Specific optic nerve proteins during regeneration of the goldfish retinotectal pathway

A cluster of proteins originally detected in the goldfish optic tectum is found in high concentration in the optic nerve. When the proteins are solubilized in sodium dodecylsulfate and analyzed by two-dimensional gel electrophoresis, a well resolved linear array is observed. The optic nerve proteins are designated here as ON1, ON2, ON3 and ON4. Proteins ON1 and ON2 can be further resolved into components (ON1a + ON1b) and (ON2a + ON2b), respectively. ON1a and ON2a are specific to the goldfish retinotectal pathway in that they are not found in brain areas which do not receive retinal inputs. The effect of optic nerve disconnection on the concentration of the ON proteins was investigated. A large decrease in the levels of ON1 and ON2 is observed within 5 days of optic nerve crush and their concentration is restored to normal levels during the regeneration process. In contrast, the concentration of ON3 and ON4 is stable following optic nerve disconnection. It is suggested that ON1 and ON2 originate from the retina and that they are located in the axons of the optic nerve while ON3 and ON4 are of non-neuronal origin. These proteins which are prominent in the optic nerve are compared to previously reported tectal proteins. Their cellular origin and the possibility that they may be associated with the neurofilament complex is discussed.