[Control of the development of Onuf's spinal nucleus]

Onuf's nucleus is located at the sacral level of the spinal cord and is formed by the motoneurons innervating the perineal muscles. Both the number and the size of these neurons vary between males and females creating a so-called sexual dimorphism. This dimosphism is mediated by androgens. In absence of these hormones, the motoneurons die by apoptosis. This androgenic effect is not mediated directly on the motoneurons but on perineal muscles. These muscles survive by the action of androgens and they secrete factors that act to promote motoneuronal survival. One of these factors could be CNTF (Ciliary Neurotrophic Factor). Later during development, androgens act directly on motoneurons either by binding their own receptor or by intracellular transformation into estrogens due to the action of the aromatase.