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 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. 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. While invertebrate model systems including C. elegans and Drosophila have contributed substantially to the understanding of neural stem cell biology, this chapter will focus on the properties of mammalian neural stem cells. 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) will be a part of the discussion on lineage commitment in this chapter, but will also be discussed in greater depth later in this volume.