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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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AJs, Crb, and the displacement of Dlg. (A) Early WT PMGI. Crb (green; arrowhead) accumulates in apical domain bordered by Baz (red, arrow). (B) Early armm/z fold (outlined). Crb (green) is enriched in apical domain (arrowheads) bordered by Baz (red, arrows). (C) armm/z rosette. Crb (green, arrowhead) remains apical to Baz (red, arrow). (D) WT, stage 10. DE-Cad in continuous ectodermal belt junctions. (E) crb2, stage 10. DE-Cad in fragmented AJs. (F) crb2, stage 10. Dlg (green) is depleted from plasma membrane domains (arrowheads) containing AJ fragments (red) and Baz (gray). Bars, 5 μm.
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fig7: AJs, Crb, and the displacement of Dlg. (A) Early WT PMGI. Crb (green; arrowhead) accumulates in apical domain bordered by Baz (red, arrow). (B) Early armm/z fold (outlined). Crb (green) is enriched in apical domain (arrowheads) bordered by Baz (red, arrows). (C) armm/z rosette. Crb (green, arrowhead) remains apical to Baz (red, arrow). (D) WT, stage 10. DE-Cad in continuous ectodermal belt junctions. (E) crb2, stage 10. DE-Cad in fragmented AJs. (F) crb2, stage 10. Dlg (green) is depleted from plasma membrane domains (arrowheads) containing AJ fragments (red) and Baz (gray). Bars, 5 μm.

Mentions: What accounts for the failure to displace Dlg from the apical domain in armm/z mutant epithelia? The apical cue Crb antagonizes Dlg (Bilder et al., 2003; Tanentzapf and Tepass, 2003). Crb is first expressed during gastrulation (Tepass et al., 1990), and Baz is required to recruit Crb to the apical domain (Bilder et al., 2003), but the role of AJs in this recruitment is unknown. In the early armm/z mutant folds and later rosettes, we found that Crb is enriched along the apical domain (Fig. 7, B and C, arrowheads) defined by Baz (Fig. 7, B and C, arrows), similar to WT (Fig. 7 A). Thus, Baz appears to recruit Crb to the apical domain in the absence of AJ function.


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

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

AJs, Crb, and the displacement of Dlg. (A) Early WT PMGI. Crb (green; arrowhead) accumulates in apical domain bordered by Baz (red, arrow). (B) Early armm/z fold (outlined). Crb (green) is enriched in apical domain (arrowheads) bordered by Baz (red, arrows). (C) armm/z rosette. Crb (green, arrowhead) remains apical to Baz (red, arrow). (D) WT, stage 10. DE-Cad in continuous ectodermal belt junctions. (E) crb2, stage 10. DE-Cad in fragmented AJs. (F) crb2, stage 10. Dlg (green) is depleted from plasma membrane domains (arrowheads) containing AJ fragments (red) and Baz (gray). Bars, 5 μm.
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Related In: Results  -  Collection

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fig7: AJs, Crb, and the displacement of Dlg. (A) Early WT PMGI. Crb (green; arrowhead) accumulates in apical domain bordered by Baz (red, arrow). (B) Early armm/z fold (outlined). Crb (green) is enriched in apical domain (arrowheads) bordered by Baz (red, arrows). (C) armm/z rosette. Crb (green, arrowhead) remains apical to Baz (red, arrow). (D) WT, stage 10. DE-Cad in continuous ectodermal belt junctions. (E) crb2, stage 10. DE-Cad in fragmented AJs. (F) crb2, stage 10. Dlg (green) is depleted from plasma membrane domains (arrowheads) containing AJ fragments (red) and Baz (gray). Bars, 5 μm.
Mentions: What accounts for the failure to displace Dlg from the apical domain in armm/z mutant epithelia? The apical cue Crb antagonizes Dlg (Bilder et al., 2003; Tanentzapf and Tepass, 2003). Crb is first expressed during gastrulation (Tepass et al., 1990), and Baz is required to recruit Crb to the apical domain (Bilder et al., 2003), but the role of AJs in this recruitment is unknown. In the early armm/z mutant folds and later rosettes, we found that Crb is enriched along the apical domain (Fig. 7, B and C, arrowheads) defined by Baz (Fig. 7, B and C, arrows), similar to WT (Fig. 7 A). Thus, Baz appears to recruit Crb to the apical domain in the absence of AJ function.

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