GWAS meta-analysis of psoriasis identifies new susceptibility alleles impacting disease mechanisms and therapeutic targets

The Aryl Hydrocarbon Receptor (AHR): Peacekeeper of the Skin

In the last decade, the aryl hydrocarbon receptor (AHR) has emerged as a critical peacekeeper for the maintenance of healthy skin. The evolutionary conservation of AHR implied physiological functions for this receptor, beyond the detoxification of man-made compounds, a notion further supported by the existence of physiological AHR ligands, notably derivates of tryptophan by the host and host microbiome. The UV light-derived ligand, 6-formylindolo[3,2-b]carbazole (FICZ), anticipated a role for AHR in skin, a UV light-exposed organ, where physiological AHR activation promotes a healthy skin barrier and constrains inflammation. The clinical development of tapinarof, the first topical AHR modulating drug for inflammatory skin disease, approved by the FDA for mild-to-moderate psoriasis and poised for approval in atopic dermatitis, supports the therapeutic targeting of the AHR pathway to harness its beneficial effect in skin inflammation. Here, we describe how a tightly controlled, physiological activation of the AHR pathway maintains skin homeostasis, and discuss how the pathway is dysregulated in psoriasis and atopic dermatitis, identifying areas offering opportunities for alternative therapeutic approaches, for further investigation.

RNA Sequencing Reveals the Long Non-Coding RNA Signature in Psoriasis Keratinocytes and Identifies CYDAER as a Long Non-Coding RNA Regulating Epidermal Differentiation

Psoriasis is a common chronic inflammatory skin disease determined by genetic and environmental factors, resulting in the activation of IL-23/IL-17-mediated immune response, epidermal hyperproliferation, and keratinocyte activation. Long non-coding RNAs (lncRNAs) are non-protein-coding transcripts > 500 nucleotides with diverse regulatory functions; their role in epidermal dysfunction in psoriasis is poorly understood. To identify epidermal transcripts with potential roles in psoriasis, including lncRNAs, we performed RNA sequencing on keratinocytes from psoriasis and healthy skin. We identified 889 differentially expressed lncRNAs, many of which with yet unknown functions. RP11-295G20.2 was identified as a lncRNA significantly induced in psoriasis keratinocytes, and this was verified by qRT-PCR and by single-molecule in situ hybridisation. Analysis of subcellular fractions of epidermis revealed a cytoplasmic localisation in line with results of single molecule in situ hybridisation. We report that RP11-295G20.2 has a skin-enriched expression, and within skin it is mainly expressed in suprabasal epidermal layers. Moreover, RP11-295G20.2 is induced by the key psoriasis cytokine IL-17A and shows a dynamic regulation during keratinocyte differentiation with upregulation during early differentiation and downregulation in the late stage. Knockdown of RP11-295G20.2 in keratinocytes promotes terminal differentiation. Based on our findings, we named RP11-295G20.2 Cytoplasmic Differentiation-Associated Epidermal RNA, CYDAER. In summary, our study provides a comprehensive characterisation of the non-coding RNA landscape of psoriasis keratinocytes and identifies CYDAER as a skin-enriched lncRNA regulating keratinocyte differentiation. Our data suggest that overexpression of CYDAER may contribute to altered differentiation in psoriatic epidermis.

IL-1 signaling enrichment in inflammatory skin disease loci with higher-risk allele frequencies in African ancestry

Inflammatory skin diseases (ISDs) exhibit varying prevalence across different ancestry background and geographical regions. Genetic research for complex ISDs has predominantly centered on European Ancestry (EurA) populations and genetic effects on immune cell responses but generally failed to consider contributions from other cell types in skin. Here, we utilized 273 genetic signals from seven different ISDs: acne, alopecia areata (AA), atopic dermatitis (AD), psoriasis, systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and vitiligo, to demonstrate enriched IL1 signaling in keratinocytes, particularly in signals with higher risk allele frequencies in the African ancestry. Using a combination of ATAC-seq, Bru-seq, and promoter capture Hi-C, we revealed potential regulatory mechanisms of the acne locus on chromosome 2q13. We further demonstrated differential responses in keratinocytes upon IL1β stimulation, including the pro-inflammatory mediators CCL5, IL36G, and CXCL8. Taken together, our findings highlight IL1 signaling in epidermal keratinocytes as a contributor to ancestry-related differences in ISDs.

scTWAS Atlas: an integrative knowledgebase of single-cell transcriptome-wide association studies

Single-cell transcriptome-wide association studies (scTWAS) is a new method for conducting TWAS analysis at the cellular level to identify gene-trait associations with higher precision. This approach helps overcome the challenge of interpreting cell-type heterogeneity in traditional TWAS results. As the field of scTWAS rapidly advances, there is a growing need for additional database platforms to integrate this wealth of data and knowledge effectively. To address this gap, we present scTWAS Atlas (https://ngdc.cncb.ac.cn/sctwas/), a comprehensive database of scTWAS information integrating literature curation and data analysis. The current version of scTWAS Atlas amasses 2,765,211 associations encompassing 34 traits, 30 cell types, 9 cell conditions and 16,470 genes. The database features visualization tools, including an interactive knowledge graph that integrates single-cell expression quantitative trait loci (sc-eQTL) and scTWAS associations to build a multi-omics level regulatory network at the cellular level. Additionally, scTWAS Atlas facilitates cross-cell-type analysis, highlighting cell-type-specific and shared TWAS genes. The database is designed with user-friendly interfaces and allows for easy browsing, searching, and downloading of relevant information. Overall, scTWAS Atlas is instrumental in exploring the genetic regulatory mechanisms at the cellular level and shedding light on the role of various cell types in biological processes, offering novel insights for human health research.

Genomic strategies for drug repurposing

Functional genomics, a multidisciplinary subject, investigates the functions of genes and their products in biological systems to better understand diseases and find new drugs. Drug repurposing is an economically efficient approach that entails discovering novel therapeutic applications for already-available medications. Genomics enables the identification of illness and therapeutic molecular characteristics and interactions, which in turn facilitates the process of drug repurposing. Techniques like gene expression profiling and Mendelian randomization are helpful in identifying possible medication candidates. Progress in computer science allows for the investigation and modeling of gene expression networks that involve large amounts of data. The amalgamation of data concerning DNA, RNA, and protein functions bears similarity to pharmacogenomics, a crucial aspect in crafting cancer therapeutics. Functional genomics in drug discovery, particularly for cancer, is still not thoroughly investigated, despite the existence of a significant amount of literature on the subject. Next-generation sequencing and proteomics present highly intriguing opportunities. Publicly available databases and mining techniques facilitate the development of cancer treatments based on functional genomics. Broadening the exploration and utilization of functional genomics holds significant potential for advancing drug discovery and repurposing, particularly within the realm of oncology.

Exploring the Link Between Genetic Predictors of Cardiovascular Disease and Psoriasis

Importance

The epidemiological link between immune-mediated diseases (IMIDs) and cardiovascular disease has often been attributed to systemic inflammation. However, the direction of causality and the biological mechanisms linking cardiovascular disease with IMIDs are incompletely understood. Given the robust epidemiological association and the growing body of supportive mechanistic evidence, psoriasis is an exemplary IMID model for exploring this relationship.

Objective

To assess the bidirectional relationships between genetic predictors of psoriasis and the 2 major forms of cardiovascular disease, coronary artery disease (CAD) and stroke, and to evaluate the association between genetic predictors of cardiovascular disease with 9 other IMIDs.

Design, Setting, and Participants

This was a genetic association study using mendelian randomization (MR), a powerful genetic tool to help distinguish causation from associations observed in epidemiological studies, to provide supportive evidence for causality between traits. The study conducted 2-sample MR analyses using summary-level data from large-scale genome-wide association meta-analysis studies (GWAS) for each trait. The analysis focused on individuals of European descent from GWAS meta-analyses, involving CAD, stroke, psoriasis, and 9 other IMIDs. Data were analyzed from January 2023 to May 2024.

Exposures

Genetic predictors of CAD, stroke, psoriasis, and 9 other IMIDs.

Main Outcomes and Measures

The primary outcomes were the associations of genetic predictors of CAD and stroke with the risk of psoriasis and 9 other IMIDs, determined using inverse-variance weighted (IVW) MR estimates.

Results

This study included 181 249 cases and 1 165 690 controls with CAD, 110 182 cases and 1 503 898 controls with stroke, 36 466 cases and 458 078 controls with psoriasis, for a total of approximately 3 400 000 individuals, and 9 other IMIDs. In contrast to previous assumptions, genetic predictors of psoriasis were found to have no association with CAD or stroke. In the reverse direction, genetic predictors of both CAD (MR estimate IVW odds ratio [OR], 1.07; 95% CI, 1.04-1.10; P = .003) and stroke (IVW OR, 1.22; 95% CI, 1.05-1.41; P = .01) were found to have risk-increasing associations with psoriasis. Adjusting for stroke rendered the associations of genetically predicted CAD with psoriasis risk nonsignificant (and vice versa), suggesting that a shared effect underlying genetic risk for CAD and stroke associates with increased psoriasis risk. No risk-increasing associations were observed for genetic predictors of cardiovascular disease with other common IMIDs, including rheumatoid arthritis and inflammatory bowel disease.

Conclusions and Relevance

Findings of this mendelian randomization study indicate that genetic predictors of cardiovascular disease were associated with increased psoriasis risk with no reciprocal effect or association with other IMIDs. Elucidating mechanisms underpinning this association could lead to novel therapeutic approaches in both diseases.

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.

Exposure to Air Pollution, Genetic Susceptibility, and Psoriasis Risk in the UK

IMPORTANCE

Psoriasis is a common autoinflammatory disease influenced by complex interactions between environmental and genetic factors. The influence of long-term air pollution exposure on psoriasis remains underexplored.

OBJECTIVE

To examine the association between long-term exposure to air pollution and psoriasis and the interaction between air pollution and genetic susceptibility for incident psoriasis.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study used data from the UK Biobank. The analysis sample included individuals who were psoriasis free at baseline and had available data on air pollution exposure. Genetic analyses were restricted to White participants. Data were analyzed between November 1 and December 10, 2023.

EXPOSURES

Exposure to nitrogen dioxide (NO2), nitrogen oxides (NOx), fine particulate matter with a diameter less than 2.5 µm (PM2.5), and particulate matter with a diameter less than 10 µm (PM10) and genetic susceptibility for psoriasis.

MAIN OUTCOMES AND MEASURES

To ascertain the association of long-term exposure to NO2, NOx, PM2.5, and PM10 with the risk of psoriasis, a Cox proportional hazards model with time-varying air pollution exposure was used. Cox models were also used to explore the potential interplay between air pollutant exposure and genetic susceptibility for the risk of psoriasis incidence.

RESULTS

A total of 474 055 individuals were included, with a mean (SD) age of 56.54 (8.09) years and 257 686 (54.36%) female participants. There were 9186 participants (1.94%) identified as Asian or Asian British, 7542 (1.59%) as Black or Black British, and 446 637 (94.22%) as White European. During a median (IQR) follow-up of 11.91 (11.21-12.59) years, 4031 incident psoriasis events were recorded. There was a positive association between the risk of psoriasis and air pollutant exposure. For every IQR increase in PM2.5, PM10, NO2, and NOx, the hazard ratios (HRs) were 1.41 (95% CI, 1.35-1.46), 1.47 (95% CI, 1.41-1.52), 1.28 (95% CI, 1.23-1.33), and 1.19 (95% CI, 1.14-1.24), respectively. When comparing individuals in the lowest exposure quartile (Q1) with those in the highest exposure quartile (Q4), the multivariate-adjusted HRs were 2.01 (95% CI, 1.83-2.20) for PM2.5, 2.21 (95% CI, 2.02-2.43) for PM10, 1.64 (95% CI, 1.49-1.80) for NO2, and 1.34 (95% CI, 1.22-1.47) for NOx. Moreover, significant interactions between air pollution and genetic predisposition for incident psoriasis were observed. In the subset of 446 637 White individuals, the findings indicated a substantial risk of psoriasis development in participants exposed to the highest quartile of air pollution levels concomitant with high genetic risk compared with those in the lowest quartile of air pollution levels with low genetic risk (PM2.5: HR, 4.11; 95% CI, 3.46-4.90; PM10: HR, 4.29; 95% CI, 3.61-5.08; NO2: HR, 2.95; 95% CI, 2.49-3.50; NOx: HR, 2.44; 95% CI, 2.08-2.87).

CONCLUSIONS AND RELEVANCE

In this prospective cohort study of the association between air pollution and psoriasis, long-term exposure to air pollution was associated with increased psoriasis risk. There was an interaction between air pollution and genetic susceptibility on psoriasis risk.

Functional Genomics and Insights into the Pathogenesis and Treatment of Psoriasis

Psoriasis is a lifelong, systemic, immune mediated inflammatory skin condition, affecting 1-3% of the world's population, with an impact on quality of life similar to diseases like cancer or diabetes. Genetics are the single largest risk factor in psoriasis, with Genome-Wide Association (GWAS) studies showing that many psoriasis risk genes lie along the IL-23/Th17 axis. Potential psoriasis risk genes determined through GWAS can be annotated and characterised using functional genomics, allowing the identification of novel drug targets and the repurposing of existing drugs. This review is focused on the IL-23/Th17 axis, providing an insight into key cell types, cytokines, and intracellular signaling pathways involved. This includes examination of currently available biological treatments, time to relapse post drug withdrawal, and rates of primary/secondary drug failure, showing the need for greater understanding of the underlying genetic mechanisms of psoriasis and how they can impact treatment. This could allow for patient stratification towards the treatment most likely to reduce the burden of disease for the longest period possible.

Evidence for the gut-skin axis: Common genetic structures in inflammatory bowel disease and psoriasis

BACKGROUND

Inflammatory bowel disease (IBD) and psoriasis (Ps) are common immune-mediated diseases that exhibit clinical comorbidity, possibly due to a common genetic structure. However, the exact mechanism remains unknown.

METHODS

The study population consisted of IBD and Ps genome-wide association study (GWAS) data. Genetic correlations were first evaluated. Then, the overall evaluation employed LD score regression (LDSC), while the local assessment utilized heritability estimation from summary statistics (HESS). Causality assessment was conducted through two-sample Mendelian randomization (2SMR), and genetic overlap analysis utilized the conditional false discovery rate/conjunctional FDR (cond/conjFDR) method. Finally, LDSC applied to specifically expressed genes (LDSC-SEG) was performed at the tissue level. For IBD and Ps-specific expressed genes, genetic correlation, causality, shared genetics, and trait-specific associated tissues were methodically examined.

RESULTS

At the genomic level, both overall and local genetic correlations were found between IBD and Ps. MR analysis indicated a positive causal relationship between Ps and IBD. The conjFDR analysis with a threshold of < 0.01 identified 43 loci shared between IBD and Ps. Subsequent investigations into disease-associated tissues indicated a close association of IBD and Ps with whole blood, lung, spleen, and EBV-transformed lymphocytes.

CONCLUSION

The current research offers a novel perspective on the association between IBD and Ps. It contributes to an enhanced comprehension of the genetic structure and mechanisms of comorbidities in both diseases.

Multi-Omics Approach to Improved Diagnosis and Treatment of Atopic Dermatitis and Psoriasis

Psoriasis and atopic dermatitis fall within the category of cutaneous immune-mediated inflammatory diseases (IMIDs). The prevalence of IMIDs is increasing in industrialized societies, influenced by both environmental changes and a genetic predisposition. However, the exact immune factors driving these chronic, progressive diseases are not fully understood. By using multi-omics techniques in cutaneous IMIDs, it is expected to advance the understanding of skin biology, uncover the underlying mechanisms of skin conditions, and potentially devise precise and personalized approaches to diagnosis and treatment. We provide a narrative review of the current knowledge in genomics, epigenomics, and proteomics of atopic dermatitis and psoriasis. A literature search was performed for articles published until 30 November 2023. Although there is still much to uncover, recent evidence has already provided valuable insights, such as proteomic profiles that permit differentiating psoriasis from mycosis fungoides and β-defensin 2 correlation to PASI and its drop due to secukinumab first injection, among others.

Genome-Wide Differential Transcription of Long Noncoding RNAs in Psoriatic Skin

Long noncoding RNAs (lncRNAs) may contribute to the formation of psoriatic lesions. The present study's objective was to identify long lncRNA genes that are differentially expressed in patient samples of psoriasis through computational analysis techniques. By using previously published RNA sequencing data from psoriatic and healthy patients (n = 324), we analysed the differential expression of lncRNAs to determine transcripts of heightened expression. We computationally screened lncRNA transcripts as annotated by GENCODE across the human genome and compared transcription in psoriatic and healthy samples from two separate studies. We observed 54 differentially expressed genes as seen in two independent datasets collected from psoriasis and healthy patients. We also identified the differential expression of LINC01215 and LINC1206 associated with the cell cycle pathway and psoriasis pathogenesis. SH3PXD2A-AS1 was identified as a participant in the STAT3/SH3PXD2A-AS1/miR-125b/STAT3 positive feedback loop. Both the SH3PXD2A-AS1 and CERNA2 genes have already been recognised as part of the IFN-γ signalling pathway regulation. Additionally, EPHA1-AS1, CYP4Z2P and SNHG12 gene upregulation have all been previously linked to inflammatory skin diseases. Differential expression of various lncRNAs affects the pathogenesis of psoriasis. Further characterisation of lncRNAs and their functions are important for developing our understanding of psoriasis.