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The Drosophila sterile-20 kinase slik controls cell proliferation and apoptosis during imaginal disc development.

Hipfner DR, Cohen SM - PLoS Biol. (2003)

Bottom Line: Tumor-like tissue overgrowth results when apoptosis is prevented.Activation of Raf can compensate for the lack of Slik and support cell survival, but activation of ERK cannot.We suggest that Slik mediates growth and survival cues to promote cell proliferation and control cell survival during Drosophila development.

View Article: PubMed Central - PubMed

Affiliation: European Molecular Biology Laboratory, Heidelberg, Germany.

ABSTRACT
Cell proliferation and programmed cell death are closely controlled during animal development. Proliferative stimuli generally also induce apoptosis, and anti-apoptotic factors are required to allow net cell proliferation. Genetic studies in Drosophila have led to identification of a number of genes that control both processes, providing new insights into the mechanisms that coordinate cell growth, proliferation, and death during development and that fail to do so in diseases of cell proliferation. We present evidence that the Drosophila Sterile-20 kinase Slik promotes cell proliferation and controls cell survival. At normal levels, Slik provides survival cues that prevent apoptosis. Cells deprived of Slik activity can grow, divide, and differentiate, but have an intrinsic survival defect and undergo apoptosis even under conditions in which they are not competing with normal cells for survival cues. Like some oncogenes, excess Slik activity stimulates cell proliferation, but this is compensated for by increased cell death. Tumor-like tissue overgrowth results when apoptosis is prevented. We present evidence that Slik acts via Raf, but not via the canonical ERK pathway. Activation of Raf can compensate for the lack of Slik and support cell survival, but activation of ERK cannot. We suggest that Slik mediates growth and survival cues to promote cell proliferation and control cell survival during Drosophila development.

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Growth Defects in slik Mutants(A) Heterozygous slik1/+ control and homozygous slik1 mutant larvae after 5 d of growth under uncrowded conditions.(B) Growth and survival characteristics of slik1/+ control and homozygous slik1 mutant larvae. The percentage of animals at each developmental stage on the indicated days are shown by the colored bars. (Left) slik1/+ control animals. (Middle) Homozygous slik1 mutant animals. (Right) Percent expected homozygous slik1 mutant females rescued by expression of Slik under control of armadilloGAL4. Note that only females received both the armadilloGAL4 driver and the UAS-slik transgene. In competition with rescued females, male larvae die earlier than when all animals are homozygous mutant. The few surviving males are included in the107% recovery at 5 d.(C) Comparison of slik1/+ control females (left) with homozygous slik1 mutant females rescued by expression of Slik under control of armadilloGAL4. Note the reduced body size of the rescued flies.(D–F) Larval internal organs labeled by BrdU incorporation. (D and E) Control larvae fed BrdU from 76 to 92 h and 56 to 72 h AEL, respectively. All nuclei are brown, indicating BrdU incorporation during endoreplication. (F) slik1 mutant larva fed from 76 to 92 h. Few nuclei were labeled. Note that the size is comparable to the much younger wild-type control.
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pbio.0000035-g002: Growth Defects in slik Mutants(A) Heterozygous slik1/+ control and homozygous slik1 mutant larvae after 5 d of growth under uncrowded conditions.(B) Growth and survival characteristics of slik1/+ control and homozygous slik1 mutant larvae. The percentage of animals at each developmental stage on the indicated days are shown by the colored bars. (Left) slik1/+ control animals. (Middle) Homozygous slik1 mutant animals. (Right) Percent expected homozygous slik1 mutant females rescued by expression of Slik under control of armadilloGAL4. Note that only females received both the armadilloGAL4 driver and the UAS-slik transgene. In competition with rescued females, male larvae die earlier than when all animals are homozygous mutant. The few surviving males are included in the107% recovery at 5 d.(C) Comparison of slik1/+ control females (left) with homozygous slik1 mutant females rescued by expression of Slik under control of armadilloGAL4. Note the reduced body size of the rescued flies.(D–F) Larval internal organs labeled by BrdU incorporation. (D and E) Control larvae fed BrdU from 76 to 92 h and 56 to 72 h AEL, respectively. All nuclei are brown, indicating BrdU incorporation during endoreplication. (F) slik1 mutant larva fed from 76 to 92 h. Few nuclei were labeled. Note that the size is comparable to the much younger wild-type control.

Mentions: Homozygous slik1 mutant animals showed a striking larval growth defect (Figure 2A). To characterize this in more detail, we collected first-instar larvae shortly after hatching, cultured them at low density, and tracked their viability and developmental progress. slik1 homozygous mutant larvae were compared with similarly staged heterozygous control larvae. slik mutants were delayed with respect to growth and developmental timing (Figure 2B). After 5 d, the largest mutant larvae had grown to about one-third the size of controls (Figure 2A). Relatively few progressed as far as the third-larval instar. However, some larvae had an abnormally long lifespan. More than 5% of the mutant larvae remained alive for 15 d (three times longer than normal), and some reached a relatively normal third-larval instar size. To confirm that these defects are due to loss of slik function, we tested whether they could be reversed by expression of a slik transgene. Ubiquitous armadilloGAL4-driven slik expression rescued the larval growth defect and lethality (Figure 2B and 2C). Of 160 rescued mutant larvae examined, 115 survived to adulthood, albeit with a developmental delay of several days. These gave rise to adult flies of reduced body size, with mildly rough eyes, but of otherwise normal appearance (Figure 2C).


The Drosophila sterile-20 kinase slik controls cell proliferation and apoptosis during imaginal disc development.

Hipfner DR, Cohen SM - PLoS Biol. (2003)

Growth Defects in slik Mutants(A) Heterozygous slik1/+ control and homozygous slik1 mutant larvae after 5 d of growth under uncrowded conditions.(B) Growth and survival characteristics of slik1/+ control and homozygous slik1 mutant larvae. The percentage of animals at each developmental stage on the indicated days are shown by the colored bars. (Left) slik1/+ control animals. (Middle) Homozygous slik1 mutant animals. (Right) Percent expected homozygous slik1 mutant females rescued by expression of Slik under control of armadilloGAL4. Note that only females received both the armadilloGAL4 driver and the UAS-slik transgene. In competition with rescued females, male larvae die earlier than when all animals are homozygous mutant. The few surviving males are included in the107% recovery at 5 d.(C) Comparison of slik1/+ control females (left) with homozygous slik1 mutant females rescued by expression of Slik under control of armadilloGAL4. Note the reduced body size of the rescued flies.(D–F) Larval internal organs labeled by BrdU incorporation. (D and E) Control larvae fed BrdU from 76 to 92 h and 56 to 72 h AEL, respectively. All nuclei are brown, indicating BrdU incorporation during endoreplication. (F) slik1 mutant larva fed from 76 to 92 h. Few nuclei were labeled. Note that the size is comparable to the much younger wild-type control.
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Related In: Results  -  Collection

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pbio.0000035-g002: Growth Defects in slik Mutants(A) Heterozygous slik1/+ control and homozygous slik1 mutant larvae after 5 d of growth under uncrowded conditions.(B) Growth and survival characteristics of slik1/+ control and homozygous slik1 mutant larvae. The percentage of animals at each developmental stage on the indicated days are shown by the colored bars. (Left) slik1/+ control animals. (Middle) Homozygous slik1 mutant animals. (Right) Percent expected homozygous slik1 mutant females rescued by expression of Slik under control of armadilloGAL4. Note that only females received both the armadilloGAL4 driver and the UAS-slik transgene. In competition with rescued females, male larvae die earlier than when all animals are homozygous mutant. The few surviving males are included in the107% recovery at 5 d.(C) Comparison of slik1/+ control females (left) with homozygous slik1 mutant females rescued by expression of Slik under control of armadilloGAL4. Note the reduced body size of the rescued flies.(D–F) Larval internal organs labeled by BrdU incorporation. (D and E) Control larvae fed BrdU from 76 to 92 h and 56 to 72 h AEL, respectively. All nuclei are brown, indicating BrdU incorporation during endoreplication. (F) slik1 mutant larva fed from 76 to 92 h. Few nuclei were labeled. Note that the size is comparable to the much younger wild-type control.
Mentions: Homozygous slik1 mutant animals showed a striking larval growth defect (Figure 2A). To characterize this in more detail, we collected first-instar larvae shortly after hatching, cultured them at low density, and tracked their viability and developmental progress. slik1 homozygous mutant larvae were compared with similarly staged heterozygous control larvae. slik mutants were delayed with respect to growth and developmental timing (Figure 2B). After 5 d, the largest mutant larvae had grown to about one-third the size of controls (Figure 2A). Relatively few progressed as far as the third-larval instar. However, some larvae had an abnormally long lifespan. More than 5% of the mutant larvae remained alive for 15 d (three times longer than normal), and some reached a relatively normal third-larval instar size. To confirm that these defects are due to loss of slik function, we tested whether they could be reversed by expression of a slik transgene. Ubiquitous armadilloGAL4-driven slik expression rescued the larval growth defect and lethality (Figure 2B and 2C). Of 160 rescued mutant larvae examined, 115 survived to adulthood, albeit with a developmental delay of several days. These gave rise to adult flies of reduced body size, with mildly rough eyes, but of otherwise normal appearance (Figure 2C).

Bottom Line: Tumor-like tissue overgrowth results when apoptosis is prevented.Activation of Raf can compensate for the lack of Slik and support cell survival, but activation of ERK cannot.We suggest that Slik mediates growth and survival cues to promote cell proliferation and control cell survival during Drosophila development.

View Article: PubMed Central - PubMed

Affiliation: European Molecular Biology Laboratory, Heidelberg, Germany.

ABSTRACT
Cell proliferation and programmed cell death are closely controlled during animal development. Proliferative stimuli generally also induce apoptosis, and anti-apoptotic factors are required to allow net cell proliferation. Genetic studies in Drosophila have led to identification of a number of genes that control both processes, providing new insights into the mechanisms that coordinate cell growth, proliferation, and death during development and that fail to do so in diseases of cell proliferation. We present evidence that the Drosophila Sterile-20 kinase Slik promotes cell proliferation and controls cell survival. At normal levels, Slik provides survival cues that prevent apoptosis. Cells deprived of Slik activity can grow, divide, and differentiate, but have an intrinsic survival defect and undergo apoptosis even under conditions in which they are not competing with normal cells for survival cues. Like some oncogenes, excess Slik activity stimulates cell proliferation, but this is compensated for by increased cell death. Tumor-like tissue overgrowth results when apoptosis is prevented. We present evidence that Slik acts via Raf, but not via the canonical ERK pathway. Activation of Raf can compensate for the lack of Slik and support cell survival, but activation of ERK cannot. We suggest that Slik mediates growth and survival cues to promote cell proliferation and control cell survival during Drosophila development.

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