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Loss of putzig Activity Results in Apoptosis during Wing Imaginal Development in Drosophila.

Zimmermann M, Kugler SJ, Schulz A, Nagel AC - PLoS ONE (2015)

Bottom Line: We present evidence that downregulation of Notch activates Dcp1 caspase and JNK signaling, however, neither induces ectopic wg nor dpp expression.In contrast, the consequences of Dref-RNAi were largely indistinguishable from pzg-RNAi with regard to apoptosis induction.Moreover, overexpression of Dref ameliorated the downregulation of pzg compatible with the notion that the two are required together to maintain cell and tissue homeostasis in Drosophila.

View Article: PubMed Central - PubMed

Affiliation: Institute of Genetics, University of Hohenheim, 70599 Stuttgart, Germany.

ABSTRACT
The Drosophila gene putzig (pzg) encodes a nuclear protein that is an integral component of the Trf2/Dref complex involved in the transcription of proliferation-related genes. Moreover, Pzg is found in a complex together with the nucleosome remodeling factor NURF, where it promotes Notch target gene activation. Here we show that downregulation of pzg activity in the developing wing imaginal discs induces an apoptotic response, accompanied by the induction of the pro-apoptotic gene reaper, repression of Drosophila inhibitor of apoptosis protein accumulation and the activation of the caspases Drice, Caspase3 and Dcp1. As a further consequence 'Apoptosis induced Proliferation' (AiP) and 'Apoptosis induced Apoptosis' (AiA) are triggered. As expected, the activity of the stress kinase Jun N-terminal kinase (JNK), proposed to mediate both processes, is ectopically induced in response to pzg loss. In addition, the expression of the mitogen wingless (wg) but not of decapentaplegic (dpp) is observed. We present evidence that downregulation of Notch activates Dcp1 caspase and JNK signaling, however, neither induces ectopic wg nor dpp expression. In contrast, the consequences of Dref-RNAi were largely indistinguishable from pzg-RNAi with regard to apoptosis induction. Moreover, overexpression of Dref ameliorated the downregulation of pzg compatible with the notion that the two are required together to maintain cell and tissue homeostasis in Drosophila.

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pzg mutant cells show characteristics of genuine dying cells and induce AiP.pzg was downregulated in the posterior part of the wing disc. Pzg protein is shown in blue (C, C''), the posterior compartment is marked in green with GFP (A-D; A''-D''; A'''-B'''). (A-A''') DNA-synthesis visualized with EdU-labeling (red) is amplified anteriorly along the A/P compartment boundary (arrows) upon pzg depletion (A-A') compared to en-Gal4 UAS-GFP control (A'''), whereas a loss can be observed within the posterior compartment (open arrow, A-A'). (B-B''') Cell division was visualized with anti-PH3 (red). Compared to the control (B'''), many cells in the posterior domain lost this marker upon pzg depletion (arrowhead, B-B'), whereas a strip of cells anterior to the A/P boundary shows stronger PH3 labeling (arrows, B-B'). (C-C'') Expression of Wg protein was monitored (red): it is interrupted at the dorso-ventral boundary in response to pzg-RNAi depletion (arrowhead in C'), whereas ectopic induction of Wg is observed in the posterior compartment outside the normal Wg expression domain (arrows, C'). (D-D'') dpp-lacZ expression (red) is unchanged by pzg depletion in the posterior compartment. Genotypes: (A'''-B''') en-Gal4 UAS-GFP/+. (A-C'') en-Gal4 UAS-GFP UAS-pzg-RNAi/+. (D-D'') en-Gal4 UAS-GFP UAS-pzg-RNAi/+; dpp-lacZ/+. Wing discs are oriented posterior rightwards and dorsally upwards. The A/P compartment boundary is marked with a dotted line. Scale bars represent: (A, B, D) 100 μm, (C) 50 μm.
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pone.0124652.g004: pzg mutant cells show characteristics of genuine dying cells and induce AiP.pzg was downregulated in the posterior part of the wing disc. Pzg protein is shown in blue (C, C''), the posterior compartment is marked in green with GFP (A-D; A''-D''; A'''-B'''). (A-A''') DNA-synthesis visualized with EdU-labeling (red) is amplified anteriorly along the A/P compartment boundary (arrows) upon pzg depletion (A-A') compared to en-Gal4 UAS-GFP control (A'''), whereas a loss can be observed within the posterior compartment (open arrow, A-A'). (B-B''') Cell division was visualized with anti-PH3 (red). Compared to the control (B'''), many cells in the posterior domain lost this marker upon pzg depletion (arrowhead, B-B'), whereas a strip of cells anterior to the A/P boundary shows stronger PH3 labeling (arrows, B-B'). (C-C'') Expression of Wg protein was monitored (red): it is interrupted at the dorso-ventral boundary in response to pzg-RNAi depletion (arrowhead in C'), whereas ectopic induction of Wg is observed in the posterior compartment outside the normal Wg expression domain (arrows, C'). (D-D'') dpp-lacZ expression (red) is unchanged by pzg depletion in the posterior compartment. Genotypes: (A'''-B''') en-Gal4 UAS-GFP/+. (A-C'') en-Gal4 UAS-GFP UAS-pzg-RNAi/+. (D-D'') en-Gal4 UAS-GFP UAS-pzg-RNAi/+; dpp-lacZ/+. Wing discs are oriented posterior rightwards and dorsally upwards. The A/P compartment boundary is marked with a dotted line. Scale bars represent: (A, B, D) 100 μm, (C) 50 μm.

Mentions: Genetic studies in Drosophila have shown that different mechanisms are triggered in apoptotic cells leading to an increase in proliferation and cell division rates of adjacent cells, a process which is referred to as Apoptosis induced Proliferation (AiP) (reviewed in [14,17,69,70]). In order to investigate the consequences of pzg depletion with regard to AiP, we monitored the proliferation rates in wing discs, where pzg-RNAi was induced in the posterior compartment. As pzg was shown to be required for the activation of cell cycle related genes [40], the autonomous decrease of actively dividing cells upon pzg depletion compared with controls was expected (Fig 4A-B'''). In addition we noted an elevated number of cells undergoing DNA synthesis (EdU labeled) as well of mitotic cells (PH3 labeled) abutting the pzg-RNAi mutant territory at the anterior, implying the induction of a non-autonomous cell division response (Fig 4A-B''').


Loss of putzig Activity Results in Apoptosis during Wing Imaginal Development in Drosophila.

Zimmermann M, Kugler SJ, Schulz A, Nagel AC - PLoS ONE (2015)

pzg mutant cells show characteristics of genuine dying cells and induce AiP.pzg was downregulated in the posterior part of the wing disc. Pzg protein is shown in blue (C, C''), the posterior compartment is marked in green with GFP (A-D; A''-D''; A'''-B'''). (A-A''') DNA-synthesis visualized with EdU-labeling (red) is amplified anteriorly along the A/P compartment boundary (arrows) upon pzg depletion (A-A') compared to en-Gal4 UAS-GFP control (A'''), whereas a loss can be observed within the posterior compartment (open arrow, A-A'). (B-B''') Cell division was visualized with anti-PH3 (red). Compared to the control (B'''), many cells in the posterior domain lost this marker upon pzg depletion (arrowhead, B-B'), whereas a strip of cells anterior to the A/P boundary shows stronger PH3 labeling (arrows, B-B'). (C-C'') Expression of Wg protein was monitored (red): it is interrupted at the dorso-ventral boundary in response to pzg-RNAi depletion (arrowhead in C'), whereas ectopic induction of Wg is observed in the posterior compartment outside the normal Wg expression domain (arrows, C'). (D-D'') dpp-lacZ expression (red) is unchanged by pzg depletion in the posterior compartment. Genotypes: (A'''-B''') en-Gal4 UAS-GFP/+. (A-C'') en-Gal4 UAS-GFP UAS-pzg-RNAi/+. (D-D'') en-Gal4 UAS-GFP UAS-pzg-RNAi/+; dpp-lacZ/+. Wing discs are oriented posterior rightwards and dorsally upwards. The A/P compartment boundary is marked with a dotted line. Scale bars represent: (A, B, D) 100 μm, (C) 50 μm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4403878&req=5

pone.0124652.g004: pzg mutant cells show characteristics of genuine dying cells and induce AiP.pzg was downregulated in the posterior part of the wing disc. Pzg protein is shown in blue (C, C''), the posterior compartment is marked in green with GFP (A-D; A''-D''; A'''-B'''). (A-A''') DNA-synthesis visualized with EdU-labeling (red) is amplified anteriorly along the A/P compartment boundary (arrows) upon pzg depletion (A-A') compared to en-Gal4 UAS-GFP control (A'''), whereas a loss can be observed within the posterior compartment (open arrow, A-A'). (B-B''') Cell division was visualized with anti-PH3 (red). Compared to the control (B'''), many cells in the posterior domain lost this marker upon pzg depletion (arrowhead, B-B'), whereas a strip of cells anterior to the A/P boundary shows stronger PH3 labeling (arrows, B-B'). (C-C'') Expression of Wg protein was monitored (red): it is interrupted at the dorso-ventral boundary in response to pzg-RNAi depletion (arrowhead in C'), whereas ectopic induction of Wg is observed in the posterior compartment outside the normal Wg expression domain (arrows, C'). (D-D'') dpp-lacZ expression (red) is unchanged by pzg depletion in the posterior compartment. Genotypes: (A'''-B''') en-Gal4 UAS-GFP/+. (A-C'') en-Gal4 UAS-GFP UAS-pzg-RNAi/+. (D-D'') en-Gal4 UAS-GFP UAS-pzg-RNAi/+; dpp-lacZ/+. Wing discs are oriented posterior rightwards and dorsally upwards. The A/P compartment boundary is marked with a dotted line. Scale bars represent: (A, B, D) 100 μm, (C) 50 μm.
Mentions: Genetic studies in Drosophila have shown that different mechanisms are triggered in apoptotic cells leading to an increase in proliferation and cell division rates of adjacent cells, a process which is referred to as Apoptosis induced Proliferation (AiP) (reviewed in [14,17,69,70]). In order to investigate the consequences of pzg depletion with regard to AiP, we monitored the proliferation rates in wing discs, where pzg-RNAi was induced in the posterior compartment. As pzg was shown to be required for the activation of cell cycle related genes [40], the autonomous decrease of actively dividing cells upon pzg depletion compared with controls was expected (Fig 4A-B'''). In addition we noted an elevated number of cells undergoing DNA synthesis (EdU labeled) as well of mitotic cells (PH3 labeled) abutting the pzg-RNAi mutant territory at the anterior, implying the induction of a non-autonomous cell division response (Fig 4A-B''').

Bottom Line: We present evidence that downregulation of Notch activates Dcp1 caspase and JNK signaling, however, neither induces ectopic wg nor dpp expression.In contrast, the consequences of Dref-RNAi were largely indistinguishable from pzg-RNAi with regard to apoptosis induction.Moreover, overexpression of Dref ameliorated the downregulation of pzg compatible with the notion that the two are required together to maintain cell and tissue homeostasis in Drosophila.

View Article: PubMed Central - PubMed

Affiliation: Institute of Genetics, University of Hohenheim, 70599 Stuttgart, Germany.

ABSTRACT
The Drosophila gene putzig (pzg) encodes a nuclear protein that is an integral component of the Trf2/Dref complex involved in the transcription of proliferation-related genes. Moreover, Pzg is found in a complex together with the nucleosome remodeling factor NURF, where it promotes Notch target gene activation. Here we show that downregulation of pzg activity in the developing wing imaginal discs induces an apoptotic response, accompanied by the induction of the pro-apoptotic gene reaper, repression of Drosophila inhibitor of apoptosis protein accumulation and the activation of the caspases Drice, Caspase3 and Dcp1. As a further consequence 'Apoptosis induced Proliferation' (AiP) and 'Apoptosis induced Apoptosis' (AiA) are triggered. As expected, the activity of the stress kinase Jun N-terminal kinase (JNK), proposed to mediate both processes, is ectopically induced in response to pzg loss. In addition, the expression of the mitogen wingless (wg) but not of decapentaplegic (dpp) is observed. We present evidence that downregulation of Notch activates Dcp1 caspase and JNK signaling, however, neither induces ectopic wg nor dpp expression. In contrast, the consequences of Dref-RNAi were largely indistinguishable from pzg-RNAi with regard to apoptosis induction. Moreover, overexpression of Dref ameliorated the downregulation of pzg compatible with the notion that the two are required together to maintain cell and tissue homeostasis in Drosophila.

Show MeSH
Related in: MedlinePlus