Differential regulation of the two xGATA-1 genes during Xenopus development.

Xenopus laevis provides an established developmental system to study the regulation of cell lineage establishment and the generation of tissue-specific patterns of gene expression. We have isolated from Xenopus erythroid cell RNA two distinct cDNA clones encoding the xGATA-1 transcription factor. We have identified, in erythroid nuclear extracts, the sequence-specific DNA-binding protein they encode. By characterizing 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 differentiation of erythroid cells, while the differentiated cells contain RNA derived predominantly from the xGATA-1b gene. Both proteins activate a target globin promoter in transient transfection assays. During early development, GATA-1 transcripts are localized to ventral regions of the embryo. GATA-1 should therefore provide a useful early marker for studying signalling pathways which result in the generation of ventral mesoderm. The differentially regulated genes may be distinct markers for targets of ventral mesoderm induction.