The HD-associated modification of BDNF gene expression was found, in the hippocampus of female and male HD mice independent of methylation increases in the gene sequence, while there existed a pattern of sex-specific differences in the levels of methylation at individual CpG sites, suggesting that such differences might explain the differential regulation of BDNF expression in the male and female brains (Zajac et al., 2010). This evidence concerns the gene BDNF and Huntington disease.