title: Plasma membrane polarity and compartmentalization are established before cellularization in the fly embryo.
abstract: Patterning in the Drosophila embryo requires local activation and dynamics of proteins in the plasma membrane (PM). We used in vivo fluorescence imaging to characterize the organization and diffusional properties of the PM in the early embryonic syncytium. Before cellularization, the PM is polarized into discrete domains having epithelial-like characteristics. One domain resides above individual nuclei and has apical-like characteristics, while the other domain is lateral to nuclei and contains markers associated with basolateral membranes and junctions. Pulse-chase photoconversion experiments show that molecules can diffuse within each domain but do not exchange between PM regions above adjacent nuclei. Drug-induced F-actin depolymerization disrupted both the apicobasal-like polarity and the diffusion barriers within the syncytial PM. These events correlated with perturbations in the spatial pattern of dorsoventral Toll signaling. We propose that epithelial-like properties and an intact F-actin network compartmentalize the PM and shape morphogen gradients in the syncytial embryo.
authors.affiliation: Cell Biology and Metabolism Program, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA. mavrakis@ibdml.univ-mrs.fr
authors.forename: Manos
authors.initials: M
authors.lastname: Mavrakis
authors.forename: Richa
authors.initials: R
authors.lastname: Rikhy
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lippincott-Schwartz
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D002467:Cell Nucleus / Q000378:metabolism; D016764:Cell Polarity / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000196:embryology* / Q000378:metabolism*; D036681:Fluorescence Recovery After Photobleaching; D019922:GAP-43 Protein / Q000378:metabolism; D015726:Giant Cells / Q000166:cytology / Q000378:metabolism; D008938:Mitosis / Q000502:physiology; D053778:Thiazolidines / Q000378:metabolism
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D029721:Drosophila Proteins; D019922:GAP-43 Protein; D053778:Thiazolidines; C037067:latrunculin A