RNA-seq and cytological study of sex-specific meiosis response to Gsdf in medaka (Oryzias latipes) 

Abstract Sexually dimorphic meiosis is monitored by meiotic recombination to prevent the formation of abnormal gametes in males and females. However, the regulatory mechanism of sex-specific meiotic recombination is not completely understood. Here we report the role of gsdf, a unique BMP/TGF-b family member gene, in the regulation of meiotic recombination in medaka (Oryzias latipes) based on the RNA-seq and cytogenetic analysis of normal and gsdf deficient gametogenesis. Several differentially expressed genes, including the FKB506-binding protein 7 (fkbp7), were significantly upregulated in pubertal gsdf deficient gonads. The escalation of alternative pre-mRNA isoforms of meiotic synaptonemal complex genes including sycp3 were visualized using Integrative Genomics Viewer and confirmed by real-time qPCR. However, immunofluorescence analysis showed that Sycp3 protein products in gsdf deficient XY oocytes were significantly reduced. Transmission electron microscope observations showed that asynchronous cysts replaced normal synchronous cysts in gsdf-deficient testis. Breeding experiments revealed a skewed ratio of gsdf−/− XY gamete fertility in a non-Mendelian manner resulting in XY chromosome non-disjunction. Taken together, our observations suggest that Gsdf signaling may directly or indirectly affect meiotic recombination in the process of sex-specific division of germline stem cells.