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Megakaryocyte dense granule components are sorted in multivesicular bodies
1INSERM U 474, Hôpital Cochin-Port-Royal, Paris, France.
Blood
|June 14, 2000
Summary
Dense granules appear early in human megakaryocyte maturation, with multivesicular bodies serving as an intermediate stage. Granulophysin is identified as a key dense granule marker.
Area of Science:
- Hematology
- Cell Biology
- Immunology
Background:
- The formation of alpha-granules involves multivesicular bodies (MVBs).
- The development and timing of dense granule formation during megakaryocyte maturation are not well understood.
Purpose of the Study:
- To investigate the kinetics and appearance of dense granules during human megakaryocyte maturation.
- To determine the role of multivesicular bodies in dense granule formation.
Main Methods:
- Immunoelectron microscopy was employed to examine cryosections of human megakaryocytes (MKs).
- CD34(+) precursors were cultured to generate MKs, and dense granule markers (granulophysin, serotonin) were monitored on days 8 and 13.
Main Results:
- Dense granules were observed to form early in immature MKs, coinciding with alpha-granule formation.
- In intermediate MKs, granulophysin localized to dense granules and MVBs, which also contained serotonin.
- This indicates granulophysin is a dense granule marker in human MKs.
Conclusions:
- Multivesicular bodies are an intermediate stage in dense granule maturation.
- MVBs likely function as a sorting compartment distinguishing between alpha-granules and dense granules.