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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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Mir is displaced from the apical domain in armm/z mutants. (A) Cellularizing WT, cross section. Note Mir (green) along full furrow length. Baz (red). (B) WT stage 9 neurectoderm, cross section. Mir (green) and apical Baz (red) segregate. (C–E) armm/z. Mir (green) is displaced from apical domain defined by Baz (red) in neurectoderm rosettes (C, arrow) and epithelial folds (D, arrow). (E) Neurectoderm rosette. Note Dlg (red) in the apical domain (arrowhead), and the Mir (green) displacement (arrow). Bars, 5 μm.
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fig9: Mir is displaced from the apical domain in armm/z mutants. (A) Cellularizing WT, cross section. Note Mir (green) along full furrow length. Baz (red). (B) WT stage 9 neurectoderm, cross section. Mir (green) and apical Baz (red) segregate. (C–E) armm/z. Mir (green) is displaced from apical domain defined by Baz (red) in neurectoderm rosettes (C, arrow) and epithelial folds (D, arrow). (E) Neurectoderm rosette. Note Dlg (red) in the apical domain (arrowhead), and the Mir (green) displacement (arrow). Bars, 5 μm.

Mentions: To investigate whether AJs play a general role in displacing basolateral cues, we analyzed Mir. Mir localizes basally in dividing neuroblasts (Doe and Bowerman, 2001; see next section). We also found Mir along the full length of WT cellularization furrows, overlapping apical Baz (Fig. 9 A). However, after gastrulation, Mir segregates from Baz to the basolateral domain of neurectoderm cells (Fig. 9 B). Thus, Mir and Dlg show similar redistributions during these stages.


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

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

Mir is displaced from the apical domain in armm/z mutants. (A) Cellularizing WT, cross section. Note Mir (green) along full furrow length. Baz (red). (B) WT stage 9 neurectoderm, cross section. Mir (green) and apical Baz (red) segregate. (C–E) armm/z. Mir (green) is displaced from apical domain defined by Baz (red) in neurectoderm rosettes (C, arrow) and epithelial folds (D, arrow). (E) Neurectoderm rosette. Note Dlg (red) in the apical domain (arrowhead), and the Mir (green) displacement (arrow). Bars, 5 μm.
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Related In: Results  -  Collection

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fig9: Mir is displaced from the apical domain in armm/z mutants. (A) Cellularizing WT, cross section. Note Mir (green) along full furrow length. Baz (red). (B) WT stage 9 neurectoderm, cross section. Mir (green) and apical Baz (red) segregate. (C–E) armm/z. Mir (green) is displaced from apical domain defined by Baz (red) in neurectoderm rosettes (C, arrow) and epithelial folds (D, arrow). (E) Neurectoderm rosette. Note Dlg (red) in the apical domain (arrowhead), and the Mir (green) displacement (arrow). Bars, 5 μm.
Mentions: To investigate whether AJs play a general role in displacing basolateral cues, we analyzed Mir. Mir localizes basally in dividing neuroblasts (Doe and Bowerman, 2001; see next section). We also found Mir along the full length of WT cellularization furrows, overlapping apical Baz (Fig. 9 A). However, after gastrulation, Mir segregates from Baz to the basolateral domain of neurectoderm cells (Fig. 9 B). Thus, Mir and Dlg show similar redistributions during these stages.

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