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Previous studies have demonstrated that GATA-1 deficient embryonic stem cells fail to produce mature red blood cells either in vivo or in vitro, though GATA-1 is known to be expressed in other hematopoietic cells. To gain further insight into the role of GATA-1 in early erythropoiesis, characteristics of the differentiating GATA-1-deficient embryonic stem (ES) cells in a simple suspension culture were monitored for their hematopoietic differentiation potential and for expressivity of several erythroid marker genes. The data showed that definitive erythropoietic lineage cells failed to mature beyond the proerythroblast stage from the colonies derived from the differentiating GATA-1-deficient ES cells, while all other hematopoietic lineage cell types were generated efficiently. Interestingly, βH1, the first β-type globin to appear in the primitive erythroid cells, initiated its expression normally but the expression was not maintained afterwards in the differentiating GATA-1 deficient ES cells, while the other β-type globins were not expressed at all. All other tested erythroid messages were expressed normally. The data suggests that GATA-1 is critical for the maintenance of relatively early erythropoiesis, but not for the onset of either primitive or definitive erythropoiesis, nor even for the onset of βh1-globin expression in primitive erythroid cells.
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