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Megakaryocytes

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Derived from hematopoietic stem cells, like all blood cells.

The hematopoietic stem cells give rise to the megakaryocyte-erythroid progenitor (MEP).

The MEPs are bi-potential precursors give rise to both megakaryocytic and erythroid lines.

There are multiple transcription factors that form complex networks that regulate and differentiate megakaryocytes both positively and negatively.

Generate platelets by a process that requires membrane and cytoskeletal reorganization.

During differentiation the megakaryocyte progenitor switches from mitosis to endomitosis corresponding to DNA replication and leading to formation of a giant cell with a single polylobulated nucleus with a 2N ploidy.

Megakaryocytes give rise to platelets by branching, budding, and release of pro platelet appendages.

Ploidization increases megakaryocyte cytoplasm volume and increases the mass of platelets that arise from cytoplasm fragmentation.

Late stage megakaryocyte maturation extend tubulin rich branches with pod-like tips which are pinched off under actin-mediated contractile forces and physiological shear to form platelets.

Transcription factors include Runx1, Gata 1, Fli1 and c-Myb.

As these cells differentiate been loose there proliferative ability and become polypoid.

During the process of differentiation diploid promegakaryicytes give rise to tetraploid cells and then become successively larger.

Mature megakaryocytes can be 150 ┬Ámol per liter or more in diameter.

Megakaryocytes are the largest hematopoietic cells in the bone marrow.

A defining feature of these cells is polyploidization, which facilitates protein and membrane synthesis required for platelet production.

There is some correlation between the megakaryocyte ploidy and platelet production.

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