Single cells transitioning to hematopoietic fate in vivo show pulsatile Gata2 expression

Cell fate is established through coordinated gene expression programs in individual cells. Regulatory networks that include the Gata2 transcription factor play central roles in hematopoietic fate establishment. Whereas Gata2 is essential to the embryonic development and function of hematopoietic stem cells that form the adult hierarchy, little is known of the in vivo expression dynamics of Gata2 in single cells. Here we examine Gata2 expression in single aortic cells as they establish hematopoietic fate in Gata2Venus mouse embryos. Time-lapse imaging reveals rapid pulsatile level changes in Gata2 reporter expression in cells undergoing endothelial-to-hematopoietic-transition. Moreover, Gata2 reporter pulsatile expression is dramatically altered in Gata2+/- aortic cells, which undergo fewer transitions and are reduced in hematopoietic potential. Our novel finding of dynamic pulsatile expression of Gata2 suggests a highly unstable genetic state in single cells concomitant with their transition to hematopoietic fate. This reinforces the notion that threshold levels of Gata2 influence fate establishment and has implications for transcription factor-related hematologic dysfunctions. Overall design: At embryonic day 10.5, HP/SC populations (CD31+ckit+) were sorted into Gata2Venus high and intermediate populations.