title: Cell ingression and apical shape oscillations during dorsal closure in Drosophila.
abstract: Programmed patterns of gene expression, cell-cell signaling, and cellular forces cause morphogenic movements during dorsal closure. We investigated the apical cell-shape changes that characterize amnioserosa cells during dorsal closure in Drosophila embryos with in vivo imaging of green-fluorescent-protein-labeled DE-cadherin. Time-lapsed, confocal images were assessed with a novel segmentation algorithm, Fourier analysis, and kinematic and dynamical modeling. We found two generic processes, reversible oscillations in apical cross-sectional area and cell ingression characterized by persistent loss of apical area. We quantified a time-dependent, spatially-averaged sum of intracellular and intercellular forces acting on each cell's apical belt of DE-cadherin. We observed that a substantial fraction of amnioserosa cells ingress near the leading edges of lateral epidermis, consistent with the view that ingression can be regulated by leading-edge cells. This is in addition to previously observed ingression processes associated with zipping and apoptosis. Although there is cell-to-cell variability in the maximum rate for decreasing apical area (0.3-9.5 μm(2)/min), the rate for completing ingression is remarkably constant (0.83 cells/min, r(2) > 0.99). We propose that this constant ingression rate contributes to the spatiotemporal regularity of mechanical stress exerted by the amnioserosa on each leading edge during closure.
authors.affiliation: Physics Department, Duke University, Durham, North Carolina, USA.
authors.forename: Adam
authors.initials: A
authors.lastname: Sokolow
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Toyama
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Kiehart
authors.forename: Glenn S
authors.initials: GS
authors.lastname: Edwards
mesh_terms: D000818:Animals; D015820:Cadherins / Q000378:metabolism; D016764:Cell Polarity; D048430:Cell Shape; D004331:Drosophila melanogaster / Q000166:cytology / Q000196:embryology*; D004625:Embryo, Nonmammalian / Q000166:cytology* / Q000378:metabolism; D047108:Embryonic Development; D008954:Models, Biological; D013997:Time Factors
chemical_list: D015820:Cadherins