Anillins, conserved proteins that help stabilize and remodel the actin cytoskeleton, have been implicated in cytokinesis in several systems and in the cellularization of the syncytial Drosophila embryo. Two studies now shed additional light on the role of anillins in contractile processes. On p. , Field et al. report that in a series of Drosophila Anillin mutants, the ingression of the furrows that form in the plasma membrane to create individual cells during cellularization is slowed. Moreover, the new plasma membrane deposited behind the furrows is unstable in these mutants. Anillin interacts with the septins, GTPases that polymerize to form filaments and that concentrate in ingressing furrows. Field et al. show that the severity of a mutant's phenotype correlates with the extent of septin disruption, indicating that septins are targeted to furrows by interacting with Anillin. On p. , Maddox et al. characterize two C. elegans anillin homologues, ANI-1 and ANI-2, that have essential roles in the early embryo and gonad, respectively. ANI-1 is required for the cytokinetic events that extrude the two polar bodies during oocyte meiosis, and organizes myosin to produce cortical ruffles during polarity establishment in the one-cell stage embryo. Like DrosophilaAnillin, ANI-1 is required to recruit septins to the base of ingressing ruffles and to contractile rings, but both ANI-1 and the septins are dispensable for mitotic cytokinesis in the early C. elegans embryo. ANI-2 functions in the syncytial gonad of the adult worm, where nuclei gradually cellularize to form oocytes. In ANI-2-depleted worms, the gonad collapses and fails to produce oocytes of uniform size. Together, these papers highlight the conserved roles of anillins in stabilizing membranes in syncytial structures and in organizing cortical contractility, possibly by acting as versatile crosslinkers of cortical cytoskeleton components.
