Histone variants expression in peripheral blood mononuclear cells of patients with rheumatoid arthritis

Aim: The purpose of the present study was to analyze the expression of four histone variants, implicated in the regulation of gene expression, in peripheral blood mononuclear cell (PBMC) samples of patients with rheumatoid arthritis and healthy controls. Method: We analyzed the expression of three genes encoding histone variants H3.3, H2A.Z, macroH2A1.1 and macroH2A1.2 in PBMC samples of 50 patients with RA, diagnosed according to American College of Rheumatology (ACR) criteria, and 51 matched healthy controls using SYBR green real-time polymerase chain reaction. Mann-Whitney U-test and Spearman correlation were used for data analysis. Results: The expression of H2A.Z was increased by 1.51-fold (P < 0.001) and the expression of H3.3 was increased by 1.13-fold (P = 0.048) in PBMCs of patients with RA compared to healthy controls. Furthermore, we found a positive correlation between Disease Activity Score (DAS-28) based on erythrocyte sedimentation rate and the expression of H2A.Z. Conclusions: Given the role of H3.3 and H2A.Z in nucleosome positioning, chromatin structure and transcription regulation, we suggest that lymphocytes and monocytes, the main cell subtypes in PBMCs of RA patients, possess a more accessible chromatin.