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Bcl-xL is a negative regulator of caspase-3 activation in immature neurons during development
1Division of Development and Differentiation, National Institute of Neuroscience, NCNP, Kodaira, Tokyo 187-8502, Japan.
Abstract:
Caspases and Bcl-xL, the mammalian homologues of the Caenorhabditis elegans (C. elegans) ced-3 and ced-9 genes, respectively, regulate apoptosis of various cells. Caspase-3 is processed into an active form (p20 or p17 and p12) during apoptosis. We investigated the relation between caspase-3 and Bcl-xL during development by examining activation of caspase-3 and apoptotic cells in Bcl-x-deficient (bcl-x(-/-)) mice at embryonic (E) day 11.5. We used a double-staining technique with a cleavage site-directed antibody against caspase-3 (anti-p20/17) and terminal-deoxytransferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL). Bcl-xL-deficiency increased both numbers of p20/17-positive and -negative apoptotic cells in dorsal root ganglia (DRG); the numbers of p20/17-positive apoptotic cells in the caudal parts of the ventral hindbrain and ventral spinal cord; and the numbers of p20/17-negative apoptotic cells in the dorsal midbrain, dorsal hindbrain, and dorsal spinal cord. Thus, Bcl-xL blocks the caspase-3-dependent apoptotic pathway in the restricted regions of the nervous system during development. Furthermore, these observations suggest that Bcl-xL protects against activation of the caspase-3-independent apoptotic pathway. Other caspases or apoptotic mechanisms may also be activated in the nervous systems of bcl-x(-/-) mice.
Insights
Bcl-xL protein regulates apoptosis during development. In mice lacking Bcl-xL, caspase-3 activation and cell death increased in specific nervous system regions, indicating Bcl-xL
Area of Science:
- Developmental biology
- Cell biology
- Neuroscience
Background:
- Apoptosis, or programmed cell death, is crucial for development.
- Caspases and Bcl-xL are key regulators of apoptosis.
- Bcl-xL is the mammalian homologue of C. elegans ced-9, while caspases are homologues of ced-3.
Purpose of the Study:
- To investigate the relationship between caspase-3 activation and Bcl-xL during embryonic development.
- To examine the role of Bcl-xL in regulating apoptosis in the developing nervous system.
Main Methods:
- Utilized Bcl-x-deficient (bcl-x(-/-)) mice at embryonic day 11.5.
- Employed a double-staining technique combining a caspase-3 cleavage site-directed antibody (anti-p20/17) and TUNEL assay.
- Quantified apoptotic cells and caspase-3 activation in various neural tissues.
Main Results:
- Bcl-xL deficiency led to increased numbers of both caspase-3-positive and -negative apoptotic cells in dorsal root ganglia (DRG).
- Increased caspase-3-positive apoptotic cells were observed in the caudal ventral hindbrain and ventral spinal cord.
- Increased caspase-3-negative apoptotic cells were found in the dorsal midbrain, dorsal hindbrain, and dorsal spinal cord.
Conclusions:
- Bcl-xL inhibits the caspase-3-dependent apoptotic pathway in specific regions of the developing nervous system.
- Bcl-xL may also protect against caspase-3-independent apoptotic pathways.
- Alternative caspases or apoptotic mechanisms might be activated in Bcl-xL-deficient mouse nervous systems.