Date of Award

2018

Degree Name

Doctor of Philosophy (College of Medicine)

First Supervisor

Associate Professor Mark Fear

Abstract

The eponymous progressive palmar fibromatosis described by Guillaume Dupuytren in 1831 is a common and debilitating disease with limited treatment options and high rates of recurrence after intervention. Dupuytren’s disease has been generally accepted as predominantly affecting Northern European individuals; Dupuytren’s disease is sometimes referred to as “Vikings Disease” as an attribution to this ethnic origin. Its familial occurrence in all communities is suggestive of Mendelian inheritance as an autosomal dominant disease with incomplete penetrance. The genetic and molecular basis of Dupuytren’s disease (DD) has been the focus of many studies, with increasingly sophisticated approaches since the sequencing of the human genome in 2003. However, whilst the pathology of the progressive fibrosis is well understood, the etiology and molecular triggers of the disease remain unknown. This study has investigated the genetic basis of Dupuytren’s disease in families and the population of Western Australia. The study involved a tripartite investigation in patients from three different cohorts. The DNA of four DD affected people within a four-generation family with autosomal dominant inheritance of DD was submitted for whole exome sequencing (WES) which initially identified 43 candidate genes with non-synonymous heterozygous rare variants. Two candidate genes, EXOG and GORASP1, were in regions of positive linkage whilst the remainder were not excluded by linkage analysis. Sanger sequencing was focused on three candidate genes, EXOG, GORASP1 and COL6A5, but no variant segregated with Dupuytren’s disease in additional family members. No likely disease-causing variant was identified in all family members positive for the disease phenotype.

A second cohort consisted of the Busselton study population, a study initiated in the 1960s and following the health outcomes of nearly 5000 people in Busselton WA. Using a survey 48 unrelated individuals were identified as having had surgery for DD, whilst 409 people had evidence of early DD. DNA from the participants of the Busselton study was screened for SNPs using a GWAS chip approach and the data analysed to identify SNPs associated with DD. This study lacked sufficient power to identify statistically significant SNPs associated with the disease. A shortlist of variants was identified using an arbritrary p-value cut-off. However, none of these SNPs were associated with genes in either the familial study or previous research. For the final genetic study DNA from another set of individuals with severe DD were subject to WES. The aim was to identify rare mutations in genes that may be associated with DD and that would promote the more aggressive phenotype in these individuals. Whilst no mutations in identical genes as previous studies were identified there was overlap in gene families and networks that suggests pathways that may be important in DD. Finally, fibroblasts isolated from some Dupuytren patients and control fibroblasts from the wrist were characterized using a modified ‘scar-in-a-jar’ protocol to investigate their collagen production. Interestingly, this model did not identify any differences between disease fibroblasts and control fibroblasts from the same patients. This may suggest that profibrotic signals in Dupuytren disease are external to the fibroblasts rather than autonomous. In addition it strongly suggests a need to develop more complex models to reproduce the disease state in vitro for further studies to understand the molecular basis of Dupuytren’s disease and The complexity of the known genetic susceptibility together with environmental factors, as well as the likely importance of non-coding and epigenetic factors continues to make identification of the genetic changes underpinning Dupuytren’s disease difficult. In addition limited in vitro and animal models for Dupuytren’s disease will continue to hamper therapeutic development and understanding. However, the studies here suggest common pathways may be implicated from the familial and population study approaches. Further work to identify the functional changes that underpin DD will be critical to the development of more effective treatment and prevention of the disease.

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