In various vertebrate species, including fish, amphibians, reptiles, birds and mammals, the DMRT1 gene is a master sex regulator, working to develop and maintain ‘maleness’ -either the sex cells (or germline) into testis and/or maintaining masculinization throughout the other cells in the body (i.e., Latin for soma, or somatic cells). But little is known about the how the DMRT1 gene is turned on and off in vertebrate testicular somatic cells or germ cells.