Diversification of haematopoietic stem cells to specific lineages

Diverse types of blood cell (lineages) are produced from rare haematopoieti c stem cells that reside in the bone marrow. This process, known as haemato poiesis, provides a Valuable model for examining how genetic programs are e stablished and executed in vertebrates, and also how homeostasis of blood f ormation is altered in leukaemias. So, how does an apparently small group o f critical lineage-restricted nuclear regulatory factors specify the divers ity of haematopoietic cells? Recent findings not only indicate how this may be achieved but also show the extraordinary plasticity of tissue stem cell s in vivo.