Editor's Summary
26 April 2007
Something in the blood
There are two recognized phases of blood formation (haematopoiesis) during embryonic development: an initial 'primitive' stage that takes place in the extraembryonic yolk sac and provides nutrients to the early embryo, then a 'definitive' stage that begins in a region of the embryo known as the aorta-gonad-mesonephros. There has been prolonged debate over whether the source of the definitive haematopoietic population is local or external, deriving from inwardly migrating precursors from the yolk sac. A new non-invasive cell tracing study contradicts the current orthodoxy and suggests that the yolk sac is indeed the source of adult haematopoietic stem cells. Knowledge of the origins of the blood supply is relevant to work on the generation of blood stem cells in culture, with the potential for therapeutic applications.
News and Views: Stem cells: Blood lines from embryo to adult
Does blood formation in mammalian embryos and adults have separate origins or a common source? The most recent investigations into the question add a further chapter to this long-running story.
Hiroo Ueno & Irving L. Weissman
doi:10.1038/446996a
Article: Cell tracing shows the contribution of the yolk sac to adult haematopoiesis
Igor M. Samokhvalov, Natalia I. Samokhvalova & Shin-ichi Nishikawa
doi:10.1038/nature05725
Abstract | Full Text | PDF (921K) | Supplementary information
