Mitochondria are distributed throughout the neuron and perform important functions like ATP production, calcium buffering and regulation of apoptosis. Mitochondria are enriched at synapses and its trafficking is known to be dependent on both cytosolic and mitochondrial calcium. In the touch receptor neurons (TRNs) of adult C. elegans, we see that mitochondria are uniformly distributed and this uniform distribution is achieved as the animal transitions from larval stage 1 (L1) to larval stage 2 (L2). We also observe that mitochondria are positioned such that the median distance between two adjacent mitochondria is ~20 mum. How this mitochondrial distribution is established and maintained and what roles do axonal mitochondria play, both remain unknown. Prior studies demonstrated that >80% of mitochondria along the neuronal processes are localized at F-actin-rich regions suggesting that an actin dependent mechanism might play a role in axonal mitochondrial distribution. Indeed, our data reveal that the transition to uniform mitochondrial distribution correlates with a change in F-actin dynamics and the distribution of actin-rich regions in TRN processes between L1 and L2 stages. To investigate the interplay between actin and mitochondria in more detail, we assessed both the role of mitochondria on neuronal actin and the role of actin on neuronal mitochondrial distribution. In
ric-7 mutants that lack mitochondria in the neuronal process, actin dynamics is altered that is restored upon artificially driving mitochondria into
ric-7 neuronal processes. Additionally, in the absence of actin-rich regions achieved by the expression of DeAct (Disassembly-promoting, encodable Actin tool) in TRNs decreases the distance between adjacent mitochondria and affects mitochondrial transport properties. Upon photo stimulation of the neuron we see that mitochondria along the axonal process buffer cytosolic calcium in a MCU-1 dependent manner. Additionally, we found that the presence of mitochondria, F-actin-rich regions and MCU-1 mediated calcium uptake all modulate calcium dynamics upon photo stimulation as well as the touch responsiveness of the animal. These data suggest that axonal mitochondria plays a role in regulating actin dynamics in the neurons and both mitochondria and actin dynamics are important for modulating touch responsiveness.