Gonadal sexual identity is determined during development, but must also be maintained in adulthood. In Drosophila, the transcription factor Chinmo has been identified as a key regulator of male identity in the adult testis: it promotes expression of the male sex determinant DsxM (the homologue of which, DMRT1, is a key regulator of male identity in mouse testes). In chinmo mutants, somatic stem cells of the adult testis adopt female fate. Now (), Erika Matunis and co-workers show that Chinmo is not only necessary but also sufficient to promote male fate. Overexpression of chinmo in adult ovarian somatic cells leads to severe oogenesis phenotypes. Marker expression analysis suggests that chinmo-overexpressing somatic cells lose female identity and gain male fate. Strikingly, this also appears to affect the sexual fate of the germ cells: a proportion of ovary germ cells start to express male markers upon somatic chinmo expression. Unlike in testis, Chinmo in the ovary does not appear to promote DsxM expression, implying that there must be alternative mechanisms for masculinisation of somatic cells. Although these mechanisms have yet to be uncovered, these data provide strong evidence that sexual identity of the Drosophila adult ovary can be reprogrammed, and that sexual fate must be actively maintained throughout life.
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