The role of muscleblind-like proteins in myotonic dystrophy

Arya, Sukrat (2014) The role of muscleblind-like proteins in myotonic dystrophy. PhD thesis, University of Nottingham.

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Myotonic dystrophy (DM) is a progressive multisystemic genetic disorder which is inherited as an autosomal dominant trait. There are two subtypes of the disorder, DM type 1 and DM type 2. DM type1 is caused by an expansion of a CTG repeat located in the 3' untranslated region of the DMPK gene on chromosome 19q13.3, whereas DM type 2 is caused by a CCTG expansion in intron 1 of ZNF9 gene located on chromosome 3q. The mutant RNAs containing the expanded CTG/CCTG repeats alters the activity of various alternative splicing factors like Muscleblind-like (MBNL) proteins, which are sequestered in the ribonuclear foci in nucleus by the expanded mutant transcripts resulting in a number of splicing defects observed in DM patients.

In first part of my thesis, I have assessed the nuclear and cytosolic distribution of MBNL proteins in both normal and DM cells. In both DM1 and DM2 cells the amount of nuclear MBNL1 was found to be at least 50% greater than seen in normal cells. In addition to this, I studied the distribution of MBNL1 protein in nuclear and cytosolic fractions of DM cells before and after treatment with compounds chromomycin A3, gemcitabine, IMOX, RO 31-8220 and hypericin which were highlighted in the primary screen. Treatment with the compounds produced a significant reduction in the proportion of nuclear MBNL1 compared to DMSO treated cells in DM fibroblast and myoblasts.

In second part of this thesis I have examined the effect of MBNL1/2 down regulation on both RNA and MBNL1 foci in DM cells. MBNL1 and MBNL2 double knockdown resulted in a 40% increase of nuclear RNA foci than observed in scrambled siRNA treated cells, though a significant reduction was observed in case of MBNL (protein) foci. Also, MBNL 1 and MBNL2 down regulation did not result in the release of mutant transcript from the nucleus to the cytoplasm in KB-Telo MyoD (DM) cells as seen in BpmI restriction polymorphism assay. However, it had a degradative effect on the mutant DMPK transcript.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Brook, J.D.
Subjects: R Medicine > RC Internal medicine
W Medicine and related subjects (NLM Classification) > WE Muscoskeletal system
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Life Sciences
Item ID: 14341
Depositing User: EP, Services
Date Deposited: 24 Oct 2014 09:15
Last Modified: 14 Sep 2016 11:12

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