PKC beta 1 regulates meiotic cell cycle in mouse oocyte

PKC beta I, a member of the classical protein kinase C family, plays key roles in regulating cell cycle transition. Here, we report the expression, localization and functions of PKC beta I in mouse oocyte meiotic maturation. PKC beta I and p-PKC beta I (phosphor-PKC beta I) were expressed from germinal vesicle (GV) stage to metaphase II (MII) stage. Confocal microscopy revealed that PKC beta I was localized in the GV and evenly distributed in the cytoplasm after GV breakdown (GVBD), and it was concentrated at the midbody at telophase in meiotic oocytes. While, p-PKC beta I was concentrated at the spindle poles at the metaphase stages and associated with midbody at telophase. Depletion of PKC beta I by specific siRNA injection resulted in defective spindles, accompanied with spindle assembly checkpoint activation, metaphase I arrest and failure of first polar body (PB1) extrusion. Live cell imaging analysis also revealed that knockdown of PKC beta I resulted in abnormal spindles, misaligned chromosomes, and meiotic arrest of oocytes arrest at the Pro-MI/MI stage. PKC beta I depletion did not affect the G2/M transition, but its overexpression delayed the G2/M transition through regulating Cyclin B1 level and Cdc2 activity. Our findings reveal that PKC beta I is a critical regulator of meiotic cell cycle progression in oocytes.