  Cytoskeletal networks, which are essentially motor-filament assemblies, play
a major role in many developmental processes involving structural remodeling
and shape changes. These are achieved by nonequilibrium self-organization
processes that generate functional patterns and drive intracellular transport.
We construct a minimal physical model that incorporates the coupling between
nonlinear elastic responses of individual filaments and force-dependent motor
action. By performing stochastic simulations we show that the interplay of
motor processes, described as driving anti-correlated motion of the network
vertices, and the network connectivity, which determines the percolation
character of the structure, can indeed capture the dynamical and structural
cooperativity which gives rise to diverse patterns observed experimentally. The
buckling instability of individual filaments is found to play a key role in
localizing collapse events due to local force imbalance. Motor-driven
buckling-induced node aggregation provides a dynamic mechanism that stabilizes
the two dimensional patterns below the apparent static percolation limit.
Coordinated motor action is also shown to suppress random thermal noise on
large time scales, the two dimensional configuration that the system starts
with thus remaining planar during the structural development. By carrying out
similar simulations on a three dimensional anchored network, we find that the
myosin-driven isotropic contraction of a well-connected actin network, when
combined with mechanical anchoring that confers directionality to the
collective motion, may represent a novel mechanism of intracellular transport,
as revealed by chromosome translocation in the starfish oocyte.
