GM1 ganglioside as a marker for neuronal differentiation in mouse cerebellum

The distribution of GM1 ganglioside in developing mouse cerebellum was monitored by indirect immunofluorescent detection of choleragenoid receptors. In frozen sections of cerebellum from mice 5 to 10 days old, fluorescence is observed on granule cells in the inner rows of the external granular layer, in the growing molecular layer, the Purkinje cell layer, and the internal granular layer. In sections of adult mice, fluorescence is restricted to the bodies of Purkinje and internal granule neurons. The percentage of fluorescent dissociated or cultured cerebellar cells increases with the postnatal age of the mouse or the duration of time in vitro. No fluorescence is observed in the absence of choleragenoid or if the test material is extracted with chloroform:methanol. To determine whether the expression of surface GM1 ganglioside in culture is a reflection of a developmental program, mice are injected at particular times with [³H]thymidine and cerebellar cultures processed for simultaneous autoradiography and immunofluorescence. Granule cells from 8-day-old mice having cholera toxin receptors at 20 hr in vitro are a distinct population born 1 day or earlier prior to sacrifice. Cells synthesizing DNA on the day of sacrifice are not fluorescent at 20 hr in vitro. This observation correlates well with immunohistological results showing a lack of fluorescence in the outer proliferative rows of the external granular layer. Therefore GM1 ganglioside is not present on granule cell precursors but is expressed at some time after the cells become postmitotic. GM1 ganglioside is detected on growing parallel fibers in situ and neurites in vitro but not on adult axons, suggesting differential localization at a later stage of development.