title: Synthesis of transforming growth factor-beta 1 by megakaryocytes and its localization to megakaryocyte and platelet alpha-granules.
abstract: We have directly demonstrated that megakaryocytes are a major site of synthesis and storage of transforming growth factor-beta 1 (TGF/beta 1) by combined immunohistochemical, immunocytochemical, and in situ hybridization methods. The presence of TGF/beta 1 messenger RNA (mRNA) in mature megakaryocytes in adult rat spleen and bone marrow (BM) was established by in situ hybridization. Localization of TGF/beta 1 protein to intact alpha-granules of megakaryocytes, its putative storage site, was accomplished in glycol-methacrylate embedded porcine BM with an immunoperoxidase technique and light microscopy. The TGF/beta 1 was sequestered in intracytoplasmic granules in a pattern virtually identical to that of another alpha-granule marker protein, fibrinogen. This observation strongly suggests packaging of TGF/beta 1 into this organelle within megakaryocytes. That TGF/beta 1 mRNA was localized to megakaryocytes suggests that the TGF/beta 1 found in the alpha-granules in platelets originates with megakaryocyte synthesis. The alpha-granule localization of TGF/beta 1, as well as fibrinogen, was also demonstrated in isolated platelets at the ultrastructural level by electronmicroscopy (EM) and postembedding colloidal-gold immunocytochemistry, thus directly demonstrating that alpha-granules are the final storage site for TGF/beta 1 in mature platelets.
authors.affiliation: Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, TN.
authors.forename: R A
authors.initials: RA
authors.lastname: Fava
authors.forename: T T
authors.initials: TT
authors.lastname: Casey
authors.forename: J
authors.initials: J
authors.lastname: Wilcox
authors.forename: R W
authors.initials: RW
authors.lastname: Pelton
authors.forename: H L
authors.initials: HL
authors.lastname: Moses
authors.forename: L B
authors.initials: LB
authors.lastname: Nanney
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000378:metabolism* / Q000648:ultrastructure; D001853:Bone Marrow / Q000378:metabolism / Q000648:ultrastructure; D001854:Bone Marrow Cells; D003594:Cytoplasmic Granules / Q000378:metabolism* / Q000648:ultrastructure; D006018:Glycols; D007106:Immune Sera / Q000276:immunology; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry / Q000379:methods; D008533:Megakaryocytes / Q000378:metabolism* / Q000648:ultrastructure; D008689:Methacrylates; D008854:Microscopy, Electron / Q000379:methods; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D013154:Spleen / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D013552:Swine; D016212:Transforming Growth Factor beta / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology
chemical_list: D006018:Glycols; D007106:Immune Sera; D008689:Methacrylates; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta