Fig. 1. Cre-inducible expression of h-αS in the dorsal medulla oblongata of iR26-αS mice.

(A) Gene targeting strategy for the generation of transgenic iR26-αS mice involved insertion of wild-type h-αS cDNA (I) into a Rosa26 targeting vector downstream to a loxP-flanked transcriptional termination (neo/STOP) cassette (II). Following homologous recombination at the murine Rosa26 genomic locus (III), correctly targeted clones contained the neo/STOP cassette and the h-αS DNA sequence adjacent to the endogenous Rosa26 promoter (IV). In mice carrying this transgene, Cre recombinase–dependent excision of the neo/STOP cassette (V) drove the inducible expression of h-αS. (B) Transgenic expression of h-αS in the MO was induced by a unilateral injection of Cre-AAVs into the left vagus nerve. Gene expression was regulated by the human synapsin 1 promoter. (C) Mice were sacrificed at 4 weeks after a vagal injection of 1 × 10¹² gc/ml (black boxes), 2 × 10¹² gc/ml (light blue boxes), or 4 × 10¹² gc/ml (green-brown boxes) of Cre-AAVs. Coronal sections of the MO were immunostained with anti–h-αS. Representative images show titer-dependent h-αS expression (brown staining) at low, medium, and high magnification. Boxes in the low-magnification images encompass an area of the dorsal MO that is shown at medium magnification. Boxes in the medium-magnification images encompass an area of the DMnX that is also shown at high magnification. Scale bars, 500, 200, and 50 μm in low-, medium-, and high-magnification images, respectively.