regions of the α-synuclein SNCA gene (Bonsch et al. 2005), the homocysteine induced endoplasmic reticulum protein HERP gene (Bleich et al. 2006), and the vasopressin AVP gene (Hillemacher et al. 2009) and decreased methylation of the promoter region of the atrial natriuretic peptide gene ANP (Hillemacher et al. 2009) in alcoholics. In women, but not men, overall DNA methylation of the monoamine oxidase A MAOA gene promoter was found to be associated point-wise with nicotine dependence and alcohol dependence (Philibert et al. 2008). Maternal cocaine exposure in mice caused decreased global methylation at P3 and increased global methylation at P30 in hippocampal pyramidal neurons (Novikova et al. 2008) and caused increased methylation of the protein kinase C epsilon (PKCε) PRKCE gene promoter (Zhang et al. 2007). Several genes that were linked to a change in methylation had their expression increased or decreased by as much as 19-fold.
