The imprinted Snurf-Snrpn chromosomal domain contains two large arrays of 
tandemly repeated, paternally expressed box C/D small-nucleolar RNA (snoRNA) 
genes: the SNORD115 (H/MBII-52) and SNORD116 (H/MBII-85) gene clusters believed 
to play key roles in the fine-tuning of serotonin receptor (5-HT2C) pre-mRNA 
processing and in the etiology of the Prader-Willi Syndrome (PWS), respectively. 
SNORD115 and SNORD116 were recently proposed to undergo significant conversion 
into shorter RNA species, the so-called psnoRNAs. Here, we provide evidence that 
argues against the existence of abundant psnoRNAs in human or mouse brain. 
Instead, we characterize a previously unsuspected low-abundance, 
fibrillarin-associated SNORD115-derived smaller RNA species. Based on these 
findings, we strongly recommend that PWS-encoded SNORD115 and SNORD116 be 
considered as bona fide box C/D snoRNAs.