CENP-V as a Potential Diagnostic Marker of Damage in Human Oocytes

Proper chromosome segregation is essential to avoid aneuploidy, yet in mammalian oocytes it progressively fails in an age-dependent manner. The ageing population and the increasing age of parenthood are leading to a declined fertility. Proteins contributing to correct chromosome segregation and oocyte ageing are therefore of central interest. Mouse oocytes deficient in CENP-V are strongly impaired in meiosis I. The spindle assembly checkpoint (SAC)-dependent arrest of about half of the Cenp-V -/- oocytes at metaphase I is only found in oocytes from young adults, not in oocytes >12 months. This suggests SAC weakening in ageing oocytes allowing them to proceed despite continuous presence of mis-aligned chromosomes and present CENP-V depleted oocytes as a model for age dependent weakening of the SAC. Sporadic cases of very-low oocyte survival rate have been observed after vitrification and thawing protocols in the clinical practice. However, no diagnostic tools are currently available to detect these cases. The relevance of this problem has led to a demand on the scientific community to obtain specific and early biomarkers to predict decreased oocyte survival rates after thawing. The main goal of this project is to establish the expression levels of the CENP-V protein in human oocytes as a diagnostic tool for the aging of a cohort of oocytes. With this purpose, the immature oocytes from the oocytes cohort recovered from women with advanced maternal age (AMA) and control, will be matured in vitro in order to compare the CENP-V expression levels between both populations. In addition, in patients with AMA, these expression levels will be correlated with the aneuploidy rate from the blastocyst of the same oocyte cohort. CENP-V-deleted mouse oocytes show higher rate of aneuploidy and spindle aberrations after cold treatment compared to control oocytes. We hypothesize that alterations in the expression level of CENP-V could be responsible of the decrease in oocyte survival rate after thawing. The main objective of this project is to establish the expression levels of the CENP-V protein in human oocytes as a diagnostic tool to assess the damage of a cohort of oocytes. For this purpose, oocytes retrieved from advanced maternal age (AMA) and control patients, as well as oocytes undergoing vitrification / thawing procedures and controls oocytes, will be analyzed. In this study, only the immature oocytes of the patients, which are destined to be discarded and not used in their treatment, will be analyzed.