ATXN3 and muscular atrophy: SCA3 is caused by 60–87 CAG repeats in the ATXN3 allele encoding a polyQ tract in the protein ataxin-3 and is expressed throughout the body and in neurons; however, mutated ataxin-3 protein causes neurotoxicity in specific brain regions in SCA3 patients, leading to progressive gait ataxia, dysarthria, dysphagia, muscular atrophy, and oculomotor dysfunction [6].