Biology subjects

Ramos-Ibeas, P.

Publications and source records attributed to Ramos-Ibeas, P..

4 recordsLinked to original sources

bioRxiv2026

NANOG is dispensable for hypoblast but essential for embryonic disc development during conceptus elongation in sheep

NANOG is a conserved regulator of epiblast identity and is essential for hypoblast development and embryo survival after the blastocyst stage in mice. However, its role during post-blastocyst development remains poorly understood in non-rodent mammals. Here, we investigated the function of NANOG during ovine embryogenesis using CRISPR/Cas9-mediated gene ablation. NANOG ablation did not affect blastocyst formation or the initial development of the epiblast. However, NANOG-deficient blastocysts contained significantly fewer SOX17+ hypoblast cells by day (D) 8, followed by reduced hypoblast migration during early post-hatching stages in D12 in vitro embryos. These defects were transient, as hypoblast development was comparable between NANOG-deficient and wild-type conceptuses during subsequent in vivo conceptus elongation from embryonic day (E) 11 onwards. In contrast, although extraembryonic membranes development and conceptus elongation proceeded normally, NANOG-deficient conceptuses lacked SOX2+ epiblast cells and failed to form an embryonic disc (ED) from E11 onwards. These findings demonstrate that NANOG is dispensable for hypoblast development but is required for epiblast maintenance and ED formation during conceptus elongation in sheep.

developmental biology↗

bioRxiv2026

A Single-Cell Transcriptomic Atlas of Symmetry Breaking Across Eutherian Mammals

The mammalian body plan is established during symmetry breaking and gastrulation. In ungulates and primates, these events occur within a flat embryonic disc and coincide with the developmental window most susceptible to pregnancy loss. Here, we generated a single-cell RNA sequencing atlas of in vivo sheep embryos that defines the timing and molecular programs underlying lineage segregation, as well as the inter-lineage signalling mediating anterior visceral hypoblast specification (AVH) and primitive streak formation. By integrating sheep data with stage-matched datasets from cow, pig, rabbit, mouse, and marmoset, we constructed a cross-species atlas of anterior-posterior axis formation and identified conserved anterior and posterior hypoblast markers. Despite major differences in embryo morphology and developmental tempo, core signalling pathways NODAL, WNT, BMP, and FGF were broadly conserved. However, species-specific features emerged, including divergent BMP and FGF ligand usage and distinct BMP sources: only the mouse relied on trophectoderm-derived BMPs, whereas in other mammals BMPs originated primarily from the hypoblast. Functional experiments showed that NODAL is dispensable for early epiblast specification but essential for maintaining epiblast and AVH survival during symmetry breaking in sheep. These findings establish sheep as a powerful model for understanding human peri-implantation development and improving stem cell-based embryo models.

developmental biology↗

bioRxiv2020

Specification and epigenetic resetting of the pig germline exhibit conservation with the human lineage

Investigations on the human germline and programming are challenging due to limited access to embryonic material. However, the pig as a model may provide insight on transcriptional network and epigenetic reprogramming applicable to both species. Here we show that during the pre- and early migratory stages pig primordial germ cells (PGCs) initiate large-scale epigenetic reprogramming, including DNA demethylation involving TET-mediated hydroxylation and potentially base excision repair (BER). There is also macroH2A1 depletion and increased H3K27me3, as well as X chromosome reactivation (XCR) in females. Concomitantly, there is dampening of glycolytic metabolism genes and re-expression of some pluripotency genes like those in preimplantation embryos. We identified evolutionarily young transposable elements and gene coding regions resistant to DNA demethylation in acutely hypomethylated gonadal PGCs, with potential for transgenerational epigenetic inheritance. Detailed insights into the pig germline will likely contribute significantly to advances in human germline biology, including in vitro gametogenesis.

developmental biology↗

bioRxiv2018

Lineage segregation, pluripotency and X-chromosome inactivation in the pig pre-gastrulation embryo

High-resolution molecular programs delineating the cellular foundations of mammalian embryogenesis have emerged recently. Similar analysis of human embryos is limited to pre-implantation stages, since early post-implantation embryos are inaccessible. Notwithstanding, we previously suggested conserved principles of pig and human early development. For further insight on pluripotent states and lineage delineation, we analysed pig embryos at single cell resolution. Here we show progressive segregation of inner cell mass and trophectoderm in early blastocysts, and then of epiblast and hypoblast in late blastocysts. We detected distinct pluripotent states, first as a short naive state followed by a protracted primed state. Dosage compensation with respect to the X-chromosome in females is attained via X-inactivation in late epiblasts. Detailed human-pig comparison is a basis towards comprehending early human development and a foundation for further studies of human pluripotent stem cell differentiation in pig interspecies chimeras.

developmental biology↗