The DMRT (doublesex and mab-3 related transcription factor) genes encode a large family of transcription factors that are related to the Drosophila doublesex proteins. Expressed primarily in the gonads, DMRT proteins contain cysteine-rich DNA-binding motifs and are thought to play an important role in sexual development. DMRT3 (doublesex and mab-3 related transcription factor 3), also known as DMRTA3, is a 472 amino acid protein that contains one DM DNA-binding domain and belongs to the DMRT family. Localized to the nucleus, DMRT3 is expressed specifically in testis and is thought to regulate transcriptional events during early sexual development. The gene encoding DMRT3 maps to human chromosome 9, which houses over 900 genes and comprises nearly 4% of the human genome. Hereditary hemorrhagic telangiectasia, which is characterized by harmful vascular defects, and Familial dysautonomia, are both associated with chromosome 9. Notably, chromosome 9 encompasses the largest interferon family gene cluster.