The Phosphatase Dusp7 Drives Meiotic Resumption and Chromosome Alignment in Mouse Oocytes

Abstract

Summary: Mammalian oocytes are stored in the ovary, where they are arrested in prophase for prolonged periods. The mechanisms that abrogate the prophase arrest in mammalian oocytes and reinitiate meiosis are not well understood. Here, we identify and characterize an essential pathway for the resumption of meiosis that relies on the protein phosphatase DUSP7. DUSP7-depleted oocytes either fail to resume meiosis or resume meiosis with a significant delay. In the absence of DUSP7, Cdk1/CycB activity drops below the critical level required to reinitiate meiosis, precluding or delaying nuclear envelope breakdown. Our data suggest that DUSP7 drives meiotic resumption by dephosphorylating and thereby inactivating cPKC isoforms. In addition to controlling meiotic resumption, DUSP7 has a second function in chromosome segregation: DUSP7-depleted oocytes that enter meiosis show severe chromosome alignment defects and progress into anaphase prematurely. Altogether, these findings establish the phosphatase DUSP7 as an essential regulator of multiple steps in oocyte meiosis. : Tischer and Schuh study how oocytes resume meiosis after a prolonged prophase arrest. They show that the phosphatase DUSP7 drives meiotic resumption by dephosphorylating and inactivating conventional protein kinase C (cPKC) isoforms. Hyperactivation of cPKC isoforms in the absence of DUSP7 causes a decrease in the activity of the cell-cycle-regulating kinase Cdk1/Cyclin B, preventing meiotic resumption. Keywords: mouse oocytes, meiosis, DUSP7, phosphatase, PKC, chromosome segregation, prophase arrest