MIRSNP rs2910164 of miR-146a is associated with the muscle involvement in polymyositis/dermatomyositis

Background Recently, single nucleotide polymorphisms (SNPs) located in microRNAs, the so-called MIRSNPs, have attracted attention for their possible involvement in the pathogenesis of various diseases. Such MIRSNPs may have a functional role, due to the alteration of microRNA function, and can be a disease marker. In this study, we evaluated the possibility that MIRSNP rs2910164 in miR-146a can be a useful marker for the diagnosis and evaluation of disease activity of polymyositis/dermatomyositis (PM/DM). Methods DNA was obtained from 25 patients with DM, 16 with clinically amyopathic DM, and three with PM, and genotyped by polymerase chain reaction (PCR). The PCR products were digested by MnlI, and the digested products were run out on a 3% agarose gel. Serum levels of miR-146a were measured by real-time PCR. Results We could not find a significant difference in the frequency of genotype distribution between controls and patients with PM/DM. However, the frequency of muscle weakness and dysphagia in patients with CC genotype was significantly higher as compared with patients with CG or GG genotype. In addition, the minimum free energy between miR-146a and its complementary strand with G allele is estimated at -26.8kcal/mol, while that of C allele is at -24.0kcal/mol, suggesting that the MIRSNP rs2910164 is functional. Serum miR-146a levels tended to be decreased in patients with DM with the CC genotype. Conclusions Taken together, miR-146a may be involved in the pathogenesis of PM/DM, and patients with the CC genotype are at higher risk of muscle involvement.