Quantifying Retinal Projections in Reelin Mutants

Intraocular injection of cholera toxin subunit B (CTB) conjugated to AlexaFluor488 or AlexaFluor 594 (Invitrogen) was performed as described previously (Jaubert-Miazza et al. 2005 (link)). After 1–2 days, mice were euthanized and brains fixed in 4% paraformaldehyde. 80–100µm coronal sections were sectioned on a vibratome and mounted in ProLong Gold (Invitrogen). Retinal projections were analyzed from at least 5 animals for each age and genotype. Images were acquired on a Leica SP2 confocal microscope. To quantify the spatial extent of vLGN and IGL innervation by retinal axons, serial coronal sections encompassing the entire LGN (~14–18 80 µm sections) were obtained and imaged from 6 P12 reln^rl/rl mutants and 6 littermate controls (for example see serial sections shown in Supplemental Figure S4). Measurements of the entire LGN area and the area of retinal innervation to vLGN and IGL in mutants and controls were obtained using AxioVision software.