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.
