Limits...
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

Inter-MT linkages are defined connectors with heterogeneous MT-mesh contacts.(A) Examples of bipolar, tripolar, and quadrupolar connectors within the mesh. Single orthoslices from tomograms showing examples of different connectors. MTs are hand-rendered (green), mesh is automatically detected (yellow, see ‘Materials and methods’), and example connectors are highlighted orange. Tomogram thickness, 51.3 nm (bipolar) and 35.2 nm (tripolar and quadrupolar). (B) Box plots to show the volume of bipolar, tripolar, and quadrupolar connectors within the mesh from multiple tomograms. (C) Box plot to show the ratio of the volume of mesh relative to MTs (walls only) or MTs + lumens (‘filled-in’ MTs). Box plots show the median, 75th and 25th percentile, and whiskers show 90th and 10th percentile. (D) Heterogeneity of contacts between mesh and MTs. Two pairs of MTs are shown with a simple bipolar connector (above) or with a more complex connection (below). MTs (green) are shown with a single component of the mesh (orange). The contact points between the selected mesh and the MTs are shown in pink. Note the extensive mesh-MT contacts in the lower example. Tomogram thickness, 66.4 nm (simple) 64.8 nm (network). For scale, MTs are 25 nm in diameter.DOI:http://dx.doi.org/10.7554/eLife.07635.007
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4495718&req=5

fig2: Inter-MT linkages are defined connectors with heterogeneous MT-mesh contacts.(A) Examples of bipolar, tripolar, and quadrupolar connectors within the mesh. Single orthoslices from tomograms showing examples of different connectors. MTs are hand-rendered (green), mesh is automatically detected (yellow, see ‘Materials and methods’), and example connectors are highlighted orange. Tomogram thickness, 51.3 nm (bipolar) and 35.2 nm (tripolar and quadrupolar). (B) Box plots to show the volume of bipolar, tripolar, and quadrupolar connectors within the mesh from multiple tomograms. (C) Box plot to show the ratio of the volume of mesh relative to MTs (walls only) or MTs + lumens (‘filled-in’ MTs). Box plots show the median, 75th and 25th percentile, and whiskers show 90th and 10th percentile. (D) Heterogeneity of contacts between mesh and MTs. Two pairs of MTs are shown with a simple bipolar connector (above) or with a more complex connection (below). MTs (green) are shown with a single component of the mesh (orange). The contact points between the selected mesh and the MTs are shown in pink. Note the extensive mesh-MT contacts in the lower example. Tomogram thickness, 66.4 nm (simple) 64.8 nm (network). For scale, MTs are 25 nm in diameter.DOI:http://dx.doi.org/10.7554/eLife.07635.007

Mentions: Having established a detection method, we next explored the anatomy of this novel subcellular structure. Three types of connectors within the mesh could be distinguished in these 3D models. Bipolar, tripolar, or quadrupolar connectors could be selected using the criterion of uninterrupted density that connects two, three, or four MTs, respectively (Figure 2A). These connectors were highly heterogeneous in size. Where the volumes of individual connectors could be determined easily, we found that bipolar, tripolar, and quadrupolar connectors had mean volumes of 6,689, 17,370, and 32,376 nm3, respectively (Figure 2B). Therefore, there is not a linear relationship between the number of struts in a connector and the connector volume. The volume of mesh within each fiber was, on average, equivalent to the volume of MTs that it encapsulates and larger than the volume of MT walls alone (Figure 2C). This observation establishes that the mesh is a major component of every K-fiber.10.7554/eLife.07635.007Figure 2.Inter-MT linkages are defined connectors with heterogeneous MT-mesh contacts.


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)

Inter-MT linkages are defined connectors with heterogeneous MT-mesh contacts.(A) Examples of bipolar, tripolar, and quadrupolar connectors within the mesh. Single orthoslices from tomograms showing examples of different connectors. MTs are hand-rendered (green), mesh is automatically detected (yellow, see ‘Materials and methods’), and example connectors are highlighted orange. Tomogram thickness, 51.3 nm (bipolar) and 35.2 nm (tripolar and quadrupolar). (B) Box plots to show the volume of bipolar, tripolar, and quadrupolar connectors within the mesh from multiple tomograms. (C) Box plot to show the ratio of the volume of mesh relative to MTs (walls only) or MTs + lumens (‘filled-in’ MTs). Box plots show the median, 75th and 25th percentile, and whiskers show 90th and 10th percentile. (D) Heterogeneity of contacts between mesh and MTs. Two pairs of MTs are shown with a simple bipolar connector (above) or with a more complex connection (below). MTs (green) are shown with a single component of the mesh (orange). The contact points between the selected mesh and the MTs are shown in pink. Note the extensive mesh-MT contacts in the lower example. Tomogram thickness, 66.4 nm (simple) 64.8 nm (network). For scale, MTs are 25 nm in diameter.DOI:http://dx.doi.org/10.7554/eLife.07635.007
© Copyright Policy
Related In: Results  -  Collection

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

fig2: Inter-MT linkages are defined connectors with heterogeneous MT-mesh contacts.(A) Examples of bipolar, tripolar, and quadrupolar connectors within the mesh. Single orthoslices from tomograms showing examples of different connectors. MTs are hand-rendered (green), mesh is automatically detected (yellow, see ‘Materials and methods’), and example connectors are highlighted orange. Tomogram thickness, 51.3 nm (bipolar) and 35.2 nm (tripolar and quadrupolar). (B) Box plots to show the volume of bipolar, tripolar, and quadrupolar connectors within the mesh from multiple tomograms. (C) Box plot to show the ratio of the volume of mesh relative to MTs (walls only) or MTs + lumens (‘filled-in’ MTs). Box plots show the median, 75th and 25th percentile, and whiskers show 90th and 10th percentile. (D) Heterogeneity of contacts between mesh and MTs. Two pairs of MTs are shown with a simple bipolar connector (above) or with a more complex connection (below). MTs (green) are shown with a single component of the mesh (orange). The contact points between the selected mesh and the MTs are shown in pink. Note the extensive mesh-MT contacts in the lower example. Tomogram thickness, 66.4 nm (simple) 64.8 nm (network). For scale, MTs are 25 nm in diameter.DOI:http://dx.doi.org/10.7554/eLife.07635.007
Mentions: Having established a detection method, we next explored the anatomy of this novel subcellular structure. Three types of connectors within the mesh could be distinguished in these 3D models. Bipolar, tripolar, or quadrupolar connectors could be selected using the criterion of uninterrupted density that connects two, three, or four MTs, respectively (Figure 2A). These connectors were highly heterogeneous in size. Where the volumes of individual connectors could be determined easily, we found that bipolar, tripolar, and quadrupolar connectors had mean volumes of 6,689, 17,370, and 32,376 nm3, respectively (Figure 2B). Therefore, there is not a linear relationship between the number of struts in a connector and the connector volume. The volume of mesh within each fiber was, on average, equivalent to the volume of MTs that it encapsulates and larger than the volume of MT walls alone (Figure 2C). This observation establishes that the mesh is a major component of every K-fiber.10.7554/eLife.07635.007Figure 2.Inter-MT linkages are defined connectors with heterogeneous MT-mesh contacts.

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