ZEBRAFISH RETINAL MUTANTS

We have initiated a genetic analysis of the zebrafish visual system to identify novel molecules involved in vertebrate retinal function. Zeb rafish are highly visual; they have four types of cones as well as rod photoreceptors, making it possible to study both rod and cone-mediate d visual responses. To identify visual mutants, optokinetic responses of mutagenized larvae are measured in a three-generation screen for re cessive mutations. By measuring visual behavior our genetic screen has been targeted towards identifying mutants that do not have gross morp hological abnormalities. The electroretinogram (ERG) of optokinetic-de fective mutants is recorded and their retinas are examined histologica lly to localize defects to the retina. In this report, we summarize ou r screening results and ERG and histological analyses of the five morp hologically normal mutants we have analyzed to date. Additionally, the more detailed characterization of a red-blind mutant that we have iso lated is summarized. Our results indicate that mutants with defects in various processes such as photoreceptor synaptic transmission, photor eceptor adaptation and cell-type specific survival and/or function can be identified using this approach. (C) 1998 Published by Elsevier Sci ence Ltd. All rights reserved.