Role of the coagulation system in development.

The generation of knock out mice urged researchers, not always voluntarily, to newly define developmental functions of the gene knocked out. Among others, this has led to the establishment of the field of developmental haemostasis. The work in this field identified a role of coagulation proteases and their regulators independent of haemostasis in the embryo proper. Rather, coagulation proteases regulate cellular function through receptor dependent signalling in the embryo proper, both within and outside the vasculature. Likewise, coagulation proteases modulate placental development independent of haemostasis through mechanisms involving the activation of maternal myeloid derived cells. The following review summarizes the current knowledge in the field of developmental haemostasis and pinpoints open questions within this evolving field.