Final answer:
Nucleation of actin polymerization in dendritic networks of actin filaments in lamellipodia is mostly performed by the Arp2/3 complex.
Step-by-step explanation:
In the dendritic networks of actin filaments in lamellipodia, the nucleation of actin polymerization is primarily conducted by the Arp2/3 complex, which binds to existing filaments, creating new branches at a characteristic 70-degree angle. These branched structures facilitate cell movement and play a fundamental role in various cellular processes, such as the extension of the cell edge in lamellipodia. The Arp2/3 complex is a crucial component for the generation of a dendritic network that enables the dynamic reorganization of the cytoskeleton, essential for cell motility and generation of force at the leading edge of migrating cells.