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Loss of Drosophila pseudouridine synthase triggers apoptosis-induced proliferation and promotes cell-nonautonomous EMT.

Vicidomini R, Di Giovanni A, Petrizzo A, Iannucci LF, Benvenuto G, Nagel AC, Preiss A, Furia M - Cell Death Dis (2015)

Bottom Line: Here we show that localized depletion of this enzyme can act as an endogenous stimulus capable of triggering apoptosis-induced proliferation, and that context-dependent effects are elicited in different sub-populations of the silenced cells.Unexpectedly, cell-nonautonomous effects, such as epithelial mesenchymal transition in the contiguous unsilenced squamous epithelium, are also promoted.On this account, our results can add new light on the still unexplained tumor predisposition that characterizes X-linked dyskeratosis, the human disease caused by reduced pseudouridine synthase activity.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Biologia, Università di Napoli 'Federico II', via Cinthia, Naples 80126, Italy.

ABSTRACT
Many developing tissues display regenerative capability that allows them to compensate cell loss and preserve tissue homeostasis. Because of their remarkable regenerative capability, Drosophila wing discs are extensively used for the study of regenerative phenomena. We thus used the developing wing to investigate the role played in tissue homeostasis by the evolutionarily conserved eukaryotic H/ACA small nucleolar ribonucleoprotein pseudouridine synthase. Here we show that localized depletion of this enzyme can act as an endogenous stimulus capable of triggering apoptosis-induced proliferation, and that context-dependent effects are elicited in different sub-populations of the silenced cells. In fact, some cells undergo apoptosis, whereas those surrounding the apoptotic foci, although identically depleted, overproliferate. This overproliferation correlates with ectopic induction of the Wg and JAK-STAT (Janus kinase-signal transducer and activator of transcription) mitogenic pathways. Expression of a p35 transgene, which blocks the complete execution of the death program and generates the so-called 'undead cells', amplifies the proliferative response. Pseudouridine synthase depletion also causes loss of apicobasal polarity, disruption of adherens cell junctions and ectopic induction of JNK (c-Jun N-terminal kinase) and Mmp1 (matrix metalloproteinase-1) activity, leading to a significant epithelial reorganization. Unexpectedly, cell-nonautonomous effects, such as epithelial mesenchymal transition in the contiguous unsilenced squamous epithelium, are also promoted. Collectively, these data point out that cell-cell communication and long-range signaling can take a relevant role in the response to pseudouridine synthase decline. Considering that all the affected pathways are highly conserved throughout evolution, it is plausible that the response to pseudouridine synthase depletion has been widely preserved. On this account, our results can add new light on the still unexplained tumor predisposition that characterizes X-linked dyskeratosis, the human disease caused by reduced pseudouridine synthase activity.

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Epithelial remodeling and formation of p35-induced undead cells in the omb silenced domain. Confocal analysis of wing discs at 96 and 120 h AED upon phalloidin staining. (a) An omb>p35 control disc. Phalloidin is in gray. (b) An omb>IRmfl silenced disc (no. 36595 line) exhibiting a strong tissue disorganization. Phalloidin is in gray and Mfl in red. (c) Expression of p35 in the silenced discs causes formation of big patches of large undead cells that secret high level of Wg (in green) and cluster along the A/P border
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fig2: Epithelial remodeling and formation of p35-induced undead cells in the omb silenced domain. Confocal analysis of wing discs at 96 and 120 h AED upon phalloidin staining. (a) An omb>p35 control disc. Phalloidin is in gray. (b) An omb>IRmfl silenced disc (no. 36595 line) exhibiting a strong tissue disorganization. Phalloidin is in gray and Mfl in red. (c) Expression of p35 in the silenced discs causes formation of big patches of large undead cells that secret high level of Wg (in green) and cluster along the A/P border

Mentions: Finally, we analyzed by phalloidin staining the structure of the silenced disc. As shown in Figure 2, the tissue appeared wrinkled, folded and fractured along the A/P border, where clusters of Cas3-positive cells were observed. These local fractures were strongly enhanced in the presence of an UAS transgene that expresses the baculovirus p35 protein, known to inhibit the function of Cas3 but not its activation.26, 27 UAS-p35 expression has no effect on the epithelium structure in a wild-type background (Figure 2a), whereas in the silenced discs it generates along the A/P margin patches of large ‘undead cells' that, as typical,28 secrete high levels of Wg (Figures 2b and c). The alignment of undead cells along the A/P boundary indicated that these margin cells exhibit a particular sensitivity to Mfl depletion, and first undergo apoptosis. This susceptibility may be an indirect consequence of abnormal formation of the A/P border, possibly due to defects in cell adhesion and/or cell communication.


Loss of Drosophila pseudouridine synthase triggers apoptosis-induced proliferation and promotes cell-nonautonomous EMT.

Vicidomini R, Di Giovanni A, Petrizzo A, Iannucci LF, Benvenuto G, Nagel AC, Preiss A, Furia M - Cell Death Dis (2015)

Epithelial remodeling and formation of p35-induced undead cells in the omb silenced domain. Confocal analysis of wing discs at 96 and 120 h AED upon phalloidin staining. (a) An omb>p35 control disc. Phalloidin is in gray. (b) An omb>IRmfl silenced disc (no. 36595 line) exhibiting a strong tissue disorganization. Phalloidin is in gray and Mfl in red. (c) Expression of p35 in the silenced discs causes formation of big patches of large undead cells that secret high level of Wg (in green) and cluster along the A/P border
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385944&req=5

fig2: Epithelial remodeling and formation of p35-induced undead cells in the omb silenced domain. Confocal analysis of wing discs at 96 and 120 h AED upon phalloidin staining. (a) An omb>p35 control disc. Phalloidin is in gray. (b) An omb>IRmfl silenced disc (no. 36595 line) exhibiting a strong tissue disorganization. Phalloidin is in gray and Mfl in red. (c) Expression of p35 in the silenced discs causes formation of big patches of large undead cells that secret high level of Wg (in green) and cluster along the A/P border
Mentions: Finally, we analyzed by phalloidin staining the structure of the silenced disc. As shown in Figure 2, the tissue appeared wrinkled, folded and fractured along the A/P border, where clusters of Cas3-positive cells were observed. These local fractures were strongly enhanced in the presence of an UAS transgene that expresses the baculovirus p35 protein, known to inhibit the function of Cas3 but not its activation.26, 27 UAS-p35 expression has no effect on the epithelium structure in a wild-type background (Figure 2a), whereas in the silenced discs it generates along the A/P margin patches of large ‘undead cells' that, as typical,28 secrete high levels of Wg (Figures 2b and c). The alignment of undead cells along the A/P boundary indicated that these margin cells exhibit a particular sensitivity to Mfl depletion, and first undergo apoptosis. This susceptibility may be an indirect consequence of abnormal formation of the A/P border, possibly due to defects in cell adhesion and/or cell communication.

Bottom Line: Here we show that localized depletion of this enzyme can act as an endogenous stimulus capable of triggering apoptosis-induced proliferation, and that context-dependent effects are elicited in different sub-populations of the silenced cells.Unexpectedly, cell-nonautonomous effects, such as epithelial mesenchymal transition in the contiguous unsilenced squamous epithelium, are also promoted.On this account, our results can add new light on the still unexplained tumor predisposition that characterizes X-linked dyskeratosis, the human disease caused by reduced pseudouridine synthase activity.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Biologia, Università di Napoli 'Federico II', via Cinthia, Naples 80126, Italy.

ABSTRACT
Many developing tissues display regenerative capability that allows them to compensate cell loss and preserve tissue homeostasis. Because of their remarkable regenerative capability, Drosophila wing discs are extensively used for the study of regenerative phenomena. We thus used the developing wing to investigate the role played in tissue homeostasis by the evolutionarily conserved eukaryotic H/ACA small nucleolar ribonucleoprotein pseudouridine synthase. Here we show that localized depletion of this enzyme can act as an endogenous stimulus capable of triggering apoptosis-induced proliferation, and that context-dependent effects are elicited in different sub-populations of the silenced cells. In fact, some cells undergo apoptosis, whereas those surrounding the apoptotic foci, although identically depleted, overproliferate. This overproliferation correlates with ectopic induction of the Wg and JAK-STAT (Janus kinase-signal transducer and activator of transcription) mitogenic pathways. Expression of a p35 transgene, which blocks the complete execution of the death program and generates the so-called 'undead cells', amplifies the proliferative response. Pseudouridine synthase depletion also causes loss of apicobasal polarity, disruption of adherens cell junctions and ectopic induction of JNK (c-Jun N-terminal kinase) and Mmp1 (matrix metalloproteinase-1) activity, leading to a significant epithelial reorganization. Unexpectedly, cell-nonautonomous effects, such as epithelial mesenchymal transition in the contiguous unsilenced squamous epithelium, are also promoted. Collectively, these data point out that cell-cell communication and long-range signaling can take a relevant role in the response to pseudouridine synthase decline. Considering that all the affected pathways are highly conserved throughout evolution, it is plausible that the response to pseudouridine synthase depletion has been widely preserved. On this account, our results can add new light on the still unexplained tumor predisposition that characterizes X-linked dyskeratosis, the human disease caused by reduced pseudouridine synthase activity.

Show MeSH
Related in: MedlinePlus