Throughout life, blood cells are continuously formed in the bone marrow, a process known as hematopoiesis. Hematopoiesis relies on several different mediators, and defects in this system may cause severe pathological conditions.

Blood cells are formed by a process known as hematopoiesis, which in adults takes place primarily in the bone marrow. The bone marrow is a spongy, semi-solid tissue that resides inside the bones and is composed of multipotent hematopoietic stem cells, adipose tissue and stroma cells. Various hematopoietic cells at different developmental levels can be identified by their morphology. Megakaryocytes, which produces thrombocytes, are easily recognized by their very large size.

The differentiation of hematopoietic stem cells start with commitment to either the myeloid or the lymphoid lineage. Besides secreted proteins, such as KIT ligand and various interleukins, several transcription factors are orchestrating the hematopoiesis as well.

The myeloid lineage form erythrocytes, mast cells, thrombocytes granulocytes and macrophages. GATA-1 and KLF-1 are transcription factors that regulates the development of mature erythrocytes from progenitor cells by interaction with globin genes, among other. Alteration of GATA-1 expression has been linked to several types of leukemia and anemia. Mutations in the KLF-1 gene are associated with congenital anemia.

The lymphoid lineage form B-cells, T-cells and natural killer cells. IKZF1 is a member of the Ikaros family and is mainly expressed in the hematopoietic and lymphopoietic system. IKZF1 is required for differentiation and maturation of B- and T cells, possibly by involvement in the rearrangement of immunoglobulins and immune receptor genes. Defects of IKZF1 has been detected in patients with acute lymphatic leukemia.

Would you like to learn about the bone marrow proteomics? You can read a summary here or read the full publication by Andersson et al.

References and links

Uhlén et al (2015). Tissue-based map of the human proteome. Science.
PubMed: 25613900 DOI: 10.1126/science.1260419

Image source from Wikipedia by M. Häggström

Charlotte Soläng