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Published on: February 1, 2018
Dark is a Drosophila homologue of Apaf-1/CED-4 and functions in an evolutionarily conserved death pathway
1Department of Cell Biology and Neuroscience, University of Texas Southwestern Medical Center, Dallas 75235-9039, USA.
Abstract:
Here we identify a new gene, dark, which encodes a Drosophila homologue of mammalian Apaf-1 and Caenorhabditis elegans CED-4, cell-death proteins. Like Apaf-1, but in contrast to CED-4, Dark contains a carboxy-terminal WD-repeat domain necessary for interactions with the mitochondrial protein cytochrome c. Dark selectively associates with another protein involved in apoptosis, the fly apical caspase, Dredd. Dark-induced cell killing is suppressed by caspase-inhibitory peptides and by a dominant-negative mutant Dredd protein, and enhanced by removal of the WD domain. Loss-of-function mutations in dark attenuate programmed cell deaths during development, causing hyperplasia of the central nervous system, and other abnormalities including ectopic melanotic tumours and defective wings. Moreover, ectopic cell killing by the Drosophila cell-death activators, Reaper, Grim and Hid, is substantially suppressed in dark mutants. These findings establish dark as an important apoptosis effector in Drosophila and raise profound evolutionary considerations concerning the relationship between mitochondrial components and the apoptosis-promoting machinery.
Insights
Researchers identified the gene dark, a Drosophila homolog of cell-death proteins Apaf-1 and CED-4. Dark interacts with cytochrome c and caspase Dredd, playing a crucial role in apoptosis and development. Dark mutations disrupt programmed cell death, leading to developmental abnormalities.
Area of Science:
- Molecular Biology
- Developmental Biology
- Genetics
Background:
- Apoptosis, or programmed cell death, is a fundamental biological process.
- Mammalian Apaf-1 and C. elegans CED-4 are key regulators of apoptosis.
- The molecular mechanisms of apoptosis in Drosophila are not fully understood.
Purpose of the Study:
- To identify and characterize novel genes involved in apoptosis in Drosophila.
- To elucidate the role of the newly identified gene, dark, in programmed cell death pathways.
- To investigate the evolutionary conservation of apoptosis pathways.
Main Methods:
- Gene identification and cloning.
- Protein interaction studies (e.g., yeast two-hybrid, co-immunoprecipitation).
- Functional assays using genetic mutants and cell culture.
- Analysis of developmental phenotypes.
Main Results:
- A novel gene, dark, was identified in Drosophila, encoding a homolog of Apaf-1 and CED-4.
- Dark interacts with mitochondrial cytochrome c and the caspase Dredd.
- Loss-of-function mutations in dark lead to developmental defects, including hyperplasia and abnormal tissue development, and suppress ectopic cell death induced by Reaper, Grim, and Hid.
Conclusions:
- Dark is a critical effector molecule in the Drosophila apoptosis pathway.
- Dark integrates signals from mitochondrial components like cytochrome c to activate caspases.
- The findings highlight conserved mechanisms in apoptosis regulation across species and suggest evolutionary links between mitochondrial function and cell death machinery.
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