[PDF] Molecular Genetic Analysis Of Drosophila Melanogaster Paramyosin In Muscle Development Structure And Function eBook

Author : Hongjun Liu
Publisher :
Page : 294 pages
File Size : 12,43 MB
Release : 2003
Category : Drosophila melanogaster
ISBN :

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Paramyosin is a major structural component of invertebrate muscles. It forms thick filament cores with other proteins. The motor protein myosin assembles on the surface of the core to form functional thick filaments. To investigate the roles of paramyosin in thick filament assembly as well as muscle contraction, I functionally knocked out the Drosophila melanogaster paramyosin gene by mobilizing a P element localized in the promoter region. I found that homozygous paramyosin mutants die at the embryo stage. Using electron microscopy and confocal microscopy, I analyzed the phenotypic defects of a functional null allele prm1. I observed that, in the absence of paramyosin, thick filaments of embryo body wall muscles are abnormal and the striated pattern of myobibrils is disrupted. These results indicate that paramyosin is essential for thick filament assembly and myofibril formation. Surprisingly, the muscle pattern of paramyosin mutant embryos is also abnormal. Mutation of paramyosin causes random losses of muscle fibers. Using a marker for founder myoblasts and the DMEF2 antibody which recognizes all myoblasts, I proved that the muscle fiber loss is not due to defects in myoblast differentiation. Rather, it is caused by abnomal myoblast fusion. Using a paramyosin specific antibody, I revealed that paramyosin functions as a cytoplasmic protein before myofibril formation and is important for myoblast fusion. I further investigated the function of paramyosin phosphorylation in the NH2-terminal non-helical domain. I made transgenic flies in which 1, 3, or 4 phosphorylatable serine residues in this domain are substituted with alanines. I observed that mutations of paramyosin at these residues do not affect the ultrastructure of myofibrils. However, mutant flies with substitution at some specific sites are flight impaired. Mechanical studies of indirect flight muscle fibers revealed that the flight impairment is caused by reduced fiber stiffness and power output. These results indicate that paramyosin phosphorylation in the NH2-terminal domain is important for muscle contraction.

Author :
Publisher :
Page : 256 pages
File Size : 23,2 MB
Release : 2003
Category : Drosophila melanogaster
ISBN :

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Paramyosin is a major structural component of invertebrate muscles. It forms thick filament cores with other proteins. The motor protein myosin assembles on the surface of the core to form functional thick filaments. To investigate the roles of paramyosin in thick filament assembly as well as muscle contraction, I functionally knocked out the Drosophila melanogaster paramyosin gene by mobilizing a P element localized in the promoter region. I found that homozygous paramyosin mutants die at the embryo stage. Using electron microscopy and confocal microscopy, I analyzed the phenotypic defects of a functional null allele prm1. I observed that, in the absence of paramyosin, thick filaments of embryo body wall muscles are abnormal and the striated pattern of myobibrils is disrupted. These results indicate that paramyosin is essential for thick filament assembly and myofibril formation. Surprisingly, the muscle pattern of paramyosin mutant embryos is also abnormal. Mutation of paramyosin causes random losses of muscle fibers. Using a marker for founder myoblasts and the DMEF2 antibody which recognizes all myoblasts, I proved that the muscle fiber loss is not due to defects in myoblast differentiation. Rather, it is caused by abnomal myoblast fusion. Using a paramyosin specific antibody, I revealed that paramyosin functions as a cytoplasmic protein before myofibril formation and is important for myoblast fusion. I further investigated the function of paramyosin phosphorylation in the NH2-terminal non-helical domain. I made transgenic flies in which 1, 3, or 4 phosphorylatable serine residues in this domain are substituted with alanines. I observed that mutations of paramyosin at these residues do not affect the ultrastructure of myofibrils. However, mutant flies with substitution at some specific sites are flight impaired. Mechanical studies of indirect flight muscle fibers revealed that the flight impairment is caused by reduced fiber stiffness and power output. These results indicate that paramyosin phosphorylation in the NH2-terminal domain is important for muscle contraction.

Author : Michelle Mardahl-Dumesnil
Publisher :
Page : 428 pages
File Size : 43,80 MB
Release : 1998
Category : Drosophila melanogaster
ISBN :

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Manipulation of muscle genes to cause their under-, over- and mis-expression and subsequent assessment of resultant phenotypes offers a comprehensive approach to understand muscle assembly, development and function. These techniques are readily applied to the fruit fly, Drosophila melanogaster, because of the relative ease of mutant isolation and germ-line transformation. The consequences of altered muscle gene expression on muscle function and ultrastructure can be well characterized in this genetic system. This dissertation describes experiments to examine the roles of two thick filament proteins and a metabolic enzyme on Drosophila muscle structure and function. In the first chapter, I have determined the genetic lesion for the Mhc2 mutant and performed detailed ultrastructural analysis of the indirect flight muscle (IFM) of mutant and transgenic lines. This investigation reveals the negative effects of over-expression and under-expression of the Mhc gene on muscle function and structure. In Chapter Two, I characterize an enhancer detection line that exhibits strong IFM specific reporter gene activity. The P element of the enhancer detection line lies downstream of the enolase gene. Two interesting complementation groups result when the P element is used to mutagenize this locus. One complementation group is the first identification of a Drosophila enolase mutant, and the other is an unknown mutation that affects flight ability presumably by disrupting mitochondrial function in the IFM. In Chapter Three, I identify both standard (PM) and mini-paramyosin (mPM) mutants. Although thick filaments are present in embryonic body-wall muscle that is lacking PM, the sarcomere is unordered, indicating that PM is needed for its normal structure and function. Low levels of mPM significantly impair flight ability and viability. In addition, more thick filaments incorporate into IFM myofibrils of the mPM mutant than those of wild-type. Over-expression of either PM or mPM affects IFM structure and function. It also appears that equivalent stoichiometric levels of mPM and PM are important for correct sarcomeric structure in the IFM. From these studies, we determine that both PM and mPM confer specific structural qualities to the thick filament and myofibril morphology.

Author : Helen Sink
Publisher : Springer Science & Business Media
Page : 214 pages
File Size : 17,31 MB
Release : 2007-02-26
Category : Science
ISBN : 0387329633

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The different aspects of muscle development are considered from cellular, molecular and genetic viewpoints, and the text is supported by black/white and color illustrations. The book will appeal to those studying muscle development and muscle biology in any organism.