Furthermore, p21Cip1-activated kinase 3 (Pak3), which is associated with non-syndromic mental retardation in humans [39], and Musk, a receptor tyrosine kinase that plays a role in neuromuscular junction organization [40], were found to be covalently conjugated to NEDD8 in vivo (Fig. 5B). The gene discussed is NEDD8; the disease is Intellectual disability.