Examination of posttranscriptional regulation and de novo transcription during early embryonic development using RNA-Seq

Student Name: Krishna Bharathala

UCD Department: Animal Science

UCD Mentor: Dr. Pablo Ross

Background: Embryonic genome activation (EGA) is a critical time during mammalian development during which an embryo initiates transcription of many important genes after a long period of transcriptional silence and dependence on stored transcripts in the oocyte. In bovine, EGA typically occurs at the 8-16 cell stage. Before EGA, the oocyte and early embryo regulate protein production using post-transcriptional mechanisms like cytoplasmic poly-adenylation.  The global targets of this regulation are not very well understood. Despite the fact that the oocyte is mostly transcriptionally silent, there is some evidence of de novo transcription between fertilization and EGA.  In fact, it has been suggested that there is a minor EGA earlier in development at the 4-cell stage. This study focuses on that transcription and on the post-transcriptional regulation of stored maternal mRNAs. Results: Our results support and characterize the notion of EGA. They yielded inconclusive results with respect to cytoplasmic poly-adenylation and post-transcriptional modification. They also suggest that androgen receptors that play a role in oocyte maturation may also play a role in signaling between embryos and the mother during early embryonic development.