Poster abstracts
Poster number 34 submitted by Elizabeth DeLaney
Disruption of Minor Intron Splicing in Inherited Developmental Disorders
Elizabeth DeLaney (Cellular and Molecular Medicine, Lerner Research Institute), Rosemary C. Dietrich (Cellular and Molecular Medicine, Lerner Research Institute), James M. Hiznay (Cellular and Molecular Medicine, Lerner Research Institute), David E. Symer (Department of Lymphoma/Myeloma-Research, Division of Cancer Medicine, UT MD Anderson Cancer Center), Richard A. Padgett (Cellular and Molecular Medicine, Lerner Research Institute)
Abstract:
Biallelic mutations in the gene encoding the minor spliceosomal small nuclear RNA (snRNA) U4atac (RNU4ATAC) have been identified in patients with three autosomal recessive developmental disorders: microcephalic osteodysplastic primordial dwarfism type I (MOPDI), Roifman Syndrome, and Lowry-Wood Syndrome. While each disorder is pathologically distinct, common features of patients include microcephaly, skeletal dysplasia, growth retardation, and cognitive delay. MOPDI is the most severe of the three disorders, with patients exhibiting severe neurological defects and early death. 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 disease-associated RNU4ATAC mutations on minor splicing. Mutations seen in all three diseases in the 5’ stem-loop region of U4atac and those in the Sm protein binding site reduce splicing to less than 30% of the wild-type U4atac, while mutations found only in Roifman and Lowry Wood Syndromes in the Stem II base pairing region have nearly 50% splicing activity. The mechanism of the splicing defects seen with RNU4ATAC mutations varies depending on the mutation’s location. Previous work revealed that mutations to the 5’ stem-loop impair binding of essential U4atac/U6atac di-snRNP protein components and reduce U4atac/U6atac.U5 tri-snRNP formation. We further show that mutations to the Sm protein binding site and Stem II base pairing region result in reduced U4atac abundance, likely due to the mutations interfering with the recruitment of essential protein factors such as the Sm proteins and Prpf3. The wide range in the nature and severity of phenotypes in patients with RNU4ATAC mutations suggest there are likely multiple mechanisms that impair minor splicing in MOPDI and Roifman and Lowry Wood syndrome patients.
Keywords: Minor splicing, snRNA, MOPDI