In vivo imaging of mitochondria in intact zebrafish larvae

Visualizing neuronal mitochondria in a living, intact mammalian organism is a challenge that can be overcome in zebrafish larvae, which are highly accessible for optical imaging and genetic manipulation. Here, we detail an approach to visualize neuronal mitochondria in sensory Rohon-Beard axons, which allows quantitatively measuring mitochondrial shape, dynamics, and transport in vivo. This provides a useful assay for basic studies exploring the behavior of neuronal mitochondria in their natural habitat, for revealing the influence that disease-related alterations have on this behavior and for testing pharmacological compounds and genetic manipulations that might ameliorate disease-related mitochondrial phenotypes in neurons.