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Dictyostelium cell death: early emergence and demise of highly polarized paddle cells.

Levraud JP, Adam M, Luciani MF, de Chastellier C, Blanton RL, Golstein P - J. Cell Biol. (2003)

Bottom Line: Paddle cell demise was not related to formation of the cellulose shell because cells where the cellulose-synthase gene had been inactivated underwent death indistinguishable from that of parental cells.A major subcellular alteration at the paddle-to-round cell transition was the disappearance of F-actin.The Dictyostelium vacuolar cell death pathway thus does not require cellulose synthesis and includes early actin rearrangements (F-actin segregation, then depolymerization), contemporary with irreversibility, corresponding to the emergence and demise of highly polarized paddle cells.

View Article: PubMed Central - PubMed

Affiliation: Centre d'Immunologie de Marseille-Luminy, INSERM/CNRS, Case 906, Parc Scientifique de Luminy, 13288 Marseille Cedex 9, France.

ABSTRACT
Cell death in the stalk of Dictyostelium discoideum, a prototypic vacuolar cell death, can be studied in vitro using cells differentiating as a monolayer. To identify early events, we examined potentially dying cells at a time when the classical signs of Dictyostelium cell death, such as heavy vacuolization and membrane lesions, were not yet apparent. We observed that most cells proceeded through a stereotyped series of differentiation stages, including the emergence of "paddle" cells showing high motility and strikingly marked subcellular compartmentalization with actin segregation. Paddle cell emergence and subsequent demise with paddle-to-round cell transition may be critical to the cell death process, as they were contemporary with irreversibility assessed through time-lapse videos and clonogenicity tests. Paddle cell demise was not related to formation of the cellulose shell because cells where the cellulose-synthase gene had been inactivated underwent death indistinguishable from that of parental cells. A major subcellular alteration at the paddle-to-round cell transition was the disappearance of F-actin. The Dictyostelium vacuolar cell death pathway thus does not require cellulose synthesis and includes early actin rearrangements (F-actin segregation, then depolymerization), contemporary with irreversibility, corresponding to the emergence and demise of highly polarized paddle cells.

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Cell rounding is accompanied with actin depolymerization. (a) HMX44A cells 16 h after addition of DIF-1. Left, phase contrast; right, same field stained with CMXRos and phalloidin. Although paddle cells are labeled with both CMXRos (red) and phalloidin (green), a number of round cells are labeled with CMXRos, but not with phalloidin. (b) Another field showing other similar cell patterns.
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fig6: Cell rounding is accompanied with actin depolymerization. (a) HMX44A cells 16 h after addition of DIF-1. Left, phase contrast; right, same field stained with CMXRos and phalloidin. Although paddle cells are labeled with both CMXRos (red) and phalloidin (green), a number of round cells are labeled with CMXRos, but not with phalloidin. (b) Another field showing other similar cell patterns.

Mentions: If not due to an external constraint, then to what is the paddle-to-round cell transition due? This transition was found to be accompanied also with loss of an internal constraint. Namely, round cells were CMXRos-positive, but phalloidin-negative, thus without detectable F-actin (Fig. 6). To quantify this, in a given experiment, cells at 15 h in DIF-1 were photographed and checked for morphology and staining. Of 228 cells, 43 had paddle morphology (about one fifth), and all of these were stained by both CMXRos and phalloidin in a paddle-segregated manner. The remaining 185 cells showed round morphology. Of these round cells, 135 were stained by both CMXRos and phalloidin; however, often with phalloidin staining reduced to a rim, whereas 50 were CMXRos-positive and phalloidin-negative, consistent with a paddle-to-round cell transition accompanied with actin depolymerization. We attempted to document the likely causality relationship between rounding and actin depolymerization by using jasplakinolide or latrunculin A. However, in this system, the toxicity of these drugs rendered interpretation of results difficult (unpublished data).


Dictyostelium cell death: early emergence and demise of highly polarized paddle cells.

Levraud JP, Adam M, Luciani MF, de Chastellier C, Blanton RL, Golstein P - J. Cell Biol. (2003)

Cell rounding is accompanied with actin depolymerization. (a) HMX44A cells 16 h after addition of DIF-1. Left, phase contrast; right, same field stained with CMXRos and phalloidin. Although paddle cells are labeled with both CMXRos (red) and phalloidin (green), a number of round cells are labeled with CMXRos, but not with phalloidin. (b) Another field showing other similar cell patterns.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2172757&req=5

fig6: Cell rounding is accompanied with actin depolymerization. (a) HMX44A cells 16 h after addition of DIF-1. Left, phase contrast; right, same field stained with CMXRos and phalloidin. Although paddle cells are labeled with both CMXRos (red) and phalloidin (green), a number of round cells are labeled with CMXRos, but not with phalloidin. (b) Another field showing other similar cell patterns.
Mentions: If not due to an external constraint, then to what is the paddle-to-round cell transition due? This transition was found to be accompanied also with loss of an internal constraint. Namely, round cells were CMXRos-positive, but phalloidin-negative, thus without detectable F-actin (Fig. 6). To quantify this, in a given experiment, cells at 15 h in DIF-1 were photographed and checked for morphology and staining. Of 228 cells, 43 had paddle morphology (about one fifth), and all of these were stained by both CMXRos and phalloidin in a paddle-segregated manner. The remaining 185 cells showed round morphology. Of these round cells, 135 were stained by both CMXRos and phalloidin; however, often with phalloidin staining reduced to a rim, whereas 50 were CMXRos-positive and phalloidin-negative, consistent with a paddle-to-round cell transition accompanied with actin depolymerization. We attempted to document the likely causality relationship between rounding and actin depolymerization by using jasplakinolide or latrunculin A. However, in this system, the toxicity of these drugs rendered interpretation of results difficult (unpublished data).

Bottom Line: Paddle cell demise was not related to formation of the cellulose shell because cells where the cellulose-synthase gene had been inactivated underwent death indistinguishable from that of parental cells.A major subcellular alteration at the paddle-to-round cell transition was the disappearance of F-actin.The Dictyostelium vacuolar cell death pathway thus does not require cellulose synthesis and includes early actin rearrangements (F-actin segregation, then depolymerization), contemporary with irreversibility, corresponding to the emergence and demise of highly polarized paddle cells.

View Article: PubMed Central - PubMed

Affiliation: Centre d'Immunologie de Marseille-Luminy, INSERM/CNRS, Case 906, Parc Scientifique de Luminy, 13288 Marseille Cedex 9, France.

ABSTRACT
Cell death in the stalk of Dictyostelium discoideum, a prototypic vacuolar cell death, can be studied in vitro using cells differentiating as a monolayer. To identify early events, we examined potentially dying cells at a time when the classical signs of Dictyostelium cell death, such as heavy vacuolization and membrane lesions, were not yet apparent. We observed that most cells proceeded through a stereotyped series of differentiation stages, including the emergence of "paddle" cells showing high motility and strikingly marked subcellular compartmentalization with actin segregation. Paddle cell emergence and subsequent demise with paddle-to-round cell transition may be critical to the cell death process, as they were contemporary with irreversibility assessed through time-lapse videos and clonogenicity tests. Paddle cell demise was not related to formation of the cellulose shell because cells where the cellulose-synthase gene had been inactivated underwent death indistinguishable from that of parental cells. A major subcellular alteration at the paddle-to-round cell transition was the disappearance of F-actin. The Dictyostelium vacuolar cell death pathway thus does not require cellulose synthesis and includes early actin rearrangements (F-actin segregation, then depolymerization), contemporary with irreversibility, corresponding to the emergence and demise of highly polarized paddle cells.

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