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Analysis of cell signalling in dystrophin-deficient myoblasts

Yazid, Muhammad Da’In Bin (2017)
Ph.D. thesis, University of Birmingham.

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Abstract

An absence of dystrophin in muscle has a massive impact throughout muscle development, and Duchene Muscular Dystrophy (DMD) is one of the consequences. The disruption of the dystrophin-glycoprotein complex (DGC) is caused by a mutation in the dmd gene, which effects muscle integrity, resulting in progressive muscle degeneration and weakness. In this study, dfd13 (dystrophin-deficient) and C2C12 (non-dystrophic) myoblasts were cultured in low mitogen conditions for 10 days to induce differentiation; however, dfdl3 myoblasts did not achieve terminal differentiation. It has been suggested that Pax7 may play a major role during myogenesis, therefore its expression pattern and transport protein were examined for any impairments. It was established that Pax7 localises in the cytoplasm of dystrophindeficient myoblasts and high expression is retained during differentiation. Colocalisation of Pax7 with subcellular markers analysis indicated that Pax7 is synthesised during the proliferative state. Pax7 was shown to possess a nuclear location signal and KPNA2 was suggested as escort protein for Pax7 translocation into the nucleus. The PTEN-PI3K/Akt signalling pathway was investigated and protein synthesis regulation and Fox03 was found to be impaired. Autophagy related genes were found to be highly expressed; however, LC3 lipidation and autophagy flux showed a reduction upon differentiation, indicating defective autophagy. The contribution of PTEN overexpression was assessed in relation to endoplasmic reticulum (ER) stress and activation of the unfolding protein response (UPR). It was established that a reduction in ER stress and changes to UPR activation lead to apoptosis. Finally, minidystrophintransfection of both types of myoblasts was utilised to examine the effect, especially in dystrophin-deficient myoblasts. Minidystrophin improved protein synthesis activation and increased autophagy (increased LC3 lipidation), suggesting that minidystrophin ameliorates dystrophic events at the level of autophagosome formation. To conclude, destabilisation of the plasma membrane owing to a dystrophin mutation causes cell signalling alterations which minidystrophin restoration can partly improve.

Type of Work:Ph.D. thesis.
Supervisor(s):Hotchin, Neil and Smith, Janet
School/Faculty:Colleges (2008 onwards) > College of Life & Environmental Sciences
Department:School of Biosciences
Subjects:QH301 Biology
QH426 Genetics
Institution:University of Birmingham
ID Code:7342
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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