methyl-CpG binding domain protein 3 gene [MBD3], the serotonin receptor 2B gene [HTR2B], and the NMDA receptor subtype 1 gene [GRIN1]) were hypermethylated. A specific CpG site in the HTR3A promoter region showed a significantly higher methylation level in EA cases than in EA controls after Bonferroni correction. However, this extended candidate gene study is limited by several factors: (i) the density of promoter CpGs was not high, and thus, some functionally important promoter CpGs might have been ignored; (ii) gene body CpGs were not included; and (iii) novel genes for AUD susceptibility were not considered, recapitulating the fundamental problem of candidate gene studies.
