Identification and characterization of neural specific molecules in the zebrafish retina

Understanding the mechanisms of neural development and function requires the identification and characterization of the molecular components involved. My thesis work has concentrated on identifying and characterizing two proteins specific for the zebrafish retina. I have generated a panel of monoclonal antibodies against zebrafish embryonic neural tissues. The most interesting one (7A11) of these monoclonal antibodies, which recognizes an antigen expressed specifically in the zebrafish retina, was characterized in detail. The 7A11 antibody first stains retinal ganglion cells about 37 hours after fertilization, and later it also stains the inner plexiform layer and the inner nuclear layer. In the adult retina it stains only the inner plexiform layer and amacrine cells. On immunoblots the 7A11 antibody stains a doublet around 70 kD, under non-reducing condition. The 7A11 antigens are sensitive to reducing reagents and to trypsin digestion, suggesting that they are proteins. And detergent phase separation experiments indicate they are membrane proteins. Considering their expression pattern and developmental regulation, it is tempting to speculate that the 7A11 antigens play a role in the histogenesis of the inner plexiform layer, or in the axon outgrowth and navigation of retinal ganglion cells. I have also identified and cloned the gene for a 30 kD protein, ES1, which is abundant in and specific to the zebrafish retina. The ES1 protein has no sequence similarity to other proteins except to an E. coli protein with an unknown function. ES1 mRNA and protein are expressed exclusively in cone photoreceptor cells of the adult retina. The ES1 protein seems to be a cytoplasmic protein. An ES1-like molecule is also detected in photoreceptor cells of goldfish. Although the function of the ES1 protein remains to be determined, it may be important in maintaining retina structure and function.