RP2 dendrite screen – phenotypic categories. Rows show examples representing the main phenotypic categories recovered from the central (RP2) neuron dendrite misexpression screen. Left and centre columns: confocal images (maximal Z-projections) of RP2 neurons at 25–31 hours AEL, visualised with UAS-mCD8::GFP. (a) Control RP2 neuron with brackets indicating the dendritic tree. (b) Control RP2 neuron in the context of a set of axon tracts visualised by anti-FasciclinII staining (magenta), with arrowheads pointing from top to bottom to the lateral, intermediate and medial FasciclinII tracts and the midline indicated by a dotted line. Dendrites between the lateral and central intermediate Fasciclin II fascicle are defined as 'lateral'; dendrites located between the central intermediate fascicle and the midline as 'medial'; the same applies to (o,p). (c) Same neuron as in (b) but with sectors of its dendritic tree pseudo-coloured to highlight branches targeted to anterior lateral (magenta), anterior medial (yellow) and posterior lateral (cyan) regions. Anterior is left and the ventral midline is down. (d,e,g,h,i,j,l,m,o,p) Experimental cells: misexpression lines are indicated in the bottom right-hand corner of each panel. Right column: (f,k,n,q) quantifications of the dendritic phenotypes shown in the left and central columns. As illustrated in (f), both dendritic tree length and number of branching events are reduced in the 'Growth' and 'Branching' categories. 'Branching' phenotypes have trees with an anterior-posterior extent comparable to controls (Additional file 2) but have an altered pattern of branching: fewer branching events and more segments that are longer (>5 μm). *P < 0.01, **P < 0.005, t-test, N = 5. Error bars indicate the standard error. Arrows in (b,o,p) point to medial branches present in controls (b) and absent/reduced in experiments (o,p). Black asterisks in (e,p) indicate the cell body of the contralateral RP2 neuron. Scale bar: 10 μm.