Rbpms2 promotes female fate upstream of the nutrient sensing Gator2 complex component, Mios
Reproductive success relies on proper establishment and maintenance of biological sex. In many animals, including mammals, the primary gonad is initially ovary in character. We previously showed the RNA binding protein (RNAbp), Rbpms2, is required for ovary fate in zebrafish. Here, we identified Rbpms2 targets in oocytes(Rbpms2-bound oocyte RNAs; rboRNAs). We identify Rbpms2 as a translational regulator ofrboRNAs, which include testis factors and ribosome biogenesis factors. Further, genetic analyses indicate that Rbpms2 promotes nucleolar amplification via the mTorc1 signaling pathway, specifically through the mTorc1-activating Gap activity towards Rags 2 (Gator2) component, Missing oocyte (Mios). Cumulatively, our findings indicate that early gonocytes are in a dual poised, bipotential state in which Rbpms2 acts as a binary fate-switch. Specifically, Rbpms2 represses testis factors and promotes oocyte factors to promote oocyte progression through an essential Gator2-mediated checkpoint, thereby integrating regulation of sexual differentiation factors and nutritional availability pathways in zebrafish oogenesis. Overall design: To determine the RNA targets of Rbpms2, we generated wildtype female zebrafish expressing Rbpms2-mApple or mApple alone fusion proteins exclusively in the germline. Immunoprecipitation was performed in 2 adult female ovaries per transgene. Crosslinked and uncrosslinked samples for Rbpms2-mApple expressing fish and crosslined and uncrosslinked samples for mApple expressing fish were sequenced. RNAs found in the Rbpms2-mApple crosslinked and the mApple crosslinked and uncrosslinked datasets that were also present in the Rbpms2-mApple uncrosslinked dataset were excluded. RNAs present only in the uncrosslinked datasets were counted as RNA targets of Rbpms2. To characterize the transcriptional differences of rbpms2 mutants vs wildtype fish prior to sex determination (21 days post fertilization), we performed bulk RNA sequencing on n=3 21 dpf wildtype and n=3 rbpms2 mutant fish. DESeq was then performed for Differential Gene Expression Analysis.