DISTRIBUTION OF AGRIN MESSENGER-RNAS IN THE CHICK-EMBRYO NERVOUS-SYSTEM

Agrin is a synapse-organizing protein likely to mediate nerve-induced aggregation of acetylcholine receptors and other postsynaptic componen ts at the neuromuscular junction. We used in situ hybridization and po lymerase chain reaction (PCR) to define the localization of agrin mRNA and its alternatively spliced forms in the chick embryo nervous syste m. Agrin cRNA probes intensely labeled motor neurons, dorsal root gang lia, cerebellar Purkinje neurons, and retinal ganglion cells. Neuronal layers in optic tectum and ventricular regions were also labeled. Ana lysis by PCR showed that all parts of the nervous system at embryonic day 10 contained three major forms of agrin mRNA. Our results raise th e possibility that agrin isoforms play a role in synapse formation or other aspects of neuronal development in the central nervous system.