Somatic mutational landscape of hereditary hematopoietic malignancies caused by germline variants in RUNX1, GATA2, and DDX41

Individuals with germ line variants associated with hereditary hematopoietic malignancies (HHMs) have a highly variable risk for leukemogenesis. Gaps in our understanding of premalignant states in HHMs have hampered efforts to design effective clinical surveillance programs, provide personalized preemptive treatments, and inform appropriate counseling for patients. We used the largest known comparative international cohort of germline RUNX1, GATA2, or DDX41 variant carriers without and with hematopoietic malignancies (HMs) to identify patterns of genetic drivers that are unique to each HHM syndrome before and after leukemogenesis. These patterns included striking heterogeneity in rates of early-onset clonal hematopoiesis (CH), with a high prevalence of CH in RUNX1 and GATA2 variant carriers who did not have malignancies (carriers-without HM). We observed a paucity of CH in DDX41 carriers-without HM. In RUNX1 carriers-without HM with CH, we detected variants in TET2, PHF6, and, most frequently, BCOR. These genes were recurrently mutated in RUNX1-driven malignancies, suggesting CH is a direct precursor to malignancy in RUNX1-driven HHMs. Leukemogenesis in RUNX1 and DDX41 carriers was often driven by second hits in RUNX1 and DDX41, respectively. This study may inform the development of HHM-specific clinical trials and gene-specific approaches to clinical monitoring. For example, trials investigating the potential benefits of monitoring DDX41 carriers-without HM for low-frequency second hits in DDX41 may now be beneficial. Similarly, trials monitoring carriers-without HM with RUNX1 germ line variants for the acquisition of somatic variants in BCOR, PHF6, and TET2 and second hits in RUNX1 are warranted.

ANKRD26 is a new regulator of type I cytokine receptor signaling in normal and pathological hematopoiesis

Sustained ANKRD26 expression associated with germline ANKRD26 mutations causes Thrombocytopenia 2 (THC2), an inherited platelet disorder associated with leukemia predisposition. Some patients also present with erythrocytosis and/or leukocytosis. Using multiple human-relevant in vitro models (cell lines, primary patient cells and patient-derived iPSCs) we demonstrate for the first time that ANKRD26 is expressed during the early steps of erythroid, megakaryocyte and granulocyte differentiation, and is necessary for progenitor proliferation. As differentiation progresses, ANKRD26 expression is progressively silenced, to complete the cellular maturation of the three myeloid lineages. In primary cells, abnormal ANKRD26 expression in committed progenitors directly impacts the proliferation/differentiation balance for the three cell types. We show that ANKRD26 interacts with and crucially modulates the activity of MPL, EPOR and G-CSFR, three homodimeric type I cytokine receptors that regulate blood cell production. Higher than normal levels of ANKRD26 prevent the receptor internalization that leads to increased signaling and cytokine hypersensitivity. These findings afford evidence how an ANKRD26 overexpression or the absence of its silencing during differentiation is responsible of myeloid blood cell abnormalities in TCH2 patients.

A thrombopoietin receptor agonist to rescue an unusual platelet transfusion-induced reaction in a p.V1316M-associated von Willebrand disease type 2B patient

This report describes the first case of splenic injury in a patient with p.V1316M-associated von Willebrand disease type 2B (VWD2B) with chronic thrombocytopenia, successfully treated with nonoperative management including von Willebrand factor (VWF) replacement therapy, and platelet transfusions relayed by a thrombopoietin receptor agonist (TPO-RA, Eltrombopag). Eltrombopag was initially introduced to rescue an unusual post-platelet-transfusion reaction exacerbating the thrombocytopenia. In-depth analysis of the dramatic platelet count drop and VWF measurements timeline ruled out an allo-immune reaction and supported an alternative hypothesis of a sudden platelet clearance as a consequence of stress-induced release of abnormal VWF. One year later, a second life-threatening bleeding episode required urgent surgery successfully managed with VWF replacement therapy and platelet transfusions. Eltrombopag was further introduced in the post-surgery period to allow bleeding-free and platelet-transfusion-free successful recovery. Treatment decisions are particularly challenging in patients with VWD2B, and this case highlights how such decisions can benefit from understanding the molecular origin of platelet count fluctuations observed in these patients. Here, we successfully used a new therapeutic approach combining VWF-replacement therapy and initial platelet-transfusion relayed by TPO-RA to optimize patient management.

Inherited platelet diseases with normal platelet count: phenotypes, genotypes and diagnostic strategy

Inherited platelet disorders resulting from platelet function defects and a normal platelet count cause a moderate or severe bleeding diathesis. Since the description of Glanzmann thrombasthenia resulting from defects of ITGA2B and ITGB3, new inherited platelet disorders have been discovered, facilitated by the use of high throughput sequencing and genomic analyses. Defects of RASGRP2 and FERMT3 responsible for severe bleeding syndromes and integrin activation have illustrated the critical role of signaling molecules. Important are mutations of P2RY12 encoding the major ADP receptor causal for an inherited platelet disorder with inheritance characteristics that depend on the variant identified. Interestingly, variants of GP6 encoding the major subunit of the collagen receptor GPVI/FcRassociate only with mild bleeding. The numbers of genes involved in dense granule defects including Hermansky-Pudlak and Chediak Higashi syndromes continue to progress and are updated. The ANO6 gene encoding a Ca2+-activated ion channel required for phospholipid scrambling is responsible for the rare Scott syndrome and decreased procoagulant activity. A novel EPHB2 defect in a familial bleeding syndrome demonstrates a role for this tyrosine kinase receptor independent of the classical model of its interaction with ephrins. Such advances highlight the large diversity of variants affecting platelet function but not their production, despite the difficulties in establishing a clear phenotype when few families are affected. They have provided insights into essential pathways of platelet function and have been at the origin of new and improved therapies for ischemic disease. Nevertheless, many patients remain without a diagnosis and requiring new strategies that are now discussed.

Novel manifestations of immune dysregulation and granule defects in gray platelet syndrome

Gray platelet syndrome (GPS) is a rare recessive disorder caused by biallelic variants in NBEAL2 and characterized by bleeding symptoms, the absence of platelet α-granules, splenomegaly, and bone marrow (BM) fibrosis. Due to the rarity of GPS, it has been difficult to fully understand the pathogenic processes that lead to these clinical sequelae. To discern the spectrum of pathologic features, we performed a detailed clinical genotypic and phenotypic study of 47 patients with GPS and identified 32 new etiologic variants in NBEAL2. The GPS patient cohort exhibited known phenotypes, including macrothrombocytopenia, BM fibrosis, megakaryocyte emperipolesis of neutrophils, splenomegaly, and elevated serum vitamin B12 levels. Novel clinical phenotypes were also observed, including reduced leukocyte counts and increased presence of autoimmune disease and positive autoantibodies. There were widespread differences in the transcriptome and proteome of GPS platelets, neutrophils, monocytes, and CD4 lymphocytes. Proteins less abundant in these cells were enriched for constituents of granules, supporting a role for Nbeal2 in the function of these organelles across a wide range of blood cells. Proteomic analysis of GPS plasma showed increased levels of proteins associated with inflammation and immune response. One-quarter of plasma proteins increased in GPS are known to be synthesized outside of hematopoietic cells, predominantly in the liver. In summary, our data show that, in addition to the well-described platelet defects in GPS, there are immune defects. The abnormal immune cells may be the drivers of systemic abnormalities such as autoimmune disease.

Eltrombopag for the Treatment of Severe Inherited Thrombocytopenia

Inherited thrombocytopenias correspond to a group of hereditary disorders characterized by a reduced platelet count, platelet dysfunction, and a family history of thrombocytopenia. It is commonly associated with mucocutaneous bleeding. Thrombocytopenia results from mutations in genes involved in megakaryocyte differentiation, platelet formation, and clearance. Here we report on a patient presenting with severe syndromic inherited thrombocytopenia manifesting as spontaneous mucocutaneous bleeds, requiring frequent platelet transfusions. Thrombocytopenia was explained by the presence of 4 mutations in 3 hematopoietic transcription factor genes: FLI1, RUNX1, and ETV6. The patient was successfully treated with high-dose eltrombopag at 150 mg/day, an orally available non-peptide thrombopoietin receptor agonist. Since the start of treatment 23 months ago, the manifestations of bleeding have resolved, and no platelet transfusions or corticosteroids have been required. The patient has no clinical or laboratory evidence of myeloid malignancy so far.

Antithrombotic prophylaxis for surgery-associated venous thromboembolism risk in patients with inherited platelet disorders. The SPATA-DVT Study

Major surgery is associated with an increased risk of venous thromboembolism (VTE), thus the application of mechanical or pharmacologic prophylaxis is recommended. The incidence of VTE in patients with inherited platelet disorders (IPD) undergoing surgical procedures is unknown and no information on the current use and safety of thromboprophylaxis, particularly of low-molecular-weight-heparin in these patients is available. Here we explored the approach to thromboprophylaxis and thrombotic outcomes in IPD patients undergoing surgery at VTE-risk participating in the multicenter SPATA study. We evaluated 210 surgical procedures carried out in 155 patients with well-defined forms of IPD (VTE-risk: 31% high, 28.6% intermediate, 25.2% low, 15.2% very low). The use of thromboprophylaxis was low (23.3% of procedures), with higher prevalence in orthopedic and gynecological surgeries, and was related to VTE-risk. The most frequently employed thromboprophylaxis was mechanical and appeared to be effective, as no patients developed thrombosis, including patients belonging to the highest VTE-risk classes. Low-molecular-weight-heparin use was low (10.5%) and it did not influence the incidence of post-surgical bleeding or of antihemorrhagic prohemostatic interventions use. Two thromboembolic events were registered, both occurring after high VTE-risk procedures in patients who did not receive thromboprophylaxis (4.7%). Our findings suggest that VTE incidence is low in patients with IPD undergoing surgery at VTE-risk and that it is predicted by the Caprini score. Mechanical thromboprophylaxis may be of benefit in patients with IPD undergoing invasive procedures at VTE-risk and low-molecular-weight-heparin should be considered for major surgery.

MYH9-related disease mutations cause abnormal red blood cell morphology through increased myosin-actin binding at the membrane

MYH9-related disease (MYH9-RD) is a rare, autosomal dominant disorder caused by mutations in MYH9, the gene encoding the actin-activated motor protein non-muscle myosin IIA (NMIIA). MYH9-RD patients suffer from bleeding syndromes, progressive kidney disease, deafness, and/or cataracts, but the impact of MYH9 mutations on other NMIIA-expressing tissues remains unknown. In human red blood cells (RBCs), NMIIA assembles into bipolar filaments and binds to actin filaments (F-actin) in the spectrin-F-actin membrane skeleton to control RBC biconcave disk shape and deformability. Here, we tested the effects of MYH9 mutations in different NMIIA domains (motor, coiled-coil rod, or non-helical tail) on RBC NMIIA function. We found that MYH9-RD does not cause clinically significant anemia and that patient RBCs have normal osmotic deformability as well as normal membrane skeleton composition and micron-scale distribution. However, analysis of complete blood count data and peripheral blood smears revealed reduced hemoglobin content and elongated shapes, respectively, of MYH9-RD RBCs. Patients with mutations in the NMIIA motor domain had the highest numbers of elongated RBCs. Patients with mutations in the motor domain also had elevated association of NMIIA with F-actin at the RBC membrane. Our findings support a central role for motor domain activity in NMIIA regulation of RBC shape and define a new sub-clinical phenotype of MYH9-RD.

Bi-allelic Loss-of-Function CACNA1B Mutations in Progressive Epilepsy-Dyskinesia

The occurrence of non-epileptic hyperkinetic movements in the context of developmental epileptic encephalopathies is an increasingly recognized phenomenon. Identification of causative mutations provides an important insight into common pathogenic mechanisms that cause both seizures and abnormal motor control. We report bi-allelic loss-of-function CACNA1B variants in six children from three unrelated families whose affected members present with a complex and progressive neurological syndrome. All affected individuals presented with epileptic encephalopathy, severe neurodevelopmental delay (often with regression), and a hyperkinetic movement disorder. Additional neurological features included postnatal microcephaly and hypotonia. Five children died in childhood or adolescence (mean age of death: 9 years), mainly as a result of secondary respiratory complications. CACNA1B encodes the pore-forming subunit of the pre-synaptic neuronal voltage-gated calcium channel Ca_v2.2/N-type, crucial for SNARE-mediated neurotransmission, particularly in the early postnatal period. Bi-allelic loss-of-function variants in CACNA1B are predicted to cause disruption of Ca²⁺ influx, leading to impaired synaptic neurotransmission. The resultant effect on neuronal function is likely to be important in the development of involuntary movements and epilepsy. Overall, our findings provide further evidence for the key role of Ca_v2.2 in normal human neurodevelopment.

Rapid Aequorin Loading into Platelets in the Presence of DMSO - Characteristics of the Responses (Changes in Light Transmission and in Calcium) to Various Agonists

We have looked at different parameters which could modify platelet behaviour during and after aequorin loading in the presence of DMSO. There is a decreased platelet reactivity in response to ADP, PAF and A-23,187 which appears to be mainly due to the exposure to EGTA during washing and loading and the 1 ml volume of the test suspension. All the studied agonists (including PMA) which elicit aggregation are able to induce an intracellular Ca2+ change detected with the aequorin probe. By contrast, epinephrine alone induces neither aggregation nor Ca2+ rise, but potentiates the responses to ADP. Different consecutive phases in Ca2+ changes after stimulation with ADP, PMA and A-23,187 can be evidenced. In the presence of external Ca2+, the second component of the Ca2+ change evoked with ADP is dependent on aggregation and the subsequent TXA2 synthesis. When the external medium is Ca2+ depleted, the two Ca2+ peaks induced by ADP disappear whereas a Ca2+ rise persists (endogenous mobilization) with the other agonists, being independent of TXA2 and ADP release. Ca2+ mobilization parallels activation with A-23,187 but not with low concentrations of thrombin.

Comprehensive Cancer-Predisposition Gene Testing in an Adult Multiple Primary Tumor Series Shows a Broad Range of Deleterious Variants and Atypical Tumor Phenotypes

Multiple primary tumors (MPTs) affect a substantial proportion of cancer survivors and can result from various causes, including inherited predisposition. Currently, germline genetic testing of MPT-affected individuals for variants in cancer-predisposition genes (CPGs) is mostly targeted by tumor type. We ascertained pre-assessed MPT individuals (with at least two primary tumors by age 60 years or at least three by 70 years) from genetics centers and performed whole-genome sequencing (WGS) on 460 individuals from 440 families. Despite previous negative genetic assessment and molecular investigations, pathogenic variants in moderate- and high-risk CPGs were detected in 67/440 (15.2%) probands. WGS detected variants that would not be (or were not) detected by targeted resequencing strategies, including low-frequency structural variants (6/440 [1.4%] probands). In most individuals with a germline variant assessed as pathogenic or likely pathogenic (P/LP), at least one of their tumor types was characteristic of variants in the relevant CPG. However, in 29 probands (42.2% of those with a P/LP variant), the tumor phenotype appeared discordant. The frequency of individuals with truncating or splice-site CPG variants and at least one discordant tumor type was significantly higher than in a control population (χ2 = 43.642; p ≤ 0.0001). 2/67 (3%) probands with P/LP variants had evidence of multiple inherited neoplasia allele syndrome (MINAS) with deleterious variants in two CPGs. Together with variant detection rates from a previous series of similarly ascertained MPT-affected individuals, the present results suggest that first-line comprehensive CPG analysis in an MPT cohort referred to clinical genetics services would detect a deleterious variant in about a third of individuals.

Mutations of the integrin αIIb/β3 intracytoplasmic salt bridge cause macrothrombocytopenia and enlarged platelet α-granules

Rare gain-of-function mutations within the ITGA2B or ITGB3 genes have been recognized to cause macrothrombocytopenia (MTP). Here we report three new families with autosomal dominant (AD) MTP, two harboring the same mutation of ITGA2B, αIIbR995W, and a third family with an ITGB3 mutation, β3D723H. In silico analysis shows how the two mutated amino acids directly modify the salt bridge linking the intra-cytoplasmic part of αIIb to β3 of the integrin αIIbβ3. For all affected patients, the bleeding syndrome and MTP was mild to moderate. Platelet aggregation tended to be reduced but not absent. Electron microscopy associated with a morphometric analysis revealed large round platelets; a feature being the presence of abnormal large α-granules with some giant forms showing signs of fusion. Analysis of the maturation and development of megakaryocytes reveal no defect in their early maturation but abnormal proplatelet formation was observed with increased size of the tips. Interestingly, this study revealed that in addition to the classical phenotype of patients with αIIbβ3 intracytoplasmic mutations there is an abnormal maturation of α-granules. It is now necessary to determine if this feature is a characteristic of all mutations disturbing the αIIb R995/β3 D723 salt bridge.

A Novel Point Mutation of the Splicing Donor Site in the Intron 2 of the Plasmin Inhibitor Gene

Plasmin inhibitor (PI) is a major physiological inhibitor of plasminmediated fibrinolysis; hence, its deficiency results in a severe haemorrhagic diathesis. We analyzed the PI gene of a French boy apparently homozygous for PI deficiency and his heterozygous parents. Both alleles of the homozygous patient had a novel G to A transition at the consensus splicing donor site in the intron 2 of the PI gene. In an expression assay using the heterologous cells transfected with the mutant PI expression vector, 3 types of aberrant transcripts using a cryptic splicing donor site within the intron 2 were detected. All of these mRNAs had a stop codon upstream of the cryptic splicing site and encode only 25 amino acids, comprising the first 21 amino acids of the signal peptide (27 amino acids) plus 4 new amino acids. This mutant was designated as PI-Paris-Trousseau.

Bleeding risk of surgery and its prevention in patients with inherited platelet disorders

Excessive bleeding at surgery is a feared complication in patients with inherited platelet disorders. However, very few studies have evaluated the frequency of surgical bleeding in these hemorrhagic disorders. We performed a worldwide, multicentric, retrospective study to assess the bleeding complications of surgery, the preventive and therapeutic approaches adopted, and their efficacy in patients with inherited platelet disorders: the Surgery in Platelet disorders And Therapeutic Approach (SPATA) study. We rated the outcome of 829 surgical procedures carried out in 423 patients with well-defined forms of inherited platelet disorders: 238 inherited platelet function disorders and 185 inherited platelet number disorders. Frequency of surgical bleeding was high in patients with inherited platelet disorders (19.7%), with a significantly higher bleeding incidence in inherited platelet function disorders (24.8%) than in inherited platelet number disorders (13.4%). The frequency of bleeding varied according to the type of inherited platelet disorder, with biallelic Bernard Soulier syndrome having the highest occurrence (44.4%). Frequency of bleeding was predicted by a pre-operative World Health Organization bleeding score of 2 or higher. Some types of surgery were associated with a higher bleeding incidence, like cardiovascular and urological surgery. The use of pre-operative pro-hemostatic treatments was associated with a lower bleeding frequency in patients with inherited platelet function disorders but not in inherited platelet number disorders. Desmopressin, alone or with antifibrinolytic agents, was the preventive treatment associated with the lowest bleedings. Platelet transfusions were used more frequently in patients at higher bleeding risk. Surgical bleeding risk in inherited platelet disorders is substantial, especially in inherited platelet function disorders, and bleeding history, type of disorder, type of surgery and female sex are associated with higher bleeding frequency. Prophylactic pre-operative pro-hemostatic treatments appear to be required and are associated with a lower bleeding incidence.

Haematological spectrum and genotype-phenotype correlations in nine unrelated families with RUNX1 mutations from the French network on inherited platelet disorders

Background

Less than 50 patients with FPD/AML (OMIM 601309) have been reported as of today and there may an underestimation. The purpose of this study was to describe the natural history, the haematological features and the genotype-phenotype correlations of this entity in order to, first, screen it better and earlier, before leukaemia occurrence and secondly to optimize appropriate monitoring and treatment, in particular when familial stem cell transplantation is considered.

Methods

We have investigated 41 carriers of RUNX1 alteration belonging to nine unrelated French families with FPD/AML and two syndromic patients, registered in the French network on rare platelet disorders from 2005 to 2015.

Results

Five missense, one non-sense, three frameshift mutations and two large deletions involving several genes including RUNX1 were evidenced. The history of familial leukaemia was suggestive of FPD/AML in seven pedigrees, whereas an autosomal dominant pattern of lifelong thrombocytopenia was the clinical presentation of two. Additional syndromic features characterized two large sporadic deletions. Bleeding tendency was mild and thrombocytopenia moderate (>50 x10⁹/L), with normal platelet volume. A functional platelet defect consistent with a δ-granule release defect was found in ten patients regardless of the type of RUNX1 alteration. The incidence of haematological malignancies was higher when the mutated RUNX1 allele was likely to cause a dominant negative effect (19/34) in comparison with loss of function alleles (3/9). A normal platelet count does not rule out the diagnosis of FPD/AML, since the platelet count was found normal for three mutated subjects, a feature that has a direct impact in the search for a related donor in case of allogeneic haematopoietic stem cell transplantation.

Conclusions

Platelet dysfunction suggestive of defective δ-granule release could be of values for the diagnosis of FPD/AML particularly when the clinical presentation is an autosomal dominant thrombocytopenia with normal platelet size in the absence of familial malignancies. The genotype-phenotype correlations might be helpful in genetic counselling and appropriate optimal therapeutic management.

Childhood diagnosis of genetic thrombocytopenia with mutation in the ankyrine repeat domain 26 gene

The most common diagnosis for pediatric thrombocytopenia is immune thrombocytopenia. Nevertheless, in atypical cases, the hypothesis of an inherited thrombocytopenia has to be investigated. We report a series of cases of a newly described entity, genetic thrombocytopenia with mutation in the ankyrine 26 gene, diagnosed from the exploration of five pediatric cases of thrombocytopenia. This entity is characterized by a moderate thrombocytopenia with normal mean platelet volume, and poorly bleeding. Its transmission is autosomal dominant. Final diagnosis is made by sequencing of a short DNA region of ANKRD26 gene. This pathology can be considered as an hematological malignancy predisposition syndrome.

CONCLUSION

We report the first cohort of pediatric patients diagnosed with thrombocytopenia with mutation in the ankyrine 26. The aim is to underline the specificities of this entity in children and bring it to the knowledge of pediatricians who may be in first place to manage these patients.

WHAT IS KNOWN

• Genetic thrombocytopenia with mutation in the ankyrine 26 gene is a recently described entity, which seems to be considered as a predisposition for hematologic malignancies. • The first cohort has been reported in 2011, by Noris et al., in 78 Italian adult patients. What is New: • We describe clinical and biological features of the first pediatric cohort diagnosed with genetic thrombocytopenia with mutation in the ankyrine 26 gene. • It seemed important to consider the pediatric specificities of this entity to enable pediatricians to investigate, diagnose, and manage pediatric patients and their families.

Jacobsen syndrome: Advances in our knowledge of phenotype and genotype

In 1973, the Danish geneticist Petrea Jacobsen described a three-generation family in which the proband carried a presumed terminal deletion at the end of the long arm of chromosome 11 (11q). This patient had dysmorphic features, congenital heart disease, and intellectual disability. Since Dr. Jacobsen's initial report, over 200 patients with Jacobsen syndrome have been reported, suggesting that Jacobsen syndrome is a contiguous gene disorder. With the advent of high resolution deletion mapping and the completion of the human genome sequencing project, a comprehensive genotype/phenotype analysis for Jacobsen syndrome became possible. In this article, we review research describing individual causal genes in distal 11q that contribute to the overall Jacobsen syndrome clinical phenotype. Through a combination of human genetics and the use of genetically engineered animal models, causal genes have been identified for the clinical problems in JS that historically have caused the greatest morbidity and mortality: congenital heart disease, the Paris-Trousseau bleeding disorder, intellectual disability, autism, and immunodeficiency. Insights gained from these studies are being applied for future drug development and clinical trials, as well as for a potential strategy for the prevention of certain forms of congenital heart disease. The results of these studies will likely not only improve the prognostic and therapeutic approaches for patients with Jacobsen syndrome, but also for the general population afflicted with these problems.

Analysis of 65 pregnancies in 34 women with five different forms of inherited platelet function disorders

This study evaluated 65 pregnancies in 34 women with five different inherited platelet function disorders. Gestation was similar to that of the general population. Severe bleeds requiring blood transfusions were observed in 50% of deliveries in Glanzmann thrombasthenia (GT), but not in the patients with delta storage pool disease, Hermansky-Pudlak syndrome, P2Y12 defect or defect of thromboxane A2 receptor. Of note, severe haemorrhage also occurred in women with GT who had received prophylactic platelet transfusions, suggesting that better preventive treatments are required. Diagnosis and degree of spontaneous bleeding tendency before pregnancy were reliable parameters to predict the delivery-related bleeding risk.

Analysis of 339 pregnancies in 181 women with 13 different forms of inherited thrombocytopenia

Pregnancy in women with inherited thrombocytopenias is a major matter of concern as both the mothers and the newborns are potentially at risk of bleeding. However, medical management of this condition cannot be based on evidence because of the lack of consistent information in the literature. To advance knowledge on this matter, we performed a multicentric, retrospective study evaluating 339 pregnancies in 181 women with 13 different forms of inherited thrombocytopenia. Neither the degree of thrombocytopenia nor the severity of bleeding tendency worsened during pregnancy and the course of pregnancy did not differ from that of healthy subjects in terms of miscarriages, fetal bleeding and pre-term births. The degree of thrombocytopenia in the babies was similar to that in the mother. Only 7 of 156 affected newborns had delivery-related bleeding, but 2 of them died of cerebral hemorrhage. The frequency of delivery-related maternal bleeding ranged from 6.8% to 14.2% depending on the definition of abnormal blood loss, suggesting that the risk of abnormal blood loss was increased with respect to the general population. However, no mother died or had to undergo hysterectomy to arrest bleeding. The search for parameters predicting delivery-related bleeding in the mother suggested that hemorrhages requiring blood transfusion were more frequent in women with history of severe bleedings before pregnancy and with platelet count at delivery below 50 × 10(9)/L.

Thrombocytopenia-associated mutations in the ANKRD26 regulatory region induce MAPK hyperactivation

Point mutations in the 5' UTR of ankyrin repeat domain 26 (ANKRD26) are associated with familial thrombocytopenia 2 (THC2) and a predisposition to leukemia. Here, we identified underlying mechanisms of ANKRD26-associated thrombocytopenia. Using megakaryocytes (MK) isolated from THC2 patients and healthy subjects, we demonstrated that THC2-associated mutations in the 5' UTR of ANKRD26 resulted in loss of runt-related transcription factor 1 (RUNX1) and friend leukemia integration 1 transcription factor (FLI1) binding. RUNX1 and FLI1 binding at the 5' UTR from healthy subjects led to ANKRD26 silencing during the late stages of megakaryopoiesis and blood platelet development. We showed that persistent ANKRD26 expression in isolated MKs increased signaling via the thrombopoietin/myeloproliferative leukemia virus oncogene (MPL) pathway and impaired proplatelet formation by MKs. Importantly, we demonstrated that ERK inhibition completely rescued the in vitro proplatelet formation defect. Our data identify a mechanism for development of the familial thrombocytopenia THC2 that is related to abnormal MAPK signaling.

The abnormal proplatelet formation in MYH9-related macrothrombocytopenia results from an increased actomyosin contractility and is rescued by myosin IIA inhibition

BACKGROUND

Mutations in the MYH9 gene cause autosomal dominant MYH9-related diseases (MYH9-RD) that associate macrothrombocytopenia with various other clinical conditions. The mechanisms giving rise to giant platelets remain poorly understood.

OBJECTIVES/PATIENTS

To study the proplatelet formation (PPF) derived from megakaryocytes (MKs) generated in vitro from 11 patients with MYH9-RD with different mutations, compared with controls.

METHODS

Proplatelet formation from cultured patients' MKs was evaluated with or without blebbistatin or the ROCK inhibitor Y27632. Myosin IIA and actin distribution were studied in spreading MKs on different surfaces by immunoconfocal analysis. Kinetic studies of contractility were performed on spreading MKs and the impact of blebbistatin on the maturation of the patients' MKs was evaluated by electron microscopy.

RESULTS AND CONCLUSIONS

We show that in vitro MKs of 11 patients formed significantly fewer proplatelets than controls. MKs from MYH9-RD displayed an abnormal spreading on polylysine, fibronectin and collagen, with a disorganized actin network and a marked increase in stress fiber formation. Traction force microscopy studies demonstrated an elevated level of contractile forces in adherent mutated MKs. The myosin II inhibitor blebbistatin and the ROCK inhibitor Y27632 both rescued the proplatelet formation defect and normalized the ultrastructural characteristics of MYH9-RD MKs. Altogether, our results show that in MYH9-RD, mutations modify the overall MYH9 function and provoke a proplatelet defect through an excess of actomyosin contractility in spreading MKs. These results may promote new therapeutic strategies aimed at reducing this actomyosin contractility.

First successful use of eltrombopag before surgery in a child with MYH9-related thrombocytopenia

MYH9-related disease (MYH9-RD) is one of the most frequent autosomal-dominant forms of inherited macrothrombocytopenias and is caused by mutations in MYH9 (nonmuscle myosin IIA), the gene coding for the heavy chain of the nonmuscle myosin IIA. Affected individuals can present with isolated thrombocytopenia, and whereas only some will have bleeding events requiring intervention, nearly all will require the use of prophylactic platelet transfusions before surgery. Here we report the first prophylactic use of eltrombopag before surgery in a child with MYH9-RD. Our patient was a 13-year-old girl with an MYH9 S96L missense mutation who required a tympanoplasty due to chronic otitis media. Pretreatment microscopic platelet count was 10 × 10(9)/L. The child was treated with eltrombopag starting 4 weeks before her planned surgery. On the day of surgery her platelet count was 70 × 10(9)/L. She required no platelet transfusions and no abnormal bleeding was reported either during surgery or postoperatively. Given these results, the first reported in a child, we suggest that the use of this thrombopoietic agent should be further evaluated as a useful presurgical prophylactic option in this hereditary thrombocytopenia, thus avoiding the use of platelet transfusions and their associated risks, which include alloimmunization and the transmission of infectious agents.

Comparative evaluation of Tissue factor and Thrombomodulin activity changes during normal and idiopathic early and late foetal loss: the cause of hypercoagulability?

Various components of the coagulation and fibrinolytic pathways are involved in normal embryonic implantation, trophoblast invasion, placentation, and recurrent miscarriages are characterized by defective placentation and microthrombi in the placental vasculature. Although recurrent miscarriage is a heterogeneous condition the relationship between abnormalities in the haemostatic pathways and pregnancy outcome is increasingly recognized. The challenge we face is how to discriminate between women who are destined to miscarry from those whose pregnancy will be successful. Considering the crucial role of thrombomodulin and tissue factor in coagulation and in embryonic development, we have performed a study using specific assays for thrombomodulin, tissue factor activity and procoagulant phospholipids in association with other parameters in 30 early (under 12weeks) and 32 late (over 22weeks) pregnancy loss women and compared them with 62 normal pregnancy women and 35 non-pregnant women. Plasma levels of tissue factor activity, thrombomodulin activity, and procoagulant phospholipids were significantly higher in patients than in control subjects. In addition the tissue factor activity/free tissue factor pathway inhibitor ratio was higher in patients than in controls. Interestingly, patients with late pregnancy loss had higher tissue factor activity/free tissue factor pathway inhibitor ratios than patients with early pregnancy loss. The combinations of these different parameters reveal an increase in procoagulant activity which could be secondary to endothelial damage or coagulation activation and then are involved in the pathogenesis of pregnancy loss. Their simultaneous measurement of these activities might provide a new tool to assess the prognosis of pregnancy loss.

Myosin IIA associates with NK cell lytic granules to enable their interaction with F-actin and function at the immunological synapse (134.13)

NK cell cytotoxicity requires the formation of an actin-rich immunological synapse (IS) with a target cell and the polarization of perforin-containing lytic granules toward the IS. Following the polarization of lytic granules, they traverse through the actin-rich IS to join the NK cell membrane in order for the directed secretion of their contents to occur. We examined the role of myosin IIA in facilitating this pre-final step in lytic NK cell IS function. Lytic granules in and derived from a human NK cell line, or ex vivo human NK cells, were constitutively associated with myosin IIA. When isolated using density gradients, myosin IIA-associated NK cell lytic granules directly bound to F-actin and the interaction was sensitive to the presence of ATP under conditions of flow. In NK cells from patients with a nonsense mutation in myosin IIA, NK cell cytotoxicity, lytic granule penetration into F-actin at the IS, and interaction of isolated granules with F-actin were all decreased. Similarly, inhibition of myosin function also diminished the penetration of lytic granules into F-actin at the IS, as well as their final approach to and their dynamics at the IS. Thus, NK cell lytic granule-associated myosin IIA enables their interaction with actin and final transit through the actin-rich IS to the synaptic membrane, and can be defective in the context of naturally occurring human myosin IIA mutation.

Supported by NIH grants R01 AI067946 (JSO) and T32-GM07229 (KBS).

[Tolerance and efficacy of mefloquine as the first line treatment of uncomplicated P. falciparum malaria in children]

INTRODUCTION

Given the national therapeutic guidelines in France, halofantrine represents the first line treatment of uncomplicated Plasmodium falciparum (P. falciparum) malaria in children. But several disadvantages exist using halofantrine in paediatrics.

OBJECTIVES

The primary objective of this study is to evaluate the tolerance and the efficacy of mefloquine as the first line treatment of uncomplicated P. falciparum malaria in a paediatric emergency department. The secondary objective of the study is to evaluate whether symptomatic measures may improve the gastrointestinal tolerance of mefloquine.

PATIENTS AND METHODS

This retrospective observational cohort study includes all the patients who have been treated for acute uncomplicated P. falciparum malaria in the paediatric emergency department of the Hospital Trousseau (Paris, France) in 2003.

RESULTS

First line treatment was mefloquine in 35 children. Early vomiting occurred in 22 (63%) cases. All children responded to mefloquine therapy except two children who had persistent vomiting early after mefloquine therapy and required intravenous quinine. Those two children had initial vomiting. Light meal and metopimazine prophylaxis did not precede mefloquine intake in those two children.

CONCLUSION

This study suggests that mefloquine treatment of uncomplicated P. falciparum malaria is effective and well tolerated in children. Furthermore, a light meal and metopimazine prophylaxis preceding mefloquine intake may improve its gastrointestinal tolerance.

[Transient myeloproliferative disorder in a neonate without Down syndrome]

We report a new case of transient myeloproliferative disorder (TMD) in a non Down syndrome neonate. The cytogenetic and molecular studies within from the blood blast cells identified a trisomy 21 and a partial deletion in exon 2 of the transcription factor GATA1. Spontaneous regression of the TMD was achieved at the age of 1 month as the clonal and molecular abnormalities. A survey by periodic cytological examinations of peripheral blood cells and GATA1 mutation analysis was instituted since three years and has not detected up to date acute leukaemia.

Cardioprotective effect of spontaneous activity

In the perspective of giving a better understanding of the cardioprotective effects attributable to the tandem low caloric intake and training, Lou/C rats would be an interesting model since these animals exhibit spontaneously these two characteristics for months, without any dietary manipulations or stressor stimuli. No information was so far available on their cardiac function. Therefore, the aim of this pilot study was (i) to document cardiac function before and after ischemia in this strain, and (ii) to investigate whether spontaneous wheel-running activity can improve the ability of cardiac muscle to recover its function after an ischemic period. Cardiac mechanical and metabolic functions were measured in isolated Langendorff hearts from Wistar sedentary, Lou/C sedentary, and Lou/C wheel-running male rats submitted to a 20-min low-flow ischemia and 20-min reperfusion. In Lou/C sedentary rats, rate-pressure product, an index of cardiac work, was decreased before ischemia as compared to Wistar sedentary animals (- 24 %, p < 0.05). After ischemia, cardiac mechanical function recovery did not significantly differ between these two groups. Nevertheless, flux of non-oxidative glycolysis was lower before and after ischemia in Lou/C sedentary animals than in Wistar sedentary rats. In Lou/C rats, during normoxic perfusion, wheel-running activity significantly decreased heart rate (- 15 %), oxygen consumption (- 2.2 %) and cardiac efficiency (- 37 %), whereas coronary flow and flux of non-oxidative glycolysis were significantly increased (+ 15 % and + 263 %, respectively). After ischemia, recovery of cardiac mechanical function and cardiac efficiency were improved in Lou/C wheel-running rats versus Lou/C sedentary animals (p < 0.05). In conclusion, the impact of ischemia-reperfusion is similar between Lou/C- and Wistar sedentary rats. Spontaneous wheel-running activity decreases cardiac efficiency before ischemia and confers a protection against ischemia- and reperfusion-induced injury in isolated Lou/C rat hearts.

Le syndrome MYH9 : à propos d'une nouvelle observation et de la mise en évidence d'une nouvelle mutation du gène MYH9

INTRODUCTION

Familial macrothrombocytopenias are a group of rare autosomal dominant platelet disorders including many syndromes in particular the May-Hegglin anomaly. They are characterized by thrombocytopenia with giant platelets and in some cases neutrophilic inclusions in peripheral blood granulocytes. Recently these different clinical entities have been demonstrated to be linked to mutations in the same gene, MYH9.

CASE REPORT

We report in a young African woman presenting as a May-Hegglin anomaly a new mutation of the MYH9 gene. In regard of this case we present a brief review of the MYH9 syndrome.

CONCLUSION

The MYH9 syndrome includes now several clinical entities who share some common clinical and biological characteristics such as a thrombocytopenia with giant platelets, presence or absence of other manifestations including Dohle like bodies, nephritis, sensorineural hearing loss, cataract. We report a new case in which a new mutation of the MYH9 gene was evidenced.

High dietary sucrose triggers hyperinsulinemia, increases myocardial β-oxidation, reduces glycolytic flux and delays post-ischemic contractile recovery

Although the causal relationship between insulin resistance (IR) and hypertension is not fully resolved, the importance of IR in cardiovascular dysfunction is recognized. As IR may follow excess sucrose or fructose diet, the aim of this study was to test whether dietary starch substitution with sucrose results in myocardial dysfunction in energy substrate utilization and contractility during normoxic and post-ischemic conditions. Forty-eight male Wistar rats were randomly allocated to three diets, differing only in their starch to sucrose (S) ratio (13, 2 and 0 for the Low S, Middle S and High S groups, respectively), for 3 weeks. Developed pressure and rate x pressure product (RPP) were determined in Langendorff mode-perfused hearts. After 30 min stabilization, hearts were subjected to 25 min of total normothermic global ischemia, followed by 45-min reperfusion. Oxygen consumption, beta-oxidation rate (using 1-13C hexanoate and Isotopic Ratio Mass Spectrometry of CO2 produced in the coronary effluent) and flux of non-oxidative glycolysis were also evaluated. Although fasting plasma glucose levels were not affected by increased dietary sucrose, high sucrose intake resulted in increased plasma insulin levels, without significant rise in plasma triglyceride and free fatty acid concentrations. Sucrose-rich diet reduced pre-ischemic baseline measures of heart rate, RPP and non-oxidative glycolysis. During reperfusion, post-ischemic recovery of RPP was impaired in the Middle S and High S groups, as compared to Low S, mainly due to delayed recovery of developed pressure, which by 45 min of reperfusion eventually resumed levels matching Low S. At the start of reperfusion, delayed post-ischemic recovery of contractile function was accompanied by: (i) reduced lactate production; (ii) decreased lactate to pyruvate ratio; (iii) increased beta-oxidation; and (iv) depressed metabolic efficiency. In conclusion, sucrose rich-diet increased plasma insulin levels, in intact rat, and increased cardiac beta-oxidation and coronary flow-rate, but reduced glycolytic flux and contractility during normoxic baseline function of isolated perfused hearts. Sucrose rich-diet impaired early post-ischemic recovery of isolated heart cardiac mechanical function and further augmented cardiac beta-oxidation but reduced glycolytic and lactate flux.

Chronic electrostimulation after nerve repair by self-anastomosis: effects on the size, the mechanical, histochemical and biochemical muscle properties

This study tests the effects of chronic electrostimulation on denervated/reinnervated skeletal muscle in producing an optimal restoration of size and mechanical and histochemical properties. We compared tibialis anterior muscles in four groups of rats: in unoperated control (C) and 10 weeks following nerve lesion with suture (LS) in the absence of electrostimulation and in the presence of muscle stimulation with either a monophasic rectangular current (LSEm) or a biphasic modulated current (LSEb). The main results were (1) muscle atrophy was reduced in LSEm (-26%) while it was absent in LSEb groups (-8%); (2) the peak twitch amplitude decreased in LS and LSEm but not in LSEb groups, whereas the contraction time was shorter; (3) muscle reinnervation was associated with the emergence of type IIC fibers and proportions of types I, IIA and IIB fibers recovered in the superficial portion of LSEb muscles; (4) the ratio of oxidative to glycolytic activities decreased in the three groups with nerve injury and repair; however, this decrease was more accentuated in LSEm groups. We conclude that muscle electrostimulation following denervation and reinnervation tends to restore size and functional and histochemical properties during reinnervation better than is seen in unstimulated muscle.

Mitochondrial H2O2 production is reduced with acute and chronic eccentric exercise in rat skeletal muscle

Oxidative stress with acute/chronic exercise has been so far examined using exercise involving a combination of concentric and eccentric contractions, but skeletal muscles are likely to be injured to a greater extent by pliometric contractions. In the present study, the effects of acute and chronic bouts of downhill running exercise on mitochondrial hydrogen peroxide (H2O2) generation (fluorimetric detection of a dimer with homovanillic acid in presence of horseradish peroxidase) and oxygen consumption in conjunction with antioxidant enzymes activity were examined. The results show that acute eccentric exercise was accompanied by a significantly reduced mitochondrial H2O2 production that is likely due to a decrease in complex I of the electron transport chain (ETC). On the other hand, eccentric training leads to positive adaptations, reflected by a higher citrate synthase activity and decreased mitochondrial H2O2 production. The decrease in mitochondrial H2O2 cannot be attributed to alterations in antioxidant capacities but rather to changes in mitochondrial membrane composition characterized by an increased polyunsaturated to saturated fatty acids ratio, and decreased contents in arachidonic acid and plasmalogens. These results suggest that changes in mitochondrial membrane properties with eccentric training can affect H2O2 production by muscle mitochondria. It is hypothesized that these changes resulted in a mild uncoupling sufficient to reduce electron back flow through complex I of the ETC, the major generator of reactive oxygen species by skeletal muscle mitochondria.

Skeletal muscle HSP72 and norepinephrine response to static magnetic field in rat

The present work was undertaken in order to investigate the noradrenergic system and skeletal muscle heat shock protein 72 (HSP72) response to static magnetic field (MF) in male rats. At thermoneutrality (25 degrees C), the exposition of rats 1 hour/day for 5 consecutive days to MF of 128 mT (m tesla) induced an increase in norepinephrine content in gastrocnemius muscle (+25%, p < 0.05) but had no effect at 67 mT (+1%, p > 0.05), indicating a stimulatory effect of sub-acute MF exposure on the noradrenergic system activity. Moreover, exposed rats to MF displayed a non-significant increase of HSP72 levels in gastrocnemius muscles (+29%, p > 0.05). The results indicate that noradrenergic systems in rat's gastrocnemius muscles are affected by MF exposure. Interestingly, sub-acute exposure insufficiency increased HSP72 levels in gastrocnemius muscles.

Molecular study of the hematopoietic zinc finger gene in three unrelated families with gray platelet syndrome

Hematopoietic zinc finger (HZF) null mice have features reminiscent of patients with gray platelet syndrome (GPS), a rare inherited bleeding disorder. This similarity has suggested that HZF deregulation might be involved in the human disease. The sequence of the eight exons of the HZF gene as well as the study of its expression in blood samples from five patients belonging to three different families did not reveal any modifications when compared with healthy donors. This study indicates that HZF is unlikely to be responsible for GPS.

Age-related sensitivity to lung oxidative stress during ozone exposure

As immature and aged rats could be more sensitive to ozone (O(3))-linked lung oxidative stress we have attempted to shed more light on age-related susceptibility to O(3) with focusing our interest on lung mitochondrial respiration, reactive oxygen species (ROS) production and lung pro/antioxidant status. For this purpose, we exposed to fresh air or O(3) (500 ppb 12 h per day, for 7 days) 3 week- (immature), 6 month- (adult) and 20 month-old rats (aged). We determined, in lung, H(2)O(2) release by mitochondria, activities of major antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT)], heat shock protein (HSP(72)) content and 8-oxodG and dG-HNE nDNA contents, as DNA oxidative damage markers. In adult rats we did not observe alteration of pro/antioxidant status. In contrast to adults, immature rats exposed to O(3) higher nDNA 8-oxodG content and HSP(72) and without antioxidant enzymes modification. Aged rats displayed mild uncoupled lung mitochondria, increased SOD and GPx activities, and higher 8-oxodG content after O(3) exposure. Thus, in contrast to adults, immature and aged rats displayed lung oxidative stress after O(3) exposure. Higher sensitivity of immature to O(3) was partly related to ventilatory parameters and to the absence of antioxidant enzyme response. In aged rats, the increase in cytosolic SOD and GPx activities during O(3) exposure was not sufficient to prevent the impairment in mitochondrial function and accumulation in lung 8- oxodG. Finally, we showed that mitochondria seem not to be a major source of ROS under O(3) exposure.

Adaptive changes in cardiac myosin heavy chain and creatine kinase isozymic profiles in rats native of altitude

AIM

The developmental changes in the myosin heavy chain (MHC) profile, creatine kinase (CK) and lactate dehydrogenase (LDH) activities and isozyme expression occurring in heart were examined in rats born and living at altitude (La Paz, Bolivia, 3700 m, H(LP)) for 16 generations. We hypothesized that H(LP) rats respond differently to hypoxia than rats born and living at sea level, and secondarily exposed to altitude during 3 weeks (H(3W)).

METHODS

The cardiac expression of MHC, CK and LDH was studied in left (LV) and right ventricle (RV) of H(LP) animals 1, 2, 3, 4 and 18 weeks after birth, and compared with control normoxic (C groups) and H(3W) animals.

RESULTS

Rats secondarily exposed to hypoxia showed a lower alpha-MHC content than C or H(LP) rats in both LV and RV, 3 weeks after birth (P < 0.05), consistent with a delay in the maturation of the heart contractile phenotype. A global increase in the total CK activity was observed in the LV of H(3W) animals in comparison with C rats (P < 0.05), while no change was reported in H(LP) animals. In both ventricles, M-LDH activity was higher in H(3W) than in H(LP) and C rats (P < 0.05). The relative amount of alpha-MHC decreased by 20% in RV of 18-week-old H(LP) and H(3W) rats in comparison with C animals, consistent with the hypoxia-induced ventricular enlargement (P < 0.01). An increased activity of the foetal B-CK subunit was observed in both LV and RV of H(3W) rats in comparison with H(LP) and C animals (P < 0.05).

CONCLUSION

This study demonstrates that rats native and living at altitude for several generations present some features relevant to genetic selection to altitude.

The 11q terminal deletion disorder: a prospective study of 110 cases

We performed a prospective study of 110 patients (75 not previously published) with the 11q terminal deletion disorder (previously called Jacobsen syndrome), diagnosed by karyotype. All the patients have multiple dysmorphic features. Nearly all the patients (94%) have Paris-Trousseau syndrome characterized by thrombocytopenia and platelet dysfunction. In total, 56% of the patients have serious congenital heart defects. Cognitive function ranged from normal intelligence to moderate mental retardation. Nearly half of the patients have mild mental retardation with a characteristic neuropsychiatric profile demonstrating near normal receptive language ability, but mild to moderate impairment in expressive language. Ophthalmologic, gastrointestinal, and genitourinary problems were common, as were gross and fine motor delays. Infections of the upper respiratory system were common, but no life-threatening infections were reported. We include a molecular analysis of the deletion breakpoints in 65 patients, from which genetic "critical regions" for 14 clinical phenotypes are defined, as well as for the neuropsychiatric profiles. Based on these findings, we provide a comprehensive set of recommendations for the clinical management of patients with the 11q terminal deletion disorder.