MAGE family member L2Prader-Willi syndrome (PWS) is manifested by neonatal hypotonia, developmental delay and childhood-onset obesity. Necdin (NDN), a gene involved in the terminal differentiation of neurons, has been implicated as one of the genes responsible for the etiology of PWS. The MAGEL2 gene is structurally similar to NDN, is localized to the PWS chromosomal region and paternally imprinted, and therefore it has a possible role in PWS. This evidence concerns the gene NDN and Prader-Willi syndrome.