Multipotent Stem Cells in the Embryonic Nervous System

Neural stem cells are multipotent stem cells that have an unlimited capacity to proliferate and self-renew but whose progeny are restricted to the neural lineages. Neural stem cells can generate large numbers of mature neuronal and glial progeny, often through transient amplification of intermediate progenitor pools, similar to the pattern observed in other organ systems (1). Although self-renewal can occur through symmetric cell divisions that generate two identical daughter cells, asymmetric cell divisions that generate a renewable stem cell and a more lineage-restricted daughter cell are a hallmark of stem cells. Cells that do not self-renew indefinitely but that nevertheless proliferate and have the capacity to generate multiple phenotypes are often referred to as multipotential progenitor cells, but they will be included in a broad definition of stem cells for the purposes of this review. Other stem cell-derived precursor populations that are able to proliferate but that have more restricted lineage potential (e.g., glial restricted or neuronal restricted cells) are discussed elsewhere in this volume.