Changes in the DNA Methylation and Hydroxymethylation Status of the Intercellular Adhesion Molecule 1 Gene Promoter in Thyrocytes from Autoimmune Thyroiditis Patients

Abstract

The intercellular adhesion molecule 1 (ICAM1) gene is not expressed in normal thyroid tissue but was shown to be expressed in the thyroid tissue of autoimmune thyroiditis (AIT) patients. This study aimed to explore whether the DNA methylation and hydroxymethylation status of the ICAM1 promoter are aberrantly altered in the thyroid cells of AIT patients and whether this change is associated with dysfunctional expression of ICAM1. A total of 35 AIT patients and 35 sex- and age-matched controls were studied. After the isolation of thyrocytes via density-gradient centrifugation, ICAM1 mRNA expression was measured using real-time PCR. The DNA methylation and hydroxymethylation status were assessed using quantitative PCR following T4 β-glucosyltransferase treatment and MspI/HpaII cleavage at -937 bp, -701 bp, -226 bp, and -65 bp upstream of the transcription start site (TSS). The DNA methylation level was verified via pyrosequencing. The AIT group showed increased DNA hydroxymethylation at -937 bp and -226 bp and decreased methylation at -937 bp, -701 bp, and -226 bp upstream of the TSS. Pyrosequencing also revealed DNA hypomethylation at -708 bp, -692 bp, -690 bp, and -688 bp upstream of the TSS. The DNA methylation status at -708 bp, -692 bp, and -226 bp upstream of the TSS was negatively associated with ICAM1 mRNA expression. In summary, we identified aberrant DNA methylation and hydroxymethylation of the ICAM1 gene promoter in the thyrocytes of AIT patients. This aberrant epigenetic modification is associated with increased expression of the ICAM1 gene.