Associations of Protein Tyrosine Phosphatase Nonreceptor 22 (PTPN22) Gene Polymorphisms with Susceptibility to Graves' Disease in a Japanese Population

Background: The polymorphism of the protein tyrosine phosphatase nonreceptor 22 (PTPN22) gene, which encodes an important negative regulator of T cell activation, has been reported to be associated with susceptibility to Graves' disease (GD) in Caucasians. The objective of this study was to investigate whether PTPN22 gene polymorphisms confer susceptibility to GD and Graves' ophthalmopathy (GO) in a Japanese population.

Methods: We performed a case-control study of PTPN22 gene polymorphisms in Japanese GD patients (n = 414) and healthy control subjects with no antithyroid autoantibodies or family history of autoimmune disorders (n = 231). The G-1123C polymorphism (rs2488457) in the promoter region, Arg620Trp (C1858T) polymorphism (rs2476601) in exon 14, IMS-JST146695 polymorphism (rs3789607) in intron 19, and SNP37 (rs3789604) downstream of the PTPN22 gene were determined by polymerase chain reaction (PCR)-restriction fragment length polymorphism using restriction enzymes and direct PCR sequencing methods.

Results: None of the GD patients or control subjects had the 1858T allele of the PTPN22 gene polymorphism. The AA-genotype and A-allele frequencies of SNP37 were significantly higher in GD patients than in control subjects (A-allele frequency: p = 0.0085, odds ratio = 1.45). The genotype frequencies and allele frequencies of the G-1123C and IMS-JST146695 polymorphisms did not differ between GD patients and control subjects. The -1123G/1858C/JST146695T/SNP37C haplotype frequency was significantly lower in GD patients than in control subjects. There were no associations between PTPN22 gene polymorphisms and GO.

Conclusions: The results suggest that SNP37 of the PTPN22 gene is associated with susceptibility to GD in a Japanese population. Further studies including functional analyses are required.