A human clonal cell line model of differentiating neurons

The human neuroblastoma cell line SK-N-SH and its thrice-subcloned derivative, SY-5Y, are nearly diploid cell lines with high levels of dopamine β-hydroxylase, a key enzyme in adrenergic neurotransmitter synthesis. The SY-5Y subclone also displays a neuroblast-like morphology in cell culture and in the undifferentiated state does not have electrically excitable membranes. In this study the response of the SY-5Y cells to the nerve growth factor protein, NGF, is described. After 5 days in culture in the presence of NGF, the SY-5Y cells extended neurites, ceased multiplying, and aggregated into clumps similar to those observed in primary cultures of sympathetic ganglia treated with NGF. Ultrastructural analysis of the induced processes showed them to be neurites. Whereas NGF treatment inhibited the incorporation of [³H]thymidine into DNA and inhibited cellular proliferation, it stimulated incorporation of³H-amino acids into protein. Further analysis of these differentiated cells showed them to have developed electrically excitable membranes. Undifferentiated cells were selectively killed by 6-hydroxydopamine, whereas NGF treatment led to protection of the differentiated cells from 6-hydroxydopamine killing. Treatment of the SY-5Y clone with dibutyryl cyclic AMP induced neurite outgrowth and enhanced electrical excitability but did not lead to protection from 6-hydroxydopamine killing. The morphological response of the SY-5Y cells to dibutyryl cyclic AMP was quite different from that observed after NGF treatment. We propose the SY-5Y clone as a model for the study of the regulation of NGF-induced differentiation in neuronal cells.