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Self-organization of an acentrosomal microtubule network at the basal cortex of polarized epithelial cells.

Reilein A, Yamada S, Nelson WJ - J. Cell Biol. (2005)

Bottom Line: Microtubules undergoing dynamic instability without any stabilization points continuously remodel their organization without reaching a steady-state network.However, the addition of increased microtubule stabilization at microtubule-microtubule and microtubule-cortex interactions results in the rapid assembly of a steady-state microtubule network in silico that is remarkably similar to networks formed in situ.These results define minimal parameters for the self-organization of an acentrosomal microtubule network.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Beckman Center for Molecular and Genetic Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.

ABSTRACT
Mechanisms underlying the organization of centrosome-derived microtubule arrays are well understood, but less is known about how acentrosomal microtubule networks are formed. The basal cortex of polarized epithelial cells contains a microtubule network of mixed polarity. We examined how this network is organized by imaging microtubule dynamics in acentrosomal basal cytoplasts derived from these cells. We show that the steady-state microtubule network appears to form by a combination of microtubule-microtubule and microtubule-cortex interactions, both of which increase microtubule stability. We used computational modeling to determine whether these microtubule parameters are sufficient to generate a steady-state acentrosomal microtubule network. Microtubules undergoing dynamic instability without any stabilization points continuously remodel their organization without reaching a steady-state network. However, the addition of increased microtubule stabilization at microtubule-microtubule and microtubule-cortex interactions results in the rapid assembly of a steady-state microtubule network in silico that is remarkably similar to networks formed in situ. These results define minimal parameters for the self-organization of an acentrosomal microtubule network.

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Assembly of the microtubule network in a basal cytoplast. In a basal cytoplast that had only a few microtubules remaining after sonication, microtubules assembled into a steady-state network in ∼10 min. The network had a similar appearance 15 min after the assembly (compare the last two panels), indicating that it had reached a steady state. Arrows indicate examples of microtubules arising from the sides of other microtubules. Bar, 5 μm.
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fig8: Assembly of the microtubule network in a basal cytoplast. In a basal cytoplast that had only a few microtubules remaining after sonication, microtubules assembled into a steady-state network in ∼10 min. The network had a similar appearance 15 min after the assembly (compare the last two panels), indicating that it had reached a steady state. Arrows indicate examples of microtubules arising from the sides of other microtubules. Bar, 5 μm.

Mentions: Our live imaging showed that microtubules on MDCK basal patches form intersections at the growing (plus) ends of microtubules with the sides of microtubules (Reilein and Nelson, 2005) as well as the minus end (origin of growth) and the sides of microtubules (Fig. 4, A and B, and see Fig. 8). Presumably, γ-tubulin is localizing to the minus end of the microtubule at branch points, although we cannot confirm this directly from the fixed images. We observed two different configurations of microtubule ends intersecting with the sides of microtubules by electron microscopy (Fig. 2). It is possible that these configurations could be plus and minus ends forming intersections with other microtubules, although other possibilities exist (for example, plus ends that are growing or pausing).


Self-organization of an acentrosomal microtubule network at the basal cortex of polarized epithelial cells.

Reilein A, Yamada S, Nelson WJ - J. Cell Biol. (2005)

Assembly of the microtubule network in a basal cytoplast. In a basal cytoplast that had only a few microtubules remaining after sonication, microtubules assembled into a steady-state network in ∼10 min. The network had a similar appearance 15 min after the assembly (compare the last two panels), indicating that it had reached a steady state. Arrows indicate examples of microtubules arising from the sides of other microtubules. Bar, 5 μm.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2171299&req=5

fig8: Assembly of the microtubule network in a basal cytoplast. In a basal cytoplast that had only a few microtubules remaining after sonication, microtubules assembled into a steady-state network in ∼10 min. The network had a similar appearance 15 min after the assembly (compare the last two panels), indicating that it had reached a steady state. Arrows indicate examples of microtubules arising from the sides of other microtubules. Bar, 5 μm.
Mentions: Our live imaging showed that microtubules on MDCK basal patches form intersections at the growing (plus) ends of microtubules with the sides of microtubules (Reilein and Nelson, 2005) as well as the minus end (origin of growth) and the sides of microtubules (Fig. 4, A and B, and see Fig. 8). Presumably, γ-tubulin is localizing to the minus end of the microtubule at branch points, although we cannot confirm this directly from the fixed images. We observed two different configurations of microtubule ends intersecting with the sides of microtubules by electron microscopy (Fig. 2). It is possible that these configurations could be plus and minus ends forming intersections with other microtubules, although other possibilities exist (for example, plus ends that are growing or pausing).

Bottom Line: Microtubules undergoing dynamic instability without any stabilization points continuously remodel their organization without reaching a steady-state network.However, the addition of increased microtubule stabilization at microtubule-microtubule and microtubule-cortex interactions results in the rapid assembly of a steady-state microtubule network in silico that is remarkably similar to networks formed in situ.These results define minimal parameters for the self-organization of an acentrosomal microtubule network.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Beckman Center for Molecular and Genetic Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.

ABSTRACT
Mechanisms underlying the organization of centrosome-derived microtubule arrays are well understood, but less is known about how acentrosomal microtubule networks are formed. The basal cortex of polarized epithelial cells contains a microtubule network of mixed polarity. We examined how this network is organized by imaging microtubule dynamics in acentrosomal basal cytoplasts derived from these cells. We show that the steady-state microtubule network appears to form by a combination of microtubule-microtubule and microtubule-cortex interactions, both of which increase microtubule stability. We used computational modeling to determine whether these microtubule parameters are sufficient to generate a steady-state acentrosomal microtubule network. Microtubules undergoing dynamic instability without any stabilization points continuously remodel their organization without reaching a steady-state network. However, the addition of increased microtubule stabilization at microtubule-microtubule and microtubule-cortex interactions results in the rapid assembly of a steady-state microtubule network in silico that is remarkably similar to networks formed in situ. These results define minimal parameters for the self-organization of an acentrosomal microtubule network.

Show MeSH