Development of heraatopoietic cells in the embryonic aortagonad-mesonephros region is dependent on the amount of the PEBP2/CBF transcription factor

We recently reported that hematopoietic progenitors and their derivative cells can be propagated in vitro by culluring cells derived from the aorta-gonadmesoncphros (AGM) region of day 11.5 mouse embryos (Mukouyama, et al.. Immunity 8, 105-114, 1998). By using this culture system, we examine in this study the expression of AML1 and PEBP2β/CBFβ proteins in these cells and also evaluate the effect of mutations in these genes on the generation of hematopoietic cells. The AML1 and PEBP2pVCBFβ proteins encode the subunits of the heterodimeric transcription factor, PEBP2/CBF, and are known (o be indispensable for the development of definitive hematopoiesis in the fetal liver Positive immunostaining of AMI ,1 and PEBP2pVCBFβ proteins was delectedin the nuclei ot most of the cell types appearing in the AGM cultures which were prepared from wild type embryos. In contrast, no hematopoietic cells were generated from the AGM culture of cells with either the AMU(-/-) or PEBP2βCBFβ(-/-) genotype. In the case of AGM cultures preparedfrom the AMLJ(+t-) or PEBP2β/CBFβ(+/-) embryos, CFU-C activities were significantly reduced compared to those of wild type AGM cultures The results indicate that the lack of definitive hematopoiesis in the hver of AMU(-i-) and PEBP2/CBF(-l-) embryos is due to the impairment of hematopoietic progenitors in the AGM region and that the development of progenitors is dependenton the amounts of the two subunits of the PEBP2/CBF transcription factor.