HoxA3 is an apical regulator of haemogenic endothelium

In the developing mouse embryo, a region of the dorsal aorta endothelium generates haematopoietic cells, but how the switch to endothelium or haematopoiesis is controlled has been unclear. HoxA3 induces endothelial differentiation through repression of key haematopoietic transcription factors, including Runx1, and is downregulated during haematopoietic differentiation.