Assessing the critical period for Rho kinase activity during Drosophila ventral furrow formation

• Published in: Developmental dynamics Vol. 241; no. 11; pp. 1729 - 1743
• Main Authors: Krajcovic, Melissa M., Minden, Jonathan S.
• Format: Journal Article
• Language: English
• Published: New York Wiley-Liss, Inc 01.11.2012; Wiley‐Liss, Inc; Wiley Subscription Services, Inc
• Subjects: Amides - pharmacology; Animals; Drosophila; Embryo, Nonmammalian - drug effects; Embryo, Nonmammalian - metabolism; gastrulation; Gastrulation - drug effects; Gastrulation - genetics; Pyridines - pharmacology; Rho kinase; rho-Associated Kinases - antagonists & inhibitors; rho-Associated Kinases - metabolism; Time-Lapse Imaging; time-lapse microscopy; ventral furrow formation; Y-27632
• ISSN: 1058-8388; 1097-0177
• DOI: 10.1002/dvdy.23859

Background: Drosophila ventral furrow formation (VFF), which is the first morphogenetic event during embryo development, serves as a model for epithelial sheet folding. VFF can be subdivided into five cell shape changes: apical membrane flattening, apicobasal nuclear migration, apicobasal cell shortening, random apical constriction, and concerted apical constriction. These processes are generally believed to be driven by Rho kinase (Rok) activation of myosin II to stimulate the constriction of the apical actomyosin network. To test the role of Rok and its downstream target myosin II in VFF, timed injections of the Rok inhibitor, Y‐27632, were performed. Results: Embryos injected with Y‐27632 before the concerted apical constriction phase of VFF were able to execute apicobasal nuclear migration and random apical constriction, but were unable to enter the concerted apical constriction phase. Embryos injected with Y‐27632 during concerted apical constriction reverted to the transition point between random apical constriction and concerted apical constriction. Finally, embryos injected with Y‐27632 upon the initiation of furrow ingression were able to complete VFF. Conclusions: Together these results suggest a critical period for Rok activity and presumably myosin II activation during the initiation of the concerted apical constriction phase of VFF. Developmental Dynamics 241:1729–1743, 2012. © 2012 Wiley Periodicals, Inc. Key findings: Inhibition of Rho kinase by Y‐27632 injection before the start of ventral furrow formation (VFF) blocks the completion of VFF, but not the initial steps of VFF. There is a brief critical period for the requirement of Rho kinase activity, hence myosin II activity, during the concerted apical constriction phase of VFF. VFF processes outside of this critical period do not require Rho kinase or myosin II activity.