Mitotic spindle formation is regulated by centrosomes, composed of a centriole pair surrounded by pericentriolar materials(PCM) proteins. However, mammalian oocytes rely on acentriolar MTOCs for the function of meiotic spindle. The composition of acentriolar MTOCs and the molecular precesses that regulate the localization and accumulation in mammalian oocyte are not well understood. In this study, we analyzed the mechanisms of spindle microtubule nucleation and stability from MTOCs in mouse oocyte, and indentified Centrosomal protein192(CEP192) as a key regulator for acentriolar MTOC formation. CEP192 specifically colocalized with pericentrin (PCNT) during the oocyte maturaion. CEP192 proteins are localized throughout cytoplasm and around nucleus at GV stage, and then after BD stage, CEP192 proteins were further fragmented into smaller MTOCs around chromosomes. At metaphase, CEP192 proteins were concentrated in spindle pole. Knockdown of CEP192 using siRNAs resulted in metaphase I arrest. The arrested oocytes were characterized by reduced microtubule intensity and misalignment chromosome. Also at BD and ProMI stage, the oocytes reduced microtubule density and PCNT intensity. To confirm the mechanism of CEP192 regulation, we confirmed that PLK1 and AuroraA kinase were involved in CEP192 activation. The investigations for detailed molecular mechanisms of CEP192 and RanGTP for microtubule nucleation in oocytes are underway using various techniques including siRNA, mRNA, and positive or negative dominant injection and inhibitors.

• In-Won Lee(Department of Animal Sciences, Chungbuk National University, Brain Korea 21 center for Bio-Resource Development, Chungbuk National University, South Korea)
• Yujin Jo(Department of Animal Sciences, Chungbuk National University, Brain Korea 21 center for Bio-Resource Development, Chungbuk National University, South Korea)
• Sung-min Jeong(Department of Animal Sciences, Chungbuk National University, Brain Korea 21 center for Bio-Resource Development, Chungbuk National University, South Korea)
• Suk Namgoong(Department of Animal Sciences, Chungbuk National University, Gaesin-dong, Cheongju, Chungbuk. 361-763, Republic of Korea)
• Nam-Hyung Kim(Department of Animal Sciences, Chungbuk National University, Brain Korea 21 center for Bio-Resource Development, Chungbuk National University, South Korea)