Aug 1, 1989

Ultrastructural and molecular analyses of homozygous-viable Drosophila melanogaster muscle mutants indicate there is a complex pattern of myosin heavy-chain isoform distribution

Genes & Development
P T O'DonnellS I Bernstein

Abstract

We describe the ultrastructural and initial molecular characterization of four homozygous-viable, dominant-flightless mutants of Drosophila melanogaster. Genetic mapping indicates that these mutations are inseparable from the known muscle myosin heavy-chain (MHC) allele Mhc1, and each mutation results in a muscle-specific reduction in MHC protein accumulation. The indirect flight muscles (IFMs) of each of these homozygous mutants fail to accumulate MHC, lack thick filaments, and do not display normal cylindrical myofibrils. As opposed to the null phenotype observed in the IFM, normal amounts of MHC accumulate in the leg muscles of three of these mutants, whereas the fourth mutant shows a 45% reduction in leg muscle MHC. The ultrastructure of the tergal depressor of the trochanter muscle TDT, or jump muscle) is normal in one mutant, completely lacks thick filaments in a second mutant, and displays a reduction of thick filaments in two mutants. The thick filament reduction in this latter class of mutants is limited to the four smaller anterior cells of the TDT, indicating that the TDT is a mixed fiber-type muscle. Because all isoforms of muscle MHC are encoded by alternative splicing of transcripts from a single gene, our results...Continue Reading

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Mentioned in this Paper

Establishment and Maintenance of Localization
Exons
Muscle Cells
Skeletal Muscle Structure of Lower Leg
Drosophila
Genome Mapping
Electron Microscopy
Muscle
Actomyosin Adenosinetriphosphatase
Mutant

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