GATA3 is not required for sheep trophectoderm development, but it plays a role in post-hatching epiblast survival

Early embryo mortality represents a major challenge in livestock production, leading to significant economic losses. However, the molecular determinants underpinning early embryo development in these species remain poorly understood. GATA3 is a key transcription factor exclusively expressed by the trophectoderm (TE) in mammalian embryos. Although its ablation does not impede trophectoderm differentiation or blastocyst formation in mice, it is lethal at later developmental stages. Here, we aimed to investigate the role of GATA3 in ovine pre- and post-hatching development in vitro as well as during conceptus elongation in vivo. By generating GATA3 knockout (KO) embryos, we confirmed that GATA3 is dispensable for TE specification and blastocyst formation in ovine. GATA3 ablation did not impact developmental rates or TE development at post-hatching stages developed in vitro but it significantly reduced epiblast survival. Following embryo transfers to evaluate the effect of GATA3 ablation at later stages, the development of extraembryonic membranes (TE and hypoblast) during conceptus elongation was unaffected by GATA3 loss. However, a significantly reduced proportion of conceptuses developed an embryonic disc after GATA3 ablation. These findings indicate that GATA3 may play a previously unrecognised role in supporting epiblast development beyond the blastocyst stage in ovine.