LAUSR

Background: Antidepressants have variable therapeutic effects, depending on genetic and environmental factors. Approximately 30% of major depressive disorder (MDD) patients do not respond significantly to antidepressants such as paroxetine, a selective serotonin reuptake inhibitor (SSRI). However, the biological mechanisms behind this phenomenon are mostly unknown. Here, we examined the role of patients' epigenetic background in SSRI efficacy. Methods: Genome-wide DNA methylation analysis of the peripheral blood of Japanese MDD patients was performed by using the Infinium HumanMethylation450 BeadChip. Results: We compared the results of the 10 patients who best responded to paroxetine (BR) with the 10 worst responders (WR), and found 623 CpG sites with a >10% difference in DNA methylation level. Among them, 218 sites were nominally significant between BR and WR (p < 0.05), and 2 sites (cg00594917 and cg07260927) were significantly different after false discovery rate (FDR) correction (q < 0.05). The methylation difference was greatest at cg00594917, located in the first exon of the PPFIA4 gene, which codes for liprin-α (p = 0.00012). Hierarchical cluster analysis of 23 CpG sites in the PPFIA4 gene distinguished BR and WR, except for 1 WR patient. The cg07260927 site was located in the 5′UTR of the heparin sulfate-glucosamine 3-sulfotransferase 1 (HS3ST1) gene (p = 0.00013). Hierarchical cluster analysis of 28 CpG sites in HS3ST1 distinguished BR and WR, except for 1 WR and 2 BR patients. Conclusion: Our results suggest that patients' DNA methylation profile at specific genes such as PPFIA4 and HS3ST1 is associated with individual variations in therapeutic responses to paroxetine.