Masaaki Moroi

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We have investigated the density of the collagen receptors glycoprotein VI (GPVI) and alpha 2 beta 1 on human platelets and their relationship to polymorphisms within the GPVI gene. GPVI levels varied 1.5-fold and showed a weak correlation (r = 0.35) with the levels of alpha 2 beta 1, which varied 3-fold. GPVI genotype had a significant effect on receptor(More)
Recently, a human megakaryoblastic cell line, CMK, was established from the peripheral blood of a megakaryoblastic leukemia patient with Down syndrome. Using this cell line, we studied the proliferation and differentiation of megakaryocytic cells in the presence of highly purified human hematopoietic factors and phorbol 12-myristate-13-acetate (PMA). In a(More)
A patient who suffered a recurring thrombosis over the last 15 yr has been investigated. The only abnormality found in this patient was a significantly depressed level of plasminogen activity in plasma. In spite of the depressed plasminogen activity, the patient was found to have a normal level of plasminogen antigen concentration. It was calculated that(More)
The extracellular matrix protein, laminin, supports platelet adhesion through binding to integrin ␣ 6 ␤ 1 In the present study, we demonstrate that human laminin, purified from placenta, also stimulates formation of filopodia and lamellipodia in human and mouse platelets through a pathway that is dependent on ␣ 6 ␤ 1 and the collagen receptor GPVI. The(More)
Phosphoinositide 3–kinases (PI3Ks), a family of lipid kinases comprising 3 classes with multiple isoforms, have been shown to participate in different phases of platelet signaling. To investigate the roles that enzymes play in platelet function in vivo and determine which iso-forms are important for particular signal-ing events, we analyzed platelet(More)
The platelet collagen receptor glycoprotein VI (GPVI) has been suggested to function as a dimer, with increased affinity for collagen. Dissociation constants (K(d)) obtained by measuring recombinant GPVI binding to collagenous substrates showed that GPVI dimers bind with high affinity to tandem GPO (Gly-Pro-Hyp) sequences in collagen, whereas the markedly(More)
The genetic basis for Glanzmann's thrombasthenia (GT) was elucidated on a compound heterozygote with glycoprotein (GP)IIb gene: an opal mutation at the end of exon 17 (CGA----TGA) results in only a trace amount of GPIIb mRNA, and a splicing mutation at the acceptor site of exon 26 (CAG----GAG) causes an in-frame, exon skipping process from exon 25 to 27.(More)
Glycoprotein VI (GPVI) is an essential platelet receptor for collagens that is exclusively expressed in the megakaryocytic lineage. Transcription of the human gene GP6 is driven largely by GATA-binding protein 1 (GATA-1), specificity protein 1 (Sp1), and Friend leukemia integration 1 (Fli-1). In this report, we show that GPVI expression during(More)
Visit-to-visit blood pressure (BP) variability is an important predictor of stroke. However, which antihypertensive drug combination is better at reducing visit-to-visit BP variability and therefore at reducing stroke incidence remains uncertain. We have previously reported that the dihydropyridine calcium channel blocker benidipine combined with a(More)
Essentials Dimeric high-affinity collagen receptor glycoprotein VI (GPVI) is present on resting platelets. Spatio-temporal organization of platelet GPVI-dimers was evaluated using advanced microscopy. Upon platelet adhesion to collagenous substrates, GPVI-dimers coalesce to form clusters. Clustering of GPVI-dimers may increase avidity and facilitate(More)
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