The WNT signalling pathway in systemic sclerosis
Date
2016-10-19
Authors
Frost, Jacqueline Michelle
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Abstract
Systemic sclerosis (SSc) is a complex autoimmune disease involving the immune system, vasculature and extracellular matrix. Dysregulation of the Wnt pathway has been implicated in the development of fibrosis in SSc and is proposed to contribute to a failure to maintain tissue homeostasis and appropriate immune response.
The objective of this research study was to explore the role of altered Wnt pathway gene regulation in the development of fibrosis in black South African SSc patients with early, diffuse disease (dcSSc). The first aim was to examine differential gene expression in the Wnt pathway and the second aim to examine differential expression of microRNAs that potentially target Wnt pathway genes.
Skin biopsies from eight black South African patients with dcSSc, samples from both the forearm (affected skin) and the back (unaffected skin), and eight ethnically matched healthy control skin samples were examined. The Wnt pathway RT2 Profiler qPCR Array (84 Wnt pathway genes) was used to assess differential gene expression, single gene TaqMan assays for validation and small RNA-sequencing for microRNA analysis. Data analysis was done using HTqPCR, NormqPCR and DESeq2 software.
Gene expression patterns revealed five distinct differentially expressed gene clusters. Two clusters displayed genes that were upregulated in both affected and unaffected SSc skin compared to controls (one showing a more heterogeneous pattern than the other). Another showed consistently decreased gene expression and two revealed more complex patterns responsible for delineating the patients into two groups. The gene
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expression was validated for five genes. The sRNA-seq data showed differential expression of 31 miRNAs that target the Wnt pathway genes, including miR-335 and miR204 that are important regulators of normal tissue development. Other dysregulated miRNAs have been linked to fibrotic and autoimmune diseases.
In this group of dcSSc patients, there is differential gene expression of several Wnt pathway genes that delineate the patients into two distinct groups. This could point to differences in disease aetiology leading to distinct clinical outcomes, such as inflammation. Together with the differentially expressed microRNAs, the findings indicate a substantial contribution of epigenetic changes to the pathogenesis, progression and diverse clinical features of dcSSc.
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A thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment for the degree of Doctor of Philosophy
2016