ATXN3 and Huntington disease: In order to assess sequence diversity at the ATXN3 repeat in the SCA3 population, we adapted the high-throughput ultra-deep MiSeq sequencing assay we developed for analysing the HD-associated HTT CAG repeat (Ciosi et al. 2018; Ciosi et al. 2019) to the ATXN3 locus.