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Apical, lateral, and basal polarization cues contribute to the development of the follicular epithelium during Drosophila oogenesis.

Tanentzapf G, Smith C, McGlade J, Tepass U - J. Cell Biol. (2000)

Bottom Line: Loss of cadherin-based adherens junctions caused by armadillo (beta-catenin) mutations results in a disruption of the lateral spectrin and actin cytoskeleton.Also Crb and the apical spectrin cytoskeleton are lost from armadillo mutant follicle cells.Together with previous data showing that Crb is required for the formation of a zonula adherens, these findings indicate a mutual dependency of apical and lateral polarization mechanisms.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Toronto, Toronto, Ontario, Canada M5S 3G5.

ABSTRACT
Analysis of the mechanisms that control epithelial polarization has revealed that cues for polarization are mediated by transmembrane proteins that operate at the apical, lateral, or basal surface of epithelial cells. Whereas for any given epithelial cell type only one or two polarization systems have been identified to date, we report here that the follicular epithelium in Drosophila ovaries uses three different polarization mechanisms, each operating at one of the three main epithelial surface domains. The follicular epithelium arises through a mesenchymal-epithelial transition. Contact with the basement membrane provides an initial polarization cue that leads to the formation of a basal membrane domain. Moreover, we use mosaic analysis to show that Crumbs (Crb) is required for the formation and maintenance of the follicular epithelium. Crb localizes to the apical membrane of follicle cells that is in contact with germline cells. Contact to the germline is required for the accumulation of Crb in follicle cells. Discs Lost (Dlt), a cytoplasmic PDZ domain protein that was shown to interact with the cytoplasmic tail of Crb, overlaps precisely in its distribution with Crb, as shown by immunoelectron microscopy. Crb localization depends on Dlt, whereas Dlt uses Crb-dependent and -independent mechanisms for apical targeting. Finally, we show that the cadherin-catenin complex is not required for the formation of the follicular epithelium, but only for its maintenance. Loss of cadherin-based adherens junctions caused by armadillo (beta-catenin) mutations results in a disruption of the lateral spectrin and actin cytoskeleton. Also Crb and the apical spectrin cytoskeleton are lost from armadillo mutant follicle cells. Together with previous data showing that Crb is required for the formation of a zonula adherens, these findings indicate a mutual dependency of apical and lateral polarization mechanisms.

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Follicle cells in agametic ovaries show partial polarization. Distribution of epithelial polarity markers in agametic ovaries of flies derived from oskar301 homozygous mutant females (Lehmann and Nusslein-Volhard 1986). (A) The anterior half of a oskar301 mutant ovary double labeled for βPS-integrin (red) and DE-cadherin (green). The arrows point to individual ovarioles in which the intense DE-cadherin labeling highlights the follicle cells. (B) As in wild type (data not shown), βPS-integrin localizes to the basal membrane of follicle cells in agametic ovaries (arrowhead), whereas DE-cadherin is largely excluded from the basal membrane and accumulates in the remaining cell surface. (C) Fasciclin III is excluded from the basal membrane (arrowheads). (D) The apical marker βHeavy-spectrin is excluded from the basal membrane (arrowheads) as well. Apical and lateral markers show an overlapping distribution and concentrate at the center of the follicle cell column at the cell pole that opposes the basal cell surface. (E) An anterior half of an oskar301 mutant ovary (compare with A) labeled for Crb. Crb is not expressed in the follicle cells of oskar301 mutant ovaries.
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Figure 4: Follicle cells in agametic ovaries show partial polarization. Distribution of epithelial polarity markers in agametic ovaries of flies derived from oskar301 homozygous mutant females (Lehmann and Nusslein-Volhard 1986). (A) The anterior half of a oskar301 mutant ovary double labeled for βPS-integrin (red) and DE-cadherin (green). The arrows point to individual ovarioles in which the intense DE-cadherin labeling highlights the follicle cells. (B) As in wild type (data not shown), βPS-integrin localizes to the basal membrane of follicle cells in agametic ovaries (arrowhead), whereas DE-cadherin is largely excluded from the basal membrane and accumulates in the remaining cell surface. (C) Fasciclin III is excluded from the basal membrane (arrowheads). (D) The apical marker βHeavy-spectrin is excluded from the basal membrane (arrowheads) as well. Apical and lateral markers show an overlapping distribution and concentrate at the center of the follicle cell column at the cell pole that opposes the basal cell surface. (E) An anterior half of an oskar301 mutant ovary (compare with A) labeled for Crb. Crb is not expressed in the follicle cells of oskar301 mutant ovaries.

Mentions: The follicle cells are generated by two stem cells that are located in the middle of the germarium at the boundary of region 2a and 2b (Margolis and Spradling 1995). Offspring of these stem cells establish contact with the basement membrane that surrounds the germarium and the follicles (King 1970; Fig. 1). Analysis of agametic ovaries has shown that the contact between follicle cells and germline cells is required for the formation of the FE. Follicle cells continue to proliferate in agametic ovaries and form a column that is two to three cells wide (Margolis and Spradling 1995; Goode et al. 1996b). To determine whether, and to what extent, contact between follicle cells and the basement membrane contributes to the polarization of the FE, we examined follicle cells in agametic ovaries (Fig. 4). In agametic ovaries, βPS-integrin localizes to the basal membrane of follicle cells as in wild type (Fig. 4A and Fig. B). Markers that normally localize to the lateral membrane [Fasciclin III (Fig. 4 C), and DN-cadherin (data not shown)], to the lateral and apical membranes [DE-cadherin (Fig. 4A and Fig. B), Armadillo (data not shown)], or to the apical membrane (βHeavy-spectrin, Fig. 4 D) are excluded from the basal cell pole. Apical and lateral markers show an overlapping distribution at the non-basal cell surface, but are concentrated at the cell pole that opposes the basal membrane. These findings suggest that contact to the basement membrane causes a partial polarization of follicle cells. The basal membrane is established and an asymmetric distribution of apical and lateral markers is observed, but the apical and lateral membrane domains are not clearly demarcated. As the follicle cells express the cadherin–catenin complex constitutively (Peifer et al. 1993; Oda et al. 1997; Godt and Tepass 1998; Niewiadomska et al. 1999; this work), it appears that basal polarization cues together with the activity of the cadherin–catenin complex are insufficient to fully polarize follicle cells.


Apical, lateral, and basal polarization cues contribute to the development of the follicular epithelium during Drosophila oogenesis.

Tanentzapf G, Smith C, McGlade J, Tepass U - J. Cell Biol. (2000)

Follicle cells in agametic ovaries show partial polarization. Distribution of epithelial polarity markers in agametic ovaries of flies derived from oskar301 homozygous mutant females (Lehmann and Nusslein-Volhard 1986). (A) The anterior half of a oskar301 mutant ovary double labeled for βPS-integrin (red) and DE-cadherin (green). The arrows point to individual ovarioles in which the intense DE-cadherin labeling highlights the follicle cells. (B) As in wild type (data not shown), βPS-integrin localizes to the basal membrane of follicle cells in agametic ovaries (arrowhead), whereas DE-cadherin is largely excluded from the basal membrane and accumulates in the remaining cell surface. (C) Fasciclin III is excluded from the basal membrane (arrowheads). (D) The apical marker βHeavy-spectrin is excluded from the basal membrane (arrowheads) as well. Apical and lateral markers show an overlapping distribution and concentrate at the center of the follicle cell column at the cell pole that opposes the basal cell surface. (E) An anterior half of an oskar301 mutant ovary (compare with A) labeled for Crb. Crb is not expressed in the follicle cells of oskar301 mutant ovaries.
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Related In: Results  -  Collection

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Figure 4: Follicle cells in agametic ovaries show partial polarization. Distribution of epithelial polarity markers in agametic ovaries of flies derived from oskar301 homozygous mutant females (Lehmann and Nusslein-Volhard 1986). (A) The anterior half of a oskar301 mutant ovary double labeled for βPS-integrin (red) and DE-cadherin (green). The arrows point to individual ovarioles in which the intense DE-cadherin labeling highlights the follicle cells. (B) As in wild type (data not shown), βPS-integrin localizes to the basal membrane of follicle cells in agametic ovaries (arrowhead), whereas DE-cadherin is largely excluded from the basal membrane and accumulates in the remaining cell surface. (C) Fasciclin III is excluded from the basal membrane (arrowheads). (D) The apical marker βHeavy-spectrin is excluded from the basal membrane (arrowheads) as well. Apical and lateral markers show an overlapping distribution and concentrate at the center of the follicle cell column at the cell pole that opposes the basal cell surface. (E) An anterior half of an oskar301 mutant ovary (compare with A) labeled for Crb. Crb is not expressed in the follicle cells of oskar301 mutant ovaries.
Mentions: The follicle cells are generated by two stem cells that are located in the middle of the germarium at the boundary of region 2a and 2b (Margolis and Spradling 1995). Offspring of these stem cells establish contact with the basement membrane that surrounds the germarium and the follicles (King 1970; Fig. 1). Analysis of agametic ovaries has shown that the contact between follicle cells and germline cells is required for the formation of the FE. Follicle cells continue to proliferate in agametic ovaries and form a column that is two to three cells wide (Margolis and Spradling 1995; Goode et al. 1996b). To determine whether, and to what extent, contact between follicle cells and the basement membrane contributes to the polarization of the FE, we examined follicle cells in agametic ovaries (Fig. 4). In agametic ovaries, βPS-integrin localizes to the basal membrane of follicle cells as in wild type (Fig. 4A and Fig. B). Markers that normally localize to the lateral membrane [Fasciclin III (Fig. 4 C), and DN-cadherin (data not shown)], to the lateral and apical membranes [DE-cadherin (Fig. 4A and Fig. B), Armadillo (data not shown)], or to the apical membrane (βHeavy-spectrin, Fig. 4 D) are excluded from the basal cell pole. Apical and lateral markers show an overlapping distribution at the non-basal cell surface, but are concentrated at the cell pole that opposes the basal membrane. These findings suggest that contact to the basement membrane causes a partial polarization of follicle cells. The basal membrane is established and an asymmetric distribution of apical and lateral markers is observed, but the apical and lateral membrane domains are not clearly demarcated. As the follicle cells express the cadherin–catenin complex constitutively (Peifer et al. 1993; Oda et al. 1997; Godt and Tepass 1998; Niewiadomska et al. 1999; this work), it appears that basal polarization cues together with the activity of the cadherin–catenin complex are insufficient to fully polarize follicle cells.

Bottom Line: Loss of cadherin-based adherens junctions caused by armadillo (beta-catenin) mutations results in a disruption of the lateral spectrin and actin cytoskeleton.Also Crb and the apical spectrin cytoskeleton are lost from armadillo mutant follicle cells.Together with previous data showing that Crb is required for the formation of a zonula adherens, these findings indicate a mutual dependency of apical and lateral polarization mechanisms.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Toronto, Toronto, Ontario, Canada M5S 3G5.

ABSTRACT
Analysis of the mechanisms that control epithelial polarization has revealed that cues for polarization are mediated by transmembrane proteins that operate at the apical, lateral, or basal surface of epithelial cells. Whereas for any given epithelial cell type only one or two polarization systems have been identified to date, we report here that the follicular epithelium in Drosophila ovaries uses three different polarization mechanisms, each operating at one of the three main epithelial surface domains. The follicular epithelium arises through a mesenchymal-epithelial transition. Contact with the basement membrane provides an initial polarization cue that leads to the formation of a basal membrane domain. Moreover, we use mosaic analysis to show that Crumbs (Crb) is required for the formation and maintenance of the follicular epithelium. Crb localizes to the apical membrane of follicle cells that is in contact with germline cells. Contact to the germline is required for the accumulation of Crb in follicle cells. Discs Lost (Dlt), a cytoplasmic PDZ domain protein that was shown to interact with the cytoplasmic tail of Crb, overlaps precisely in its distribution with Crb, as shown by immunoelectron microscopy. Crb localization depends on Dlt, whereas Dlt uses Crb-dependent and -independent mechanisms for apical targeting. Finally, we show that the cadherin-catenin complex is not required for the formation of the follicular epithelium, but only for its maintenance. Loss of cadherin-based adherens junctions caused by armadillo (beta-catenin) mutations results in a disruption of the lateral spectrin and actin cytoskeleton. Also Crb and the apical spectrin cytoskeleton are lost from armadillo mutant follicle cells. Together with previous data showing that Crb is required for the formation of a zonula adherens, these findings indicate a mutual dependency of apical and lateral polarization mechanisms.

Show MeSH