CRISPR/Cas9-mediated genetic correction reverses spinocerebellar ataxia 3 disease-associated phenotypes in differentiated cerebellar neurons.

The neurodegenerative disease spinocerebellar ataxia type 3 (SCA3; also called Machado-Joseph disease, MJD) is a trinucleotide repeat disorder caused by expansion of the CAG repeats in the ATXN3 gene. Here, we applied a CRISPR/Cas9-mediated approach using homologous recombination to achieve a one-step genetic correction in SCA3-specific induced pluripotent stem cells (iPSCs). The genetic correction reversed disease-associated phenotypes during cerebellar region-specific differentiation. In addition, we observed spontaneous ataxin-3 aggregates specifically in mature cerebellar neurons differentiated from SCA3 iPSCs rather than in SCA3 pan-neurons, SCA3 iPSCs or neural stem cells, suggesting that SCA3 iPSC-derived disease-specific and region-specific cerebellar neurons can provide unique cellular models for studying SCA3 pathogenesis in vitro. Importantly, the genetically corrected cerebellar neurons did not display typical SCA3 aggregates, suggesting that genetic correction can subsequently reverse SCA3 disease progression. Our strategy can be applied to other trinucleotide repeat disorders to facilitate disease modeling, mechanistic studies and drug discovery.