Bernard-soulier syndrome with a homozygous 13 base pair deletion in the signal peptide-coding region of the platelet glycoprotein Ib(beta) gene.
ABSTRACT We report a family with Bernard-Soulier syndrome with a homozygous mutation within the GPIb(beta) gene. The proband was a 24-year-old Japanese male who has suffered from life-long bleeding tendency. The patient's sister also had severe bleeding episodes. The proband and the affected sister had no apparent complications including organic or skeletal anomaly, or mental disturbance. They had thrombocytopenia [(35-40) x 10(9)/l] with giant platelets. In addition to platelet size, electron microscopic analysis revealed abnormalities in the internal structures of platelets. Ristocetin-induced platelet aggregation was defective. Flow cytometric analysis and western blot analysis showed that glycoprotein IX was nearly absent in platelets, whereas GPIb(alpha) and GPV were detectable. Genetic studies revealed a 13 base pair deletion in the signal peptide-coding sequence of GPIb(beta). The deletion would cause a frame-shift, resulting in the appearance of a stop codon following an indifferent polypeptide sequence. Analysis of platelet RNA showed that the mutant GPIb(beta) gene was transcribed. The propositus and his affected sister were homozygous for the deletion, whereas their unaffected father and mother were heterozygotes. The molecular defects of this family would help understand the relevance of GPIb(beta) for complex formation of the glycoprotein Ib/IX/V receptor.
Article: The same genetic defect in three Tunisian families with Bernard Soulier syndrome: a probable founder Stop mutation in GPIbbeta.[show abstract] [hide abstract]
ABSTRACT: GPIbα, GPIbβ, and GPIX are three candidate genes for a rare genetic bleeding disorder named Bernard Soulier syndrome (BSS). These genes are unique in the genome and encode for glycoprotein subunits of the GPIb-IX complex. Quantitative or qualitative deficiency in this complex is often associated with BSS. Here, we report the novel variant of BSS in which Ser23 of GPIbβ is substituted by a Stop codon causing a premature termination of translation, recently described in one family. This genetic defect is revealed in three unrelated BSS patients. The pedigree was determined for two families (F1 and F2) and revealed the homozygosity of the mutation in the two patients and its heterozygosity in parents. In the third family, the patient DNA was heterozygote with the same Ser23 Stop mutation in addition to two missense heterozygote mutations (Asp 51 Gly) and (Ala 55 to Pro). We studied the effect of the Ser23 Stop mutation on the expression of the complex. Our findings confirm that the identified GPIbβ mutation is responsible for the BSS phenotype and hampers the GPIb-IX complex to form on the platelets' surface. Regarding the scarcity of the BSS syndrome, the occurrence of the same mutation in three unrelated families would suggest a BSS founder mutation in Tunisia.Annals of Hematology 06/2009; 89(1):75-81. · 2.62 Impact Factor
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ABSTRACT: Bernard-Soulier syndrome (BSS), also known as Hemorrhagiparous thrombocytic dystrophy, is a hereditary bleeding disorder affecting the megakaryocyte/platelet lineage and characterized by bleeding tendency, giant blood platelets and low platelet counts. This syndrome is extremely rare as only approximately 100 cases have been reported in the literature. Clinical manifestations usually include purpura, epistaxis, menorrhagia, gingival and gastrointestinal bleeding. The syndrome is transmitted as an autosomal recessive trait. The underlying defect is a deficiency or dysfunction of the glycoprotein GPIb-V-IX complex, a platelet-restricted multisubunit receptor required for normal primary hemostasis. The GPIb-V-IX complex binds von Willebrand factor, allowing platelet adhesion and platelet plug formation at sites of vascular injury. Genes coding for the four subunits of the receptor, GPIBA, GPIBB, GP5 and GP9, map to chromosomes 17p12, 22q11.2, 3q29, and 3q21, respectively. Defects have been identified in GPIBA, GPIBB, and GP9 but not in GP5. Diagnosis is based on a prolonged skin bleeding time, the presence of a small number of very large platelets (macrothrombocytopenia), defective ristocetin-induced platelet agglutination and low or absent expression of the GPIb-V-IX complex. Prothrombin consumption is markedly reduced. The prognosis is usually good with adequate supportive care but severe bleeding episodes can occur with menses, trauma and surgical procedures. Treatment of bleeding or prophylaxis during surgical procedures usually requires platelet transfusion.Orphanet Journal of Rare Diseases 02/2006; 1:46. · 5.83 Impact Factor