Microscopic Dissection of Ependymal Wall SVZ Tissue for RNA Isolation

SVZ tissue samples were harvested at the level of the mid-septal nucleus from 3 mm thick coronal slice on postnatal days 3, 7 and 14. We chose this level because the germinal matrix is noticeable at this location and is a useful landmark to reproducibly dissect homogenous tissues from all experimental groups. Slices were separated into wax-coated petri dishes containing sterile cold PBS and stabilized with sterile head pins so that the lateral ventricle could be viewed under a dissecting microscope. As shown in the Supplementary Figures 1F,G, we dissected a region of 0.5–1 mm size reflecting the ependymal wall using fine microdissection scissors along the lateral side of both lateral ventricle walls. Immediately after dissection of the tissue, samples were snap frozen in liquid nitrogen and stored it at −80°C, until further processing.