A dominant form of inherited retinal degeneration caused by a non-photoreceptor cell-specific mutation

We have isolated a dominant mutation, night blindness a (nba), that causes a slow retinal degeneration in zebrafish. Heterozygous nba fish have normal vision through 2–3 months of age but subsequently become night blind. By 9.5 months of age, visual sensitivity of affected fish may be decreased more than two log units, or 100-fold, as measured behaviorally. Electroretinographic (ERG) thresholds of mutant fish are also raised significantly, and the ERG b-wave shows a delayed implicit time. These defects are due primarily to a late-onset photoreceptor cell degeneration involving initially the rods but eventually the cones as well. Homozygous nba fish display an early-onset neuronal degeneration throughout the retina and elsewhere in the central nervous system. As a result, animals develop with small eyes and die by 4–5 days postfertilization (pf). These latter data indicate that the mutation affecting nba fish is not in a photoreceptor cell-specific gene.