Animals were perfused with 4% paraformaldehyde in 0.1 M PB. Brains were fixed for an additional 18 hr at 4°C. Brains were then cryoprotected in 20% (w/v) sucrose in PBS at 4°C overnight. Brains were embedded in OCT and 25-μm cryosections were cut using the tape transfer method. For direct imaging of XFP, sections were DAPI stained and coverslipped as above. For single-label immunofluorescence, sections were incubated for 30 min at room temperature in PBS containing 0.3% Triton X-100 and 5% normal goat serum (NGS). Sections were incubated with anti- GFP (Abcam; 1:1000 dilution) overnight at 4°C. Sections were rinsed for 30 min in PBS containing 1% NGS, incubated in goat anti-rabbit IgG-Alexa Fluor 488 (Invitrogen; 1:400 dilution) for 2 hr at room temperature, rinsed for 10 min in PBS containing 1% NGS, and rinsed for 30 min in PBS. Sections were then DAPI stained and coverslipped as above. XFP or IHC imaging was identical to the DFISH automated fluorescence microscopy method.