The 10-23Dz may cleave the expanded CUG repeat in myotonic dystrophy 1 (DM1 [106]) and Fuchs endothelial corneal dystrophy (FECD [107]) at GC sites, the intronic CCUG repeat in myotonic dystrophy 2 (DM2 [108]) and GGGGCC repeat in C9orf72-amyotrophic lateral sclerosis/ frontotemporal dementia (ALS/FTD [109]) at GC sites, the CGG repeat in Fragile X–associated tremor ataxia syndrome (FXTAS [110]) and oculopharyngodistal myopathy (OPDM [111]) at GC sites, and the AU-rich repeats in SCA10 [112], SCA31 [113], and SCA37 [114] at AU sites. The gene discussed is ATXN10; the disease is myotonic dystrophy type 1.