Antiserum to a new neuronal growth factor: effects on neurite outgrowth.

A new neuronal growth factor (CMF) isolated from mouse heart-cell-conditioned medium stimulates morphologic and biochemical development of mouse embryo sympathetic neurons [Coughlin et al, 1981]. Further analysis of CMF by chromatographic and electrophoretic procedures has shown that under nondissociating conditions, CMF activity is associated with very high molecular weight material. All biological activity eluted within the included volume of a Sepharose CL-2B column in a molecular weight range corresponding to approximately 5 X 10(6) daltons. Similarly, electrophoresis showed no activity and very little protein entering 3% polyacrylamide gels, whereas both protein and activity migrated through 0.6% agarose-1.2% acrylamide composite gels. To further characterize the biological effects of CMF on normal neuronal development, antibodies to CMF were employed. Rabbits immunized against CMF developed high titres of antibodies with activity specifically directed against CMF (anti-CMF). Although anti-CMF inhibited nerve growth factor (NGF)-stimulated neurite outgrowth from the neonatal superior cervical ganglion, it did not inhibit the NGF-stimulated increase in tyrosine hydroxylase activity. Moreover, ganglia incubated for 3 days in the presence of anti-CMF were subsequently capable of producing neurites when washed and cultured in medium free of antiserum. Thus, anti-CMF specifically blocked neurite extension without causing cell death or irreversible damage in ganglionic explants. Our observations suggest, therefore, that CMF or antigenically similar material is a requirement for neurite extension.