Role of snoRNAs in Prader-Willi Syndrome

Principle Investigator : Stefan Stamm, Ph.D.

Department of Molecular and Cellular Biochemistry
University of Kentucky, College of Medicine

The loss of expression of small nuclear RNAs (snoRNAs) encoded in the Prader-Willi critical region on chromosome 15q11-q13 is the major molecular cause for the Prader-Willi syndrome (PWS).  They recently showed that one of the missing snoRNAs, HBII-52, changes splice site selection. Based on these findings, they identified seven more alternative splicing events that are regulated by HBII-52. One of the targets is the

corticotrophin releasing hormone receptor (CRHR1). HBII-52 promotes the production of receptors that do not transduce a corticotrophin releasing hormone/factor (CRH) signal and act in a dominant-negative way on the full-length CRHR1 receptor. Loss of CRHR1 could explain the upregulation of pro-opiomelanocortin (POMC) mRNA that has been observed in mouse models and central adrenal insufficiency observed in children with PWS.  

They propose to (1) prove that HBII-52 regulates the CRHR1 function in mice by performing correlation analysis, testing variants of HBII-52 for their influence on CRHR1 splicing and by setting up a cell system that recapitulates the CRHR1 splicing on the protein level. In the second aim, we will (2) investigate how the loss of HBII-52 function can be compensated by determining the mechanism by which HBII-52 acts on CRHR1 splicing, and by using lentivirus constructs and oligonucleotides as a substitute for HBII-52.

These findings are relevant for the PWS community, as they could explain central adrenal insufficiency on a molecular basis, set up a screening system for a library of potential compounds and finally identify therapeutic approaches 

The first aim of the project could explain the molecular basis for central adrenal insufficiency and the abnormal high POMC levels seen in PWS. The experiments will show what will be the best snoRNA candidates for substitution and the system developed can be used for high throughput screening in future work. An effective screening system is a prerequisite for further funding from the NICHD to perform high-throughput drug screening. 

As a follow up, the following was recently published in HUMAN MOLECULAR GENETICS VOLUME 19 NUMBER 7 1 APRIL 2010 PAGES 1153–1386  

The snoRNA MBII-52 (SNORD 115) is processed into smaller RNAs and regulates alternative splicing

Shivendra Kishore1,2,{, Amit Khanna1,{, Zhaiyi Zhang1, Jingyi Hui2,{, Piotr J. Balwierz3,

Mihaela Stefan4,}, Carol Beach1, Robert D. Nicholls4, Mihaela Zavolan3 and Stefan Stamm1,2,_ 

The loss of HBII-52 and related C/D box small nucleolar RNA (snoRNA) expression units have been implicated as a cause for the Prader–Willi syndrome (PWS). We recently found that the C/D box snoRNA HBII-52 changes the alternative splicing of the serotonin receptor 2C pre-mRNA, which is different from the traditional C/D box snoRNA function in non-mRNA methylation. Using bioinformatic predictions and experimental verification, we identified five pre-mRNAs (DPM2, TAF1, RALGPS1, PBRM1 and CRHR1) containing alternative exons that are regulated by MBII-52, the mouse homolog of HBII-52. Analysis of a single member of the MBII-52 cluster of

snoRNAs by RNase protection and northern blot analysis shows that the MBII-52 expressing unit generates shorter RNAs that originate from the full-length MBII-52 snoRNA through additional processing steps. These novel RNAs associate with hnRNPs and not with proteins associated with canonical C/D box snoRNAs. Our data indicate that not a traditional C/D box snoRNA MBII-52, but a processed version lacking the snoRNA stem is the predominant MBII-52 RNA missing in PWS. This processed snoRNA functions in alternative splice-site selection. Its substitution could be a therapeutic principle for PWS.