Mostly Biomathematics Lunchtime Seminar

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Dendrite architecture determine mitochondrial localization patterns in vivo

Speaker: Erin Barnhart, Columbia University

Location: Warren Weaver Hall 1314

Date: Tuesday, October 25, 2022, 12:30 p.m.

Synopsis:

Neuronal function is inextricably linked to neuronal form: dendrite size limits the formation of synaptic connections to a particular receptive field; branching patterns affect dendritic integration of input signals; and axon thickness regulates action potential propagation. Our work suggests that HS neurons in the Drosophila visual system also maintain a dendritic architecture that allows reliable distribution of mitochondria through asymmetrically branched arbors. We present a model in which four simple scaling rules determine steady-state mitochondrial distribution patterns. The first two rules — scaling of mitochondrial transport with dendrite radius and proportional splitting of mitochondria at branch points — relate local mitochondrial motility rates to dendritic branch radii. The third and fourth rules — power law scaling of parent and daughter radii and scaling of trunk thickness with sister subtree size — are morphological rules that determine the architecture of the dendrite. There are many possible forms of these dendritic scaling rules, but only a subset of the rules we examined — scaling of parent-daughter radii at branch points according to Da Vinci's Rule for Trees and sister subtree scaling with trunk thickness proportional to subtree bushiness — predict realistic mitochondrial localization patterns in our model. Our experimental measurements demonstrate that HS dendrites do in fact obey these morphological scaling rules. Altogether, our work suggests that intracellular transport, and the need to distribute mitochondria throughout elaborately branched dendritic arbors, acts as an important constraint on dendrite morphology.