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We have investigated the differentiation potential of precursor cells within the developing spinal-cord of mice and have shown that spinal cord cells from embryonic day 10 specifically give rise to neurons when plated onto an astrocytic monolayer, Ast-1. These neurons had the morphology of motor neurons and >83% expressed the motor neuron markers choline acetyltransferase, peripherin, calcitonin gene-related peptide, and L-14. By comparison, 93% of cells present on the Ast-1 monolayers were motor neuron-like. Time-lapse analysis revealed that the precursors on the Ast-1 monolayers gave rise to neurons either directly or following a single cell division. Together, these results indicate that precursors in the murine spinal cord can be induced to differentiate into the motor neuron phenotype by factors produced by Ast-1 cells, suggesting that a similar factor(s) produced by cells akin to Ast-1 may regulate motor neuron differentiation vivo.

Neurofilament-containing cells of neuronal morphology from the adult central nervous system were generated de novo. The production of the neurons was found to be optimal under conditions wherein the precursors were initially stimulated with basic fibroblast growth factor. These results indicate the need for discrete epigenetic signals for the proliferation and differentiation of neuronal precursors in the adult mammalian brain.