Nuclear localization, DNA binding and restricted expression in neural and germ cells of zebrafish Dmrt3

Background information. The DM (doublesex and male aberrant-3) genes implicated in sexual development in diverse metazoan organisms have been proved to be involved in development of non-gonadal tissues. The aim of the present study was to identify and characterize Dmrt3 (DM-related transcription factor 3) of zebrafish. Results. Zebrafish Dmrt3 has a conserved DMA domain, besides a common DM domain, which clustered it into the DMRTA subfamily. During embryogenesis, Dmrt3 expression increases gradually to a high level at pharyngula stage, which is restricted to the olfactory placode and the neural tube. In the juvenile zebrafish, the gene expression is first detected in undifferentiated gonad on 17 dpf (day post-fertilization). In adult, Dmrt3 is expressed only in the developing germ cells of both gonads, mainly in spermatogonia, spermatocytes and developing oocytes. The Dmrt3 has a functional NLS (nuclear localization signal) K-41 GHKR(45) within the DM domain, which ensures that Dmrt3 exerts its role in the nucleus. Moreover, EMSA (electrophoretic mobility-shift assay) indicates that the Dmrt3-derived DM polypeptide binds to similar sites of both targets of DSX (doublesex) and MAB-3 (male aberrant-3). Conclusion. These results suggest that as a DNA-binding protein, zebrafish Dmrt3 may function in the nucleus as a potential transcription factor to exert potential roles in the development of the olfactory placode, the neural tube and germ cells.