- Simon Alberti
- Jan Brugués
- Suzanne Eaton
- Anne Grapin-Botton
- Michael Hiller
- Alf Honigmann
- Wieland Huttner
- Anthony Hyman
- Florian Jug
- Elisabeth Knust
- Moritz Kreysing
- Teymuras Kurzchalia
- Carl Modes
- Gene Myers
- André Nadler
- Caren Norden
- Gaia Pigino
- Jochen Rink
- Ivo Sbalzarini
- Andrej Shevchenko
- Jacqueline Tabler
- Dora Tang
- Pavel Tomancak
- Agnes Toth-Petroczy
- Nadine Vastenhouw
- Christoph Zechner
- Marino Zerial
Anyone who watches a movie of a developing embryo is immediately struck by the dramatic choreography of tissue movements and shape changes, and appreciates intuitively that growth and morphogenesis depend on organized physical forces exerted by cells. Epithelial cells, like those in mesenchymal tissues, can sense and exert forces where they contact the extracellular matrix. They can also sense and exert forces cells on each other through their apico-lateral contacts. How do epithelial cells polarize their force generating machinery and remodel their contacts to drive oriented tissue growth and morphogenesis? We are exploring these questions in the developing wing of Drosophila using genetic and biophysical approaches, along with quantitative image analysis and modelling.
Most of the growth of the future wing occurs in larvae (Figure 1A). At this stage, the wing epithelium is called a wing imaginal disc, and consists of a folded epithelial sac with an apical lumen. Although the shape of the wing is unrecognizable, morphogen signalling systems present at lineage restriction boundaries are already controlling growth, and generating patterns of gene expression that will later specify the position of wing veins and sensory organs. When larvae have reached a critical size, they stop feeding and pupariate. At this time, the wing imaginal disc begins to undergo dramatic morphogenetic movements that sculpt the wing into its adult shape. These occur in two different phases. First, the larval wing epithelium essentially turns itself inside out – changing from an epithelial sac with an apical lumen to an epithelial bilayer whose basal sides are opposed to each other (Figure 1B).
This process, called wing eversion, produces a crude approximation of the adult wing shape and ends as wing epithelial cells secrete a temporary cuticle from their apical surface (Figure 1C).
The second phase of morphogenesis, called hinge contraction/elongation, begins with the shedding of the temporary cuticle throughout most of the wing (Figure 1C,D). As the cuticle is released, patterned contractions shape the wing hinge and reduce its area. These contractions generate anisotropic tension along the proximal-distal (PD) axis of the adjacent wing blade because it remains connected to the overlying cuticle at its edge. This produces anisotropic tissue flows that elongate the wing in the PD axis and narrow it in the anterior-posterior (AP) axis. During these flows, wing epithelial cells divide, change shape and exchange neighbours (Aigouy et al., 2010). They also regularize their packing geometry to form an array of hexagons (Classen et al., 2005).
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