Cholera toxin binds to differentiating neurons in the developing murine basal ganglia

Cell-surface expression of gangliosides in the developing mammalian central nervous system is temporally-regulated in a cell-type and regionally specific fashion. Gangliosides may be involved in cell-cell and cell-matrix interactions, and can act synergystically with several growth factors or growth factor receptors. Thus, a role for gangliosides in the regulation of neuronal stem cell proliferation and differentiation has been suggested. We have previously shown that cholera toxin B subunit (CTB), which binds to the ganglioside GM1, binds heterogeneously to dissociated neuroepithelial cells from the developing mouse telencephalon. We stained fixed sections of the ganglionic eminences (GE) of fetal mouse brains and found that CTB labels regions which contain differentiating neurons, but does not stain the rapidly dividing neuroepithelial cells in the ventricular zone. We dissociated cells from the GE on day 14 of gestation (E14), labeled the cells with CTB-FITC, and separated them by flow cytometry. We found the highest level of CTB binding in postmitotic cells which had begun to express markers of neuronal differentiation. When CTB-sorted cells were placed into short-term (48 h) cell culture, high CTB binding continued to correlate with fewer numbers of proliferating cells and larger numbers of differentiating neurons. CTB binding and fluorescence activated cell sorting appear to be useful for separating populations of differentiating neurons from immature, proliferating cells. These studies further lead us to suggest that GM1 plays a role in the differentiation of neurons in the basal ganglia.