PRC2 Controls Drosophila Oocyte Cell Fate by Repressing Cell Cycle Genes

• PRC2 is a determinant of the oocyte fate in Drosophila independently of PRC1
• In the absence of PRC2 components, the oocyte transdetermines into a nurse cell fate
• PRC2 is required for oocyte determination, not for specification of the preoocyte
• Oocyte fate maintenance requires PRC2-mediated repression of CycE and dap

SummaryThe oocyte is a unique cell type that undergoes extensive chromosome changes on its way to fertilization, but the chromatin determinants of its fate are unknown. Here, we show that Polycomb group (PcG) proteins of the Polycomb repressive complex 2 (PRC2) determine the fate of the oocyte in Drosophila. Mutation of the enzymatic PRC2 subunit Enhancer of zeste (E(z)) in the germline abolishes spatial and temporal control of the cell cycle and induces sterility via transdetermination of the oocyte into a nurse-like cell. This fate switch depends on loss of silencing of two PRC2 target genes, Cyclin E and the cyclin-dependent kinase inhibitor dacapo. By contrast, the PRC1 component Polycomb (Pc) plays no role in this process. Our results demonstrate that PRC2 plays an exquisite role in the determination of the oocyte fate by preventing its switching into an endoreplicative program.

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