Dynamic actin-based epithelial adhesion and cell matching during Drosophila dorsal closure.
BACKGROUND
The adhesion of two epithelial sheets is a fundamental process that occurs throughout embryogenesis and during wound repair. Sealing of the dorsal epidermis along the midline of the Drosophila embryo provides a genetically tractable model to analyse the closure of such holes. Several studies indicate that the actin cytoskeleton plays a critical role in dorsal closure. Although many components of the signalling cascade directing this process have been identified, the precise cell-biological events upon which these signals act remain poorly described.


RESULTS
By confocal imaging of living fly embryos expressing green fluorescent protein (GFP)-tagged actin, we found that dorsal closure relies on the activity of dynamic filopodia and lamellipodia that extend from front-row cells to actively zipper the epithelial sheets together. As these epithelial fronts approach one another, we observed long, thin filopodia, apparently 'sampling' cells on the opposing face. When the assembly of these actin-based protrusions was blocked (by interfering with the activities of Cdc42 and Jun N-terminal kinase signalling), the adhesion and fusion of opposing epithelial cells was prevented and their ability to 'sense' correct partners was also blocked, leading to segment misalignment along the midline seam.


CONCLUSIONS
Dynamic, actin-based protrusions (filopodia and lamellae) are critical, both in the mechanics of epithelial adhesion during dorsal closure and in the correct 'matching' of opposing cells along the fusion seam.
Jacinto
A
A
Department of Anatomy and Developmental Biology, University College London, Gower Street, WC1E 6BT, London, UK. a.jacinto@ucl.ac.uk
Wood
W
W
Balayo
T
T
Turmaine
M
M
Martinez-Arias
A
A
Martin
P
P
D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D004330:Drosophila / Q000196:embryology / Q000502:physiology*; D004848:Epithelium / Q000502:physiology; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D011554:Pseudopodia / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
D000199:Actins; D011993:Recombinant Fusion Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020764:cdc42 GTP-Binding Protein