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Elasticity and structure of eukaryote chromosomes studied by micromanipulation and micropipette aspiration.

Houchmandzadeh B, Marko JF, Chatenay D, Libchaber A - J. Cell Biol. (1997)

Bottom Line: Larger deformations of 10 to 100 times irreversibly and progressively transform the chromosomes into a "thin filament," parts of which display a helical organization.Chromosomes break for elongations of the order of 100 times, at which time the applied force is around 100 nanonewtons.Knowing the Young modulus allows us to estimate that the force exerted by the spindle on a newt chromosome at anaphase is roughly one nanonewton.

View Article: PubMed Central - PubMed

Affiliation: Centre National de la Recherche Scientifique (CNRS), Laboratoire de Spectrométrie Physique, Saint-Martin-d'Hères, France. bahram@coucou.ujf-grenoble.fr

ABSTRACT
The structure of mitotic chromosomes in cultured newt lung cells was investigated by a quantitative study of their deformability, using micropipettes. Metaphase chromosomes are highly extensible objects that return to their native shape after being stretched up to 10 times their normal length. Larger deformations of 10 to 100 times irreversibly and progressively transform the chromosomes into a "thin filament," parts of which display a helical organization. Chromosomes break for elongations of the order of 100 times, at which time the applied force is around 100 nanonewtons. We have also observed that as mitosis proceeds from nuclear envelope breakdown to metaphase, the native chromosomes progressively become more flexible. (The elastic Young modulus drops from 5,000 +/- 1,000 to 1,000 +/- 200 Pa.) These observations and measurements are in agreement with a helix-hierarchy model of chromosome structure. Knowing the Young modulus allows us to estimate that the force exerted by the spindle on a newt chromosome at anaphase is roughly one nanonewton.

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A broken thin filament attached to the pipette and deformed by flow. From top to bottom: (a) the original shape; (b) the filament stretched by the flow (the flow was produced by movement of the XY stage relative to the pipette); (c) 1.4 s after flow stopped;  and (d) 2.8 s after flow stopped. Bar, 10 μm.
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Figure 6: A broken thin filament attached to the pipette and deformed by flow. From top to bottom: (a) the original shape; (b) the filament stretched by the flow (the flow was produced by movement of the XY stage relative to the pipette); (c) 1.4 s after flow stopped; and (d) 2.8 s after flow stopped. Bar, 10 μm.

Mentions: When the tension on the thin filament is released, following either partial or total conversion of the chromosome to this form, portions of it take on a helical shape. Each helical turn involves 5 to 10 μm of relaxed thin filament. Both left- and right-handed curls were observed. Fig. 6 a shows a thin filament after its breakage. If we then perturb it with a flow, the helical filament behaves like a spiral spring (Fig. 6, b–d).


Elasticity and structure of eukaryote chromosomes studied by micromanipulation and micropipette aspiration.

Houchmandzadeh B, Marko JF, Chatenay D, Libchaber A - J. Cell Biol. (1997)

A broken thin filament attached to the pipette and deformed by flow. From top to bottom: (a) the original shape; (b) the filament stretched by the flow (the flow was produced by movement of the XY stage relative to the pipette); (c) 1.4 s after flow stopped;  and (d) 2.8 s after flow stopped. Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2139812&req=5

Figure 6: A broken thin filament attached to the pipette and deformed by flow. From top to bottom: (a) the original shape; (b) the filament stretched by the flow (the flow was produced by movement of the XY stage relative to the pipette); (c) 1.4 s after flow stopped; and (d) 2.8 s after flow stopped. Bar, 10 μm.
Mentions: When the tension on the thin filament is released, following either partial or total conversion of the chromosome to this form, portions of it take on a helical shape. Each helical turn involves 5 to 10 μm of relaxed thin filament. Both left- and right-handed curls were observed. Fig. 6 a shows a thin filament after its breakage. If we then perturb it with a flow, the helical filament behaves like a spiral spring (Fig. 6, b–d).

Bottom Line: Larger deformations of 10 to 100 times irreversibly and progressively transform the chromosomes into a "thin filament," parts of which display a helical organization.Chromosomes break for elongations of the order of 100 times, at which time the applied force is around 100 nanonewtons.Knowing the Young modulus allows us to estimate that the force exerted by the spindle on a newt chromosome at anaphase is roughly one nanonewton.

View Article: PubMed Central - PubMed

Affiliation: Centre National de la Recherche Scientifique (CNRS), Laboratoire de Spectrométrie Physique, Saint-Martin-d'Hères, France. bahram@coucou.ujf-grenoble.fr

ABSTRACT
The structure of mitotic chromosomes in cultured newt lung cells was investigated by a quantitative study of their deformability, using micropipettes. Metaphase chromosomes are highly extensible objects that return to their native shape after being stretched up to 10 times their normal length. Larger deformations of 10 to 100 times irreversibly and progressively transform the chromosomes into a "thin filament," parts of which display a helical organization. Chromosomes break for elongations of the order of 100 times, at which time the applied force is around 100 nanonewtons. We have also observed that as mitosis proceeds from nuclear envelope breakdown to metaphase, the native chromosomes progressively become more flexible. (The elastic Young modulus drops from 5,000 +/- 1,000 to 1,000 +/- 200 Pa.) These observations and measurements are in agreement with a helix-hierarchy model of chromosome structure. Knowing the Young modulus allows us to estimate that the force exerted by the spindle on a newt chromosome at anaphase is roughly one nanonewton.

Show MeSH