CARD14 alterations in Tunisian patients with psoriasis and further characterization in European cohorts

Abstract

Background: Rare highly penetrant gain-of-function mutations in caspase recruitment domain family, member 14 (CARD14) can lead to psoriasis, a chronic inflammatory disease of the skin and other organs.

Objectives: To investigate the contribution of rare CARD14 variants to psoriasis in the Tunisian population and to expand knowledge of CARD14 variants in the European population.

Methods: CARD14 coding exons were resequenced in patients with psoriasis and controls from Tunisia and Europe, including 16 European cases with generalized pustular psoriasis (GPP). Novel variants were evaluated for their effect on nuclear factor (NF)-κB signalling.

Results: Rare variants in CARD14 were significantly enriched in Tunisian cases compared with controls. Three were collectively found in 5% of Tunisian cases, and all affected the N-terminal region of the protein harbouring its caspase recruitment domain or coiled-coil domain. These variants were c.349G>A (p.Gly117Ser), c.205C>T (p.Arg69Trp) and c.589G>A (p.Glu197Lys). c.589G>A (p.Glu197Lys) led to upregulation of NF-κB activity in a similar manner to that of previously described psoriasis-associated mutations. p.Arg69Trp led to sevenfold downregulation of NF-κB activity. One Tunisian case harboured a c.1356+5G>A splice alteration that is predicted to lead to loss of exon 9, which encodes part of the coiled-coil domain. No cases of GPP harboured an interleukin-36RN mutation, but one of 16 cases of GPP with a family history of psoriasis vulgaris harboured a c.1805C>T (p.Ser602Leu) mutation in CARD14.

Conclusions: These observations provide further insights into the genetic basis of psoriasis in the Tunisian population and provide functional information on novel CARD14 variants seen in cases from Tunisia and other populations.

Figure 1. CARD14 protein domains and locations of amino acid substitutions

Novel missense variants identified in CARD14 by re-sequencing are shown relative to key protein domains.

Figure 2. Effect of wild-type and novel CARD14 variants on NF-kb activation

HEK293 cells were transfected with the construct that codes for wild type CARD14sh, the same construct harbouring one of the rare variants shown, or a construct that codes for CARD14cl and lacks the CARD domain. NF-kb activity was determined by measuring relative luciferase activity. All values were first normalized to Renilla expression to control for transfection efficiency and then adjusted to control for activity of the empty background vector, pTAL-luc. Change in NF-kb activity relative to background vector was determined for each variant (y-axis, NF-kb activity). Every data point represents the average of three replicates. Asterisks show results from two-tailed, unpaired student’s t tests comparing NF-kb activation induced by the indicated variant to that of unstimulated cells with CARD14sh. * p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001.