title: P-selectin mRNA is expressed at a later phase of megakaryocyte maturation than mRNAs for von Willebrand factor and glycoprotein Ib-alpha.
abstract: The assembly of alpha-granules occurs exclusively in megakaryocytes because platelets have limited capacity for the synthesis of macromolecules. Thus far, alpha-granule development in megakaryocytes has been primarily evaluated by ultrastructural studies. The aim of the study was to obtain molecular and biochemical evidence for the expression of selected alpha-granule proteins in megakaryocytes. Guinea pig megakaryocytes were purified and separated into subgroups at different phases of maturation by the Celsep procedure (Schick et al. Blood 1989;73:1801-8). Guinea pig-specific probes for P-selectin, von Willebrand factor (vWF), glycoprotein Ib-alpha (GpIb-alpha), and phosphoglycerate kinase were prepared by using the polymerase chain reaction. By Northern blot analysis, P-selectin messenger ribonucleic acid (mRNA) was primarily expressed in the mature megakaryocyte Celsep subgroup, whereas vWF and GpIb-alpha mRNA were expressed at all phases of megakaryocyte maturation. In situ hybridization confirmed that P-selectin mRNA was primarily expressed at later stages of cytoplasmic maturation: 14% +/- 6.2% of stage I, 35.5% +/- 6.1% of stage II, 72% +/- 5.2% of stage III, and 47.0% +/- 3.3% of stage IV megakaryocytes expressed P-selectin mRNA. Thus, the expression of mRNA for P-selectin appeared to peak in stage III cells. In contrast vWF mRNA was expressed in immature megakaryocytes and persisted throughout megakaryocyte maturation. In situ hybridization did not demonstrate a relationship between the expression of mRNA for P-selectin or vWF with megakaryocyte ploidy.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Cardeza Foundation for Hematologic Research, Philadelphia, Pennsylvania.
authors.forename: P K
authors.initials: PK
authors.lastname: Schick
authors.forename: B A
authors.initials: BA
authors.lastname: Konkle
authors.forename: X
authors.initials: X
authors.lastname: He
authors.forename: R D
authors.initials: RD
authors.lastname: Thornton
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015152:Blotting, Northern; D015815:Cell Adhesion Molecules / Q000235:genetics*; D006168:Guinea Pigs; D008533:Megakaryocytes / Q000378:metabolism*; D019007:P-Selectin; D010980:Platelet Membrane Glycoproteins / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis*; D014841:von Willebrand Factor / Q000235:genetics*
chemical_list: D015815:Cell Adhesion Molecules; D019007:P-Selectin; D010980:Platelet Membrane Glycoproteins; D012333:RNA, Messenger; D014841:von Willebrand Factor