and gene expression of Protocadherin alpha-7 (PCDHA7), Aquaporin-11 (AQP11), and potassium inwardly-rectifying channel, subfamily J, member 5 (CIR), all of which are involved in critical neuronal and cellular functions. Globally, among all 13,113 histone H3K4me3 peaks mapped to the promoters of hippocampal expressed genes, there was a trend of correlation between H3K4me3 and expression changes in cocaine addicts. However, this trend was not observed in alcoholics. Overall, there was no significant overlap between the genes with either significant H3K4me3 changes or expression changes in both cocaine addicts and alcoholics. This may reflect the fact that epigenetic regulation of gene expression through chromatin remodeling involves many different types of histone modifications at many different histone residues (Barski et al., 2007; Wang et al., 2008), and cocaine- and alcohol-induced expression changes are very likely the results of alterations of those many different histone modifications.
