Indeed, genes that were down-regulated in CAG-expanded and in HTT KO eCNs, such as RFC2, THBS1, HAT1, PHF6, IPO7, and COG7, were previously found to be associated with reduced neuronal survival upon knockdown, suggesting that these genes may have a role in HD-associated neurodegeneration (Fig. 6E). This evidence concerns the gene HAT1 and Huntington disease.