The sex of most mammals is determined by the action of SRY. Its presence initiates testis formation resulting in male differentiation, its absence results in ovary formation and female differentiation. We have used suppression subtraction hybridisation between 12.0-12.5 days postcoitum (dpc) mouse testes and ovaries to identify genes that potentially lie within the Sry pathway. Normalised urogenital ridge libraries comprising 8,352 clones were differentially screened with subtracted probes. A total of 272 candidate cDNAs were tested for qualitative differential expression and localisation by whole mount in situ hybridisation; germ cell-dependent or -independent expression was further resolved using busulfan. Fifty-four genes were identified that showed higher expression in the testis than the ovary. One novel gene may be a candidate for interactions with WT1, based on its localisation to Sertoli cells and map position (16q24.3).

Vertebrate DM domain genes encode a novel group of proteins related to the Drosophila doublesex and Caenorhabditis elegans mab-3 transcription factors. It is shown here that the recently identified gene, DMRT3, has a restricted embryonic expression profile that is conserved in chicken and mouse embryos. DMRT3 is expressed primarily in the forebrain, neural tube and nasal placode of both species. In the chicken, DMRT3 is also expressed in newly forming tail somites at early developmental stages and, later, in the Müllerian ducts of the urogenital system.