NEURONAL AND GLIAL EPITOPES AND TRANSMITTER-SYNTHESIZING ENZYMES APPEAR IN PARALLEL WITH MEMBRANE EXCITABILITY DURING NEUROBLASTOMA X GLIOMA HYBRID DIFFERENTIATION

The membrane excitability and the presence of neural proteins, includi ng neuronal and glial markers and neurotransmitter-synthesizing enzyme s, were examined in parallel while the NG108-15 cell line was maintain ed in a serum-free medium. Whole-cell recordings in voltage-clamp or c urrent-clamp configurations were used to evaluate the membrane excitab ility, and immunostaining was done with a panel of well-characterized antibodies against NSE, NF150, S-100 beta, GFAP, ChAT and TH. Culture for 4 to 10 days led to a striking rise in neurite outgrowth, electric al excitability and expression of neural proteins in type I neuron-lik e cells, which were of both neuronal and glial character, and expresse d both cholinergic and adrenergic traits. After about 2 weeks, type II cells which lack neurite processes began to emerge. The type II cells proliferated, as revealed by BrdU uptake, and gradually overgrew diff erentiated cell types. They exhibited little or no membrane excitabili ty and absence of immunoreactivity for the neuronal and glial specific proteins tested. These measurements indicate that the presence of the se neural proteins at crucial stages of membrane excitability developm ent is an important characteristic of NG108-15 cell differentiation, p roviding insights into the neural development and the reversible natur e of neoplasia in the nervous system. (C) 1998 Elsevier Science B.V.