The Drosophila gamma-tubulin small complex subunit Dgrip84 is required for structural and functional integrity of the spindle apparatus.
Gamma-tubulin, a protein critical for microtubule assembly, functions within multiprotein complexes. However, little is known about the respective role of gamma-tubulin partners in metazoans. For the first time in a multicellular organism, we have investigated the function of Dgrip84, the Drosophila orthologue of the Saccharomyces cerevisiae gamma-tubulin-associated protein Spc97p. Mutant analysis shows that Dgrip84 is essential for viability. Its depletion promotes a moderate increase in the mitotic index, correlated with the appearance of monopolar or unpolarized spindles, impairment of centrosome maturation, and increase of polyploid nuclei. This in vivo study is strengthened by an RNA interference approach in cultured S2 cells. Electron microscopy analysis suggests that monopolar spindles might result from a failure of centrosome separation and an unusual microtubule assembly pathway via centriolar triplets. Moreover, we point to an involvement of Dgrip84 in the spindle checkpoint regulation and in the maintenance of interphase microtubule dynamics. Dgrip84 also seems essential for male meiosis, ensuring spindle bipolarity and correct completion of cytokinesis. These data sustain that Dgrip84 is required in some aspects of microtubule dynamics and organization both in interphase and mitosis. The nature of a minimal gamma-tubulin complex necessary for proper microtubule organization in the metazoans is discussed.
Colombié
Nathalie
N
Centre de Recherche en Pharmacologie-Santé, Unité Mixte de Recherche 2587, Centre National de la Recherche Scientifique-Pierre Fabre, Institut de Sciences et Technologies du Médicament de Toulouse, 31400 Toulouse, France.
Vérollet
Christel
C
Sampaio
Paula
P
Moisand
André
A
Sunkel
Claudio
C
Bourbon
Henri-Marc
HM
Wright
Michel
M
Raynaud-Messina
Brigitte
B
D000818:Animals; D002460:Cell Line; D002503:Centromere / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008854:Microscopy, Electron; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000235:genetics / Q000378:metabolism; D008938:Mitosis; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D011485:Protein Binding; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D013091:Spermatogenesis; D008941:Spindle Apparatus / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D018411:Spodoptera; D014404:Tubulin / Q000737:chemistry* / Q000378:metabolism*
D029721:Drosophila Proteins; C509152:Grip84 protein, Drosophila; D008869:Microtubule-Associated Proteins; D021122:Protein Subunits; D014404:Tubulin