The same genetic defect in three Tunisian families with Bernard Soulier syndrome: a probable founder Stop mutation in GPIbbeta

Purification of glycocalicin from human plasma

Glycocalicin (GC) is a large extracellular proteolytic fragment of glycoprotein Ib, a membrane platelet component playing an essential role in the physiological processes of platelet adhesion and aggregation. GC contains the binding sites for thrombin and von Willebrand factor. GC circulates normally in vivo in significant concentrations and the plasma level of this protein reflects a complex function of factors including platelet count or platelet turnover. It can therefore serve as a good indicator for many diseases like hypoplastic thrombocytopenia and idiopathic thrombocytopenic purpura. For this reason, several purification assays have been previously described. In this work, we describe a novel analytical method for GC purification from human platelets based on preparative HPLC gel filtration followed by immuno-affinity chromatography on NHS activated column conjugated with specific antibody. Pure GC was obtained from tiny amount of starting material. Our protocol of GC purification is simple, fast and provides a pure end product.

Spectrum of the mutations in Bernard-Soulier syndrome

Bernard-Soulier syndrome (BSS) is a rare autosomal recessive bleeding disorder characterized by defects of the GPIb-IX-V complex, a platelet receptor for von Willebrand factor (VWF). Most of the mutations identified in the genes encoding for the GP1BA (GPIbα), GP1BB (GPIbβ), and GP9 (GPIX) subunits prevent expression of the complex at the platelet membrane or more rarely its interaction with VWF. As a consequence, platelets are unable to adhere to the vascular subendothelium and agglutinate in response to ristocetin. In order to collect information on BSS patients, we established an International Consortium for the study of BSS, allowing us to enrol and genotype 132 families (56 previously unreported). With 79 additional families for which molecular data were gleaned from the literature, the 211 families characterized so far have mutations in the GP1BA (28%), GP1BB (28%), or GP9 (44%) genes. There is a wide spectrum of mutations with 112 different variants, including 22 novel alterations. Consistent with the rarity of the disease, 85% of the probands carry homozygous mutations with evidence of founder effects in some geographical areas. This overview provides the first global picture of the molecular basis of BSS and will lead to improve patient diagnosis and management.