Loss of cyclin D1 in necrotic and apoptotic models of cortical neuronal degeneration.
Recent evidence suggests that apoptosis in post-mitotic neurons involves an aborted attempt of cells to re-enter the cell cycle and it is characterized by increased expression of cyclins, such as cyclin D1, prior to death. Cyclin D1 increases to permit transition from growth phase (G0/G1) to synthesis phase (S) during normal development but there is controversy as to which of the cyclins are activated prior to apoptotic cell death. We looked at the expression of cyclin D1 in cortical neuronal cultures treated with either staurosporine to produce apoptotic death, or with glutamate, to produce a non-apoptotic death. Cyclin D1 immunoreactivity was observed in the cytoplasm and nucleus of virtually all neurons under control conditions. Following the addition of either staurosporine or glutamate, cyclin D1 immunoreactivity did not change within 4 h. The cyclin D1 immunoreactivity was lost by 6 h with the appearance of either staurosporine-induced fragmented nuclei or glutamate-induced pyknotic nuclei. These immunocytochemical observations were confirmed with immunoblot analysis. Therefore, cyclin D1 is not a reliable indicator of apoptosis in cortical neuronal cultures and should not be used as an indicator of apoptotic cell death.
Small
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DL
Institute for Biological Sciences, National Research Council of Canada, Building M-54, Montreal Road, Ottawa, Canada. dan.small@nrc.ca
Monette
R
R
Comas
T
T
Fournier
M
M
Morley
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P
D000818:Animals; D017209:Apoptosis; D002453:Cell Cycle / Q000502:physiology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology* / Q000473:pathology; D019938:Cyclin D1 / Q000032:analysis / Q000378:metabolism*; D005333:Fetus; D016193:G1 Phase; D018698:Glutamic Acid / Q000494:pharmacology; D007700:Kinetics; D008959:Models, Neurological; D009336:Necrosis; D009410:Nerve Degeneration; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D016192:Resting Phase, Cell Cycle; D016196:S Phase; D019311:Staurosporine / Q000494:pharmacology
D019938:Cyclin D1; D018698:Glutamic Acid; D019311:Staurosporine