Variations in two genes of the tumour necrosis factor (TNF) alpha pathway have been implicated in the pathogenesis of autoimmune diseases: polymorphisms in the TNFRSF1A gene, encoding TNF receptor 1, showed significant association with MS in genomewide association scans, and variation in or near the TNFAIP3 gene, coding for a negative regulator of NFkB, was associated with MS, systemic lupus erythematosus, diabetes and rheumatoid arthritis.
These findings extend our knowledge of susceptibility locus sharing across different autoimmune diseases, and provide convincing evidence that the RA/SLE locus 6q23/TNFAIP3 is a newly identified T1D locus.
Genome-wide association studies have implicated the TNFAIP3 locus in susceptibility to autoimmune disorders in European cohorts, including rheumatoid arthritis, coronary artery disease, psoriasis, celiac disease, type 1 diabetes, inflammatory bowel disease, and systemic lupus erythematosus (SLE).
In the total RA inception cohort, the HLA-DRB1 shared epitope (per-allele odds ratio (OR) = 2.1, trend P < 0.0001), PTPN22 (per-allele OR = 1.5, trend P < 0.0001), OLIG3/TNFAIP3 locus (per-allele OR = 1.2, trend P = 0.009) and TRAF1/C5 locus (per-allele OR = 1.1, trend P = 0.04) were associated with RA.
To define the contribution of A20 to rheumatoid arthritis pathology, we generated myeloid-specific A20-deficient mice and show that specific ablation of Tnfaip3 in myeloid cells results in spontaneous development of a severe destructive polyarthritis with many features of rheumatoid arthritis.
In the paper by Dieguez-Gonzalez and colleagues in the present issue of Arthritis Research & Therapy, the results of a detailed genetic investigation of the recently identified rheumatoid arthritis and systemic lupus erythematosus susceptibility region at 6q23 containing the TNFAIP3 gene are reported.
Sixty-three RA patients were included.Nine genes (13 SNPs) were subsequently analyzed, including those coding for cytokines involved in synovitis (IL10, LTA, TGFβ1, TNF-α, TNF receptor II) and genes associated with RA susceptibility (-C5 TRAF1, STAT4, TNFAIP3 and PTPN22).