Cumulus cell gene expression following the LH surge in bovine preovulatory follicles: potential early markers of oocyte competence

Abstract

Cumulus cells (CCs) are essential for oocytes to reach full development competency and become fertilized. Many major functional properties of CCs are triggered by gonadotropins and governed by the oocyte. Consequently, cumulus may reflect oocyte quality and is often used for oocyte selection. The most visible function of CCs is their ability for rapid extracellular matrix expansion after the LH surge. Although unexplained, LH induces the final maturation and improves oocyte quality. To study the LH signaling and gene expression cascade patterns close to the germinal vesicle breakdown, bovine CCs collected at 2 h before and 6 h after the LH surge were hybridized to a custom-made microarray to better understand the LH genomic action and find differentially expressed genes associated with the LH-induced oocyte final maturation. Functional genomic analysis of the 141 overexpressed and 161 underexpressed clones was performed according to their molecular functions, gene networks, and cell compartments. Following real-time PCR validation of our gene lists, some interesting pathways associated with the LH genomic action on CCs and their possible roles in oocyte final maturation, ovulation, and fertilization are discussed. A list of early potential markers of oocyte competency in vivo and in vitro is thereafter suggested. These early biomarkers are a preamble to understand the LH molecular pathways that trigger the final oocyte competence acquisition process in bovine.