Xianfa Tang

Genome-wide association study for vitiligo identifies susceptibility loci at 6q27 and the MHC

We conducted a genome-wide association study of generalized vitiligo in the Chinese Han population by genotyping 1,117 cases and 1,429 controls. The 34 most promising SNPs were carried forward for replication in samples from individuals of the Chinese Han (5,910 cases and 9,916 controls) and Chinese Uygur (713 cases and 824 controls) populations. We identified two independent association signals within the major histocompatibility complex (MHC) region (rs11966200, Pcombined = 1.48 × 10−48, OR = 1.90; rs9468925, Pcombined = 2.21 × 10−33, OR = 0.74). Further analyses suggested that the strong association at rs11966200 might reflect the reported association of the HLA-A*3001, HLA-B*1302, HLA-C*0602 and HLA-DRB1*0701 alleles and that the association at rs9468925 might represent a previously unknown HLA susceptibility allele. We also identified one previously undescribed risk locus at 6q27 (rs2236313, Pcombined = 9.72 × 10−17, OR = 1.20), which contains three genes: RNASET2, FGFR1OP and CCR6. Our study provides new insights into the genetic basis of vitiligo.

A large-scale screen for coding variants predisposing to psoriasis.

To explore the contribution of functional coding variants to psoriasis, we analyzed nonsynonymous single-nucleotide variants (SNVs) across the genome by exome sequencing in 781 psoriasis cases and 676 controls and through follow-up validation in 1,326 candidate genes by targeted sequencing in 9,946 psoriasis cases and 9,906 controls from the Chinese population. We discovered two independent missense SNVs in IL23R and GJB2 of low frequency and five common missense SNVs in LCE3D, ERAP1, CARD14 and ZNF816A associated with psoriasis at genome-wide significance. Rare missense SNVs in FUT2 and TARBP1 were also observed with suggestive evidence of association. Single-variant and gene-based association analyses of nonsynonymous SNVs did not identify newly associated genes for psoriasis in the regions subjected to targeted resequencing. This suggests that coding variants in the 1,326 targeted genes contribute only a limited fraction of the overall genetic risk for psoriasis.

Exome sequencing identifies MVK mutations in disseminated superficial actinic porokeratosis

Disseminated superficial actinic porokeratosis (DSAP) is an autosomal dominantly inherited epidermal keratinization disorder whose etiology remains unclear. We performed exome sequencing in one unaffected and two affected individuals from a DSAP family. The mevalonate kinase gene (MVK) emerged as the only candidate gene located in previously defined linkage regions after filtering against existing SNP databases, eight HapMap exomes and 1000 Genomes Project data and taking into consideration the functional implications of the mutations. Sanger sequencing in 57 individuals with familial DSAP and 25 individuals with sporadic DSAP identified MVK mutations in 33% and 16% of these individuals (cases), respectively. All 14 MVK mutations identified in our study were absent in 676 individuals without DSAP. Our functional studies in cultured primary keratinocytes suggest that MVK has a role in regulating calcium-induced keratinocyte differentiation and could protect keratinocytes from apoptosis induced by type A ultraviolet radiation. Our results should help advance the understanding of DSAP pathogenesis.

Sequencing-based approach identified three new susceptibility loci for psoriasis

In a previous large-scale exome sequencing analysis for psoriasis, we discovered seven common and low-frequency missense variants within six genes with genome-wide significance. Here we describe an in-depth analysis of noncoding variants based on sequencing data (10,727 cases and 10,582 controls) with replication in an independent cohort of Han Chinese individuals consisting of 4,480 cases and 6,521 controls to identify additional psoriasis susceptibility loci. We confirmed four known psoriasis susceptibility loci (IL12B, IFIH1, ERAP1 and RNF114; 2.30 × 10(-20)≤P≤2.41 × 10(-7)) and identified three new susceptibility loci: 4q24 (NFKB1) at rs1020760 (P=2.19 × 10(-8)), 12p13.3 (CD27-LAG3) at rs758739 (P=4.08 × 10(-8)) and 17q12 (IKZF3) at rs10852936 (P=1.96 × 10(-8)). Two suggestive loci, 3p21.31 and 17q25, are also identified with P<1.00 × 10(-6). The results of this study increase the number of confirmed psoriasis risk loci and provide novel insight into the pathogenesis of psoriasis.

Association Analyses Identify Three Susceptibility Loci for Vitiligo in the Chinese Han Population

To identify susceptibility loci for vitiligo, we extended our previous vitiligo genome-wide association study with a two-staged replication study that included 6,857 cases and 12,025 controls from the Chinese Han population. We identified three susceptibility loci, 12q13.2 (rs10876864, P(combined)=8.07 × 10(-12), odds ratio (OR)=1.18), 11q23.3 (rs638893, P(combined)=2.47 × 10(-9), OR=1.22), and 10q22.1 (rs1417210, P(combined)=1.83 × 10(-8), OR=0.88), and confirmed three previously reported loci for vitiligo, 3q28 (rs9851967, P(combined)=8.57 × 10(-8), OR=0.88), 10p15.1 (rs3134883, P(combined)=1.01 × 10(-5), OR=1.11), and 22q12.3 (rs2051582, P(combined)=2.12 × 10(-5), OR=1.14), in the Chinese Han population. The most significant single-nucleotide polymorphism in the 12q13.2 locus is located immediately upstream of the promoter region of PMEL, which encodes a major melanocyte antigen and has expression loss in the vitiligo lesional skin. In addition, both 12q13.2 and 11q23.3 loci identified in this study are also associated with other autoimmune diseases such as type 1 diabetes and systemic lupus erythematosus. These findings provide indirect support that vitiligo pathogenesis involves a complex interplay between immune regulatory factors and melanocyte-specific factors. They also highlight similarities and differences in the genetic basis of vitiligo in Chinese and Caucasian populations.

Association analyses identifying two common susceptibility loci shared by psoriasis and systemic lupus erythematosus in the Chinese Han population

Background Genome-wide association studies (GWASs) have revealed a large number of genetic risk loci for many autoimmune diseases. One clear finding emerging from the published genetic studies of autoimmunity is that different autoimmune diseases, such as psoriasis and systemic lupus erythematosus (SLE), share susceptibility loci. Our study explores additional susceptibility loci shared by psoriasis and SLE in the Chinese Han population. Methods In total, 20 single nucleotide polymorphisms (SNPs) in 17 previously reported psoriasis susceptibility loci and 34 SNPs from 24 previously reported SLE susceptibility loci were investigated in our initial psoriasis and SLE GWAS dataset. Among these SNPs, we selected two SNPs (rs8016947 and rs4649203) with association values of p<5×10−2 for both diseases in the GWAS data for further investigation in psoriasis (7260 cases and 9842 controls) and SLE (2207 cases and 9842 controls) using a Sequenom MassARRAY system. Results We found that these two SNPs (rs8016947 and rs4649203) in two loci (NFKBIA and IL28RA) were associated with psoriasis and SLE with genome-wide significance (Pcombined<5×10−8 in psoriasis and Pcombined<5×10−8 in SLE): rs8016947 at NFKBIA (Pcombined-psoriasis=3.90×10−10, Pcombined-SLE=1.08×10−13) and rs4649203 at IL28RA (Pcombined-psoriasis=3.91×10−12, Pcombined-SLE=9.90×10−9). Conclusions These results showed that two common susceptibility loci (NFKBIA and IL28RA) are shared by psoriasis and SLE in the Chinese Han population.

The effect of overweight and obesity on psoriasis patients in Chinese Han population: a hospital-based study.

Background  Accumulating evidence indicates that psoriasis is associated with increased risk of overweight and obesity. However, few studies have investigated this relationship in Chinese Han population.

EZH2 genetic variants affect risk of gastric cancer in the Chinese Han population.

Enhancer of zeste 2 (EZH2) gene encodes a histone methyltransferase that constitutes the catalytic component of the polycomb repressive complex‐2 (PRC2) to initiate epigenetic silencing of genes. It is reported that the expression level of EZH2 in gastric cancer tissue was highly correlated with tumor progression, however, whether EZH2 genetic variants were associated with the risk of gastric cancer remains yet unknown. In this study, we conducted a genotyping analysis for EZH2 in 311 cases of gastric cancer and 425 controls from the Chinese Han population. We found five single nucleotide polymorphisms (SNP; rs12670401, rs6464926, rs2072407, rs734005, and rs734004) of EZH2 gene were significantly associated with the risk of gastric cancer. Of which, the rs12670401 with the minor allele C and rs6464926 with the minor allele T revealed strong associations with increased gastric cancer risk [P = 0.009, adjusted odds ratio (aOR) = 1.327, 95% CI = 1.075–1.683 and P = 0.012, aOR = 1.310, 95% CI = 1.059–1.619]. The other three SNPs, rs2072407, rs734005, and rs734004 contributed to significantly reduced risk of gastric cancer (P = 0.033, aOR = 0.787, 95% CI = 0.633–0.981, P = 0.045, aOR = 0.799, 95% CI = 0.642–0.995 and P = 0.048, aOR = 0.803, 95% CI = 0.645–0.999), respectively. We further found that rs12670401 and rs6464926 were in a strong LD while rs2072407, rs734005, and rs734004 were in another. Haplotype analysis of the five SNPs showed that haplotype CCTCT reduced the risk of gastric cancer (P = 0.031 and aOR = 0.784), while haplotype GTCTC significantly elevated the risk of gastric cancer (P = 0.011 and aOR = 1.310). We concluded that EZH2 variants were significantly associated with gastric cancer risk. Our results for the first time provided new insight into susceptibility factors of EZH2 gene variants in carcinogenesis of gastric cancer of the Chinese Han population.

Exome sequencing identifies a COL14A1 mutation in a large Chinese pedigree with punctate palmoplantar keratoderma

Background Punctate palmoplantar keratoderma (PPPK) is a rare autosomal dominant skin disorder characterised by numerous hyperkeratotic papules irregularly distributed on the palms and soles. To date, no causal gene for this disease has been identified. Methods We performed exome sequencing analysis of four affected individuals and two unaffected controls from one Chinese PPPK family where disease locus was mapped at 8q24.13-8q24.21 by our previous linkage analysis. Results We identified a novel heterozygous mutation in COL14A1 gene (c.4505C→T (p.Pro1502Leu)), which located within the linkage region that we previously identified for PPPK. The mutation was shared by the four affected individuals, but not for the two controls of the family. Sanger sequencing confirmed this mutation in another four cases from this family. This mutation was invisible in the normal controls of this family as well as the additional 676 unrelated normal controls and 781 patients with other disease. The shared COL14A1 mutation, p.Pro1502Leu, is a missense substitution at a highly conserved amino acid residue across multiple species. Conclusions The power of combining exome sequencing and linkage information in the study of genetics of autosomal dominant disorders, even in simplex cases, has been demonstrated. Our results suggested that COL14A1 would be a casual gene for PPPK, which was helpful for advancing us on understanding of the pathogenesis of PPPK.

Genetic Susceptibility to Vitiligo: GWAS Approaches for Identifying Vitiligo Susceptibility Genes and Loci

Vitiligo is an autoimmune disease with a strong genetic component, characterized by areas of depigmented skin resulting from loss of epidermal melanocytes. Genetic factors are known to play key roles in vitiligo through discoveries in association studies and family studies. Previously, vitiligo susceptibility genes were mainly revealed through linkage analysis and candidate gene studies. Recently, our understanding of the genetic basis of vitiligo has been rapidly advancing through genome-wide association study (GWAS). More than 40 robust susceptible loci have been identified and confirmed to be associated with vitiligo by using GWAS. Most of these associated genes participate in important pathways involved in the pathogenesis of vitiligo. Many susceptible loci with unknown functions in the pathogenesis of vitiligo have also been identified, indicating that additional molecular mechanisms may contribute to the risk of developing vitiligo. In this review, we summarize the key loci that are of genome-wide significance, which have been shown to influence vitiligo risk. These genetic loci may help build the foundation for genetic diagnosis and personalize treatment for patients with vitiligo in the future. However, substantial additional studies, including gene-targeted and functional studies, are required to confirm the causality of the genetic variants and their biological relevance in the development of vitiligo.