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The mesh is a network of microtubule connectors that stabilizes individual kinetochore fibers of the mitotic spindle.

Nixon FM, Gutiérrez-Caballero C, Hood FE, Booth DG, Prior IA, Royle SJ - Elife (2015)

Bottom Line: Molecular manipulation of the mesh by overexpression of TACC3 causes disorganization of the K-fiber MTs.We propose that the mesh stabilizes K-fibers by pulling MTs together and thereby maintaining the integrity of the fiber.Our work thus identifies the K-fiber meshwork of linked multipolar connectors as a key integrator and determinant of K-fiber structure and function.

View Article: PubMed Central - PubMed

Affiliation: Division of Biomedical Cell Biology, Warwick Medical School, Coventry, United Kingdom.

ABSTRACT
Kinetochore fibers (K-fibers) of the mitotic spindle are force-generating units that power chromosome movement during mitosis. K-fibers are composed of many microtubules that are held together throughout their length. Here, we show, using 3D electron microscopy, that K-fiber microtubules (MTs) are connected by a network of MT connectors. We term this network 'the mesh'. The K-fiber mesh is made of linked multipolar connectors. Each connector has up to four struts, so that a single connector can link up to four MTs. Molecular manipulation of the mesh by overexpression of TACC3 causes disorganization of the K-fiber MTs. Optimal stabilization of K-fibers by the mesh is required for normal progression through mitosis. We propose that the mesh stabilizes K-fibers by pulling MTs together and thereby maintaining the integrity of the fiber. Our work thus identifies the K-fiber meshwork of linked multipolar connectors as a key integrator and determinant of K-fiber structure and function.

No MeSH data available.


Related in: MedlinePlus

The mesh is associated with K-fiber MTs.(A) 3D rendering of ‘non-mesh’ (brown) in a tomogram of a single K-fiber. Single orthoslice (i), with added rendering (MTs, green; mesh, yellow) (ii) and model alone (iii), is shown. Rendering the mesh involves segmenting density that is attached to the MTs. Here, density to the upper right of the K-fiber was rendered, although it was not touching MTs. The result is a particulate 3D structure that is dissimilar to the K-fiber mesh. (B) Translation of MT map from the tomogram in A, to the upper right corner. Mesh detection was performed as described in ‘Materials and methods’. Single orthoslice view (i), with added rendering (MTs, green; mesh, yellow) (ii). Zoomed views of two MTs and associated ‘pseudo-mesh’ are shown in (iii and iv). Note that the mesh passes through the MTs and is more particulate than the K-fiber mesh. Tomogram thickness, 35.2 nm.DOI:http://dx.doi.org/10.7554/eLife.07635.005
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fig1s2: The mesh is associated with K-fiber MTs.(A) 3D rendering of ‘non-mesh’ (brown) in a tomogram of a single K-fiber. Single orthoslice (i), with added rendering (MTs, green; mesh, yellow) (ii) and model alone (iii), is shown. Rendering the mesh involves segmenting density that is attached to the MTs. Here, density to the upper right of the K-fiber was rendered, although it was not touching MTs. The result is a particulate 3D structure that is dissimilar to the K-fiber mesh. (B) Translation of MT map from the tomogram in A, to the upper right corner. Mesh detection was performed as described in ‘Materials and methods’. Single orthoslice view (i), with added rendering (MTs, green; mesh, yellow) (ii). Zoomed views of two MTs and associated ‘pseudo-mesh’ are shown in (iii and iv). Note that the mesh passes through the MTs and is more particulate than the K-fiber mesh. Tomogram thickness, 35.2 nm.DOI:http://dx.doi.org/10.7554/eLife.07635.005

Mentions: To obtain an unbiased view of the mesh, we developed a semi-automated segmentation method for 3D model building (Figure 1B, Video 1). This method was used for all subsequent quantification. We found that mesh preservation was superior using HPF/FS compared with chemical fixation (Figure 1—figure supplement 1). Moreover, the mesh was associated with K-fiber MTs. In contrast, segmentation of non-K-fiber areas resulted in distinct, particulate density and translating MTs to a non-K-fiber area meant that globular density, which passed through the MTs, was detected (Figure 1—figure supplement 2).


The mesh is a network of microtubule connectors that stabilizes individual kinetochore fibers of the mitotic spindle.

Nixon FM, Gutiérrez-Caballero C, Hood FE, Booth DG, Prior IA, Royle SJ - Elife (2015)

The mesh is associated with K-fiber MTs.(A) 3D rendering of ‘non-mesh’ (brown) in a tomogram of a single K-fiber. Single orthoslice (i), with added rendering (MTs, green; mesh, yellow) (ii) and model alone (iii), is shown. Rendering the mesh involves segmenting density that is attached to the MTs. Here, density to the upper right of the K-fiber was rendered, although it was not touching MTs. The result is a particulate 3D structure that is dissimilar to the K-fiber mesh. (B) Translation of MT map from the tomogram in A, to the upper right corner. Mesh detection was performed as described in ‘Materials and methods’. Single orthoslice view (i), with added rendering (MTs, green; mesh, yellow) (ii). Zoomed views of two MTs and associated ‘pseudo-mesh’ are shown in (iii and iv). Note that the mesh passes through the MTs and is more particulate than the K-fiber mesh. Tomogram thickness, 35.2 nm.DOI:http://dx.doi.org/10.7554/eLife.07635.005
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4495718&req=5

fig1s2: The mesh is associated with K-fiber MTs.(A) 3D rendering of ‘non-mesh’ (brown) in a tomogram of a single K-fiber. Single orthoslice (i), with added rendering (MTs, green; mesh, yellow) (ii) and model alone (iii), is shown. Rendering the mesh involves segmenting density that is attached to the MTs. Here, density to the upper right of the K-fiber was rendered, although it was not touching MTs. The result is a particulate 3D structure that is dissimilar to the K-fiber mesh. (B) Translation of MT map from the tomogram in A, to the upper right corner. Mesh detection was performed as described in ‘Materials and methods’. Single orthoslice view (i), with added rendering (MTs, green; mesh, yellow) (ii). Zoomed views of two MTs and associated ‘pseudo-mesh’ are shown in (iii and iv). Note that the mesh passes through the MTs and is more particulate than the K-fiber mesh. Tomogram thickness, 35.2 nm.DOI:http://dx.doi.org/10.7554/eLife.07635.005
Mentions: To obtain an unbiased view of the mesh, we developed a semi-automated segmentation method for 3D model building (Figure 1B, Video 1). This method was used for all subsequent quantification. We found that mesh preservation was superior using HPF/FS compared with chemical fixation (Figure 1—figure supplement 1). Moreover, the mesh was associated with K-fiber MTs. In contrast, segmentation of non-K-fiber areas resulted in distinct, particulate density and translating MTs to a non-K-fiber area meant that globular density, which passed through the MTs, was detected (Figure 1—figure supplement 2).

Bottom Line: Molecular manipulation of the mesh by overexpression of TACC3 causes disorganization of the K-fiber MTs.We propose that the mesh stabilizes K-fibers by pulling MTs together and thereby maintaining the integrity of the fiber.Our work thus identifies the K-fiber meshwork of linked multipolar connectors as a key integrator and determinant of K-fiber structure and function.

View Article: PubMed Central - PubMed

Affiliation: Division of Biomedical Cell Biology, Warwick Medical School, Coventry, United Kingdom.

ABSTRACT
Kinetochore fibers (K-fibers) of the mitotic spindle are force-generating units that power chromosome movement during mitosis. K-fibers are composed of many microtubules that are held together throughout their length. Here, we show, using 3D electron microscopy, that K-fiber microtubules (MTs) are connected by a network of MT connectors. We term this network 'the mesh'. The K-fiber mesh is made of linked multipolar connectors. Each connector has up to four struts, so that a single connector can link up to four MTs. Molecular manipulation of the mesh by overexpression of TACC3 causes disorganization of the K-fiber MTs. Optimal stabilization of K-fibers by the mesh is required for normal progression through mitosis. We propose that the mesh stabilizes K-fibers by pulling MTs together and thereby maintaining the integrity of the fiber. Our work thus identifies the K-fiber meshwork of linked multipolar connectors as a key integrator and determinant of K-fiber structure and function.

No MeSH data available.


Related in: MedlinePlus