We have studied
ganglioside alterations and their enzymatic basis during the course of neural differentiation of mouse embryonic
carcinoma cell line P19. This cell line can differentiate into neurons and astrocytes on cell aggregation
after treatment with
retinoic acid (RA) or into muscle cells on
dimethyl sulfoxide (
DMSO) treatment. GD3, detected on immunostaining after thin-layer chromatography (TLC) with
monoclonal antibody (MAb) R24, was markedly present in aggregates treated with RA.
GM3 synthase (alpha 2,3-sialyltransferase, SAT-I) in neurons was found to exhibit the highest activity. GD3 synthase (alpha 2,8-sialyltransferase, SAT-II) and GD3 synthase
mRNA, as analyzed by Northern blotting, were also markedly present in aggregates and neurons induced by RA. However, on treatment with
DMSO, which induces muscle cells, there was no change in the level of GD3 synthase activity, and its transcript was hardly detected during the course of muscle differentiation.
GT1b synthase (alpha 2,3-sialyltransferase, SAT-IV) was present at similar levels in undifferentiated cells and aggregates treated with RA, but a higher level was observed in neurons. On the other hand, the level of GQ1b synthase (alpha 2,8-sialyltransferase, SAT-V) in RA-induced aggregates was significantly higher than that in neurons. These results show that RA but not
DMSO induces the expression of GM3, GD3, GT1b and GQ1b synthases, and particularly GD3 synthase
mRNA, in the
ganglioside biosynthetic pathway during the neural differentiation of embryonic
carcinoma P19 cells.