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Megakaryocyte
A megakaryocyte (from mega- 'large' karyo- 'cell nucleus' and -cyte 'cell') is a large bone marrow cell with a lobated nucleus that produces blood platelets (thrombocytes), which are necessary for normal clotting. In humans, megakaryocytes usually account for 1 out of 10,000 bone marrow cells, but can increase in number nearly 10-fold during the course of certain diseases. Owing to variations in combining forms and spelling, synonyms include megalokaryocyte and megacaryocyte.
In general, megakaryocytes are 10 to 15 times larger than a typical red blood cell, averaging 50–100 μm in diameter. During its maturation, the megakaryocyte grows in size and replicates its DNA without cytokinesis in a process called endomitosis. As a result, the nucleus of the megakaryocyte can become very large and lobulated, which, under a light microscope, can give the false impression that there are several nuclei. In some cases, the nucleus may contain up to 64N DNA, or 32 copies of the normal complement of DNA in a human cell.
The cytoplasm, just as the platelets that bud off from it, contains α-granules and dense bodies.
Recent single-cell RNA sequencing studies have revealed that megakaryocytes are not a homogeneous population, but rather comprise distinct subpopulations with specialized functions. Megakaryocytes can be transcriptionally categorized into platelet generating, niche supporting, immune, and cycling cells, which are distinguished by their unique gene expression patterns and cellular markers.
These functional subpopulations include:
Thrombopoietic megakaryocytes: The classic platelet-producing cells with high expression of genes involved in platelet formation and release.
Immune megakaryocytes: A significant population of these cells have been established to reside in the non-hematopoietic tissues and they display enhanced immune-related characteristics. These cells express higher levels of immune-related genes and can participate in antigen presentation and immune responses.
Niche-supporting megakaryocytes: Megakaryocytes that support hematopoietic stem cell maintenance in the bone marrow niche through production of regulatory factors such as CXCL4 (platelet factor 4), transforming growth factor-β1, and fibroblast growth factor 1.
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Megakaryocyte
A megakaryocyte (from mega- 'large' karyo- 'cell nucleus' and -cyte 'cell') is a large bone marrow cell with a lobated nucleus that produces blood platelets (thrombocytes), which are necessary for normal clotting. In humans, megakaryocytes usually account for 1 out of 10,000 bone marrow cells, but can increase in number nearly 10-fold during the course of certain diseases. Owing to variations in combining forms and spelling, synonyms include megalokaryocyte and megacaryocyte.
In general, megakaryocytes are 10 to 15 times larger than a typical red blood cell, averaging 50–100 μm in diameter. During its maturation, the megakaryocyte grows in size and replicates its DNA without cytokinesis in a process called endomitosis. As a result, the nucleus of the megakaryocyte can become very large and lobulated, which, under a light microscope, can give the false impression that there are several nuclei. In some cases, the nucleus may contain up to 64N DNA, or 32 copies of the normal complement of DNA in a human cell.
The cytoplasm, just as the platelets that bud off from it, contains α-granules and dense bodies.
Recent single-cell RNA sequencing studies have revealed that megakaryocytes are not a homogeneous population, but rather comprise distinct subpopulations with specialized functions. Megakaryocytes can be transcriptionally categorized into platelet generating, niche supporting, immune, and cycling cells, which are distinguished by their unique gene expression patterns and cellular markers.
These functional subpopulations include:
Thrombopoietic megakaryocytes: The classic platelet-producing cells with high expression of genes involved in platelet formation and release.
Immune megakaryocytes: A significant population of these cells have been established to reside in the non-hematopoietic tissues and they display enhanced immune-related characteristics. These cells express higher levels of immune-related genes and can participate in antigen presentation and immune responses.
Niche-supporting megakaryocytes: Megakaryocytes that support hematopoietic stem cell maintenance in the bone marrow niche through production of regulatory factors such as CXCL4 (platelet factor 4), transforming growth factor-β1, and fibroblast growth factor 1.