DNA Methylation in Autoimmune Thyroid Disease

• Published in: The journal of clinical endocrinology and metabolism Vol. 108; no. 3; pp. 604 - 613
• Main Authors: Lafontaine, Nicole, Wilson, Scott G, Walsh, John P
• Format: Journal Article
• Language: English
• Published: US Oxford University Press 01-03-2023
• Subjects: Autoimmune diseases; Autoimmune Diseases - genetics; Autoimmunity; B cells; Death-associated protein kinase; DNA Methylation; Drb1 protein; Environmental factors; Epigenetic inheritance; Epigenetics; Gene expression; Genes; Genetic aspects; Genetic Predisposition to Disease; Genomes; Genomics; Graves Disease; Hashimoto Disease - genetics; Histocompatibility antigens; HLA histocompatibility antigens; Humans; Immunoregulation; Intercellular adhesion molecule 1; Interleukin 2 receptors; Iodine; Medical research; Medicine, Experimental; Methylation; Protein Tyrosine Phosphatase, Non-Receptor Type 22 - genetics; Protein-tyrosine-phosphatase; Therapeutic targets; Thyroid diseases; Thyroid hormones; Tumor necrosis factor; Australia; autoimmune diseases; DNA methylation; Graves disease; epigenome; autoimmune thyroiditis; Hashimoto disease
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/clinem/dgac664

Abstract
Graves disease and Hashimoto disease form part of the spectrum of autoimmune thyroid disease (AITD), to which genetic and environmental factors are recognized contributors. Epigenetics provides a potential link between environmental influences, gene expression, and thyroid autoimmunity. DNA methylation (DNAm) is the best studied epigenetic process, and global hypomethylation of leukocyte DNA is reported in several autoimmune disorders. This review summarizes the current understanding of DNAm in AITD. Targeted DNAm studies of blood samples from AITD patients have reported differential DNAm in the promoter regions of several genes implicated in AITD, including TNF, IFNG, IL2RA, IL6, ICAM1, and PTPN22. In many cases, however, the findings await replication and are unsupported by functional studies to support causal roles in AITD pathogenesis. Furthermore, thyroid hormones affect DNAm, and in many studies confounding by reverse causation has not been considered. Recent studies have shown that DNAm patterns in candidate genes including ITGA6, PRKAA2, and DAPK1 differ between AITD patients from regions with different iodine status, providing a potential mechanism for associations between iodine and AITD. Research focus in the field is moving from candidate gene studies to an epigenome-wide approach. Genome-wide methylation studies of AITD patients have demonstrated multiple differentially methylated positions, including some in immunoregulatory genes such as NOTCH1, HLA-DRB1, TNF, and ICAM1. Large, epigenome-wide studies are required to elucidate the pathophysiological role of DNAm in AITD, with the potential to provide novel diagnostic and prognostic biomarkers as well as therapeutic targets.