SNRPN and Prader-Willi syndrome: PWS patients lack the locus 15q11.2–q13.1 containing the SNRNP Upstream Reading Frame-Small Nuclear Ribonucleoprotein Polypeptide N (SNURF-SNRPN) gene, which hosts six SNORDs (SNORD107, SNORD64, SNORD108, SNORD109a, SNORD115 and SNORD116), the deleterious effects being driven by the absence of SNORDs.