The alpha(IIb)beta(3) integrin and GPIb-V-IX complex identify distinct stages in the maturation of CD34(+) cord blood cells to megakaryocytes.
Megakaryocytopoiesis is a complex multistep process involving cell division, endoreplication, and maturation and resulting in the release of platelets into the blood circulation. Megakaryocytes (MK) progressively express lineage-restricted proteins, some of which play essential roles in platelet physiology. Glycoprotein (GP)Ib-V-IX (CD42) and GPIIb (CD41) are examples of MK-specific proteins having receptor properties essential for platelet adhesion and aggregation. This study defined the progressive expression of the GPIb-V-IX complex during in vitro MK maturation and compared it to that of GPIIb, an early MK marker. Human cord blood CD34(+) progenitor cells were cultured in the presence of cytokines inducing megakaryocytic differentiation. GPIb-V-IX expression appeared at day 3 of culture and was strictly dependent on MK cytokine induction, whereas GPIIb was already present in immature CD34(+) cells. Analysis by flow cytometry and of the messenger RNA level both showed that GPV appeared 1 day later than GPIb-IX. Microscopy studies confirmed the late appearance of GPV, which was principally localized in the cytoplasm when GPIb-IX was found on the cell surface, suggesting a delayed program of GPV synthesis and trafficking. Cell sorting studies revealed that the CD41(+)GPV(+) population contained 4N and 8N cells at day 7, and was less effective than CD41(+)GPV(-) cells in generating burst-forming units of erythrocytes or MK colonies. This study shows that the subunits of the GPIb-V-IX complex represent unique surface markers of MK maturation. The genes coding for GPIb-IX and GPV are useful tools to study megakaryocytopoiesis and for tissue-specific or conditional expression in mature MK and platelets. (Blood. 2000;96:4169-4177)
Lepage
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INSERM U.506, Hôpital Paul Brousse, 14 avenue Paul Vaillant Couturier, F-94800 Villejuif, France.
Leboeuf
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Cazenave
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JP
de la Salle
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C
Lanza
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Uzan
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D018952:Antigens, CD34 / Q000032:analysis*; D000943:Antigens, Differentiation / Q000032:analysis* / Q000096:biosynthesis / Q000235:genetics; D002454:Cell Differentiation; D002462:Cell Membrane / Q000737:chemistry; D002463:Cell Membrane Permeability; D002469:Cell Separation; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D003593:Cytoplasm / Q000737:chemistry; D015672:Erythroid Precursor Cells / Q000166:cytology; D005312:Fetal Blood / Q000166:cytology*; D005434:Flow Cytometry; D018507:Gene Expression Regulation, Developmental; D006410:Hematopoiesis; D006801:Humans; D007231:Infant, Newborn; D008533:Megakaryocytes / Q000737:chemistry / Q000166:cytology*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000032:analysis* / Q000096:biosynthesis / Q000235:genetics; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000032:analysis* / Q000096:biosynthesis / Q000235:genetics; D011003:Ploidies; D021381:Protein Transport; D012333:RNA, Messenger / Q000096:biosynthesis; D013997:Time Factors
D018952:Antigens, CD34; D000943:Antigens, Differentiation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D019038:Platelet Glycoprotein GPIb-IX Complex; D012333:RNA, Messenger