Functional Changes of Actin-Binding Proteins for Human Umbilical CD-105 Positive Stromal Cell Proliferation and Differentiation

Abstract

We perform a series of simulations to study the effects of myosin minifilaments on the stress distribution in a crosslinked actin network. Previous theoretical studies suggest that the maximum tension generated per myosin depends strongly on the length of the myosin minifilaments and the actin filaments (A. E. Carlsson, Phys. Rev. E74, 051912, 2006). We study both two-and three-dimensional actin networks. The two-dimensional actin network is modeled as a collection of randomly oriented rods connected at their edges to a square frame. Before including the myosin-induced stresses, we studied the elastic response of the network under affine and nonaffine strain. The network structures are obtained by minimization of an energy function including terms due to both stretching and bending of rods. Rods are allowed to rotate without any energy cost at a crosslink where it connects to another rod. After energy minimization following a strain, forces and torques exerted by the network on the walls and Young's modulus of the network are calculated. The myosin forces are included by treating each myosin minifilament as a force dipole whose components act on different actin filaments. Then evaluation of the forces on the walls allows us to calculate the tension induced per myosin. These calculations allow us to understand the myosin induced stress as a function of structure of the network, by varying properties like connectivity, filament length, the extent of branching, and the treadmilling rate.