
FetubMetalloprotease inhibitorExtracellularKOFemale infertilityPremature zona pellucida hardening. ()
Serpinc1Serine protease inhibitorExtracellularKI
(Arg48Cys)
Female subfertilityThrombosis in placenta and penile vessels. ()
Adam10MetalloproteaseCell membraneTie2-cre; Adam10fl/flFemale subfertilityImpaired decidualization. ()
Adamts18MetalloproteaseExtracellularKOFemale infertility or subfertilityFifty percent of mutant females are infertile because of vaginal obstruction due to either a dorsoventral vaginal septum or imperforate vagina. ()
PlgSerine proteaseExtracellularKOFemale subfertilityCompromised female fertility. (, )
Timp1Metalloprotease inhibitorExtracellularKOFemale subfertilityReduction in reproductive lifespan. ()
Pcsk2Serine proteaseExtracellularKOFemale subfertilityDetails are uncertain. ()
Espl1Cysteine proteaseNucleusKI
Meox2cre; Espl1+/S1121A
Male infertilitySpermatogonia cell depletion. ()
Zp3-cre;
Espl1fl/fl
Female infertilityPrevention of chiasmata resolution. Failure to extrude polar bodies in Meiosis I. ()
Meox2cre; Espl1+/S1121AFemale infertilityPrimordial germ cell depletion by apoptosis during embryonic oogenesis. (, 107)
Zp3-cre; KI
(Ser1121Ala)
Female infertilityFailure in preimplantation development. (108)
Agtpbp1MetalloproteaseIntracellularSpontaneous mutation,
insertional mutation
Male infertilityDefective spermatogenesis. (109112)
Female subfertilityPoor development of secondary follicles into antral follicles. (113)
ClppSerine proteaseMitochondriaKOMale infertilityDisrupted spermatogenesis at the spermatid stage. (114)
Female infertilityOvarian follicular differentiation failure, premature reproductive aging. (114)
NpeppsMetallo-aminopeptidaseNucleus,
cytosol
Gene trapMale infertilityLack of copulatory behavior, impaired spermatogenesis. (115)
Female infertilityImpaired formation of corpus luteum in pregnancy. (116)
Ggt1ProteasePlasma membraneKOMale infertilityReduced testis and seminal vesicle size, reduced seminiferous tubule diameter. (117)
Female infertilityHypogonadal, absence of antral follicles and corpora lutea and follicular degeneration. (117)
Immp2lSerine proteaseMitochondriaKOSevere male subfertilityErectile dysfunction. (118)
Female infertilityDefective folliculogenesis and ovulation. (118)
Adam17MetalloproteaseExtracellularSox9-cre; Adam17fl/flMale subfertilityDetails are uncertain. (119)
Female infertilityDetails are uncertain. (119)
Mesocricetus auratus
AcrSerine proteaseAcrosomeKOMale infertilitySperm failure in zona pellucida penetration. (120)
R. norvegicus
Adamts16MetalloproteaseExtracellularKOMale infertilityCryptorchidism. (121, 122)
D. rerio
adamts9MetalloproteaseExtracellularKOFemale infertilityOvary malformation. (123)
H. sapiens
SPINK2Serine protease inhibitorExtracellularSpontaneous mutationMale infertilityAzoospermia. ()
GCNAMetalloproteaseNucleusSpontaneous mutationMale infertilityNon-obstructive azoospermia and cryptoospermia. (124, 125)
A. thaliana
A36Aspartic proteasePlasma membraneT-DNA insertionDecreased male transmissionReduced pollen germination. (126)
A36; A39Aspartic proteasePlasma membraneDouble KO by T-DNA insertionSeverely compromised male transmissionProgrammed cell death of microspores. Compromised micropylar guidance of pollen tubes. (126)
PCS1Aspartic proteaseEndoplasmic reticulumT-DNA insertionReduced male and female transmissionDegeneration of both male and female gametophytes. (127)
UNDAspartic proteaseMitochondriasiRNA and artificial microRNAPartial male sterilityApoptosis-like programmed cell death in tapetum and pollen. (128)
CEP1Cysteine proteaseVacuole, endoplasmic reticulumT-DNA insertionMale subfertilityMutants exhibited aborted tapetal PCD and decreased pollen fertility with abnormal pollen exine. (129)
SPF1; SPF2SUMO-specific cysteine proteaseDouble KO by T-DNA insertionMale and female sterilitySevere abnormalities in microgametogenesis, megagametogenesis, and embryo development. (130)
O. sativa
OsAP65Aspartic proteaseVacuoleT-DNA insertionMale sterilityNo germination or elongation of mutant pollen. (131)

Proteolysis-related genes associated with reproduction.

Unicellular Organisms

Saccharomyces cerevisiae

S. cerevisiae, Baker’s yeast, is a model diploid unicellular organism. S. cerevisiae can stably exist as either a diploid or a haploid. When stressed, S. cerevisiae can undergo meiosis to produce four haploid spores. Haploid cells are capable of fusing with other haploid cells of the opposite mating type (an ‘a’ cell can only mate with an ‘α’ cell, and vice versa) to produce a stable diploid cell. a and α cells produce mating peptide pheromones a-factor and α-factor, respectively. Ste24p and Axl1p encoded by ste24 and alx1, respectively, are metalloendopeptidases that process precursor peptide to produce mature mating a-factor pheromone (, ).

Multicellular Organisms I: Invertebrates

The body of multicellular organisms consists of two types of cells with different lineages, i.e., germ cells and somatic cells. Germ cells produce gametes for fertilization, whereas somatic cells develop reproductive organs to support gametogenesis and fertilization by germ cells. Therefore, dysfunction of proteolysis in either cell lineage can result in fertility defects.

Nematodes

Caenorhabditis elegans is androdioecious; i.e., it has two sexes, hermaphrodite and male, whereas Ascaris suum is dioecious, being either male or female. They develop two U-shaped gonads in which gametes are generated and fertilization occurs. Several proteases and inhibitors have been identified to regulate nematode reproductive processes.

Oogenesis and fertilization are affected when cpi-2a, encoding a cystatin-like cysteine protease inhibitor, is mutated (). Nullification of dss-1 encoding a 26S proteasome subunit provokes sterility because of deficient oogenesis (). Knockdown of puromycin-sensitive aminopeptidase encoded by pam-1 causes delayed oocyte maturation and subfertility (). Deletion of dpf-3 encoding a serine protease causes sterility because of impaired spermatogenesis (). gon-1 encoding a disintegrin-like and metalloproteinase domain with thrombospondin type 1 motif (ADAMTS) is necessary for morphogenesis of U-shaped gonads (, ). A mutant worm lacking timp-1 encoding a tissue inhibitor of metalloproteinase also shows deficient gonadal development (). A double mutant in which sup-17 and adm-4, encoding nematode orthologs of mammalian membrane metalloproteases ADAM10 and ADAM17, respectively, are sterile because of aberrant spermathecal function ().

Unlike mammalian flagellated sperm, nematode sperm are amoeboid cells. For successful fertilization, sperm must be activated prior to contacting an oocyte in both C. elegans and A. suum. This sperm activation is called spermiogenesis through which round immobile spermatids transform into motile, fertilization-competent spermatozoa. Mechanistically, spermiogenesis occurs by sensing extracellular signals and can be reproduced in vitro by exposing spermatids to proteases such as Pronase and proteinase K. A trypsin-like secreted protease encoded by try-5 is expressed in the vas deferens and triggers activation of spermatids (). swm-1 encodes a secreted protein with a trypsin inhibitor-like domain, and swm-1 mutant males are infertile because of ectopic premature activation of sperm (). Like in C. elegans, activation of spermatozoa by exposure to extrinsic protease in vitro can also be seen in several insect species (132, 133). spe-4 encoding a presenilin, an aspartyl protease with intramembrane proteolytic activity prevents spermatid activation because spe-4 mutant males progress directly to functional spermatozoa without the need for an activation signal (134).

gcna-1 encodes nuclear metalloprotease. gcna-1 deletion causes genomic instability decreasing fertility in later generations (). T12E12.6 encodes intracellular metalloprotease whereas zmp-2 encodes secreted metalloproteases. Knockdown of either of them results in reduced offspring production (, ).

Insects

The reproductive system of Drosophila melanogaster is more complex compared with nematodes; it is composed of gonads, genital ducts, and accessory structures. Several proteases have been implicated in D. melanogaster spermatogenesis. In the D. melanogaster genome, there are five genes paralogous to S. cerevisiae ste24 encoding a type I prenyl protease. Deletion of three tandemly arrayed ste24 paralogs results in male fertility defects manifesting late in spermatogenesis ().

All Drosophila spermatid nuclei descended from a primary spermatocyte remain connected to each other via an extensive network of cytoplasmic bridges. Spermatids should therefore be physically dissociated from each other by a process referred as individualization and a ubiquitin-proteasome system regulates this process. Males in which Prosalpha6T encoding a testis-specific proteasome core particle subunit was ablated are sterile because of defects in sperm individualization and nuclear maturation (). Duba encodes a deubiquitylating enzyme and Duba null mutants are male sterile and display defects in spermatid individualization (). The non-apoptotic function of caspases also contributes to individualization. DARK is a Drosophila homolog of mammalian caspase activator Apaf-1, whereas DRONC and DREDD are Drosophila apical caspases. Flies deficient in DARK or expressing a dominant-negative version of DRONC failed individualization (, 135). Dredd-null flies also often show individualization defects ().

In D. melanogaster sperm, mitochondrial derivatives run along the entire flagellum to provide structural rigidity for flagellar movement. Two mitochondrial derivatives (i.e., major and minor) differentiate and major one accumulates paracrystalline material by the end of spermatogenesis. S-Lap1-8, Sperm-Leucylaminopeptidase (S-Lap) family members are constituents of paracrystalline material. S-Lap mutants possess defects in paracrystalline material accumulation and abnormal structure of the elongated major mitochondrial derivatives and male sterility (). Htra2 encodes a mitochondrial serine protease. In one Htra2-null mutant line males are infertile because sperm are completely immotile (), whereas spermatogenesis is defective in another Htra2 mutant line ().

Seminal fluid produced in the accessory gland includes proteases and protease inhibitors and is thought to contribute to fertilization in a post-mating manner. Seminase is a trypsin-like protease encoded by Sems and included in seminal fluid. When females mated with Sems knockdown males, they laid significantly fewer eggs (). In cricket, Allonemobius socius, an ejaculate serine protease encoded by ejac-sp is expressed in male reproductive accessory glands. RNAi knockdown of ejac-sp resulted in a significant reduction of the male’s ability to induce a female to lay eggs (). Nep4, a drosophila ortholog of mammalian Mmel1, encodes a metalloprotease expressed in male gonads (136). Nep4 mutant males are infertile; mutant sperm are quickly discarded by females (). When Dcp-1 encoding a cysteine protease was ablated in their germline, the resulting females were infertile because of defective oogenesis ().

Several proteases also of concern in Drosophila reproduction include maternal haploid or mh encodes the Drosophila homolog of SPRTN, a conserved metalloprotease essential for resolving DNA–protein cross-linked products. Paternal chromatids of mh mutants are unable to separate in the anaphase of the first embryonic mitosis and form a chromatin bridge. As a consequence, haploid nuclei of maternal origin rapidly separate from the damaged paternal chromosomes and haploid embryos develop but become lethal in a maternal effect manner (, , 137). Ance encodes a putative homologue of mammalian angiotensin-converting enzyme (ACE). Compound heterozygote for two different Ance lethal alleles exhibit male sterility (), but the molecular details are unknown. RNAi knockdown of Slfc encoding a secreted serine protease causes male infertility (). When a membrane serine protease encoded by ome was mutated, males became subfertile (). RNAi knockdown of a secreted metalloprotease encoded by Mmp2 caused female subfertility because ovulation was blocked ().

Several pest control attempts target reproduction-associated proteases. In pests Spodoptera litura and Plutella xylostella, targeted inactivation of serine protease genes Osp and Ser2, respectively, resulted in female and male infertility as also observed in silkworm moth Bombyx mori (, ). In other pests Hyphantria cunea, and Bactrocera dorsalis, RNAi knockdown of Hcser2, and Bdcp-1 encoding serine protease and cysteine protease, respectively, also resulted in infertility (, ). Thus, proteases are potential targets for pest population control.

Multicellular Organisms II: Vertebrates

Findings in vertebrates were obtained by genetic studies in rodents, fish, and human patients. Genes disrupted in these species include those encoding proteases, protease inhibitors, and non-catalytically active pseudo-proteases. Proteolysis-related factors are included in various aspects of male and female reproductive processes such as gamete production, gamete maturation, fertilization, post-fertilization events, and mating behavior.

UPS in Gamete Production

For the fine-tuning of cellular processes, intracellular proteins are timely degraded by UPS. The proteasome localizes in the nucleus and cytoplasm where it degrades ubiquitylated proteins. Spermatoproteasome, a testis-specific proteasome, is one of the three tissue-specific proteasomes identified together with the immunoproteasome and the thymoproteasome in mammals (138). Deletion of Psma8, which encodes a testis-specific 20S proteasome component, leads to spermatogenesis arrest at the spermatocyte stage (). Psme3 encodes REGγ, a proteasome activator. Psme3-null males are subfertile with decreased sperm number and motility (). This is probable because REGγ regulates p53-mediated transcription of Plzf, a transcription factor necessary for spermatogonial stem cell self-renewal and proliferation (139). Psme4 encodes PA200 proteasome activator. Psme4-null males have reduced fertility due to defects in meiotic spermatocytes and post-meiotic spermatids (). Psme3;Psme4 double KO males were infertile; mutant sperm appeared morphologically normal but exhibited remarkable defects in motility and decreased proteasome activity ().

Proteasome target proteins are ubiquitylated by E3 ubiquitin ligases which transfer the ubiquityl group from E2 ligase to the target protein. There are ∼600 E3 ligases encoded in the mammalian genome (140). The ubiquitin ligases, which are not proteases but included in ubiquitin-proteasome system-mediated protein degradation, indispensable for mammalian reproduction are listed in Table 2. Here only Huwe1 is mentioned as how E3 ligases function in reproductive processes. Huwe1 ubiquitylates histone H2AX, which is phosphorylated in response to DNA damage and is essential to the efficient recognition and repair of DNA double-strand breaks. Germline-specific Huwe1 ablation increased histone H2AX level, elevated DNA damage response, and caused Sertoli cell only phenotype. Thus Huwe1 likely regulates the response to spontaneous DNA damage by UPS-mediated H2AX degradation to maintain cell survival (156).

Table 2

GeneTypeGene-modified organismPhenotypeRefs.
D. melanogaster
rae1E3 ligase componentms (2)Z5584 mutationMale infertile, striking defects in primary spermatocyte nuclear integrity, meiotic chromosome condensation, segregation, and spindle morphology. (141)
parkinE3 ligaseP element insertionFemale infertility. (142)
cul3E3 ligaseEMS mutagenesisMale infertility (143)
C. elegans
mel-26E3 ligaseEMS mutagenesisGerm cell depletion and sterility. (144)
skr-1, skr-2E3 ligase componentRNAi
knockdown
Hermaphrodites are sterile. Arrested germline development in pachytene stage, expanded transition zone, and the presence of gaps in the gonad arm. (145)
vhl-1E3 ligaseRNAi
knockdown
Reduced fertility. (146)
M. musculus
ChfrE3 ligaseKO30% of KO male were infertile. (147)
Cul4aE3 ligase componentKOMale infertility phenotype resulted from a combination of decreased spermatozoa number, reduced sperm motility and defective acrosome formation. (148, 149)
Cul4bE3 ligaseVasa-cre;
Cul4bfl/Y
Male infertility. (150)
Cul4b-/YMale infertility. (151)
Dcaf17E3 ligaseKOMale infertility due to abnormal sperm development. (152)
Dcaf8E3 ligaseKOPronounced sperm morphological abnormalities with typical bent head malformation. (153)
Dcun1d1E3 ligase component for neddylationKOMalformed spermatozoa with supernumerary and malpositioned centrioles. (154)
Fbxw7E3 ligase componentAmh-cre;
Fbxw7fl/fl
Impaired testis development, which is characterized by age-dependent tubular atrophy, excessive germ cell loss, and spermatogenic arrest, and the mutant males were infertile at 7 months old (155)
Huwe1E3 ligaseDdx4-cre;
Huwe1fl/Y
Male infertile, Sertoli cell only phenotype. Increased level of histone H2AX and an elevated DNA damage response. (156)
E3 ligaseStra8-cre;
Huwe1fl/Y
Male infertile, spermatogenesis arrest. Accumulation of DNA damage response protein γH2AX. (157)
E3 ligaseZp3-cre;
Huwe1fl/fl
Oocyte death and female infertility. (158)
Mdm2E3 ligasePgr-cre; Mdm2fl/flFemale infertility. Impaired oocyte maturation, ovulation, and fertilization. (159)
Gdf9-cre;
Mdm2fl/fl
Female infertility. Complete lack of follicular structures resembling human premature ovarian failure. (160)
Zp3-cre;
Mdm2fl/fl
Female infertility. (160)
Amh-cre;
Mdm2fl/fl
Male infertile. degenerated testes with no organized seminiferous tubules and a complete loss of differentiated germ cells. (161)
Mgrn1E3 ligaseSpontaneousMale infertility. (162)
Phf7E3 ligaseKOMale infertility due to impaired protamine replacement in elongated spermatids. (163)
Rnf20E3 ligaseStra8-cre;
Rnf20fl/fl
Male infertility because of arrested spermatogenesis at the pachytene stage. (164)
Rnf216E3 ligaseKODisrupted spermatogenesis and male infertility. (165)
Rnf8E3 ligaseKOMale infertility. (166)
Gene trapMale infertility. (167)
Siah1aE3 ligaseKOFemale subfertility and male infertility. Interrupted spermatogenesis because of impaired progression past meiotic metaphase I. (168)
SpopE3 ligasePgr-cre;
Spopfl/fl
Female infertility because of impaired uterine decidualization. (169)
Syvn1 (Hrd1)E3 ligaseAlb-cre;
Hrd1fl/fl
Female infertility. (170)
Trim37E3 ligaseKOMale and female infertility. (171)
Trim71E3 ligaseNanos3-cre;
Trim71fl/–
Male infertility because of Sertoli cell-only phenotype. (172)
Ubr2E3 ligaseKOMale infertility caused by arrested spermatogenesis at meiotic prophase I. (173)
Uhrf1E3 ligaseStra8-cre; Uhrf1fl/flFailure of meiosis and male infertility. (174)
Zp3-cre;
Uhrf1fl/fl
Female infertility. (175)
Rad6bE2 ligaseKOMale infertility because of the loss of spermatogenesis (166)
Ube2iE2 ligaseGdf9-icre;
Ube2ifl/fl
Female infertility with major defects in stability of the primordial follicle pool, ovarian folliculogenesis, ovulation and meiosis. (176)
Ube2j1E2 ligaseKOMale infertility because of deficient spermatogenesis. (177)
Ube2q1E2 ligaseKOReduced female fertility. Altered estrus cycle, abnormal sexual behavior and reduced offspring care, and significantly increased embryonic lethality in the uterus of mutant females. (178)
H. sapiens
RNF220E3 ligaseSpontaneous mutationSmall-headed sperm. (179)
A. thaliana
PUB4E3 ligaseT-DNA
insertion
Male sterility. (180)
SAPE3 ligase componentTwo-element Enhancer-Inhibitor transposon systemMale and female sterility. Severe aberrations in inflorescence and flower and ovule development. Carpelloid sepals, short and narrow or absent petals, and degenerated anthers. (181)
SIZ1SUMO E3 ligaseT-DNA
insertion
Arrest of funicular and micropylar pollen tube guidance. (182)
MMS21SUMO E3 ligaseT-DNA
insertion
Severely reduced fertility, deficient gametogenesis. (183)
O. sativa
SIZ1SUMO E3 ligaseT-DNA
insertion
Spikelet sterility caused by defective anther dehiscence. (184)

The ubiquitin ligases indispensable for mammalian reproduction.

Cullin-RING E3 ubiquitin ligases are known to be reversibly neddylated, i.e., conjugated with NEDD8, a ubiquitin-like protein. By conjugation with NEDD8, cullin-RING E3 ligases increase their stability and ligase activity. The constitutive photomorphogenic-9 signalosome (CSN) deneddylates cullin-RING E3 ligases by cleaving the isopeptide bond of neddylated lysine to regulate the cellular ubiquitylation status. COPS5 is the fifth component of the CSN and abundant in mouse testis (185). Cops5-null males were infertile because of significant reduction of sperm number caused by premeiotic apoptosis of germ cells ().

Ubiquitylated proteins can be deubiquitylated by deubiquitylating enzymes such as ubiquitin-specific proteases (USPs), cysteine endopeptidases encoded by Usp genes, thereby expression levels and activity of target proteins are regulated. USP1 deubiquitylates FANCD2 which is included in the repair of DNA crosslinks. Usp1 null males were infertile and the seminiferous tubules were markedly atrophic and mostly devoid of spermatogenic cells in the mutant testis. Usp2-null males possessed severely reduced fertility and the mutant sperm were defective in sperm motility and egg fertilizing ability in vitro (). Germ cell-specific ablation of Usp9x using Vasa-cre possessed spermatogenic cell apoptosis at the early spermatocyte stage and resulted in complete infertility (). Usp26 is an X-linked gene exclusively expressed in testis (186). Usp26 -null males are subfertile because of reduced number of haploid cells in testis (, ). Usp1-null female mice showed reduced fertility probably because of a reduced number of oocytes in ovaries (). Thus, UPS is critically important for germ cell production in both sexes.

Non-Proteasomal Intracellular and Extracellular Proteolysis Factors in Sperm Production

Intracellular and extracellular proteolysis factors critically function in spermatogenesis. Cleavage of specific peptide bonds also contributes to spermatogenesis. Apaf1 encodes a caspase activator, and Apaf1-null males are infertile because of degeneration of spermatogonia, which results in the absence of sperm (). Agbl5 encodes an intracellular metalloprotease. Agbl5-null males are infertile because of defective spermatogenesis (, ). A cytosolic carboxypeptidase 1, another metalloprotease encoded by Agtpbp1 deglutamylates polyglutamylated proteins. Agtpbp1 mutant mice known as Purkinje cell degeneration (pcd) possess male infertility (109112) because of defective spermatogenesis (110). A germ cell nuclear antigen encoded by Gcna contains a metalloprotease domain. Gcna-null males are nearly devoid of sperm and infertile (). In human, GCNA spontaneous mutations were identified in spermatogenic failure patients (124, 125).

Separin, a caspase-like cysteine protease encoded by Espl1, plays a central role in chromosome segregation by cleaving the SCC1/RAD21 subunit of the cohesin complex (187189). A point mutation in Espl1 which substitutes inhibitory phosphorylation site Ser1121 to Ala depletes spermatogonia because of chromosome misalignment during proliferation of the postmigratory primordial germ cells and following mitotic arrest, aneuploidy, and cell death (). Threonine aspartase 1 (TASP1) is an intracellular endopeptidase that cleaves after distinct aspartate residues of the conserved IXQL(V)D/G motif (190). TASP1 cleaves general transcription factor TFIIAα−β to enable testis-specific transcription; Tasp1-null male mice were unable to activate spermatogenic gene activation, which lead to the release of immature germ cells and infertility (). A serine protease ClpP is located in the mitochondrial matrix and participates in mitochondrial protein quality control by degrading misfolded or damaged proteins. In Clpp-null mutants spermatogenesis was disrupted by the spermatid stage (114). Tysnd1 encodes a serine protease that processes peroxisomal leader peptides. Tysnd1-null mutant males possess globozoospermia and their spermatozoa lack the acrosomal cap (). Spink2 encodes a Kazal-type serine protease inhibitor abundantly expressed in testis and epididymis (191). Spink2-null males had azoospermia, and a homozygous splice mutation of SPINK2 was found in infertile men (). Ablation of Serpina5 encoding another serine protease inhibitor also results in an abnormality in sperm production in the testis ().

Puromycin-sensitive aminopeptidase encoded by Npepps is also an intracellular protease. It appears to contribute indirectly to spermatogenesis. Npepps-null testes and seminal vesicles were significantly reduced in weight, spermatogenesis was impaired, and copulatory behavior was lacking. It is suggested that the defects in the testes likely arises from dysfunction of Sertoli cells, whereas the lack of copulatory behavior results from defects in the brain (115).

A null mutation of Adamts2 encoding secreted metalloproteinase caused male infertility (). Decreased spermatogenesis was observed but copulatory behavior and/or copulatory plug formation may also be impaired because a copulatory plug was never observed ().

Proteolysis Factors Associated With Sperm Function

Acrosomal Function

The acrosome is a Golgi-derived sperm head organelle in which many digestive enzymes such as proteases and hyaluronidases are included to penetrate egg surroundings. Acrosin is a serine protease and a major component of the acrosome. Although acrosin-deficient male mice are fertile (, ), disruption of hamster acrosin resulted in complete male infertility (120). In vitro, mutant hamster spermatozoa attached to the zona pellucida, but failed to penetrate it (120), suggesting that acrosomal function can be attributed to specific factors in a species-specific manner.

Proprotein convertases convert inactive precursor proteins into their mature and active forms. PCSK4 is a member of proprotein convertases expressed on the sperm surface overlying the acrosome (). Pcsk4-null males showed impaired fertility (, ) and mutant sperm exhibited accelerated capacitation, precocious acrosome reaction, reduced binding to egg zona pellucida (). Acrosome formation during spermatogenesis was also abnormal (192).

Sperm Maturation

A group of genes encoding proteases, enzymatically inactive pseudoproteases, and protease inhibitors is apparently associated with the same physiological function, i.e., maturation of sperm conferring abilities to migrate into female oviduct and bind with zona pellucida. Ablation of Tmprss12 (), Prss55 (, ), Tryx5 (), Prss37 (), Ace (), Adam1a (), Adam2 (), Adam3 (, ), and Adam6 () results in deficient sperm migration into the oviduct and binding to the zona pellucida of eggs. Among them, Adam1a, Adam2, Adam3, Adam6, and Prss37 encode catalytically inactive pseudoproteases. A disintegrin and metallopeptidase domain (ADAM) 3, a catalytically inactive transmembrane pseudoprotease appears to be central to a molecular mechanism that governs sperm migratory and adhesion abilities, because ADAM3 expression is a prerequisite for sperm to acquire these abilities (193).

ADAM3 is expressed as a precursor and the processed into mature form as spermatozoa mature in epididymis (194). Similarly, enzymatically inactive pseudoproteases ADAM2 and ADAM6 are processed during sperm maturation in epididymis (195, 196). Therefore, they are rather substrates for other proteases. Ablation of ADAM2 or ADAM6 also results in significant decrease or loss of ADAM3 from epididymal sperm (, ) indicating the involvement of both ADAM2 and ADAM6 in ADAM3 expression. PRSS37 supports ADAM3 precursor translocation to the sperm cell surface by collaborating with PDILT, a testis-specific protein disulfide isomerase indispensable for ADAM3 surface expression (197, 198). TMPRSS12, PRSS55, and TRYX5, all of which are serine proteases and retain catalytic triad residues, are necessary for the production or stable localization of processed ADAM3 on the cell surface of epididymal spermatozoa (), although it remains uncertain whether these proteases directly cleave ADAM3.

Cystatins are secreted cysteine proteinase inhibitors. Cystatin genes Cst8, 9, 11, 12, 13, dc1, dc2, and l1 are clustered on mouse chromosome 2 and expressed in both testis and epididymis. Their simultaneous ablation resulted in the loss of ADAM3 from epididymal sperm and deficient sperm migration into the oviduct (), implying the importance of regulated proteolysis in sperm maturation. Ovochymase 2 (OVCH2) is a chymotrypsin-like serine protease. OVCH2 is specifically expressed in the caput epididymis under the regulation of lumicrine signaling, in which testis-derived secreted protein NELL2 transiting through the luminal space acts on the epididymal epithelium by binding to its receptor ROS1 tyrosine kinase to differentiate (). Ablation of Ovch2 results in abnormal sperm ADAM3 processing and deficient sperm migration into the oviduct (). Thus, regulated proteolysis on or outside spermatozoa apparently modulates sperm maturation.

NL1 encoded by Mmel1 is a zinc metallopeptidase expressed in testis. NL1 is expressed as a type II transmembrane protein but released as a soluble form. Mmel1-null mice show normal spermatogenesis but reduced egg fertilization, suggesting the role of NL1 in sperm maturation (). It remains, however, uncertain whether NL1 is included in ADAM3-mediated sperm maturation. Testisin encoded by Prss21 is a GPI-anchored serine protease. Prss21 KO males are subfertile because mutant spermatozoa possessed decreased motility, angulated and curled tails, and fragile necks (). In another Prss21 mutant line in vitro sperm binding to egg zona pellucida, acrosome reaction, and fertility were decreased ().

Other Proteolytic Factors Associated With Male Reproduction

Several cell surface and extracellular proteases and inhibitors seem to regulate male fertility in more indirect manners. Adamts16 homozygous mutant rat males resulted in cryptorchidism and male sterility (121). The mutant testis undescended during development because of the failure of gubernacular migration (122). γ-glutamyltranspeptidase 1 (GGT1) is a type II transmembrane protein which cleaves γ-glutamyl bond of extracellular glutathione (γ-Glu-Cys-Gly), glutathione conjugates, and other γ-glutamyl compounds. The resulting cysteinyl-glycine is further cleaved by dipeptidase into free amino acids. Ggt1-null males are infertile because of decreased epididymal sperm number and failure in copulatory plug formation (117). Although Ggt1-null testis was small, spermatogenesis inside seminiferous tubules appeared normal and seminal vesicles were hypoplastic. As N-acetylcysteine-fed mutant mice were fertile, the observed infertility is a consequence of cysteine deficiency (117),. Carboxypeptidase E (CPE) is a metallo-carboxypeptidase and functions as a prohormone processing exopeptidase. Cpefat/fat males are infertile and deficient in Pro-gonadotropin-releasing hormone processing in the hypothalamus (). ADAM24 is a metalloproteinase localized on the mature sperm surface. Adam24-null males are subfertile and polyspermic fertilization increased in vitro and in vivo, suggesting a physiological role of ADAM24 for prevention of polyspermy (). ADAM7 is a membrane-anchored protein with a catalytically-inactive metalloproteinase domain abundantly expressed in the epididymis (199). Adam7 ablation resulted in a modest reduction of male fertility; impaired epididymal morphology and integrity may affect sperm maturation ().

Cystatin C encoded by Cst3 is a cysteine protease inhibitor abundantly expressed in testis and epididymis. Substitution of Leu68 to Gln is an amyloid-forming mutation found in a hereditary form of cystatin C amyloid angiopathy. Heterozygous male mice were infertile and increased levels of amyloid was observed in the epididymal fluid (). Nonpathological function of amyloid during epididymal sperm maturation is also suggested (200).

Immp2l encodes an inner mitochondrial membrane peptidase 2-like. Immp2l-null homozygous males were severely subfertile because of erectile dysfunction (118). Tumor necrosis factor-α (TNFα) converting enzyme encoded by Adam17 is involved in the proteolytic release of the ectodomain of diverse cell surface proteins. Conditional ablation of Adam17 with Sox9-cre severely impaired male fertility but the details are uncertain (119).

Serpine2 encodes protease nexin-1, a serine protease inhibitor expressed in seminal fluid. Serpine2-null males possessed reduced fertility because of impaired semen coagulation and copulatory plug formation ().

Proteolytic Factors in Ovary and Follicle Development

Both intracellular and extracellular proteolytic factors are included in ovary and follicle development. Conditional ablation of separase under the control of Zp3-cre hindered extrusion of the first polar body and caused female sterility (). Introduction of a Ser1121 to Ala deregulatory mutation into separase led to primordial germ cell apoptosis during embryonic oogenesis (107). Ablation of cytosolic carboxypeptidase 1 encoded by Agtpbp1 results in female subfertility because secondary follicles poorly develop into antral follicles (113). Oocyte-specific ablation of nuclear cysteine protease separase causes female infertility because mutant oocytes are able neither to extrude polar bodies in meiosis I nor to resolve chiasmata ().

A deregulatory mutation into separin encoded by Espl1 at early embryonic period caused primordial germ cell depletion by apoptosis during embryonic oogenesis, which led to female infertility (, 107). The introduction of the same mutation at later oocyte development by using Zp3-cre also resulted in female infertility but because of failure in preimplantation development (108).

Matriptase encoded by Tmprss6 is a type II transmembrane serine protease which functions in iron homeostasis by cleaving cell surface proteins associated with iron absorption. Tmprss6-null females possessed marked retardation in ovarian maturation (), probably because of severe decrease in plasma iron levels. The defective ovarian follicle development and female infertility can be mimicked by a low iron diet (201).

The inter-α-trypsin inhibitor (IαI) family are abundantly found in body fluids including blood plasma and urine and possess inhibitory activity for serine proteases. They are composed of bikunin, a proteoglycan with a single chondroitin sulfate chain, and heavy chains covalently bound to chondroitin sulfate chain of bikunin. IαI family members are able to transfer their heavy chains from IαI to hyaluronan in the presence of tumor necrosis factor-stimulated gene-6. This reaction results in the modified hyaluronan covalently linked heavy chain and is necessary for hyaluronan-rich cumulus matrix expansion. When the bikunin-coding region was deleted from Ambp gene, the resulting homozygous females ovulate oocytes deficient in hyaluronan-rich cumulus matrix expansion, leading to female infertility (, ).

γ-secretase is an endoprotease complex that catalyzes the intramembrane cleavage of integral membrane proteins. Psen1 encodes presenillin-1, a catalytic subunit of γ-secretase. Female mice homozygous with a Leu166 to Pro mutation, an aggressive mutation found in familial Alzheimer’s disease patients, are infertile and their ovaries consisted largely of stromal elements with primordial follicles near the cortex ().

ADAMTS1 is a secreted metalloproteinase expressed in the granulosa cell layer of mature follicles in the ovary (). Adamts1-null females possessed lower numbers of mature follicles in the ovary and a thick and convoluted uterus (). In another mutant mouse line, ovulation in null females was impaired because mature oocytes remained trapped in ovarian follicles (). In zebrafish, adamts9-null females possess ovarian malformation and are unable to ovulate (123).

Lonp encodes a mitochondrial serine protease. Oocyte-specific Lonp ablation by Gdf9-cre or Zp3-cre; Lonp1fl/fl results in female infertility because of impaired follicular development, progressive oocyte death, ovarian reserve loss (). Furin encodes a transmembrane serine protease localized in Golgi appratus, endosome, plasma membrane; it is necessary for mature protein release by cleaving at RX(K/R)R consensus motif. Conditional ablation of Furin by Gdf9-cre or Zp3-cre; Furinfl/fl result in female infertility because of the arrested oogenesis at early secondary follicles (). Pappa encodes an extracellular metalloprotease. Pappa KO females decreased their litter size and ovulatory capacity, probably because of decreased bioavailability of ovarian insulin-like growth factor ().

Loss of GGT1 causes infertility in not only males but females. In the Ggt1-null females, antral follicles and corpora lutea were absent and follicles degenerated due to the reduced intracellular cysteine levels (117).

Mitochondrial proteases also affect ovarian follicle development. Ablation of Clpp encoding mitochondrial matrix ClpP protease caused relatively small ovaries in which follicular differentiation was impaired probably because of the reduction of the granulosa cell layers (114). When the inner mitochondrial membrane peptidase 2-like encoded by Immp2l was ablated, the resulting mutant females were deficient in folliculogenesis and ovulation and infertile, probably because of low availability of nitric oxide caused by mitochondrial dysfunction (118).

Proteolytic Factors in Post-Fertilization Events of Female Reproduction

Several proteolysis-associated secreted proteins contribute to post-fertilization events including the hardening of the egg-surrounding zona pellucida. Ovastacin encoded by Astl is a secreted metalloendopeptidase deposited in cortical granules of oocytes. Ovastatin is secreted into the extracellular space in response to egg activation triggered by fertilization. In Astl-null eggs, ZP2 cleavage necessary for zona pellucida hardening and the postfertilization block to polyspermy did not occur after fertilization (). Fetuin is a cystatin family protease inhibitor abundantly expressed in blood plasma. Fetuin-B prevents premature ZP hardening probably by inhibiting ovastacin derived from spontaneous cortical granule release, as fetuin-B inhibited ovastacin protease activity in vitro and Fetub-deficient oocytes undergo premature zona pellucida hardening ().

Antithrombin encoded by Serpinc1 inhibits thrombin and some other coagulation factors by binding heparin and heparan sulfate. When an Arg48 to Cys mutation, which corresponds to human thrombosis mutation, was introduced into mice, the resulting homozygous females had decreased their litter size, probably because thrombosis occurred in placenta ().

Adam10 encodes a membrane metalloprotease. Conditional ablation of vascular Adam10 by Tie2-Cre; Adam10fl/fl causes impaired decidualization and female subfertility (). Adamts18 encodes a member of secreted metalloprotease ADAMTS. Adamts18-null females suffer from vaginal obstruction, due to either a dorsoventral vaginal septum or imperforate vagina and infertility or subfertility ().

Other Proteolytic Factors in Female Reproduction

Several proteolysis-associated factors regulate female reproduction in a more indirect manner. Npepps-null females lacking a puromycin-sensitive aminopeptidase impairs corpus luteum formation and are infertile, probably because of disruption of the hypothalamic-pituitary axis (116). Plasmin is a secreted serine protease generated from plasminogen through activation by tissue-type or urokinase-type plasminogen activators. The fertility of plasmin-deficient Plg-null female mice appeared to be compromised (, ). It seems not to be the consequence of the impaired proteolytic process essential for ovulation, as plasminogen-deficient mice had normal ovulation efficiency (202). Timp1 encodes a tissue inhibitor of metalloproteinases 1, an inhibitor for matrix metalloproteinases. Timp1 mutation reduced the reproductive lifespan of female but not male mice (). When Pcsk2 encoding neuroendocrine convertase 2 was ablated, the number of consecutive litters from mutant female mice was small and Pcsk2-null female mice sometimes gave birth to dead pups () for uncertain reason. Conditional ablation of TNFα converting enzyme by Sox9-cre; Adam17fl/fl resulted in female infertility but details are uncertain (119).

Fertility-Associated Proteases in Plants

Several aspartic proteases are associated with pollen development and function. In Arabidopsis thaliana, A36 and A39 are GPI-anchored putative aspartic proteases predominantly expressed in pollen and the pollen tube. In a36; a39 double mutant, pollen grains underwent apoptosis-like programmed cell death and the pollen tube compromised micropylar guidance (126). UND encodes a secreted aspartic protease UNDEAD, and its silencing using small interfering RNA caused premature tapetal and pollen programmed cell death (128).

In Oryza sativa, OsAP65 encodes an aspartic protease localized in the pre-vacuolar compartment. T-DNA-inserted OsAP65 mutant alleles could not be transmitted through the male gamete; the mutant pollen matured normally, but did not germinate or elongate, indicating its essentiality in pollen germination and tube growth (131). PCS1 encodes an aspartic protease and its loss-of-function mutation caused degenerated male and female gametophytes (127).

A cysteine protease also contributes to pollen development; when a papain-like vacuolar cysteine protease encoded by CEP1 was ablated, the resulting mutants are male subfertile because of aborted tapetal programmed cell death and decreased pollen fertility with abnormal pollen exine (129).

Some aspect of A. thaliana reproduction includes Small Ubiquitin-related Modifier (SUMO). SPF1 and SPF2 are cysteine proteases and function in desumoylation of sumoylated proteins. spf1; spf2 double mutants exhibit severe abnormalities in microgametogenesis, megagametogenesis, and embryo development (130). There are SUMO-E3 ligases involved in gametophyte development (182, 183) in A. thaliana and in anther dehiscence in O. sativa (184).

Conclusion and Perspective

By a comprehensive survey, it has been demonstrated that proteolysis regulates reproduction in various species including yeast, insects, nematodes, vertebrates, and plants. Regulation of reproduction by proteolysis already exist in unicellular yeast. In multicellular organisms, proteolysis regulates the formation and function of gametes derived from germ cells as well as the development and function of reproductive organs by somatic cells, thereby securing successful reproduction. In these cell lineages, both limited proteolysis and degrative proteolysis by ubiquitin-proteasome system play critical roles.

One of intriguing paradigms emerging in this review is that many sperm surface and extracellular proteases, pseudoproteases, and inhibitors are included in the acquisition of mammalian sperm conferring abilities to migrate into the oviduct and to bind to the zona pellucida of eggs. As spermatozoa are transcriptionally and translationally silent, post-translational modification mechanisms such as proteolysis may largely contribute to sperm maturation.

Many compounds have been designed to inhibit the enzymatic activity of proteases. Clinically, there have been numerous successes including angiotensin-converting enzyme inhibitors for cardiovascular disorders (203), thrombin inhibitors for thromboembolism and bleeding disorders (204, 205), and HIV protease inhibitors in the treatment of HIV and AIDS (206), among others (207, 208). In addition, enzymatically active proteases could also be good druggable targets for contraceptives.

Genome editing techniques developed in recent years will identify fertility-associated proteolytic factors further. In addition to identifying novel factors, more intense studies on the molecular basis of proteolysis including the identification of substrates will clarify how proteolytic events govern reproduction. It will also clarify the physiological significance of molecular events governed by proteolysis in reproduction.

Funding

This work was supported in part by Ministry of Education, Culture, Sports, Science and Technology (MEXT)/Japan Society for the Promotion of Science (JSPS) KAKENHI grants (JP21H00231 to D.K. and JP21H05033 to MI), Japan Science and Technology Agency (21460710 to D.K. and 21467777 to MI), National Institutes of Health (R01HD088412 and P01HD087157 to MI), and the Bill & Melinda Gates Foundation (Grant INV-001902 to MI). Under the grant conditions of the Foundation, a Creative Commons Attribution 4.0 Generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission.

Publisher’s Note

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.

Statements

Author contributions

DK and MI wrote the manuscript. All authors contributed to the article and approved the submitted version.

Acknowledgments

We thank Dr Julio Castaneda for critical reading of this manuscript.

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.

Abbreviations

ACE, angiotensin converting enzyme; ADAM, a disintegrin-like and metalloproteinase domain; ADAMTS, a disintegrin-like and metalloproteinase domain with thrombospondin type 1 motif; CSN, constitutive photomorphogenic-9 signalosome; EMS, ethylmethane-sulfonate; GGT, glutamyltranspeptidase; IαI, inter-α-trypsin inhibitor; KI, knock-in; KO, knockout; OVCH2, ovochymase 2; S-Lap, sperm-Leucylaminopeptidase; SUMO, small ubiquitin-related modifier; TASP1, threonine aspartase 1; TMP,trimethylpsoralen; TNFα, tumor necrosis factor-α; UPS, ubiquitin-proteasome system; USP, ubiquitin-specific protease.

References

  • 1

    KahneDStillWC. Hydrolysis of a Peptide Bond in Neutral Water. J Am Chem Assoc (1988) 110(22):7529–34. doi: 10.1021/ja00230a041

  • 2

    CherryJMHongELAmundsenCBalakrishnanRBinkleyGChanETet al. Saccharomyces Genome Database: The Genomics Resource of Budding Yeast. Nucleic Acids Res (2012) 40(Database issue):D700–5. doi: 10.1093/nar/gkr1029

  • 3

    LarkinAMarygoldSJAntonazzoGAttrillHDos SantosGGarapatiPVet al. FlyBase: Updates to the Drosophila Melanogaster Knowledge Base. Nucleic Acids Res (2021) 49(D1):D899–907. doi: 10.1093/nar/gkaa1026

  • 4

    DavisPZarowieckiMArnaboldiVBecerraACainSChanJet al. WormBase in 2022-Data, Processes, and Tools for Analyzing Caenorhabditis Elegans. Genetics (2022) 220(4):iyac003. doi: 10.1093/genetics/iyac003

  • 5

    PuenteXSSanchezLMOverallCMLópez-OtinC. {H}uman and Mouse Proteases: A Comparative Genomic Approach. Nat Rev Genet (2003) 4(7):544–58. doi: 10.1038/nrg1111

  • 6

    García-LorenzoMSjödinAJanssonSFunkC. Protease Gene Families in Populus and Arabidopsis. BMC Plant Biol (2006) 6:30. doi: 10.1186/1471-2229-6-30

  • 7

    KleinTEckhardUDufourASolisNOverallCM. Proteolytic Cleavage - Mechanisms, Function, and “Omic” Approaches for a Near-Ubiquitous Posttranslational Modification. Chem Rev (2018) 118(3):1137–68. doi: 10.1021/acs.chemrev.7b00120

  • 8

    Fujimura-KamadaKNouvetFJMichaelisS. A Novel Membrane-Associated Metalloprotease, Ste24p, is Required for the First Step of NH2-Terminal Processing of the Yeast a-Factor Precursor. J Cell Biol (1997) 136(2):271–85. doi: 10.1083/jcb.136.2.271

  • 9

    AdamesNBlundellKAshbyMNBooneC. Role of Yeast Insulin-Degrading Enzyme Homologs in Propheromone Processing and Bud Site Selection. Sci (1995) 270(5235):464–7. doi: 10.1126/science.270.5235.464

  • 10

    HashmiSZhangJOksovYJiQLustigmanS. The Caenorhabditis Elegans CPI-2a Cystatin-Like Inhibitor has an Essential Regulatory Role During Oogenesis and Fertilization. J Biol Chem (2006) 281(38):28415–29. doi: 10.1074/jbc.M600254200

  • 11

    BlellochRKimbleJ. Control of Organ Shape by a Secreted Metalloprotease in the Nematode Caenorhabditis Elegans. Nat (1999) 399(6736):586–90. doi: 10.1038/21196

  • 12

    BlellochRAnna-ArriolaSSGaoDLiYHodgkinJKimbleJ. The Gon-1 Gene is Required for Gonadal Morphogenesis in Caenorhabditis Elegans. Dev Biol (1999) 216(1):382–93. doi: 10.1006/dbio.1999.9491

  • 13

    KubotaYNishiwakiKItoMSugimotoA. The Role of Tissue Inhibitors of Metalloproteinases in Organ Development and Regulation of ADAMTS Family Metalloproteinases in Caenorhabditis Elegans. Genetics (2019) 212(2):523–35. doi: 10.1534/genetics.119.301795

  • 14

    PispaJPalménSHolmbergCIJänttiJC. Elegans Dss-1 is Functionally Conserved and Required for Oogenesis and Larval Growth. BMC Dev Biol (2008) 8:51. doi: 10.1186/1471-213X-8-51

  • 15

    GudipatiRKBraunKGypasFHessDSchreierJCarlSHet al. Protease-Mediated Processing of Argonaute Proteins Controls Small RNA Association. Mol Cell (2021) 81(11):23882402.e8. doi: 10.1016/j.molcel.2021.03.029

  • 16

    JarriaultSGreenwaldI. Evidence for Functional Redundancy Between C. Elegans ADAM Proteins SUP-17/Kuzbanian and ADM-4/TACE. Dev Biol (2005) 287(1):110. doi: 10.1016/j.ydbio.2005.08.014

  • 17

    AlthoffMJFlickKTrzepaczC. Collaboration Within the M1 Aminopeptidase Family Promotes Reproductive Success in Caenorhabditis Elegans. Dev Genes Evol (2014) 224(3):137–46. doi: 10.1007/s00427-014-0470-3

  • 18

    SmithJRStanfieldGM. TRY-5 is a Sperm-Activating Protease in Caenorhabditis Elegans Seminal Fluid. PloS Genet (2011) 7(11):e1002375. doi: 10.1371/journal.pgen.1002375

  • 19

    StanfieldGMVilleneuveAM. Regulation of Sperm Activation by SWM-1 is Required for Reproductive Success of C Elegans Males. Curr Biol (2006) 16(3):252–63. doi: 10.1016/j.cub.2005.12.041

  • 20

    BhargavaVGoldsteinCDRussellLXuLAhmedMLiWet al. GCNA Preserves Genome Integrity and Fertility Across Species. Dev Cell (2020) 52(1):3852.e10. doi: 10.1016/j.devcel.2019.11.007

  • 21

    AltincicekBFischerMFischerMLüersenKBollMWenzelUet al. Role of Matrix Metalloproteinase ZMP-2 in Pathogen Resistance and Development in Caenorhabditis Elegans. Dev Comp Immunol (2010) 34(11):1160–9. doi: 10.1016/j.dci.2010.06.010

  • 22

    AdolphsenKAmellAHavkoNKevorkianSMearsKNeherHet al. Type-I Prenyl Protease Function is Required in the Male Germline of Drosophila Melanogaster. G3 (Bethesda) (2012) 2(6):629–42. doi: 10.1534/g3.112.002188

  • 23

    ZhongLBeloteJM. The Testis-Specific Proteasome Subunit Prosalpha6T of D. Melanogaster is Required for Individualization and Nuclear Maturation During Spermatogenesis. Development (2007) 134(19):3517–25. doi: 10.1242/dev.004770

  • 24

    KoerverLMelzerJRocaEATeichertDGlatterTAramaEet al. The De-Ubiquitylating Enzyme DUBA is Essential for Spermatogenesis in Drosophila. Cell Death Differ (2016) 23(12):2019–30. doi: 10.1038/cdd.2016.79

  • 25

    HuhJRVernooySYYuHYanNShiYGuoMet al. Multiple Apoptotic Caspase Cascades are Required in Nonapoptotic Roles for Drosophila Spermatid Individualization. PloS Biol (2004) 2(1):E15. doi: 10.1371/journal.pbio.0020015

  • 26

    TainLSChowdhuryRBTaoRNPlun-FavreauHMoisoiNMartinsLMet al. Drosophila HtrA2 is Dispensable for Apoptosis But Acts Downstream of PINK1 Independently From Parkin. Cell Death Differ (2009) 16(8):1118–25. doi: 10.1038/cdd.2009.23

  • 27

    YunJCaoJHDodsonMWClarkIEKapahiPChowdhuryRBet al. Loss-Of-Function Analysis Suggests That Omi/HtrA2 is Not an Essential Component of the PINK1/PARKIN Pathway In Vivo. J Neurosci (2008) 28(53):14500–10. doi: 10.1523/JNEUROSCI.5141-08.2008

  • 28

    LaurinyeczBVedelekVKovácsALSzilasiKLipinszkiZSlezákCet al. Sperm-Leucylaminopeptidases are Required for Male Fertility as Structural Components of Mitochondrial Paracrystalline Material in Drosophila Melanogaster Sperm. PloS Genet (2019) 15(2):e1007987. doi: 10.1371/journal.pgen.1007987

  • 29

    LaFlammeBARamKRWolfnerMF. The Drosophila Melanogaster Seminal Fluid Protease “Seminase” Regulates Proteolytic and Post-Mating Reproductive Processes. PloS Genet (2012) 8(1):e1002435. doi: 10.1371/journal.pgen.1002435

  • 30

    OhsakoTShirakamiMOiwaKIbarakiKKarrTLTomaruMet al. The Drosophila Neprilysin 4 Gene Is Essential for Sperm Function Following Sperm Transfer to Females. Genes Genet Syst (2021) 96(4):177–86. doi: 10.1266/ggs.21-00024

  • 31

    McCallKStellerH. Requirement for DCP-1 Caspase During Drosophila Oogenesis. Sci (1998) 279(5348):230–4. doi: 10.1126/science.279.5348.230

  • 32

    LoppinBBergerFCoubleP. Paternal Chromosome Incorporation Into the Zygote Nucleus is Controlled by Maternal Haploid in Drosophila. Dev Biol (2001) 231(2):383–96. doi: 10.1006/dbio.2000.0152

  • 33

    DelabaereLOrsiGASapey-TriompheLHorardBCoublePLoppinB. The Spartan Ortholog Maternal Haploid Is Required for Paternal Chromosome Integrity in the Drosophila Zygote. Curr Biol (2014) 24(19):2281–7. doi: 10.1016/j.cub.2014.08.010

  • 34

    TateiKCaiHIpYTLevineM. Race: A Drosophila Homologue of the Angiotensin Converting Enzyme. Mech Dev (1995) 51(2–3):157–68. doi: 10.1016/0925-4773(95)00349-5

  • 35

    ChenSYangHKrinskyBHZhangALongM. Roles of Young Serine-Endopeptidase Genes in Survival and Reproduction Revealed Rapid Evolution of Phenotypic Effects at Adult Stages. Fly (Austin) (2011) 5(4):345–51. doi: 10.4161/fly.5.4.17808

  • 36

    ChiharaCJSongCLaMonteGFetalveroKHinchmanKPhanHet al. Identification and Partial Characterization of the Enzyme of Omega: One of Five Putative DPP IV Genes in Drosophila Melanogaster. J Insect Sci (2005) 5:26. doi: 10.1093/jis/5.1.26

  • 37

    DeadyLDShenWMosureSASpradlingACSunJ. Matrix Metalloproteinase 2 Is Required for Ovulation and Corpus Luteum Formation in Drosophila. PloS Genet (2015) 11(2):e1004989. doi: 10.1371/journal.pgen.1004989

  • 38

    MarshallJLHuestisDLHiromasaYWheelerSOppertCMarshallSAet al. Identification, RNAi Knockdown, and Functional Analysis of an Ejaculate Protein That Mediates a Postmating, Prezygotic Phenotype in a Cricket. PloS One (2009) 4(10):e7537. doi: 10.1371/journal.pone.0007537

  • 39

    XuXBiHWangYLiXXuJLiuZet al. Disruption of the Ovarian Serine Protease (Osp) Gene Causes Female Sterility in Bombyx Mori and Spodoptera Litura. Pest Manag Sci (2020) 76(4):1245–55. doi: 10.1002/ps.5634

  • 40

    XuXWangYBiHXuJLiuZNiuCet al. Mutation of the Seminal Protease Gene, Serine Protease 2, Results in Male Sterility in Diverse Lepidopterans. Insect Biochem Mol Biol (2020) 116:103243. doi: 10.1016/j.ibmb.2019.103243

  • 41

    LiXLiuQBiHWangYXuXSunWet al. Piggybac-Based Transgenic RNAi of Serine Protease 2 Results in Male Sterility in Hyphantria Cunea. Insect Biochem Mol Biol (2022) 143:103726. doi: 10.1016/j.ibmb.2022.103726

  • 42

    LiuGLvZWuQZhouZZhangGWanFet al. The Bactrocera Dorsalis Caspase-1 Gene is Expressed Throughout Development and Required for Female Fertility. Pest Manag Sci (2020) 76(12):4104–11. doi: 10.1002/ps.5966

  • 43

    ZhangQJiS-YBusayavalasaKShaoJYuC. Meiosis I Progression in Spermatogenesis Requires a Type of Testis-Specific 20S Core Proteasome. Nat Commun (2019) 10(1):3387. doi: 10.1038/s41467-019-11346-y

  • 44

    GaoXChenHLiuJShenSWangQClementTMet al. The Regγ-Proteasome Regulates Spermatogenesis Partially by P53-PLZF Signaling. Stem Cell Rep (2019) 13(3):559–71. doi: 10.1016/j.stemcr.2019.07.010

  • 45

    KhorBBredemeyerALHuangC-YTurnbullIREvansRMaggiLBet al. Proteasome Activator PA200 is Required for Normal Spermatogenesis. Mol Cell Biol (2006) 26(8):29993007. doi: 10.1128/MCB.26.8.2999-3007.2006

  • 46

    HuangLHaratakeKMiyaharaHChibaT. Proteasome Activators, PA28γ and PA200, Play Indispensable Roles in Male Fertility. Sci Rep (2016) 6:23171. doi: 10.1038/srep23171

  • 47

    HuangQLiuHZengJLiWZhangSZhangLet al. COP9 Signalosome Complex Subunit 5, an IFT20 Binding Partner, is Essential to Maintain Male Germ Cell Survival and Acrosome Biogenesis†. Biol Reprod (2020) 102(1):233–47. doi: 10.1093/biolre/ioz154

  • 48

    BedardNYangYGregoryMCyrDGSuzukiJYuXet al. Mice Lacking the USP2 Deubiquitinating Enzyme Have Severe Male Subfertility Associated With Defects in Fertilization and Sperm Motility. Biol Reprod (2011) 85(3):594604. doi: 10.1095/biolreprod.110.088542

  • 49

    KishiKUchidaATakaseHMSuzukiHKurohmaruMTsunekawaNet al. Spermatogonial Deubiquitinase USP9X Is Essential for Proper Spermatogenesis in Mice. Reproduction (2017) 154(2):135–43. doi: 10.1530/REP-17-0184

  • 50

    TianHHuoYZhangJDingSWangZLiHet al. Disruption of Ubiquitin Specific Protease 26 Gene Causes Male Subfertility Associated With Spermatogenesis Defects in Mice†. Biol Reprod (2019) 100(4):1118–28. doi: 10.1093/biolre/ioy258

  • 51

    SakaiKItoCWakabayashiMKanzakiSItoTTakadaSet al. Usp26 Mutation in Mice Leads to Defective Spermatogenesis Depending on Genetic Background. Sci Rep (2019) 9(1):13757. doi: 10.1038/s41598-019-50318-6

  • 52

    KimJMParmarKHuangMWeinstockDMRuitCAKutokJLet al. Inactivation of Murine Usp1 Results in Genomic Instability and a Fanconi Anemia Phenotype. Dev Cell (2009) 16(2):314–20. doi: 10.1016/j.devcel.2009.01.001

  • 53

    HonarpourNDuCRichardsonJAHammerREWangXHerzJ. Adult Apaf-1-Deficient Mice Exhibit Male Infertility. Dev Biol (2000) 218(2):248–58. doi: 10.1006/dbio.1999.9585

  • 54

    WuH-YWeiPMorganJI. Role of Cytosolic Carboxypeptidase 5 in Neuronal Survival and Spermatogenesis. Sci Rep (2017) 7:41428. doi: 10.1038/srep41428

  • 55

    GiordanoTGadadharSBodakuntlaSStraubJLeboucherSMartinezGet al. Loss of the Deglutamylase CCP5 Perturbs Multiple Steps of Spermatogenesis and Leads to Male Infertility. J Cell Sci (2019) 132(3):jcs226951. doi: 10.1242/jcs.226951

  • 56

    CarmellMADokshinGASkaletskyHHuY-Cvan WolfswinkelJCIgarashiKJet al. A Widely Employed Germ Cell Marker is an Ancient Disordered Protein With Reproductive Functions in Diverse Eukaryotes. Elife (2016) 5:e19993. doi: 10.7554/eLife.19993

  • 57

    OyamaTSasagawaSTakedaSHessRALiebermanPMChengEHet al. Cleavage of TFIIA by Taspase1 Activates TRF2-Specified Mammalian Male Germ Cell Programs. Dev Cell (2013) 27(2):188200. doi: 10.1016/j.devcel.2013.09.025

  • 58

    MizunoYNinomiyaYNakachiYIsekiMIwasaHAkitaMet al. Tysnd1 Deficiency in Mice Interferes With the Peroxisomal Localization of PTS2 Enzymes, Causing Lipid Metabolic Abnormalities and Male Infertility. PloS Genet (2013) 9(2):e1003286. doi: 10.1371/journal.pgen.1003286

  • 59

    KherrafZ-EChristou-KentMKaraouzeneTAmiri-YektaAMartinezGVargasASet al. SPINK2 Deficiency Causes Infertility by Inducing Sperm Defects in Heterozygotes and Azoospermia in Homozygotes. EMBO Mol Med (2017) 9(8):1132–49. doi: 10.15252/emmm.201607461

  • 60

    UhrinPDewerchinMHilpertMChrenekPSchöferCZechmeister-MachhartMet al. Disruption of the Protein C Inhibitor Gene Results in Impaired Spermatogenesis and Male Infertility. J Clin Invest (2000) 106(12):1531–9. doi: 10.1172/JCI10768

  • 61

    LiS-WWAritaMFertalaABaoYKopenGCLångsjöTKet al. Transgenic Mice With Inactive Alleles for Procollagen N-Proteinase (ADAMTS-2) Develop Fragile Skin and Male Sterility. Biochem J (2001) 355(2):271–8. doi: 10.1042/bj3550271

  • 62

    BabaTAzumaSKashiwabaraSToyodaY. Sperm From Mice Carrying a Targeted Mutation of the Acrosin Gene can Penetrate the Oocyte Zona Pellucida and Effect Fertilization. J Biol Chem (1994) 269(50):31845–9. doi: 10.1016/S0021-9258(18)31772-1

  • 63

    AdhamIMNayerniaKEngelW. Spermatozoa Lacking Acrosin Protein Show Delayed Fertilization. Mol Reprod Dev (1997) 46(3):370–6. doi: 10.1002/(SICI)1098-2795(199703)46:3<370::AID-MRD16>3.0.CO;2-2

  • 64

    Gyamera-AcheampongCTantibhedhyangkulJWeerachatyanukulWTadrosHXuHvan de LooJ-Wet al. Sperm From Mice Genetically Deficient for the PCSK4 Proteinase Exhibit Accelerated Capacitation, Precocious Acrosome Reaction, Reduced Binding to Egg Zona Pellucida, and Impaired Fertilizing Ability. Biol Reprod (2006) 74(4):666–73. doi: 10.1095/biolreprod.105.046821

  • 65

    MbikayMTadrosHIshidaNLernerCPDe LamirandeEChenAet al. Impaired Fertility in Mice Deficient for the Testicular Germ-Cell Protease PC4. Proc Natl Acad Sci USA (1997) 94(13):6842–6. doi: 10.1073/pnas.94.13.6842

  • 66

    LarasatiTNodaTFujiharaYShimadaKTobitaTYuZet al. Tmprss12 is Required for Sperm Motility and Uterotubal Junction Migration in Mice†. Biol Reprod (2020) 103(2):254–63. doi: 10.1093/biolre/ioaa060

  • 67

    ShangXShenCLiuJTangLZhangHWangYet al. Serine Protease PRSS55 is Crucial for Male Mouse Fertility via Affecting Sperm Migration and Sperm-Egg Binding. Cell Mol Life Sci (2018) 75(23):4371–84. doi: 10.1007/s00018-018-2878-9

  • 68

    KobayashiKEndoTMatsumuraTLuYYuZMatzukMMet al. Prss55 But Not Prss51 is Required for Male Fertility in Mice†. Biol Reprod (2020) 103(2):223–34. doi: 10.1093/biolre/ioaa041

  • 69

    ZhangHLiYCuiKChenXShangCMinWet al. Male Fertility in Mus Musculus Requires the Activity of TRYX5 in Sperm Migration Into the Oviduct. J Cell Physiol (2020) 235(9):6058–72. doi: 10.1002/jcp.29534

  • 70

    ShenCKuangYLiuJFengJChenXWuWet al. Prss37 is Required for Male Fertility in the Mouse. Biol Reprod (2013) 88(5):123, 1–11. doi: 10.1095/biolreprod.112.107086

  • 71

    EstherCRHowardTEMarinoEMGoddardJMCapecchiMRBernsteinKE. Mice Lacking Angiotensin-Converting Enzyme Have Low Blood Pressure, Renal Pathology, and Reduced Male Fertility. Lab Invest (1996) 74(5):953–65.

  • 72

    NishimuraHKimENakanishiTBabaT. Possible Function of the ADAM1a/ADAM2 Fertilin Complex in the Appearance of ADAM3 on the Sperm Surface. J Biol Chem (2004) 279(33):34957–62. doi: 10.1074/jbc.M314249200

  • 73

    ChoCBunchDODFaureJEGouldingEHEddyEMPrimakoffPet al. Fertilization Defects in Sperm From Mice Lacking Fertilin β. Sci (80-) (1998) 281(5384):1857–9. doi: 10.1126/science.281.5384.1857

  • 74

    NishimuraHChoCBranciforteDRMylesDGPrimakoffP. Analysis of Loss of Adhesive Function in Sperm Lacking Cyritestin or Fertilin Beta. Dev Biol (2001) 233(1):204–13. doi: 10.1006/dbio.2001.0166

  • 75

    YamaguchiRMuroYIsotaniATokuhiroKTakumiKAdhamIet al. Disruption of ADAM3 Impairs the Migration of Sperm Into Oviduct in Mouse. Biol Reprod (2009) 81(1):142–6. doi: 10.1095/biolreprod.108.074021

  • 76

    VoroninaVAHarrisFMSchmahlJGalliganCOristianDZamfirovaRet al. Deletion of Adam6 in Mus Musculus Leads to Male Subfertility and Deficits in Sperm Ascent Into the Oviduct. Biol Reprod (2019) 100(3):686–96. doi: 10.1093/biolre/ioy210

  • 77

    FujiharaYNodaTKobayashiKOjiAKobayashiSMatsumuraTet al. Identification of Multiple Male Reproductive Tractspecific Proteins That Regulate Sperm Migration Through the Oviduct in Mice. Proc Natl Acad Sci USA (2019) 116(37):18498–506. doi: 10.1073/pnas.1908736116

  • 78

    KiyozumiDNodaTYamaguchiRTobitaTMatsumuraTShimadaKet al. NELL2-Mediated Lumicrine Signaling Through OVCH2 is Required for Male Fertility. Sci (80-) (2020) 368(6495):1132–5. doi: 10.1126/science.aay5134

  • 79

    CarpentierMGuillemetteCBaileyJLBoileauGJeannotteLDesGroseillersLet al. Reduced Fertility in Male Mice Deficient in the Zinc Metallopeptidase NL1. Mol Cell Biol (2004) 24(10):4428–37. doi: 10.1128/MCB.24.10.4428-4437.2004

  • 80

    Netzel-ArnettSBuggeTHHessRACarnesKStringerBWScarmanALet al. The Glycosylphosphatidylinositol-Anchored Serine Protease PRSS21 (Testisin) Imparts Murine Epididymal Sperm Cell Maturation and Fertilizing Ability. Biol Reprod (2009) 81(5):921–32. doi: 10.1095/biolreprod.109.076273

  • 81

    YamashitaMHondaAOguraAKashiwabaraSFukamiKBabaT. Reduced Fertility of Mouse Epididymal Sperm Lacking Prss21/Tesp5 is Rescued by Sperm Exposure to Uterine Microenvironment. Genes Cells (2008) 13(10):1001–13. doi: 10.1111/j.1365-2443.2008.01222.x

  • 82

    SrinivasanSBunchDOFengYRodriguizRMLiMRavenellRLet al. Deficits in Reproduction and Pro-Gonadotropin-Releasing Hormone Processing in Male Cpefat Mice. Endocrinol (2004) 145(4):2023–34. doi: 10.1210/en.2003-1442

  • 83

    ZhuG-ZGuptaSMylesDGPrimakoffP. Testase 1 (ADAM 24) a Sperm Surface Metalloprotease is Required for Normal Fertility in Mice. Mol Reprod Dev (2009) 76(11):1106–14. doi: 10.1002/mrd.21076

  • 84

    ChoiHHanCJinSKwonJTKimJJeongJet al. Reduced Fertility and Altered Epididymal and Sperm Integrity in Mice Lacking Adam7. Biol Reprod (2015) 93(3):70. doi: 10.1095/biolreprod.115.130252

  • 85

    WhellySSerobianGBorchardtCPowellJJohnsonSHakanssonKet al. Fertility Defects in Mice Expressing the L68Q Variant of Human Cystatin C: A Role for Amyloid in Male Infertility. J Biol Chem (2014) 289(11):7718–29. doi: 10.1074/jbc.M113.515759

  • 86

    MurerVSpetzJFHengstUAltroggeLMde AgostiniAMonardD. Male Fertility Defects in Mice Lacking the Serine Protease Inhibitor Protease Nexin-1. Proc Natl Acad Sci USA (2001) 98(6):3029–33. doi: 10.1073/pnas.051630698

  • 87

    FolguerasARde LaraFMPendásAMGarabayaCRodríguezFAstudilloAet al. Membrane-Bound Serine Protease Matriptase-2 (Tmprss6) Is an Essential Regulator of Iron Homeostasis. Blood (2008) 112(6):2539–45. doi: 10.1182/blood-2008-04-149773

  • 88

    SatoHKajikawaSKurodaSHorisawaYNakamuraNKagaNet al. Impaired Fertility in Female Mice Lacking Urinary Trypsin Inhibitor. Biochem Biophys Res Commun (2001) 281(5):1154–60. doi: 10.1006/bbrc.2001.4475

  • 89

    ZhuoLYonedaMZhaoMYingsungWYoshidaNKitagawaYet al. Defect in SHAP-Hyaluronan Complex Causes Severe Female Infertility. A Study by Inactivation of the Bikunin Gene in Mice. J Biol Chem (2001) 276(11):7693–6. doi: 10.1074/jbc.C000899200

  • 90

    VidalRSammetaNGarringerHJSambamurtiKMiravalleLLambBTet al. The Psen1-L166P-Knock-in Mutation Leads to Amyloid Deposition in Human Wild-Type Amyloid Precursor Protein YAC Transgenic Mice. FASEB J (2012) 26(7):2899–910. doi: 10.1096/fj.12-205542

  • 91

    MittazLRussellDLWilsonTBrastedMTkalcevicJSalamonsenLAet al. Adamts-1 is Essential for the Development and Function of the Urogenital System. Biol Reprod (2004) 70(4):1096–105. doi: 10.1095/biolreprod.103.023911

  • 92

    ShindoTKuriharaHKunoKYokoyamaHWadaTKuriharaYet al. ADAMTS-1: A Metalloproteinase-Disintegrin Essential for Normal Growth, Fertility, and Organ Morphology and Function. J Clin Invest (2000) 105(10):1345–52. doi: 10.1172/JCI8635

  • 93

    ShengXLiuCYanGLiGLiuJYangYet al. The Mitochondrial Protease LONP1 Maintains Oocyte Development and Survival by Suppressing Nuclear Translocation of AIFM1 in Mammals. EBioMedicine (2022) 75:103790. doi: 10.1016/j.ebiom.2021.103790

  • 94

    MengT-GHuM-WMaX-SHuangLLiangQ-XYuanYet al. Oocyte-Specific Deletion of Furin Leads to Female Infertility by Causing Early Secondary Follicle Arrest in Mice. Cell Death Dis (2017) 8(6):e2846. doi: 10.1038/cddis.2017.231

  • 95

    NyegaardMOvergaardMTSuY-QHamiltonAEKwintkiewiczJHsiehMet al. Lack of Functional Pregnancy-Associated Plasma Protein-A (PAPPA) Compromises Mouse Ovarian Steroidogenesis and Female Fertility. Biol Reprod (2010) 82(6):1129–38. doi: 10.1095/biolreprod.109.079517

  • 96

    BurkartADXiongBBaibakovBJiménez-MovillaMDeanJ. Ovastacin, a Cortical Granule Protease, Cleaves ZP2 in the Zona Pellucida to Prevent Polyspermy. J Cell Biol (2012) 197(1):3744. doi: 10.1083/jcb.201112094

  • 97

    DietzelEWesslingJFloehrJSchäferCEnsslenSDeneckeBet al. Fetuin-B, a Liver-Derived Plasma Protein is Essential for Fertilization. Dev Cell (2013) 25(1):106–12. doi: 10.1016/j.devcel.2013.03.001

  • 98

    DewerchinMHéraultJ-PWallaysGPetitouMSchaefferPMilletLet al. Life-Threatening Thrombosis in Mice With Targeted Arg48-To-Cys Mutation of the Heparin-Binding Domain of Antithrombin. Circ Res (2003) 93(11):1120–6. doi: 10.1161/01.RES.0000103634.69868.4F

  • 99

    Lustgarten GuahmichNFarberGShafieiSMcNallyDRedmondDKallinosEet al. Endothelial Deletion of ADAM10, A Key Regulator of Notch Signaling, Causes Impaired Decidualization and Reduced Fertility in Female Mice. Angiogenesis (2020) 23(3):443–58. doi: 10.1007/s10456-020-09723-z

  • 100

    AtacaDCaikovskiMPiersigilliAMoulinABenarafaCEarpSEet al. Adamts18 Deletion Results in Distinct Developmental Defects and Provides a Model for Congenital Disorders of Lens, Lung, and Female Reproductive Tract Development. Biol Open (2016) 5(11):1585–94. doi: 10.1242/bio.019711

  • 101

    PloplisVACarmelietPVazirzadehSVan VlaenderenIMoonsLPlowEFet al. Effects of Disruption of the Plasminogen Gene on Thrombosis, Growth, and Health in Mice. Circulation (1995) 92(9):2585–93. doi: 10.1161/01.CIR.92.9.2585

  • 102

    LundLRBjørnSFSternlichtMDNielsenBSSolbergHUsherPAet al. Lactational Competence and Involution of the Mouse Mammary Gland Require Plasminogen. Development (2000) 127(20):4481–92. doi: 10.1242/dev.127.20.4481

  • 103

    NothnickWB. Reduction in Reproductive Lifespan of Tissue Inhibitor of Metalloproteinase 1 (TIMP-1)-Deficient Female Mice. Reproduction (2001) 122(6):923–7. doi: 10.1530/rep.0.1220923

  • 104

    FurutaMYanoHZhouARouilléYHolstJJCarrollRet al. Defective Prohormone Processing and Altered Pancreatic Islet Morphology in Mice Lacking Active SPC2. Proc Natl Acad Sci USA (1997) 2494(13):6646–51. doi: 10.1073/pnas.94.13.6646

  • 105

    HuangXAndreu-VieyraCVYorkJPHatcherRLuTMatzukMMet al. Inhibitory Phosphorylation of Separase is Essential for Genome Stability and Viability of Murine Embryonic Germ Cells. PloS Biol (2008) 6(1):e15. doi: 10.1371/journal.pbio.0060015

  • 106

    KudoNRWassmannKAngerMSchuhMWirthKGXuHet al. Resolution of Chiasmata in Oocytes Requires Separase-Mediated Proteolysis. Cell (2006) 126(1):135–46. doi: 10.1016/j.cell.2006.05.033

  • 107

    XuJWangMGaoXHuBDuYZhouJet al. Separase Phosphosite Mutation Leads to Genome Instability and Primordial Germ Cell Depletion During Oogenesis. PloS One (2011) 6(4):e18763. doi: 10.1371/journal.pone.0018763

  • 108

    HuangXAndreu-VieyraCVWangMCooneyAJMatzukMMZhangP. Preimplantation Mouse Embryos Depend on Inhibitory Phosphorylation of Separase to Prevent Chromosome Missegregation. Mol Cell Biol (2009) 29(6):1498–505. doi: 10.1128/MCB.01778-08

  • 109

    MullenRJEicherEMSidmanRL. Purkinje Cell Degeneration, a New Neurological Mutation in the Mouse. Proc Natl Acad Sci (1976) 73(1):208–12. doi: 10.1073/pnas.73.1.208

  • 110

    KrulewskiTFNeumannPEGordonJW. Insertional Mutation in a Transgenic Mouse Allelic With Purkinje Cell Degeneration. Proc Natl Acad Sci USA (1989) 86(10):3709–12. doi: 10.1073/pnas.86.10.3709

  • 111

    Fernandez-GonzalezALa SpadaARTreadawayJHigdonJCHarrisBSSidmanRLet al. Purkinje Cell Degeneration (Pcd) Phenotypes Caused by Mutations in the Axotomy-Induced Gene, Nna1. Sci (2002) 295(5561):1904–6. doi: 10.1126/science.1068912

  • 112

    ChakrabartiLNealJTMilesMMartinezRASmithACSopherBLet al. The Purkinje Cell Degeneration 5J Mutation is a Single Amino Acid Insertion That Destabilizes Nna1 Protein. Mamm Genome (2006) 17(2):103–10. doi: 10.1007/s00335-005-0096-x

  • 113

    SongNKimNXiaoRChoiHChunH-IKangM-Het al. Lack of Cytosolic Carboxypeptidase 1 Leads to Subfertility Due to the Reduced Number of Antral Follicles in Pcd3j-/- Females. PloS One (2015) 10(10):e0139557. doi: 10.1371/journal.pone.0139557

  • 114

    GispertSParganlijaDKlinkenbergMDröseSWittigIMittelbronnMet al. Loss of Mitochondrial Peptidase Clpp Leads to Infertility, Hearing Loss Plus Growth Retardation via Accumulation of CLPX, mtDNA and Inflammatory Factors. Hum Mol Genet (2013) 22(24):4871–87. doi: 10.1093/hmg/ddt338

  • 115

    OsadaTWatanabeGKondoSToyodaMSakakiYTakeuchiT. Male Reproductive Defects Caused by Puromycin-Sensitive Aminopeptidase Deficiency in Mice. Mol Endocrinol (2001) 15(6):960–71. doi: 10.1210/mend.15.6.0643

  • 116

    OsadaTWatanabeGSakakiYTakeuchiT. Puromycin-Sensitive Aminopeptidase is Essential for the Maternal Recognition of Pregnancy in Mice. Mol Endocrinol (2001) 15(6):882–93. doi: 10.1210/mend.15.6.0644

  • 117

    KumarTRWisemanALKalaGKalaSVMatzukMMLiebermanMW. Reproductive Defects in Gamma-Glutamyl Transpeptidase-Deficient Mice. Endocrinol (2000) 141(11):4270–7. doi: 10.1210/endo.141.11.7760

  • 118

    LuBPoirierCGasparTGratzkeCHarrisonWBusijaDet al. A Mutation in the Inner Mitochondrial Membrane Peptidase 2-Like Gene (Immp2l) Affects Mitochondrial Function and Impairs Fertility in Mice. Biol Reprod (2008) 78(4):601–10. doi: 10.1095/biolreprod.107.065987

  • 119

    HoriuchiKKimuraTMiyamotoTMiyamotoKAkiyamaHTakaishiHet al. Conditional Inactivation of TACE by a Sox9 Promoter Leads to Osteoporosis and Increased Granulopoiesis via Dysregulation of IL-17 and G-CSF. J Immunol (2009) 182(4):2093–101. doi: 10.4049/jimmunol.0802491

  • 120

    HiroseMHondaAFulkaHTamura-NakanoMMatobaSTomishimaTet al. Acrosin is Essential for Sperm Penetration Through the Zona Pellucida in Hamsters. Proc Natl Acad Sci USA (2020) 117(5):2513–8. doi: 10.1073/pnas.1917595117

  • 121

    Abdul-MajeedSMellBNauliSMJoeB. Cryptorchidism and Infertility in Rats With Targeted Disruption of the Adamts16 Locus. PloS One (2014) 9(7):e100967. doi: 10.1371/journal.pone.0100967

  • 122

    SarilaGBaoTAbeydeeraSALiRMellBJoeBet al. Interplay Between Collagenase and Undescended Testes in Adamts16 Knockout Rats. J Pediatr Surg (2020) 55(9):1952–8. doi: 10.1016/j.jpedsurg.2019.12.019

  • 123

    CarterNJRoachZAByrnesMMZhuY. Adamts9 is Necessary for Ovarian Development in Zebrafish. Gen Comp Endocrinol (2019) 277(March):130–40. doi: 10.1016/j.ygcen.2019.04.003

  • 124

    ArafatMKleimanSEAbuMadighemAZeadnaALevitasEVardiIHet al. Pathogenic Variations in Germ Cell Nuclear Acidic Peptidase (GCNA) are Associated With Human Male Infertility. Eur J Hum Genet (2021) 29(12):1781–8. doi: 10.1038/s41431-021-00946-2

  • 125

    HardyJJWyrwollMJMcfaddenWMalcherARotteNPollockNCet al. Variants in GCNA, X-Linked Germ-Cell Genome Integrity Gene, Identified in Men With Primary Spermatogenic Failure. Hum Genet (2021) 140(8):1169–82. doi: 10.1007/s00439-021-02287-y

  • 126

    GaoHZhangYWangWZhaoKLiuCBaiLet al. Two Membrane-Anchored Aspartic Proteases Contribute to Pollen and Ovule Development. Plant Physiol (2017) 173(1):219–39. doi: 10.1104/pp.16.01719

  • 127

    GeXDietrichCMatsunoMLiGBergHXiaY. An Arabidopsis Aspartic Protease Functions as an Anti-Cell-Death Component in Reproduction and Embryogenesis. EMBO Rep (2005) 6(3):282–8. doi: 10.1038/sj.embor.7400357

  • 128

    PhanHAIacuoneSLiSFParishRW. The MYB80 Transcription Factor is Required for Pollen Development and the Regulation of Tapetal Programmed Cell Death in Arabidopsis Thaliana. Plant Cell (2011) 23(6):2209–24. doi: 10.1105/tpc.110.082651

  • 129

    ZhangDLiuDLvXWangYXunZLiuZet al. The Cysteine Protease CEP1, a Key Executor Involved in Tapetal Programmed Cell Death, Regulates Pollen Development in Arabidopsis. Plant Cell (2014) 26(7):2939–61. doi: 10.1105/tpc.114.127282

  • 130

    LiuLJiangYZhangXWangXWangYHanYet al. Two SUMO Proteases SUMO PROTEASE RELATED TO FERTILITY1 and 2 Are Required for Fertility in Arabidopsis. Plant Physiol (2017) 175(4):1703–19. doi: 10.1104/pp.17.00021

  • 131

    HuangJZhaoXChengKJiangYOuyangYXuCet al. OsAP65, a Rice Aspartic Protease, is Essential for Male Fertility and Plays a Role in Pollen Germination and Pollen Tube Growth. J Exp Bot (2013) 64(11):3351–60. doi: 10.1093/jxb/ert173

  • 132

    ThalerCDMiyataHHaimoLTCardulloRA. Waveform Generation is Controlled by Phosphorylation and Swimming Direction Is Controlled by Ca2+ in Sperm From the Mosquito Culex Quinquefasciatus. Biol Reprod (2013) 89(6):135. doi: 10.1095/biolreprod.113.109488

  • 133

    MiyataHThalerCDHaimoLTCardulloRA. Protease Activation and the Signal Transduction Pathway Regulating Motility in Sperm From the Water Strider Aquarius Remigis. Cytoskeleton (2012) 69(4):207–20. doi: 10.1002/cm.21012

  • 134

    GosneyRLiauW-SLamunyonCW. A Novel Function for the Presenilin Family Member Spe-4: Inhibition of Spermatid Activation in Caenorhabditis Elegans. BMC Dev Biol (2008) 8:44. doi: 10.1186/1471-213X-8-44

  • 135

    RodriguezAOliverHZouHChenPWangXAbramsJM. Dark is a Drosophila Homologue of Apaf-1/CED-4 and Functions in an Evolutionarily Conserved Death Pathway. Nat Cell Biol (1999) 1(5):272–9. doi: 10.1038/12984

  • 136

    SitnikJLFrancisCHensKHuybrechtsRWolfnerMFCallaertsP. Neprilysins: An Evolutionarily Conserved Family of Metalloproteases That Play Important Roles in Reproduction in Drosophila. Genetics (2014) 196(3):781–97. doi: 10.1534/genetics.113.160945

  • 137

    TangXCaoJZhangLHuangYZhangQRongYS. Maternal Haploid, a Metalloprotease Enriched at the Largest Satellite Repeat and Essential for Genome Integrity in Drosophila Embryos. Genetics (2017) 206(4):1829–39. doi: 10.1534/genetics.117.200949

  • 138

    QianM-XPangYLiuCHHaratakeKDuB-YJiD-Yet al. Acetylation-Mediated Proteasomal Degradation of Core Histones During DNA Repair and Spermatogenesis. Cell (2013) 153(5):1012–24. doi: 10.1016/j.cell.2013.04.032

  • 139

    CostoyaJAHobbsRMBarnaMCattorettiGManovaKSukhwaniMet al. Essential Role of Plzf in Maintenance of Spermatogonial Stem Cells. Nat Genet (2004) 36(6):653–9. doi: 10.1038/ng1367

  • 140

    JevtićPHaakonsenDLRapéM. An E3 Ligase Guide to the Galaxy of Small-Molecule-Induced Protein Degradation. Cell Chem Biol (2021) 28(7):1000–13. doi: 10.1016/j.chembiol.2021.04.002

  • 141

    VolpiSBongiorniSFabbrettiFWakimotoBTPranteraG. Drosophila Rae1 is Required for Male Meiosis and Spermatogenesis. J Cell Sci (2013) 126(Pt 16):3541–51. doi: 10.1242/jcs.111328

  • 142

    OttoneCGalassoAGemeiMPisaVGigliottiSPiccioniFet al. Diminution of Eif4e Activity Suppresses Parkin Mutant Phenotypes. Gene (2011) 470(1–2):12–9. doi: 10.1016/j.gene.2010.09.003

  • 143

    AramaEBaderMRieckhofGEStellerH. A Ubiquitin Ligase Complex Regulates Caspase Activation During Sperm Differentiation in Drosophila. PloS Biol (2007) 5(10):e251. doi: 10.1371/journal.pbio.0050251

  • 144

    Luke-GlaserSPintardLTyersMPeterM. The AAA-ATPase FIGL-1 Controls Mitotic Progression, and its Levels are Regulated by the CUL-3mel-26 E3 Ligase in the C. Elegans Germ Line. J Cell Sci (2007) 120(Pt 18):3179–87. doi: 10.1242/jcs.015883

  • 145

    NayakSSantiagoFEJinHLinDSchedlTKipreosET. The Caenorhabditis Elegans Skp1-Related Gene Family: Diverse Functions in Cell Proliferation, Morphogenesis, and Meiosis. Curr Biol (2002) 12(4):277–87. doi: 10.1016/S0960-9822(02)00682-6

  • 146

    MehtaRSteinkrausKASutphinGLRamosFJShamiehLSHuhAet al. Proteasomal Regulation of the Hypoxic Response Modulates Aging in C. elegans Sci (2009) 324(5931):1196–8. doi: 10.1126/science.1173507

  • 147

    LuL-YYuX. CHFR is Important for the Survival of Male Premeiotic Germ Cells. Cell Cycle (2015) 14(21):3454–60. doi: 10.1080/15384101.2015.1093701

  • 148

    YinYLinCKimSTRoigIChenHLiuLet al. The E3 Ubiquitin Ligase Cullin 4A Regulates Meiotic Progression in Mouse Spermatogenesis. Dev Biol (2011) 356(1):5162. doi: 10.1016/j.ydbio.2011.05.661

  • 149

    KopanjaDRoyNStoyanovaTHessRABagchiSRaychaudhuriP. Cul4A is Essential for Spermatogenesis and Male Fertility. Dev Biol (2011) 352(2):278–87. doi: 10.1016/j.ydbio.2011.01.028

  • 150

    YinYLiuLYangCLinCVeithGMWangCet al. Cell Autonomous and Nonautonomous Function of CUL4B in Mouse Spermatogenesis. J Biol Chem (2016) 291(13):6923–35. doi: 10.1074/jbc.M115.699660

  • 151

    LinC-YChenC-YYuC-HYuI-SLinS-RWuJ-Tet al. Human X-Linked Intellectual Disability Factor CUL4B Is Required for Post-Meiotic Sperm Development and Male Fertility. Sci Rep (2016) 6:20227. doi: 10.1038/srep20227

  • 152

    AliAMistryBVAhmedHAAbdullaRAmerHAPrinceAet al. Deletion of DDB1- and CUL4- Associated Factor-17 (Dcaf17) Gene Causes Spermatogenesis Defects and Male Infertility in Mice. Sci Rep (2018) 8(1):9202. doi: 10.1038/s41598-018-27379-0

  • 153

    ZhangXXiaZLvXLiDLiuMZhangRet al. DDB1- and CUL4-Associated Factor 8 Plays a Critical Role in Spermatogenesis. Front Med (2021) 15(2):302–12. doi: 10.1007/s11684-021-0851-8

  • 154

    HuangGKaufmanAJRyanRJHRominYHurynLBainsSet al. Mouse DCUN1D1 (SCCRO) is Required for Spermatogenetic Individualization. PloS One (2019) 14(1):e0209995. doi: 10.1371/journal.pone.0209995

  • 155

    ZhangHChenFDongHXieMZhangHChenYet al. Loss of Fbxw7 in Sertoli Cells Impairs Testis Development and Causes Infertility in Mice†. Biol Reprod (2020) 102(4):963–74. doi: 10.1093/biolre/ioz230

  • 156

    FokKLBoseRShengKChangC-WKatz-EgorovMCultyMet al. Huwe1 Regulates the Establishment and Maintenance of Spermatogonia by Suppressing DNA Damage Response. Endocrinol (2017) 158(11):4000–16. doi: 10.1210/en.2017-00396

  • 157

    BoseRShengKMoawadARMankuGO’FlahertyCTaketoTet al. Ubiquitin Ligase Huwe1 Modulates Spermatogenesis by Regulating Spermatogonial Differentiation and Entry Into Meiosis. Sci Rep (2017) 7(1):17759. doi: 10.1038/s41598-017-17902-0

  • 158

    EisaAABangSCrawfordKJMurphyEMFengWWDeySet al. X-Linked Huwe1 Is Essential for Oocyte Maturation and Preimplantation Embryo Development. iSci (2020) 23(9):101523. doi: 10.1016/j.isci.2020.101523

  • 159

    HaraguchiHHirotaYSaito-FujitaTTanakaTShimizu-HirotaRHaradaMet al. Mdm2-P53-SF1 Pathway in Ovarian Granulosa Cells Directs Ovulation and Fertilization by Conditioning Oocyte Quality. FASEB J (2019) 33(2):2610–20. doi: 10.1096/fj.201801401R

  • 160

    ZhangC-XZhangQXieY-YHeX-YXiangCHouX-Set al. Mouse Double Minute 2 Actively Suppresses P53 Activity in Oocytes During Mouse Folliculogenesis. Am J Pathol (2017) 187(2):339–51. doi: 10.1016/j.ajpath.2016.09.023

  • 161

    FouchécourtSLiveraGMessiaenSFumelBParentA-SMarineJ-Cet al. Apoptosis of Sertoli Cells After Conditional Ablation of Murine Double Minute 2 (Mdm2) Gene is P53-Dependent and Results in Male Sterility. Cell Death Differ (2016) 23(3):521–30. doi: 10.1038/cdd.2015.120

  • 162

    ChengDXiongCLiJSuiCWangSLiHet al. The Effect of Mahogunin Gene Mutant on Reproduction in Male Mice: A New Sight for Infertility? Andrologia (2014) 46(2):98105. doi: 10.1111/and.12050

  • 163

    WangXKangJ-YWeiLYangXSunHYangSet al. PHF7 is a Novel Histone H2A E3 Ligase Prior to Histone-to-Protamine Exchange During Spermiogenesis. Development (2019) 146(13):dev175547. doi: 10.1242/dev.175547

  • 164

    XuZSongZLiGTuHLiuWLiuYet al. H2B Ubiquitination Regulates Meiotic Recombination by Promoting Chromatin Relaxation. Nucleic Acids Res (2016) 44(20):9681–97. doi: 10.1093/nar/gkw652

  • 165

    MelnickAFGaoYLiuJDingDPredomAKellyCet al. RNF216 is Essential for Spermatogenesis and Male Fertility†. Biol Reprod (2019) 100(5):1132–4. doi: 10.1093/biolre/ioz006

  • 166

    GuoYSongYGuoZHuMLiuBDuanHet al. Function of RAD6B and RNF8 in Spermatogenesis. Cell Cycle (2018) 17(2):162–73. doi: 10.1080/15384101.2017.1361066

  • 167

    LuL-YWuJYeLGavrilinaGBSaundersTLYuX. RNF8-Dependent Histone Modifications Regulate Nucleosome Removal During Spermatogenesis. Dev Cell (2010) 18(3):371–84. doi: 10.1016/j.devcel.2010.01.010

  • 168

    DickinsRAFrewIJHouseCMO’BryanMKHollowayAJHavivIet al. The Ubiquitin Ligase Component Siah1a is Required for Completion of Meiosis I in Male Mice. Mol Cell Biol (2002) 22(7):2294–303. doi: 10.1128/MCB.22.7.2294-2303.2002

  • 169

    HaiLSzwarcMMHeBLonardDMKommaganiRDeMayoFJet al. Uterine Function in the Mouse Requires Speckle-Type Poz Protein. Biol Reprod (2018) 98(6):856–69. doi: 10.1093/biolre/ioy060

  • 170

    WeiJChenLLiFYuanYWangYXiaWet al. HRD1-ERAD Controls Production of the Hepatokine FGF21 Through CREBH Polyubiquitination. EMBO J (2018) 37(22):e98942. doi: 10.15252/embj.201898942

  • 171

    KettunenKMKarikoskiRHämäläinenRHToivonenTTAntonenkovVDKulesskayaNet al. Trim37-Deficient Mice Recapitulate Several Features of the Multi-Organ Disorder Mulibrey Nanism. Biol Open (2016) 5(5):584–95. doi: 10.1242/bio.016246

  • 172

    Torres-FernándezLAEmichJPortYMitschkaSWösteMSchneiderSet al. TRIM71 Deficiency Causes Germ Cell Loss During Mouse Embryogenesis and Is Associated With Human Male Infertility. Front Cell Dev Biol (2021) 9:658966. doi: 10.3389/fcell.2021.658966

  • 173

    KwonYTXiaZAnJYTasakiTDavydovIVSeoJWet al. Female Lethality and Apoptosis of Spermatocytes in Mice Lacking the UBR2 Ubiquitin Ligase of the N-End Rule Pathway. Mol Cell Biol (2003) 23(22):8255–71. doi: 10.1128/MCB.23.22.8255-8271.2003

  • 174

    PanHJiangNSunSJiangHXuJJiangXet al. UHRF1-Repressed 5’-Hydroxymethylcytosine is Essential for the Male Meiotic Prophase I. Cell Death Dis (2020) 11(2):142. doi: 10.1038/s41419-020-2333-3

  • 175

    CaoYLiMLiuFNiXWangSZhangHet al. Deletion of Maternal UHRF1 Severely Reduces Mouse Oocyte Quality and Causes Developmental Defects in Preimplantation Embryos. FASEB J (2019) 33(7):8294–305. doi: 10.1096/fj.201801696RRRR

  • 176

    RodriguezABrileySMPattonBKTripuraniSKRajapaksheKCoarfaCet al. Loss of the E2 SUMO-Conjugating Enzyme Ube2i in Oocytes During Ovarian Folliculogenesis Causes Infertility in Mice. Development (2019) 146(23):dev176701. doi: 10.1242/dev.176701

  • 177

    KoenigP-ANichollsPKSchmidtFIHagiwaraMMaruyamaTFrydmanGHet al. The E2 Ubiquitin-Conjugating Enzyme UBE2J1 is Required for Spermiogenesis in Mice. J Biol Chem (2014) 289(50):34490–502. doi: 10.1074/jbc.M114.604132

  • 178

    GrzmilPAltmannMEAdhamIMEngelUJarryHSchweyerSet al. Embryo Implantation Failure and Other Reproductive Defects in Ube2q1-Deficient Female Mice. Reproduction (2013) 145(1):4556. doi: 10.1530/REP-12-0054

  • 179

    JiangXWangXZhangXXiaoZZhangCLiuXet al. A Homozygous RNF220 Mutation Leads to Male Infertility With Small-Headed Sperm. Gene (2019) 688:13–8. doi: 10.1016/j.gene.2018.11.074

  • 180

    WangHLuYJiangTBergHLiCXiaY. The Arabidopsis U-Box/ARM Repeat E3 Ligase AtPUB4 Influences Growth and Degeneration of Tapetal Cells, and its Mutation Leads to Conditional Male Sterility. Plant J (2013) 74(3):511–23. doi: 10.1111/tpj.12146

  • 181

    ByzovaMVFrankenJAartsMGde Almeida-EnglerJEnglerGMarianiCet al. Arabidopsis STERILE APETALA, a Multifunctional Gene Regulating Inflorescence, Flower, and Ovule Development. Genes Dev (1999) 13(8):1002–14. doi: 10.1101/gad.13.8.1002

  • 182

    LingYZhangCChenTHaoHLiuPBressanRAet al. Mutation in SUMO E3 Ligase, SIZ1, Disrupts the Mature Female Gametophyte in Arabidopsis. PloS One (2012) 7(1):e29470. doi: 10.1371/journal.pone.0029470

  • 183

    LiuMShiSZhangSXuPLaiJLiuYet al. SUMO E3 Ligase AtMMS21 is Required for Normal Meiosis and Gametophyte Development in Arabidopsis. BMC Plant Biol (2014) 14:153. doi: 10.1186/1471-2229-14-153

  • 184

    ThangasamySGuoC-LChuangM-HLaiM-HChenJJauhG-Y. Rice SIZ1, a SUMO E3 Ligase, Controls Spikelet Fertility Through Regulation of Anther Dehiscence. New Phytol (2011) 189(3):869–82. doi: 10.1111/j.1469-8137.2010.03538.x

  • 185

    CayliSOcakliSErdemirFTasUAslanHYenerTet al. Developmental Expression of P97/VCP (Valosin-Containing Protein) and Jab1/CSN5 in the Rat Testis and Epididymis. Reprod Biol Endocrinol (2011) 9:117. doi: 10.1186/1477-7827-9-117

  • 186

    WangPJMcCarreyJRYangFPageDC. An Abundance of X-Linked Genes Expressed in Spermatogonia. Nat Genet (2001) 27(4):422–6. doi: 10.1038/86927

  • 187

    UhlmannFWernicDPoupartMAKooninEVNasmythK. Cleavage of Cohesin by the CD Clan Protease Separin Triggers Anaphase in Yeast. Cell (2000) 103(3):375–86. doi: 10.1016/S0092-8674(00)00130-6

  • 188

    BuonomoSBClyneRKFuchsJLoidlJUhlmannFNasmythK. Disjunction of Homologous Chromosomes in Meiosis I Depends on Proteolytic Cleavage of the Meiotic Cohesin Rec8 by Separin. Cell (2000) 103(3):387–98. doi: 10.1016/S0092-8674(00)00131-8

  • 189

    WaizeneggerICHaufSMeinkeAPetersJM. Two Distinct Pathways Remove Mammalian Cohesin From Chromosome Arms in Prophase and From Centromeres in Anaphase. Cell (2000) 103(3):399410. doi: 10.1016/S0092-8674(00)00132-X

  • 190

    ChenDYLeeYVan TineBASearlemanACWestergardTDLiuHet al. A Pharmacologic Inhibitor of the Protease Taspase1 Effectively Inhibits Breast and Brain Tumor Growth. Cancer Res (2012) 72(3):736–46. doi: 10.1158/0008-5472.CAN-11-2584

  • 191

    LeeBParkIJinSChoiHKwonJTKimJet al. Impaired Spermatogenesis and Fertility in Mice Carrying a Mutation in the Spink2 Gene Expressed Predominantly in Testes. J Biol Chem (2011) 286(33):29108–17. doi: 10.1074/jbc.M111.244905

  • 192

    TardifSGuyonnetBCormierNCornwallGA. Alteration in the Processing of the ACRBP/sp32 Protein and Sperm Head/Acrosome Malformations in Proprotein Convertase 4 (PCSK4) Null Mice. Mol Hum Reprod (2012) 18(6):298307. doi: 10.1093/molehr/gas009

  • 193

    FujiharaYMiyataHIkawaM. Factors Controlling Sperm Migration Through the Oviduct Revealed by Gene-Modified Mouse Models. Exp Anim (2018) 67(2):91104. doi: 10.1538/expanim.17-0153

  • 194

    LinderBBammerSHeinleinUA. Delayed Translation and Posttranslational Processing of Cyritestin, an Integral Transmembrane Protein of the Mouse Acrosome. Exp Cell Res (1995) 221(1):6672. doi: 10.1006/excr.1995.1353

  • 195

    BlobelCPMylesDGPrimakoffPWhiteJM. Proteolytic Processing of a Protein Involved in Sperm-Egg Fusion Correlates With Acquisition of Fertilization Competence. J Cell Biol (1990) 111(1):6978. doi: 10.1083/jcb.111.1.69

  • 196

    HanCChoiEParkILeeBJinSKimDHet al. Comprehensive Analysis of Reproductive ADAMs: Relationship of ADAM4 and ADAM6 With an ADAM Complex Required for Fertilization in Mice. Biol Reprod (2009) 80(5):1001–8. doi: 10.1095/biolreprod.108.073700

  • 197

    TokuhiroKIkawaMBenhamAMOkabeM. Protein Disulfide Isomerase Homolog PDILT is Required for Quality Control of Sperm Membrane Protein ADAM3 and Male Fertility. PNAS (2012) 109(10):3850–5. doi: 10.1073/pnas.1117963109

  • 198

    XiongWShenCLiCZhangXGeHTangLet al. Dissecting the PRSS37 Interactome and Potential Mechanisms Leading to ADAM3 Loss in PRSS37-Null Sperm. J Cell Sci (2021) 134(10):jcs258426. doi: 10.1242/jcs.258426

  • 199

    CornwallGAHsiaN. ADAM7, A Member of the ADAM (a Disintegrin and Metalloprotease) Gene Family is Specifically Expressed in the Mouse Anterior Pituitary and Epididymis. Endocrinol (1997) 138(10):4262–72. doi: 10.1210/endo.138.10.5468

  • 200

    WhellySJohnsonSPowellJBorchardtCHastertMCCornwallGA. Nonpathological Extracellular Amyloid is Present During Normal Epididymal Sperm Maturation. PloS One (2012) 7(5):e36394. doi: 10.1371/journal.pone.0036394

  • 201

    TonaiSKawabataANakanishiTLeeJYOkamotoAShimadaMet al. Iron Deficiency Induces Female Infertile in Order to Failure of Follicular Development in Mice. J Reprod Dev (2020) 66(5):475–83. doi: 10.1262/jrd.2020-074

  • 202

    NyALeonardssonGHägglundACHägglöfPPloplisVACarmelietPet al. Ovulation in Plasminogen-Deficient Mice. Endocrinol (1999) 140(11):5030–5. doi: 10.1210/endo.140.11.7113

  • 203

    PiephoRW. Overview of the angiotensin-converting-enzyme inhibitors. Am J Health Syst Pharm. (2000) 57(Suppl 1):S3–7. doi: 10.1093/ajhp/57.suppl_1.S3

  • 204

    StraubARoehrigSHillischA. Oral, Direct Thrombin and Factor Xa Inhibitors: The Replacement for Warfarin, Leeches, and Pig Intestines? Angew Chem Int Ed Engl (2011) 50(20):4574–90. doi: 10.1002/anie.201004575

  • 205

    NutescuEAWittkowskyAK. Direct Thrombin Inhibitors for Anticoagulation. Ann Pharmacother (2004) 38(1):99109. doi: 10.1345/aph.1D066

  • 206

    DeeksSGSmithMHolodniyMKahnJO. HIV-1 Protease Inhibitors. A Rev Clin JAMA (1997) 277(2):145–53. doi: 10.1001/jama.1997.03540260059037

  • 207

    AgbowuroAAHustonWMGambleABTyndallJDA. Proteases and Protease Inhibitors in Infectious Diseases. Med Res Rev (2018) 38(4):1295–331. doi: 10.1002/med.21475

  • 208

    EatemadiAAiyelabeganHTNegahdariBMazlomiMADaraeeHDaraeeNet al. Role of Protease and Protease Inhibitors in Cancer Pathogenesis and Treatment. BioMed Pharmacother (2017) 86:221–31. doi: 10.1016/j.biopha.2016.12.021

Summary

Keywords

protease, fertilization, proteolysis, protease inhibitor, pseudoprotease, gene-modified animal models, ubiquitin-proteasome system, sperm maturation

Citation

Kiyozumi D and Ikawa M (2022) Proteolysis in Reproduction: Lessons From Gene-Modified Organism Studies. Front. Endocrinol. 13:876370. doi: 10.3389/fendo.2022.876370

Received

15 February 2022

Accepted

28 March 2022

Published

04 May 2022

Volume

13 - 2022

Edited by

Erwin Goldberg, Northwestern University, United States

Reviewed by

Toshinobu Tokumoto, Shizuoka University, Japan; Martine Culty, University of Southern California, United States

Updates

Copyright

*Correspondence: Daiji Kiyozumi, ; Masahito Ikawa,

This article was submitted to Reproduction, a section of the journal Frontiers in Endocrinology

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.

Outline

Cite article

Copy to clipboard


Export citation file


Share article

Article metrics