Septins promote F-actin ring formation by crosslinking actin filaments into curved bundles

• Published in: Nature cell biology Vol. 16; no. 4; pp. 322 - 334
• Main Authors: Mavrakis, Manos, Azou-Gros, Yannick, Tsai, Feng-Ching, Alvarado, José, Bertin, Aurélie, Iv, Francois, Kress, Alla, Brasselet, Sophie, Koenderink, Gijsje H., Lecuit, Thomas
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.04.2014; Nature Publishing Group
• Subjects: 631/136/334/1582/715; 631/80/128; 631/80/128/1276; Actin; Actin Cytoskeleton - metabolism; Actins - metabolism; Actomyosin - metabolism; Animals; Binding proteins; Cancer Research; Cell Biology; Cell Division; Cell research; Cellular Biology; Cleavage Stage, Ovum - metabolism; Cytokinesis; Cytokinesis - physiology; Developmental Biology; Drosophila melanogaster - embryology; Drosophila melanogaster - genetics; Embryos; Humans; Insects; Life Sciences; Membranes; Molecular Motor Proteins - genetics; Molecular Motor Proteins - metabolism; Mutation; Myosins - genetics; Myosins - metabolism; Properties; Protein Binding - physiology; Proteins; Septins - genetics; Septins - metabolism; Stem Cells; Subcellular Processes; France
• ISSN: 1465-7392; 1476-4679
• DOI: 10.1038/ncb2921

Animal cell cytokinesis requires a contractile ring of crosslinked actin filaments and myosin motors. How contractile rings form and are stabilized in dividing cells remains unclear. We address this problem by focusing on septins, highly conserved proteins in eukaryotes whose precise contribution to cytokinesis remains elusive. We use the cleavage of the Drosophila melanogaster embryo as a model system, where contractile actin rings drive constriction of invaginating membranes to produce an epithelium in a manner akin to cell division. In vivo functional studies show that septins are required for generating curved and tightly packed actin filament networks. In vitro reconstitution assays show that septins alone bundle actin filaments into rings, accounting for the defects in actin ring formation in septin mutants. The bundling and bending activities are conserved for human septins, and highlight unique functions of septins in the organization of contractile actomyosin rings. Lecuit and colleagues use Drosophila embryo cellularization as an in vivo model system, as well as in vitro reconstitution assays, to show that septin mutant embryos display defects in actin organization and that septins are able to crosslink, bundle and bend actin filaments into rings.