Evaluation of the IRF-2 gene as a candidate for PSORS3.

Type 1 interferon can trigger flares of psoriasis. Hypersensitivity to type 1 interferon signaling causes a psoriasis-like skin disease in mice deficient for the transcription factor interferon regulatory factor 2 (IRF2). The human IRF2 gene is located at a previously identified candidate psoriasis susceptibility locus on chromosome 4q (PSORS3 at D4S1535). Therefore, we tested association of psoriasis with IRF2. We generated a sample consisting of 157 families with a total of 521 individuals. Five novel microsatellite markers were developed and typed, and complemented with three known markers to yield a set of eight markers spaced within 600 kb around the IRF2 gene, three of which are located in the gene. We detected association of IRF2 with type 1 psoriasis at two markers in the IRF2 gene. Haplotype sharing analysis confirmed association of IRF2 with type 1 psoriasis (p=0.0017; pcorr=0.03). The 921G/A SNP in exon 9 was found to obliterate a predicted exon splice enhancer in an allele-specific manner. There was a suggestive increase of homozygosity for the splicing-deficient allele in type 1 psoriasis patients. Our data identify IRF2 as a potential susceptibility gene for psoriasis.