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Abelson kinase regulates epithelial morphogenesis in Drosophila.

Grevengoed EE, Loureiro JJ, Jesse TL, Peifer M - J. Cell Biol. (2001)

Bottom Line: The defects of abl mutants are strongly enhanced by heterozygosity for shotgun, which encodes DE-cadherin.Finally, loss of Abl reduces Arm and alpha-catenin accumulation in adherens junctions, while having little or no effect on other components of the cytoskeleton or cell polarity machinery.We discuss possible models for Abl function during epithelial morphogenesis in light of these data.

View Article: PubMed Central - PubMed

Affiliation: Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA.

ABSTRACT
Activation of the nonreceptor tyrosine kinase Abelson (Abl) contributes to the development of leukemia, but the complex roles of Abl in normal development are not fully understood. Drosophila Abl links neural axon guidance receptors to the cytoskeleton. Here we report a novel role for Drosophila Abl in epithelial cells, where it is critical for morphogenesis. Embryos completely lacking both maternal and zygotic Abl die with defects in several morphogenetic processes requiring cell shape changes and cell migration. We describe the cellular defects that underlie these problems, focusing on dorsal closure as an example. Further, we show that the Abl target Enabled (Ena), a modulator of actin dynamics, is involved with Abl in morphogenesis. We find that Ena localizes to adherens junctions of most epithelial cells, and that it genetically interacts with the adherens junction protein Armadillo (Arm) during morphogenesis. The defects of abl mutants are strongly enhanced by heterozygosity for shotgun, which encodes DE-cadherin. Finally, loss of Abl reduces Arm and alpha-catenin accumulation in adherens junctions, while having little or no effect on other components of the cytoskeleton or cell polarity machinery. We discuss possible models for Abl function during epithelial morphogenesis in light of these data.

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Total levels of Arm and α-catenin are reduced in abl mutants. abl germline mutant females were mated to abl heterozygous males and progeny were picked at the cellular blastoderm stage and aged for the indicated time postblastoderm (PBD). Wild-type embryos (Canton S [CS]) served as a control. Cell extracts were fractionated by SDS-PAGE and immunoblotted with the indicated antibodies. Molecular weight markers are to the right. Bicaudal D (BicD) or Peanut (Pnut) are loading controls. Each vertical set of samples represents sequential reprobing of the same blot. (A and B) Stage 11/12 embryos (6 h postblastoderm). (C) Stage 13/14 embryos (9 h postblastoderm).
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fig10: Total levels of Arm and α-catenin are reduced in abl mutants. abl germline mutant females were mated to abl heterozygous males and progeny were picked at the cellular blastoderm stage and aged for the indicated time postblastoderm (PBD). Wild-type embryos (Canton S [CS]) served as a control. Cell extracts were fractionated by SDS-PAGE and immunoblotted with the indicated antibodies. Molecular weight markers are to the right. Bicaudal D (BicD) or Peanut (Pnut) are loading controls. Each vertical set of samples represents sequential reprobing of the same blot. (A and B) Stage 11/12 embryos (6 h postblastoderm). (C) Stage 13/14 embryos (9 h postblastoderm).

Mentions: To complement these immunofluorescence assays, we examined total protein levels of Arm and other proteins in the progeny of abl4 germline mutant females crossed to abl heterozygous males. Half of these embryos are ablMZ and the other half are zygotically rescued. To ensure that embryos were similarly aged and to remove unfertilized eggs from the samples, we selected living embryos at the cellular blastoderm stage and then let them develop for given amounts of time. Total levels of Arm protein are significantly reduced throughout development compared with wild-type (Fig. 10, A–C). Similar reductions in Arm protein were observed in abl1 (unpublished data). In contrast to Arm, the levels of two unrelated control proteins, Pnut and BicD, were unaffected by loss of Abl function (Fig. 10, A–C). We next examined the levels of other adherens junction proteins. Reduction in Abl function also led to reduction in α-catenin protein levels (Fig. 10 A). In contrast, levels of DE-cadherin are not altered in abl mutants (Fig. 10, A–C). We then assessed whether these effects were specific for adherens junction proteins, by examining the levels of other markers of cell polarity or the cytoskeleton. We saw either subtle reduction or no effect of abl mutations on the levels of actin, the septate junction protein Coracle, and the apical marker Crumbs (Fig. 10, B and C).


Abelson kinase regulates epithelial morphogenesis in Drosophila.

Grevengoed EE, Loureiro JJ, Jesse TL, Peifer M - J. Cell Biol. (2001)

Total levels of Arm and α-catenin are reduced in abl mutants. abl germline mutant females were mated to abl heterozygous males and progeny were picked at the cellular blastoderm stage and aged for the indicated time postblastoderm (PBD). Wild-type embryos (Canton S [CS]) served as a control. Cell extracts were fractionated by SDS-PAGE and immunoblotted with the indicated antibodies. Molecular weight markers are to the right. Bicaudal D (BicD) or Peanut (Pnut) are loading controls. Each vertical set of samples represents sequential reprobing of the same blot. (A and B) Stage 11/12 embryos (6 h postblastoderm). (C) Stage 13/14 embryos (9 h postblastoderm).
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Related In: Results  -  Collection

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fig10: Total levels of Arm and α-catenin are reduced in abl mutants. abl germline mutant females were mated to abl heterozygous males and progeny were picked at the cellular blastoderm stage and aged for the indicated time postblastoderm (PBD). Wild-type embryos (Canton S [CS]) served as a control. Cell extracts were fractionated by SDS-PAGE and immunoblotted with the indicated antibodies. Molecular weight markers are to the right. Bicaudal D (BicD) or Peanut (Pnut) are loading controls. Each vertical set of samples represents sequential reprobing of the same blot. (A and B) Stage 11/12 embryos (6 h postblastoderm). (C) Stage 13/14 embryos (9 h postblastoderm).
Mentions: To complement these immunofluorescence assays, we examined total protein levels of Arm and other proteins in the progeny of abl4 germline mutant females crossed to abl heterozygous males. Half of these embryos are ablMZ and the other half are zygotically rescued. To ensure that embryos were similarly aged and to remove unfertilized eggs from the samples, we selected living embryos at the cellular blastoderm stage and then let them develop for given amounts of time. Total levels of Arm protein are significantly reduced throughout development compared with wild-type (Fig. 10, A–C). Similar reductions in Arm protein were observed in abl1 (unpublished data). In contrast to Arm, the levels of two unrelated control proteins, Pnut and BicD, were unaffected by loss of Abl function (Fig. 10, A–C). We next examined the levels of other adherens junction proteins. Reduction in Abl function also led to reduction in α-catenin protein levels (Fig. 10 A). In contrast, levels of DE-cadherin are not altered in abl mutants (Fig. 10, A–C). We then assessed whether these effects were specific for adherens junction proteins, by examining the levels of other markers of cell polarity or the cytoskeleton. We saw either subtle reduction or no effect of abl mutations on the levels of actin, the septate junction protein Coracle, and the apical marker Crumbs (Fig. 10, B and C).

Bottom Line: The defects of abl mutants are strongly enhanced by heterozygosity for shotgun, which encodes DE-cadherin.Finally, loss of Abl reduces Arm and alpha-catenin accumulation in adherens junctions, while having little or no effect on other components of the cytoskeleton or cell polarity machinery.We discuss possible models for Abl function during epithelial morphogenesis in light of these data.

View Article: PubMed Central - PubMed

Affiliation: Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA.

ABSTRACT
Activation of the nonreceptor tyrosine kinase Abelson (Abl) contributes to the development of leukemia, but the complex roles of Abl in normal development are not fully understood. Drosophila Abl links neural axon guidance receptors to the cytoskeleton. Here we report a novel role for Drosophila Abl in epithelial cells, where it is critical for morphogenesis. Embryos completely lacking both maternal and zygotic Abl die with defects in several morphogenetic processes requiring cell shape changes and cell migration. We describe the cellular defects that underlie these problems, focusing on dorsal closure as an example. Further, we show that the Abl target Enabled (Ena), a modulator of actin dynamics, is involved with Abl in morphogenesis. We find that Ena localizes to adherens junctions of most epithelial cells, and that it genetically interacts with the adherens junction protein Armadillo (Arm) during morphogenesis. The defects of abl mutants are strongly enhanced by heterozygosity for shotgun, which encodes DE-cadherin. Finally, loss of Abl reduces Arm and alpha-catenin accumulation in adherens junctions, while having little or no effect on other components of the cytoskeleton or cell polarity machinery. We discuss possible models for Abl function during epithelial morphogenesis in light of these data.

Show MeSH
Related in: MedlinePlus