Fig. 4
Morphological analysis of neurons labeled by dg4ii plasmid. (A) Approach used to determine laminar targeting of neurites in the tectal neuropil. Image of pou4f3:gfp fluorescence, which labels a subset of RGC axons that target the SO and the two deepest sublayers of the SFGS. This signal was used to determine the relative thickness of the SO and SFGS layers, which receive the vast majority of retinal afferents. (B) Maximum projection of a confocal image volume obtained from a single tectal neuron at 5 dpf labeled by blastomere injection of dg4ii and uas:dsred plasmids. Note the single apical neurite that gives rise to a compact arbor lacking an efferent projection. (C) Forty-five degree rotation of 3D volume rendering performed on image stack in B reveals precise stratification of two distinct arbors. (D) Cut-view at the same 45° orientation as in (C) demonstrates the roughly 45° orientation of the apical dendrite. (E) A merged image of cut-view in (D; red) and pou4f3:gfp fluorescence (green) reveals that the superficial arbor targets the SFGS layer, whereas the deeper arbor targets the SGC layer below the SFGS. Scale bar, 50 μm in (A), 25 μm in (B–E).