Demethylation of the FCER1G promoter leads to FceRI overexpression on monocytes of patients with atopic dermatitis

Background: Overexpression of the high-affinity receptor for immunoglobulin E on atopic monocytes and dendritic cells is known to contribute to the pathogenesis of atopic dermatitis (AD). However, it remains unclear what is the underlying mechanism of FceRI deregulation. It has been speculated that epigenetic deregulation may play a role. Methods: Global DNA methylation levels of monocytes from 10 AD patients and 10 healthy controls were measured using a global DNA methylation kit. Bisulfite sequencing was performed to determine the methylation status of the FCER1G promoter region. FceRI? mRNA and FceRI protein levels were detected by real-time RT-PCR, Western blotting, and flow cytometry, respectively. Patch methylation and the demethylating agent, 5-azacytidine, were used to determine the functional significance of methylation changes on FceRI expression. Results: Monocytes from AD patients show a global hypomethylation, as well as a locus-specific hypomethylation at FCER1G promoter, as compared to healthy controls. Furthermore, this hypomethylation of FCER1G is inversely correlated with its expression. Patch methylation in combination with luciferase reporter assay confirmed the direct relationship between methylation and expression. Moreover, treating healthy monocytes with 5-azacytidine caused a reduction in methylation levels and an induction in FceRI? transcription and surface expression of FceRI. Conclusion: Demethylation of specific regulatory elements within the FCER1G locus contributes to FceRI overexpression on monocytes from patients with AD.