Variation at the IRF2 gene and susceptibility to psoriasis in chromosome 4q-linked families.

Evidence, largely from Irish pedigrees, indicates that a susceptibility locus for psoriasis maps to chromosome 4q. The gene encoding interferon regulatory factor-2 (IRF-2) maps to this region, and, as mice lacking IRF-2 exhibit a dermatologic phenotype resembling many aspects of human psoriasis, IRF-2 represents an attractive positional candidate. We set out to establish whether variation in IRF-2 sequence or expression was related to the development of psoriasis. First, the promoter, coding, and adjacent untranslated regions of IRF-2 were screened in individuals from 4q-linked families. Neither variant identified (IVS1A+29A/G; IVS3+729T/C), however, had functional credentials or statistical evidence supporting a susceptibility role. Second, in 62 Irish parent-offspring trios ascertained for psoriasis, we conducted a linkage-disequilibrium screen of the IRF2 region using a dense microsatellite map (covering 1.5 Mb from D4S1554 to D4S1540). Though there was nominal association for D4S1554/D4S2348 haplotypes (p=0.03) with one haplotype showing particularly skewed transmission to psoriatic offspring (p=0.0002, uncorrected), these markers lie some distance (500 kb) from IRF-2. Finally, we found no abnormalities of IRF-2 protein expression or distribution in skin biopsies from psoriatic individuals. These diverse lines of inquiry allow us to exclude variation in IRF2 as responsible for the 4q-linkage signal previously identified in Irish pedigrees.