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Orbit, a Novel Microtubule-Associated Protein Essential for Mitosis in Drosophila melanogaster

Inoue, Yoshihiro H. and do Carmo Avides, Maria and Shiraki, Michina and Deak, Peter and Yamaguchi, Masamitsu and Nishimoto, Yoshio and Matsukage, Akio and Glover, David M. (2000) Orbit, a Novel Microtubule-Associated Protein Essential for Mitosis in Drosophila melanogaster. Journal of Cell Biology, 149 (1). pp. 153-166. ISSN 0021-9525. PMCID PMC2175100. doi:10.1083/jcb.149.1.153.

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We describe a Drosophila gene, orbit, that encodes a conserved 165-kD microtubule-associated protein (MAP) with GTP binding motifs. Hypomorphic mutations in orbit lead to a maternal effect resulting in branched and bent mitotic spindles in the syncytial embryo. In the larval central nervous system, such mutants have an elevated mitotic index with some mitotic cells showing an increase in ploidy. Amorphic alleles show late lethality and greater frequencies of hyperploid mitotic cells. The presence of cells in the hypomorphic mutant in which the chromosomes can be arranged, either in a circular metaphase or an anaphase-like configuration on monopolar spindles, suggests that polyploidy arises through spindle and chromosome segregation defects rather than defects in cytokinesis. A role for the Orbit protein in regulating microtubule behavior in mitosis is suggested by its association with microtubules throughout the spindle at all mitotic stages, by its copurification with microtubules from embryonic extracts, and by the finding that the Orbit protein directly binds to MAP-free microtubules in a GTP-dependent manner.

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Glover, David M.0000-0003-0956-0103
Additional Information:© 2000 The Rockefeller University Press. After the Initial Publication Period, RUP will grant to the public the non-exclusive right to copy, distribute, or display the Article under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 International license, as described at, or updates thereof. Received: 24 August 1999. Revised: 28 February 2000. Accepted: 29 February 2000. We would like to thank Fumiko Hirose for supplying staged total RNA and Maria Deak for technical assistance at initial stages of the project. This work was supported by a program grant from the Cancer Research Campaign (CRC), and by a Grant-in-Aid for Scientific Research (A) on Priority Areas from the Ministry of Education, Science and Culture of Japan. Project grant support was provided by the Medical Research Council and the Association for International Cancer Research. The CRC Cell Cycle Genetics Group is also a member of a TMR Network of the EU.
Funding AgencyGrant Number
Cancer Research CampaignUNSPECIFIED
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Medical Research Council (UK)UNSPECIFIED
Association for International Cancer ResearchUNSPECIFIED
Subject Keywords:mitosis • microtubule-associated protein • Drosophila melanogaster • mitotic spindle • centrosome
Issue or Number:1
PubMed Central ID:PMC2175100
Record Number:CaltechAUTHORS:20201007-123359484
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Official Citation:Yoshihiro H. Inoue, Maria do Carmo Avides, Michina Shiraki, Peter Deak, Masamitsu Yamaguchi, Yoshio Nishimoto, Akio Matsukage, David M. Glover; Orbit, a Novel Microtubule-Associated Protein Essential for Mitosis in Drosophila melanogaster. J Cell Biol 3 April 2000; 149 (1): 153–166. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105887
Deposited By: George Porter
Deposited On:07 Oct 2020 22:46
Last Modified:16 Nov 2021 18:47

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