Association of the late cornified envelope-3 genes with psoriasis and psoriatic arthritis: a systematic review

Functional Genomics in Psoriasis

Psoriasis is an autoimmune cutaneous condition that significantly impacts quality of life and represents a burden on society due to its prevalence. Genome-wide association studies (GWASs) have pinpointed several psoriasis-related risk loci, underlining the disease's complexity. Functional genomics is paramount to unveiling the role of such loci in psoriasis and disentangling its complex nature. In this review, we aim to elucidate the main findings in this field and integrate our discussion with gold-standard techniques in molecular biology-i.e., Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-and high-throughput technologies. These tools are vital to understanding how disease risk loci affect gene expression in psoriasis, which is crucial in identifying new targets for personalized treatments in advanced precision medicine.

Psoriasis and Psoriatic Arthritis-Associated Genes, Cytokines, and Human Leukocyte Antigens

In recent years, research has intensified in exploring the genetic basis of psoriasis (PsO) and psoriatic arthritis (PsA). Genome-wide association studies (GWASs), including tools like ImmunoChip, have significantly deepened our understanding of disease mechanisms by pinpointing risk-associated genetic loci. These efforts have elucidated biological pathways involved in PsO pathogenesis, particularly those related to the innate immune system, antigen presentation, and adaptive immune responses. Specific genetic loci, such as TRAF3IP2, REL, and FBXL19, have been identified as having a significant impact on disease development. Interestingly, different genetic variants at the same locus can predispose individuals to either PsO or PsA (e.g., IL23R and deletion of LCE3B and LCE3C), with some variants being uniquely linked to PsA (like HLA B27 on chromosome 6). This article aims to summarize known and new data on the genetics of PsO and PsA, their associated genes, and the involvement of the HLA system and cytokines.

Skin barrier-inflammatory pathway is a driver of the psoriasis-atopic dermatitis transition

As chronic inflammatory conditions driven by immune dysregulation are influenced by genetics and environment factors, psoriasis and atopic dermatitis (AD) have traditionally been considered to be distinct diseases characterized by different T cell responses. Psoriasis, associated with type 17 helper T (Th17)-mediated inflammation, presents as well-defined scaly plaques with minimal pruritus. AD, primarily linked to Th2-mediated inflammation, presents with poorly defined erythema, dry skin, and intense itching. However, psoriasis and AD may overlap or transition into one another spontaneously, independent of biological agent usage. Emerging evidence suggests that defects in skin barrier-related molecules interact with the polarization of T cells, which forms a skin barrier-inflammatory loop with them. This loop contributes to the chronicity of the primary disease or the transition between psoriasis and AD. This review aimed to elucidate the mechanisms underlying skin barrier defects in driving the overlap between psoriasis and AD. In this review, the importance of repairing the skin barrier was underscored, and the significance of tailoring biologic treatments based on individual immune status instead of solely adhering to the treatment guidelines for AD or psoriasis was emphasized.

The role of enhancers in psoriasis and atopic dermatitis

Regulatory elements, particularly enhancers, play a crucial role in disease susceptibility and progression. Enhancers are DNA sequences that activate gene expression and can be affected by epigenetic modifications, interactions with transcription factors (TFs) or changes to the enhancer DNA sequence itself. Altered enhancer activity impacts gene expression and contributes to disease. In this review, we define enhancers and the experimental techniques used to identify and characterize them. We also discuss recent studies that examine how enhancers contribute to atopic dermatitis (AD) and psoriasis. Articles in the PubMed database were identified (from 1 January 2010 to 28 February 2023) that were relevant to enhancer variants, enhancer-associated TFs and enhancer histone modifications in psoriasis or AD. Most enhancers associated with these conditions regulate genes affecting epidermal homeostasis or immune function. These discoveries present potential therapeutic targets to complement existing treatment options for AD and psoriasis.

Epidemiology of mental health comorbidity in patients with psoriasis: An analysis of trends from 1986 to 2019

BACKGROUND

The prevalence of mental disorders such as depression, anxiety, and suicide has increased in patients with psoriasis, although no study has systematically analyzed the epidemiology worldwide.

OBJECTIVE

To explore the prevalence and incidence of psoriasis with comorbid mental disorders (i.e., depression, anxiety, and suicide).

METHODS

Five databases from establishment through May 2022 were searched. Stata SE 15.1 was used for the data analysis. Subgroup, meta-regression, and sensitivity analyses were used to evaluate the heterogeneity of pooled studies.

RESULTS

We evaluated 56 studies in our research. The prevalence of depression, anxiety, and suicide in adults with psoriasis was 20%, 21%, and 0.77%. Patients with psoriasis in North America had a higher prevalence of depression and suicide, whereas those in South America had a higher prevalence of anxiety. The incidence of depression, anxiety, and suicide was 42.1, 24.7, and 2.6 per 1000 person-years in adults with psoriasis, respectively.

LIMITATIONS

All of the included studies were published in Chinese and English, causing a degree of selection bias.

CONCLUSION

These findings demonstrate the incidence and prevalence of comorbid mental disorders in patients with psoriasis, which may raise awareness among physicians and patients regarding the mental problems associated with psoriasis.

Transcriptomic Analysis Reveals Genetic Cross-Talk between Periodontitis and Hypothyroidism

Background. Aim of this bioinformatics study based on transcriptomic analysis was to reveal the cross-talk between periodontitis (PD) and hypothyroidism (HT). Methods. The gene expression datasets GSE18152 and GSE176153 of HT and GSE10334, GSE16134, and GSE173078 of PD were downloaded through the Gene Expression Omnibus (GEO) database. Differential Expression Genes (DEG) between cases and controls in each microarray were assessed by using the “limma” (linear models for microarray data) R package (|log2 fold change (FC)| >0 and $P$ -value <0.05). To analyze the cross-talk effect between HT and PD, the intersection of DEG of HT and PD was selected. To investigate the biological function of cross-talk genes, the gene ontology (GO) functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were applied. Protein-Protein Interaction (PPI) network was constructed using Cytoscape software. Top 10 cross-talk genes were screened, and the expression values of these 10 genes were extracted. ROC analysis was performed by using the pROC package and GGplot2 package of R language to predict the classification accuracy. Results. The overlapping DEG between HT and PD were 107 cross-talk genes. The results revealed that developmental process ( $P$ -value =1.06E-21) was the most significantly enriched biological process, followed by cell differentiation ( $P$ -value =8.49E-18) and immune system process ( $P$ -value =6.78E-11). KEGG analysis showed that Complement and coagulation cascades ( $P$ -value =2.29E-05), Hematopoietic cell lineage ( $P$ -value =2.66E-05), Phospholipase D signaling pathway ( $P$ -value =0.034367878) and Chemokine signaling pathway ( $P$ -value =0.04946333) were significantly enriched. The top 10 genes with most connections were LCE1B, LCE2B, LCE2A, LCE2C, LCE1C, LCE1F, ITGAM, C1QB, TREM2, and CD19. The AUC values of the two datasets of HT were both greater than 65% (GSE18152 = 81.42%, GSE176153 = 68.75%). AUC values of three datasets of PD were all greater than 60% (GSE10334 = 69.23%, GSE16134 = 73.72%, GSE173078 = 81.6%). Conclusions. A genetic cross-talk between HT and PD was detected, whereby LCE family genes appeared to play the most important role.

How Far Are We from the Completion of the Human Protein Interactome Reconstruction?

After more than fifteen years from the first high-throughput experiments for human protein–protein interaction (PPI) detection, we are still wondering how close the completion of the genome-scale human PPI network reconstruction is, what needs to be further explored and whether the biological insights gained from the holistic investigation of the current network are valid and useful. The unique structure of PICKLE, a meta-database of the human experimentally determined direct PPI network developed by our group, presently covering ~80% of the UniProtKB/Swiss-Prot reviewed human complete proteome, enables the evaluation of the interactome expansion by comparing the successive PICKLE releases since 2013. We observe a gradual overall increase of 39%, 182%, and 67% in protein nodes, PPIs, and supporting references, respectively. Our results indicate that, in recent years, (a) the PPI addition rate has decreased, (b) the new PPIs are largely determined by high-throughput experiments and mainly concern existing protein nodes and (c), as we had predicted earlier, most of the newly added protein nodes have a low degree. These observations, combined with a largely overlapping k-core between PICKLE releases and a network density increase, imply that an almost complete picture of a structurally defined network has been reached. The comparative unsupervised application of two clustering algorithms indicated that exploring the full interactome topology can reveal the protein neighborhoods involved in closely related biological processes as transcriptional regulation, cell signaling and multiprotein complexes such as the connexon complex associated with cancers. A well-reconstructed human protein interactome is a powerful tool in network biology and medicine research forming the basis for multi-omic and dynamic analyses.

The Interactions of Small Proline-Rich Proteins with Late Cornified Envelope Proteins are Involved in the Pathogenesis of Psoriasis

Purpose

Psoriasis is a common cutaneous disease with multiple characteristics including inflammation and aberrant keratinocyte proliferation. However, the pathogenesis of psoriasis is not completely clear yet. The objective of this study is to perform an in-depth analysis of the association between SPRR and LCE in the pathogenesis of psoriasis.

Methods

In this study, we explore the differentially expressed genes (DEGs) in psoriasis by analyzing different gene expression profiles obtained from the Gene Expression Omnibus (GEO) database. The DEGs were examined using gene ontology (GO) functional enrichment analysis and protein–protein interactions (PPI) network. Correlation analysis in R studio software was used to analyze the association between SPRR and LCE genes. Further, potential direct protein–protein interactions between SPRR proteins and LCE3D were verified by co-localization observations and co-immunoprecipitation (CO-IP) assays in 293T cells. Also, the expression levels of SPRR and LCE genes were detected in lesional skin of the IMQ-induced psoriasiform dermatitis mice using RT-PCR.

Results

Interestingly, the small proline-rich (SPRR) and late cornified envelope (LCE) genes were identified as a module in the constructed PPI network. And the analysis of the gene expression profile GSE63684 showed that both SPRR family and LCE family genes were significantly upregulated in imiquimod (IMQ) induced psoriasiform dermatitis mice. Also, the correlation analysis in R studio software recognized the association of SPRR and LCE genes, which were further verified by co-localization and co-immunoprecipitation (CO-IP) assays in 293T cells, and the results show that the direct interactions between SPRR2 and LCE3D. Notably, we also found that the expression levels of SPRR and LCE genes were significantly increased in the IMQ-induced psoriasiform dermatitis mice, while specifically decreased under the tazarotene cream treatment, indicating that the SPRR and LCEs were regulated simultaneously in psoriasis.

Conclusion

In summary, our study found that interactions between SPRR proteins and LCE proteins may provide new insights into the pathogenesis of psoriasis.

Deep sequencing of 1320 genes reveals the landscape of protein-truncating variants and their contribution to psoriasis in 19,973 Chinese individuals

Protein-truncating variants (PTVs) have important impacts on phenotype diversity and disease. However, their population genetics characteristics in more globally diverse populations are not well defined. Here, we describe patterns of PTVs in 1320 genes sequenced in 10,539 healthy controls and 9434 patients with psoriasis, all of Han Chinese ancestry. We identify 8720 PTVs, of which 77% are novel, and estimate 88% of all PTVs are deleterious and subject to purifying selection. Furthermore, we show that individuals with psoriasis have a significantly higher burden of PTVs compared to controls (P = 0.02). Finally, we identified 18 PTVs in 14 genes with unusually high levels of population differentiation, consistent with the action of local adaptation. Our study provides insights into patterns and consequences of PTVs.

Methylome profiling of young adults with depression supports a link with immune response and psoriasis

BACKGROUND

Currently the leading cause of global disability, clinical depression is a heterogeneous condition characterised by low mood, anhedonia and cognitive impairments. Its growing incidence among young people, often co-occurring with self-harm, is of particular concern. We recently reported very high rates of depression among first year university students in Northern Ireland, with over 25% meeting the clinical criteria, based on DSM IV. However, the causes of depression in such groups remain unclear, and diagnosis is hampered by a lack of biological markers. The aim of this exploratory study was to examine DNA methylation patterns in saliva samples from individuals with a history of depression and matched healthy controls.

RESULTS

From our student subjects who showed evidence of a total lifetime major depressive event (MDE, n = 186) we identified a small but distinct subgroup (n = 30) with higher risk scores on the basis of co-occurrence of self-harm and attempted suicide. Factors conferring elevated risk included being female or non-heterosexual, and intrinsic factors such as emotional suppression and impulsiveness. Saliva samples were collected and a closely matched set of high-risk cases (n = 16) and healthy controls (n = 16) similar in age, gender and smoking status were compared. These showed substantial differences in DNA methylation marks across the genome, specifically in the late cornified envelope (LCE) gene cluster. Gene ontology analysis showed highly significant enrichment for immune response, and in particular genes associated with the inflammatory skin condition psoriasis, which we confirmed using a second bioinformatics approach. We then verified methylation gains at the LCE gene cluster at the epidermal differentiation complex and at MIR4520A/B in our cases in the laboratory, using pyrosequencing. Additionally, we found loss of methylation at the PSORSC13 locus on chromosome 6 by array and pyrosequencing, validating recent findings in brain tissue from people who had died by suicide. Finally, we could show that similar changes in immune gene methylation preceded the onset of depression in an independent cohort of adolescent females.

CONCLUSIONS

Our data suggests an immune component to the aetiology of depression in at least a small subgroup of cases, consistent with the accumulating evidence supporting a relationship between inflammation and depression. Additionally, DNA methylation changes at key loci, detected in saliva, may represent a valuable tool for identifying at-risk subjects.

Analysis of Laser Therapy Effects on Squamous Cell Carcinoma Patients: A System Biology Study

Introduction: The Mechanism of laser therapy and also its safety are 2 important features of the application of different types of lasers in medicine. This study aims to investigate the critically affected genes after the treatment of squamous cell carcinoma patients. Methods: The gene expression profiles of 4 squamous cell carcinoma patients that were treated via chemoradiotherapy (CRT) plus the laser and 3 similar patients without laser exposure from Gene Expression Omnibus (GEO) were downloaded and were screened to find critical genes via network analysis. The STRING database, Cytoscape software, and the Clue GO plug-in of Cytoscape software were used. Results: The genes HSX70 and NCC27 were determined as neighbors and HSPA1B, CLIC1, RAB13, PPIF, and LCE3D as hub genes. The over-expression of LCE3D was interpreted as the side effect of laser therapy. Apoptosis and the cell cycle were the dominant biological processes regulated by the HSP molecules in the laser-treated patients. Conclusion: The laser affected the main biological processes and simultaneously issued side effects.

Tissue-Specific Gene Expression during Productive Human Papillomavirus 16 Infection of Cervical, Foreskin, and Tonsil Epithelium

Epidemiological data confirm a much higher incidence of high-risk human papillomavirus 16 (HPV16)-mediated carcinogenesis of the cervical epithelium than for other target sites. In order to elucidate tissue-specific responses to virus infection, we compared gene expression changes induced by productive HPV16 infection of cervical, foreskin, and tonsil organotypic rafts. These rafts closely mimic persistent HPV16 infection, long before carcinogenesis sets in. The total number of gene expression changes varied considerably across the tissue types, with only 32 genes being regulated in common. Among them, we confirmed the Kelch-like family protein KLHL35 and the laminin-5 complex to be upregulated and downregulated, respectively, in all the three tissues. HPV16 infection induces upregulation of genes involved in cell cycle control, cell division, mitosis, DNA replication, and DNA damage repair in all the three tissues, indicative of a hyperproliferative environment. In the cervical and tonsil epithelium, we observe significant downregulation of genes involved in epidermis development, keratinocyte differentiation, and extracellular matrix organization. On the other hand, in HPV16-positive foreskin (HPV16 foreskin) tissue, several genes involved in interferon-mediated innate immunity, cytokine signaling, and cellular defenses were downregulated. Furthermore, pathway analysis and experimental validations identified important cellular pathways like STAT1 and transforming growth factor β (TGF-β) to be differentially regulated among the three tissue types. The differential modulation of important cellular pathways like TGF-β1 and STAT1 can explain the sensitivity of tissues to HPV cancer progression.IMPORTANCE Although the high-risk human papillomavirus 16 infects anogenital and oropharyngeal sites, the cervical epithelium has a unique vulnerability to progression of cancer. Host responses during persistent infection and preneoplastic stages can shape the outcome of cancer progression in a tissue-dependent manner. Our study for the first time reports differential regulation of critical cellular functions and signaling pathways during productive HPV16 infection of cervical, foreskin, and tonsil tissues. While the virus induces hyperproliferation in infected cells, it downregulates epithelial differentiation, epidermal development, and innate immune responses, according to the tissue type. Modulation of these biological functions can determine virus fitness and pathogenesis and illuminate key cellular mechanisms that the virus employs to establish persistence and finally initiate disease progression.

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.

DNA methylation age is not affected in psoriatic skin tissue

Background

Psoriasis (Ps) is a common chronic inflammatory skin disease. The keratinocytes of psoriatic skin defy normal apoptosis and exhibit active cell proliferation. Aberrant DNA methylation (DNAm) has been suggested relevant through regulating the expression of Ps susceptibility genes. However, it is unclear whether the biological age inferred from DNA methylome is affected.

Results

To address the above issue, we applied a recently developed methylation clock model to our Chinese Han population dataset, which includes DNAm data of 114 involved psoriatic skin tissues (PP) and 41 uninvolved psoriatic skin tissues (PN) from Ps patients, and 62 normal skin tissues (NN) from health controls. We first confirmed the applicability of the clock in PN and NN. We then showed that PP samples have largely unchanged DNAm age, and that no association was observed between available clinical features and DNAm age acceleration. Examination of genome-wide CpGs yielded age-associated CpGs with concordant age-association coefficients among the three groups, which was also supported by an external dataset. We also interestingly observed two clock CpGs differentially methylated between PP and PN.

Conclusions

Overall, our results suggest no significant alteration in DNAm age in PN and PP. Therefore, the increase in keratinocyte proliferation and alteration in DNAm caused by Ps may not affect the biological age of psoriatic skin tissue.

Electronic supplementary material

The online version of this article (10.1186/s13148-018-0584-y) contains supplementary material, which is available to authorized users.

Association between LCE gene polymorphisms and psoriasis vulgaris among Mongolians from Inner Mongolia

The late cornified envelope (LCE) gene cluster is located on chromosome 1q21, including LCE1–LCE6. Several single nucleotide polymorphisms (SNPs) in the LCE cluster were associated with susceptibility to psoriasis in Chinese population. However, there is no report on the relationship in ethnic minority areas in China. This study aimed to investigate the association between the gene polymorphisms of LCE1B, LCE1C, LCE3A, LCE3D and psoriasis vulgaris among Mongolians from Inner Mongolia. Totally, 305 Mongolians with psoriasis vulgaris (PsV) and 383 healthy controls were enrolled in the study from 2006 to 2015. 7 SNPs including rs6701216, rs4112788, rs12023196, rs512208, rs4845454, rs4085613 and rs1886734, were selected for genotyping with ligase detection reaction (LDR). Statistical analysis was performed for comparisons of allele frequencies and genotype frequencies between the patient group and the control group. In this study, excluding rs4085613 and rs1886734, differences were detected in the allele frequencies of other 5 SNPs between the patients and controls. Genotype analysis showed that under the recessive inheritance model, the genotype frequencies of rs4845454, rs4112788 differed between the patients and controls (all p < 0.00 5).Under the dominant and the recessive model, the genotype frequencies of rs6701216, rs12023196 and rs512208 significantly differed between the patients and controls. The LD analysis showed that strong LD existed between rs6701216 and rs12023196, rs4845454 and rs4085613, rs4845454 and rs1886734, and rs4085613 and rs1886734. The SNPs rs6701216, rs4112788, rs12023196, rs512208 and rs4845454 in the LCE gene were associated with psoriasis vulgaris among Mongolians from Inner Mongolia.

Transcriptome analysis of airborne PM2.5-induced detrimental effects on human keratinocytes

Ambient air pollution is becoming more severe worldwide, posing a serious threat to human health. Fine airborne particles of particulate matter (PM_2.5) show higher cytotoxicity than other coarse fractions. Indeed, PM_2.5 induces cardiovascular or respiratory damage; however, few studies have evaluated the detrimental effect of PM_2.5 to normal human skin. We used a next-generation sequencing-based (RNA-Seq) method with transcriptome and Gene Ontology (GO) enrichment analysis to determine the harmful influences of PM_2.5 on human normal epidermal keratinocytes. DAVID analysis showed that the most significantly enriched GO terms were associated with epidermis-related biological processes such as "epidermis development (GO: 0008544)" and "keratinocyte differentiation (GO: 0030216)", suggesting that PM_2.5 has some deleterious effects to the human epidermis. In addition, Ingenuity Pathway Analysis predicted inflammation-related signaling as one of the major PM_2.5-induced signaling pathways, and pro-inflammatory cytokines as upstream regulators with symptoms similar to psoriasis as downstream effects. PM_2.5 caused considerable changes in the expression of pro-inflammatory cytokines and psoriatic skin disease-related genes, might lead to epidermal dysfunctions. Our results might help to understand the mechanism of air pollution-induced skin barrier perturbation and contribute to the development of a new strategy for the prevention or recovery of the consequent damage.

Copy number variations in Saudi family with intellectual disability and epilepsy

Background

Epilepsy is genetically complex but common brain disorder of the world affecting millions of people with almost of all age groups. Novel Copy number variations (CNVs) are considered as important reason for the numerous neurodevelopmental disorders along with intellectual disability and epilepsy. DNA array based studies contribute to explain a more severe clinical presentation of the disease but interoperation of many detected CNVs are still challenging.

Results

In order to study novel CNVs with epilepsy related genes in Saudi family with six affected and two normal individuals with several forms of epileptic seizures, intellectual disability (ID), and minor dysmorphism, we performed the high density whole genome Agilent sure print G3 Hmn CGH 2x 400 K array-CGH chips analysis. Our results showed de novo deletions, duplications and deletion plus duplication on differential chromosomal regions in the affected individuals that were not shown in the normal fathe and normal kids by using Agilent CytoGenomics 3.0.6.6 softwear. Copy number gain were observed in the chromosome 1, 16 and 22 with LCE3C, HPR, GSTT2, GSTTP2, DDT and DDTL genes respectively whereas the deletions observed in the chromosomal regions 8p23-p21 (4303127–4337759) and the potential gene in this region is CSMD1 (OMIM: 612279). Moreover, the array CGH results deletions and duplication were also validated by using primer design of deleted regions utilizing the flanked SNPs using simple PCR and also by using quantitative real time PCR.

Conclusions

We found some of the de novo deletions and duplication in our study in Saudi family with intellectual disability and epilepsy. Our results suggest that array-CGH should be used as a first line of genetic test for epilepsy except there is a strong indication for a monogenic syndrome. The advanced high through put array-CGH technique used in this study aim to collect the data base and to identify new mechanisms describing epileptic disorder, may help to improve the clinical management of individual cases in decreasing the burden of epilepsy in Saudi Arabia.

Trying to understand the genetics of atopic dermatitis

Atopic dermatitis (AD) is a common and complex skin disease associated with both genetic and environmental factors. Loss-of-function mutations in the filaggrin gene, encoding a structural protein with an important role in epidermal barrier function, constitutes a well recognised susceptibility locus for AD. Further, genome-wide association studies (GWAS), including large meta-analyses, have discovered 38 additional susceptibility loci with genome-wide significance. However, the reported variations only explain a fraction of the overall heritability of AD. Here, we summarize the current knowledge of the role of filaggrin and the epidermal differentiation complex as well as the results of GWAS, with an emphasis on novel findings and observations made in the past two years. Additionally, we present first results of exome sequencing for AD and discuss novel therapeutic strategies.

Interactions of the Immune System with Skin and Bone Tissue in Psoriatic Arthritis: A Comprehensive Review

Cutaneous psoriasis (e.g., psoriasis vulgaris (PsV)) and psoriatic arthritis (PsA) are complex heterogeneous diseases thought to have similar pathophysiology. The soluble and cellular mediators of these closely related diseases are being elucidated through genetic approaches such as genome-wide association studies (GWAS), as well as animal and molecular models. Novel therapeutics targeting these mediators (IL-12, IL-23, IL-17, IL-17 receptor, TNF) are effective in treating both the skin and joint manifestations of psoriasis, reaffirming the shared pathophysiology of PsV and PsA. However, the molecular and cellular interactions between skin and joint disease have not been well characterized. Clearly, PsV and PsA are highly variable in terms of their clinical manifestations, and this heterogeneity can partially be explained by differences in HLA-associations (HLA-Cw*0602 versus HLA-B*27, for example). In addition, there are numerous other genetic susceptibility loci (LCE3, CARD14, NOS2, NFKBIA, PSMA6, ERAP1, TRAF3IP2, IL12RB2, IL23R, IL12B, TNIP1, TNFAIP3, TYK2) and geoepidemiologic factors that contribute to the wide variability seen in psoriasis. Herein, we review the complex interplay between the genetic, cellular, ethnic, and geographic mediators of psoriasis, focusing on the shared mechanisms of PsV and PsA.

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

HLA-Cw6 is one of the most associated alleles in psoriasis. Recently, Late Cornified Envelop 3 (LCE3) genes were identified as a susceptibility factor for psoriasis. Some population showed epistatic interaction of LCE3 risk variants with HLA-Cw6, while some population failed to show any association. We determined the associations of a 32.2 kb deletion comprising LCE3C-3B genes and three SNPs (rs1886734, rs4112788; rs7516108) at the LCE3 gene cluster among the psoriasis patients in India. All three SNPs at the LCE3 gene cluster failed to show any association. In contrary, for patients with HLA-Cw6 allele, all three SNPs and the LCE3C-3B deletion showed significant associations. While, all five LCE3 genes were upregulated in psoriatic skin, only LCE3A showed significant overexpression with homozygous risk genotype compared to the non-risk genotype. LCE3B also showed significant overexpression in patients with HLA-Cw6 allele. Moreover, LCE3A showed significantly higher expression in patients bearing homozygous risk genotype in presence of HLA-Cw6 allele but not in those having non-risk genotype, demonstrating the combined effect of HLA-Cw6 allele and risk associated genotype near LCE3A gene. Integration of genetic and gene expression data thus allowed us to identify the actual disease variants at the LCE3 cluster among the psoriasis patients in India.