Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Biochemistry

Supervisor

Dr. David O'Gorman

Abstract

Dupuytren’s Disease (DD) is a benign and heritable connective tissue fibrosis that affects the palmar fascia and typically results in permanent finger contracture(s). Similar to other fibroses, DD is characterized by increased fibroblast proliferation, myofibroblast differentiation and excess collagen deposition. Currently, there are no truly effective treatment options for connective tissue fibroses.

Increased levels of β-catenin, an intracellular trans-regulator of gene transcription, have been previously reported in DD. Genes that are associated with, and therefore potentially transcriptionally regulated by, β-catenin during DD development were identified in this thesis. One of these gene targets, IGFBP6, was shown to consistently be associated with β-catenin in fibroblasts derived from phenotypically normal palmar fascia (PF cells) but not fibroblasts derived from diseased tissues (DD cells). β-catenin association with the IGFBP6 promoter in these cells was directly correlated with IGFBP6 expression levels and with the secretion of its protein product, Insulin-like Growth Factor Binding Protein-6 (IGFBP-6). In addition, 1 438 unique genes were shown to associate with β-catenin in DD cells but not PF cells derived from the same patients.

The functional consequences of IGFBP-6 repression, and the increased availability of its primary ligand, IGF-II were also elucidated. Exogenous addition of IGFBP-6 inhibited the proliferation of DD and control fibroblasts, and attenuated IGF-II induced contraction of DD cells. IGF-II stimulated the proliferation of normal fibroblasts but not fibroblasts derived from patients with DD. The gene encoding IGF-II, IGF2, was found to be up regulated in DD cells, and potential mechanisms facilitating IGF2 overexpression were investigated. Loss of imprinted expression of IGF2 was detected in a subset of patients and a corresponding loss of H19 expression, a non-coding RNA that is reciprocally expressed relative to IGF2, was observed. Aberrant IGF2 promoter usage was also identified in a subset of DD and PF cells. In combination, these disease-associated changes may explain the increased IGF2 expression in DD. Identification of novel genes targets of β-catenin and the factors that regulate the expression of IGFBP6 or IGF2 during the development of this debilitating fibrosis may allow us to identify novel therapeutic targets.

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