Regulation of Gata1 gene expression levels during erythroid cell development

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Transcription factor GATA-1 is the master regulator of erythroid cell differentiation. Expression level of the Gata1 gene changes dynamically during erythroid differentiation, and this change is essential for the proper erythropoiesis. To investigate the molecular mechanism how Gata1 gene expression changes during the erythroid lineage development, we established a novel reporter transgenic mouse system utilizing bacterial artificial chromosome containing the Gata1 gene (Gata1-BAC). In the Gata1-BAC transgenic mice, reporter gene expression faithfully recapitulates temporal and spatial expression of the Gata1 gene in a copy number-dependent but integration position-independent manner. Since the core region (235 bp) of Gata1 gene hematopoietic enhancer (G1HE), which localizes at 3.9-kbp upstream of erythroid specific IE first exon, is highly conserved between human and mouse and appeared to be important in our plasmid transgenic mouse experiments, we analyzed reporter transgenic mouse lines harboring the G1HE-Core-deficient BAC reporter transgene. Results demonstrated that G1HE-Core is essential for up-regulation of the Gata1 gene throughout the erythroid differentiation. Especially, in the absence of G1HE-Core, the expression of Gata1 is abrogated in early erythroid progenitor (EEP) stage, which corresponds to BFU-E, and in erythroblasts. On the contrary, there remains G1HE-Core-independent expression of the Gata1 gene in late erythroid progenitor (LEP) stage, which contains to CFU-E and proerythroblasts. Mutational analyses further revealed that the conserved GATA-box in G1HE-Core is essential for this enhancer activity. Thus, analyses with the Gata1-BAC reporter transgenic mouse lines demonstrate for the first time that G1HE-Core directs the stage-specific expression of the Gata1 gene in vivo.