Journal of Neuroscience, Vol 3, 806-817, Copyright © 1983 by Society for Neuroscience
Ganglioside composition is regulated during differentiation in the neuroblastoma X glioma hybrid cell line NG108-15
NM Dahms and RL Schnaar
Cellular differentiation of the neuroblastoma X glioma hybrid cell line
NG108-15 was measured and correlated with quantitative changes in the
cells' ganglioside composition. The degree of differentiation was measured
using an enzymatic marker, choline acetyltransferase (CAT), which is
responsible for neurotransmitter synthesis in this cell line.
Differentiation of these cells is commonly induced by agents such as
dibutyryl cyclic adenosine 3':5'-monophosphate (Bt2cAMP). However, in our
studies, we observed that these cells "self-differentiated," in the absence
of chemical inducers, when the cells became dense in culture. The
differentiation marker, CAT specific activity, rose from 150 to more than
400 pmol/min/mg of protein as cell density increased, attaining a level
higher than that achieved by treatment with Bt2cAMP. Differentiation of
sparse cultures could be induced by conditioned medium removed from dense
cultures. This effect was not due to depletion of a serum component from
the medium by the cells, since it was not mimicked by serum depletion or
inhibited by addition of fresh serum to the conditioned medium. These data
suggest that cell density- dependent differentiation was caused by release
of a factor from the cells which induced differentiation in a
concentration-dependent manner. Gangliosides, therefore, were purified from
sparse control cultures, dense cultures, and cultures treated with the
differentiating agents Bt2cAMP, prostaglandin E1 (plus theophylline), or
butyric acid. Quantitative thin layer chromatography revealed that all of
the cultures contained the four gangliosides GM3, GM2, GM1, and GD1a. The
concentration of one of the gangliosides, GM2, increased markedly (up to
12-fold) during differentiation. The GM2 concentration correlated closely
with the level of CAT activity in the different cultures (r = 0.99). These
data demonstrate that the ganglioside concentration in these cells is
regulated during differentiation, a finding consistent with a possible role
for gangliosides in the differentiated phenotype.
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