While the investigations reported here indicate that the allele-specific effects of Supt4h knockdown reported previously in cultured cells occur also in mouse HD model systems and that reduction of Supt4h expression can result in disease-related consequences in a mouse HD model, the parameters that affect selective expression of mutant vs. wild type HTT alleles require further investigation before the clinical relevance of our findings can be established. This evidence concerns the gene SUPT4H1 and Huntington disease.