DIFFERENTIAL REGULATION OF THE 2 XGATA-1 GENES DURING XENOPUS DEVELOPMENT

Xenopus laevis provides an established developmental system to study t he regulation of cell lineage establishment and the generation of tiss ue-specific patterns of gene expression. We have isolated from Xenopus erythroid cell RNA two distinct cDNA clones encoding the xGATA-1 tran scription factor. We have identified, in erythroid nuclear extracts, t he sequence-specific DNA-binding protein they encode. By characterizin g the expression patterns for RNA derived from two distinct homologues , we find that the two xGATA-1 genes are differentially regulated. The xGATA-1a mRNA predominates in embryos prior to terminal differentiati on of erythroid cells, while the differentiated cells contain RNA deri ved predominantly from the xGATA-1b gene. Both proteins activate a tar get globin promoter in transient transfection assays. During early dev elopment, GATA-1 transcripts are localized to ventral regions of the e mbryo. GATA-1 should therefore provide a useful early marker for study ing signalling pathways which result in the generation of ventral meso derm. The differentially regulated genes may be distinct markers for t argets of ventral mesoderm induction.