SNORD115

SNORD115, also known as HBII-52, is a small nucleolar RNA (snoRNA) of the C/D box class. It is encoded within the Prader-Willi syndrome critical region on chromosome 15q11-q13 and is expressed mainly in the brain. Like other intronically encoded snoRNAs, SNORD115 is typically transcribed as part of a host gene transcript and processed from introns with paternal imprinting.

SNORD115 functions as a snoRNA; while many C/D box snoRNAs guide 2'-O-methylation of ribosomal RNA, SNORD115 is considered an orphan snoRNA with no established rRNA target. It is reported to interact with serotonin receptor 2C (HTR2C) pre-mRNA, via base pairing, and has been proposed to regulate alternative splicing and/or RNA editing of HTR2C transcripts, which could influence receptor activity in the brain. However, evidence for a robust effect in vivo has been mixed, and the precise mechanism remains unresolved.

Genomic context and evolution: SNORD115 is part of a multi-gene snoRNA cluster (HBII-52) within the imprinted region; its copy number and exact composition vary among species. It is one of several snoRNAs in the PWS region thought to contribute to neural development.

Clinical relevance: Deletions or disruptions of the paternal allele in the Prader-Willi region, including SNORD115, are associated with the features of Prader-Willi syndrome, though the syndrome reflects a combined loss of multiple paternal genes.