The project aimed to understand conceptus elongation, a largely unexplored developmental period exclusive from ungulates, which include the four most relevant mammalian livestock species in Europe: cows, pigs, sheep and goat. Key developmental processes occurring during this period include the formation of a flat embryonic disc resembling that of humans, and gastrulation, which entails the differentiation of epiblast cells into the three germ layers. The importance of studying these developmental processes is dual. On one side, failures during this period account for most reproductive losses in livestock species, exerting a negative impact on European Bioeconomy. On the other, given the similarities in embryonic disc formation between humans and ungulates, ungulate embryos serve as a model to understand human diseases and conditions that origin during early development, such as spina bifida. The overall objectives of this project have been 1) to uncover the role of specific genes on developmental processes by means of CRISPR-mediated ablation, 2) to determine the metabolic and proteomic composition of the uterine fluid to understand the embryonic requirements for conceptus elongation, and 3) to develop an in vitro system to achieve conceptus elongation without the need of experimental animals. The conclusions of the project organized by objectives have been 1) striking differences have been observed between the transcriptional regulation of mouse early development and that of ungulates and humans, the role of transcription factors essential for mouse development is not conserved between mammals, 2) a detailed analysis of the proteomics and metabolomics composition of the uterine fluid has provided clues to develop the in vitro system of the last objective and to design future nutritional and pharmacological strategies to prevent embryonic loss in farm animals, and 3) a fully in vitro system –not requiring from experimental animals- has been developed to achieve embryonic development to the beginning of gastrulation, an unprecedented advance in ungulates that provides a unique animal experimentation-free and real embryo model to study mammalian flat gastrulation.
