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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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Differentiation and junctions in scrib epithelia. Eyes consisting of cells homozygous for WT (A), scrib 2 (B), and scrib 4 (C) were produced using the EGUF/hid system. Scrib 4 cells can differentiate into adult eye tissue, whereas scrib 2 cannot. The neuronal differentiation marker Elav (green, phalloidin in red) is severely reduced in scrib 2 (E) but, like WT (D), present in scrib 4 eye discs (F). (G–P) Junctional defects in scrib 4 epithelia. Apicolateral polarization of Cor (green; blue bar shows the full extent of the lateral membrane) in the hindgut (G, WT embryos) is lost in scrib 4 GLC embryos (H). scrib 4 GLC embryos also have a large dorsal hole (J, compare with WT in I). K–P show TEM images of WT (K), scrib 1 (L, note lower magnification), scrib 4 (M) and scrib 5 (N) wing disc cells, with AJs (magenta, A) and SJs (cyan, S) marked. Bars, 0.25 μm. AJs are mislocalized in scrib 2 but found normally in the other mutants; SJs are absent in scrib 2 and most scrib 4 cells, although dispersed septa are rarely found in the latter (P, compare with WT in O).
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fig3: Differentiation and junctions in scrib epithelia. Eyes consisting of cells homozygous for WT (A), scrib 2 (B), and scrib 4 (C) were produced using the EGUF/hid system. Scrib 4 cells can differentiate into adult eye tissue, whereas scrib 2 cannot. The neuronal differentiation marker Elav (green, phalloidin in red) is severely reduced in scrib 2 (E) but, like WT (D), present in scrib 4 eye discs (F). (G–P) Junctional defects in scrib 4 epithelia. Apicolateral polarization of Cor (green; blue bar shows the full extent of the lateral membrane) in the hindgut (G, WT embryos) is lost in scrib 4 GLC embryos (H). scrib 4 GLC embryos also have a large dorsal hole (J, compare with WT in I). K–P show TEM images of WT (K), scrib 1 (L, note lower magnification), scrib 4 (M) and scrib 5 (N) wing disc cells, with AJs (magenta, A) and SJs (cyan, S) marked. Bars, 0.25 μm. AJs are mislocalized in scrib 2 but found normally in the other mutants; SJs are absent in scrib 2 and most scrib 4 cells, although dispersed septa are rarely found in the latter (P, compare with WT in O).

Mentions: Overproliferation of animal cells can be associated with a failure to terminally differentiate and exit from the cell cycle. Therefore, we investigated the ability of scrib cells to differentiate and contribute to adult structures. In genetically mosaic imaginal discs, clones of cells mutant for strong scrib alleles grow slowly and are outcompeted by WT cells. We used the EGUF/hid system (Stowers and Schwarz, 1999) to generate eyes consisting exclusively of scrib mutant cells. Adult eye tissue homozygous for scrib 4 was readily obtained, although it was rough, enlarged and folded (Fig. 3 C). However, animals with eyes homozygous for scrib 1, 2, and 3 never eclose, instead dying as headless pharate adults (Fig. 3 B). Analysis of scrib 2 eye discs reveals severe defects in the expression of the neuronal differentiation marker Elav, as well as a failure to organize ommatidial preclusters; these processes occur normally in scrib 4 eye discs (Fig. 3, E and F). Differentiation capacity in scrib cells therefore correlates with the ability to organize an epithelial monolayer rather than the ability to control all cell proliferation.


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

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

Differentiation and junctions in scrib epithelia. Eyes consisting of cells homozygous for WT (A), scrib 2 (B), and scrib 4 (C) were produced using the EGUF/hid system. Scrib 4 cells can differentiate into adult eye tissue, whereas scrib 2 cannot. The neuronal differentiation marker Elav (green, phalloidin in red) is severely reduced in scrib 2 (E) but, like WT (D), present in scrib 4 eye discs (F). (G–P) Junctional defects in scrib 4 epithelia. Apicolateral polarization of Cor (green; blue bar shows the full extent of the lateral membrane) in the hindgut (G, WT embryos) is lost in scrib 4 GLC embryos (H). scrib 4 GLC embryos also have a large dorsal hole (J, compare with WT in I). K–P show TEM images of WT (K), scrib 1 (L, note lower magnification), scrib 4 (M) and scrib 5 (N) wing disc cells, with AJs (magenta, A) and SJs (cyan, S) marked. Bars, 0.25 μm. AJs are mislocalized in scrib 2 but found normally in the other mutants; SJs are absent in scrib 2 and most scrib 4 cells, although dispersed septa are rarely found in the latter (P, compare with WT in O).
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Related In: Results  -  Collection

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fig3: Differentiation and junctions in scrib epithelia. Eyes consisting of cells homozygous for WT (A), scrib 2 (B), and scrib 4 (C) were produced using the EGUF/hid system. Scrib 4 cells can differentiate into adult eye tissue, whereas scrib 2 cannot. The neuronal differentiation marker Elav (green, phalloidin in red) is severely reduced in scrib 2 (E) but, like WT (D), present in scrib 4 eye discs (F). (G–P) Junctional defects in scrib 4 epithelia. Apicolateral polarization of Cor (green; blue bar shows the full extent of the lateral membrane) in the hindgut (G, WT embryos) is lost in scrib 4 GLC embryos (H). scrib 4 GLC embryos also have a large dorsal hole (J, compare with WT in I). K–P show TEM images of WT (K), scrib 1 (L, note lower magnification), scrib 4 (M) and scrib 5 (N) wing disc cells, with AJs (magenta, A) and SJs (cyan, S) marked. Bars, 0.25 μm. AJs are mislocalized in scrib 2 but found normally in the other mutants; SJs are absent in scrib 2 and most scrib 4 cells, although dispersed septa are rarely found in the latter (P, compare with WT in O).
Mentions: Overproliferation of animal cells can be associated with a failure to terminally differentiate and exit from the cell cycle. Therefore, we investigated the ability of scrib cells to differentiate and contribute to adult structures. In genetically mosaic imaginal discs, clones of cells mutant for strong scrib alleles grow slowly and are outcompeted by WT cells. We used the EGUF/hid system (Stowers and Schwarz, 1999) to generate eyes consisting exclusively of scrib mutant cells. Adult eye tissue homozygous for scrib 4 was readily obtained, although it was rough, enlarged and folded (Fig. 3 C). However, animals with eyes homozygous for scrib 1, 2, and 3 never eclose, instead dying as headless pharate adults (Fig. 3 B). Analysis of scrib 2 eye discs reveals severe defects in the expression of the neuronal differentiation marker Elav, as well as a failure to organize ommatidial preclusters; these processes occur normally in scrib 4 eye discs (Fig. 3, E and F). Differentiation capacity in scrib cells therefore correlates with the ability to organize an epithelial monolayer rather than the ability to control all cell proliferation.

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