Genetic analysis of PSORS2 markers in a UK dataset supports the association between RAPTOR SNPs and familial psoriasis

Psoriasis [MIM 177900] is a chronic and disfiguring skin disorder, which is inherited as a multifactorial trait.1 Genome wide scans have repeatedly mapped a major disease susceptibility locus (PSORS1) to the Major Histocompatibility Complex (MHC), on chromosome 6p21 (reviewed by Capon et al2). Outside of the MHC, at least eight additional susceptibility intervals have been reported (PSORS2-9) (reviewed by Capon et al2). The PSORS2 interval [MIM 602723] was originally mapped to chromosome 17q25, in a sample of extended pedigrees presenting with disease segregation across multiple generations.3 Linkage to PSORS2 was later replicated in independently ascertained cohorts.4–6 Conversely, two distinct genome wide scans carried out by our group failed to detect any evidence for linkage to PSORS2, in United Kingdom cohorts of European descent.7,8 High density genetic analysis of the PSORS2 interval recently identified two distinct association peaks, both defined by a small number of non-coding single nucleotide polymorphisms (SNPs).9 The proximal peak spans a 20 kb genomic segment where a putative susceptibility allele, mapping between the SLC9AR1 and NAT9 genes, abolishes a RUNX1 binding site. The less characterised distal region of association lies 6 Mb away, within intron 3 of the RAPTOR gene [MIM *607130].9 To define the relevance of PSORS2 genetic variation …