Hematopoietic stem cells are at the foundation of the blood system. Their study is not only relevant to the understanding of the basic cellular mechanisms of self-renewal, lineage commitment, and differentiation, but they have also been the target of intense clinical research into the causes of leukemia and the exploitation of these cells for cell replacement therapies. The basic mechanisms of hematopoietic stem cell regulation become evident in the way these cells are first generated and expanded during development. Isolating and analyzing hematopoietic stem cells from the embryo is therefore of direct clinical importance.
