HEMATOPOIESIS Identification and characterization of 2 types of erythroid progenitors that express GATA-1 at distinct levels

for the development of the erythroid lin-eage. To ascertain whether strict control of GATA-1 expression level is necessary for achieving proper erythropoiesis, we established transgenic mouse lines ex-pressing green fluorescent protein (GFP) under the control of the GATA-1 gene hematopoietic regulatory domain. We ex-amined the GATA-1 expression level by exploiting the transgenic mice and found 2 GFP-positive hematopoietic progenitor fractions in the bone marrow. One is the GFPhigh fraction containing mainly CFU-E and proerythroblasts, which coexpress transferrin receptor, while the other is the GFPlow/transferrin receptor–negative frac-tion containing BFU-E. Since the intensity of green fluorescence correlates well with the expression level of GATA-1, these results indicate that GATA-1 is highly expressed in erythroid colony-forming unit (CFU-E) but low in erythroid burst-forming unit (BFU-E), suggesting that the incremental expression of GATA-1 is re-quired for the formation of erythroid pro-genitors. We also examined GFP-positive fractions in the transgenic mouse spleen and fetal liver and identified fractions containing BFU-E and CFU-E, respec-tively. This study also presents an effi-cient method for enriching the CFU-E and BFU-E from mouse hematopoietic tis-sues. (Blood. 2003;102:3575-3583) © 2003 by The American Society of Hematolog