The conditional medaka mutation eyeless uncouples patterning and morphogenesis of the eye.

In early vertebrate eye development, the retinal anlage is specified in the anterior neuroectoderm. During neurulation, the optic vesicles evaginate from the lateral wall of the prosencephalon. Here we describe the temperature-sensitive mutation eyeless in the Japanese medakafish. Marker gene analysis indicates that, whereas, specification of two retinal primordia and proximodistal patterning takes place in the mutant embryo, optic vesicle evagination does not occur and subsequent differentiation of the retinal primordia is not observed. The mutation eyeless thus uncouples patterning and morphogenesis at early steps of retinal development. Temperature-shift experiments indicate a requirement for eyeless activity prior to optic vesicle evagination. Cell transplantation shows that eyeless acts cell autonomously.