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Characterization of C. elegans PAT-9 and FRG-1, which are critical for body wall muscle development

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Title: Characterization of C. elegans PAT-9 and FRG-1, which are critical for body wall muscle development
Author(s): Liu, Qian
Director of Research: Jones, Peter L.
Doctoral Committee Chair(s): Chen, Jie
Doctoral Committee Member(s): Jones, Peter L.; Best, Philip M.; Newmark, Phillip A.; Brieher, William M.
Department / Program: Cell & Developmental Biology
Discipline: Cell and Developmental Biology
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: Ph.D.
Genre: Dissertation
Subject(s): Caenorhabditis elegans muscle facioscapulohumeral muscular dystrophy region gene 1 (FSHD FRG-1) microarray
Abstract: Caenorhabditis elegans, a small free-living nematode, has been used to investigate many biological processes including apoptosis, the cell cycle, gene regulation, cell polarity, metabolism, aging, and development. Transgenic C. elegans have been broadly utilized as a human disease model to study mechanisms of pathology for diseases such as obesity, diabetes, cancer, Duchenne’s muscular dystrophy, and several neurodegenerative diseases. In these studies we used C. elegans to further investigate muscle development and as a model for facioscapulohumeral muscular dystrophy (FSHD) pathophysiology. A previous genetic screen in C. elegans investigating early muscle development isolated mutants producing a pat (paralyzed, elongation arrested at two-fold) phenotype. This project focused on identifying and characterizing one of the pat genes, pat-9. Positional cloning and reverse genetics were used to identify T27b1.2 as encoding the pat-9 gene. Characterization of the PAT-9 protein revealed that it is an exclusively nuclear zinc finger protein required for muscle development. This nuclear localization for PAT-9 makes it unique among the pat family of genes. Considering the pat-9 mutant phenotype shows severely disrupted muscle attachment sites despite PAT-9 not localizing to those sites, PAT-9 may function in the regulation of expression for some necessary structural component of the muscle attachment sites. For the FSHD project, a C. elegans homolog of the FSHD candidate gene FRG1 (FSHD region gene 1), ZK1010.3, was identified, cloned, renamed frg-1, and characterized. Surprisingly, both the endogenous and overexpressed FRG-1 was localized to the nucleus and the cytoplasm, contrary to what had been reported in the literature for human FRG1. Interestingly, in adult body wall muscle, FRG-1 associated with the cytoplasmic dense bodies whose primary function in C. elegans is to transfer mechanical force from muscle contraction to the cuticle by attaching the muscle fiber to the muscle cell membrane and the surrounding extracellular matrix (ECM). Thus, dense bodies are functionally similar to the vertebrate Z-disk and contain homologs of many of the same Z-disk proteins. Many other types of muscular dystrophy, such as Duchenne, Becker, certain limb-girdle dystrophies and some rare congenital muscular dystrophies result from mutations affecting vertebrate orthologs of dense body components. To date, our study of FRG-1 in C. elegans renders FRG-1 the only FSHD candidate gene with a direct link to muscle structure. In addition, overexpression of FRG-1 affects its distribution between the nucleus and cytoplasm, and 25% of transgenic animals overexpressing FRG-1 showed disruptions in body wall musculature, including smaller, misaligned, missing and disconnected muscle cells. FRG-1 is highly evolutionarily conserved suggesting human FRG1 may have the similar expression and function. This data strongly supports a role for mis-expressed FRG1 in mediating the disruption of muscle cell membrane integrity and muscle weakness in FSHD patients.
Issue Date: 2010-08-31
URI: http://hdl.handle.net/2142/17011
Rights Information: Copyright 2010 Qian Liu
Date Available in IDEALS: 2010-08-31
2012-09-07
Date Deposited: 2010-08
 

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