Review: Lamin A/C, caspase-6, and chromatin configuration during meiosis resumption in the mouse oocyte

After in vitro maturation (IVM), isolation of the healthiest oocytes is essential for successful in vitro fertilization. As germinal vesicle (GV) oocytes resume meiosis through healthy or apoptotic pathways without discernable morphological criteria, we checked for an apoptotic element acting at the nucleus level. We hypothesized that caspase-6 with its corresponding substrate, lamin A/C, could be a potential target candidate, because caspase-6 is the only functional caspase for lamin A/C. We used immunohistochemistry methods, Western blots, and a specific caspase-6 inhibitor to determine the presence of lamin A/C and caspase-6 during oogenesis and in isolated oocytes. Our results demonstrated that these proteins were always present and that their distributions were related to oocyte maturity, determined by chromatin configuration and oocyte diameter. Caspase-6 inhibition slowed meiosis resumption suggesting the involvement of caspase-6 in the oocyte apoptotic pathway. Lamin A/C and caspase-6 could be valuable tools in the knowledge of oocyte in vitro destiny.