There are two nonsynonymous coding polymorphisms in the deubiquitinating (DUB) domain of TNFAIP3: F127C, which is in high-linkage disequilibrium with reported SLE-risk variants, and A125V, which has not been previously studied.
The rs2230926 allele of TNFAIP3 was associated with susceptibility to SLE in males, but after Bonferroni correction there were no significant associations with any of the other four SNPs in IRF5, BLK, TNIP1 and ETS1 genes.
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.
We show that three independent SNPs in the TNFAIP3 region (rs13192841, rs2230926 and rs6922466) are associated with systemic lupus erythematosus (SLE) among individuals of European ancestry.
The replication analysis indicates that TNFAIP3, ETS1 and TNIP1 are probably common susceptibility genes for SLE in Chinese populations, and they may contribute to the pathogenesis of multiple SLE subphenotypes.
As proof of concept, we employed TALEN (transcription activation-like effector nuclease)-mediated genome editing to specifically disrupt the TT>A enhancer region to mimic candidate causal variants identified in the systemic lupus erythematosus-associated susceptibility gene, tumor necrosis factor-α-induced protein 3 (TNFAIP3), in an isogenic HEK293T cell line devoid of other linkage disequilibrium-associated variants.
TNFAIP3 interacting protein 1, TNIP1 (ABIN-1) is involved in inhibition of nuclear factor-κB (NF-κB) activation by interacting with TNF alpha-induced protein 3, A20 (TNFAIP3), an established susceptibility gene to systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).
TNFAIP3, an RA candidate gene, flanks this region, and polymorphisms in both the TNFAIP3 gene and the intergenic region are associated with systemic lupus erythematosus.
Meta-analysis followed by replication identifies loci in or near CDKN1B, TET3, CD80, DRAM1, and ARID5B as associated with systemic lupus erythematosus in Asians.
Interestingly, some of these studies emphasized significant associations between TNFAIP3/A20 SNPs imparting decreased expression or loss of NF-kappaB inhibitory function, and susceptibility to systemic lupus erythematosus (SLE) and coronary artery disease (CAD).
In conclusion, single nucleotide polymorphisms in ITGAM, TNFSF4, TNFAIP3 and STAT4 genes are associated with susceptibility to SLE in a North Indian population.