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Transcriptome analysis of psoriasis in a large case-control sample: RNA-seq provides insights into disease mechanisms

ABSTRACT: To increase our understanding of psoriasis, we utilized RNA-seq to assay the transcriptomes of lesional psoriatic and normal skin. We sequenced polyadenylated RNA-derived cDNAs from 92 psoriatic and 82 normal punch biopsies, generating an average of ~38 million single-end 80-bp reads per sample. Comparison of 42 samples* examined by both RNA-seq and microarray [GSE13355] revealed marked differences in sensitivity, with transcripts identified only by RNA-seq having much lower expression than those also identified by microarray. RNA-seq identified many more differentially expressed transcripts enriched in immune system processes. Weighted gene co-expression network analysis (WGCNA) revealed multiple modules of coordinately expressed epidermal differentiation genes, overlapping significantly with genes regulated by the long non-coding RNA TINCR, its target gene, staufen-1 (STAU1), the p63 target gene ZNF750, and its target KLF4. Other coordinately expressed modules were enriched for lymphoid and/or myeloid signature transcripts and genes induced by IL-17 in keratinocytes. Dermally-expressed genes were significantly down-regulated in psoriatic biopsies, most likely due to expansion of the epidermal compartment. These results demonstrate the power of WGCNA to elucidate gene regulatory circuits in psoriasis, and emphasize the influence of tissue architecture in both differential expression and co-expression analysis. *The list of 42 samples examined by both RNA-seq and microarray is provided in the 'MAoverlappedsamples.txt'.

ORGANISM(S): Homo sapiens

PROVIDER: GSE54456 | GEO | 2014/01/29

SECONDARY ACCESSION(S): PRJNA236547

REPOSITORIES: GEO

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Project description:IL-20 cytokines are involved in the establishment of psoriasis, a common chronic skin inflammation epidemiologically associated with metabolic syndrome, but molecular mechanisms underlying their over-expression remain to be elucidated. We find that keratinocytes (KCs) expressed IL-20 and lymphocytes expressed IL-22 cytokines up-regulation occurs at post-transcriptional level with stabilization of their RNA messengers. Looking at psoriatic epidermis, we observe that the p38/MK2 pathway is not activated but that the RNA-binding protein (RBP) HuR re-localizes in keratinocytes cytoplasm, suggesting post-transcriptional regulation of numerous mRNAs. HuR ribonucleoprotein immunoprecipitations analyzed by high-throughput sequencing (RIP-Seq) identify potential pre-mature and mature RNA targets for uninvolved and involved skin and confirms that HuR activity is displaced from the nucleus to the cytoplasm. Numerous psoriasis up-regulated transcripts are HuR targets and HuR knockdown reduces expression of transcripts like beta-defensin-2, CXCL-10 or IL-2, suggesting an implication of HuR in pathophysiological processes such as morphological, immune and metabolic inflammatory responses. Finally, metabolic disorders affecting psoriatic keratinocytes are responsible for HuR cytoplasmic localization since a decreased activity of the cellular metabolic sensor AMPK, that is observed in human psoriatic epidermis, is sufficient to promote HuR cytosolic localization as well as IL-20 over-production both in human keratinocytes and in vivo in mouse epidermis where it then initiates psoriasis-like histological changes. These results may provide insights into molecular links between metabolism and post-transcriptional networks during chronic inflammation, as illustrated in psoriasis by mechanisms connecting AMPK, HuR and IL-20. Analysis of HuR-binding RNA in uninvolved versus involved psoriatic samples by RIP-Seq. Samples from five different patients were used for both uninvolved and involved skin. RIP-Seq was also made using a control IgG.

Project description:Background: Plaque psoriasis is a chronic autoimmune disorder characterized by the development of red scaly plaques. To date psoriasis lesional skin transcriptome has been extensively studied, whereas only few proteomic studies of psoriatic skin are available. Aim: The aim of this study was to compare protein expression patterns of lesional and normally looking skin of psoriasis patients with skin of the healthy volunteers, reveal differentially expressed proteins and identify changes in cell metabolism caused by the disease. Methods: Skin samples of normally looking and lesional skin donated by psoriasis patients (n = 5) and samples of healthy skin donated by volunteers (n = 5) were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). After protein identification and data processing, the set of differentially expressed proteins was subjected to protein ontology analysis to characterize changes in biological processes, cell components and molecular functions in the patients' skin compared to skin of the healthy volunteers. Results: The performed analysis identified 405 and 59 differentially expressed proteins in lesional and normally looking psoriatic skin compared to healthy control. We discovered decreased expression of KNG1, APOE, HRG, THBS1 and PLG in normally looking skin of the patients. Presumably, these changes were needed to protect the epidermis from spontaneous activation of kallikrein-kinin system and delay the following development of inflammatory response. In lesional skin, we identified several large groups of proteins with coordinated expression. Mainly, these proteins were involved in different aspects of protein and RNA metabolism, namely ATP synthesis and consumption; intracellular trafficking of membrane-bound vesicles, pre-RNA processing, translation, chaperoning and degradation in proteasomes/immunoproteasomes. Conclusion: Our findings explain the molecular basis of metabolic changes caused by disease in skin lesions, such as faster cell turnover and higher metabolic rate. They also indicate on downregulation of kallikrein-kinin system in normally looking skin of the patients that would be needed to delay exacerbation of the disease.

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Transcriptome analysis of psoriasis in a large case-control sample: RNA-seq provides insights into disease mechanisms

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