PWS is caused by the loss of paternal expression of several genes of the 15q11-q13 region, including NECDIN. Necdin protein is a member of the Mage family, with proposed functions in differentiation (Andrieu et al., 2003; Takazaki et al., 2002), migration (Kuwajima et al., 2010; Miller et al., 2009; Tennese et al., 2008), neurite growth (Liu et al., 2009; Tennese et al., 2008), axonal extension, arborization and fasciculation (Pagliardini et al., 2005), and cell survival (Aebischer et al., 2011; Andrieu et al., 2006; Kuwako et al., 2005; Tennese et al., 2008). This evidence concerns the gene NDN and Prader-Willi syndrome.