Building brains: Neural chimeras in the study of nervous system development and repair

The ability to isolate multipotential neuroepithelial precursor cells from the mammalian nervous system provides exciting perspectives for the in vitr o analysis of early nervous system development and the generation of donor cells for neural repair, New models are needed to study the properties of t hese cells in vivo. Neural chimeras have revealed a remarkable degree of pl asticity in the developmental potential of neuroepithelial precursor cells. Following transplantation into the cerebral ventricle of embryonic hosts, precursors derived from various brain regions and developmental stages part icipate in host brain development and undergo region-specific differentiati on into neurons and glia,These findings indicate that in the developing ner vous system, migration and differentiation of neural precursors cells are r egulated to a large extent by extrinsic signals, Neural chimeras composed o f genetically modified cells will permit the study of the molecular mechani sms underlying these guidance cues, which may eventually be exploited for c ell replacement strategies in the adult brain. A key problem in neural tran splantation is the availability of suitable donor tissue, Neural chimeras c omposed of embryonic stem (ES) cell-derived neurons and glia depict ES cell s as a versatile and virtually unlimited donor source for neural repair, Ge neration of interspecies neural chimeras composed of human and rodent cells facilitates the translation of these advances into clinical strategies for human nervous system repair.