Synucleins in ocular tissues.

Synucleins are small proteins associated with neurodegenerative diseases and some forms of cancer. Most studies of this group of proteins have been directed to the elucidation of their role in the brain and their connection to the formation of depositions in brain tissues. Here we describe the localization of different types of synucleins in ocular tissues. By Western blot analysis, all members of the synuclein family are found in the retina and optic nerve, where their relative ratio varies. The data on immunohistochemical staining show that different members of the synuclein family have different localizations in ocular tissues. Alpha-synucleins and beta-synucleins are present predominantly in the inner plexiform layer, whereas gamma-synuclein is in the nerve fiber layer. In transgenic mice overexpressing alpha-synuclein, a different pattern of localization depending on the promoter used for the expression was observed. In Alzheimer's disease patients, immunohistochemical staining for gamma-synuclein revealed the loss of immunoreactivity in the nerve fiber layer and the nerve fiber layer and the appearance of immunopositive cells in or near the outer nuclear layer. We conclude that, in mature eyes, synucleins are present predominantly in the retina and optic nerve, and the immunoreactivity of gamma-synuclein changes specifically in the retina of Alzheimer's disease patients. In transgenic mice overexpressing alpha-synuclein, immunopositive deposits in the optic nerve and accumulation of immunoreactivity in specific retinal cells were found.