A retroviral vector containing sh-miR-137 under a U6 promoter and EGFP under a chicken actin promoter was prepared, and the virus containing the construct was injected into the dentate gyrus of adult mice in vivo. BrdU was injected twice/day (50,g/kg i.p.) for a total of 7 injections beginning immediately after viral grafting. After 1 week, animals were anesthetized, perfused with 4% paraformaldehyde, brains removed and postfixed, equilibrated in 30% sucrose, and sectioned at a thickness of 40µm with a sliding microtome. Infected cells were localized using chicken-α-GFP (Invitrogen) and rat-α-BrdU (Abcam), secondaries were α-chicken Alexa Fluor 488 and goat-α-rat Alexa Fluor 647 (both from Invitrogen). Confocal z-stacks were acquired at 1 µm steps using a Nikon TE2000 with equipped with a spinning disc confocal with an oil immersion 40X 1.3 NA objective (Zeiss). For additional details see: J. Cell Biol. Vol. 189:127–141.