Molecular cloning, expression of Sox5 and its down-regulation of Dmrt1 transcription in zebrafish

The doublesex and mab-3-related transcription factor 1 (Dmrt1) is the founding member of a family of DM domain genes, involved in gonadogenesis. Here we report the cloning of zebrafish Sox5 and use real time PCR to show that its expression increases while expression of Dmrt1 decreases during embryogenesis. Characterization of the proximal promoter of zebrafish Dmrt1 revealed two positive and two negative regulatory regions and a Sox5-binding site. Co-transfection of dmrt1 (with or without the Sox-binding site), driving an EGFP reporter and Sox5 showed further that Sox5 bound the Dmrt1 promoter and inhibited Dmrt1 expression. This antagonistic partnership between Dmrt1 and Sox5 suggests a potential transcriptional regulatory mechanism for Dmrt1 in early embryogenesis.