Peripapillary glial cells in the chick retina: A special glial cell type expressing astrocyte, radial glia, neuron, and oligodendrocyte markers throughout development.

Peripapillary glial cells of the chick are a special type of glia, not only because of their position, forming a boundary between the retina on one side and the optic nerve head (ONH) and the pecten on the other, but also because although they have the same orientation and similar shape as the retinal Müller cell (a type of radial glia) and express common markers for these cells and astrocytes, they do not express glutamine synthetase (GS) or carbonic anhydrase C (CA-C), enzymes intensely expressed by Müller cells and astrocytes. In this study, we present further molecular characterization of these cells, using immunohistochemistry techniques. We show that peripapillary glial cells express a novel neuron antigen, 3BA8, that in the adult retina is located only in one neuron type (the amacrine cell) and in the inner plexiform layer (IPL).