Identification of functional missense single-nucleotide polymorphisms in TNFAIP3 in a predominantly Hispanic population.

Abstract

Tumor necrosis factor alpha-induced protein 3 (TNFAIP3) is a multifunctional ubiquitin binding and editing enzyme that regulates inflammation. Genetic studies have implicated polymorphisms within the TNFAIP3 locus to the development of numerous immune-related diseases. This study evaluated the frequencies of single nucleotide polymorphism (SNPs) within the exonic regions of the TNFAIP3 gene and an associated point mutation from the Illumina array among a predominantly Hispanic cohort. Genomic DNA was obtained from 721 participants and sequencing of all TNFAIP3 exons and an intergenic point mutation (rs6920220) was performed. In vitro functional assessment was performed by transfecting mutated TNFAIP3 constructs into TNFAIP3 knockout cells containing the NF-kB luciferase reporter and stimulating with TNFα. Comparative statistics were performed with Student's t-test for continuous variables and Chi-squared test for categorical variables. Sequencing revealed two missense SNPs, rs146534657:A>G and rs2230926:T>G, both within exon 3 of TNFAIP3, which encodes the protein's deubiquitinating enzymatic domain. Frequencies of all three point mutations differed significantly across racial groups (χ2-test, P=0.014 to P<0.001). Compared to Caucasians, rs146534657:A>G was overrepresented among Hispanics (odds ratio (OR) [95% CI] 4.05 [1.24-13.18]), and rs2230926:T>G was more prevalent among African Americans (OR [95% CI] 3.65 [1.58-8.43]). In vitro assays confirm rs146534657:A>G and rs2230926:T>G decrease the ability of TNFAIP3 to abrogate NF-κB activation by 2-fold (P<0.01) and 1.7-fold (P<0.01), respectively. This study reports the frequency of rs146534657:A>G among Hispanics and is the first to evaluate its potential physiologic impact, establishing a basis for future research as a potential biomarker among this population.