Wild type and CNP-EGFR mice (P8, n=6 for each phenotype; adult, n=4 for each phenotype) were perfused through the heart with a mixture of 3% paraformaldehyde and 1.25% glutaraldehyde in 0.1M phosphate buffer (PB). Brains were removed and postfixed overnight with the same fixative. Brains were sectioned with a vibratome and stored in 0.1M PB. Before postfixation for 1 hour with 1% osmium tetroxide, slices were washed in 0.1M cacodylate buffer pH7.2. After, brain slices were dehydrated through a series of ethanol solutions (50%, 70%, 85%, 95% and 100%), infiltrated with epoxy resins and flat embedded. Sections with the lateral ventricle and the SVZ were trimmed and mounted on blocks and cut with an ultramicrotome. Ultrathin sections (70–80 nm in thickness) were counterstained with uranyl acetate and lead citrate and analyzed with a TECNAI G2 Spirit Biotwin TEM (FEI, Hillsboro, OR, USA). The images were captured with an AMT XR40 4 megapixel side mounted CCD camera (Danvers, MA, USA) using the electron micrograph montage option. Image processing was performed with Adobe Photoshop using only the brightness and contrast commands. The
