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© The Rockefeller University Press,
0021-9525/2003/3/1105 $5.00
The Journal of Cell Biology, Volume 160, Number 7, 1105-1114
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Dictyostelium cell death
: early emergence and demise of highly polarized paddle cells
2 Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409
Address correspondence to Pierre Golstein, Centre d'Immunologie de Marseille-Luminy, INSERM/CNRS, Case 906, Parc Scientifique de Luminy, 13288 Marseille Cedex 9, France. Tel.: 33-4-91-26-94-68. Fax: 33-4-91-26-94-30. E-mail: golstein{at}ciml.univ-mrs.fr
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.
Key Words: cell death; Dictyostelium; actin; cellulose; cell polarity
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