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Domains controlling cell polarity and proliferation in the Drosophila tumor suppressor Scribble.

Zeitler J, Hsu CP, Dionne H, Bilder D - J. Cell Biol. (2004)

Bottom Line: The PDZ domains, which recruit the LRR to the junctional complex, are dispensable for overall epithelial organization.PDZ domain absence leads to mild polarity defects accompanied by moderate overproliferation, but the PDZ domains alone are insufficient to provide any Scrib function in mutant discs.We suggest a model in which Scrib, via the activity of the LRR, governs proliferation primarily by regulating apicobasal polarity.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA 94720, USA.

ABSTRACT
Cell polarity and cell proliferation can be coupled in animal tissues, but how they are coupled is not understood. In Drosophila imaginal discs, loss of the neoplastic tumor suppressor gene scribble (scrib), which encodes a multidomain scaffolding protein, disrupts epithelial organization and also causes unchecked proliferation. Using an allelic series of mutations along with rescuing transgenes, we have identified domain requirements for polarity, proliferation control, and other Scrib functions. The leucine-rich repeats (LRR) tether Scrib to the plasma membrane, are both necessary and sufficient to organize a polarized epithelial monolayer, and are required for all proliferation control. The PDZ domains, which recruit the LRR to the junctional complex, are dispensable for overall epithelial organization. PDZ domain absence leads to mild polarity defects accompanied by moderate overproliferation, but the PDZ domains alone are insufficient to provide any Scrib function in mutant discs. We suggest a model in which Scrib, via the activity of the LRR, governs proliferation primarily by regulating apicobasal polarity.

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Epithelial architecture of scrib wing discs. Confocal images displaying multiple folds in the disc epithelium. WT disc cells (A) show apicobasal (a and b) polarity, revealed by apically enriched filamentous actin (phalloidin, red), and monolayered cellular organization, revealed by nuclear staining (DAPI, blue). Apical polarity and monolayered organization are absent in scrib 2 (B) and 3 (C) discs, but present in scrib 4 (D), 5 (E), and 7 (F) discs.
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fig1: Epithelial architecture of scrib wing discs. Confocal images displaying multiple folds in the disc epithelium. WT disc cells (A) show apicobasal (a and b) polarity, revealed by apically enriched filamentous actin (phalloidin, red), and monolayered cellular organization, revealed by nuclear staining (DAPI, blue). Apical polarity and monolayered organization are absent in scrib 2 (B) and 3 (C) discs, but present in scrib 4 (D), 5 (E), and 7 (F) discs.

Mentions: To test the functions that each mutant Scrib protein is capable of providing, we analyzed the phenotypes of wing imaginal discs from hemizygous larvae. The wing disc includes a monolayer of highly elongated epithelial cells that attains a consistent size and organization. We first assayed epithelial architecture using rhodamine-phalloidin, which binds to apically enriched filamentous actin (Fig. 1 A). In discs from the allele scrib 2, phalloidin staining reveals uniform actin localization throughout the cortex, and the cells themselves are round rather than elongated (Fig. 1 B). Moreover, these cells have a multilayered rather than monolayered organization, forming a solid spherical mass rather than a flat disc. These phenotypes are identical to those of scrib 1 (Bilder et al., 2000) as well as scrib 3 (Fig. 1 C). By contrast, discs from scrib 4, 5, 6, and 7 larvae contain cells arranged in epithelial monolayers, maintaining the distinctive folded structure of the tissue (Fig. 1, D–F). Interestingly, epithelial cells from scrib 4 and 5 discs display altered cell shapes, with scrib 4 in particular showing cuboidal rather than columnar morphology. Nevertheless, apical accumulation of actin is readily seen. These results demonstrate that the proteins produced by scrib 4, 5, 6, and 7 can provide polarity function in imaginal discs, whereas those produced by scrib 1, 2, and 3 cannot.


Domains controlling cell polarity and proliferation in the Drosophila tumor suppressor Scribble.

Zeitler J, Hsu CP, Dionne H, Bilder D - J. Cell Biol. (2004)

Epithelial architecture of scrib wing discs. Confocal images displaying multiple folds in the disc epithelium. WT disc cells (A) show apicobasal (a and b) polarity, revealed by apically enriched filamentous actin (phalloidin, red), and monolayered cellular organization, revealed by nuclear staining (DAPI, blue). Apical polarity and monolayered organization are absent in scrib 2 (B) and 3 (C) discs, but present in scrib 4 (D), 5 (E), and 7 (F) discs.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172630&req=5

fig1: Epithelial architecture of scrib wing discs. Confocal images displaying multiple folds in the disc epithelium. WT disc cells (A) show apicobasal (a and b) polarity, revealed by apically enriched filamentous actin (phalloidin, red), and monolayered cellular organization, revealed by nuclear staining (DAPI, blue). Apical polarity and monolayered organization are absent in scrib 2 (B) and 3 (C) discs, but present in scrib 4 (D), 5 (E), and 7 (F) discs.
Mentions: To test the functions that each mutant Scrib protein is capable of providing, we analyzed the phenotypes of wing imaginal discs from hemizygous larvae. The wing disc includes a monolayer of highly elongated epithelial cells that attains a consistent size and organization. We first assayed epithelial architecture using rhodamine-phalloidin, which binds to apically enriched filamentous actin (Fig. 1 A). In discs from the allele scrib 2, phalloidin staining reveals uniform actin localization throughout the cortex, and the cells themselves are round rather than elongated (Fig. 1 B). Moreover, these cells have a multilayered rather than monolayered organization, forming a solid spherical mass rather than a flat disc. These phenotypes are identical to those of scrib 1 (Bilder et al., 2000) as well as scrib 3 (Fig. 1 C). By contrast, discs from scrib 4, 5, 6, and 7 larvae contain cells arranged in epithelial monolayers, maintaining the distinctive folded structure of the tissue (Fig. 1, D–F). Interestingly, epithelial cells from scrib 4 and 5 discs display altered cell shapes, with scrib 4 in particular showing cuboidal rather than columnar morphology. Nevertheless, apical accumulation of actin is readily seen. These results demonstrate that the proteins produced by scrib 4, 5, 6, and 7 can provide polarity function in imaginal discs, whereas those produced by scrib 1, 2, and 3 cannot.

Bottom Line: The PDZ domains, which recruit the LRR to the junctional complex, are dispensable for overall epithelial organization.PDZ domain absence leads to mild polarity defects accompanied by moderate overproliferation, but the PDZ domains alone are insufficient to provide any Scrib function in mutant discs.We suggest a model in which Scrib, via the activity of the LRR, governs proliferation primarily by regulating apicobasal polarity.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA 94720, USA.

ABSTRACT
Cell polarity and cell proliferation can be coupled in animal tissues, but how they are coupled is not understood. In Drosophila imaginal discs, loss of the neoplastic tumor suppressor gene scribble (scrib), which encodes a multidomain scaffolding protein, disrupts epithelial organization and also causes unchecked proliferation. Using an allelic series of mutations along with rescuing transgenes, we have identified domain requirements for polarity, proliferation control, and other Scrib functions. The leucine-rich repeats (LRR) tether Scrib to the plasma membrane, are both necessary and sufficient to organize a polarized epithelial monolayer, and are required for all proliferation control. The PDZ domains, which recruit the LRR to the junctional complex, are dispensable for overall epithelial organization. PDZ domain absence leads to mild polarity defects accompanied by moderate overproliferation, but the PDZ domains alone are insufficient to provide any Scrib function in mutant discs. We suggest a model in which Scrib, via the activity of the LRR, governs proliferation primarily by regulating apicobasal polarity.

Show MeSH
Related in: MedlinePlus