Electron microscopic and electrophoretic studies of a Drosophila muscle mutant wings-up B.

Mogami, Kaname; Nonomura, Yoshiaki; Hotta, Yoshiki

doi:10.1266/jjg.56.51

Cited by 21 publications

(18 citation statements)

References 17 publications

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“…If so, a mutation that alters the ratio of thick to thin filaments or affects crossbridge formation would also be expected to cause aberrant myofibrillar assembly. As expected, mutations in the genes encoding myosin heavy chain, troponin T and the IFM specific isoform of actin have been shown to result in aberrant myofibrillar assembly in heterozygotes (Mogami et al, 1981;Mahaffey et al, 1985; Chun and Falkenthal, 1988;O'Donnell and Bernstein, 1988;Beall et al, 1989;. Electron microscopy of IFMs from heterozygous troponin T and actin null mutants revealed that these mutations reduced the number of thin filaments by "o50%, whereas heterozygous myosin heavy chain null mutants exhibit an "o50% reduction in the number of thick filaments.…”

Section: Ifm Myofibrillar Assembly Requires Diploid Levels Of Mlc-2 Gmentioning

confidence: 55%

“…Electron microscopy of IFMs from heterozygous troponin T and actin null mutants revealed that these mutations reduced the number of thin filaments by "o50%, whereas heterozygous myosin heavy chain null mutants exhibit an "o50% reduction in the number of thick filaments. The common ultrastructural defect conferred by these myofibrillar protein deficiencies is that the central core of the myofibril appears to assemble normally; however, the arrangement of myofilaments at the periphery of the myofibrils is aberrant due to the altered ratio of thick to thin filaments (Mogami et al, 1981; Chun and Falkenthal, 1988;Beall et al, 1989).…”

Section: Ifm Myofibrillar Assembly Requires Diploid Levels Of Mlc-2 Gmentioning

confidence: 99%

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Myosin light chain-2 mutation affects flight, wing beat frequency, and indirect flight muscle contraction kinetics in Drosophila.

Warmke

Yamakawa

Molloy

et al. 1992

The Journal of Cell Biology

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Abstract. We have used a combination of classical genetic, molecular genetic, histological, biochemical, and biophysical techniques to identify and characterize a null mutation of the myosin light chain-2 (MLC-2) locus of Drosophila melanogaster. Mlc2 e3a is a null mutation of the MLC-2 gene resulting from a nonsense mutation at the tenth codon position. Mlc2 E3s confers dominant flightless behavior that is associated with reduced wing beat frequency. Mlc2 E3a heterozygotes exhibit a 50% reduction of MLC-2 mRNA concentration in adult thoracic musculature, which results in a commensurate reduction of MLC-2 protein in the indirect flight muscles. Indirect flight muscle myofibrils from Mlc2 ~38 heterozygotes are aberrant, exhibiting myofilaments in disarray at the periphery. Calcium-activated Triton X-100-treated single fiber segments exhibit slower contraction kinetics than wild type. Introduction of a transformed copy of the wild type MLC-2 gene rescues the dominant flightless behavior of Mlc2 E3s heterozygotes. Wing beat frequency and single fiber contraction kinetics of a representative rescued line are not significantly different from those of wild type. Together, these results indicate that wild type MLC-2 stoichiometry is required for normal indirect flight muscle assembly and function. Furthermore, these resuits suggest that the reduced wing beat frequency and possibly the flightless behavior conferred by Mlc2 e3s is due in part to slower contraction kinetics of sarcomeric regions devoid or partly deficient in MLC-2.F ORCE production in virtually all types of muscle requires the formation of mechanically strained, elastic cross-bridges between myosin-and actin-containing filaments. These cross-bridges are composed of the globular heads of the myosin heavy chain subunits and their associated light chains (the myosin alkali light chain and the myosin light chain-2 (MLC-2) t, the regulatory light chain). The myosin cross-bridge projects out from the thick (myosin) filament and attaches to an adjacent thin (actin) filament, activating an actomyosin Mg2 § which provides the chemical energy required for muscle contraction (Adelstein and Eisenberg, 1980). The cyclic making and breaking of these cross-bridges, together with a conformational change within the myosin molecule, causes the actin and myosin filaments to slide past each other enabling the muscle to shorten against an external load (Huxley, 1969 Two independent systems regulate the actomyosin ATPase cycle and contraction: a thin filament control system regulated by the troponin-tropomyosin complex, and a thick filament control system modulated by MLC-2 (Lehman and Szent-Gyorgyi, 1975;Sweeney and Stull, 1990, and references therein). The sophisticated molecular and genetic manipulations possible in Drosophila provides a powerful approach with which to investigate the structure-funodon relationships of these regulatory proteins (Peckham et al., 1990;Fyrberg and Beall, 1990). Our efforts have been directed toward defining the role of the MLC-2 protein.Her...

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Section: Ifm Myofibrillar Assembly Requires Diploid Levels Of Mlc-2 Gmentioning

confidence: 55%

Section: Ifm Myofibrillar Assembly Requires Diploid Levels Of Mlc-2 Gmentioning

confidence: 99%

Myosin light chain-2 mutation affects flight, wing beat frequency, and indirect flight muscle contraction kinetics in Drosophila.

Warmke

Yamakawa

Molloy

et al. 1992

The Journal of Cell Biology

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“…A major fraction of these mutations are expected to reside in genes that specify muscle-specific proteins. This expectation is corroborated in the cases of a few genes whose wild-type products have been characterized (1,16,17,23,26,27). A second set of mutations may represent genes expressed in the muscle which also have expression in other tissues.…”

mentioning

confidence: 77%

“…Several mutants with impaired flight display defects in muscle structure or organization (8,18,23,26,27). A major fraction of these mutations are expected to reside in genes that specify muscle-specific proteins.…”

mentioning

confidence: 99%

Molecular isolation and analysis of the erect wing locus in Drosophila melanogaster.

Fleming¹,

DeSimone²,

White³

1989

Mol. Cell. Biol.

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The molecular study of the erect wing (ewg) locus was initiated by isolating DNA in the lA8-lB1 interval of the X chromosome. Previous developmental genetic analyses of the mutant alleles at the ewg locus have demonstrated that the wild-type ewg product is essential during embryogenesis and is required postembryonically at least for the development of indirect ffight muscle. To define the ewg-encoding DNA, chromosomal breakpoints that genetically flank the ewg locus were used. P-element-mediated transformation followed by subsequent rescue of the ewg-lethal alleles has defined a 11.5-kilobase genomic fragment as encoding the ewg locus. Northern blot analysis of transcription from this DNA has revealed a complex pattern of transcription with respect to both size and developmental profile. Tissue distribution of putative ewg transcription was examined by in situ hybridization to 6-to 14-h-old embryonic sections. These sections revealed that the expression of putative ewg messages is limited to the central nervous system-derived structures and not observed within the mesoderm during this developmental stage.In the fruit fly, Drosophila melanogaster, a large array of mutations have been discovered through phenotypic wing position abnormalities or flight abnormalities (13). Several mutants with impaired flight display defects in muscle structure or organization (8,18,23,26,27). A major fraction of these mutations are expected to reside in genes that specify muscle-specific proteins. This expectation is corroborated in the cases of a few genes whose wild-type products have been characterized (1,16,17,23,26,27). A second set of mutations may represent genes expressed in the muscle which also have expression in other tissues. Finally, a third class of mutations may identify an interesting group of genes whose expression lies outside of the mesodermal tissue but is essential to the proper development or function of muscle. The involvement of a functional nervous system in the proper development and maintenance of muscle has been recognized in vertebrate and invertebrate systems (3, 12, 14, 19, 25, 30). The recent work of Lawrence and Johnston (20) has revealed neural influence during the differentiation and development of insect musculature.We have been studying the erect wing (ewg) locus in Drosophila melanogaster because of the interesting phenotypes associated with mutations at this locus (11; R. J. Fleming, Ph.D. thesis, Brandeis University, Waltham, Mass., 1987 blastoderm, the area from which the mesoderm and the nervous system are derived (11). Thus, both the phenotypic defects associated with mutant ewg alleles and the genetic mosaic analyses are consistent with the suggestion that the ewg gene product may be required in the musculature or the nervous system.To directly address the question of tissue specificity of expression and function of the ewg gene, we have initiated a molecular characterization of the ewg-encoding DNA. The proximal to distal order for known genes in the 1A8-1B1-2 interval of the X chrom...

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“…One of the TnT mutations results in abnormal splicing: the Int15 G → A mutation inactivates a 5 Ј splice donor site leading to either skipping of exon 15 or activation of a cryptic splice site; both aberrant cDNAs encode a truncated TnT peptide lacking the conserved carboxyl terminus. Based on analogy to a similar mutation previously found in Drosophila melanogaster which encodes no stable TnT peptide (14), the Int15 G → A mutation was predicted to result in a functional null (4). If this were the case, then the pathogenesis would likely be via a different mechanism than that of the myosin mutations, with important consequences for further investigation and potential intervention in this condition.…”

Section: Introductionmentioning

confidence: 90%

Expression and functional assessment of a truncated cardiac troponin T that causes hypertrophic cardiomyopathy. Evidence for a dominant negative action.

Watkins

Seidman²,

Seidman³

et al. 1996

J. Clin. Invest.

128

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Mutations in the ␤ -myosin heavy chain gene are believed to cause hypertrophic cardiomyopathy (HCM) by acting as dominant negative alleles. In contrast, a truncated cardiac troponin T (TnT) that causes HCM implies that altered stoichiometry of contractile proteins may also cause cardiac hypertrophy. Wild-type and HCM-mutant (truncated) TnT were studied in a novel quail myotube expression system. Unexpectedly, antibody staining demonstrated incorporation of both forms of human cardiac TnT into the sarcomeres of quail myotubes. Functional studies of wild type and mutant transfected myotubes of normal appearance revealed that calcium-activated force of contraction was normal upon incorporation of wild type TnT, but greatly diminished for the mutant TnT. These findings indicate that HCM-causing mutations in TnT and ␤ -myosin heavy chain share abnormalities in common, acting as dominant negative alleles that impair contractile performance. This diminished force output is the likely stimulus for hypertrophy in the human heart. ( J. Clin. Invest. 1996. 98:2456-2461.)

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Electron microscopic and electrophoretic studies of a Drosophila muscle mutant wings-up B.

Cited by 21 publications

References 17 publications

Myosin light chain-2 mutation affects flight, wing beat frequency, and indirect flight muscle contraction kinetics in Drosophila.

Myosin light chain-2 mutation affects flight, wing beat frequency, and indirect flight muscle contraction kinetics in Drosophila.

Molecular isolation and analysis of the erect wing locus in Drosophila melanogaster.

Expression and functional assessment of a truncated cardiac troponin T that causes hypertrophic cardiomyopathy. Evidence for a dominant negative action.

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