ORIGINAL RESEARCH article
Front. Cell Dev. Biol.
Sec. Embryonic Development
Maternal Provisioning and Zygotic Activation: Transcriptomic Dynamics of Early Atlantic Halibut (Hippoglossus hippoglossus) Embryogenesis
Provisionally accepted
- 1Department of Biology, NTNU, Trondheim, Norway
- 2Animal and Food Genomics Group, Universita di Bologna Divisione di Scienze Animali, Bologna, Italy
- 3Nordic Halibut AS, Bergen, Norway
- 4Danmarks Tekniske Universitet Institut for Akvatiske Ressourcer, Lyngby, Denmark
Select one of your emails
You have multiple emails registered with Frontiers:
Notify me on publication
Please enter your email address:
If you already have an account, please login
You don't have a Frontiers account ? You can register here
Introduction: In Atlantic halibut (Hippoglossus hippoglossus) aquaculture, egg and larval quality remain major bottlenecks. Most transcriptomic and proteomic studies compare freshly fertilized eggs of good versus poor quality, assuming early molecular differences explain hatching success. However, many lethal phenotypes arise only after the mid-blastula transition (MBT), suggesting that early comparisons may overlook key developmental processes. Methods: We performed stage-resolved RNA sequencing of Atlantic halibut embryos spanning unfertilized egg (UF), cleavage (8C, 16C), blastula (BL), 25% epiboly (25EB), and blastopore closure (50 degree-days, 50 dd). Differential expression analysis (DESeq2 with LFC shrinkage), Gene Ontology (GO) overrepresentation (PANTHER, REVIGO), and curated axis-patterning gene sets from zebrafish orthologs were used to map transcriptional dynamics. Results: Minimal transcriptional change occurred during cleavage (UF–16C), dominated by maternal transcripts. A pronounced transcriptional shift emerged at MBT (16C→BL), marked by upregulation of canonical developmental pathways (Wnt, BMP, Notch) and axis-specification genes (e.g., bmp2b, chrd, wnt8b, fgf8a). These pathways remained active through gastrulation (BL→25EB), alongside enrichment of morphogenetic processes such as mesoderm formation and left–right symmetry. By 50 dd, expression shifted toward lineage differentiation programs involving neurons, muscle, and cranial skeleton. Axis-regulator dynamics showed that dorso– ventral (D–V) patterning is initiated by maternal factors but reinforced by zygotic cascades, whereas anterior–posterior (A–P) patterning is primarily zygotic. Discussion: Our results demonstrate that the decisive transcriptional programs underlying axis formation and organogenesis are activated from MBT onward. These findings imply that comparisons limited to unfertilized or early cleavage stages cannot capture the biology determining embryo viability. Stage-resolved analyses encompassing MBT and gastrulation are therefore essential for identifying transcriptomic markers of egg and larval quality in halibut.
Keywords: Atlantic halibut, Embryonic Development, Transcriptomics, egg quality, maternal zygotic transition
Received: 11 Oct 2025; Accepted: 20 Nov 2025.
Copyright: © 2025 Niepagen, Bertolini, Berg, Tomkiewicz and Kjørsvik. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Nils Niepagen, nils.niepagen@ntnu.no
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.