Neurite extension factor induces rapid morphological differentiation of mouse neuroblastoma cells in defined medium.

The present study describes an in vitro bioassay for neurite-promoting factors using a mouse neuroblastoma cell line (Neuro-2A) in defined medium at low cell density. Neurite extension factor (NEF) is a disulfide-bonded dimer of a protein closely related to S100 beta, a calcium-binding protein made by glial cells. NEF induces process outgrowth from chick embryo cerebral cortical neurons. We now report that NEF induces rapid morphological differentiation of Neuro-2A cells. Within 4-6 h of addition of NEF, the cells elaborate multipolar neurites and the cell body becomes rounded. In the absence of NEF, the cells do not extend neurites and the cell body appears flattened. This response is dose-dependent, with half-maximal stimulation at a concentration of about 300 ng/ml (15 nM) of NEF. This completely defined system should be useful for characterizing NEF receptors and studying the mechanism of action of NEF.