Effect of MPG Gene rs2858056 Polymorphism, Copy Number Variation, and Level of Serum MPG Protein on the Risk for Rheumatoid Arthritis

OBJECTIVE: This study examined the role of SNP rs2858056 of the MPG gene on the incidence and severity of rheumatoid arthritis (RA). METHODS: This cohort study enrolled 365 RA patients and 375 age- and gender-matched healthy controls, all of whom had Han Chinese ethnicity and were from Taiwan. Gene polymorphism of the SNP rs2858056 of MPG was determined from genomic DNA. Allelic frequencies and genotypes were compared among cases and controls. Quantitation of rs2858056 copy number variation (CNV) was determined. Serum samples from RA patients and controls were analyzed to determine serum levels of MPG. The relationship between rs2858056 polymorphism and clinical manifestations of RA was evaluated. RESULTS: Our results indicated a statistically significant difference in genotype frequency distributions at rs2858056 for RA patients and controls (p = 0.05) and a significant difference in allelic frequency in patients and controls (p = 0.04). Furthermore, there was a significantly greater level of serum MPG protein in patients than controls (p < 0.001). However, the cases and controls had no significant differences in MPG CNV (p = 0.12). We also did not detect any association of the MPG rs2858056 with rheumatoid factor (RF), extraarticular involvement, or bone erosion in the RA patients. CONCLUSION: Our study suggests that RA is associated with a polymorphism in the MPG gene (rs2858056) and increased serum level of the MPG protein.