NDN and Prader-Willi syndrome: Numerous disease symptoms in PWS and AS cases, irrespective of the involvement of the same segment, lie in the fact that PWS is caused by the deletion of specific paternally expressed genes like MAGEL2, MKRN3, PWRN1, NDN, C15orf 2, SNURF-SNRPN, and other snoRNA genes.