Overexpression of CCNK Leads to Early Resumption of Meiosis in Mouse Oocytes

The synthesis and degradation of Cyclins are critical for cell cycle progression. Cyclin K (CCNK), a member of the Cyclin family, is known to regulate transcriptional elongation and the MAPK signaling pathway by binding to CDK12/13. While CCNK has been extensively studied in cancers, its roles in oocyte maturation remains unclear. In this study, we found that overexpression of CCNK accelerates the resumption of meiosis in oocytes. This effect is primarily attributed to the early nuclear entry of Cyclin B1 (CCNB1) and the premature activation of maturation promoting factor. These findings suggest that CCNK plays a vital role in the process of oocyte maturation, and its dysregulation could disrupt the normal progression of meiosis.