SPECIFIC CELLULAR-LOCALIZATION OF TYROSINASE MESSENGER-RNA DURING CIONA-INTESTINALIS LARVAL DEVELOPMENT

A Ciona intestinalis cDNA clone that encodes a protein highly homologo us to other tyrosinases was isolated. Northern blot analysis showed th at expression of Ciona tyrosinase starts at the early neurula stage an d continues throughout the tail-bud and tadpole larval stages. The ear liest tyrosinase expression was detected, by in situ hybridization, at the neural plate stage, in pigment precursor cells located along the two neural folds, in the animal region of the embryo. In the course of embryonic development the strong hybridization signal was always loca lized, within the rostral part of the developing brain, in the pigment precursor cells and was later detected in the otolith and ocellus. Th ese results are discussed in relation to tyrosinase as an early marker of neural induction.