Single Nucleotide Polymorphism rs 2476601 of PTPN22 Gene and Susceptibility to Rheumatoid Arthritis in Iranian Population

The rs2476601 (R620W, C1858T) polymorphism in PTPN22 gene has been repeatedly reported to be associated with rheumatoid arthritis (RA). The rs 2476601 is widely suggested for predictive testing and risk assessment for RA. The aim of this study was to test the possible association of this SNP with RA in Iranian population. A total of 872 samples (405 confirmed RA patients and 467 healthy controls) were recruited in this study. Genomic DNA was extracted from whole blood and the genotyping was performed by polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP). Genotyping for a set of samples were re-confirmed by two other rounds of genotyping, using another PCR-RFLP experiment with different enzyme and DNA sequencing. All 872 samples were genotyped as homozygous CC in first round of genotyping. Genotyping was repeated for 30% of samples by another restriction enzyme and for 10% of samples by sequencing. Again all samples showed homozygous CC genotype.This study suggests that the rs2476601 polymorphism of PTPN22 gene is mono-morphic in Iranian population, containing only C allele. Considering that previous studies in other populations reported the T allele as the risk allele at this locus, the present study concluded that rs2476601 play no role in susceptibility to RA and other autoimmune diseases in Iranian population. This finding has significant future clinical implications in determining the strategy for risk assessment and predictive testing for such diseases in Iranian population.