Figure 4: Transduction of spinal cord motor neurons. Immunohistochemical detection of GFP and choline acetyl transferase (ChAT), a motor neuron marker, in mice spinal cords following intracardiac injections of tyrosine-mutant AAV9/3 vectors that expressed GFP under control of the synapsin I promoter. (a) An axial section demonstrating colabeling of GFP (green) and ChAT (red) in the large ventral horn neurons of the spinal cord. ((b)–(d)) High magnification images of the square area outlined in (a). (b) GFP-positive cells (green); (c) ChAT-positive cells (red); and (d) the merged image of ((b) and (c)). Scale bars: (a) 100 μm; ((b)–(d)) 20 μm.