Recent researches in our laboratory showed the implication of Dmxl2 gene in follicle formation in mouse ovaries (refer to Maëva Elzaiat’s poster). In the differentiating ovary Dmxl2 is expressed both by germ cells and somatic cells. Then, when folliculogenesis starts, the protein is detected in oocyte cytoplasm at every folliclar stages; but also in granulosa cells, faintly in primordial or primary follicles and strongly in follicle of later stages. Dmxl2 encodes for a scaffold protein presenting several protein/protein interaction domains, which appear to be involved in cell trafficking. In the female gonad, this protein could play a specific role in each cell types together with being involved in oocyte and granulosa cells communication. To determine the role of Dmxl2 in germ cells and in supporting cells, conditional invalidation of this gene is realized thanks to 2 transgenic lines of mice: one expressing the Cre recombinase under the control of the Vasa gene promoter in germ cells (Vasa-Cre); the other under the control of the AMH receptor II promoter in female supporting cells (Amhr2-Cre). Up to now, only mice invalidated for Dmxl2 in germ cells have been obtained. Regarding to our first results, females (Vasa-Cre; Dmxl2flox/flox) seem to be able to reproduce. However, ongoing fertility tests tend to show a lower fertility, (decreasing with age). Histological analyses of these mice ovaries at 7 weeks showed important mass cells and a few antrum follicles. Analyses at older stages are pursued. To conclude, invalidation of Dmxl2 in the germ cell line has no effect on initial follicle formation, but seems to be involved in ovarian function maintenance at adult stages.