CYP17A1 and Infertility: As previously reported [35], all homozygous mice produced by hybridization of heterozygous mice (created by TALEN) were infertile due to gonadal developmental defects, parts of them were Y chromosome-positive and the XY knockout mice had a female appearance (external genital phenotype) (Additional file 1: Fig. S6A), resembling the phenotype of human CYP17A1 deficiency, leading to 46 XY differences/disorders of sex development.