For biolistic transfection of SACs, gold particles (1.0 μm diameter, Bio-Rad), were coated with plasmids encoding tdTomato driven by CMV promoter24. Live retinas were dissected, transected with four radial incisions, flattened with photoreceptor side down, and mounted onto a nitrocellulose filter (Millipore). Gold particles were delivered using a Biolistics Helios Gene gun device (Bio-Rad), and retinas were cultured in Ames medium (Sigma) in an oxygenated incubator heated to 37°C for 12-16 hrs.
