Bernard-Soulier Syndrome Patients Research Articles

Novel GPIb-independent platelet aggregation induced by botrocetin: implications for diagnosis and antithrombotic therapy

BackgroundSnake venom botrocetin facilitates von Willebrand factor (VWF) binding to platelet GPIbα and has been widely used for the diagnosis of von Willebrand disease and GPIb-related disorders. Botrocetin is also commonly employed for the development/characterization of antithrombotics targeting the GPIb-VWF axis. ObjectivesTo explore the alternative receptor(s)/mechanisms that participate in botrocetin-induced platelet aggregation. MethodsThe effects of botrocetin on platelet aggregation were examined using platelets from wild-type, VWF- and fibrinogen-deficient, GPIbα-deficient, IL4Rα/GPIbα-transgenic and αIIbβ3-deficient mice and Bernard–Soulier syndrome and healthy human samples. Platelet-fibrinogen and platelet-VWF interaction were measured using flow cytometry. GPIbα-VWF binding was evaluated utilizing enzyme-linked immunosorbent assay. Botrocetin-αIIbβ3 and botrocetin-GPIbα interactions were measured using enzyme-linked immunosorbent assay and fluorescence anisotropy assays. Heparinized whole blood from healthy donors was examined for thrombus formation and growth in a perfusion chamber. ResultsBotrocetin could induce aggregation of platelets from a Bernard–Soulier syndrome patient and GPIbα-deficient mice as well as platelets lacking the N-terminal extracellular domain of GPIbα. Botrocetin could interact with αIIbβ3 and facilitated αIIbβ3-VWF interaction independent of GPIb. Botrocetin competitively bound to the ligand-binding domain of activated rather than resting αIIbβ3. Although botrocetin-induced platelet aggregation requires VWF, strikingly, in the absence of VWF, botrocetin blocked fibrinogen and other ligand binding to αIIbβ3 and inhibited platelet aggregation and thrombus formation. Consistently, recombinant botrocetin defective in VWF binding inhibited αIIbβ3- and GPIb-mediated platelet aggregation, spreading, and thrombus formation. ConclusionOur study provides insights into avoiding the misdiagnosis of GPIb-related disorders and developing botrocetin mutants as potential new antithrombotics that may simultaneously target both αIIbβ3 and GPIbα.

Understanding Natural History of Common Inherited Platelet Function Disorder (IPFD) Patients: An Indian Study

Background : Inherited platelet function disorders (IPFDs) are less well studied in a resource poor country in comparison to hemophilia and other bleeding disorders.With high rates of consanguinous marriages in some of the communities in India, Glanzmanns thrombasthenia (GT) and Bernard soulier syndrome (BSS) are the two platelet function disorders that are commonly diagnosed. There is no data on the nature of bleeding, mode of treatment, mortality as well as quality of life (QoL) in these conditions. Aim : To understand clinical manifestations, treatment, quality-of-life (QoL), mortality and other details in GT and BSS patients. Methods : This is a retrospective, non-interventional, observational single center data collection study.Subjects were eligible to participate, if they had confirmed reports of laboratory diagnosis of GT or BSS by both platelet aggregometry and flow cytometry studies. Data collected were demographics, medical history, co-morbidities (HIV, HCV, HBV), detailed treatment/product(s) usage, bleeding events, surgical procedures, and other adverse events. It also included patient-reported outcome questionnaires regarding health-related quality of life (HRQoL) using SF-36 and EQ-5D instruments. All data were entered into electronic case report forms by the laboratory personnel. Results : Sixty one ( GT 50, BSS 11) patients participated in the present study; 31 were males and 30 females. 43 were pediatric patients and 18 adults. Seventeen patients were diagnosed at birth and 10 patients were diagnosed beyond the age of 10 years. Forty four patients (72%) had parental consanguinity. Thirteen patients ( BSS 8, GT 5) did not have any major bleeding manifestations which required treatment. In the remaining patients, the median ABR was 10 ( range 2.5 - >75). The median ISTH BAT score was 10 (range 1-26.)The bleeding manifestations included epistaxis (61%), ecchymosis (58%) , gum bleed (48%), gastrointestinal bleed (28%), soft tissue bleed (23%), hematuria (8%), joint bleed (3%) and intracranial bleed ( 3%). Heavy menstrual bleed (HMB) was the primary bleeding manifestation in all females in the reproductive age group. Four patients were diagnosed following circumcision. Treatment strategies for bleeding events included antifibrinolytic agents alone (26%), platelet transfusion (43%), or whole blood and fresh frozen plasma (39%). Antifibrinolytic agents were also used as adjunct agents with platelet transfusion in majority of the patients. None of the patients were on recombinant activated FVIIa. Overall 8 deaths were reported due to bleeding in these 61 families during the last 10 years, the cause of death mainly being non-availability of treatment products. The self- reported median EQ-5D health score was 82.5 ( range 40-100) Figure 1 shows the detailed EQ-5D analysis in these 61 patients Conclusion : Present study provides detailed information of GT and BSS and its impact throughout life. A wide variation in clinical manifestations and disease outcomes was observed, the major attributing factor may possibly be socioeconomic factor which includes access to clinical resources and treatment products for bleed management. Unlike hemophilia, GT and BSS patients do not have the privilege of prophylactic treatment in our country, but there is a need for optimal disease management to normalize both physical and psychosocial outcomes. More such studies will add to an increased understanding of critical issues in these

Elevated CD9 expression as a potential biomarker for diagnosis of Bernard-Soulier syndrome.

Diagnosis of inherited platelet glycoprotein disorders is based on specific laboratory techniques such as aggregometry and flow cytometry. Flowcytometry is a powerful method, but equivocal results are produced in some cases. New cluster of differentiation markers could resolve the diagnostic dilemmas. Abnormal expression of CD9 in Bernard-Soulier syndrome (BSS) is recently reported. We aimed to determine the diagnostic significance of CD9 expression in a cohort of Iranian patients with inherited platelet glycoprotein defects. Twelve BSS, 21 Glanzmann thrombasthenia and 16 healthy controls were included in the present study. Flowcytometric diagnosis of BSS and Glanzmann thrombasthenia was made by analysis of CD41/61 and CD42a/42b CD markers. Moreover, phycoerythrin-labelled anti CD9 was examined in patients and healthy controls. The mean fluorescence intensity (MFI) of CD9 among the three groups was compared using suitable statistical methods and a P value of less than 0.05 considered statistically significant. Mean MFI of CD9 was 990.0 in BSS patients versus 421.2 and 317.3 in individuals with Glanzmann thrombasthenia and healthy controls, respectively (P < 0.05). Between the two-group comparison of means by the Mann-Whitney test revealed a P value of less than 0.001 for BSS group versus GT (2.4-fold) and BSS versus healthy controls (2.9-fold). CD9 molecule also expressed differently in patients with Glanzmann thrombasthenia in comparison with healthy controls (P < 0.001), although with a less magnitude (1.3-fold). According to our findings, CD9 is a potential biomarker for laboratory diagnosis of inherited glycoprotein defects, especially to elucidate the ambiguous results in BSS cases.

Evaluation of platelet surface glycoproteins in inherited thrombocytopathy

Background Glanzmann's thrombasthenia (GT) and Bernard-Soulier syndrome (BSS) are genetic bleeding syndromes characterized by defects in platelet aggregometry. Although these disorders are classified to be rare, their exact prevalence is still unknown; however, they are more frequent in communities where consanguineous marriages are common. Aim To study platelet surface glycoproteins expression using flow cytometry and to examine their correlation with bleeding severity using International Society of Thrombosis and Hemostasis–Bleeding Assessment Tools (ISTH-BAT) as bleeding score of choice. Patients and methods This case–control study included 51 patients with bleeding disorders recruited from the Department of Pediatric Hematology, Assiut University Hospital, in addition to 36 apparently healthy age- and sex-matched controls. All patients were tested for complete blood count (CBC), prothrombin time, partial thromboplastin time, platelet aggregation, and platelets surface glycoprotein analysis by flow cytometry. ISTH-BAT was used to register bleeding data for patients. Results GT and BSS had some similarities regarding the presentation and bleeding severity, but when CBC, platelet aggregation studies, and flow cytometric analysis were done, differentiation became much easier. GT patients showed a decrease in the expression of CD41 and CD61. Type I GT patients had more bleeding severity than type II and type III. BSS patients showed a decrease in expression of CD42b. There are correlations between the bleeding severity and CD41 in GT, and between the severity and CD42b in BSS. Conclusion Flow cytometric studies of platelet glycoproteins have great values in diagnosing BSS and GT, and further classifying GT cases into its three types. ISTH-BAT is a useful tool when dealing with platelet function disorders and has good sensitivity and ability to determine the severity.

Diagnosis of Bernard Soulier Syndrome and Glanzmann’s Thrombasthenia in Iraqi Patients

Background: Bernard–Soulier syndrome (BSS) and Glanzmann Thrombasthenia (GT) are rare inheritedplatelet function disorders, defined by a permanent history of mucocutaneous bleeding. The objective of thisproject was to identify biological and clinical characteristics of BSS and GT patients. Methodology: Thisstudy included 52 patients with bleeding disorders, the clinical, haematological and demographic featuresof patients were determined and the level of GpIIb/IIIa and GPIb/IX was assessed. Results: From a total of52 patient, 20 were diagnosis with BSS (9 females and 11 males), their age range from 6 to 42 year and 23diagnoses with GT (10 females and 13 males), their age range from 4 to 50 year. Epistaxis, easy bruising,menorrhagia and ecchymosis were the most frequent symptoms. Prolonged bleeding time (BT), normal PTand PTT were seen in all cases. Variable thrombocytopenia, large platelets with decreased GPIb/IX levelwere seen in BSS patients, while the level of GPIIb/IIIa was decreased in GT cases. Conclusion: SinceBSS and GT are infrequent disorders diagnosis may be postponed, both diseases are combined with crucialbleeding tendency, therefore earlier detection would have been important for patients management.

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.

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.

Clinical phenotype in heterozygote and biallelic Bernard-Soulier syndrome--a case control study.

Bernard-Soulier syndrome (BSS) is a rare severe autosomal recessive bleeding disorder. To date heterozygous carriers of BSS mutations have not been shown to have bleeding symptoms. We assessed bleeding using a semi-quantitative questionnaire, platelet parameters, PFA-100 closure times, ristocetin response, GP Ib/IX expression and VWF antigen in 14 BSS patients, 30 heterozygote carriers for related mutations and 29 controls. Eight mutations in GP1BA, GP1BB or GP9 were identified including four previously unknown pathogenic mutations. Subjects with BSS reported markedly more mucocutaneous bleeding than controls. Increased bleeding was also observed in heterozygotes. Compared to controls, patients with BSS had lower optical platelet counts (P < 0.001), CD61-platelet counts (P < 0.001) and higher mean platelet volume (17.7 vs. 7.8 fL, P < 0.001) and ristocetin response and closure times were unmeasurable. Heterozygotes had higher MPV (9.7 fL, P < 0.001) and lower platelet counts (P < 0.001) than controls but response to ristocetin and closure times were normal. The VWF was elevated in both BSS and in heterozygotes (P = 0.005). We conclude that heterozygotes for BSS mutations have lower platelet counts than controls and show a bleeding phenotype albeit much milder than in BSS. Both patients with BSS and heterozygote carriers of pathogenic mutations have raised VWF.

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.

Mutation Analysis and Clinical Sprectrum Of Patients With Glanzmann's Thrombasthenia and Bernard Soulier Syndrome

Introduction and Aim Glanzmann’s thrombasthenia (GT) is an inherited disorder of platelet aggregation, resulting from defective glycoprotein IIb/IIIa on platelet surface. Bernard Soulier Syndrome (BSS) is also an inherited disorder of platelet adhesion and associated with defective glycoprotein Ib-V-IX on platelet surface. Both of these disorders usually present with mucocutaneous bleedings. We aimed to evaluate the clinical and genetic characteristics of the patients diagnosed as BSS and GT in department of pediatric hematology of Meram Faculty of Medicine, retrospectively. Method Seven patients diagnosed with BSS and 20 patients diagnosed with GT were enrolled to the study. Medical records of patients were reviewed retrospectively. Glycoprotein IIb gen rearrangement was investigated in genetic department of Ankara University Medical School, Turkey. Mutational analysis for BSS was performed in Medicina Interna ed Oncologia Medica, Italy. The correlation between clinical outcome and genotyping was investigated. Results Of 20 patients of GT, 8 were male and 12 were female. Of 7 patients of BSS, all of them were female. Glycoprotein IIB gene rearrangement was detected in 7 patient of GT. 5 of 7 were newly described mutations in published literature. Mutations in GpIBB and GpIBA gene were detected in 7 patients with BSS. No correlation was observed among the clinical and genotype characteristics of patients both with GT and BSS. The most common patterns of bleeding were epistaxis and gum bleeding. Life threatening bleeding was seen in 5 of GT patients (4 gastrointestinal bleeding, 1 mediastinal hematoma) and 2 of BSS patients (1 splenic rupture and 1 gastrointestinal bleeding). No patients had died due to major bleedings. One patient with GT experienced spontaneous duodenal intramural bleeding resulting duodenal obstruction. One patient with BSS experienced spontaneous mediastinal hematoma. Although the BSS, it is interesting that the patient was able to control of mediastinal hematoma. Further investigations revealed the patient has prothrombotic mutation (heterozygous FV Leiden). Conclusion The most common bleeding pattern in patients with thrombocyte dysfunction is mucocutaneous bleeding. Some patients may suffer from life-threatening bleedings. Our study contributes to the literature because of five newly described mutations in GT patients. It may be hypothesed that the presence of prothrombotic mutation in patients with thrombocyte dysfunction may reduce the severity of bleedings. Disclosures: No relevant conflicts of interest to declare.

Novel genetic abnormalities in Bernard-Soulier syndrome in India

Bernard-Soulier syndrome (BSS) is a severe inherited bleeding disorder due to defects in GPIb/IX/V, a platelet receptor that normally functions as a platelet membrane receptor for von Willebrand factor, thrombin and factor XI. BSS results from mutations in GP1BA, GP1BB or GP9 genes. In 15 patients with Bernard-Soulier syndrome from Western India, we amplified the entire coding sequences of GP1BA, GP1BB and GP9 genes and directly sequenced them. Twelve homozygous changes have been identified, out of which ten were novel mutations. These included eight frameshift mutations, i.e. p.Asp79GlufsX2, p.Phe314PhefsX37, p.Pro93ProfsX59, p.Asp89GlufsX63, p.Glu489AsnfsX64, p.Phe355PhefsX4, p.Leu479PhefsX19 and p.Leu531ArgfsX22, one missense mutation (p.Val262Gly) in GPIBA and one nonsense mutation (p.Tyr95X) in GP9. The two known changes include one missense mutation (p.Cys24Arg) in GP9 and one nonsense change (p.Trp46X) in GPIBB. A wide heterogeneity in the nature of mutations has been observed in Indian BSS patients in the present study. Identification of mutations in this rare platelet function disorder would pave way for genetic diagnosis in affected families in India, where consanguineous marriages are very common.

Bernard-Soulier Syndrome: An Update

Bernard-Soulier syndrome (BSS) is a rare inherited platelet bleeding disorder characterized by low platelet count and abnormally large platelets (macrothrombocytopenia). Platelets from BSS patients are typically defective in surface expression of glycoprotein (GP)Ib-IX-V, a platelet-specific adhesion-signaling complex, composed of GPIbα disulfide linked to GPIbβ, and noncovalently associated with GPIX and GPV. The major ligand-binding subunit, GPIbα, binds the adhesive ligands von Willebrand factor (VWF) or thrombospondin, counterreceptors on activated endothelial cells (P-selectin) or activated leukocytes (integrin αMβ2), and coagulation factors (thrombin, factors XI and XII, high-molecular-weight kininogen). The cytoplasmic domain of GPIb-IX-V interacts with the cytoskeletal protein, filamin-A via a binding site within the GPIbα cytoplasmic tail, and with structural-signaling proteins including calmodulin, 14-3-3ζ and the p85 subunit of phosphoinositide 3-kinase. GPIbα is physically/functionally co-associated on the platelet surface with the major platelet collagen receptor, GPVI. As such, it is easy to see how genetic defects impacting GPIb-IX-V expression or function can have significant consequences on normal platelet size, adhesion to VWF/collagen and/or stable thrombus formation, and why BSS is often associated with clinical bleeding. Furthermore, the rarity, multiple genetic causes, and variable clinical phenotype of BSS can complicate routine diagnosis. Here, we discuss how studies of BSS have contributed to platelet biology and recent studies to improve diagnosis and treatment.

Bernard–Soulier syndrome caused by a hemizygous GPIbβ mutation and 22q11.2 deletion

Bernard-Soulier syndrome (BSS) is a rare autosomal recessive bleeding disorder characterized by giant platelets, thrombocytopenia, and a prolonged bleeding time, which is caused by homozygous mutations in the GPIbα, GPIbβ, or GPIX genes. The 22q11.2 deletion syndrome (22q11.2DS) is caused by a microdeletion on chromosome 22, which includes the GPIbβ gene, and is characterized by abnormal development of the pharyngeal apparatus and heart. Thus, patients with 22q11.2DS are obligate carriers for BSS. We evaluated two infants with BSS and performed the genetic analysis of the GPIbα, GPIbβ, or GPIX genes, and investigated the segregation of the mutation within the families. The status of the 22q11.2 deletion was examined by fluorescence in situ hybridization and single-nucleotide polymorphism array copy number analysis. DNA sequencing analysis revealed that the infants were compound heterozygous for a hemizygous mutation in the GPIbβ gene (p.Trp148X and p.Leu97Phe, respectively) and 22q11.2 deletion in the other chromosome. Both infants had the common 3Mb 22q11.2 deletion but did not show major phenotypic features of 22q11.2DS, such as developmental delay, cardiac defects, dysmorphic facial features, palatal anomalies, hypocalcemia, and immune deficiency. The 22q11.2DS would not have become clear if detailed molecular genetic analyses of BSS had not been performed. Our cases illustrate that a suspicion of 22q11.2 deletion is warranted in pediatric BSS patients with a mutation in the GPIbβ gene, even without remarkable symptoms.

Abnormal Whole Blood Thrombi in Humans with Inherited Platelet Receptor Defects

To delineate the critical features of platelets required for formation and stability of thrombi, thromboelastography and platelet aggregation measurements were employed on whole blood of normal patients and of those with Bernard-Soulier Syndrome (BSS) and Glanzmann’s Thrombasthenia (GT). We found that separation of platelet activation, as assessed by platelet aggregation, from that needed to form viscoelastic stable whole blood thrombi, occurred. In normal human blood, ristocetin and collagen aggregated platelets, but did not induce strong viscoelastic thrombi. However, ADP, arachidonic acid, thrombin, and protease-activated-receptor-1 and -4 agonists, stimulated both processes. During this study, we identified the genetic basis of a very rare double heterozygous GP1b deficiency in a BSS patient, along with a new homozygous GP1b inactivating mutation in another BSS patient. In BSS whole blood, ADP responsiveness, as measured by thrombus strength, was diminished, while ADP-induced platelet aggregation was normal. Further, the platelets of 3 additional GT patients showed very weak whole blood platelet aggregation toward the above agonists and provided whole blood thrombi of very low viscoelastic strength. These results indicate that measurements of platelet counts and platelet aggregability do not necessarily correlate with generation of stable thrombi, a potentially significant feature in patient clinical outcomes.

Whole Blood Impedance Aggregometry: A New Tool for Severe Inherited Platelet Disorder Diagnosis?

Abstract 5266Diagnosis and characterization of platelet function disorders may be challenging. It requires multiple laboratory data including the assessment of platelet functions. Platelet function analysis is most commonly performed using light transmission aggregometry (LTA). LTA is a time-consuming method requiring centrifugation steps and large blood volumes. It is difficult to perform in children and in cases of thrombocytopenia. In contrast, platelet aggregation in whole blood using impedancemetry (WBI) is a fast method, allows omission of centrifugation steps and performance of platelet function studies under more physiological conditions with small samples size. It is based on the change of resistance proportional to the amount of platelets sticking to two electrodes where an alternating current is applied. Multiplate® (for “multiple electrode aggregometry”, Dynabite Medical) is a new generation of WBI aggregometer using diluted blood and single-use test cells containing twin electrodes that reduce the variation of results. We have already showed the good Multiplate® performance concerning ristocetin-induced platelet aggregation in a population of 30 patients with characterized von Willebrand disease (Valarche et al, 2011). Our aim in this ongoing study was to assess the performance of WBI in patients with inherited platelet function disorders. We tested 8 patients including 2 unrelated patients with Glanzmann Thrombasthenia (GT), 2 unrelated patients with Bernard-Soulier Syndrome (BSS), 1 patient with Gray Platelet Syndrome (GPS) and 3 patients from the same family with a platelet type von Willebrand disease (PTVWD). GT, BSS, and PTVWD diagnosis were confirmed using genotyping. BSS and GPS patients had chronic thrombocytopenia. GT, BSS, GPS and 1/3 PTVWD had platelet function tests with LTA in parallel. WBI was performed on heparinized whole blood diluted at ½ in NaCl at 37°C and triggered using high (0.77 mg/mL, WBI RH) and low (0.5 mg/mL, WBI RL) final ristocetin concentrations, ADP (6.5 Âμ Mol, WBI ADP) and collagen (3.2 Âμg/mL, WBI Coll). Results were expressed in arbitrary unit (AU) corresponding to the area under the aggregation curve observed during 6 min. Normal ranges indicated in brackets were based on the mean +/− 2 SD of 30 healthy volunteers’ results. Results highlighted in grey are those out of the normal ranges (Table 1).Table 1:Results of the 8 patients with inherited platelet disorders.PatientsPlatelet count (109/L)WBI RH (AU) [>500]WBI RL (AU) [<150]WBI ADP (AU) [>550]WBI Coll (AU) [>500]GT 116923441443GT 224955417ND7BSS 134371119129BSS 230254733582GPS7916217ND42PTVWD22099493ND338PTVWD231116560ND1092PTVWD2341174168ND852All patients except those with PTVWD had decreased results with WBI. However, as expected, patients with GT had flat traces using WBI ADP and WBI Coll but normal or only decreased curves (234 – 554 AU) using WBI RH. On the opposite, BSS patients had flat traces using WBI RH but detectable curves using WBI ADP (191 – 335 AU) despite decreased platelet count. The thrombocytopenic GPS patient has a flat trace using WBI Coll and decreased WBI RH (162 AU). Members of the PTVWD family had normal results except a slightly increased result with WBI RH in 1/3 patients. Finally, LTA results performed in 6/8 patients were all in accordance with those of the WBI. In conclusion, in 8 patients with well characterized inherited platelet disorders, WBI was able to detect all abnormalities except PTVWD. In such cases, different ristocetin concentrations use might be critical to increase sensitivity. In our hands, WBI was able to discriminate disorders involving platelet glycoprotein (GP) IIb-IIIa from GP Ib-IX-V: GT patients exhibited flat traces using WBI ADP and WBI Coll, whereas patients with BSS exhibited flat traces with ristocetin. These preliminary results need to be confirmed on a larger population of patients with various characterized platelet function disorders. They suggest that WBI using the Multiplate® analyzer, which is a fast, easy and blood-preserving test, could be a valuable extra step before or in addition to the classic LTA for the diagnosis of severe inherited platelet disorders. Disclosures:No relevant conflicts of interest to declare.

Successful Outcome of Two Pregnancies in a Woman with Bernard Soulier Syndrome

Abstract 4676 INTRODUCTION:Bernard Soulier Syndrome (BSS) is a rare qualitative and quantitative autosomal recessive platelet disorder molecularly characterized by defective GPIb-IX-V membrane glycoprotein that is related to platelet adhesion and interaction with both Von Willebrand factor and endothelium. It is usually expressed by an enlarged bleeding time and decreased yet giant sized platelets, and can cause severe hemorrhagic complications during pregnancy. CASE REPORT:We present two successful pregnancies and labour management on a 33-year-old woman diagnosed in her childhood with BSS. Ristocetin induced platelet agglutination test and membrane glycoprotein study were performed to get the diagnosis. Furthermore, in the last year we have completed the diagnosis with platelet receptor expression flow citometry analysis, finding out depleted antiGPIbα and antiGPIX antibodies. Changes which prevent GPIbα for correct expression and processing were observed. Also integrin αIIbβ3 levels were risen due to the big sized platelets. A PCR product was obtained from genomic DNA using the GPIbα oligonucleotide pair; sense and antisense, and direct DNA sequencing of the amplification was performed in a model ABIprism 377 DNA sequencer (Perkin-Elmer Cetus). The direct sequencing of the sense strand of the 5x fragment shows in the patient the simultaneous presence of G and C nucleotids in 688 position, and the T and A nucleotids in 715 position. These punctual mutations give Ala200Pro substitutions and Cys209Ser in heterozygosis in mature peptide, respectively, Figure 1. The Ala200Pro mutation has not been reported in others cases of Bernard-Soullier, previously. The Cys209Ser has been described in other two Spanish patients: one in homozygosis and the other in heterozygosis associated to the mutation.Our patient presented hemorrhagic symptoms from 18 month old with an average of 40×103/μ l platelet count and increased platelet volume who required multiple platelet transfusions during her childhood. In the menarche main hemorrhagic manifestations consisted on methrorragia and epistaxis which were controlled with tranexamic acid. At the age of 26 a spontaneous ovarian cyst rupture required urgent hospital admission and two platelet pool transfusion. On December 2007 she consulted for epistaxis, and on September 2008 cesarean delivery was planned at 38th week of pregnancy; platelet count was 40×103/μ l, antiplatelet antibodies were negative for membrane glycoproteins and antiHLA-1 was positive against 98% donors tested. As a result, an HLA-compatible donor was searched, and two platelet apheresis were transfused one hour before surgery and every 12 hours after the procedure. The next 4 days one apheresis every 48 hours were transfused with no hemorrhagic symptoms. On January 2010, she presented with her second pregnancy; the patient had severe anemia, with high transfusion requirements; neither hemorrhage or hemolysis was detected, and even the possibility of a Munchausen syndrome was questioned. Unplanned caesarean was performed at 32th week because of the clinical instability of the patient, and this time we could not find on time an HLA-compatible donor, so two random platelet pools were transfused one hour before surgery and one platelet apheresis every day during 4 days after caesarean deliver, without any hemorrhagic complication. The newborn was asymptomatic with normal platelet count. The patientxs haemoglobin level returned to normal after five days of delivery. CONCLUSIONS:We present the successful labour management of two consecutive pregnancies on a young woman diagnosed with BSS. The low prevalence of this syndrome (less than one case per million population) explains the absence of well-established protocols for the management of pregnancy in this disease. Up to date there are only twelve reported cases of pregnancy and delivery in BSS patients, most of them presenting with severe hemorrhagic complications. Correct platelet transfusion is the mainstay of treatment, and screening for anti-platelet antibodies study is mandatory due to its high prevalence in these patients. Disclosures:No relevant conflicts of interest to declare. [Display omitted]

Quaternary Organization of GPIb-IX Complex and Insights Into Bernard-Soulier Syndrome Revealed by the Crystal Structures of GPIbβ Ectodomain and a GPIbβ/GPIX Chimera

Abstract 2195Platelet glycoprotein (GP)Ib-IX receptor complex contains three subunits, GPIbα, GPIbβ and GPIX, which assemble with a ratio of 1:2:1. Dysfunction in surface expression of the complex leads to Bernard-Soulier syndrome (BSS). We have crystallized the GPIbβ ectodomain (GPIbβE) and determined the structure to reveal a single leucine-rich repeat with N- and C-terminal disulfide bonded capping regions. The central region of the structure can be divided into concave parallel β-sheet and convex loops. The crystal structure of a GPIbβE/GPIXE chimera that contains three non-continguous convex loops of GPIX and retains a GPIbβ-binding site of GPIX (Mo et al. J. Thromb. Haemost. 7:1533–40, 2009) was also determined. The chimera, but not GPIbβE, forms a homotetramer in the crystal, revealing a quaternary interface between GPIbβ and GPIX ectodomains. Central to this interface is residue Tyr106 from GPIbβ that inserts into a shallow and largely hydrophobic pocket generated by two convex loops from GPIX. Mutagenesis studies confirmed this interface as a valid representation of interactions between GPIbβ and GPIX in the full-length complex. Eight GPIbβ missense mutations identified from BSS patients were examined in transiently transfected Chinese hamster ovary cells for changes to the GPIb-IX complex surface expression. Six of the eight mutations lead to secretion defect and/or misfolding of GPIbβE. In contrast, the other two mutations, A108P and P74R, were found to maintain normal secretion and folding of GPIbβE but were unable to support GPIX surface expression. The close structural proximity of these mutations to Tyr106 and the GPIbβE interface with GPIX indicates that residues Ala108 and Pro74 in GPIbβ are located at the GPIbβE/GPIXE interfaces. Based on the tetrameric arrangement of the chimera structure, we propose a structural model for the GPIb-IX complex that embodies its organizing principles and helps to provide mechanistic insights on its assembly, function and regulation. Disclosures:No relevant conflicts of interest to declare.

Six Novel Mutations Identified in the Glycoproteins Ib Alpha, Ib Beta and IX Genes Among Twenty-Two Unrelated Patients with Bernard-Soulier Syndrome in Brazil

Abstract 1156▪▪This icon denotes a clinically relevant abstract Introduction:Bernard-Soulier syndrome (BSS) is a rare hereditary bleeding disorder, caused by mutations within the glycoprotein (GP) Ib alpha, GP Ib beta and GP IX genes that encode three of four subunits of the platelet GP Ib-V-IX adhesion receptor. In the present study we evaluated the mutations involved in the diagnosis of BSS from twenty-two unrelated patients. Patients and Methods: All patients were followed in two large bleeding disorder reference centers in Brazil. The diagnosis of BSS was established based on the presence of mucocutaneous bleeding and macrotrombocytopenia, and was confirmed by platelet ristocetin aggregation and flow cytometry for the platelet GP Ib alpha (CD 42b), GP Ib beta (CD 42c), and GP IX (CD 42a). Available first- and second-degree relatives were also contacted for clinical, laboratory and molecular evaluation. Genomic DNA from all index cases was used for sequence analysis of the three genes, GP1BA, GP1BB and GP9, and the results were confirmed in relatives when available. Results: Twenty-two unrelated patients with the confirmed diagnosis of BSS were enrolled in this study. Among twenty-two index cases, twenty-one had one or two mutations identified, including six novel mutations. We also identified two mutations that have been previously reported, GP1BA C209S (Simsek, et al., 1994), and GP9 A140T (Wang, et al., 2004). The six novel mutations correspond to conserved regions, and they consist of two mutations in the GP1BA (L51R, and L99P), three in GP1BB (M-25A, L72R, and L112P), and one in GP9 (P52Q). One of these novel mutations, the GP1BB L112P was observed in twelve of twenty-two unrelated cases. PCR-restriction fragment length analysis of genomic DNA from a hundred normal unrelated controls were performed to evaluate the presence of GP1BA L99P and GP1BB L112P mutations by using the AlwN I and Alu I restriction enzymes, respectively. All controls were negative for both mutations. Interestingly, when we analyzed the relatives of the index cases indentified with the mutations GP1BA L99P and GP1BB M-25A, we found evidence of mild macrotrombocytopenia in the heterozygote carriers of these mutations. The relatives heterozygous for GP1BB L112P showed normal platelet count and morphology. However, in three index cases with mild macrotrombocytopenia, GP1BB L112P in heterozygosity was the only mutation identified. Furthermore, site-directed mutagenesis was carried out to evaluate the expression of the novel mutations GP1BA L51R, and GP1BA L99P. Compared to the GP1BA wild-type, both mutations were only minimally expressed in CHO bIX cells, which stably express GP Ib beta and GP IX. Conclusions: We identified in this study eight distinct mutations among twenty-two unrelated SBS patients, including six novel mutations. The GP1BB L112P mutation was found in twelve of the twenty-two index cases, suggesting that this could be due to a founder effect. Identifying such a frequent mutation in this population of BSS patients will be helpful for genetic diagnosis of this condition in Brazil. Furthermore these mutations significantly add to the mutation database of BSS and will inevitably provide insights into the function of GP Ib-V-IX. Disclosures:No relevant conflicts of interest to declare.

Correction of murine Bernard-Soulier syndrome by lentivirus-mediated gene therapy.

Bernard-Soulier syndrome (BSS) is an inherited bleeding disorder caused by a defect in the platelet glycoprotein (GP) Ib-IX-V complex. The main treatment for BSS is platelet transfusion but it is often limited to severe bleeding episodes or surgical interventions due to the risk of alloimmunization. We have previously reported successful expression of human GPIbα (hGPIbα) in human megakaryocytes using a lentiviral vector (LV) encoding human GP1BA under control of the platelet-specific integrin αIIb promoter (2bIbα). In this study, we examined the efficacy of this strategy for the gene therapy of BSS using GPIbα(null) as a murine model of BSS. GPIbα(null) hematopoietic stem cells (HSC) transduced with 2bIbα LV were transplanted into lethally irradiated GPIbα(null) littermates. Therapeutic levels of hGPIbα expression were achieved that corrected the tail bleeding time and improved the macrothrombocytopenia. Sequential bone marrow (BM) transplants showed sustained expression of hGPIbα with similar phenotypic correction. Antibody response to hGPIbα was documented in 1 of 17 total recipient mice but was tolerated without any further treatment. These results demonstrate that lentivirus-mediated gene transfer can provide sustained phenotypic correction of murine BSS, indicating that this approach may be a promising strategy for gene therapy of BSS patients.

Molecular basis of Bernard–Soulier syndrome in 27 patients from India

Bernard-Soulier syndrome (BSS) is an extremely rare (1:1 million) bleeding disorder of platelet adhesion, caused by defects in the glycoprotein (GP)Ib/IX/V complex. The diagnosis in 27 patients was based on low platelet count, presence of giant platelets and aggregometry studies. Flow cytometry to assess the surface GPIb/IX/V complex showed reduced (7.7-57%) expression. gDNA was screened for mutations in the GPIBA, GPIBB, GP9 genes using PCR-conformation sensitive gel electrophoresis (CSGE). Thirteen different disease-causing mutations, including missense (54%), frameshifts (38%) and nonsense (8%) mutations, were identified in 27 patients. Eleven of them were novel including five novel frameshifts (GPIbα: p.Gln97_98fsX113, p.Pro402_403fsX52; GPIbβ: p.Arg17fsX14; GPIX: p.Gly24fsX43, p. Pro130fs, a nonsense mutation (GPIX, p.94, Gln>X) and five novel missense mutations (GPIbα: p.492, Tyr>His; GPIbβ: p.65, Pro>Arg, p.129, Gln>His, p.132, Leu>Pro; GPIX: p.55, Phe>Cys). Interestingly, four common mutations, Cys8Arg (n = 6) and Phe55Ser (n = 2), Phe55Cys (n = 2) in GPIX and a novel 22-bp deletion in the GPIBB gene predicting p.Arg17fsX 14 (n = 10) were seen in 20 patients. The molecular data presented here is the largest series of BSS patients to be reported so far, adding significantly to the mutation database of this condition and also useful for its genetic diagnosis in India.