RETINOIC ACID IS NECESSARY FOR DEVELOPMENT OF THE VENTRAL RETINA IN ZEBRAFISH

In the embryonic zebrafish retina, as in other vertebrates, retinoic a cid is synthesized from retinaldehyde by two different dehydrogenases, one localized dorsally, the other primarily ventrally. Early in eye d evelopment only the ventral enzyme is present. Citral competitively in hibits the ventral enzyme in vitro and decreases the production of ret inoic acid in the ventral retina in vivo. Treatment of neurula-stage z ebrafish embryos with citral during the formation of the eye primordia results in eyes lacking a ventral retina. This defect can be partiall y rescued by retinoic acid. The results demonstrate that synthesis of retinoic acid can be selectively inhibited in vivo and suggest that re tinoic acid is necessary for the proper development of the ventral ret ina.