Developmental competence in oocytes and cumulus cells: candidate genes and networks

Abstract

Common aspects of infertility can be seen across several species. In humans, dairy cows, and mares there is only a 25-35% chance of producing a live offspring after a single insemination, whether natural or artificial. Oocyte quality and subsequent embryo development can be affected by factors such as nutrition, hormonal regulation, and environmental influence. The objective of this study was to identify genes expressed in oocytes and/ or cumulus cells, across a diverse range of species, which may be linked to the ability an oocyte has to develop following fertilization. Performing a meta-analysis on previously published microarray data on various models of oocyte and embryo quality allowed for the identification of 56 candidate genes associated with oocyte quality across several species, 4 of which were identified in the cumulus cells that surround the oocyte. Twenty-one potential biomarkers were associated with increased competence and 35 potential biomarkers were associated with decreased competence. The upregulation of Metap2, and the decrease of multiple genes linked to mRNA and protein synthesis in models of competence, highlights the importance of de novo protein synthesis and its regulation for successful oocyte maturation and subsequent development. The negative regulation of Wnt signaling has emerged in human, monkey, bovine, and mouse models of oocyte competence. Atrx expression was linked to decreased competence in both oocytes and cumulus cells. Biological networks and transcription factor regulation associated with increased and decreased competence were also identified. These genes could potentially act as biomarkers of oocyte quality or as pharmacological targets for manipulation in order to improve oocyte developmental potential.

Predictive value of bovine follicular components as markers of oocyte developmental potential

“…Our findings cement earlier recommendations of TNFAIP6 as a potential cumulus cell indicator of oocyte competence in cattle (Assidi et al 2008;Tesfaye et al 2009). The panel of candidate genes was assembled following a thorough cross-species review of mammalian oocyte and cumulus cell transcriptomic data (O'Shea et al 2012). The poor correlation between our findings and that of Follicular predictors of bovine oocyte quality Reproduction, Fertility and Developmentpreviously published findings is possibly due to the variation in oocyte maturation and sample processing regimes associated with different species.…”

New molecular markers for the evaluation of gamete quality

“…Some of these seem to drive to the identification of 56 candidate genes associated with oocyte quality across several species, 4 of which were identified in the cumulus cells that surround the oocyte. Twenty-one potential biomarkers were associated with increased competence and 35 potential biomarkers were associated with decreased competence [32]. These genes could potentially act as biomarkers of oocyte competence or as pharmacological targets for manipulation in order to improve oocyte developmental potential, but more research is needed to apply in the routine of IVF clinic.…”

Identification of Maturation-Specific Proteins by Single-Cell Proteomics of Human Oocytes

“…Before resumption of maturation, oocytes undergo extensive growth, which is accompanied by high transcription rate, while fully matured oocytes become transcriptionally silenced (1,2). Various studies have investigated gene expression programs in human oocytes (3)(4)(5)(6)(7), yet the characterization of translation into functional protein products at different stages of oocyte growth and maturation remains poorly understood. During oocyte growth, many maternally transcribed mRNAs can be stored dispersed throughout the cytoplasm or in localized messenger ribonucleoprotein complexes in a translationally silent state (8).…”