Research Article: An Equatorial Contractile Mechanism Drives Cell Elongation but not Cell Division

Date Published: February 4, 2014

Publisher: Public Library of Science

Author(s): Ivonne M. Sehring, Bo Dong, Elsa Denker, Punit Bhattachan, Wei Deng, Birthe T. Mathiesen, Di Jiang, Michael Levine

Abstract: A cytokinesis-like contractile mechanism is co-opted in a different developmental scenario to achieve cell elongation instead of cell division in Ciona intestinalis.

Partial Text: Individual cell shape changes contribute significantly to morphogenesis during embryonic development [1]. The actomyosin network is a central player in the formation and transformation of functional cell shapes. Actin and myosin filaments are highly and dynamically organized in different developmental contexts, and often exist in a higher structure as a ring. The equatorial circumferential ring in cytokinesis is essential for the cell division to occur [2]. An actomyosin ring is also present in the yolk syncytial layer of zebrafish embryo, and is implicated in the epiboly movement of the enveloping cell layer [3]. In addition, the actomyosin ring is readily assembled after a wound in the cell membrane, and is responsible for the wound healing [4].

Our results demonstrate that the Ciona notochord actomyosin ring possesses a well-organized molecular architecture that is strikingly similar to that of the cytokinetic contractile machinery. Dynamic cortical flow contributes to the formation of the ring. Actin-based bleb-like membrane deformations occur at the basal surface. The elongation of Ciona notochord cells arises from a concerted effort of two force-generating mechanisms: equatorial constriction and repeated local basal contractions. Thus, the postmitotic notochord cells exploit significant components of the complex cytokinetic machinery not for cell division but for cell elongation.