AGRIN GENE-EXPRESSION IN CILIARY GANGLION NEURONS FOLLOWING PREGANGLIONIC DENERVATION AND POSTGANGLIONIC AXOTOMY

Agrin is an extracellular matrix protein that has been implicated as a synaptogenic agent in the peripheral and central nervous systems. Bot h the level of expression and pattern of alternative splicing of agrin mRNA are developmentally regulated. As a step toward identifying sign als important in regulating agrin gene expression in neurons, we exami ned the effects of postganglionic axotomy or preganglionic denervation on agrin mRNA levels and alternative splicing in ciliary ganglia of p osthatch chicks. In comparison to unoperated age-matched controls, in situ hybridization with a pan-specific agrin cRNA probe demonstrated a significant decrease in neuronal agrin mRNA expression as a result of axotomy. Reverse transcription-polymerase chain reaction analysis dem onstrated that axotomy also resulted in changes in the pattern of alte rnative splicing of agrin mRNA. Underlying these changes are decreases in the molar amounts of transcripts encoding the neuron-specific isof orms agrin8 and agrin19, homologous to rat agrin proteins that have hi gh AChR aggregating activity. Similar, but less dramatic changes in ag rin expression following axotomy were also observed in unoperated neur ons on the contralateral side. In contrast, the only significant chang e in agrin gene expression following ganglionic denervation was a smal l decline in the relative abundance of agrin 8 mRNA in operated versus unoperated age-matched control ganglia. Major changes in agrin gene e xpression following axotomy but not denervation are consistant with th e notion that agrin synthesized by ganglionic neurons exerts its effec ts in the periphery rather than at synapses formed between ciliary gan glion neurons and their preganglionic input. These data suggest that t he pattern of alternative splicing and the absolute amount of agrin mR NA in ciliary ganglion neurons may be regulated by target tissue inter actions. (C) 1995 Academic Press, Inc.