Increased Risk of Psoriasis due to combined effect of HLA-Cw6 and LCE3 risk alleles in Indian population

Identifying the genetic associations among the psoriasis patients in eastern India

Psoriasis is a multifactorial genetic disorder manifested by hyperproliferation and abnormal differentiation of epidermal keratinocytes, along with the infiltration of inflammatory cells into the skin. Although ~80 genetic susceptibility variants were reported in psoriasis, many loci showed population-specific associations, warranting the need for more population-specific association studies in psoriasis. We determined the association of forty single nucleotide polymorphisms (SNPs) among 2136 psoriasis patients and normal individuals from eastern India. We investigated the expression of corresponding genes and evaluated the protein structure stability for the genes with susceptible coding variants. We found fifteen SNPs significantly associated with psoriasis, while additional three SNPs showed significant association when we classified the patients based on the presence of HLA-Cw6 allele. Epistatic interaction between HLA-Cw6 and other associated loci showed significant association with the SNPs at PSORS1 region, along with other five SNPs outside PSORS1. Three genes showed significant differential expression in psoriatic tissues compared to the adjacent normal skin tissues but were not differential when classified the patients based on their genotypes. SNP rs495337 at SPATA2 (Spermatogenesis Associated 2) showed a 1.2-fold increased risk among the HLA-Cw6 patients compared to combined samples. We found significant downregulation of SPATA2 among the patients with risk genotypes and HLA-Cw6 allele compared to the non-risk genotypes. Protein structure stability analysis showed reduced structural stability for all the mutant residues caused by the associated coding variants. Our study evaluated the genetic associations of psoriasis-susceptible variants in India and evaluated the possible functional significance of these associated variants in psoriasis.

Disentangling the complexity of psoriasis in the post-genome-wide association era

In recent years, genome-wide association studies (GWAS) have been instrumental in unraveling the genetic architecture of complex diseases, including psoriasis. The application of large-scale GWA studies in psoriasis has illustrated several associated loci that participate in the cutaneous inflammation, however explaining a fraction of the disease heritability. With the advent of high-throughput sequencing technologies and functional genomics approaches, the post-GWAS era aims to unravel the functional mechanisms underlying the inter-individual variability in psoriasis patients. In this review, we present the key advances of psoriasis GWAS in under-represented populations, rare, non-coding and structural variants and epistatic phenomena that orchestrate the interplay between different cell types. We further review the gene-gene and gene-environment interactions contributing to the disease predisposition and development of comorbidities through Mendelian randomization studies and pleiotropic effects of psoriasis-associated loci. We finally examine the holistic approaches conducted in psoriasis through system genetics and state-of-the-art transcriptomic analyses, discussing their potential implication in the expanding field of precision medicine and characterization of comorbidities.

The HLA-Cw*06 allele may predict the response to methotrexate (MTX) treatment in Chinese arthritis-free psoriasis patients

MTX in genetically distinctive Chinese psoriatic patients remains less explored. The present study aimed to determine the impact of HLA-Cw*06 on MTX response in a Chinese psoriasis patient population. A total of 204 patients with psoriasis were enrolled in this study. Clinical data and DNA samples from all patients were collected. The allele of HLA-Cw*06 genotyping was detected using direct Sanger sequencing. This study enrolled 204 patients with psoriasis, including 47 (23.04%) psoriatic arthritis patients, 157 (76.96%) patients free of psoriatic arthritis. Overall, 110 (53.92%) of all patients carried the HLA-Cw*06 allele. This frequency in patients with arthritis-free psoriasis was higher than that in those with psoriatic arthritis (58.59 vs. 38.30%, P = 0.014). After 8 weeks of MTX treatment, the arthritis-free psoriasis patients, who tested positive for the HLA-Cw*06 allele, showed significant improvement compared to those who tested negative (For PASI50, 78.57 vs. 55.22%, P = 0.02, and for PASI75, 51.11 vs. 34.33%, P = 0.036). The psoriatic arthritis-free patients who carried the HLA-Cw*06 allele in combination with the ABCB1 rs1045642 CC genotype showed the highest improvement. A regression model containing HLA-Cw*06, rs1045642T > C, and initial PASI scores was used to construct the efficacy prediction model of MTX, which yielded AUC values of 73.2 and 75.6% for PASI50 and PASI75 to MTX, respectively, in arthritis-free psoriasis patients. The HLA-Cw*06 allele is associated with optimal response to MTX treatment in arthritis-free Chinese psoriasis patients. When combined with clinical indicators, the polymorphism explained more than 75% of the individual efficacy differences.

Variations in genetics, biology, and phenotype of cutaneous disorders in skin of color - Part I: Genetic, biologic, and structural differences in skin of color

Skin of color (SOC) populations include those who identify as Black/African, Hispanic/Latinx, Asian/Pacific Islander, American Indian/Native Alaskan, Indigenous Australian, Middle Eastern, biracial/multiracial, or non-White; this list is far from exhaustive and may vary between and within cultures. Recent genetic and immunological studies have suggested that cutaneous inflammatory disorders (atopic dermatitis, psoriasis, and hidradenitis suppurativa) and malignancies (melanoma, basal cell carcinoma, and cutaneous T-cell lymphoma) may have variations in their immunophenotype among SOC. Additionally, there is growing recognition of the substantial role social determinants of health play in driving health inequalities in SOC communities. It is critically important to understand that social determinants of health often play a larger role than biologic or genetic factors attributed to "race" in health care outcomes. Herein, we describe the structural, genetic, and immunological variations and the potential implications of these variations in populations with SOC. This article underscores the importance of increasing the number of large, robust genetic studies of cutaneous disorders in SOC to create more targeted, effective therapies for this often underserved and understudied population. Part II of this CME will highlight the clinical differences in the phenotypic presentation of and the health disparities associated with the aforementioned cutaneous disorders in SOC.

Transethnic analysis of psoriasis susceptibility in South Asians and Europeans enhances fine-mapping in the MHC and genomewide

Because transethnic analysis may facilitate prioritization of causal genetic variants, we performed a genomewide association study (GWAS) of psoriasis in South Asians (SAS), consisting of 2,590 cases and 1,720 controls. Comparison with our existing European-origin (EUR) GWAS showed that effect sizes of known psoriasis signals were highly correlated in SAS and EUR (Spearman ρ = 0.78; p < 2 × 10-14). Transethnic meta-analysis identified two non-MHC psoriasis loci (1p36.22 and 1q24.2) not previously identified in EUR, which may have regulatory roles. For these two loci, the transethnic GWAS provided higher genetic resolution and reduced the number of potential causal variants compared to using the EUR sample alone. We then explored multiple strategies to develop reference panels for accurately imputing MHC genotypes in both SAS and EUR populations and conducted a fine-mapping of MHC psoriasis associations in SAS and the largest such effort for EUR. HLA-C*06 was the top-ranking MHC locus in both populations but was even more prominent in SAS based on odds ratio, disease liability, model fit and predictive power. Transethnic modeling also substantially boosted the probability that the HLA-C*06 protein variant is causal. Secondary MHC signals included coding variants of HLA-C and HLA-B, but also potential regulatory variants of these two genes as well as HLA-A and several HLA class II genes, with effects on both chromatin accessibility and gene expression. This study highlights the shared genetic basis of psoriasis in SAS and EUR populations and the value of transethnic meta-analysis for discovery and fine-mapping of susceptibility loci.

Transcriptome Analysis of Host Inflammatory Responses to the Ectoparasitic Mite Sarcoptes scabiei var. hominis

Scabies, a human skin infestation caused by the ectoparasitic mite Sarcoptes scabiei var. hominis, affects more than 200 million people globally. The prevailing knowledge of the disease process and host immune response mechanisms is limited. A better understanding of the host-parasite relationship is essential for the identification of novel vaccine and drug targets. Here we aimed to interrogate the transcriptomic profiles of mite-infested human skin biopsies with clinical manifestations of ordinary scabies subjects ("OS"; n = 05) and subjects naive to scabies ("control"; n = 03) using RNASeq data analysis. A combined clustering, network, and pathway mapping approach enabled us to identify key signaling events in the host immune and pro-inflammatory responses to S. scabiei infestation. The clustering patterns showed various differentially expressed genes including inflammatory responses and innate immunity genes (DEFB4A, IL-19, CXCL8, CSF3, SERPINB4, S100A7A, HRNR) and notably upregulation of the JAK-STAT pathway in scabies-infested samples. Mite-infested human skin biopsies (GSE178563) were compared with an ex-vivo porcine infested model (E-MTAB-6433) and human skin equivalents (GSE48459). Marked enrichment of immune response pathways (JAK-STAT signaling, IL-4 and IL-13 pathway, and Toll receptor cascade), chemokine ligands and receptors (CCL17, CCL18, CCL3L1, CCL3L3, CCR7), and cytokines (IL-13 and IL-20) were observed. Additionally, genes known for their role in psoriasis and atopic dermatitis were upregulated, e.g., IL-19. The detailed transcriptomic profile has provided an insight into molecular functions, biological processes, and immunological responses and increased our understanding about transcriptomic regulation of scabies in human.

Functional Mapping of Genetic Interactions between HLA-Cw6 and LCE3A in Psoriasis

Functional studies to delineate the molecular mechanisms of causal genetic variants are the main focus in the post-GWAS era. Previous GWASs have identified >50 susceptibility loci associated with psoriasis. Functional understanding of the biology underlying the disease risk of most of these associated loci is unclear. In this study, we identified a regulatory SNP at the putative enhancer of the LCE3A gene within the epidermal differentiation complex that showed epistatic interaction with HLA-Cw6. The variant allele disrupted signal transducer and activator of transcription 3 binding to the region, thereby regulating the expression of the downstream LCE3A gene. Electrophoretic mobility shift and pulldown assay confirmed the preferential binding of signal transducer and activator of transcription 3 to the DNA with a wild-type allele compared with the DNA with a variant allele. The reporter assay further validated the IL-6‒stimulated phosphorylated signal transducer and activator of transcription 3‒mediated LCE3A activation in the presence of the wild-type allele. Interestingly, the presence of the HLA-Cw6 allele leads to IL-6‒mediated phosphorylation of signal transducer and activator of transcription 3, followed by its nuclear localization in the epidermal keratinocytes of psoriatic skin, suggesting indirect interaction of the HLA-Cw6 allele and a regulatory SNP upstream of the LCE3A gene. This study reflects an interesting approach to dissecting the molecular mechanism underlying the genetic interaction observed between HLA-Cw6 and LCE3A in psoriasis pathogenesis.

The roles of ERAP1 and ERAP2 in autoimmunity and cancer immunity: New insights and perspective

Autoimmunity and cancer affect millions worldwide and both, in principal, result from dysregulated immune responses. There are many well-known molecules involved in immunological process playing as a double-edged sword, by which associating autoimmune diseases and cancer. In this regard, Endoplasmic reticulum aminopeptidases (ERAP) 1, which belongs to the M1 family of aminopeptidases, plays a central role as a "molecular ruler", proteolyzing of N-terminal of the antigenic peptides before their loading onto HLA-I molecules for antigen presentation in the Endoplasmic Reticulum (ER). Several genome-wide association studies (GWAS) highlighted the significance of ERAP1 and ERAP2 in autoimmune diseases, including Ankylosing spondylitis, Psoriasis, Bechet's disease, and Birdshot chorioretinopathy, as well as in cancers. The expression of ERAP1/2 is mostly altered in different cancers compared to normal cells, but how this affects anti-cancer immune responses and cancer growth has been little explored. Recent studies on the immunological outcomes and the catalytic functions of ERAP1 and ERAP2 have provided a better understanding of their potential pathogenetic role in autoimmunity and cancer. In this review, we summarize the role of ERAP1 and ERAP2 in the autoimmune diseases and cancer immunity based on the recent advances in GWAS studies.

Association between HLA-Cw6 allele expression and characteristics of Javanese ethnic psoriasis patients in Indonesia

BACKGROUND Psoriasis is an autoimmune disease with involvement of genetic and environmental factors. The HLA-Cw6 allele is the strongest genetic factor that correlates with earlier onset and more severe clinical manifestation of psoriasis. In Javanese ethnic, HLA-Cw6 allelic expression has not been identified, although increasing psoriasis patients were found in hospital dermatology departments. The study was aimed to determine the allelic expression of HLA-Cw6 based on the onset and severity of psoriasis in Javanese ethnic. METHODS A cross-sectional study was conducted from March to September 2018. Sixty psoriasis patients in the Margono Soekarjo Hospital and Banyumas Regional General Hospital were recruited consecutively. Psoriasis type, diagnosis, onset, and disease severity were assessed by dermatologists. HLA-Cw6 allelic expression was identified by DNA isolation, quantitative testing, and HLA-Cw6 genotyping. Fisher’s exact and chi-square tests were used to evaluate the association of HLA-Cw6 with age, clinical type, disease severity, onset, and gender. RESULTS The HLA-Cw6 allele positivity was identified at 297 base pairs (bp), while control showed at 618 bp bands. Among 60 subjects, 13 subjects (22%) showed HLACw6 positivity, and 47 subjects (78%) were HLA-Cw6 negative. HLA-Cw6 genotypes were similarly distributed concerning age, onset, gender, clinical type, and disease severity in psoriasis patients of Javanese ethnic (p > 0.05). CONCLUSIONS HLA-Cw6 expression type may not have influence to the characteristics of patients with psoriasis.

Genetics of psoriasis: a basis for precision medicine

Psoriasis is an inflammatory skin disease with a background of polygenic inheritance. Both environmental and genetic factors are involved in the etiology of the disease. In the last two decades, numerous studies have been conducted through linkage analysis, genome-wide association study (GWAS), and direct sequencing to explore the role of genetic variation in disease pathogenesis and progression. To date, >80 psoriasis susceptibility genes have been identified, including HLA-Cw6, IL12B, IL23R, and LCE3B/3C. Some genetic markers have been applied in disease prediction, clinical diagnosis, treatment, and new drug development, which could further explain the pathogenesis of psoriasis and promote the development of precision medicine. This review summarizes related research on genetic variation in psoriasis and explores implications of the findings in clinical application and the promotion of a personalized medicine project.

Defining Early Life Stress as a Precursor for Autoimmune Disease

Childhood exposure to traumatic events, termed early life stress (ELS), is now widely recognized for causing long-term negative health effects that may not manifest until adulthood. Allostatic load (AL) describes the cumulative "wear-and-tear" effects of chronic stress on the body that may adversely affect human health by accelerating other disease processes. Recent epidemiological studies have reported higher stress levels in industrialized countries and trends of increasing prevalence in autoimmune diseases during recent decades. To elucidate mechanisms of stress-related immune dysregulation, most animal studies up to now have focused on AL and stress-triggered events occurring in adults but have not explored ELS in the context of autoimmune disorders. We have identified a current gap in understanding the impact of ELS on immune system ontogeny and its potential for priming genetically susceptible individuals who are at increased risk for autoimmune diseases later in life, through mechanisms involving neuroendocrine-immune cross talk. In this review, we highlight the intersection between stress and immune function, with a focus on ELS as consequential for increased autoimmune disorder risks later in life.

Epigenome-wide DNA methylation regulates cardinal pathological features of psoriasis

Background

Psoriasis is a chronic inflammatory autoimmune skin disorder. Several studies suggested psoriasis to be a complex multifactorial disease, but the exact triggering factor is yet to be determined. Evidences suggest that in addition to genetic factors, epigenetic reprogramming is also involved in psoriasis development. Major histopathological features, like increased proliferation and abnormal differentiation of keratinocytes, and immune cell infiltrations are characteristic marks of psoriatic skin lesions. Following therapy, histopathological features as well as aberrant DNA methylation reversed to normal levels. To understand the role of DNA methylation in regulating these crucial histopathologic features, we investigated the genome-wide DNA methylation profile of psoriasis patients with different histopathological features.

Results

Genome-wide DNA methylation profiling of psoriatic and adjacent normal skin tissues identified several novel differentially methylated regions associated with psoriasis. Differentially methylated CpGs were significantly enriched in several psoriasis susceptibility (PSORS) regions and epigenetically regulated the expression of key pathogenic genes, even with low-CpG promoters. Top differentially methylated genes overlapped with PSORS regions including S100A9, SELENBP1, CARD14, KAZN and PTPN22 showed inverse correlation between methylation and gene expression. We identified differentially methylated genes associated with characteristic histopathological features in psoriasis. Psoriatic skin with Munro’s microabscess, a distinctive feature in psoriasis including parakeratosis and neutrophil accumulation at the stratum corneum, was enriched with differentially methylated genes involved in neutrophil chemotaxis. Rete peg elongation and focal hypergranulosis were also associated with epigenetically regulated genes, supporting the reversible nature of these characteristic features during remission and relapse of the lesions.

Conclusion

Our study, for the first time, indicated the possible involvement of DNA methylation in regulating the cardinal pathophysiological features in psoriasis. Common genes involved in regulation of these pathologies may be used to develop drugs for better clinical management of psoriasis.

Electronic supplementary material

The online version of this article (10.1186/s13148-018-0541-9) contains supplementary material, which is available to authorized users.

Recent evolution of the human skin barrier

The skin is the first line of defense against the environment, with the epidermis as the outermost tissue providing much of the barrier function. Given its direct exposure to and encounters with the environment, the epidermis must evolve to provide an optimal barrier for the survival of an organism. Recent advances in genomics have identified a number of genes for the human skin barrier that have undergone evolutionary changes since humans diverged from chimpanzees. Here, we highlight a selection of key and innovative genetic findings for skin barrier evolution in our divergence from our primate ancestors and among modern human populations.

Psoriasis in Skin of Color: Insights into the Epidemiology, Clinical Presentation, Genetics, Quality-of-Life Impact, and Treatment of Psoriasis in Non-White Racial/Ethnic Groups

Psoriasis is a chronic inflammatory skin condition affecting diverse racial/ethnic groups throughout the world. Large population-based studies suggest that psoriasis occurs most often in individuals of European ancestry, followed by black and Hispanic individuals, although the true prevalence of psoriasis in non-white individuals is likely underestimated. Despite similarities in psoriasis between ethnic groups, there are notable differences in the presentation, quality-of-life impact, and treatment of psoriasis with important implications for the management of non-white individuals. Overall, heterogeneity in psoriasis susceptibility alleles, in combination with cultural and socioeconomic factors, may explain these differences. In this article, we review the epidemiology, clinical presentation, genetic polymorphisms, quality-of-life impact, and treatment nuances of psoriasis in patients with skin of color.

Human Leukocyte Antigen-Class I Alleles and the Autoreactive T Cell Response in Psoriasis Pathogenesis

Psoriasis is a complex immune-mediated inflammatory skin disease characterized by T-cell-driven epidermal hyperplasia. It occurs on a strong genetic predisposition. The human leukocyte antigen (HLA)-class I allele HLA-C*06:02 on psoriasis susceptibility locus 1 (PSORS1 on 6p21.3) is the main psoriasis risk gene. Other HLA-class I alleles encoding HLA molecules presenting overlapping peptide repertoires show associations with psoriasis as well. Outside the major histocompatibility complex region, genome-wide association studies identified more than 60 psoriasis-associated common gene variants exerting only modest individual effects. They mainly refer to innate immune activation and the interleukin-23/T_h/c17 pathway. Given their strong risk association, explaining the role of the HLA-risk alleles is essential for elucidating psoriasis pathogenesis. Psoriasis lesions develop upon epidermal infiltration, activation, and expansion of CD8⁺ T cells. The unbiased analysis of a paradigmatic Vα3S1/Vβ13S1-T-cell receptor from a pathogenic epidermal CD8⁺ T-cell clone of an HLA-C*06:02⁺ psoriasis patient had revealed that HLA-C*06:02 directs an autoimmune response against melanocytes through autoantigen presentation, and it identified a peptide form ADAMTS-like protein 5 as an HLA-C*06:02-presented melanocyte autoantigen. These data demonstrate that psoriasis is an autoimmune disease, where the predisposing HLA-class I alleles promote organ-specific inflammation through facilitating a T-cell response against a particular skin-specific cell population. This review discusses the role of HLA-class I alleles in the pathogenic psoriatic T-cell immune response. It concludes that as a principle of T-cell driven HLA-associated inflammatory diseases proinflammatory traits promote autoimmunity in the context of certain HLA molecules that present particular autoantigens.

HLA-Cw6 and psoriasis

Psoriasis is a multifactorial disease with a strong genetic background. HLA-Cw6 is one of the most strongly associated psoriasis susceptibility alleles. It is repeatedly observed to affect disease course, phenotypic features, severity, comorbidities and treatment outcomes. To the best of our knowledge, the roles of HLA-Cw6 in psoriasis have not yet been thoroughly reviewed. The worldwide frequency of the HLA-Cw6 allele varies greatly, with it being generally higher in white people than in Asians. The allele is associated with type I early-onset psoriasis. Stress, obesity and streptococcal pharyngitis are commonly observed in HLA-Cw6-positive patients. Phenotypically, HLA-Cw6 has been found to be associated with guttate psoriasis. In addition, patients carrying the allele are more likely to have arm, leg and trunk involvement, and the Koebner phenomenon. Patients with psoriatic arthritis with HLA-Cw6 more often have early onset and tend to show cutaneous symptoms before musculoskeletal symptoms. HLA-Cw6-positive patients have been shown in several studies to be more responsive to methotrexate and ustekinumab. However, this difference in ustekinumab efficacy was only moderate in a post-hoc analysis of a pivotal phase III study. HLA-Cw6 positivity also tends to be less frequent in high-need patients who fail conventional therapy. Small studies have also investigated the role of HLA-Cw6 in remission of psoriasis during pregnancy, and with the comorbidities of photosensitivity and atherosclerosis. Given the diverse nature of psoriasis pathogenesis, as well as the difference of HLA-Cw6 positivity in different ethnic groups, more studies are needed to confirm the role of HLA-Cw6 in psoriasis.

dbGAPs: A comprehensive database of genes and genetic markers associated with psoriasis and its subtypes

Psoriasis is a systemic hyperproliferative inflammatory skin disorder, although rarely fatal but significantly reduces quality of life. Understanding the full genetic component of the disease association may provide insight into biological pathways as well as targets and biomarkers for diagnosis, prognosis and therapy. Studies related to psoriasis associated genes and genetic markers are scattered and not easily amendable to data-mining. To alleviate difficulties, we have developed dbGAPs an integrated knowledgebase representing a gateway to psoriasis associated genomic data. The database contains annotation for 202 manually curated genes associated with psoriasis and its subtypes with cross-references. Functional enrichment of these genes, in context of Gene Ontology and pathways, provide insight into their important role in psoriasis etiology and pathogenesis. The dbGAPs interface is enriched with an interactive search engine for data retrieval along with unique customized tools for Single Nucleotide Polymorphism (SNP)/indel detection and SNP/indel annotations. dbGAPs is accessible at http://www.bmicnip.in/dbgaps/.

Associations of ERAP1 coding variants and domain specific interaction with HLA-C∗06 in the early onset psoriasis patients of India

Interferon-γ-induced aminopeptidase ERAP1 trims peptides within the endoplasmic reticulum so that they can be loaded onto MHC class I and presented to the CD8⁺ T-cells. ERAP1 association and its interaction with HLA-C∗06 is controversial across different populations. We have investigated the association and possible functional role of non-synonymous SNPs at different exons of ERAP1 (rs26653: Arg127Pro, rs30187: Lys528Arg and rs27044: Gln730Glu) and their interactions with HLA-C∗06 in psoriasis. Significant associations of HLA-C∗06 (OR=5.47, P<2.2×10^-16), rs30187 (OR 1.35, P=7.4×10^-4) and rs27044 (OR=1.24, P=5.8×10^-3) were observed. All three ERAP1 SNPs showed significant association only for HLA-C∗06 positive patients, while rs30187 and rs27044 showed significant association only for early onset patients (rs30187: OR=1.47, P=9.6×10^-5; rs27044: OR=1.36, P=3.3×10^-4). No differential expression of ERAP1 was observed either between paired uninvolved and involved skin tissues of psoriasis patients or between non-risk and risk variants in the involved skin. Significant epistatic interaction was observed between HLA-C∗06 and the SNP (rs27044) located at the peptide-binding cavity of ERAP1. Evolutionary conservation analysis among mammals showed confinement of Lys528 and Gln730 within highly conserved regions of ERAP1 and suggested the possible detrimental effect of this allele in ERAP1 regulation.

Psoriasis-Associated Late Cornified Envelope (LCE) Proteins Have Antibacterial Activity

Terminally differentiating epidermal keratinocytes express a large number of structural and antimicrobial proteins that are involved in the physical barrier function of the stratum corneum and provide innate cutaneous host defense. Late cornified envelope (LCE) genes, located in the epidermal differentiation complex on chromosome 1, encode a family of 18 proteins of unknown function, whose expression is largely restricted to epidermis. Deletion of two members, LCE3B and LCE3C (LCE3B/C-del), is a widely-replicated psoriasis risk factor that interacts with the major psoriasis-psoriasis risk gene HLA-C*06. Here we performed quantitative trait locus analysis, utilizing RNA-seq data from human skin and found that LCE3B/C-del was associated with a markedly increased expression of LCE3A, a gene directly adjacent to LCE3B/C-del. We confirmed these findings in a 3-dimensional skin model using primary keratinocytes from LCE3B/C-del genotyped donors. Functional analysis revealed that LCE3 proteins, and LCE3A in particular, have defensin-like antimicrobial activity against a variety of bacterial taxa at low micromolar concentrations. No genotype-dependent effect was observed for the inside-out or outside-in physical skin barrier function. Our findings identify an unknown biological function for LCE3 proteins and suggest a role in epidermal host defense and LCE3B/C-del-mediated psoriasis risk.

Association of IL12B risk haplotype and lack of interaction with HLA-Cw6 among the psoriasis patients in India

Psoriasis is a complex multifactorial chronic inflammatory skin disorder involving both genetic and environmental susceptibility factors. It is strongly associated with HLA-Cw6, but several studies suggested that further genetic factors may confer additional risk. We investigated the association of two single-nucleotide polymorphisms (SNPs), rs3212227 at the 3'-untranslated region and rs7709212 located at ~6.7 kb upstream from the transcription start site of IL12B gene in a case-control study comprising 1702 individuals from India. We found both SNPs were significantly associated with psoriasis (rs7709212: odds ratio (OR)=1.37, P-value=1.09 × 10^-5; rs3212227: OR=1.38, P-value=8.88 × 10^-6). IL12B gene was significantly upregulated in involved skin of psoriasis patients with risk genotype carriers (rs7709212_TT and rs3212227_TT) compared with non-risk genotype carriers (rs7709212_CC and rs3212227_GG). Significantly higher serum protein concentration of IL12 was also observed among risk allele carriers compared with non-risk allele carriers irrespective of the presence of HLA-Cw6 allele. Haplotype analysis suggested significant increased risk (OR=1.50, P-value=5.01 × 10^-8) to the disease when both risk alleles of IL12B were present. IL12 serum protein concentration of risk haplotype (TT-TT) carriers showed significant upregulation compared with the non-risk carriers independent of HLA-Cw6 alleles. Our data suggested the association of IL12B with the psoriasis, however no evidence was observed for the epistatic effect of IL12B with HLA-Cw6 among the psoriasis patients in India.