Distinct Roles of Microtubules and Actin Filaments in Defining Dendritic Architecture

Abstract

Microtubules and F-actin have long been recognized as key regulators of dendritic morphology. Nevertheless, precisely ascertaining their distinct influences on dendritic trees have been hampered until now by the lack of direct, arbor-wide cytoskeletal quantification. We pair live confocal imaging of fluorescently labeled dendritic arborization (da) neurons in drosophila larvae with complete multi-signal neural tracing to separately measure microtubules and F-actin. We demonstrate that dendritic arbor length is highly dependent on local microtubule quantity, whereas local F-actin enrichment is associated with dendritic branching. Computational simulation of arbor structure solely constrained by experimentally observed subcellular distributions of these cytoskeletal components generated synthetic morphological and molecular patterns statistically equivalent to those of real da neurons, corroborating the sufficiency of local microtubule and F-actin in defining dendritic architecture. The analysis and modeling outcomes hold true for the simplest (Class I), most complex (Class IV), and genetically altered (Formin3 overexpression) da neuron types.