The eye disorder associated with Graves' disease, called Graves' ophthalmopathy (GO), greatly reduces the quality of life in affected patients. Expression of the calsequestrin (CASQ1) protein in thyroid tissue may be the trigger for the development of eye muscle damage in patients with GO. We determined the prevalence of rs74123279, rs3747673, and rs2275703 single-nucleotide polymorphism (SNPs) in patients with autoimmune thyroid disorders, GO, Graves' hyperthyroidism (GH), or Hashimoto's thyroiditis (HT) and control subjects with no personal or family history of autoimmune thyroid disorders. Furthermore, we measured the concentration of the CASQ1 protein in normal and Graves' thyroid tissue, correlating levels with parameters of the eye signs, CASQ1 antibody levels, and the CASQ1 gene polymorphism rs74123279 and rs2275703.
High-quality genomic DNA was isolated from fresh blood samples, assayed for identification of rs74123279, rs3747673, and rs2275703 SNPs in CASQ1 gene by MassARRAY SNP analysis using iPLEX technology of SEQUENOM.
DNA samples from 300 patients and 106 control subjects (100 males, 306 females) with GO (n=74), GH (n=130), HT (n=96) and control subjects (n=106) were genotyped for the SNPs rs74123279, rs3747673 (n=405), and rs2275703 (n=407). The SNP rs74123279, rs3747673, and rs2275703 were identified as 1) common homozygous or wild type, 2) heterozygote, and 3) rare homozygous. Minor allele frequency for rs74123279, rs3747763, and rs2275703 were 21%, 40%, and 44%, respectively. Multiple comparisons of genotype frequency for rs74123279, rs3747763, and rs2275703 in the GO, GH, HT, and control groups showed P=0.06, 0.641, and 0.189, respectively. These results were substantiated by multiple comparison of alleles frequency for rs74123279, rs3838216, rs3747763, and rs2275703 in the GO, GH, HT, and control groups showed, P=0.36, 0.008, 0.66, and 0.05, respectively. Pairwise analysis of alleles frequency distribution in patients with GO showed significant probability for rs2275703, P=0.008.
Based on their evolutionary conservation and their significant prevalence, we suggest that CASQ1 gene SNPs rs74123279, rs3838216, and rs2275703 may be considered as genetic markers for GO.