POST-DOCTORAL FELLOWSHIP Award

Smita Agrawal, PhD

University of Minnesota, Minneapolis, MN
Alternative Splicing in SCA1

Spinocerebellar ataxia type 1 (SCA1) is a genetic neurodegenerative disorder caused by mutation in the SCA1 gene, which encodes for the ataxin1 protein. This mutation involves the expansion of a translated CAG repeat that encodes a polyglutamine tract in ataxin1. At the
pathological level, the most common feature is the progressive degeneration of cerebellar Purkinje cells in SCA1 patients. Previous studies suggest that in addition to the expansion of the polyglutamine tract, other domains of ataxin1 are also important for development of neuropathology in SCA1, including phosphorylation of serine 776. The RNA-binding capabilities of ataxin1 and its interaction with various modulators of transcription suggest that it plays a role in RNA transcription. A recent study demonstrates that ataxin1 interacts with RBM17, an RNA splicing factor and this interaction is enhanced in the presence of mutant ataxin1. We hypothesize that this enhanced interaction of RBM17 with the mutant ataxin1 may cause changes in RNA splicing in downstream target genes, which in turn may contribute to onset of the disease. We have examined the splicing patterns of cerebellar RNA from SCA1 mutant and control mice and detected widespread changes in splicing patterns between the two transgenic mice models before pathological effects are apparent. This further strengthens our hypothesis. In this proposal, we aim to identify and validate key target genes and pathways affected due to alternative splicing before onset of SCA1 pathology due to mutant ataxin1-RBM17 interaction. To this end, we first propose to conduct a genome wide exon expression analysis on two additional well characterized SCA1 mice models in order to shortlist the candidate target genes and identify putative pathways for therapeutic targeting. These hits will then be validated using standard quantitative RT-PCR techniques and a cell based assay system that we have developed. Finally, the long-term goal of the project is to generate an RBM17 gain-of-function transgenic mouse model to further investigate the role of RBM17 in causing SCA1 pathology. The identification of genes and pathways downstream of mutant ataxin1 that might be altered due to splicing changes will provide mechanistic insights into the onset of SCA1 pathology. In addition, these genes could also become potential targets for development of SCA1 therapeutics.