Fig. 3

The Tectal Projectome Reveals at Least Seven Different Classes of Projection Neurons (A) Single-cell reconstruction strategy. Crossing BGUG (Brn3c:Gal4;UAS:GFP) fish to Gal4s1013t; elavl3:lyn-tagRFP fish results in stochastic labeling of individual tectal neurons expressing GFP (green), whereas pan-neuronally expressed lyn-tagRFP (magenta) serves as a registration reference channel across different fish. (B) Example z-projection of a single tectal projection neuron labeled with GFP in a fish expressing pan-neuronally lyn-tagRFP. (C) Tracing of the labeled neuron, color-coded with the Strahler number of each point, highlighting arbor terminals. (D) Summary of all neuronal types found (133 projection neurons). Shown is a connectivity matrix revealed by manual annotation of innervated tectal and extra-tectal targets of every neuron subclass (black, innervated; gray, absent). The ordering was determined by hierarchical clustering of the extra-tectal targets. Seven main projection classes can be distinguished (I–VII; the dendrogram is shown in Figure S4A), determined by their main projection targets, with 29 subclasses differing in final target structures (compare the wiring diagram in Figure S5). The number of cells for each subclass is indicated below the table. (E) Cellular atlas of tectal projection neurons, visualized by color-coding every cell by its projection class. (F) Main arborization targets for every main projection class, determined by kernel density estimation of the last 10 points of neurons’ skeletons with Strahler numbers of 1 (leaves) for points outside of the tectum (more detailed information in Figure S4). The scale bar represents 100 μm. See also Figures S4 and S5.