Association of PSORS1C3, CARD14 and TLR4 genotypes and haplotypes with psoriasis susceptibility

Abstract

Psoriasis is a common chronic, immune-mediated inflammatory disease of the skin. PSORS1C3 is a non-protein coding gene, of which the RNA transcript is found in psoriatic patients. CARD14 is mainly expressed in epidermal keratinocytes. TLR4 is a transmembrane protein to recognize microbial antigens. Our study aimed to assess the relationship among PSORS1C3, CARD14 and TLR4 polymorphisms, inflammatory expression and psoriasis susceptibility. To the end, 71 patients with psoriasis and 46 healthy individuals with the well-characterized clinical profiles were enrolled. Gene polymorphisms were determined by Sanger DNA sequencing and secretion of cytokines by ELISA. As a result, genetic analysis of PSORS1C3 gene identified nine SNPs and three haplotype blocks. Sequencing of the CARD14 gene determined eight SNPs and one haplotype block. Sequencing of TLR4 gene identified nine SNPs, in which a SNP rs1018673641 was found to exert deleterious effect. The linkage disequilibrium analysis showed that seven variants in PSORS1C3 gene and three SNPs in CARD14 gene were in tightly linked. More importantly, a significant association between IL-6 level and rs1018673641 AT genotype in TLR4 gene was detected in psoriatic patients. In conclusion, the PSORS1C3, CARD14 and TLR4 polymorphisms and haplotypes may be correlated with risk of suffering psoriasis and the IL-6-mediated chronic inflammation in psoriasis could be partially regulated by the TLR4 functional variant.

Figure 1-. Polymorphisms of PSORS1C3 gene in psoriatic patients and controls. Partial sequence chromatograms of PSORS1C3 gene from wildtype (1^st panels) and variant (2^nd and 3^rd panels) genotypes of the rs887464 G>A, rs3868542 A>G, rs11507945 C>T, rs3871247 C>T, rs369029873 G>A, rs3130506 C>T, rs3871246 A>G, rs11967629 G>A and +280 G>A polymorphisms are shown. Arrows indicate the location of the base changes.

Figure 2-. Polymorphisms of CARD14 gene in psoriatic patients and controls. Partial sequence chromatograms of CARD14 gene from wildtype (1^st panels) and variant (2^nd and 3^rd panels) genotypes of the rs11653893 A>G, p.T812A/S (c.3150 A>G/T), rs11652075 C>T, rs189286068 C>T, rs61757652 C>T, rs1486223942 C>T, c.3285+54 C>G and rs376428578 C>A polymorphisms are shown. Arrows indicate the location of the base changes.

Figure 3-. Polymorphisms of TLR4 gene in psoriatic patients and controls. A: Partial sequence chromatograms of TLR4 gene from wildtype (1^st panels) and variant (2^nd and 3^rd panels) genotypes of the rs2149356 T>G, c.331-428 T>G, c.331-200 G>A, c.331-102 T>A, c.331-1 G>C, rs770576183 G>C/A, rs1018673641 A>T, p.L101L (c.371 C>T) and p.S102S (c.376 C>T) polymorphisms are shown. Arrows indicate the location of the base changes. B: Functional prediction of the SNP rs1018673641 by the Polyphen-2 program.

Figure 4-. Linkage disequilibrium (LD) analysis of TLR4, CARD14 and PSORS1C3 genes in psoriatic patients and controls. Linkage disequilibrium analysis shows the genotyped variants in PSORS1C3, CARD14 and TLR4 genes. D’ value was shown in the LD block.

Figure 5-. Expression of inflammatory cytokines in psoriatic patients. A: Arithmetic means ± SEM (n = 46-71) of IL-6, IL-17A and TNF-α concentrations are attained from sera of healthy donors and psoriatic patients. ** (p<0.01) and *** (p<0.001) indicate significant differences from healthy donors (Mann-Whitney U test). The box plots denote the median, IQR and minimum and maximum values. B: Arithmetic means ± SEM (n = 11-60) of IL-6 concentration is attained from sera of psoriatic patients carrying the AA or AT genotype of SNP rs1018673641 in TLR4 gene. *** (p<0.001) indicates significant difference from the AA genotype (Mann-Whitney U test). The box plots denote the median, IQR and minimum and maximum values.