EXPRESSION OF ZEBRAFISH GATA-3 (GTA3) DURING GASTRULATION AND NEURULATION SUGGESTS A ROLE IN THE SPECIFICATION OF CELL FATE

In order to understand the role of the transcription factor GATA 3 in vertebrate development, we have examined its expression and some aspec ts of its regulation during gastrulation and neurulation in the zebraf ish. The complete coding sequence of the cDNA encoding the zebrafish G ATA 3 homologue, termed gta3, is described. Analysis of expression pat terns by in situ hybridisation shows the gene to be expressed during g astrulation in the ventral region of the embryo which includes tissue fated to form the non-neural ectoderm. By the end of gastrulation, the re is a clear border to the gta3 expression domain that is close to th e edge of the neural plate. Subsequently, gta3 expresses in the pronep hric duct and in defined regions of the central nervous system which i nclude specific cells in each segment of the spinal cord and nuclei in the brain. Double labelling embryos with a probe for gta3 and antibod ies which identify differentiated neurons suggest that gta3 is dynamic ally expressed during the early differentiation phase of a subset of n eurons but not in the terminal phase. Analysis of gta3 expression in d orsalised embryos and in eye and spl mutant embryos indicates that the neural expression of the gene is subject to control by signals from t he mesoderm, including both the notochord and the somites, which influ ence the segmental organisation of expression in the spinal cord.