FMNL1 polymerized actin filaments complete mitochondrial division downstream of Golgi-derived vesicles

Mitochondrial division includes contributions from several organelles yet the molecular machinery that facilitates the final Drp1-induced scission of the OMM is largely elusive. We elucidate that FMNL1, a formin family actin assembly factor, is recruited to the mitochondrial division sites through the TGN vesicles in a calcium dependent pathway to complete mitochondrial division. FMNL1 is activated specifically by Cdc42 that generates actin filaments to complete division of the OMM in Drp1 and actin-dependent pathway. Depletion of FMNL1 enhances early events in mitochondrial division pathway characterized by enhanced ER-mitochondrial contacts and increased Drp1 and TGN vesicles on mitochondria which still results in failed mitochondrial division.