Systemic lupus erythematosus (SLE) is an autoimmune inflammatory rheumatic disease. SLE susceptibility is affected by multiple genetic elements, environmental factors, and their interactions. We aimed in this study to statistically and functionally characterize a gene-gene interaction (epistasis) recently documented to affect SLE risk.
Two single-nucleotide polymorphisms, rs2230926 in TNFAIP3 (A20) gene and rs131654 in UBE2L3 (UBCH7) gene, were genotyped in all 3525 Korean participants, and their SLE risk association and epistasis were statistically analyzed by calculating odds ratio (OR), 95% confidence interval (CI), and P values in genotype comparisons between 1318 SLE patients and 2207 healthy controls. Furthermore, their effects on gene functions were assessed by comparatively examining separate and combined effects of TNFAIP3 and UBE2L3 knockdowns on NF-κB transcription factor activity in human cells.
SLE susceptibility is associated with TNFAIP3 rs2230926 (OR = 1.9, 95% CI 1.6-2.4, P = 8.6 × 10
A synergistic interaction between TNFAIP3 and UBE2L3 genes is observed in SLE risk, as being evident in comparison of genotype distributions between SLE patients and controls. Additionally, the synergistic gene-gene interaction is functionally validated, as TNFAIP3 reduction and UBE2L3 augment exert synergism in activation of NF-κB and subsequent induction of inflammatory cytokines. Accordingly, SLE inflammation and risk could be synergistically alleviated by TNFAIP3 upregulation and UBE2L3 downregulation.