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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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Stable helix formed after a plastic deformation. Bar, 10 μm.
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Figure 4: Stable helix formed after a plastic deformation. Bar, 10 μm.

Mentions: Fig. 3 shows an interesting aspect of the plastic behavior for ε ≈ 20. When the micropipette tip is brought back near the cell so as to slightly compress the chromosome, transient undulations develop along parts of the chromosome. Those undulating regions relax into a region of thicker straight chromosome after 1 to 2 s. If the pipette is pushed closer, stable helices appear (Fig. 4). Some but not all of the plastic deformation can be reabsorbed by the chromosome.


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

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

Stable helix formed after a plastic deformation. Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 4: Stable helix formed after a plastic deformation. Bar, 10 μm.
Mentions: Fig. 3 shows an interesting aspect of the plastic behavior for ε ≈ 20. When the micropipette tip is brought back near the cell so as to slightly compress the chromosome, transient undulations develop along parts of the chromosome. Those undulating regions relax into a region of thicker straight chromosome after 1 to 2 s. If the pipette is pushed closer, stable helices appear (Fig. 4). Some but not all of the plastic deformation can be reabsorbed by the chromosome.

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