Early Primate Embryo Development Meets Single-cell Multi-omics

Given the constraints imposed by the "14-day ethics" rule, numerous critical events occurring between the second and fourth weeks of embryonic development remain poorly understood. This underscores the necessity of a detailed understanding of embryonic development and regulation during this period, which is indispensable for preventing pregnancy failure, treating birth defects, and promoting human reproductive health. Rodents, characterized by their small size, rapid growth, strong reproductive capacity, and fully sequenced genomes, are widely used as crucial models for studying embryonic development. However, the substantial physiological differences between rodents and primates due to evolutionary divergence make it challenging to directly apply findings from rodent studies to primates. Besides, primates, our closest relatives in terms of evolutionary phylogenetics and physiological characteristics, share more than 95% genetic homology with humans, underscoring the urgent need for primate research. Furthermore, early-stage embryonic cells are both scarce and diverse, making their regulatory mechanisms and developmental pathways typically elucidated through single-cell sequencing. For instance, three significant articles published in Science in 2018 mapped the complete atlas of organ and tissue development from fertilization and captured dynamic gene expression profiles in zebrafish and frogs through single-cell transcriptomics. Unfortunately, relying solely on single-cell omics analysis falls short in effectively and comprehensively deciphering the intricate cellular network information. Single-cell multi-omics empower researchers to systematically decode cell heterogeneity and developmental trajectories at the individual cell level by combining transcriptomics, epigenomics, proteomics, and metabolomics analyses. These emerging technologies play a significant role in life sciences, enabling the elucidation of critical early primate embryonic development events from a multi-dimensional perspective, including zygotic genome activation (ZGA), X-chromosome dosage compensation, origins of primordial germ cells (PGCs), mechanisms of cell fate determination, and pivotal events in gastrulation and early organogenesis. This article chronicles the advancement of pivotal technologies, from single-cell histology to multi-omics, beginning with the single-cell transcriptome and culminating in a comprehensive analysis according to the central dogma of molecular biology. It highlights the transition from a singular to a holistic perspective in cellular analysis and reviews the application of multi-omics techniques in unveiling early primate embryonic development. Finally, it delves into the application of multi-omics technologies in enhancing our understanding of early primate embryonic development and explores future possibilities, directions, and challenges in this rapidly evolving field. In doing so, it emphasizes the critical role of interdisciplinary approaches, combining insights from genetics, molecular biology, and bioinformatics to foster innovations in reproductive medicine and developmental biology. The integration of such technologies offers the promise of breakthroughs in understanding complex biological processes, potentially leading to novel therapeutic strategies and advancements in reproductive health and medicine.