Oocyte developmental competence and embryo quality: distinction and new perspectives

Gilbert, IMacaulay, ARobert, C

In vitro embryo production is the cornerstone of infertility treatment in human and is increasingly used in cattle to propagate high genetic merit animals. To increase its efficiency, many different approaches have been tested all of which stem from the concepts of oocyte quality and developmental competence. Presented here are recently reported findings and perspectives related to bovine oocyte biology and analysis of blastocyst quality that addresses these concepts from a different angle supporting the complex nature of the very dynamic developmental window that encompasses late oogenesis up to blastocyst development. It was recently reported that the atypical nature of the oocyte is supported by extensive nurturing from the surrounding cumulus cells in the form of large cargo transfer as well as transfer of phosphocreatine as an alternate means of generating ATP to fulfill the oocyte’s needs during the energy demanding process of maturation. It has been shown many times over that the determinants of early embryogenesis are embedded in the oocyte, however, transcriptome analysis dissociates embryonic yield from the concept of embryonic quality. Within the divergent gene expression, long non-coding RNAs represent a very functionally diverse class of transcripts that have yet been characterized. Taken together, it is clear that a clearer definition of both oocyte and embryonic quality are still needed to support the improvement of in vitro embryo production.(AU)

1. oocyte competence
2. embryo quality
3. RNA transfer