MUTATIONS AFFECTING DEVELOPMENT OF THE ZEBRAFISH RETINA

In a large scale screen for genetic defects in zebrafish embryogenesis we identified 49 mutations affecting development of the retina, Based on analysis of living embryos as well as histological sections, we gr ouped the isolated mutations into six phenotypic categories, (1) Mutat ions in three loci result in a loss of wild-type laminar pattern of th e neural retina, (2) Defects in four loci lead to an abnormal specific ation of the eye anlagen, Only one eye frequently forms in this class of mutants, (3) Seven loci predominantly affect development of the out er retinal layers, Mutants in this category display cell loss mainly i n the photoreceptor cell layer. (4) Nine mutations cause retardation o f eye growth without any other obvious abnormalities in the retina, (5 ) A group of twelve mutations is characterized by nonspecific retinal degeneration, (6) Four mutations display retinal degeneration associat ed with a pigmentation defect. Finally, two mutations, one with absenc e of the ventral retina and one with an eye-specific pigmentation defe ct, are not classified in any of the above groups, The identified muta tions affect numerous aspects of eye development, including: specifica tion of the eye anlage, growth rate of the optic cup, establishment of retinal stratification, specification or differentiation of retinal n eurons and formation of the dorsoventral axis in the developing eye.