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mini spindles: A gene encoding a conserved microtubule-associated protein required for the integrity of the mitotic spindle in Drosophila.

Cullen CF, Deák P, Glover DM, Ohkura H - J. Cell Biol. (1999)

Bottom Line: Mutation in msps disrupts the structural integrity of the mitotic spindle, resulting in the formation of one or more small additional spindles in diploid cells.The msps gene encodes a 227-kD protein with high similarity to the vertebrate microtubule-associated proteins (MAPs), human TOGp and Xenopus XMAP215, and with limited similarity to the Dis1 and STU2 proteins from fission yeast and budding yeast.In the embryonic division cycles, Msps protein localizes to centrosomal regions at all mitotic stages, and spreads over the spindles during metaphase and anaphase.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cell and Molecular Biology, The University of Edinburgh, Edinburgh EH9 3JR, United Kingdom.

ABSTRACT
We describe a new Drosophila gene, mini spindles (msps) identified in a cytological screen for mitotic mutant. Mutation in msps disrupts the structural integrity of the mitotic spindle, resulting in the formation of one or more small additional spindles in diploid cells. Nucleation of microtubules from centrosomes, metaphase alignment of chromosomes, or the focusing of spindle poles appears much less affected. The msps gene encodes a 227-kD protein with high similarity to the vertebrate microtubule-associated proteins (MAPs), human TOGp and Xenopus XMAP215, and with limited similarity to the Dis1 and STU2 proteins from fission yeast and budding yeast. Consistent with their sequence similarity, Msps protein also associates with microtubules in vitro. In the embryonic division cycles, Msps protein localizes to centrosomal regions at all mitotic stages, and spreads over the spindles during metaphase and anaphase. The absence of centrosomal staining in interphase of the cellularized embryos suggests that the interactions between Msps protein and microtubules or centrosomes may be regulated during the cell cycle.

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Structural integrity of mitotic spindle is disrupted in the mspsP mutant. Whole mount preparations of larval central nervous system were prepared from mspsP and stained to reveal tubulin (green), DNA (red), and a centrosomal antigen, CP190 (blue). The focal planes shown display the overall spindle structure and CP190 staining for each mitotic figure. (a) Category I. Apparently normal bipolar spindle with CP190 at both poles. (b) Category II. One bipolar spindle and one smaller bipolar spindle (arrowhead). CP190 is found at both poles of larger spindle and is missing from one pole of the smaller one. (c) Category II. Two bipolar spindles with one shared pole. CP190 is found at both poles of one spindle, while it is absent from the unshared pole of the other spindle (arrowhead). (d) Category II. At least three chromosomes are associated with each of small bipolar spindles. One spindle has CP190 at both poles, another has the protein at one pole, and the other shows no CP190 at the poles. (e) Category IV. One bipolar spindle and a monopolar spindle. The bipolar spindle has CP190 at both poles. (f) Category III. Short disorganized microtubule bundles associated with a chromosome mass. No discrete CP190 staining is seen. (g) Frequencies of each category of spindle structure observed. Bar, 5 μm.
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Figure 2: Structural integrity of mitotic spindle is disrupted in the mspsP mutant. Whole mount preparations of larval central nervous system were prepared from mspsP and stained to reveal tubulin (green), DNA (red), and a centrosomal antigen, CP190 (blue). The focal planes shown display the overall spindle structure and CP190 staining for each mitotic figure. (a) Category I. Apparently normal bipolar spindle with CP190 at both poles. (b) Category II. One bipolar spindle and one smaller bipolar spindle (arrowhead). CP190 is found at both poles of larger spindle and is missing from one pole of the smaller one. (c) Category II. Two bipolar spindles with one shared pole. CP190 is found at both poles of one spindle, while it is absent from the unshared pole of the other spindle (arrowhead). (d) Category II. At least three chromosomes are associated with each of small bipolar spindles. One spindle has CP190 at both poles, another has the protein at one pole, and the other shows no CP190 at the poles. (e) Category IV. One bipolar spindle and a monopolar spindle. The bipolar spindle has CP190 at both poles. (f) Category III. Short disorganized microtubule bundles associated with a chromosome mass. No discrete CP190 staining is seen. (g) Frequencies of each category of spindle structure observed. Bar, 5 μm.

Mentions: We found that only 28% of mitotic cells formed an apparently normal bipolar spindle (Fig. 2 a) while the rest showed abnormal structures (Fig. 2 g). The most common abnormalities (36% of total mitotic cells) are cells containing more than one bipolar spindle forms (Fig. 2, b–d). As shown in Fig. 2 b, most chromosomes are aligned at the metaphase plate and associated with a bipolar spindle, but a few of them have become separated from other chromosomes and associate with an additional smaller bipolar spindle. The two bipolar spindles typically share one of the poles. The major bipolar spindle usually has CP190 staining at both poles, whereas the unshared pole of the other spindle typically has no CP190 staining. The poles of both bipolar spindles are focused. In some cases, chromosomes appeared still to be aligned on a common metaphase plate even though the spindle had bifurcated and the metaphase plate appears to be kinked (Fig. 2 c). In other cases, a large bipolar spindle is no longer observed, but instead there are multiple small bipolar spindles associated with individual chromosomes (Fig. 2 d).


mini spindles: A gene encoding a conserved microtubule-associated protein required for the integrity of the mitotic spindle in Drosophila.

Cullen CF, Deák P, Glover DM, Ohkura H - J. Cell Biol. (1999)

Structural integrity of mitotic spindle is disrupted in the mspsP mutant. Whole mount preparations of larval central nervous system were prepared from mspsP and stained to reveal tubulin (green), DNA (red), and a centrosomal antigen, CP190 (blue). The focal planes shown display the overall spindle structure and CP190 staining for each mitotic figure. (a) Category I. Apparently normal bipolar spindle with CP190 at both poles. (b) Category II. One bipolar spindle and one smaller bipolar spindle (arrowhead). CP190 is found at both poles of larger spindle and is missing from one pole of the smaller one. (c) Category II. Two bipolar spindles with one shared pole. CP190 is found at both poles of one spindle, while it is absent from the unshared pole of the other spindle (arrowhead). (d) Category II. At least three chromosomes are associated with each of small bipolar spindles. One spindle has CP190 at both poles, another has the protein at one pole, and the other shows no CP190 at the poles. (e) Category IV. One bipolar spindle and a monopolar spindle. The bipolar spindle has CP190 at both poles. (f) Category III. Short disorganized microtubule bundles associated with a chromosome mass. No discrete CP190 staining is seen. (g) Frequencies of each category of spindle structure observed. Bar, 5 μm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2169485&req=5

Figure 2: Structural integrity of mitotic spindle is disrupted in the mspsP mutant. Whole mount preparations of larval central nervous system were prepared from mspsP and stained to reveal tubulin (green), DNA (red), and a centrosomal antigen, CP190 (blue). The focal planes shown display the overall spindle structure and CP190 staining for each mitotic figure. (a) Category I. Apparently normal bipolar spindle with CP190 at both poles. (b) Category II. One bipolar spindle and one smaller bipolar spindle (arrowhead). CP190 is found at both poles of larger spindle and is missing from one pole of the smaller one. (c) Category II. Two bipolar spindles with one shared pole. CP190 is found at both poles of one spindle, while it is absent from the unshared pole of the other spindle (arrowhead). (d) Category II. At least three chromosomes are associated with each of small bipolar spindles. One spindle has CP190 at both poles, another has the protein at one pole, and the other shows no CP190 at the poles. (e) Category IV. One bipolar spindle and a monopolar spindle. The bipolar spindle has CP190 at both poles. (f) Category III. Short disorganized microtubule bundles associated with a chromosome mass. No discrete CP190 staining is seen. (g) Frequencies of each category of spindle structure observed. Bar, 5 μm.
Mentions: We found that only 28% of mitotic cells formed an apparently normal bipolar spindle (Fig. 2 a) while the rest showed abnormal structures (Fig. 2 g). The most common abnormalities (36% of total mitotic cells) are cells containing more than one bipolar spindle forms (Fig. 2, b–d). As shown in Fig. 2 b, most chromosomes are aligned at the metaphase plate and associated with a bipolar spindle, but a few of them have become separated from other chromosomes and associate with an additional smaller bipolar spindle. The two bipolar spindles typically share one of the poles. The major bipolar spindle usually has CP190 staining at both poles, whereas the unshared pole of the other spindle typically has no CP190 staining. The poles of both bipolar spindles are focused. In some cases, chromosomes appeared still to be aligned on a common metaphase plate even though the spindle had bifurcated and the metaphase plate appears to be kinked (Fig. 2 c). In other cases, a large bipolar spindle is no longer observed, but instead there are multiple small bipolar spindles associated with individual chromosomes (Fig. 2 d).

Bottom Line: Mutation in msps disrupts the structural integrity of the mitotic spindle, resulting in the formation of one or more small additional spindles in diploid cells.The msps gene encodes a 227-kD protein with high similarity to the vertebrate microtubule-associated proteins (MAPs), human TOGp and Xenopus XMAP215, and with limited similarity to the Dis1 and STU2 proteins from fission yeast and budding yeast.In the embryonic division cycles, Msps protein localizes to centrosomal regions at all mitotic stages, and spreads over the spindles during metaphase and anaphase.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cell and Molecular Biology, The University of Edinburgh, Edinburgh EH9 3JR, United Kingdom.

ABSTRACT
We describe a new Drosophila gene, mini spindles (msps) identified in a cytological screen for mitotic mutant. Mutation in msps disrupts the structural integrity of the mitotic spindle, resulting in the formation of one or more small additional spindles in diploid cells. Nucleation of microtubules from centrosomes, metaphase alignment of chromosomes, or the focusing of spindle poles appears much less affected. The msps gene encodes a 227-kD protein with high similarity to the vertebrate microtubule-associated proteins (MAPs), human TOGp and Xenopus XMAP215, and with limited similarity to the Dis1 and STU2 proteins from fission yeast and budding yeast. Consistent with their sequence similarity, Msps protein also associates with microtubules in vitro. In the embryonic division cycles, Msps protein localizes to centrosomal regions at all mitotic stages, and spreads over the spindles during metaphase and anaphase. The absence of centrosomal staining in interphase of the cellularized embryos suggests that the interactions between Msps protein and microtubules or centrosomes may be regulated during the cell cycle.

Show MeSH
Related in: MedlinePlus