Compositions and methods for the culturing, propagation, cryopreservation and manipulation of neural progenitor cells (NPC) and pluripotent stem cells (PSC) are provided. The cells exhibit rapid doubling times and can be maintained in vitro for extended periods. Also provided is a method of propagating neural progenitor cells, and a method of transplanting human NPC and/or PSC to a host. The cells can be genetically modified to express a therapeutic agent prior to the transplanting.