Molecular Analysis of the MN1 Oncogene and the Leukemia-Associated Fusion Gene MN1-TEL

The word hematopoiesis comes from the ancient Greek; haima translates to 'blood' and poiesis means 'to make': hematopoiesis describes the formation and development of bloods cells. Different types of blood cells are recognized. Red blood cells, the erythrocytes, are important for transport of oxygen throughout the body, white blood cells, B and T-lymphocytes, are crucial for the immune response and granulocytes and monocytes are important for responses against infections. Platelets, which form clots to stop bleeding, are also formed by hematopoiesis.1 Hematopoiesis is an intriguing process that continuously supplies the organism of new blood cells for its complete lifespan. In humans, the first primitive blood cells are formed in the blood island of the yolk sac (2 to 8 weeks of development).2 This is followed by blood cell formation in the fetal liver and the spleen. At five months of development the bone marrow is the site of production of blood cells and it continues to do so throughout life. The cells from the hematopoietic system are generated from the self-renewing hematopoietic stem cells (HSC) that reside mainly in the bone marrow.3,4,5 HSCs are divided in long-term (LT)-HSC and short-term (ST)-HSC (Figure 1). LT-HSC are slow-dividing cell populations that contain self-renewing cells that sustain long-term hematopoiesis, divide a-symmetrically, and form ST-HSC. These cells are faster-dividing cell populations with limited self-renewal potentials and are more committed, ready-to-differentiate and produce the progeny of the different lineages. ST-HSC differentiate into nonself-renewing multipotent progenitors (MPP). This cell type differentiates into two oligolineage progenitors, the common myeloid progenitor (CMP) or common lymphoid progenitor (CLP). T-cells, natural killer (NK)-cells and B-cells are formed from the CLPs. CMPs differentiate into either megakaryotic/erythoid progenitors (MEP) that produce erythrocytes and platelets or granulocyte/monocyte progenitors (GMP). Dendritic cells are produced either from CMPs or CLPs.