MULTIPLE FACTORS CONTROL THE PROLIFERATION AND DIFFERENTIATION OF RATEARLY EMBRYONIC (DAY-9) NEUROEPITHELIAL CELLS

The proliferation and differentiation of neural precursor cells is lar gely controlled by environmental factors. By providing the factors tha t favor the proliferation or suppress the differentiation of this cell type, we isolated and expanded an early neuroepithelial predifferenti ated cell type from E9 rat neural plate in serum-free medium. This has led to the establishment of a neural epithelial precursor (NEP) cell line. The NEP cell's properties are substantially different from those of cell lines previously derived from neural tissue at later stages o f development. Initial selection and survival of this cell type requir es a factor secreted by an embryonic Schwann (nrESC) cell line. Contin ued passage of these cells requires cell-cell contact for both surviva l and growth. Neural cell differentiation can be induced in this nesti n positive precursor cell line by bFGF and forskolin. General neuronal markers, as well as cortical neuron-specific protein kinase C isozyme , and accumulation of glutamate and aspartate were induced in most cel ls. Choline acetyl-transferase was also induced in a small number of c ells. When implanted into neonatal rat brain, the NEP cell line gave r ise to several distinct neuronal and glial phenotypes in different reg ions of the brain including cerebellar cortex and hippocampus.