Recently the results of multiple, well powered, genetic case-control studies have begun to appear providing convincing statistical evidence for at least ten non-HLA related risk genes or loci (C5/TRAF1, CD40, CTLA4, KIF5A/PIP4K2C, MMEL1/TNFRSF14, PADI4, PRKCQ, PTPN22, STAT4, and TNFAIP3/OLIG3) for RA and six (IL12B, IL13, IL23R, STAT2/IL23A, TNFAIP3, and TNIP1) for psoriasis.
Recently, the results of multiple well-powered genome-wide association studies have identified several additional loci outside the major histocompatibility complex region associated with psoriasis risk, including three genes involved in interleukin (IL)-23 signaling (IL-23R, IL-23A, IL-12B), two genes that regulate nuclear factor-kappaB signaling (TNIP1, TNFAIP3), and two genes involved in the modulation of T-helper type 2 immune responses (IL-4, IL-13).
More recently, analysis of psoriasis genome-wide association studies in a PsA subgroup has also implicated IL23A, TNFAIP3, and TNIP1 genetic variants as conferring risk to PsA.
We identified six new susceptibility loci associated with psoriasis in the Chinese study containing the candidate genes ERAP1, PTTG1, CSMD1, GJB2, SERPINB8 and ZNF816A (combined P < 5 × 10⁻⁸) and replicated one locus, 5q33.1 (TNIP1-ANXA6), previously reported (combined P = 3.8 × 10⁻²¹) in the European studies.
Psoriasis and psoriatic arthritis fall into this disease spectrum, with the largest region of susceptibility coming from the MHC (most likely HLA-C, ie, C*06:02 although additional influences are also being implicated), and most of the other genetic susceptibility coming from genes involved in cytokine production, specifically genes in the Th17 pathway (IL-12B, IL-23A and IL-23R, the latter, like in AS, not seen in Asians), genes in the nuclear factor κB pathway (TNFAIP3 and TNIP1) and genes in the Th2 pathway (IL-4 and IL-13).
A growing number of references have implicated TNIP1 through GWAS and expression studies in chronic inflammatory diseases such as psoriasis and rheumatoid arthritis, although TNIP1s exact role has yet been determined.
This study provides empirical evidence for the gene-environment interactions between TNIP1/ANXA6 and alcohol use, CSMD1 and cigarette smoking, highlighting the importance of gene-environment interactions in the pathogenesis of psoriasis.
After our first psoriasis genome-wide association study, we designed a custom genotyping array to fine-map eight genome-wide significant susceptibility loci known at that time (IL23R, IL13, IL12B, TNIP1, MHC, TNFAIP3, IL23A and RNF114) enabling genotyping of 2269 single-nucleotide polymorphisms (SNPs) in the eight loci for 2699 psoriasis cases and 2107 unaffected controls of European ancestry.
Thus, the data suggested that HCP5, TNIP1 and TNFAIP3 may play a role in common pathogenic of psoriasis in Chinese and confer risk factors for psoriasis in various ethnic populations.
In addition, we show that the MHC and TNIP1 regions are significantly different in patients with psoriasis onset before the age of 40 (type I) compared to after 40 years of age (type II).
We further identified previously unreported pleiotropic alleles with opposing effects on atopic dermatitis and psoriasis risk in PRKRA and ANXA6/TNIP1.
Strong additive effects when combining HLA-C*06 with IL23A, IL23R, IL12B, NFKB1 or TNIP1 were restricted to the severe cohort, indicating that activation of these pathways may influence disease severity in psoriasis.
Based on previous studies suggesting a role for TNIP1 in modulating cancer cell growth, we investigated its role in keratinocyte proliferation, which is clearly abnormal in psoriasis.
Thus, our results suggest that TNFAIP3 (rs610604) and TNIP1 (rs17728338) polymorphisms confer increased risk of psoriasis and may play a vital role in its pathogenesis in our ethnic South Indian Tamils.
The association between tumor necrosis factor-alpha induced protein 3 interacting protein 1 (TNIP1) gene and psoriasis was confirmed in people with multiple ethnicities.