Brain gene makes a female develop as a male

Australian scientists have discovered that changes to a gene involved in brain development can lead to testis formation and male genitalia in an otherwise female embryo. Lead researcher Professor Andrew Sinclair of the University of Melbourne and the Murdoch Childrens Research Institute said the breakthrough would improve diagnosis and clinical management of patients with disorders of sex development (DSD). These conditions occur when the testes or ovaries do not develop properly in the embryo, causing genital abnormalities in one in 4500 babies. The gene, called SOX3, sits on the X chromosome and is normally involved in the development of the central nervous system and the brain's pituitary gland. But, scientists found that mutations affecting the SOX3 gene caused it to be abnormally turned on in the embryonic gonad, leading to testis development in human DSD patients and mice. In males, testis development is regulated by an almost identical gene on the Y chromosome known as SRY. Females have two X chromosomes and therefore do not have an SRY gene.