Flow-independent accumulation of motor-competent non-muscle myosin II in the contractile ring is essential for cytokinesis

• Published in: bioRxiv
• Main Authors: Daniel Sampaio Osorio, Fung Yi Chan, Saramago, Joana, Leite, Joana, Silva, Ana Marta, Sobral, Ana Filipa, Gassmann, Reto, Carvalho, Ana Xavier
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 31.05.2018
• Subjects: Actin; Actomyosin; Cytokinesis; Embryos; Filaments; Genomes; Motor activity; Muscle contraction; Myosin
• DOI: 10.1101/333286

Cytokinesis in animal cells requires the assembly of a contractile actomyosin ring, whose subsequent constriction physically separates the two daughter cells. Non-muscle myosin II (myosin) is essential for cytokinesis, but the role of its motor activity remains poorly defined. Here, we examine cytokinesis in C. elegans one-cell embryos expressing myosin motor mutants generated by genome editing. Motor-dead myosin, which is capable of binding F-actin, does not support cytokinesis, and embryos co-expressing motor-dead and wild-type myosin are delayed in cytokinesis. Partially motor-impaired myosin also delays cytokinesis and renders contractile rings more sensitive to reduced myosin levels. Thus, myosin motor activity, rather than its ability to cross-link actin filaments, drives contractile ring assembly and constriction. We further demonstrate that myosin motor activity is required for long-range cortical actin flows, but that flows per se play a minor role in contractile ring assembly. Our results suggest that flow-independent recruitment of motor-competent myosin to the cell equator is both essential and rate-limiting for cytokinesis.