The 1D4 antibody labels outer segments of long double cone but not rod photoreceptors in zebrafish.

In experimental eye research, zebrafish has become a powerful model for human retina disorders. The purpose of the present study is the characterization of antibodies commonly employed in zebrafish models for rod photoreceptor degeneration. The 1D4 monoclonal antibody, developed against bovine rhodopsin, has been widely used in studies addressing structural and functional features of rhodopsin and was reported as an informative marker to stain rod outer segments in both mice and zebrafish. We have used transgenic reporter lines and histologic analysis to determine the photoreceptor types identified by 1D4 and other antibodies in zebrafish. We demonstrate that 1D4, in contrast to what has been reported previously, does not recognize rod outer segments in zebrafish, but instead labels long double cone outer segments consistent with sequence conservation of the respective epitope. As an alternative marker for zebrafish rods, we characterized the monoclonal antibody zpr-3, which was found to stain outer segments of both rods, as well as double cones. Our findings highlight the importance to confirm specificity of antibodies in cross-species experiments for correct interpretation of experimental data. Our findings clarify conflicting published information arising from studies using 1D4 and zpr-3 antibodies in zebrafish.