ADDITIONAL GLYCOPROTEIN DEFECTS IN BERNARD-SOULIERS SYNDROME - CONFIRMATION OF GENETIC-BASIS BY PARENTAL ANALYSIS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 62  (4) , 800-807
Abstract
The glycoprotein profile of Bernard-Soulier platelets was examined by labeling washed platelets with periodate 3H-sodium borohydride, a procedure that labels > 30 glycoproteins on the membrane surface of normal platelets. Three Bernard-Soulier patients were studied: 2 were siblings and the 3rd was unrelated. The platelet protein and glycoprotein profiles were evaluated under nonreduced and reduced conditions using 5-15% exponential SDS[sodium dodecyl sulfate]-polyacrylamide gel electrophoresis. The 2 siblings completely lacked glycoprotein Ib (GPIb). The unrelated patient had .simeq. 7% of the normal level. This was confirmed by 2-dimensional nonreduced-reduced SDS-polyacrylamide gel electrophoresis, a procedure that allows clear separation of the disulfide-linked subunits of GPIb, GPIb.alpha. (MW 145,000), and GPI.beta. (MW 25,000) from other membrane glycoproteins. On 1-dimensional analysis, Bernard-Soulier''s syndrome (BSS) platelets also lacked the peripheral membrane glycoprotein, GPV (MW 82,000) and a low-MW glycoprotein, GPIX, (nonreduced or reduced, MW .simeq. 22,000). The 2-dimensional gel system also revealed the absence of a minor glycoprotein with a MW of .simeq. 100,000 (GP 100). Quantitation of these proteins solubilized from electrophoretograms showed that the siblings'' parents had .simeq. 50% levels of GPIb, GPIX and GP 100. A monoclonal antibody against GPIb, FMC 25, was negative by immunofluorescence against Bernard-Soulier platelets and immuneprecipitated both GPIb and GPIX from Triton X100 solubilized, labeled platelets. The apparent genetic absence of multiple proteins in Bernard-Soulier platelets may be due, in part, to the presence in normal platelets of a tight membrane complex between GPIb and at least one of the other absent glycoproteins.