Retrograde Mitochondrial Transport Is Essential for Organelle Distribution and Health in Zebrafish Neurons

Area of Science:

• Neuroscience
• Cell Biology
• Mitochondrial Dynamics

Background:

• Mitochondria are vital for neuronal function, with dysfunction linked to neurodegenerative diseases.
• Anterograde mitochondrial transport is understood, but retrograde transport remains largely unexplored.
• Retrograde transport is thought to facilitate organelle degradation in the cell body.

Purpose of the Study:

• To investigate the frequency and function of retrograde mitochondrial transport in neurons.
• To determine the impact of disrupting retrograde transport on mitochondria and axons.
• To understand the role of retrograde transport in maintaining mitochondrial homeostasis and neural circuit function.

Main Methods:

• Long-term in vivo imaging of mitochondrial motility in zebrafish sensory and motor axons.
• Tracking of mitochondria leaving axon terminals to assess their fate.
• Assays of neural circuit activity following disruption of mitochondrial transport.

Main Results:

• Retrograde mitochondrial transport enables daily replacement of axon terminal mitochondria.
• Mitochondria transported retrogradely persist for days, not solely degraded.
• Disruption leads to aged organelle accumulation in axon terminals and loss in cell bodies.
• Motor neuron axon terminal activity is negatively impacted, while sensory remains unaffected.

Conclusions:

• Retrograde mitochondrial transport is essential for maintaining a homeostatic distribution of mitochondria in neurons.
• Disruption of this transport impacts mitochondrial pool health and leads to disparate effects on motor versus sensory circuits.
• This process is conserved and critical for neuronal health, with implications for neurodegenerative diseases.