In Vivo and In Vitro Expression of Gangliosides in Chick Retina Müller Cells

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Abstract
The expression of gangliosides of the lactosylceramide (LC) and of the gangliotetraosylceramide (GTC) series on the surface of cells from the chick neural retina was investigated by double-color indirect immunofluorescence. GD3 was assumed to be representative of LC and was detected using specific monoclonal antibody. GM1 was assumed to be representative of GTC and was detected using the binding of cholera toxin followed by the binding of cholera toxin antibodies. The expression of polysialosylated GTC (polysialosyl-GTC) was detected using the cholera toxin-cholera toxin antibody experimental approach, after conversion of polysialosyl-GTC to GM 1 by treatment of the cells with neuraminidase. In retinas from 6-day-old embryos (R6), most cells (.apprx. 80%) expressed GD3 but not GTC. After culturing for 7 days (R6+7), the expression of GTC was found confined to neuron-like cells; flat cells derived from Muller cells expressed GD3 but were negative for GTC expression. On the other hand, postmiotic Muller cells obtained from 13-day-old embryo (R13) or 1-day-old hatched chick retina (RPl) expressed GD3, GM1 and polysialosyl-GTC but were unable to maintain the expression of these GTCs when kept in culture for several days. According to these results, retinal cells can be defined on the basis of their ganglioside expression as follows (a) retinoblasts, by the expression of GD3; (b) postmitotic neuronal cells, by the expression of GTC; and (c) postmitotic Muller cells, by the expression of GD3 and GTC. In addition, it was concluded that in contrast to retinal neurons, which express GTC in vitro, flat, Muller-derived cells either lack (R6 cell cultures) or are unable to maintain (R13 cell cultures) the expression of GTC, observations suggesting a dependence of these cells of environmental conditions for expression of these gangliosides.