Martin Behrndt        Pedro Campinho        Julien Compagnon          Hitoshi Morita


Actomyosin contractility plays a mayor role in epithelial morphogenesis in development. To unravel the function of actomyosin-mediated contraction for epithelial morphogenesis in gastrulating zebrafish embryos, we are studying the formation of two epithelial structures - the Enveloping Cell Layer (EVL) and Kupffer's Vesicle (KV). The EVL is a squamous epithelial cell layer at the surface of the embryo, which during the course of gastrulation spreads over the yolk sac to completely engulf it at the end of gastrulation. KV is formed from a small group of mesenchymal cells induced at the dorsal side of the early gastrula, which undergo an mesenchymal-to-epithelial transition to assemble into a luminal vesicle, which is ciliated on its inside and required for left-right asymmetry of the developing embryo. To determine the role of actomyosin contraction for the formation of these structures, we are using a laser-cutter to reveal tissue tension, and multi-photon and fast-scanning microscopy to visualize the actomyosin cytoskeleton in transgenic embryos expressing fluorescently-tagged fusion proteins of various cytoskeletal and adhesion components.

Confocal images of KV at bud stage (10 hpf) and 6-somite stage (12 hpf).DNA=blue; sox17:GFP=green; aPKC=red.









EVL cells ectopically expressing PKC exhibit pronounced changes in apicobasal polarization and cell shape.

EVL movement during epiboly. Embryos were injected with GPI-RFP mRNA at 1-cell stage to label cell membranes, and EVL movement was recorded for 3 h starting at sphere stage (4 hpf).