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Ontogeny and Plasticity of Adult Hippocampal Neural Stem Cells

We have investigated the ontogenetic origin and the degree of plasticity of adult hippocampal neural stem cells. Wnt1-expressing cells are located at the dorsal aspect of the embryonic neural tube and some of them are predestined to give rise to neural crest stem cells. Whereas the majority of adult hippocampal neural stem cells do not originate from cells that express Wnt1, a subset does express Wnt1 transiently during embryogenesis, as determined in the double transgenic mouse, Wnt1-cre/R26R. Hippocampal stem cells from adult ROSA 26 mice differentiate into chondrocytes, melanocytes (pigment cells) and smooth muscle cells when cocultured with neural crest cells from quail embryos. Neural crest cell-generated stimuli have a short-range of action and are recognized across species. These observations provide evidence for the heterogeneity in the hippocampal neural stem cell pool with regard to Wnt1 expression. Furthermore, they show plasticity and a remarkably wide range of developmental options of adult hippocampal stem cells.