DIFFERENT FORMS OF THE NEUROTROPHIN RECEPTOR TRKB MESSENGER-RNA PREDOMINATE IN RAT RETINA AND OPTIC-NERVE

The expression of TrkB mRNAs was investigated in rat retina and optic nerve. A 11.5 kb transcript that encodes full-length TRKB was found to predominate in Northern blots of retinal RNA. By in situ hybridizatio n, this trkB expression was concentrated in the ganglion cell and inne r nuclear layers. Furthermore, an antibody to the full-length TRKB imm unostained retinal ganglion cells and their axons. In contrast, Northe rn blots of optic nerve RNA showed a prominent 9.5 kb band that encode d a form of the TRKB receptor lacking the tyrosine kinase domain. This species was also detected in both the sciatic nerve and cultured astr ocytes and C6 glioma cells. These results suggest that neurons express the full-length TRKB containing the tyrosine kinase domain, while non -neuronal cells express the truncated form of the receptor. These two classes of TRKB may mediate different neurotrophic actions in the reti na and optic nerve. (C) 1993 John Wiley & Sons, Inc.