Noncoding RNAs at the heart of the imprinted Prader-Willi and Angelman syndrome locus

Title Noncoding RNAs at the heart of the imprinted Prader-Willi and Angelman syndrome locus
Lecturer Dr. Janine LaSalle( Medical Microbiology and Immunology, UC Davis Genome Center, University of California Davis)
Language English
Date&Time 11/22/2016 (Tue) 13:30~14:30
Venue 大セミナー室
Detail Prader-Willi syndrome (PWS) is a neurodevelopmental disorder with a known genetic etiology, but a complex epigenetic basis. PWS is an imprinted disorder, meaning that genes expressed only on the paternal but not the maternal chromosome 15q11-q13 region are causative. Furthermore, unlike genetic mutations that affect protein-coding genes, the smallest genetic deletions causing PWS only affect noncoding transcripts of RNA. At the heart of the minimally deleted region in PWS are differently processed functional noncoding RNAs. First, the SNORD116 small nucleolar RNAs (snoRNAs) localize to the nucleolus in maturing neurons and impact rRNA and nucleolar maturation. Second, the host gene exons (116HG) surrounding the SNORD116 snoRNAs are spliced and nuclear retained as a long noncoding RNA (lncRNA), forming a large RNA cloud-like structure that regulates diurnally expressed transcription and metabolism. The intronic sequences with high GC skew form DNA:RNA hybrid structures called R-loops that promote chromatin decondensation and slow transcriptional progression of the antisense transcript to the Angelman syndrome (AS) gene UBE3A. To understand the processing, localization, and functional relevance of each component of SNORD116, we engineered novel transgenic mice to test complementation of the PWS mouse model, Snord116del. Complete transgene wild-type (Ctg/WT) mice carrying all of the elements of the Snord116 repeat were generated and bred to Snord116del males to produce mice deficient for endogenous paternal Snord116 but expressing the transgene (Ctg/Snord116del). RNA fluorescence in situ hybridization (FISH) analysis of brain showed that spliced 116HG RNA localized in a distinct cloud at its decondensed transcription site and mature snoRNAs localized to the nucleolus in wild-type (WT) but not Snord116del neurons. In non-neuronal Ctg/WT tissues and all Ctg/Snord116del tissues, no 116HG RNA cloud or snoRNAs were detected, but in Ctg/WT neurons, nucleolar snoRNAs were increased and a significantly larger single 116HG RNA cloud was detected, suggesting that processing and localization of the transgene requires the presence of an active endogenous Snord116 locus. qRT-PCR analysis demonstrated that splicing of the Snord116 transgene was largely restricted to neuronal tissues of both Ctg/WT and Ctg/Snord116del mice, despite widespread expression from the CMV promoter in many tissues. These combined results suggest that processing of the Snord116 transcript is dependent on neuronal-specific splicing factors and/or chromatin states, including the decondensed Snord116 paternal allele. Understanding how DNA-RNA interactions mediate the processing and localization required for Snord116 function and phenotypic rescue is critical for the development of effective PWS therapies in the future.
Contact 神経システム生物学
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