When we investigated the expression of genes containing CAG repeats such as ATXN1, ATN1, ATXN3, ATXN7, CACNA1A, and TBP in human HD fibroblasts, the expression of the genes was significantly reduced by Cas9-sgRNA treatment, but not by dCas9-sgRNA treatment. Here, ATXN1 is linked to Huntington disease.