Developmental programs in chicken early embryos by whole transcriptome analysis.

Temporal regulation of gene expression is essential for early embryonic development. With the development of next-generation sequencing technologies, transcriptional profiling of early developmental processes in various vertebrates are already revealed. However, overall transcriptome analysis of early embryonic development in avian have never been investigated. In this study, to our knowledge, we provide comprehensive profiling of pre-oviposited embryos in chicken by whole-transcriptome RNA-seq for the first time. We demonstrated the presence of avian-specific mechanism of first- and second-wave of zygotic genome activation (ZGA). Chicken early embryo have distinct developmental programs between cleavage and area pellucida formation period. Additional speculation of epigenetic dynamics indicate that maternal-to-zygotic transition (MZT) in chicken is promoted after second-wave of ZGA, through EGK.VI to EGK.X stages. These extensive results contribute to understanding avian early embryogenesis and comparative studies with other species with many developmental aspects. Chicken early embryo (Oocyte to EGK.X) samples were investigated based on the whole transcriptome sequencing approach.