Ovarian follicle formation in Drosophila, which occurs throughout adult life, involves the coordinated proliferation and differentiation of somatic and germline cells within the ovaries. Narbonne et al. now report that the polyhomeotic (ph) gene is required in somatic cells for both their proliferation and differentiation during follicle formation(). This new role for the ph gene, a member of the Polycomb group (Pc-G)genes, which maintain the repression of homeotic gene transcription during development, was discovered during a gain-of-function screen for genes acting during ovarian follicle formation. Furthermore, loss of function of ph results in abnormal folliculogenesis, and mutations in two other Pc-G genes - Sex combs extra and Sex comb on midleg- produce similar ovarian defects. Given these results, the researchers suggest that Pc-G genes may have more general developmental roles than previously thought and that the Drosophila ovary could provide a new model system with which to study Pc-G gene function.
