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Adherens junction-dependent and -independent steps in the establishment of epithelial cell polarity in Drosophila.

Harris TJ, Peifer M - J. Cell Biol. (2004)

Bottom Line: We found apical accumulation of both Drosophila E-Cadherin (DE-Cad) and the apical cue Bazooka (Baz) as cells first form.Some epithelial structures are retained, however.These structures maintain apical Baz, accumulate apical Crumbs, and organize polarized cytoskeletons, but display abnormal cell morphology and fail to segregate the basolateral cue Discs large from the apical domain.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.

ABSTRACT
Adherens junctions (AJs) are thought to be key landmarks for establishing epithelial cell polarity, but the origin of epithelial polarity in Drosophila remains unclear. Thus, we examined epithelial polarity establishment during early Drosophila development. We found apical accumulation of both Drosophila E-Cadherin (DE-Cad) and the apical cue Bazooka (Baz) as cells first form. Mutant analyses revealed that apical Baz accumulations can be established in the absence of AJs, whereas assembly of apical DE-Cad complexes requires Baz. Thus, Baz acts upstream of AJs during epithelial polarity establishment. During gastrulation the absence of AJs results in widespread cell dissociation and depolarization. Some epithelial structures are retained, however. These structures maintain apical Baz, accumulate apical Crumbs, and organize polarized cytoskeletons, but display abnormal cell morphology and fail to segregate the basolateral cue Discs large from the apical domain. Thus, although epithelial polarity develops in the absence of AJs, AJs play specific roles in maintaining epithelial architecture and segregating basolateral cues.

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Related in: MedlinePlus

Neuronal polarity is retained in armm/z mutants. (A) WT cross section. Neuroblasts divide along the apical–basal axis. Mir (green) and Baz (red) are at opposite poles (one neuroblast outlined). (B) armm/z, surface. Mir (green) and Baz (red) at opposite poles of neuroblasts with no fixed division orientation. (C and D) armm/z. Tubulin (green) shows spindle orientation. (C) Group of dividing dorsal epithelial cells (arrow) next to amnioserosa (outlined). (D) region indicated by arrow in C. Dividing epithelial cells show uniform cortical Baz (red, outlined). Note adjacent epithelial fold (arrowheads). Note one cell dividing perpendicularly to the others (blue arrowhead). (E) WT epithelial cell division (outlined), surface section. Tubulin (green), Baz (red). In this plane Baz is uniform around the cell. Bars: (gray) 25 μm; (white) 5 μm.
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fig10: Neuronal polarity is retained in armm/z mutants. (A) WT cross section. Neuroblasts divide along the apical–basal axis. Mir (green) and Baz (red) are at opposite poles (one neuroblast outlined). (B) armm/z, surface. Mir (green) and Baz (red) at opposite poles of neuroblasts with no fixed division orientation. (C and D) armm/z. Tubulin (green) shows spindle orientation. (C) Group of dividing dorsal epithelial cells (arrow) next to amnioserosa (outlined). (D) region indicated by arrow in C. Dividing epithelial cells show uniform cortical Baz (red, outlined). Note adjacent epithelial fold (arrowheads). Note one cell dividing perpendicularly to the others (blue arrowhead). (E) WT epithelial cell division (outlined), surface section. Tubulin (green), Baz (red). In this plane Baz is uniform around the cell. Bars: (gray) 25 μm; (white) 5 μm.

Mentions: Because Mir and Baz segregate in armm/z mutant epithelia, we investigated whether they also do so in armm/z mutant neuroblasts. Neuroblasts are neuronal progenitor cells. In WT embryos, they delaminate from the ventral neurectoderm, and then divide asymmetrically with Baz at the apical pole, that renews the neuroblast, and Mir at the basal pole, that produces a ganglion mother cell (Fig. 10 A, outlined; Doe and Bowerman, 2001).


Adherens junction-dependent and -independent steps in the establishment of epithelial cell polarity in Drosophila.

Harris TJ, Peifer M - J. Cell Biol. (2004)

Neuronal polarity is retained in armm/z mutants. (A) WT cross section. Neuroblasts divide along the apical–basal axis. Mir (green) and Baz (red) are at opposite poles (one neuroblast outlined). (B) armm/z, surface. Mir (green) and Baz (red) at opposite poles of neuroblasts with no fixed division orientation. (C and D) armm/z. Tubulin (green) shows spindle orientation. (C) Group of dividing dorsal epithelial cells (arrow) next to amnioserosa (outlined). (D) region indicated by arrow in C. Dividing epithelial cells show uniform cortical Baz (red, outlined). Note adjacent epithelial fold (arrowheads). Note one cell dividing perpendicularly to the others (blue arrowhead). (E) WT epithelial cell division (outlined), surface section. Tubulin (green), Baz (red). In this plane Baz is uniform around the cell. Bars: (gray) 25 μm; (white) 5 μm.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172516&req=5

fig10: Neuronal polarity is retained in armm/z mutants. (A) WT cross section. Neuroblasts divide along the apical–basal axis. Mir (green) and Baz (red) are at opposite poles (one neuroblast outlined). (B) armm/z, surface. Mir (green) and Baz (red) at opposite poles of neuroblasts with no fixed division orientation. (C and D) armm/z. Tubulin (green) shows spindle orientation. (C) Group of dividing dorsal epithelial cells (arrow) next to amnioserosa (outlined). (D) region indicated by arrow in C. Dividing epithelial cells show uniform cortical Baz (red, outlined). Note adjacent epithelial fold (arrowheads). Note one cell dividing perpendicularly to the others (blue arrowhead). (E) WT epithelial cell division (outlined), surface section. Tubulin (green), Baz (red). In this plane Baz is uniform around the cell. Bars: (gray) 25 μm; (white) 5 μm.
Mentions: Because Mir and Baz segregate in armm/z mutant epithelia, we investigated whether they also do so in armm/z mutant neuroblasts. Neuroblasts are neuronal progenitor cells. In WT embryos, they delaminate from the ventral neurectoderm, and then divide asymmetrically with Baz at the apical pole, that renews the neuroblast, and Mir at the basal pole, that produces a ganglion mother cell (Fig. 10 A, outlined; Doe and Bowerman, 2001).

Bottom Line: We found apical accumulation of both Drosophila E-Cadherin (DE-Cad) and the apical cue Bazooka (Baz) as cells first form.Some epithelial structures are retained, however.These structures maintain apical Baz, accumulate apical Crumbs, and organize polarized cytoskeletons, but display abnormal cell morphology and fail to segregate the basolateral cue Discs large from the apical domain.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.

ABSTRACT
Adherens junctions (AJs) are thought to be key landmarks for establishing epithelial cell polarity, but the origin of epithelial polarity in Drosophila remains unclear. Thus, we examined epithelial polarity establishment during early Drosophila development. We found apical accumulation of both Drosophila E-Cadherin (DE-Cad) and the apical cue Bazooka (Baz) as cells first form. Mutant analyses revealed that apical Baz accumulations can be established in the absence of AJs, whereas assembly of apical DE-Cad complexes requires Baz. Thus, Baz acts upstream of AJs during epithelial polarity establishment. During gastrulation the absence of AJs results in widespread cell dissociation and depolarization. Some epithelial structures are retained, however. These structures maintain apical Baz, accumulate apical Crumbs, and organize polarized cytoskeletons, but display abnormal cell morphology and fail to segregate the basolateral cue Discs large from the apical domain. Thus, although epithelial polarity develops in the absence of AJs, AJs play specific roles in maintaining epithelial architecture and segregating basolateral cues.

Show MeSH
Related in: MedlinePlus