DMRT1 and Decreased testicular size: In humans, DMRT1 is located on 9p24.3 in a small cluster with the related genes DMRT2 and DMRT3. Large terminal deletions of 9p are a known cause of syndromic XY sex-reversal, and although the role of the DMRT genes in the 9p deletion syndrome phenotype has not yet been defined, mouse experiments have shown that homozygous deletion of DMRT1 causes severe testicular hypoplasia [38], [39], [40].