Figure 2

Expression of dominant-negative forms of Unc5a in the chick hindbrain causes BM axon pathfinding errors. (A-G) Flat-mount chick hindbrains that have been electroporated with plasmids encoding myristylated GFP (myr-GFP) or dominant-negative Unc5a (DN-Unc5a), as labelled. Immunostaining with anti-GFP (green) and anti-Islet1/2 (red) antibodies. In controls, axons in r5 grow rostrally and correctly towards exit point (orange arrow in (A)). In DN-Unc5a-expressing embryos some axons also pathfind normally (orange arrow in (D)), whereas some axons in r5 turn caudally (arrowheads in (B,C)). Some DN-Unc5a-expressing BM axons are orientated at an angle to the floor plate rather than perpendicularly (arrowheads in (E)). DN-Unc5a-expressing BM neuron cell bodies are found ectopically within the floor plate (pink arrowheads in (F,G)) and produce multiple branches (white arrowheads in (F,G)). Inset in (F) shows cell body with higher Islet-1/2 immunofluorescence. fp, floor plate. Scale bar: 50 μm (A,B); 25 μm (C-E); 20 μm (F,G).