The primitive streak gene Mixl1 is required for efficient haematopoiesis and BMP4-induced ventral mesoderm patterning in differentiating ES cells

Abstract

The homeobox gene Mixl1 is expressed in the primitive streak of the gastrulating embryo, and marks cells destined to form mesoderm and endoderm. The role of Mixl1 in development of haematopoietic mesoderm was investigated by analysing the differentiation of ES cells in which GFP was targeted to one (Mixl1GFP/w) or both (Mixl1GFP/GFP) alleles of the Mixl1 locus. In either case, GFP was transiently expressed, with over 80% of cells in day 4 embryoid bodies (EBs) being GFP+. Up to 45% of Mixl1GFP/w day 4 EB cells co-expressed GFP and the haemangioblast marker FLK1, and this doubly-positive population was enriched for blast colony forming cells (BL-CFCs). Mixl1-null ES cells, however, displayed ..