Expression of netrin-1 and its receptors DCC and UNC-5H2 after axotomy andduring regeneration of adult rat retinal ganglion cells

Netrins are a family of chemotropic factors that guide axon outgrowth durin g development; however, their function in the adult CNS remains to be estab lished. We examined the expression of the netrin receptors DCC and UNC5H2 i n adult rat retinal ganglion cells (RGCs) after grafting a peripheral nerve (PN) to the transected optic nerve and following optic nerve transection a lone. In situ hybridization revealed that both Dec and Unc5h2 mRNAs are exp ressed by normal adult RGCs. In addition, netrin-1 was found to be constitu tively expressed by RGCs. Quantitative analysis using in situ hybridization demonstrated that both Dec and Unc5h2 were down-regulated by RGCs followin g axotomy. In the presence of an attached PN graft, Dec and Unc5h2 were sim ilarly down-regulated in surviving RGCs regardless of their success in rege nerating an axon. Northern blot analysis demonstrated expression of netrin- 1 in both optic and sciatic nerve, and Western blot analysis revealed the p resence of netrin protein in both nerves. Immunohistochemical analysis indi cated that netrin protein was closely associated with glial cells in the op tic nerve. These results suggest that netrin-1, DCC, and UNC5H2 may contrib ute to regulating the regenerative capacity of adult RGCs. a zool Academic Press.