Talk abstracts

Talk on Friday 03:30-03:45pm submitted by Elizabeth DeLaney

Disruption of Minor Intron Splicing in Inherited Developmental Disorders

Elizabeth DeLaney (Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute), Rosemary C. Dietrich (Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute), James M. Hiznay (Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute), David E. Symer (Department of Lymphoma and Myeloma, University of Texas MD Anderson Cancer Center), Richard A. Padgett (Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute)

Abstract:
Mutation to components of the pre-mRNA splicing machinery is a significant cause of human disease, and in particular mutations to the minor spliceosome suggest it plays a crucial role in human development. Biallelic mutations in the gene encoding the minor spliceosomal small nuclear RNA (snRNA) U4atac (RNU4ATAC) have been identified in patients with three developmental disorders: microcephalic osteodysplastic primordial dwarfism type I (MOPDI), Roifman Syndrome (RS), and Lowry-Wood Syndrome (LWS). Common features include microcephaly, skeletal dysplasia, and growth retardation. Twenty-six unique disease-causing mutations have been identified in RNU4ATAC. Current data suggests that RNU4ATAC mutations disrupt U4atac snRNA function and impair minor splicing through several mechanisms. Using our in vivo orthogonal splicing assay, we have characterized the effects of RNU4ATAC mutations on minor splicing. Mutations to the 5’ stem-loop region of U4atac and the Sm protein binding site severely reduce splicing, while mutations in the Stem II base pairing region are much more moderate. The mechanism of the splicing defects seen with RNU4ATAC mutations varies depending on the mutation’s location. Mutations to the 5’ stem-loop impair binding of essential U4atac/U6atac di-snRNP protein components and reduce U4atac/U6atac.U5 tri-snRNP formation. Mutations to the Sm protein binding site and Stem II base pairing region result in reduced U4atac abundance, likely due to interference with the recruitment of protein factors such as the Sm proteins and Prpf3. There is a wide range in both the nature and severity of phenotypes observed in patients with RNU4ATAC mutations. We observe a rough correlation when comparing the degree of the splicing defect measured for individual mutations in our assay and the overall severity of the phenotype reported in patients. Collectively, our data suggests there are likely multiple mechanisms that impair minor splicing in MOPDI, RS, and LWS patients.

Keywords: Minor splicing, snRNA, MOPDI