The A allele of the intronic SNP rs80262450 in the PTPN2 gene favors the expression of the splicing isoform PTPN2.4. This cytoplasmic isoform enhances TNF-α production in myeloid cells, thereby contributing to intestinal inflammation. These findings identify PTPN2.4 as a key pathogenic regulator and potential therapeutic target for inflammatory bowel disease.
ABSTRACT
Genome-wide association studies implicate the PTPN2 gene locus (18p11.21) in risk for several autoimmune diseases, including inflammatory bowel disease. Through genetic fine mapping, we identified the single-nucleotide polymorphism rs80262450 in the PTPN2 gene as the putative causal variant. Analysis of GTEx tissue samples and genetically engineered myeloid cell lines carrying risk and nonrisk alleles of rs80262450 demonstrated increased expression of the PTPN2 splice isoform 4 (PTPN2.4), suggesting that the rs80262450 enhances disease susceptibility by favoring production of PTPN2.4. Furthermore, we found that PTPN2.4 contains a nuclear export sequence (NES) that leads to its retention in the cytoplasm. Differential localization of PTPN2.4 isoform results in a distinct protein binding profile revealed by mass-spectrometry analysis, and its overexpression increased TNF-α. PTPN2.4 knockdown reduced pro-inflammatory cytokines in human macrophages. Mutations within the NES motif abolished the unique localization and function of PTPN2.4. Lastly, increased expression of PTPN2.4 was found in Crohn’s disease tissues, demonstrating its involvement in the disease. Together, we identified the pathogenic isoform PTPN2.4 as a novel driver of intestinal inflammation and a potential target to attenuate inflammation in IBD.