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Phenotypic analysis of misato function reveals roles of noncentrosomal microtubules in Drosophila spindle formation

Violaine Mottier-Pavie1, Giovanni Cenci, Fiammetta Vernì

  • 1Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Sapienza Università di Roma, Ple. A. Moro 5, 00185 Roma, Italy.

Journal of Cell Science
|February 3, 2011
PubMed

Insights

Kinetochore-driven microtubule (MT) growth is essential for proper spindle assembly in Drosophila. Mutations in the misato (mst) gene disrupt this pathway, leading to monopolar spindles and larval death.

Area of Science:

  • Cell Biology
  • Genetics
  • Developmental Biology

Background:

  • Mitotic spindle assembly involves centrosome- and chromosome-based microtubule (MT) nucleation pathways.
  • The precise roles of these pathways, especially kinetochore-driven MT growth, remain unclear.
  • Drosophila mutants lacking centrosomes can form viable spindles, suggesting alternative mechanisms.

Purpose of the Study:

  • To investigate the role of the Drosophila misato (mst) gene in mitotic spindle assembly.
  • To define the contribution of kinetochore-driven MT growth to spindle bipolarity.
  • To understand the consequences of impaired kinetochore MT nucleation.

Main Methods:

  • Genetic analysis of Drosophila misato (mst) and Sas-4 mutants.
  • Microtubule regrowth experiments after cold shock.
  • Analysis of mitotic spindle morphology in larval brain cells.

Main Results:

  • mst mutations inhibit kinetochore-driven MT growth, causing monopolar spindles and larval lethality.
  • In mst mutants, initial aster separation fails to be maintained, indicating k-fiber importance.
  • Double mutants lacking both centrosomes and mst function form monopolar spindles, while Sas-4 mutants form bipolar spindles from chromosome-driven MTs.

Conclusions:

  • Kinetochore-driven MT formation is crucial for establishing and maintaining spindle bipolarity in Drosophila somatic cells.
  • The misato gene product is essential for kinetochore MT nucleation.
  • Spindle assembly relies on the coordinated function of both centrosome- and kinetochore-based pathways.

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