GENES INVOLVED IN FOREBRAIN DEVELOPMENT IN THE ZEBRAFISH, DANIO-RERIO

We identified four zebrafish mutants with defects in forebrain inducti on and patterning during embryogenesis. The four mutants define three genes: masterblind (mbl), silverblick (slb), and knollnase (kas), In m bl embryos, the anterior forebrain acquires posterior forebrain charac teristics: anterior structures such as the eyes, olfactory placodes an d the telencephalon are missing, whereas the epiphysis located in the posterior forebrain is expanded, In slb embryos, the extension of the embryonic axis is initially delayed and eventually followed by a parti al fusion of the eyes, Finally, in kas embryos, separation of the tele ncephalic primordia is incomplete and dorsal midline cells fail to for m a differentiated roof plate, Analysis of the mutant phenotypes indic ates that we have identified genes essential for the specification of the anterior forebrain (mbl), positioning of the eyes (slb) and differ entiation of the roof plate (kas). In an appendix to this study we lis t mutants showing alterations in the size of the eyes and abnormal dif ferentiation of the lenses.