Role Of Cofilin1in Mouse Oocyte Meiosis

Cofilin1belongs to the ADF (actin depolymerizing factor)/Cofilin protein family, a class of actin-binding protein which exists widely in eukaryotic cell. They regulate the cytoskeleton by cutting off the actin filaments (F-actin) and increasing the depolymerization of F-actin, thus they affects the cell proliferation, migration, morphology, apoptosis and embryo development and some other important physiologic functions. Oocyte has abundant actin, so maybe Cofilin1plays a important role in oocyte meiosis through regulation of actin. In mammalia, studies about Cofilin1revolve in only localization during oocyte meiosis. We speculated the Cofilin1control the actin to regulated spindle assembling, migration and other processes in mouse oocyte meiosis. The present study investigated the expression pattern of Cofilin1in mouse oocyte meiosis and found that Cofilin1expressed at a high level from GVBD to Mll. Furthermore, the overexpression of Cofilin1or S3A mutant had no significant influence on oocyte meiosis, as western result indicated that Cofilin1expressed at a high level, suggesting that oocyte has a efficient regulation mechanism to keep Cofilin1level in normal, or dissection and depolymerization of Cofilin1for F-Actin has a saturation mechanism. However, the orientation and morphology of spindle had abnormity in oocyte knockdown Cofilin1. Further more study found the meiosis process was influenced significantly, more oocyte was arrested at pre-MI and MI of meiosis. In addition, we made investigation for LIMK1, a upstream kinase of Cofilin1, and found LIMK1has similar expression partern with Cofilin1, suggesting that LIMK1and Cofilin1has similar regulation in oocyte meiosis with mitosis. However, Co-IP found no evidence for the combination of LIMKI and Cofilin1, indicating the regulation was incomplete same with mitosis, reflect the complexity of cell cycle regulation.Besides, the paper explored involvement of caspase-8in luteolysis mechanism. In the mouse ovary, luteolysis is subdivided into two processes, functional luteolysis characterized by an initial decline of progesterone secretion and subsequent structural luteolysis involved in apoptosis. Caspase-8, the most well characterized apoptosis initiator, invovle in apoptosis initiation and signal transmission. In the estrus cycle of mouse, old corpus luteum had more cleaved caspase-8expression than new corpus luteum, the analysis of hormone treated and pregnant mice further confirmed this, indicating caspase-8plays a role in luteolysis, particularly in structural luteolysis.To explore the role of caspase-8in granulosa cell or oocyte, the present study used three conditiongal knockout mouse (cKO) generated by Cre/Lox system. Casp8F/F Acre cKO was used to detect the effect of caspase-8knockout in granulosa cell during female mouse reproduction. Casp8F/F GCre cKO was used to detect the effect of caspase-8knockout in oocyte during female mouse reproduction. Fertility test of all the cKO shows no significant difference from the control, indicating caspase-8are not necessary for their target cell during female mouse reproduction.