A Novel Mutation in GP1BB Reveals the Role of the Cytoplasmic Domain of GPIbß in the Pathophysiology of Bernard-Soulier Syndrome and GPIb-IX Complex Assembly.

Bernard-Soulier syndrome (BSS) is an autosomal-recessive bleeding disorder caused by biallelic variants in the GP1BA, GP1BB, and GP9 genes encoding the subunits GPIbα, GPIbß, and GPIX of the GPIb-IX complex. Pathogenic variants usually affect the extracellular or transmembrane domains of the receptor subunits. We investigated a family with BSS caused by the homozygous c.528_550del (p.Arg177Serfs*124) variant in GP1BB, which is the first mutation ever identified that affects the cytoplasmic domain of GPIbß. The loss of the intracytoplasmic tail of GPIbß results in a mild form of BSS, characterized by only a moderate reduction of the GPIb-IX complex expression and mild or absent bleeding tendency. The variant induces a decrease of the total platelet expression of GPIbß; however, all of the mutant subunit expressed in platelets is correctly assembled into the GPIb-IX complex in the plasma membrane, indicating that the cytoplasmic domain of GPIbß is not involved in assembly and trafficking of the GPIb-IX receptor. Finally, the c.528_550del mutation exerts a dominant effect and causes mild macrothrombocytopenia in heterozygous individuals, as also demonstrated by the investigation of a second unrelated pedigree. The study of this novel GP1BB variant provides new information on pathophysiology of BSS and the assembly mechanisms of the GPIb-IX receptor.

Bernard-Soulier syndrome associated with 22q11.2 deletion and clinical features of DiGeorge/velocardiofacial syndrome.

: Bernard-Soulier syndrome (BSS) is a rare autosomal recessive bleeding disorder caused by a defective function of glycoprotein (GP) Ib-V-IX complex. Among the genes encoding the 4 receptor subunits (GPIbα, GPIbß, GPV and GPIX), the GPIbß gene is located on chromosomes 22q11.2. We report a case of a girl with BSS associated with clinical features of 22q11.2 deletion syndrome (22q11.2DS) with phenotypic spectrum of DiGeorge syndrome/velocardiofacial syndrome. She has a history of life-long bleeding tendency, tetralogy of Fallot, hypothyroidism, mild facial dysmorphic signs and macrothrombocytopenia. The BBS and 22q11.2DS association could be explained by the fact that the constitutional hemizygosity of 22q11.2 may unmask an autosomal recessive disorder caused by alterations of the nondeleted GPIbß allele. We suggest that all patients with 22q11.2DS and bleeding manifestations should be always tested for BSS.

Study of Bernard-Soulier Syndrome Megakaryocytes and Platelets Using Patient-Derived Induced Pluripotent Stem Cells.

Bernard-Soulier syndrome (BSS) is a hereditary macrothrombocytopenia caused by defects in the glycoprotein (GP) Ib-IX-V complex. The mechanism of giant platelet formation remains undefined. Currently, megakaryocytes (MKs) can be generated from induced pluripotent stem cells (iPSCs) to study platelet production under pharmacological or genetic manipulations. Here, we generated iPSC lines from two BSS patients with mutations in different genes (GP1BA and GP1BB: termed BSS-A and BSS-B, respectively). The iPSC-derived MKs and platelets were examined under electron microscopy and stained by immunofluorescence to observe proplatelet formation and measure platelet diameters which were defined by circumferential tubulin. BSS-iPSCs produced abnormal proplatelets with thick shafts and tips. In addition, compared with the normal iPSCs, the diameters were larger in platelets derived from BSS-A and BSS-B with the means ± standard deviations of 4.34 ± 0.043 and 3.88 ± 0.045 µm, respectively (wild-type iPSCs 2.61 ± 0.025 µm, p < 0.001). Electron microscopy revealed giant platelets with the abnormal demarcation membrane system. Correction of BSS-A and BSS-B-iPSCs using lentiviral vectors containing respective GP1BA and GP1BB genes improved proplatelet structures and platelet ultrastructures as well as reduced platelets sizes. In conclusion, the iPSC model can be used to explore molecular mechanisms and potential therapy for BSS.

How we treat the platelet glycoprotein defects; Glanzmann thrombasthenia and Bernard Soulier syndrome in children and adults.

The inherited platelet glycoprotein deficiencies, Glanzmann thrombasthenia (GT) and Bernard Soulier syndrome (BSS) are rare but important long-term bleeding disorders. Once diagnosed, affected patients should be referred to a specialist centre for bleeding disorders for general advice and ongoing management. Patients do not require prophylactic treatment and so the management of GT and BSS focuses around prophylactic treatment prior to high risk procedures and treatment in response to non-surgical bleeding events and, in women, the management of menorrhagia and pregnancy. There is no consistent approach to the treatment or prevention of bleeding complications. Management must be tailored for each individual and the approach may not be the same for different events, even for the same patient, depending on the type of accident or invasive procedure, the extent of bleeding and the presence or not of platelet refractoriness.

Induced pluripotent stem cells derived from Bernard-Soulier Syndrome patient's peripheral blood cells with a p.Phe55Ser mutation in the GPIX gene.

Bernard Soulier Syndrome (BSS) is a rare autosomal platelet disorder characterized by mutations in the von Willebrand factor platelet receptor complex GPIb-V-IX. In this work we have generated an induced pluripotent stem cell (BSS3-PBMC-iPS4F8) from peripheral blood mononuclear cells of a BSS patient with a p.Phe55Ser mutation in the GPIX gene. Characterization of BSS3-PBMC-iPS4F8 showed that these cells maintained the original mutation present in the BSS patient, expressed pluripotent stem cell markers and were able to differentiate into the three germline layers. This new iPSC line will contribute to better understand the biology of BSS disease.

Patients with Bernard-Soulier syndrome and different severity of the bleeding phenotype.

Bernard-Soulier syndrome is a rare (1:1million), hereditary bleeding disorder caused by defects of the platelet GPIb-IX-V complex. Patients suffer from mucocutaneous bleedings. Typical are thrombocytopenia, giant platelets and impaired agglutination after stimulation with ristocetin. In populations in which consanguineous marriages are common the frequency of the disorder is increased because Bernard-Soulier syndrome is mostly inherited autosomal recessively. Genetic analyses of the disease-related genes may help to gain more insights regarding the phenotype/genotype correlation. Here, we investigated several patients with Bernard-Soulier syndrome from different families. We analyzed two patients with severe bleeding symptoms from one family of middle east origin and confirmed the diagnosis by identifying a pathogenic variant in GP1BB. We compared phenotype/genotype correlation of this GP1BB mutation with the GP9 (p.Asn61Ser) European founder mutation present in 9 patients out of 4 families for whom we also performed molecular genetic analysis.

Generation of a human induced pluripotent stem cell (iPSC) line from a Bernard-Soulier syndrome patient with the mutation p.Asn45Ser in the GPIX gene.

Bernard Soulier Syndrome (BSS) is an inherited rare platelet disorder characterized by mutations in the platelet glycoprotein complex GPIb-IX-V. We generated an induced pluripotent stem cell (iPSC) line from a BSS patient with a mutation p.Asn45Ser in the GPIX locus (BSS2-PBMC-iPS4F24). Peripheral blood mononuclear cells were reprogrammed using non-integrative viral transduction. Characterization of BSS2-PBMC-iPS4F24 included mutational analysis of GPIX locus, analysis of conventional pluripotency-associated factors at mRNA and protein level and in vitro and in vivo differentiation studies. This iPSC line will provide a powerful tool to study the biology of BSS disease.

Generation of induced pluripotent stem cells (iPSCs) from a Bernard-Soulier syndrome patient carrying a W71R mutation in the GPIX gene.

We generated an induced pluripotent stem cell (iPSC) line from a Bernard-Soulier Syndrome (BSS) patient carrying the mutation p.Trp71Arg in the GPIX locus (BSS1-PBMC-iPS4F4). Peripheral blood mononuclear cells (PBMCs) were reprogrammed using heat sensitive non-integrative Sendai viruses containing the reprogramming factors Oct3/4, SOX2, KLF4 and c-MYC. Successful silencing of the exogenous reprogramming factors was checked by RT-PCR. Characterization of BSS1-PBMC-iPS4F4 included mutation analysis of GPIX locus, Short Tandem Repeats (STR) profiling, alkaline phosphatase enzymatic activity, analysis of conventional pluripotency-associated factors at mRNA and protein level and in vivo differentiation studies. BSS1-PBMC-iPS4F4 will provide a powerful tool to study BSS.

The utility of International Society on Thrombosis and Haemostasis-Bleeding Assessment Tool and other bleeding questionnaires in assessing the bleeding phenotype in two platelet function defects.

The main objective of this study is to investigate the utility of International Society on Thrombosis and Haemostasis-Bleeding Assessment Tool (ISTH-BAT) in comparison with the condensed form of Molecular and Clinical Markers for the Diagnosis and Management of type 1 and WHO BATs, in assessing bleeding in two well known and clinically significant platelet function defects. Thirty-eight patients previously diagnosed with Glanzmann's thrombasthenia and 10 with Bernard-Soulier syndrome (BSS) were analyzed. Bleeding scores were significantly higher than that of controls using both electronic bleeding questionnaire (eBQ) and ISTH-BAT with no significant difference between both tools. ISTH-BAT had a sensitivity, specificity, positive predictive value and negative predictive value of 100%, 76.2%, 0.9 and 1. This was closely similar to eBQ. Both ISTH-BAT and eBQ are efficient in BSS and Glanzmann's thrombasthenia. However, given the ISTH recommendation, ISTH-BAT should be adopted. Larger study including other platelet defects will enhance its utility and support the integration of bleeding scores with standardized laboratory testing to allow for a universal diagnostic approach to patients with suspected bleeding disorders.

[Bernard-Soulier syndrome and pregnancy: a case report]. / Syndrome de Bernard-Soulier et grossesse : à propos d'un cas.

Bernard-Soulier syndrome is an inherited bleeding disorder. Due to the rarity of the combination of this syndrome and pregnancy, data on the clinical course and outcome of pregnancy in women with Bernard-Soulier syndrome is scattered in individual case reports and there is no consensus in the management of SBS. In some patients, the pregnancy course was uneventful while in others post partum hemorrhage was the most common complication. We report our experience about the perioperative management of a pregnant woman with Bernard-Soulier syndrome.

Primigravida with Bernard-Soulier Syndrome: a case report.

BACKGROUND: Bernard-Soulier Syndrome is a rare congenital bleeding disorder, mainly inherited in an autosomal recessive pattern. It is characterized by a genetic defect on one of the four genes encoding the subunits of the transmembrane protein complex GPIb-V-IX, physiologically expressed only in platelets. The exact phenotype varies widely from individual to individual depending on the particular mutation presented. Currently, there is no consensus about ideal management of affected pregnant women, in face of the scarcity of cases. CASE PRESENTATION: We report on a 28-year-old Black Brazilian primigravida who was referred to our maternity hospital, a tertiary care center, for decision about the most adequate mode of delivery. She was admitted with a platelet count of 43.000 plt/µL, and hemoglobin of 13.6 g/dL. Platelet transfusion was regarded as a necessary prophylactic measure prior to delivery. Ten units of random donor platelets were administered on the course of three days, after which the patient was submitted to an elective cesarean section delivery under general anesthesia at 40 weeks of gestational age. A healthy male baby with a normal birthweight of 3.615 kg was delivered. After the delivery, the mother's state continued being assessed daily, with special attention taken to lochia and surgical wound healing. At one week postpartum, a complete blood count revealed a platelet count of 41.000 plt/µL, and hemoglobin of 13.3 g/dL. As there were no signs of neither evident nor occult hemorrhage, and surgical wound was healing accordingly, the patient was discharged, after being oriented about bleeding preventive measures. CONCLUSION: The peripartum period is regarded as the most crucial moment of pregnancy in women with Bernard-Soulier Syndrome, hence the importance of a judiciously planned mode of delivery, and of careful prophylaxis against bleeding beforehand. Furthermore, absence of complications during the peripartum period does not predict how the woman will do subsequently. Strict vigilance is warranted at least until six weeks postpartum, due to the virtual risk of secondary postpartum hemorrhage.

Roll, adhere, spread and contract: structural mechanics of platelet function.

Platelets are involved in life-sustaining processes such as hemostasis, wound healing, atherothrombosis and angiogenesis. Mechanical trauma to blood vessels causes platelet activation resulting in their adherence and clot formation at the damaged site, culminating in clot retraction and tissue repair. Two of the major players underlying this process are the cytoskeleton, i.e., actin and microtubules, and the membrane integrin receptors. Rare congenital bleeding disorders such as Glanzmann thrombasthenia and Bernard-Soulier syndrome are associated with genetic alterations of platelet surface receptors, also affecting the platelet cytoskeletal structure. In this review, we summarize the current knowledge about platelet structure and adhesion, and delve into the mechanical aspects of platelet function. Platelets lack a nucleus, and can thus provide a minimal model of a biological cell. New biophysical tools may help to scrutinize platelets anew and to extend the existing knowledge on cell biology.

Inherited platelet disorders including Glanzmann thrombasthenia and Bernard-Soulier syndrome.

Inherited platelet disorders (IPDs) are a heterogeneous group of diseases affecting platelet production, morphology, and function. The degree of thrombocytopenia and functional abnormality of platelets determines the clinical manifestations. Although severe deficiencies may cause excessive bleeding beginning in early childhood, most of IPDs have mild bleeding tendencies and therefore are not always easy to distinguish from acquired platelet disorders. The diagnosis of IPD may require extensive laboratory investigation, because current routine laboratory tests are not satisfactory for differential diagnosis in some cases, and most of the specific tests are not readily available in many countries. This review summarizes the classification and clinical and molecular characteristics of known IPDs, including Bernard-Soulier syndrome and Glanzmann thrombasthenia, with a focus on current challenges in the laboratory diagnosis and management of bleeding in these patients.