I attended the “Cell and Tissue Morphogenesis” minisymposium this morning and, I have to say, the co-chairs Darren Gilmour (EMBL) and Cheryll Tickle (University of Bath) put together a fantastic program of speakers. Gilmour began by reminding the audience that cell biology and developmental biology have common origins: much of the early cell biological work by scientists such as Theodor Boveri was conducted in developing embryos, and it was only with the advent of cell culture that the cell and developmental biology fields drifted apart.
But recent years have seen cell biology return to more developmental contexts, a trend amply illustrated by the talks that followed Gilmour’s introduction. Rodrigo Fernandez-Gonzalez, from Jennifer Zallen’s lab at Memorial Sloan Kettering discussed his work showing that tissue tension within elongating Drosophila embryos feeds back to stabilize myosin II at cell junctions so that the actin-based motor can drive the cell rearrangements necessary for further tissue elongation. Ronen Zaidel-Bar (National University of Singapore) followed with a presentation of his recent JCB paper showing that the membrane-bending protein SRGP-1 promotes intercellular adhesion formation.
Lance Davidson (University of Pittsburgh) returned to the theme of embryo elongation mechanics using what I thought was a really cool system: explanted pieces of Xenopus embryos that continue to undergo morphogenetic movements in vitro as if they were still in an intact embryo. Davidson has used this system to measure the stiffness of different parts of the embryo as it elongates and determined that this property of developing Xenopus tissues is controlled by the actomyosin cytoskeleton. Surprisingly, tissue stiffness increases when microtubules are depolymerized with nocodazole, due to the release of a Rho GTPase exchange factor that stimulates actin assembly.
Gilmour himself finished off the session with a presentation of his studies on the Zebrafish lateral line primordium. This too is a really cool system. The lateral line primordium is a group of cells that migrate collectively through the zebrafish, forming and depositing mechanosensory hair cell organs at regular intervals along the way. Cells at the front of the migrating promordium have a mesenchymal phenotype but the trailing cells are more epithelial in character. The primordium needs both types of cells to migrate along the lateral line. Gilmour described some of the signaling mechanisms (such as FGF) that organize the two cell types and how they coordinate with each other to facilitate persistent directional migration of the entire tissue. As Gilmour said in his introduction, the beauty of reintroducing cell biology into a developmental context is that it allows researchers to study the influence that cells have on each other.
Image © Zaidel-Bar et al., 2010