Endothelial cell–neural stem cell cocultures. Neural stem cells from wild-type mice were cocultured in transwells for 7 days with equal numbers of endothelial cells from survivin^+/+ (A-B) or survivin^+/− (C-D) mice, as described in “Materials and methods.” Adherent neural cells were coimmunostained for nestin (A,C) and RC-2 (B,D). Shown is a representative microscopic field, which indicates that there are approximately 2-fold more undifferentiated neural stem cells after coculture with survivin^+/+ endothelial cells.