Differentiation of oligodendrocytes cultured from developing rat brain is enhanced by exogenous GM3 ganglioside

Abstract

Cultures consisting primarily of O-2A progenitor cells and immature oligodendrocytes with a few microglia and astrocytes were obtained by shaking primary cultures from neonatal rat brain after 12-14 days in vitro. Addition of 50 micrograms/ml exogenous Neu-NAc alpha 2-3Gal beta 1-4Glc beta 1-1'ceramide (GM3 ganglioside) to the cultures resulted in an increase in the number and thickness of cell processes that stained intensely for sulfatide and galactocerebroside (galC) in comparison to control cultures without added GM3. The treated cultures also contained fewer astrocytes than control cultures as revealed by immunostaining for glial fibrillary acidic protein (GFAP). Cells that immunostained for both GFAP and sulfatide/galC were very rare in control cultures but were frequently seen in the GM3-treated cultures, suggesting that these may represent cells changing their direction of differentiation away from type II astrocytes toward oligodendrocytes under the influence of GM3. These effects on the developing rat oligodendrocytes were specific for GM3 ganglioside and were not produced by adding GM1, GM2, GD3, or GD1a to the cultures. Lactosyl ceramide and neuraminyl lactose were also ineffective. When control cultures were initially plated on polylysine and incubated with [14C]galactose, GD3 was the principal labeled ganglioside. However, as the control cells differentiated over time in culture without the addition of exogenous GM3 and produced increasing amounts of myelin-related components, the incorporation of [14C]galactose into endogenous GM3 increased to become the predominant labeled ganglioside by 6 days after plating. Metabolic labeling of the GM3-treated oligodendrocytes with [14C]galactose revealed increased incorporation into galC and sulfatide in comparison to control cultures, but a decreased labeling of endogenous GM3. Similarly, incorporation of an amino acid precursor into the myelin-associated glycoprotein (MAG) was increased by GM3 treatment, but incorporation into myelin basic protein (MBP) was not affected. Although the overall effect of added GM3 was to decrease the phosphorylation of most proteins in the oligodendrocytes, including MBP, GM3 enhanced the phosphorylation of MAG. These findings indicate that GM3 ganglioside has an important role in the differentiation of cells of the O-2A lineage toward myelin production, since differentiation is associated with increased metabolic labeling of endogenous GM3 in control cultures and is enhanced by the addition of exogenous GM3.

Negative Regulation of Oligodendrocyte Differentiation by Galactosphingolipids

“…oligodendrocyte differentiation and myelination by acting as sensors/transmitters of environmental information" (Bansal et al, 1988;. This hypothesis has been supported by our findings using anti-galactolipid antibody perturbation and biochemical inhibition of sulfatide synthesis (Bansal et al, 1988;Pfeiffer, 1989, 1994a,b) (this report), as well as by a number of other observations related to the role of not only galactolipids but also gangliosides (for review, see Bansal et al, 1988;Coetzee et al, 1998;e.g., Diaz et al, 1978;Dorfman et al, 1979;Ranscht et al, 1982Ranscht et al, , 1987Dyer and Benjamins, 1988;Pettmann et al, 1988;Wu and Ledeen, 1991;Yim et al, 1994). These studies demonstrate that the interaction of these galactolipids with the environment leads to biological responses.…”

The pathogenesis of primary progressive multiple sclerosis: antibody-mediated attack and no repair?

“…One possible immune mechanism for inhibiting remyelination is the action of antiGM3 antibodies which are elevated in the sera of patients with primary progressive MS; 35 these antibodies might interfere with the important role that GM3 ganglioside has in the differentiation of oligodendrocyte progenitors toward myelin production. 45 …”

Characterization of initiated cells in N-methylnitrosourea-induced carcinogenesis of the CNS in the adult rat

“…Previous data support the concept that glial multipotent progenitor cells coexpress mature glial markers when stimulated. For example, GFAP and GalC are coexpressed in O-2A cells (Yim et al, 1994). Addition of db-cAMP to primary cultures of glial cells from adult rat olfactory bulb results in the coexpression of GalC and GFAP (Bakardjiev, 1997).…”