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A megakaryoblast () is a precursor cell to a promegakaryocyte. During thrombopoiesis, the promegakaryocyte matures into the form of a megakaryocyte. From the megakaryocyte, are formed. (2025). 9780198836612, Oxford University Press. ISBN 9780198836612 The megakaryoblast is the beginning of the thrombocytic series or platelet forming series.
Megakaryoblasts typically have a large oval-shaped Cell nucleus or a nucleus that is Lobation with Multinucleate. The megakaryoblast resembles the myeloblast or lymphoblast morphologically; however the megakaryoblast varies in phenotype and the structure viewed with electron microscopy. (2025). 9780702031472, Churchill Livingstone/Elsevier. ISBN 9780702031472
Increased amounts of megakaryoblasts in the bone marrow may indicate a disease state. (2025). 9783136731024, Thieme. ISBN 9783136731024 An example of this is acute megakaryoblastic leukemia, which occurs when the level of megakaryoblasts in the bone marrow exceeds 20%.
The megakaryoblast is derived from colony forming units (CFU-Meg) of hematopoietic stem cells found in red bone marrow. There are found on the surface of hemopoietic stem cells that are used as identifiers for megakaryoblasts and other . Two of the committed biomarkers are CD34- and CD150+. (2025). 9780128098431, Elsevier. ISBN 9780128098431 The CFU-Meg, which forms megakaryoblasts, is derived from the colony forming units that form myeloid cells (CFU-GEMM). The CFU-GEMM is also referred to as common myeloid progenitor cells giving rise to various hemopoietic cell lines. (2025). 9781550092134, BC Decker. ISBN 9781550092134
Once formed, megakaryoblasts become promegakaryocytes through one or two cycles of endomitosis, which is the division of chromosomes without the cell dividing via cytokinesis. Endomitosis creates cells with one nucleus and multiple chromosome copies. The promegakaryocytes continue the process of endomitosis, which results in the formation of granular megakaryocytes as the nucleus forms lobes with increased volumes. The megakaryocytes release the into the blood stream. (2025). 9780128098431, Elsevier. ISBN 9780128098431
The process of platelet production, beginning with the formation of megakaryoblasts, takes about 7 days. Once in the blood stream, platelets last about 8 to 10 days.
Compared to megakaryoblasts, promegakaryocytes and granular megakaryocytes are both larger and contain less basophilic cytoplasm with granules. Promegakaryocytes are usually about 15μm to 30μm in diameter with a lobed nucleus and some azurophil granules within moderately basophilic cytoplasm. Granular megakaryocytes are typically 40μm to 60μm in diameter with a large multi-lobed nucleus and an abundance of azurohpil granules within slightly basophilic cytoplasm.
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