Abstract
To study the cellular heterogeneity of astrocytes from early postnatal mouse cerebellum in culture, Bergmann glia were enriched by hand-dissection of Purkinje, molecular and external granular layers (‘outer’ layer) and fibrous astrocytes of white matter and deep cerebellar nuclei (‘inner’ layer). Both populations of GFA protein and vimentin-positive astrocytes express N-CAM and the L2/HNK-1 epitope, but not tetanus toxin receptors or A2B5 antigen, at levels detectable by indirect immunofluorescence procedures. The two astrocyte populations are thus indistinguishable from each other. Expression of tetanus toxin receptors and A2B5 antigen in these astrocytes can, however, be induced by removal of neurons. The expression of tetanus toxin receptors is again reduced by readdition of purified populations of small cerebellar neurons. Morphology and proliferation of astrocytes from both layers is also dependent on the presence of neurons: removal of neurons leads to an epithelioid, rather than star-shaped morphology and a severalfold increase in proliferation. Readdition of neurons induces astrocytes to return to their star-shaped morphology. Epidermal growth factor increases proliferation in both populations of astrocytes. We conclude that neither antigenic marker profile, morphology nor proliferative responses serve to distinguish between enriched Bergmann glia and enriched fibrous astrocytes.