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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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Dlt is required for the formation of the FE and apical localization of Crb. (A) Wild-type stage 2 follicle stained with phalloidin. Note the prominent accumulation of F-actin at the apical surface of the cells of the FE. (B) Stage 2 and (C) stage 4 follicles containing dltdre1 mutant early clones. The FE shows gaps (between arrowheads) into which germline cells have penetrated. (D) dltMY10 mutant follicle cells, induced before the FE forms, do not form a FE, resulting in follicles with gaps in the FE (arrows). (E–H) Late dlt mutant clones. (E) dltdre1and (F) dltMY10mutant follicle cells have lost Crb. Dlt forms a central cap in the apical membrane in dltdre1 mutant cells (E, arrows). (G and H) dltMY10 mutant follicle cell clones show normal distribution of F-actin (G) and Arm (H).
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Figure 6: Dlt is required for the formation of the FE and apical localization of Crb. (A) Wild-type stage 2 follicle stained with phalloidin. Note the prominent accumulation of F-actin at the apical surface of the cells of the FE. (B) Stage 2 and (C) stage 4 follicles containing dltdre1 mutant early clones. The FE shows gaps (between arrowheads) into which germline cells have penetrated. (D) dltMY10 mutant follicle cells, induced before the FE forms, do not form a FE, resulting in follicles with gaps in the FE (arrows). (E–H) Late dlt mutant clones. (E) dltdre1and (F) dltMY10mutant follicle cells have lost Crb. Dlt forms a central cap in the apical membrane in dltdre1 mutant cells (E, arrows). (G and H) dltMY10 mutant follicle cell clones show normal distribution of F-actin (G) and Arm (H).

Mentions: dltMY10and dltdre1 mutant follicle cells clones, if generated before the formation of the FE, displayed gaps of variable size in the FE similar to those caused by crb mutations (Fig. 6, B–D). As dltdre1 is a protein-positive allele, we were not able to determine whether some dltdre1 mutant follicle cells become part of the FE. In contrast to crb mutant follicle cell clones, we did not find any dltMY10 mutant follicle cells that participate in the formation of the FE in early clones. dltMY10 is a deletion that removes the genes encoding cdc37 and α-spectrin in addition to dlt (Bhat et al. 1999; our unpublished observations). The loss of cdc37 is compensated for by a transgene (see Materials and Methods). Thus, dltMY10 mutant clones lack dlt and α-spectrin, raising the possibility that the observed mutant phenotype is the consequence of a synergistic effect between dlt and α-spectrin mutations, although it was shown that α-spectrin is not required for the formation of the FE (Lee et al. 1997). These findings suggests that Dlt is required, and may be essential for the formation of the FE.


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)

Dlt is required for the formation of the FE and apical localization of Crb. (A) Wild-type stage 2 follicle stained with phalloidin. Note the prominent accumulation of F-actin at the apical surface of the cells of the FE. (B) Stage 2 and (C) stage 4 follicles containing dltdre1 mutant early clones. The FE shows gaps (between arrowheads) into which germline cells have penetrated. (D) dltMY10 mutant follicle cells, induced before the FE forms, do not form a FE, resulting in follicles with gaps in the FE (arrows). (E–H) Late dlt mutant clones. (E) dltdre1and (F) dltMY10mutant follicle cells have lost Crb. Dlt forms a central cap in the apical membrane in dltdre1 mutant cells (E, arrows). (G and H) dltMY10 mutant follicle cell clones show normal distribution of F-actin (G) and Arm (H).
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Related In: Results  -  Collection

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Figure 6: Dlt is required for the formation of the FE and apical localization of Crb. (A) Wild-type stage 2 follicle stained with phalloidin. Note the prominent accumulation of F-actin at the apical surface of the cells of the FE. (B) Stage 2 and (C) stage 4 follicles containing dltdre1 mutant early clones. The FE shows gaps (between arrowheads) into which germline cells have penetrated. (D) dltMY10 mutant follicle cells, induced before the FE forms, do not form a FE, resulting in follicles with gaps in the FE (arrows). (E–H) Late dlt mutant clones. (E) dltdre1and (F) dltMY10mutant follicle cells have lost Crb. Dlt forms a central cap in the apical membrane in dltdre1 mutant cells (E, arrows). (G and H) dltMY10 mutant follicle cell clones show normal distribution of F-actin (G) and Arm (H).
Mentions: dltMY10and dltdre1 mutant follicle cells clones, if generated before the formation of the FE, displayed gaps of variable size in the FE similar to those caused by crb mutations (Fig. 6, B–D). As dltdre1 is a protein-positive allele, we were not able to determine whether some dltdre1 mutant follicle cells become part of the FE. In contrast to crb mutant follicle cell clones, we did not find any dltMY10 mutant follicle cells that participate in the formation of the FE in early clones. dltMY10 is a deletion that removes the genes encoding cdc37 and α-spectrin in addition to dlt (Bhat et al. 1999; our unpublished observations). The loss of cdc37 is compensated for by a transgene (see Materials and Methods). Thus, dltMY10 mutant clones lack dlt and α-spectrin, raising the possibility that the observed mutant phenotype is the consequence of a synergistic effect between dlt and α-spectrin mutations, although it was shown that α-spectrin is not required for the formation of the FE (Lee et al. 1997). These findings suggests that Dlt is required, and may be essential for the formation of the FE.

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