In addition, overexpression studies in iPSC-derived neurons from patients with SCA1 revealed that though TGM5 was not successfully expressed, the overexpression of its paralogs TGM2 and TGM6 whose neuronal function and/or levels are well-known to contribute to polyQ-expansion disorders, such as Huntington’s disease or SCA35 (32–35), significantly increased total ATXN1 protein levels without changing mRNA levels, suggesting that TGMs regulated ATXN1 posttranslationally (Supplemental Figure 5; see complete unedited blots in the supplemental material). Here, ATXN1 is linked to Huntington disease.