Cells were trypsinized and washed in L-15 medium containing 100 IU/ml DNase I (Roche) and concentrated via centrifugation at 600 g for 3 min. Newborn severe combined immunodeficient (SCID) mice (n = 8–10) regardless of sex were used as recipients for each experiment. P1-2 SCID recipients were anesthetized by hypothermia until pedal reflex disappeared, and subsequently placed on a stereotaxic platform. Concentrated cells (~1,000,000 cells/μl) were loaded into a beveled glass micropipette (Drummond Scientific), and two injections of 0.1 μl each were delivered into the forebrain of the recipient at 2.0 mm posterior, 1.4 mm lateral, 0.8 mm deep (targeting the subventricular zone) and 2.0 mm posterior, 1.4 mm lateral, 0.5 mm deep (targeting the cortex). The coordinates were zeroed anteriorly at the inner corner of the eye, laterally at the midpoint between the eyes and vertically at the skin surface. After the injections, recipients were placed on a heating pad until warm and active and returned to their mothers until weaning at P21. All animal experiments for the present study were performed with approval of the Stanford IACUC.
