Abstract
Graves’ disease (GD) is an autoimmune oligogenic disorder with a strong hereditary component. Several GD susceptibility genes have been identified and confirmed during the last two decades. However, there are very few studies that evaluated susceptibility genes for GD in specific geographic subsets. Previously, we mapped a new locus on chromosome 3q that was unique to GD families of Italian origin. In the present study, we used association analysis of single-nucleotide polymorphism (SNPs) at the 3q locus in a cohort of GD patients of Italian origin in order to prioritize the best candidates among the known genes in this locus to choose the one(s) best supported by the association. DNA samples were genotyped using the Illumina GoldenGate genotyping assay analyzing 690 SNP in the linked 3q locus covering all 124 linkage disequilibrium blocks in this locus. Candidate non-HLA (human-leukocyte-antigen) genes previously reported to be associated with GD and/or other autoimmune disorders were analyzed separately. Three SNPs in the 3q locus showed a nominal association (p < 0.05): rs13097181, rs763313, and rs6792646. Albeit these could not be further validated by multiple comparison correction, we were prioritizing candidate genes at a locus already known to harbor a GD-related gene, not hypothesis testing. Moreover, we found significant associations with the thyroid-stimulating hormone receptor (TSHR) gene, the cytotoxic T-lymphocyte antigen-4 (CTLA-4) gene, and the thyroglobulin (TG) gene. In conclusion, we identified three SNPs on chromosome 3q that may map a new GD susceptibility gene in this region which is unique to the Italian population. Furthermore, we confirmed that the TSHR, the CTLA-4, and the TG genes are associated with GD in Italians. Our findings highlight the influence of ethnicity and geographic variations on the genetic susceptibility to GD.
Highlights
Graves’ disease (GD) is one of the most common autoimmune endocrine disorders characterized by goiter, hyperthyroidism and, in 10–25% of patients, ophthalmopathy [1, 2]
We studied 333 Caucasian patients with GD of Italian origin
The inheritance of GD is complex, involving multiple genes with variable penetrance, and environmental and epigenetic factors play a critical role in the etiology of the disease [5, 43, 44]
Summary
Graves’ disease (GD) is one of the most common autoimmune endocrine disorders characterized by goiter, hyperthyroidism and, in 10–25% of patients, ophthalmopathy [1, 2]. Several susceptibility genes for Graves’ ophthalmopathy have been proposed over the years based on small case–control association studies. These include CTLA-4, tumor necrosis factor-α (TNF-α), intercellular adhesion molecule-1 (ICAM-1), interferon-γ (IFN-γ) [8], insulin-like growth factor-1 receptor (IGF-1R) [9], suppressor of cytokine signaling 3 (SOCS3) [10], thyroid peroxidase (TPO) [11], calsequestrin 1 (CASQ1) [12], cysteine-rich angiogenic inducer 61 (CYR61), zinc finger protein 36 C3H type homog mouse (ZFP36), and stearoylcoenzyme A desaturase (SCD) [13]. None of the Graves’ ophthalmopathy specific genes have been confirmed
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