Evaluation of RNA trans-splicing as a therapeutic strategy for spinocerebellar ataxia, type 1

This project will evaluate the therapeutic potential of spliceosome-mediated RNA trans-splicing (SMaRT) for the treatment of spinocerebellar ataxias (SCAs). SMaRT is an RNA-based gene therapy that creates a hybrid mRNA through a trans-splicing reaction between a target pre-mRNA and an exogenous pre-trans-splicing molecule (PTM). Our hypothesis is that a SCA-causing protein can be converted into a non-toxic form by SMaRT. SCA1, caused by an expanded polyglutamine tract in the protein ataxin-1, will be used as a prototypic system. Ataxin-1 phosphorylation at S776 is critical for its neurotoxicity and acts synergistically with the polyglutamine sequence in the pathogenic mechanism. To test our hypothesis, we will use trans-splicing to substitute S776 for alanine in SCA1 patient-derived fibroblasts and SCA1 hiPSC-derived neurones. PTMs will be delivered using lentiviral transduction. The time course of ataxin-1 reprogramming will be established. Ataxin-1 reprogramming will be demonstrated biochemically and the association of reprogrammed ataxin-1 with functional protein complexes analysed. The pathological phenotypes of SCA1 hiPSC-derived neurones will be assessed and correlated with biochemical parameters. Our project aims to provide the first demonstration that a S776A mutation can alleviate SCA1 pathophysiology in patient-derived cells and validate SMaRT as a realistic therapeutic strategy for SCA1 and other spinocerebellar ataxias.

Spinocerebellar ataxia type 1 (SCA1) is caused by an expansion in a region of the ATXN1 gene. The ATXN1 gene contains instructions used to produce the ataxin-1 protein, which in SCA1 also contains an expanded region. In SCA1, the expanded region of the ataxin-1 protein interacts with another part of the protein. Research has suggested that it is this interaction which starts a toxic chain of events, eventually leading to the symptoms of SCA1.

We are testing a method by which this interaction can be prevented, by altering the part of the protein involved. The method is called SMaRT, and is a version of gene therapy. We will test the SMaRT method on skin cells taken from people with SCA1, which can be reprogrammed in the laboratory to resemble brain cells. This project will demonstrate whether preventing this interaction can prevent the toxic events which lead to SCA1 occurring in these cells, and validate the SMaRT method as a realistic therapeutic strategy for SCA1 and other ataxias.