Researchers describe the birth of a girl with the XY male karyotype, who has a completely normal female phenotype, including uterus and histologically normal ovaries. In mice with a similar phenotype, ablation of the M33 gene, an ortholog of Drosophila Polycomb, causes male-to-female sex reversal. Analysis of the human homolog of M33 (that is, the CBX2 gene) in this girl revealed a loss-of-function mutation in the CBX2 gene. This research was reported in an advance online article in the American Journal of Human Genetics. [AJHG abstract]Login Or Register To Read Full Story