Augmin complex components control branching of sensory neuron dendrites in <em>Drosophila</em> larvae

Abstract

Microtubule is the major architectural element to support proper neuronal structure. It is tightly organized with intrinsic polarity and affects not only neuronal morphology but also the transport property within the cell. In many cell types, the centrosome component γ-<em>tubulin</em> is the principal microtubule nucleator. However, the mechanism underlying neuronal microtubule nucleation and organization remains unknown. During neuronal development, the centrosome is inactivated and microtubule nucleation becomes acentrosomal. Whether the microtubule centrosomal-independent nucleation contributes to the establishment of polarity in neurons remains unclear and essential to answer. <br /> The purpose of this work is to reveal whether Augmin mediated microtubule nucleation plays a role in building up proper dendritic morphology and organizing dendritic microtubule polarity. To this purpose, I analyzed the dendrite morphology of class IV ddaC da neurons in Drosophila larvae carrying mutations for γ-<em>tubulin</em> and Augmin. I found that dendritic morphology and dendrite branch dynamics were changed in γ-<em>tubulin</em>, <em>dgt5</em>, <em>dgt6</em> (Augmin) and <em>Dgp71WD</em> (γ-TuRC) mutants. Interestingly, the phenotypes of these various mutants were similar, suggesting the possibility that they might act in concert. To test this possibility, I performed genetic interaction experiments between <em>γtub23C</em>, <em>dgt5</em>, <em>dgt6</em> and <em>Dgp71WD</em> and found these molecules play coordinate roles in dendrite morphology. In Augmin complex mutant neurons, the localization of fluorescently tagged α-<em>tubulin</em> and the microtubule minusend marker Nod were both altered, suggesting a role of Augmin in microtubule organization in these neurons. Taken together, my work suggests a role of the Augmin complex in the proper organization of microtubules in neuronal dendrites, which is important for achieving dendritic complexity in <em>Drosophila</em> PNS class IV da neuron.