Casein kinase (I) alpha (CK1α) is a member of serine/threonine protein kinase, generally present in all eukaryotes.We examined Ck1α mRNA and protein expression, as well as its subcellular localization in mouse oocytes.We used CK1α specific morpholino injection and specific CK1 inhibitor D4476 to block the function, leading to failure of polar body 1 (PB 1) extrusion, chromosome abnormal, oocyte pro-MI arrest and impairment of embryo developmental potential.We employed pyrvinium pamoate (PP) to enhance CK1α activity, leading PBI extrusion failure and severe congression abnormalities.Taken together, our study for the first time demonstrates that CK1α is required for chromosome alignment and segregation during oocyte meiotic maturation and early embryo development.