Regulation of gene expression during oocyte maturation and early embryo development

Precise regulation of gene expression ensures oocytes and embryos accomplish the dynamic events required for successful oocyte maturation and early embryo development. However, most studies of gene expression regulation have focused on the mouse. In this respect, we used the cow as an alternative mammalian model to study gene expression regulation during oocyte maturation and early embryo development. We described dynamic changes in gene expression and poly(A) tail length during bovine oocyte maturation and early embryo development. As a result of these changes, the reference genes most suitable for gene expression normalization are different when different reverse transcription priming methods are employed. On the other hand, epigenetic alterations and differential regulation of transcription factors affect gene expression at the transcriptional level in embryos. One of the major epigenetic events-XCI, is initiated at morula stage in female bovine embryos. However, the initiation of XCI does not lead to complete down-regulation of all X-linked genes. The expression of the transcription factor CDX2 in bovine embryos is up regulated after exposure to LPA. But LPA stimulation does not change embryo constitution in terms of percentages of cells committed to one or another lineage. Overall, a better understanding of gene expression regulation during ocoyte maturation and early embryo development broadens our fundamental knowledge of mammalian embryonic development and will improve our understanding of the requirements for cell lineage determination and pluripotency, and the short and longer term consequences of epigenetic disturbances resulting from sub-optimal maternal health and nutrition or in vitro fertilization and embryo culture conditions.