PSORS2 is due to mutations in CARD14

Psoriasis is a common, immune-mediated, genetic disorder of the skin associated with arthritis in approximately 30% of cases. Previously, we localized PSORS2 (psoriasis susceptibility locus 2) to chromosome 17q25.3-qter following a genome-wide linkage scan in a family of European origin with multiple cases of psoriasis and psoriatic arthritis. Linkage to PSORS2 was also observed in a multiply affected psoriasis family from Taiwan. With genomic capture and DNA sequencing, we identified unique gain-of-function mutations in caspase recruitment domain family, member 14 (CARD14) that segregated with psoriasis. The mutations, c.349G>A (p.Gly117Ser) and c.349+5G>A respectively, altered splicing between exons 3 and 4 of CARD14. A de novo mutation in CARD14, c.413A>C [p.Glu138Ala], was detected in a child with sporadic, early-onset, generalized pustular psoriasis. CARD14 activates nuclear factor kappa B (NF-kB), and the p.Gly117Ser and p.Glu138Ala substitutions were shown to lead to enhanced NF-kB activation and upregulation of a subset of psoriasis-associated genes in keratinocytes compared to wildtype CARD14. These included chemokine (C-C motif) ligand 20 (CCL20) and interleukin 8 (IL8). CARD14 is localized mainly in the basal and suprabasal layers of healthy skin epidermis, while in lesional psoriatic skin it is reduced in the basal layer and more diffusely upregulated in the suprabasal layers of the lesional epidermis. We propose that, following a triggering event that can include epidermal injury, rare gain-of-function mutations in CARD14 initiate a process that includes inflammatory cell recruitment by keratinocytes. This perpetuates a vicious cycle of epidermal inflammation and regeneration that is the hallmark of psoriasis. No replicates are included. Three sample sets. [1] Skin biopsies had RNA extracted for expression within target tissue. [2] HEK cells were transfected with different constructs (including wildtype) of CARD14 to determine the mutational effect in keratinocytes. [3] Keratinocytes derived from psoriasis patients with CARD14 mutations were cultured and compared with and without stimulation with TNFalpha.