All experimental procedures were approved by the Institutional Animal Care and Use Committee at The Salk Institute for Biological Studies. For the engrafting assay, NPCs infected with lentiviral vector carrying the CAG-GFP reporter construct were dissociated and resuspended in PBS-glucose + ROCK inhibitor, BDNF, ascorbic acid, cAMP, and laminin at 20,000 cells per μl. P14 NOD-SCID pups were anesthetized using ketamine/xylazine (100 mg/kg, 10 mg/kg) and 1 μl of cell suspension was delivered to the DG of the mouse hippocampus in the right hemisphere by stereotaxic surgery. The injection site was determined using the difference between bregma and lambda (d), using the position of the bregma as reference as follows: anteroposterior, −(1/2) × d mm; lateral, −1.6 mm (if d < 1.6) or −1.7 mm; ventral, −1.9 mm (from dura). Then 2 or 4 weeks posttransplantation, animals were anesthetized with ketamine/xylazine and perfused transcardially with 0.9% saline followed by 4% paraformaldehyde. The brain samples were postfixed with 4% paraformaldehyde and equilibrated in 30% sucrose. Coronal sections of 40 μm were prepared with a sliding microtome. Brain sections of one-in-four series
