title: Organelle positioning in muscles requires cooperation between two KASH proteins and microtubules.
abstract: Striated muscle fibers are characterized by their tightly organized cytoplasm. Here, we show that the Drosophila melanogaster KASH proteins Klarsicht (Klar) and MSP-300 cooperate in promoting even myonuclear spacing by mediating a tight link between a newly discovered MSP-300 nuclear ring and a polarized network of astral microtubules (aMTs). In either klar or msp-300(ΔKASH), or in klar and msp-300 double heterozygous mutants, the MSP-300 nuclear ring and the aMTs retracted from the nuclear envelope, abrogating this even nuclear spacing. Anchoring of the myonuclei to the core acto-myosin fibrillar compartment was mediated exclusively by MSP-300. This protein was also essential for promoting even distribution of the mitochondria and ER within the muscle fiber. Larval locomotion is impaired in both msp-300 and klar mutants, and the klar mutants were rescued by muscle-specific expression of Klar. Thus, our results describe a novel mechanism of nuclear spacing in striated muscles controlled by the cooperative activity of MSP-300, Klar, and astral MTs, and demonstrate its physiological significance.
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Hadas
authors.initials: H
authors.lastname: Elhanany-Tamir
authors.forename: Yanxun V
authors.initials: YV
authors.lastname: Yu
authors.forename: Miri
authors.initials: M
authors.lastname: Shnayder
authors.forename: Ankit
authors.initials: A
authors.lastname: Jain
authors.forename: Michael
authors.initials: M
authors.lastname: Welte
authors.forename: Talila
authors.initials: T
authors.lastname: Volk
mesh_terms: D000205:Actomyosin / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D064211:Connectin; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D008124:Locomotion / Q000235:genetics / Q000502:physiology; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D008870:Microtubules / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000378:metabolism* / Q000502:physiology*; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009210:Myofibrils / Q000235:genetics / Q000378:metabolism*; D009685:Nuclear Envelope / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D015388:Organelles / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*
chemical_list: D064211:Connectin; D029721:Drosophila Proteins; D026901:Membrane Transport Proteins; D008840:Microfilament Proteins; C079806:Msp300 protein, Drosophila; D009124:Muscle Proteins; C401521:klar protein, Drosophila; C577347:sls protein, Drosophila; D000205:Actomyosin