The role of actin filament brancher Arp2/3 in the dynamics and structures of actomyosin networks*

Actomyosin network contractility underlies the motility and division of a cell, involving contraction and expansion that are driven by active protein motors and actin treadmilling. In this work, we present novel computational and theoretical approaches to model contractility and growth in actomyosin networks and evaluate the spatiotemporal patterns of actin reorganization. We consider two different actomyosin network morphologies, unbranched and branched. For the unbranched case, the system includes motor proteins (non-muscle myosin IIA (NMIIA)) and cross-linker proteins (α-actinin). For the branched case, the system includes a third component—Arp2/3 complexes—that allows us to investigate the role of branching in actomyosin contractility. We observe that linkers modulate contraction in the unbranched and the branched actomyosin networks. The branched actomyosin networks relax more slowly than their unbranched counterparts. However, the branched networks show pronounced convulsive contractions. We expect our results to give an insight into the importance of the branched morphological formation in enhancing contractility of the actomyosin networks.