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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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Ultrastructural appearance of paddle cells. After 14 h of incubation in SB in the absence or presence of DIF-1, cells were fixed and processed for EM. (a) In most of the cells incubated without DIF-1, the organelles were evenly distributed within the cytoplasm. Note the presence of autophagic vacuoles. (b) Treatment with DIF-1 induced the formation of paddle-shaped cells in which a marked rearrangement of organelles was observed. Dark patches are probably calcium phosphate deposits (de Chastellier and Ryter, 1981). Arrowheads show membrane interdigitations. M, mitochondrion; N, nucleus; AV, autophagic vacuole; Pro, propodium; Para, parapodium. Bars, 1 μm.
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fig4: Ultrastructural appearance of paddle cells. After 14 h of incubation in SB in the absence or presence of DIF-1, cells were fixed and processed for EM. (a) In most of the cells incubated without DIF-1, the organelles were evenly distributed within the cytoplasm. Note the presence of autophagic vacuoles. (b) Treatment with DIF-1 induced the formation of paddle-shaped cells in which a marked rearrangement of organelles was observed. Dark patches are probably calcium phosphate deposits (de Chastellier and Ryter, 1981). Arrowheads show membrane interdigitations. M, mitochondrion; N, nucleus; AV, autophagic vacuole; Pro, propodium; Para, parapodium. Bars, 1 μm.

Mentions: Electron microscope observation of paddle cells confirmed a redistribution of organelles. In other cells, organelles are evenly distributed within the cytoplasm (Fig. 4 a). Within paddle cells (Fig. 4 b), mitochondria as well as the scarce endocytic or autophagic vacuoles were all concentrated within the posterior (according to time-lapse videos) one third to one half of the cell. The anterior part of the cell, the propodium, appeared devoid of organelles and contained large amounts of ribosome and glycogen. Due to their abundance and high density, the actin filament network that accumulated within this region as shown by phalloidin staining was difficult to visualize by the EM procedure used in the present paper. The nucleus was often located at the interface between the organelle-free and organelle-rich regions. Small portions of ER were also observed at the interface, and sometimes extended into the organelle-free region. Interestingly, adjacent cells often displayed tight plasma membrane interdigitations, especially at the level of the organelle-free regions. The parapodium, known from the time-lapse studies to have adherent properties, was also poor in organelles and rich in actin.


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)

Ultrastructural appearance of paddle cells. After 14 h of incubation in SB in the absence or presence of DIF-1, cells were fixed and processed for EM. (a) In most of the cells incubated without DIF-1, the organelles were evenly distributed within the cytoplasm. Note the presence of autophagic vacuoles. (b) Treatment with DIF-1 induced the formation of paddle-shaped cells in which a marked rearrangement of organelles was observed. Dark patches are probably calcium phosphate deposits (de Chastellier and Ryter, 1981). Arrowheads show membrane interdigitations. M, mitochondrion; N, nucleus; AV, autophagic vacuole; Pro, propodium; Para, parapodium. Bars, 1 μm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2172757&req=5

fig4: Ultrastructural appearance of paddle cells. After 14 h of incubation in SB in the absence or presence of DIF-1, cells were fixed and processed for EM. (a) In most of the cells incubated without DIF-1, the organelles were evenly distributed within the cytoplasm. Note the presence of autophagic vacuoles. (b) Treatment with DIF-1 induced the formation of paddle-shaped cells in which a marked rearrangement of organelles was observed. Dark patches are probably calcium phosphate deposits (de Chastellier and Ryter, 1981). Arrowheads show membrane interdigitations. M, mitochondrion; N, nucleus; AV, autophagic vacuole; Pro, propodium; Para, parapodium. Bars, 1 μm.
Mentions: Electron microscope observation of paddle cells confirmed a redistribution of organelles. In other cells, organelles are evenly distributed within the cytoplasm (Fig. 4 a). Within paddle cells (Fig. 4 b), mitochondria as well as the scarce endocytic or autophagic vacuoles were all concentrated within the posterior (according to time-lapse videos) one third to one half of the cell. The anterior part of the cell, the propodium, appeared devoid of organelles and contained large amounts of ribosome and glycogen. Due to their abundance and high density, the actin filament network that accumulated within this region as shown by phalloidin staining was difficult to visualize by the EM procedure used in the present paper. The nucleus was often located at the interface between the organelle-free and organelle-rich regions. Small portions of ER were also observed at the interface, and sometimes extended into the organelle-free region. Interestingly, adjacent cells often displayed tight plasma membrane interdigitations, especially at the level of the organelle-free regions. The parapodium, known from the time-lapse studies to have adherent properties, was also poor in organelles and rich in actin.

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.

Show MeSH
Related in: MedlinePlus