The first approach is to use animal models to validate DNA methylation/gene expression alterations observed in AUD subjects. For instance, following the finding that a CpG site in the promoter region of HTR3A was hypermethylated in the peripheral blood of AUD subjects,100 our research group used the DID mouse model to validate the finding from human AUD subjects.96 We also observed increased methylation levels of Htr3a promoter CpGs in the blood of mice exposed to alcohol. Moreover, we observed altered methylation levels of Htr3a promoter CpGs in reward-related brain regions (elevated in the hippocampus but reduced in the dorsomedial striatum and the dorsomedial prefrontal cortex) of alcohol drinking mice. Additionally, we found that Htr3a promoter methylation levels were inversely correlated with Htr3a expression levels in specific brain regions such as the dorsomedial striatum. Nevertheless, particular caution must be taken when extrapolating from the mouse findings because the promoter DNA sequence of human HTR3A and mouse Htr3a are not homologous.
