Abstract
Sex hormones are a major factor responsible for the development of sex differences. Steroidogenic factor 1 (SF-1) is a key regulator of gonadal and adrenal development, and SF-1 knockout mice (SF-1 KO) are born without gonads and adrenal glands. Consequently, these mice are not exposed to gonadal sex steroids. SF-1 KO pups die shortly after birth due to adrenal deficiency. In the present study, SF-1 KO mice were rescued by neonatal corticosteroid injections followed by adrenal transplantations on day 7-8 postnatally. Control mice received corticosteroid injections and were gonadectomized prior to puberty. Mice were observed interacting with ovariectomized hormone primed females and gonad-intact males. In the absence of sex steroid replacement, adult SF-1 KO mice were significantly more aggressive than control mice in tests with stimulus females. After testosterone treatment, control males displayed significantly more aggression towards male intruders than control female mice, or male and female SF-1 KO mice, suggesting a developmental role of gonadal hormones in the expression of aggressive behavior and affirming SF-1 KO mice as a behavioral model to investigate affects of fetal gonad deficiency.