Systems Biomechanics of the Cell - Systems Biomechanics of the Cell - page 39

Fig. 22 Angle of the
unstressed microtubule
direction, beyond which
metastable forms do not exist,
in the course of continuous
microtubule elongation in a
flat cell. The angle is as
defined in Fig. 1 . Reproduced
from Maly and Maly ( 2010 )
with permission from
Elsevier
Fig. 23 Equilibrium forms of a microtubule aster in a flat cell during elongation and shortening of
microtubules. Microtubule length is indicated in relation to the cell radius. Reproduced from Maly
and Maly ( 2010 ) with permission from Elsevier
general irreversible should apply directly to more complex, realistic cytoskeletons.
It does not depend on the simplicity of the aster structure in the computational
examples shown, but only on the presence of metastable microtubule forms, which
model feature is realistic, as discussed in the previous section.
The model of Maly and Maly ( 2010 ) establishes a qualitative difference between
the flat and three-dimensional cases. In three dimensions, the aster adopts the
“combed” conformation, in which all microtubules are buckled in the same direc-
tion (Fig. 3 ). Their distal (plus) ends are bent away from the direction of the centro-
some displacement from the cell center. This kind of aster structure is “memoryless”:
The directions of microtubule buckling remain the same if the centrosome is moved
by external forces or if the microtubule length changes, and there is only one