OMICS for the Identification of Biomarkers for Oocyte Competence, with Special Reference to the Mare as a Prospective Model for Human Reproductive Medicine

A crucial component of Assisted Reproductive Technologies (ART) is the assessment of oocyte developmental potential, to allow selection of those oocytes most likely to result in fertilization and pregnancy. Currently, oocyte quality assessment is largely based on the morphological appearance of the cumulus-oocyte complex, however the accuracy of morphological methods, as predictive of oocyte competence, is still suboptimal. Therefore, the development of objective, accurate, fast and reliable tests for assessing oocyte developmental potential remains an important aim of human and veterinary reproductive medicine. The process of oocyte meiotic maturation, which is central to the developmental competence of the oocyte, is regulated by numerous genes (Matzuk & Lamb, 2008; Fauser et al., 2011) and protein pathways (Kubiak, 2011) and is accompanied by significant changes within the oocyte at many levels. Better understanding of oocyte meiotic maturation would allow better support of this process to increase the success of reproductive biotechnologies, and thus overcome some forms of infertility. Recently, global assessment strategies, namely OMICS, investigating genomic, transcriptomic, proteomic, lipidomic, and glycomic profiles of oocytes, cumulus or granulosa cells have become increasingly applied to the study of oocyte physiology and pathology. Also being investigated is the oocyte-cumulus metabolome, via measurements of metabolites in biological fluids, such as follicular or tubal fluid, or in culture media. The establishment of these technologies, which are in their initial stages of application to reproductive biology, can require large sample numbers; only animal models can meet this requirement. Because of their wide availability and the body of existing knowledge regarding their biology, oocytes of large animals provide useful models for investigating the relationship between oocyte developmental competence and OMICS biomarkers. This review summarizes recent literature on the application of OMICS strategies to evaluating developmental competence of human oocytes and oocytes of large