Dendritic mitochondrial transport in mature neurons is important for motor skill learning

Mitochondrial trafficking is essential for neuronal development as well as for maintenance of functional mitochondrial pools at synaptic terminals. Nevertheless, the relevance of this process for mature neurons and the mechanisms governing the inherent motility of mitochondria across neuronal compartments remains unknown. By imaging mitochondrial transport in developing Purkinje neurons (PN) in situ, we observed progressive the formation of stable pools in the distal regions of dendrites, while larger dendritic calibers and axonal shaft kept a considerable extent of organelle motility up and beyond 1 year of age. Abrogation of mitochondria motility via deletion of the motor adaptor protein Miro1 in mature PN did not alter neuronal viability but led to opposite changes in neuronal compartments. While axonal segments retained seemingly intact mitochondria, the prolonged absence of mitochondria transport led to changes in cytosolic Ca2+ activity and aberrations in cristae structures in dendrites by 1 year of age. This phenomenon correlated with deficits in motor learning skills observed in mice. Altogether, while our findings underscore the dispensability of mitochondrial transport for neuronal viability in mature PN, they also highlight its crucial role in synaptic activity regulation.