Axon-regenerating retinal ganglion cells in adult rats synthesize the cell 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 synthesize cell adhesion/recognition molecules which they possessed during development, retinae were subjected to in situ hybridization with antisense 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 rats. After optic nerve lesion (ONL), the surviving RGCs between 2 and 28 days after ONL continued to express L1. TAG-1 and SC-1 expression, however is lost. In grafted rats, axon-regenerating RGCs express L1 (together with GAP-43) but neither TAG-1 nor SC-1. Thus, axonal regeneration in grafted rats occurs in the presence of L1 (and GAP-43) but in the absence of TAG-1 and SC-1).