On cables, clouds and comets

Much is known about how during cell division, the nuclear genome is partitioned between the two daughter cells. But what about other cellular components — for instance, organelles such as endoplasmic reticulum and mitochondria? Here, Erika Holzbaur and colleagues investigate the mechanism of mitochondrial organization and inheritance during mitotic cell division. They find that several assemblies of the actin cytoskeleton have distinct but complementary roles in ensuring equal and random mitochondrial inheritance. The find that a meshwork of actin cables throughout the cytoplasm organizes mitochondrial positioning to ensure equal segregation of mitochondrial mass into the two daughter cells. They also see a dynamic wave of actin filaments on the surface of mitochondria. The waves break symmetry to envelope associated mitochondria within actin clouds. The clouds in turn evolve into elongated comet tails, which promote bursts of movement, shuffling mitochondria within the mother cell and thus randomizing inheritance of healthy and damaged mitochondria between daughter cells.