Figure 6: Delivery of miRNAs into the substantia nigra with systemic injections of tyrosine-mutant AAV9/3 vectors. (a) Illustration of the vector construct. The double-stranded pre-miRNA sequence for aromatic L-amino acid decarboxylase (AADC) was placed between the GFP and SV40 poly(A) sequences. ITR: inverted terminal repeat; SynI: synapsin I promoter. (b) A coronal mouse brain section showing a high concentration of GFP-immunoreactive cells in the substantia nigra pars compacta (SNc, circled area). (c) An enlarged image of the SNc subjected to double immunostaining shows colocalization of GFP-positive cells (green) and tyrosine hydroxylase (TH-) positive cells (red). ((d)–(g)) Selective inhibition of AADC expression in SNc neurons. AADC immunoreactivity (red) was not detected in the cells that were positive for both GFP (green) and TH (blue) (arrows). TH-positive cells that were GFP-negative displayed AADC immunoreactivity (arrowheads). Scale bars: (b) 2 mm; (c) 100 μm; ((d)–(g)) 20 μm.