AXON-REGENERATING RETINAL GANGLION-CELLS IN ADULT RATS SYNTHESIZE THECELL-ADHESION MOLECULE L1 BUT NOT TAG-1 OR SC-1

Retinal ganglion cells (RGCs) in rats regenerate axons in the presence of a PNS nerve graft. To determine if axon-regenerating RGCs synthesi ze cell adhesion/recognition molecules which they possessed during dev elopment, retinae were subjected to in situ hybridization with antisen se cRNA probes of L1, TAG-1, and SC-1 (and GAP-43 for comparison). L1 and TAG-1 (and GAP-43) proteins on axons were detected with antibodies . L1,TAG-1, and SC-1 (and Gap-43) mRNAs and L1 and TAG-1 (and Gap-43) proteins were expressed by RGCs in embryonic, postnatal, and adult rat s. After optic nerve lesion (ONL), the surviving RGCs between 2 and 28 days after ONL continue to express L1. TAG-1 and SC-1 expression, how ever, is lost. In grafted rats, axon-regenerating RGCs express L1 (tog ether with GAP-43) but neither TAG-1 nor SC-1. Thus, axonal regenerati on in grafted rats occurs in the presence of L1 (and GAP-43) but in th e absence of TAG-1 and SC-1.