Development of Thy-1 antigen on cerebellar neurons in culture.

The Thy-1.1 cell surface antigen was demonstrated by indirect immunofluorescence on two types of neurons in dissociated cell cultures of developing rat cerebellum. In cultures from postnatal rats, small cells predominated. They bound tetanus toxin, a neuronal marker, and did not have the capacity to take up gamma-aminobutyric acid (GABA) as measured by autoradiography. From these properties, we conclude that they are granule cells. These neurons began to express the surface antigen Thy-1.1 by 2 weeks in culture, and by 4 weeks, the antigen was detected on about 40% of all of the surviving neurons. The second type of neuron, which may be a heterogeneous mixture of cerebellar neurons, was numerous only in cultures prepared from embryonic rats. They were larger than granule cells and expressed Thy-1.1 antigen after a few days in culture. Such cells bound tetanus toxin and were negative for the glial markers galactocerebroside and glial fibrillary acidic protein. Thy-1-positive cells and cells with high GABA uptake were most frequent in embryonic day 19 cultures, where 40 to 50% of all of the neurons were positive for either property. They survived about 1 week in culture. The size and frequency of Thy-1 cells and the frequency of similar cells with high GABA uptake suggest that the embryonic rat cultures included many Purkinje cells, which express Thy-1.