FIGURE 10:

Model for macrophage fusion initiated by an actin-based protrusion. (A) The interface between two closely apposing macrophages contains numerous thin actin-based protrusions. A wave of podosomes moves from the interior of the cell that initiates fusion to the site of cell–cell contact. (B) Once podosomes arrive and align at the site of contact with the acceptor macrophage, membrane fusion is initiated by a single protrusion and podosomes from the donor macrophage advance into the acceptor macrophage. (C) The actin network at the site of fusion rapidly reorganizes to expand the initial pore. (D) The actin cytoskeleton and nuclei undergo directional integration.