Mitochondrial Bcl-xL promotes brain synaptogenesis by controlling non-lethal caspase activation

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Biology

Background:

• Non-lethal caspase activation (NLCA) plays a role in neurodevelopment.
• The precise mechanisms controlling NLCA in neurons are not fully understood.
• Bcl-xL, a Bcl-2 homolog, regulates caspase activation via mitochondria.

Purpose of the Study:

• To investigate the role of mitochondrial Bcl-xL in neuronal caspase activation and neurodevelopment.
• To characterize a novel mouse model with altered Bcl-xL localization.

Main Methods:

• Generated an ER-xL mouse model with Bcl-xL absent in mitochondria but present in the endoplasmic reticulum.
• Analyzed caspase-3 activity in brain and spinal cord tissues.
• Assessed neuronal cell death and neurite morphology in ER-xL mice.
• Investigated the involvement of Drp-1-dependent mitochondrial fission.

Main Results:

• ER-xL mice survived embryonic development but exhibited post-partum lethality due to feeding behavior deficits.
• Increased caspase-3 activity was detected in white matter of the brain and spinal cord, independent of apoptosis.
• ER-xL neurons showed elevated caspase-3 activity in neurites, leading to impaired axon branching and synapse formation.
• Findings suggest mitochondrial Bcl-xL regulates caspase-3 activity via Drp-1-dependent mitochondrial fission.

Conclusions:

• Mitochondrial Bcl-xL is crucial for fine-tuning caspase-3 activity.
• This regulation is essential for proper neural network design, including axon arborescence and synaptogenesis.
• The study identifies a novel role for mitochondrial Bcl-xL in apoptosis-independent neuronal processes vital for development.