Transcriptional Characterization of Glioma Neural Stem Cells Diva ...

3.3 Glioma Culture Systems Introduction
bic acid, and PDGF [165]. Thus, the authors suggested that either G144 cells
represented a corrupted three-directional potent state with acquired genetic
changes influencing the lineage choice toward oligodendrocyte commitment,
or that they may have a distinct phenotype more similar to oligodendrocyte
precursor cells than NS cells. To distinguish between these two possibilities,
G144 was tested for the expression of established markers of oligodendrocyte
precursor cells, i.e. Olig2, Sox10, NG2, and PDGFRα prior to and during
differentiation, to find out that G144 cells stably exhibited an oligodendro-
cyte precursor-like phenotype expressing these markers prior to the beginning
of differentiation by growth factor withdrawal. In fact, upon re-examination
based on histopathology and CNPase staining, G144 was shown to have a
significant oligodendrocyte component even though originally diagnosed as a
glioblastoma [404].
In determining whether GNS cells could generate astrocytes, G144 and G179
were observed to undergo a striking change in cell morphology after seven days
from addition of BMP4 and removal of EGF and FGF2, the protocol used for
astrocyte differentiation of NS cells (see Fig 2.9). The majority of cells ex-
pressed high levels of GFAP, although the frequency was much lower for G166,
and cell lines G144 and G179 expressed low levels of the Doublecortin (Dcx) +
neuronal marker. This ensemble of events showed that although GNS cells
retain the capacity to differentiate, efficiency and lineage choice vary dramat-
ically between each line [404].
GFAP is expressed in radial progenitors and radial glia in the developing pri-
mate nervous system, as well as putative NS cells within the adult SVZ and,
specifically, at low levels in human fetal NS cell lines. Since an alternatively
spliced form, GFAPδ, was shown to mark human SVZ astrocytes [432], the
behaviour of the GNS cell lines with respect to GFAPδ was assessed. The
expression level of GFAPδ mRNA was five times greater in G179 than in
G144 and G166, with G179 cells also up-regulating GFAP expression following
BMP treatment and G144 cells remaining, instead, predominantly negative.
Co-expression of GFAPδ, Sox2, and Nestin was specific to G179 cells, which,
together with the ability to generate neuronal-like cells in vitro, are all fea-
tures conserved in adult SVZ astrocytes [443]. The fact that G166 cells lacked
the expression of GFAPδ and oligodendrocyte precursor markers, but differ-
entiated toward GFAP + astrocytes in vitro, suggested similarity to a more
restricted astrocyte precursor. Thus, despite their shared capacity to prolif-
erate in response to EGF and FGF2 and the widespread expression of neural
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