Alternative cell death of Apaf1-deficient neural progenitor cells induced by withdrawal of EGF or insulin.
BACKGROUND
Various forms of cell death, such as apoptotic, autophagic and non-lysosomal types, are implicated in normal physiological processes. Apoptotic protease activating factor 1 (Apaf1) is an important component of the intrinsic apoptotic pathway. Deficiency of Apaf1 results in an accumulation of neural progenitor cells (NPCs) in the developing central nervous system and thus, in perinatal lethality. A small percentage of the mutant mice, however, are viable and grow to maturity. The occurrence of such normal mutants implicates alternative cell death pathways during neurogenesis.


METHODS
NPCs prepared from wild-type or Apaf1-deficient embryos were cultured in growth factor-deprived medium and examined for cell death, caspase activation and morphological alterations. Generation of reactive oxygen species (ROS) and the effects of antioxidants were examined.


RESULTS
Wild-type NPCs underwent apoptosis within 24 hours of withdrawal of epidermal growth factor (EGF) or insulin, whereas Apaf1-deficient NPCs underwent cell death but showed no signs of apoptosis. Autophagy was not necessarily accompanied by cell death. Cell death of the Apaf1-deficient NPCs resembled necroptosis-necrosis-like programmed cell death. The necroptosis inhibitor necrostatin-1, however, failed to inhibit the cell death. ROS accumulation was detected in NPCs deprived of growth factors, and an antioxidant partially suppressed the non-apoptotic cell death of Apaf1-deficient NPCs.


CONCLUSIONS
These data indicate that after withdrawal EGF or insulin withdrawal, the Apaf1-deficient cells underwent non-apoptotic cell death. ROS generation may partially participate in the cell death.


CONCLUSIONS
Non-apoptotic cell death in NPCs may be a compensatory mechanism in the developing CNS of Apaf1-deficient embryos.
Shiraishi
Hiroshi
H
Division of Medical Biochemistry, Department of Biomolecular Sciences, Faculty of Medicine, Saga University, Saga 849-8501, Japan.
Okamoto
Hideaki
H
Hara
Hiromitsu
H
Yoshida
Hiroki
H
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D053477:Apoptotic Protease-Activating Factor 1 / Q000172:deficiency* / Q000235:genetics; D016923:Cell Death / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects; D003433:Crosses, Genetic; D017931:DNA Primers; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005838:Genotype; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D019284:Thapsigargin / Q000494:pharmacology; D014415:Tunicamycin / Q000494:pharmacology
D000975:Antioxidants; C506593:Apaf1 protein, mouse; D053477:Apoptotic Protease-Activating Factor 1; D017931:DNA Primers; D007328:Insulin; D014415:Tunicamycin; D004815:Epidermal Growth Factor; D019284:Thapsigargin