Influence of HumDN1 VNTR polymorphism on DNASE1 expression in systemic lupus erythematosus and rheumatoid arthritis.

The purpose of this study was to analyze the effect of the HumDN1 VNTR polymorphism on DNASE1 mRNA expression and enzyme activity in lupus (SLE) and rheumatoid arthritis (RA) compared to healthy control (HC). Kuwait subjects (n = 500) matched by age/gender/ethnicity were genotyped by fragment-analysis. DNASE1 expression was analysed using quantitative Real-Time-PCR and sera from subjects were screened for DNase1 reduction activity by ELISA. Allele and genotype distribution of HumDN1 VNTR revealed a significant association with susceptibility to SLE and RA (p < 0.05, OR > 1). Relative expression analysis revealed a significant increase in DNASE1 mRNA in SLE (p = 0.0001) and RA (p = 0.002) compared to HC. Stratification of subjects revealed, increased DNASE1 expression in SLE with 5/5 (p = 0.0001), 3/4 (p = 0.0001) and 3/5 genotype (p = 0.01). A reduction in DNASE1 expression was specifically observed in SLE with 4,4 genotype (p = 0.0004). RA patients with 3/4 genotype (p = 0.02) showed a significant increase in DNASE1 expression. Similarly a significant association was observed between DNase1 reduction activity and SLE (p = 0.0001). SLE patients with 3,4 (p = 0.0001) and 5,5 genotype (p = 0.0001) showed increased DNase1 reduction activity, while a lack of association was observed with RA. The present study is the first to reveal the effect of HumDN1 VNTR on DNASE1 expression in SLE and RA.