Structural and Functional Characterization of Four Novel Fibrinogen Mutations in FGB Causing Congenital Fibrinogen Disorder.

Congenital fibrinogen disorders are caused by mutations in genes coding for fibrinogen and may lead to various clinical phenotypes. Here, we present a functional and structural analysis of 4 novel variants located in the FGB gene coding for fibrinogen Bß chain-heterozygous missense BßY416C and BßA68S, homozygous nonsense BßY345*, and heterozygous nonsense BßW403* mutations. The cases were identified by coagulation screening tests and further investigated by various methods. Fibrin polymerization had abnormal development with decreased maximal absorbance in all patients. Plasmin-induced fibrin degradation revealed different lytic phases of BßY416C and BßW403* than those of the control. Fibrinopeptide cleavage measured by reverse phase high pressure liquid chromatography of BßA68S showed impaired release of fibrinopeptide B. Morphological properties, studied through scanning electron microscopy, differed significantly in the fiber thickness of BßY416C, BßA68S, and BßW403*, and in the fiber density of BßY416C and BßW403*. Finally, homology modeling of BßA68S showed that mutation caused negligible alternations in the protein structure. In conclusion, all mutations altered the correct fibrinogen function or structure that led to congenital fibrinogen disorders.

Diagnosing Czech Patients with Inherited Platelet Disorders.

A single-center study was conducted on 120 patients with inherited disorders of primary hemostasis followed at our hematological center. These patients presented a variety of bleeding symptoms; however, they had no definitive diagnosis. Establishing a diagnosis has consequences for the investigation of probands in families and for treatment management; therefore, we aimed to improve the diagnosis rate in these patients by implementing advanced diagnostic methods. According to the accepted international guidelines at the time of study, we investigated platelet morphology, platelet function assay, light-transmission aggregometry, and flow cytometry. Using only these methods, we were unable to make a definitive diagnosis for most of our patients. However, next-generation sequencing (NGS), which was applied in 31 patients, allowed us to establish definitive diagnoses in six cases (variants in ANKRD26, ITGA2B, and F8) and helped us to identify suspected variants (NBEAL2, F2, BLOC1S6, AP3D1, GP1BB, ANO6, CD36, and ITGB3) and new suspected variants (GFI1B, FGA, GP1BA, and ITGA2B) in 11 patients. The role of NGS in patients with suspicious bleeding symptoms is growing and it changes the diagnostic algorithm. The greatest disadvantage of NGS, aside from the cost, is the occurrence of gene variants of uncertain significance.

Hsp70 Trap Assay for Detection of Misfolded Subproteome Related to Myelodysplastic Syndromes.

The onset and progression of numerous serious diseases (e.g., various types of malignancies, neurodegenerative diseases, and cardiac diseases) are, on a molecular level, associated with protein modifications and misfolding. Current methods for the detection of misfolded proteins are not able to detect the whole misfolded subproteome and, moreover, are rather laborious and time consuming. Herein, we report on a novel simple method for the detection of misfolded proteins employing a surface plasmon resonance (SPR) biosensor and heat shock protein 70 (Hsp70) that recognizes and traps misfolded proteins in a nucleotide-dependent manner. We use this method for the detection of misfolded proteins in blood plasma of patients with various subtypes of myelodysplastic syndromes (MDS) and healthy donors. Our results reveal significantly elevated levels of misfolded proteins in the two stages of MDS that are most affected by oxidative stress: low-risk (RARS) and intermediate-risk (RCMD) patients. This approach can be extended to a variety of diseases and provides unique insights into the thus far unexplored area of blood proteome.

The effect of reagents mimicking oxidative stress on fibrinogen function.

Fibrinogen is one of the plasma proteins most susceptible to oxidative modification. It has been suggested that modification of fibrinogen may cause thrombotic/bleeding complications associated with many pathophysiological states of organism. We exposed fibrinogen molecules to three different modification reagents-malondialdehyde, sodium hypochlorite, and peroxynitrite-that are presented to various degrees in different stages of oxidative stress. We studied the changes in fibrin network formation and platelet interactions with modified fibrinogens under flow conditions. The fastest modification of fibrinogen was caused by hypochlorite. Fibers from fibrinogen modified with either reagent were thinner in comparison with control fibers. We found that platelet dynamic adhesion was significantly lower on fibrinogen modified with malondialdehyde and significantly higher on fibrinogen modified either with hypochlorite or peroxynitrite reflecting different prothrombotic/antithrombotic properties of oxidatively modified fibrinogens. It seems that, in the complex reactions ongoing in living organisms at conditions of oxidation stress, hypochlorite modifies proteins (e.g., fibrinogen) faster and more preferentially than malondialdehyde. It suggests that the prothrombotic effects of prior fibrinogen modifications may outweigh the antithrombotic effect of malondialdehyde-modified fibrinogen in real living systems.

Linking aberrant glycosylation of plasma glycoproteins with progression of myelodysplastic syndromes: a study based on plasmonic biosensor and lectin array.

Aberrant glycosylation of glycoproteins has been linked with various pathologies. Therefore, understanding the relationship between aberrant glycosylation patterns and the onset and progression of the disease is an important research goal that may provide insights into cancer diagnosis and new therapy development. In this study, we use a surface plasmon resonance imaging biosensor and a lectin array to investigate aberrant glycosylation patterns associated with oncohematological disease-myelodysplastic syndromes (MDS). In particular, we detected the interaction between the lectins and glycoproteins present in the blood plasma of patients (three MDS subgroups with different risks of progression to acute myeloid leukemia (AML) and AML patients) and healthy controls. The interaction with lectins from Aleuria aurantia (AAL) and Erythrina cristagalli was more pronounced for plasma samples of the MDS and AML patients, and there was a significant difference between the sensor response to the interaction of AAL with blood plasma from low and medium-risk MDS patients and healthy controls. Our data also suggest that progression from MDS to AML is accompanied by sialylation of glycoproteins and increased levels of truncated O-glycans and that the number of lectins that allow discriminating different stages of disease increases as the disease progresses.

Fibrinogen Sumperk II: dysfibrinogenemia in an individual with two coding mutations.

Fibrinogen­a 340-kDa glycoprotein­plays a crucial role in blood coagulation, platelet aggregation, wound healing, and other physiological processes. A mutation in fibrinogen may lead to congenital dysfibrinogenemia,a rare disease characterized by the functional deficiency of fibrinogen. About 580 cases of abnormal fibrinogens have been reported worldwide; thereof 335 cases in the fibrinogen Aa chain[1]. To our knowledge, only five cases of abnormal fibrinogens with two mutations [2­6] and one case of two different mutations in the same family [7] have been described earlier. A 52-year-old female was examined for bleeding. Routine hemostasis screening resulted in a diagnosis of dysfibrinogenemia. Functional testing revealed prolonged fibrin polymerization, prolonged lysis of the clot, abnormal fibrin morphology,and fibrinopeptides release. Genetic analysis showed two heterozygous nonsense mutations­previously described mutation AaGly13Glu and a novel mutation Aa Ser314Cys. The mutation Aa Gly13-Glu was found in her brother and niece, but there was no evidence in either of the mutation Aa Ser314Cys. While mutation Aa Gly13Glu is responsible for abnormal fibrinopeptide release and prolonged thrombin time, the novel mutation Aa Ser314Cys seems to affect fibrin morphology and fibrinolysis.

Thrombosis-associated hypofibrinogenemia: novel abnormal fibrinogen variant FGG c.8G>A with oxidative posttranslational modifications.

Here, we present the first case of fibrinogen variant FGG c.8G>A. We investigated the behaviour of this mutated fibrinogen in blood coagulation using fibrin polymerization, fibrinolysis, fibrinopeptides release measurement, mass spectrometry (MS), and scanning electron microscopy (SEM). The case was identified by routine coagulation testing of a 34-year-old man diagnosed with thrombosis. Initial genetic analysis revealed a heterozygous mutation in exon 1 of the FGG gene encoding gamma chain signal peptide. Fibrin polymerization by thrombin and reptilase showed the normal formation of the fibrin clot. However, maximal absorbance within polymerization was lower and fibrinolysis had a longer degradation phase than healthy control. SEM revealed a significant difference in clot structure of the patient, and interestingly, MS detected several posttranslational oxidations of fibrinogen. The data suggest that the mutation FGG c.8G>A with the combination of the effect of posttranslational modifications causes a novel case of hypofibrinogenemia associated with thrombosis.

Incorporation of Fibrin, Platelets, and Red Blood Cells into a Coronary Thrombus in Time and Space.

We describe the internal structure, spatial organization and dynamic formation of coronary artery thrombi from ST-segment elevation myocardial infarction patients. Scanning electron microscopy (SEM) revealed significant differences among four groups of patients (<2 hours; 2-6 hours; 6-12 hours, and >12 hours) related to the time of ischemia. Coronary artery thrombi from patients presenting less than 2 hours after the infarction were almost entirely composed of platelets, with small amounts of fibrin and red blood cells. In contrast, thrombi from late presenters (>12 hours) consisted of mainly platelets at the distal end, where clotting was initiated, with almost no platelets at the proximal end, while the red blood cell content went from low at the initiating end to more than 90% at the proximal end. Furthermore, fibrin was present mainly on the outside of the thrombi and older thrombi contained thicker fibers. The red blood cells in late thrombi were compressed to a close-packed, tessellated array of polyhedral structures, called polyhedrocytes. Moreover, there was redistribution from the originally homogeneous composition to fibrin and platelets to the outside, with polyhedrocytes on the interior. The presence of polyhedrocytes and the redistribution of components are signs of in vivo clot contraction (or retraction). These results suggest why later thrombi are resistant to fibrinolytic agents and other treatment modalities, since the close-packed polyhedrocytes form a nearly impermeable seal. Furthermore, it is of particular clinical significance that these findings suggest specific disparate therapies that will be most effective at different stages of thrombus development.

Two novel fibrinogen variants in the C-terminus of the Bß-chain: fibrinogen Rokycany and fibrinogen Znojmo.

Hereditary dysfibrinogenemia is a rare disorder wherein an inherited abnormality in fibrinogen structure may result in defective fibrin function and/or structure. Congenital hypofibrinogenemia is a rare autosomal bleeding disorder, either recessive or dominant, characterized by a low fibrinogen plasma level. A 28-year-old asymptomatic woman (fibrinogen Rokycany) and a 54-year-old man with thrombosis and pulmonary embolism (fibrinogen Znojmo) were investigated for a suspected fibrinogen mutation after abnormal coagulation tests results were obtained. DNA sequencing showed the heterozygous point mutation Bß Asn351Lys in fibrinogen Rokycany and the heterozygous point mutation Bß Arg237Ser in fibrinogen Znojmo, respectively. The kinetics of fibrinopeptide release was found to be normal in both cases. Fibrinolysis was impaired in the Znojmo variant. The average fibril diameters of Znojmo fibrin was slightly increased, but not differing significantly from normal; formed by less fibrils with abrupt fibril terminations. Rheological studies revealed a softer clot. Rokycany fibrin was formed by significantly narrower fibrils than normal fibrin; and the clot was denser than the control clot. Rheological studies revealed a stiffer clot. Impaired fibrinolysis and abnormal clot morphology may be the cause of thrombotic episodes in the patient with Znojmo mutation. New cases of hypofibrinogenemia and dysfibrinogenemia, found by routine coagulation testing, were genetically identified as a novel fibrinogen variants Bß Asn351Lys (fibrinogen Rokycany) and Bß Arg237Ser (fibrinogen Znojmo), respectively.

Nature of frequent deletions in CEBPA.

C/EBPalpha (CCAAT/enhancer binding protein alpha) belongs to the family of leucine zipper transcription factors and is necessary for transcriptional control of granulocyte, adipocyte and hepatocyte differentiation, glucose metabolism and lung development. C/EBPalpha is encoded by an intronless gene. CEBPA mutations cause a myeloid differentiation block and were detected in acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), multiple myeloma and non-Hodgkin's lymphoma (NHL) patients. In this study we identified in 41 individuals from 824 screened individuals (290 AML patients, 382 MDS patients, 56 NHL patients and 96 healthy individuals) a single class of 23 deletions in CEBPA gene which involved a direct repeat of at least 2 bp. These mutations are characterised by the loss of one of two same repeats at the ends of deleted sequence. Three most frequent repeats included in these deletions in CEBPA gene are CGCGAG (493-498_865-870), GCCAAGCAGC (508-517_907-916) and GG (486-487_885-886), all according to GenBank accession no. NM_004364.2. A mechanism for deletion formation between two repetitive sequences can be recombination events in the repair process. Double-stranded cut in DNA can initiate these recombination events of adjacent DNA sequences.

Two cases of congenital dysfibrinogenemia associated with thrombosis - Fibrinogen Praha III and Fibrinogen Plzen.

Congenital dysfibrinogenemia is a rare disease characterised by inherited abnormality in the fibrinogen molecule, resulting in functional defects. Two patients, a 26-year-old woman and a 61-year-old man, both with history of thrombotic events, had abnormal coagulation test results. DNA sequencing showed the heterozygous gamma Y363N mutation (Fibrinogen Praha III) and the heterozygous Aalpha N106D mutation (Fibrinogen Plzen), respectively. Fibrin polymerisation, after addition of either thrombin or reptilase, showed remarkably delayed polymerisation in both cases. Fibrinolysis experiments showed slower tPA initiated lysis of clots. SDS-PAGE did not show any difference between normal and Praha III and Plzen fibrinogens. Both mutations had a significant effect on platelet aggregation. In the presence of either ADP or TRAP, both mutations caused the decrease of platelet aggregation. SEM revealed abnormal clot morphology, with a large number of free ends and narrower fibres of both fibrin Praha III and Plzen. Praha III mutation was situated in the polymerisation pocket "a". The replacement of the bulky aromatic side chain of tyrosine by the polar uncharged small side chain of asparagine may lead to a conformational change, possibly altering the conformation of the polymerisation pocket. The Plzen mutation is situated in the coiled-coil connector and this replacement of polar uncharged asparagine residue by polar acidic aspartate changes the alpha-helical conformation of the coiled-coil connector; and may destabilise hydrogen bonds in its neighborhood. Although both mutations are situated in different regions of the molecule, both mutations have a very similar effect on fibrinogen functions and both are connected with thromboses.

Clinical manifestation and molecular genetic characterization of MYH9 disorders.

Currently, the May-Hegglin anomaly (MHA), Sebastian (SBS), Fechtner (FTNS) and Epstein (EPS) syndrome are considered to be distinct clinical manifestations of a single disease caused by mutations of the MYH9 gene encoding the heavy chain of non-muscle myosin IIA (NMMHC-IIA). Manifestations of these disorders include giant platelets, thrombocytopenia and combinations of the presence of granulocyte inclusions, deafness, cataracts and renal failure. We examined 15 patients from 10 unrelated families on whom we performed immunostaining of NMMHC-IIA in blood samples. Polymerase chain reaction (PCR) analysis of selected exons of the MYH9 gene revealed mutations in nine samples with one novel mutation. Results of fluorescence and mutational analysis were compared with clinical manifestations of the MYH9 disorder. We also determined the number of glycoprotein sites on the surface of platelets. Most patients had an increased number of glycoproteins, which could be due to platelet size.

A New Approach for the Diagnosis of Myelodysplastic Syndrome Subtypes Based on Protein Interaction Analysis.

Myelodysplastic syndromes (MDS) are a heterogeneous group of hematological malignancies with a high risk of transformation to acute myeloid leukemia (AML). MDS are associated with posttranslational modifications of proteins and variations in the protein expression levels. In this work, we present a novel interactomic diagnostic method based on both protein array and surface plasmon resonance biosensor technology, which enables monitoring of protein-protein interactions in a label-free manner. In contrast to conventional methods based on the detection of individual biomarkers, our presented method relies on measuring interactions between arrays of selected proteins and patient plasma. We apply this method to plasma samples obtained from MDS and AML patients, as well as healthy donors, and demonstrate that even a small protein array comprising six selected proteins allows the method to discriminate among different MDS subtypes and healthy donors.

A novel fibrinogen variant--Liberec: dysfibrinogenaemia associated with gamma Tyr262Cys substitution.

OBJECTIVE: A 22-yr-old woman had abnormal preoperative coagulation test results and congenital dysfibrinogenaemia was suspected. PATIENTS AND METHODS: The patient from Liberec (Czech Republic) had a low fibrinogen plasma level as determined by Clauss method, normal fibrinogen level as determined by immunoturbidimetrical method, and prolonged thrombin time. To identify the genetic mutation responsible for this dysfibrinogen, genomic DNA extracted from the blood was analysed. Fibrin polymerisation measurement, kinetics of fibrinopeptide release, fibrinogen clottability measurement and scanning electron microscopy were performed. RESULTS: DNA sequencing showed the heterozygous fibrinogen gamma Y262C mutation. Kinetics of fibrinopeptide release was normal, however fibrin polymerisation was impaired. Fibrinogen clottability measurement showed that only about 45% molecules of fibrinogen are involved in the clot formation. Scanning electron microscopy revealed thicker fibres, which were significantly different from the normal control. CONCLUSION: A case of dysfibrinogenaemia, found by routine coagulation testing, was genetically identified as a novel fibrinogen variant (gamma Y262C) that has been named Liberec.

Acquired dysfibrinogenemia secondary to multiple myeloma.

Abnormal coagulation properties indicative of a dysfibrinogen were found in the plasma of a 72-year-old male with multiple myeloma (IgGkappa, stage IIIA). The patient had high paraprotein concentration (85.75 g/l) and prolonged thrombin time (76.8 s), activated partial thromboplastin time (39.5 s), prothrombin time (23.5 s) and reptilase time (72.0 s). The fibrinogen level was increased. The fibrin polymerization induced by both thrombin and reptilase was impaired. Scanning electron microscopy revealed abnormal clot morphology. After six months of treatment, the paraprotein level decreased (19.48 g/l) and coagulation normalized as well as fibrin polymerization and fibrin clot morphology. It was found that the paraprotein interacts with the gamma-chain of fibrinogen. Acquired dysfibrinogenemia associated with multiple myeloma was diagnosed in the 72-year-old patient.

High-resolution melting analysis for detection of MYH9 mutations.

May-Hegglin anomaly (MHA), Sebastian (SBS), Fechtner (FTNS) and Epstein (EPS) syndromes are rare autosomal dominant disorders with giant platelets and thrombocytopenia. Other manifestations of these disorders are combinations of the presence of granulocyte inclusions and deafness, cataracts and renal failure. Currently, MHA, SBS, FTNS and EPS are considered to be distinct clinical manifestation of a single illness caused by mutations of the MYH9 gene encoding the heavy chain of non-muscle myosin IIA (NMMHC-IIA). As the MYH9 gene has a high number of exons, it takes much time and material to use this method for the detection of MYH9 mutations. Recently, a new method has been introduced for scanning DNA mutations without the need for direct sequencing: high-resolution melting analysis (HRMA). Mutation detection with HRMA relies on the intercalation of the specific dye (LC Green plus) in double-strand DNA and fluorescence monitoring of PCR product melting profiles. In our study, we optimized the conditions and used HRMA for rapid screening of mutations in all MYH9 exons in seven affected individuals from four unrelated families with suspected MYH9 disorders. Samples identified by HRMA as positive for the mutation were analysed by direct sequencing. HRMA saved us over 85% of redundant sequencing.

Fibrinogen Nový Jicín and Praha II: cases of hereditary Aalpha 16 Arg-->Cys and Aalpha 16 Arg-->His dysfibrinogenemia.

INTRODUCTION: Various dysfibrinogenemias have been described worldwide. This paper describes two new cases of dysfibrinogenemia identified in the Czech Republic. MATERIALS AND METHODS: The proposita of fibrinogen Nový Jicín, a 12-year-old girl, presented with hemorrhagic complications, low Clauss fibrinogen level (0.3 g/l) and prolonged both thrombin (70.8 s) and reptilase (>180 s) time. Her mother and sister both presented with normal coagulation tests, normal fibrinogen level and reported no history of bleeding. The carriers of the fibrinogen Praha II were a 31-year-old man and his 11-year-old daughter. They both presented with low fibrinogen Clauss level (0.88 g/l) and prolonged thrombin and reptilase time. To identify the genetic mutation responsible for these dysfibrinogens, genomic DNA extracted from the blood was analyzed. The presence of the mutant chains in the circulation was determined by MALDI-TOF mass spectroscopy. Scanning electron micrographs of the patients' fibrin clots were obtained. RESULTS: The kinetics of fibrinopeptide release and fibrin polymerization were impaired for both fibrinogen Nový Jicín and Praha II. DNA sequencing showed heterogeneous fibrinogen Aalpha R16C mutation in the fibrinogen Nový Jicín case and heterogeneous fibrinogen Aalpha R16H in the fibrinogen Praha II case. The mutant chains were found to be expressed to the circulation by MALDI-TOF mass spectroscopy. Scanning electron micrographs of the patient's fibrin clot were found to be abnormal. CONCLUSIONS: The case of dysfibrinogenemia Aalpha R16C-fibrinogen Nový Jicín and the case of dysfibrinogenemia Aalpha R16H were found by routine coagulation testing and were genetically identified.

Enhanced plasma protein carbonylation in patients with myelodysplastic syndromes.

Myelodysplastic syndromes (MDS) represent a heterogeneous group of pre-leukemic disorders, characterized by ineffective hematopoiesis and the abnormal blood cell development of one or more lineages. Oxidative stress, as an important factor in the carcinogenesis of onco-hematological diseases, is also one of the known factors involved in the pathogenesis of MDS. An increase of reactive oxygen species (ROS) may lead to the oxidation of DNA, lipids, and proteins, thereby causing cell damage. Protein carbonylation caused by ROS is defined as an irreversible post-translational oxidative modification of amino acid side chains, and could play an important role in signaling processes. The detection of protein carbonyl groups is a specific useful marker of oxidative stress. In this study, we examined 32 patients divided into three different subtypes of MDS according to the World Health Organization (WHO) classification criteria as refractory anemia with ringed sideroblasts (RARS), refractory cytopenia with multilineage dysplasia (RCMD), refractory anemia with excess blasts-1,2 (RAEB-1,2). We found significant differences in protein carbonylation between the group of all MDS patients and healthy controls (P=0.0078). Furthermore, carbonylated protein levels were significantly elevated in RARS patients compared to healthy donors (P=0.0013) and to RCMD patients (P=0.0277). We also found a significant difference in the total iron binding capacity (TIBC) between individual subgroups of MDS patients (P=0.0263). Moreover, TIBC was decreased in RARS patients compared to RCMD patients (P=0.0203). TIBC moderately negatively correlated with carbonyl levels (r=-0.5978, P=0.0054) in the MDS patients as a whole. Additionally we observed changes in the carbonylated proteins of RARS patients in comparison with healthy controls and their negative controls. Using tandem mass spectrometry (LC-MS/MS) we identified 27 uniquely carbonylated proteins of RARS patients, which were generated by ROS and could influence the pathophysiology of low-risk MDS. These data indicate that increased protein carbonylation is related with RARS as low-risk MDS subgroup. We suggest that this type of post-translational modification in MDS disease is not "only" a consequence of oxidative stress, but also plays an active role in the pathophysiology and iron metabolism within the RARS subgroup of MDS. Measurement of plasma carbonyl levels and the isolation of carbonylated plasma proteins, followed by their identification, could serve as a potential diagnostic and prognostic tool in MDS.

A novel natural mutation AαPhe98Ile in the fibrinogen coiled-coil affects fibrinogen function.

The aim of this study was to investigate the structure and function of fibrinogen obtained from a patient with normal coagulation times and idiopathic thrombophilia. This was done by SDS-PAGE and DNA sequence analyses, scanning electron microscopy, fibrinopeptide release, fibrin polymerisation initiated by thrombin and reptilase, fibrinolysis, and platelet aggregometry. A novel heterozygous point mutation in the fibrinogen Aα chain, Phe98 to Ile, was found and designated as fibrinogen Vizovice. The mutation, which is located in the RGDF sequence (Aα 95-98) of the fibrinogen coiled-coil region, significantly affected fibrin clot morphology. Namely, the clot formed by fibrinogen Vizovice contained thinner and curled fibrin fibers with reduced length. Lysis of the clots prepared from Vizovice plasma and isolated fibrinogen were found to be impaired. The lysis rate of Vizovice clots was almost four times slower than the lysis rate of control clots. In the presence of platelets agonists the mutant fibrinogen caused increased platelet aggregation. The data obtained show that natural mutation of Phe98 to Ile in the fibrinogen Aα chain influences lateral aggregation of fibrin protofibrils, fibrinolysis, and platelet aggregation. They also suggest that delayed fibrinolysis, together with the abnormal fibrin network morphology and increased platelet aggregation, may be the direct cause of thrombotic complications in the patient associated with pregnancy loss.