Trio is required for dendritic branching and the formation of filopodia in class III da neurons.

<p>(<b>A,B</b>) Live confocal images of third instar larval dorsal class III and IV da neurons labeled by the F-actin reporter, <i>UAS-GMA</i>, and driven by the <i>ppk-GAL4</i> transgene. Class III da neurons are distinguished by the presence of short, actin-rich dendritic filopodia emanating from the primary branches. The class III ddaA and ddaF neuron cell bodies are indicated by the arrows and for clarity the class III neuron cell bodies and dendrites have been highlighted by a magenta pseudo-color trace overlay. As compared to wild-type controls (<b>A</b>), <i>UAS-trio^RNAi</i> knockdown results in a strong reduction in dendritic branching particularly with respect to the characteristic dendritic filopodia in class III neurons (<b>B</b>). (<b>C</b>) Quantitative analyses of the average number of dendritic terminals reveal significant reductions in branching proximal and distal to the cell body. For these analyses, 100×100 micron boxes were drawn in parallel areas proximal and distal to the cell body in both wild-type and <i>trio^RNAi</i> and the average number of dendritic terminals quantified. Images were taken at 20× magnification and size bar represents 50 microns. The total <i>n</i> value for each neuron and genotype quantified is reported on the bar graph. Statistically significant <i>p</i> values are reported on the graph as follows (** = <i>p</i><0.01; *** = <i>p</i><0.001). Genotypes: <b>WT</b>: <i>UAS-GMA/+;ppk-GAL4</i>/+;+. <b><i>trio^RNAi</i></b>: <i>UAS-GMA/+;ppk-GAL4/+;UAS-trio^RNAi/+</i>.