Markers of differentiation in glial cells

Cell Biology

732

MARKERS Margaret Garscube

OF

International

DIFFERENTIATION

glioma lines Lineweaver-Burk of glutamate

used, indicating low affinity affinity [Km The high affinity to competitive Demonstration and specific prove useful tion in these

tested showed plots, within concentrations

the presence of both (Km 0.3 - O.SmM) and high 30 - SOpMl uptake mechanisms. mechanism is sensitive inhibition by aspartate. of high affinity transport may inhibition by aspartate as a marker of differentiacells. Of the other cell

types tested, only melanoma lines ed the presence of two different ity mechanisms of uptake. Foetal Intestine (FHI) cells, 3T3 mouse fibroblasts and NRC-5 human diploid fibroblasts gave rise to monoph,asic weaver-Burk affinity Another

plots mechanism cell line

with for [GNSI

showaffinHuman

Line-

only a lbw glutamate uptake. which was derived

from a human astrocytoma but was thought to be predominantly endotheli 1 from "\ morphological evidence, its loss of GFAP positive cells with passage number, and its high level of alkaline phosphatase. also showed only a low affinity glutamate uptake system. All the glial lines tested and some glioma lines have both tligh and low affinity mechanisms of GABA uptake. In some cases the presence of the high affinity system was only evident after treatment of the cells with known inducers of glial differentiation.such as dibutyrylcyclic AMP (in the absence of serum) or B-methasone. These observations

0309-I

IN

GLIAL

Frame, R.I. Freshney, R. Shaw The Beatson Institute for Cancer Estate, Switchback Road, Bearsden,

The kinetics of uptake of glutamate and y-aminobutyric acid [GABA) by normal glia and glioma cell lines have been used as marker properties of differentiation. With respect to glutamate uptake,all glia and biphasic the range

Reports, Vol. 4, No. 8, August

651/80/080732-01/.$02.00/0

1980

CELLS

and 0.1. Research, Glasgow,

Graham G61

180.

imply that high affinity transport of putative neurotransmitter amino acids may be restricted to neurectodermal cells. Glial fibrillarv acidic protein (GFAPI has been shown to-be a specific marker for astroglia and can be demonstrated in both normal amd malignant glia, in viva and --in vitro. GFAP was induced spontaneously in cultures of human and mouse foetal brain. It is also present in rat Cg glioma cultures, being maximally expressed in early stationary phase cultures. This increase in GFAP production coincides with the onset of cell - cell contact and density dependent inhibition of proliferation. Induction of GFAP in Cg cultures above control values can be achieved by agents such as isoproterenol, dibutyryl-cyclic AMP and dexamethasone with maximal induction being obtained using a combination of the5e agents. The protein synthesis inhibitor, cycloheximide, and the transcriptional inhibitor, actinomycin 0, both prevent this induced increase in GFAP. It may be possible to exploit these marker properties of glial cells (with the help of inducing agents) in future studies of differentiation and malignancy in cultures of normal glia and glial tumours. Acknowledgements The work was supported by grants from the Medical Research Council, The Cancer Research Campaign and the Scottish Home and Health Oepartment. Nrs.Frame is supported be a CASE [SRC) Studentship in collaboration with Dr.R.C.Imrie of Beechams Research Laboratories.

01980

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