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Cell cycle progression and cell division are sensitive to hypoxia in Drosophila melanogaster embryos
R M Douglas1, T Xu, G G Haddad
1Department of Pediatrics, Section of Respiratory Medicine, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Abstract:
We and others recently demonstrated that Drosophila melanogaster embryos arrest development and embryonic cells cease dividing when they are deprived of O2. To further characterize the behavior of these embryos in response to O2 deprivation and to define the O2-sensitive checkpoints in the cell cycle, embryos undergoing nuclear cycles 3-13 were subjected to O2 deprivation and examined by confocal microscopy under control, hypoxic, and reoxygenation conditions. In vivo, real-time analysis of embryos carrying green fluorescent protein-kinesin demonstrated that cells arrest at two major points of the cell cycle, either at the interphase (before DNA duplication) or at metaphase, depending on the cell cycle phase at which O2 deprivation was induced. Immunoblot analysis of embryos whose cell divisions are synchronized by inducible String (cdc25 homolog) demonstrated that cyclin B was degraded during low O2 conditions in interphase-arrested embryos but not in those arrested in metaphase. Embryos resumed cell cycle activity within ~20 min of reoxygenation, with very little apparent change in cell cycle kinetics. We conclude that there are specific points during the embryonic cell cycle that are sensitive to the O2 level in D. melanogaster. Given the fact that O2 deprivation also influences the growth and development of other species, we suggest that similar hypoxia-sensitive cell cycle checkpoints may also exist in mammalian cells.
Insights
Fruit fly embryos stop dividing when oxygen is low, arresting at specific cell cycle stages. These oxygen-sensitive checkpoints in Drosophila melanogaster development may inform similar mechanisms in mammals.
Area of Science:
- Developmental Biology
- Cell Cycle Regulation
- Hypoxia Research
Background:
- Drosophila melanogaster embryos exhibit developmental arrest and cell division cessation under oxygen deprivation.
- Previous studies established the link between oxygen levels and embryonic development in fruit flies.
Purpose of the Study:
- To characterize the behavior of Drosophila embryos during oxygen deprivation.
- To identify specific oxygen-sensitive checkpoints within the embryonic cell cycle.
- To investigate the molecular mechanisms underlying cell cycle arrest under hypoxia.
Main Methods:
- Confocal microscopy was used for in vivo, real-time analysis of embryos.
- Embryos underwent controlled oxygen deprivation and reoxygenation.
- Immunoblot analysis examined cyclin B degradation in synchronized cell cycles.
Main Results:
- Oxygen deprivation induced cell cycle arrest at interphase or metaphase, depending on the cell cycle phase.
- Cyclin B degradation occurred in interphase-arrested embryos but not in metaphase-arrested embryos under low oxygen.
- Embryos resumed cell cycle activity rapidly upon reoxygenation (~20 min).
Conclusions:
- Drosophila melanogaster embryos possess specific oxygen-sensitive cell cycle checkpoints.
- Hypoxia-induced cell cycle arrest mechanisms in flies may be conserved in other species, including mammals.
- Understanding these checkpoints is crucial for comprehending developmental responses to oxygen levels.