Role of the HBII-85 snoRNA cluster in the pathogenesis of PWS

It has been known for many years that loss of function of the copy of the DNA inherited from the father for genes in the Prader-Willi syndrome (PWS) region cause PWS. However, there are multiple genes in the region, and it has not been clear as to exactly which gene or genes cause PWS. Based on studies of a series of rare families with translocations, there has been increasing evidence that PWS may be caused by deficiency for a group of noncoding RNA molecules called HBII-85 snoRNAs. We recently encountered a patient with a deletion which substantially strengthens the argument that the majority of the features of PWS are caused by deficiency of the HBII-85 snoRNA cluster. Very little is known about these snoRNA genes, and the major focus of this grant is to attempt to determine the function of these genes. Based on what is known generally about snoRNA molecules, it is quite likely that these snoRNAs modify some other form of RNA to alter its function. We will use both genome-wide strategies and gene candidate strategies to try to identify the RNA molecules that presumptively are modified by the HBII-85 snoRNAs as described in more detail in the scientific portion of the application. As these new genes, which might be called targets of the snoRNAs are identified, we will study the role of each of these genes in the causation of the various aspects of the abnormalities found in PWS. This project addresses a very basic question in PWS, that is, exactly what is the molecular genetic basis of PWS? How does the gene abnormality, usually a paternal deletion, lead to the clinical findings in PWS? This is a very central question to any research regarding PWS. It is reasonable to hope that better understanding of these mechanisms would open better opportunities for treatment in PWS, particularly pharmacologic treatment that might modify gene function towards a more normal state. We believe that this kind of study has very direct and important relevance for PWS patients and their families.

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