The distribution of tenascin-R in the developing avian nervous system.

Tenascin-R is an extracellular matrix glycoprotein found in the developing central nervous system. In vitro, tenascin-R promotes axon growth. In order to learn more about the function and regulation of tenascin-R in neural development, we have used monoclonal antibodies to localize tenascin-R immunoreactivity in the developing and adult chicken brain. The earliest stage stained with anti-tenascin-R was embryonic day 6.5, when the matrix surrounding the cell bodies of spinal cord motoneurons was stained. At embryonic day 18, specific brain regions were stained, including the basal nuclei, habenular nuclei, layer "i" of the optic tectum, and the motor nuclei of cranial nerves. Anti-tenascin-R staining persisted in these regions in the adult chicken brain. Thus, the distribution of tenascin-R immunoreactivity in the developing and mature avian brain is correlated with the distribution of nerve growth factor (NGF)-sensitive neurons, but it is not correlated with neurite outgrowth. Finally, NGF was shown to upregulate tenascin-R expression in PC12 cells, indicating that expression of neuron-derived tenascin-R may be regulated by exogenous NGF.