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SummaryWe have identified 1,135 haemophilia A patients with missense mutations associated with mild (46%), moderate (22%), severe (16%), and mixed haemophilia phenotypes (11%). Altogether, we detected 374 different missense mutations of which 195 are not listed in the HAMSTeRS database. While missense mutations are strongly underrepresented within the factor VIII (FVIII) B-domain, they are evenly distributed throughout the entire F8 cDNA sequence. Only 36 (5%) of 720 patients with missense mutations and known inhibitor status showed an association with inhibitor formation. Inhibitor prevalence was four-fold higher for severe haemophilia compared to mild/moderate phenotypes. Mutations associated with inhibitor formation were especially clustered within the C1/C2 domain compared to the other domains (8.7% C1/C2 domain vs. 3.6% non-C1/C2-domain; p-value: 0.01). Three different missense mutations (T314A [T295A], S2010P [S1991P], R2169H [R2150H]) were associated twice with inhibitor formation. Importantly, we found that the risk of inhibitor formation in association with FVIII missense mutations is significant higher if the amino acid substitution belongs to another physicochemical class than the original residue (p-value 0.039). For this purpose distinct classes of substitutions were grouped in association with side chains properties: class I, small/hydrophobic; class II, neutral; class III, acidic; class IV, basic. Thus, although missense mutations were associated with an overall lower risk of inhibitor formation compared to other F8 gene mutation types, different missense mutations correlate with specific risks for inhibitor formation. These differences have to be identified in assigning risk profiles to aid in choice of preventative treatments designed to prevent inhibitor formation.

Zusammenfassung Die Hämophilie A und B werden durch unterschiedliche Mutationen im Faktor VIII (FVIII)- bzw. Faktor IX (FIX)-Gen verursacht. Entsprechend der Schwere des molekularen Defekts gibt es klinisch unterschiedlich schwere Verlaufsformen der Erkrankung. Hämophiliepatienten können heutzutage ausgezeichnet mit aus Plasma oder rekombinant hergestellten Gerinnungspräparaten behandelt werden. Hierdurch können Blutungen und deren Folgen weitgehend verhindert werden, mit einer inzwischen fast normalisierten Lebensqualität und Lebenserwartung. Eine schwere Komplikation ist die Antikörper (Hemmkörper)-Bildung gegen den zugeführten Gerinnungsfaktor. Das Risiko einer solchen Hemmkörperbildung ist bei Vorliegen von Mutationen ohne endogene Faktor-VIII-Protein-Bildung besonders hoch und liegt bei 25–50%. Die Information über den zu erwartenden klinischen Verlauf ist heute die wichtigste Indikation für die FVIII-/FIX-Genanalyse und wird regelhaft bei den schwer betroffenen Hämophiliepatienten durchgeführt. Die Kenntnis des FVIII-/FIX-Gendefekts ermöglicht des Weiteren eine sichere und schnelle Überträgerinnendiagnose bei weiblichen Familienangehörigen von Hämophilen.

Recently, it was shown that glycoproteins with N-glycans close to the NH(2) terminus can directly enter the calnexin/calreticulin cycle and bypass BiP binding. This should allow efficient secretion of glycoproteins such as factor VIII (FVIII) whose secretion is negatively affected by BiP interaction. Examination of the glycosylation pattern of the NH(2) terminus of FV and FVIII revealed N-glycans at positions 23 and 27 in FV and at position 41 in FVIII. To improve FVIII secretion, a 14-amino-acid-long polypeptide with (G3) or without (G0; control) three N-linked glycosylation consensus sites was inserted upstream of the NH(2) terminus of a B-domain deleted FVIII protein. Expression of G3- and G0-constructs in three different cell lines resulted in the same or even higher expression rate of protein as found for the B-domain deleted FVIII. However, as demonstrated by Western blot analysis, the G3- as well as the G0-protein variants were mainly retained inside the cells in similar amounts. Thus, glycosylation alone does not automatically lead to higher secretion rates, but must be in context to the normal structure of the FVIII protein.

Abnormal patterns of DNA methylation are observed in many diseases such as tumors and imprinting disorders. Little is known about inter-individual and gender specific variations. Here, we report on accurate and sensitive quantitative measurements of methylation in DNA from total blood in 96 healthy human males and 96 healthy human females. Global methylation was estimated by studying two repetitive DNA elements, namely Line-1 and Alu repeats, while single loci were investigated for three differentially methylated regions (DMRs) at PEG3, NESP55 and H19 imprinted genes and two additional loci at Xq28 (F8 gene) and at 19q13.4 (locus between PEG3 and ubiquitin specific protease 29). We observed inter-individual correlations in the degree of methylation between Alu and Line-1 repeats. Moreover, all studied CpGs showed slightly higher methylation in males (P < 0.0003-0.0381), with the exception of DMRs at imprinted genes (P = 0.0342-0.9616) which were almost equally methylated in both sexes with only a small tendency towards higher methylation in males. This observed difference could be due to the process of X chromosome inactivation or merely to the presence of an additional X chromosome in female cells or could be a result of downstream effects of sex determination.

Hemophilia A and B are inherited coagulopathies caused by mutations in the factor VIII (FVIII) and factor IX (FIX) gene, respectively. Although today, both diseases are well or excellently be treatable by intravenous substitution of FVIII and FIX concentrates, considerable efforts are being made to develop gene therapy protocols for hemophilia aimed to improving patients’ quality of life and to reducing the costs of substitution therapy. Gene therapy aims to correct gene defects and is based principally on the introduction of the intact FVIII or FIX gene into somatic cells. This procedure requires viral transfer vectors. So far, sufficient and even high gene therapeutically expressed concentrations of FVIII/FIX could only be achieved in animal studies, while clinical protocols for humans had to be preliminarily stopped due to inefficacy and side effects. Nevertheless, based on the success of the animal studies, it can be expected that similarly high expression rates can also be achieved in humans. With view to the fact that in the present situation patients are at high risk of developing thrombotic events, this study presents a doxycycline inducible expression system for human FIX integrated within an adenoviral gene transfer vector. After intravenous injection of modified adenoviral vectors in mice, the efficacy of the regulation was demonstrated by measuring the FIX antigen concentration as well as FIX activity in mouse blood. Additionally, by measuring the Ddimer concentration in mouse blood and correlating these values with the gene therapeutically expressed human FIX concentration, we could demonstrate, for the first time, that high expression levels of human FIX in a gene therapy protocol increased the blood procoagulant activity in animals.

The use of restricted replication-competent adenoviruses (RRCAs) inducing tumor cell-specific lysis is a promising approach in cancer gene therapy. However, the use of RRCAs in humans carries considerable risk, since after injection into the patient, further regulation or inhibition of virus replication from the outside is impossible. Therefore, we have developed a novel system allowing external pharmacological control of RRCA replication. We show here that a tumor-selective E1B-deleted RRCA can be tightly regulated by use of doxycycline (dox)-controlled adenoviral E1A gene expression, which in turn determines vector replication. RRCA replication is switched on by addition and switched off by withdrawal of dox. The system results in efficient tumor cell killing after induction by dox, whereas cells are unaffected by the uninduced system. It was also employed for efficient external control of transgene expression from cotransfected replication-deficient adenovectors. Furthermore, the use of a liver cell-specific human alpha1-antitrypsin (hAAT)-promoter driving a tetracycline-controlled transcriptional silencer allowed specific protection of cells with hAAT-promoter activity in the absence of dox in vitro and in vivo, delineating a new principle of 'tissue protective' gene therapy. The concept of external control of RRCAs may help to improve the safety of cancer gene therapy.

ZusammenfassungDie Hämophiliekommission der GTH betreibt ein zentrales Register für alle deutschen Zentren, die Patienten mit Blutungsneigungen behandeln. Das Ziel war ein System, mit dem epidemiologische Daten bzgl. Gerinnungsstörungen effektiver gesammelt und ausgewertet werden können. Das Register bildet außerdem die datentechnische Grundlage im Rahmen des Deutschen Human-Genom-Projekts. Erklärtes Ziel ist dabei die vollständige molekulare Charakterisierung der genetischen Mutationen des X-Chromosoms von Patienten mit Hämophilie A in Deutschland und die anschließende Korrelation mit dem Phänotyp. Ein elektronisches Netzwerk wird für die Kommunikation benutzt. Eine Java-Applikation wurde entwickelt, wodurch die Online-Datenerfassung durch die teilnehmenden Zentren möglich wurde. Alternativ wurde die Möglichkeit zur Offline-Datenerfassung mit Versendung von verschlüsselten Datenträgern geschaffen. Der Datenschutz ist durch personenbezogenen Zugangsschutz, Anonymisierung der Patientendaten und Kodierung der Daten mit einem Verschlüsselungsverfahren gewährleistet. Die Bestätigung der Datenschutzbehörden über die Unbedenklichkeit des Projekts liegt vor. Insgesamt wird durch das Hämophileregister eine Verbesserung der epidemiologischen Wissensbasis als Grundlage für zukünftige therapeutische Entscheidungen bzgl. Grund- und Begleiterkrankungen erwartet. Das Register kann außerdem weiteren Forschungsprojekten als Basis dienen.

SummaryFollowing substitution therapy with human factor IX (hFIX) concentrate, therapy of haemophilia B by viral gene transfer has become an attractive alternative therapy in recent years. However, high doses of expressed hFIX, which can already be achieved in animal studies, may cause thrombosis in humans (van Hylckama Vlieg et al., 2000). Thus, it should be possible to maintain transgene expression within the therapeutic range. Therefore, we inserted elements of the tetracycline (Tet)-dependent Tet-On gene regulatory system into replication deficient adenovectors. The new system consists of two adenovec-tors: a response vector expressing hFIX (Ad5. TRE.hFIX), and a regulator vector expressing a second generation reverse tetracycline transactivator controlled by a CMV- (Ad5. CMV.rtTA) or human alpha1-antitrypsin-promoter (Ad5.hAAT.rtTA). Expression studies in four human cell lines showed high expression of hFIX from Ad5. TRE.hFIX in all cell lines in combination with Ad5. CMV.rtTA regulator vector, but only high specific expression in HepG2-cells in combination with Ad5.hAAT.rtTA regulator vector. Additionally, up- and down-regulation of hFIX expression could be demonstrated in vitro with the Ad5. TRE.hFIX/Ad5. CMV.rtTA combination and modulating doxycycline concentrations. When SCID-mice were infected with the Ad5. TRE.hFIX/Ad5. CMV.rtTA combination, up- and down-regulation of hFIX expression was achieved by oral doses of doxycycline for a period of at least two months. Replacement of the Ad5. CMV.rtTA vector by the Ad5.hAAT.rtTA vector showed minimal expression of hFIX in vivo. Although hFIX expression showed a slow and gradual decrease over time in vivo with the Ad5. CMV.rtTA vector, it remained within the therapeutic range. To date, regulation of hFIX has not been described in this way.

ZusammenfassungIn Deutschland leben rund 6000 Hämophilie-A-Patienten. Mit Screening-Methoden können ca. 97% der Mutationen erfasst werden. Für die restlichen Patienten werden alle kodierenden Regionen des FVIII-Gens sequenziert.Von 1350 Patienten wurde bei 80 Patienten zunächst keine Mutation gefunden. In fünf Fällen war eine Inversion im Intron 1 verantwortlich, in 16 Patienten wurden bekannte und bei 19 Patienten neue Mutationen identifiziert. Von den neuen Mutationen lagen 14 in kodierenden Bereichen, die restlichen fünf befanden sich in flankierenden Bereichen von Exons. Neben den als kausal betrachteten Mutationen wurden fünf Polymorphismen identifiziert. Weitere Untersuchungen müssen klären, ob diese Polymorphismen Krankheitsbild und -verlauf beeinflussen.Überraschenderweise wurde bei 23 der 80 Patienten keine kausale Mutation in den untersuchten Regionen identifiziert. Das bedeutet, dass in etwa 2% der Hämophilie-A-Patienten keine Mutation in der cDNA des FVIII-Gens gefunden werden kann. Daher müssen auch Mutationen in nicht kodierenden Regionen oder sogar in anderen Genen in Betracht gezogen werden. Eines dieser Gene kodiert für den von-Willebrand-Faktor (vWF). Wir identifizieren in zwei Fällen eine Mutation im vWF-Gen.

ZusammenfassungEtwa 30% der Patienten die an schwerer Hämophilie A leiden, entwickeln als Komplikation einer Substitutionstherapie gegen Faktor VIII gerichtete Antikörper, die die prokoagulatorische Aktivität von intravenös injizierten FVIII-Proteinen neutralisieren. In der Regel werden verschiedene Epitope auf dem FVIII-Molekül durch diese Antikörper gebunden. Die detaillierte Struktur dieser Epitope ist unbekannt. In dieser Studie werden Epitope auf dem Faktor-VIII-Molekül mit Hilfe festphasengebundener Peptid-Arrays identifiziert, auf denen die Aminosäuresequenz des FVIII in Oligopeptiden dargestellt wird. Die Bindung von FVIII-Antikörpern an bestimmte Peptidsequenzen zeigt potenzielle Epitopstrukturen. FVIII-Antikörper von Inhibitorpatienten und gesunden Blutspendern werden zurzeit mit dieser Methode charakterisiert. Identifizierte Epitope können zur Entwicklung neuer Therapiekonzepte führen, die dazu dienen, eine Hemmkörperentwicklung zu vermeiden bzw. bereits entstandene Hemmkörper besser zu eliminieren. Als Teilprojekt des Konsortiums »Hämophilie A« wird im Rahmen des Gesamtvorhabens »Genotyp-Phänotyp-Korrelation bei der Hämophilie A« untersucht, ob die Epitopcharakteristik mit dem Typ und der Position der FVIII-Genmutationen korreliert sowie Zusammenhänge zwischen Epitop und klinischem Verlauf der Krankheit bestehen. Zusätzlich wird der Einfluss der Epitope auf den therapeutischem Effekt und Erfolg der Immuntoleranzinduktion untersucht.

ZusammenfassungDie Hämophilie A wird durch einen genetischen Defekt des FVIII-Gens verursacht und führt entweder zum vollständigen Fehlen oder zu einem erheblichen Funktionsverlust des Gerinnungsfaktors VIII im Blut. Die erhöhte Blutungsneigung der betroffenen Patienten kann durch die intravenöse Gabe von Faktor-VIII-Protein verhindert werden. Allerdings entwickeln 25% der Patienten, die an einer schweren Hämophilie A leiden, Anti-Faktor-VIII-Antikörper gegen das substitutierte Konzentrat. In dieser Studie wird versucht, die phänotypischen Parameter (z.B. detaillierte Dokumentation des Krankheitsverlaufs, Basislaborwerte) und therapieassoziierten Daten (z.B. verwendetes Konzentrat, Konzentratverbrauch, Anzahl der Substitutionen, Faktor-VIII-Recovery sowie Inhibitorentwicklung und -eliminierung) von etwa 800 Patienten zu erfassen. Durch diese Erfassung kann der Effekt der unterschiedlichen Therapiemaßnahmen auf den Krankheitsverlauf bewertet werden. Einen besonderen Einfluss auf den Krankheitsverlauf und die Therapie hat der Faktor-VIII-Gendefekt, der ursächlich für die Hämophilie verantwortlich ist. Wir erwarten, dass bestimmte Mutationen bzw. Mutationstypen spezifischen Phänotypen und in etwa vergleichbaren therapeutischen Verläufen zugeordnet werden können.

ZusammenfassungDie Hämophilie ist die häufigste genetisch bedingte Form einer schweren Blutungsneigung. Ursächlich für die Erkrankung sind Defekte im Faktor-VIII-Gen, die zu verminderter Faktor-VIII-Aktivität mit einer vom Ausmaß der Störung abhängigen Blutungsneigung führen. Die ursächlichen Gendefekte können inzwischen routinemäßig identifiziert werden. Trotz der Vielfalt der Mutationen lassen sich mehrere Hotspots feststellen, z.B. Inversion im Intron 22, kleine Deletionen/Insertionen an Poly-A und Punktmutationen an CpG-Dinukleotiden. Bereiche geringer Mutationshäufigkeit sind z.B. im mittleren Abschnitt des Exons 14, der für die funktionell wenig bedeutende B-Domäne kodiert und praktisch keine Missense-Mutationen enthält. Die Mutationsdiagnostik verbesserte die Diagnostik und das Verständnis der Pathogenese der Hämophilie-A-Erkrankung. Nach Identifizierung des Gendefekts in einer Familie ist eine schnelle und sichere Konduktorinnendiagnostik möglich. Die Korrelation zwischen Gendefekt und klinischem Verlauf zeigte, dass die Art der Mutation einen wichtigen genetischen Prädispositionsfaktor für die zurzeit schwerste therapeutische Komplikation bei Hämophilie, die Hemmkörperbildung, darstellt. Ein relativ leichter Verlauf bei eigentlich schwerer Hämophilie A lässt sich mit speziellen Mutationen oder gleichzeitig vorliegenden thrombophiliefördernden Mutationen erklären. Molekulare Modelle des Faktor-VIII-Moleküls erlauben gezielt Auswirkungen von Mutationen zu untersuchen und so neue Struktur/ Funktionsbeziehungen zu erkennen. Dies könnte die Entwicklung zukünftiger rekombinanter Gerinnungspräparate mit veränderten Eigenschaften (z.B. höherer Wirkungsgrad, verlängerte Halbwertszeit, geringere Immunogenität) anstoßen.

Summary. The severe clotting defects associated with the diagnosis of severe haemophilia A and B require a quality management and quality assurance system designed to avoid both bleeding sequelae (such as damaged joints) through early on-demand or prophylactic treatment in a home-care setting, and side-effects such as infectious diseases (hepatitis A–G and human immunodeficiency virus), allergic reactions, haemolysis and if possible inhibitor formation, by using highly purified, virus-inactivated or recombinant products in which the factor VIII and IX proteins are as natural as possible. As the intravenous injection of the required clotting factor is entrusted to the patients in home treatment, the haemophilia centre has to check treatment protocols and, when necessary, joint and muscle status. In addition, it is imperative to ensure the safety of the product, and checks must be carried out to make sure that batch numbers are recalled as soon as possible if side-effects are observed. These are the reasons for several Acts of Parliament in Germany requiring special treatments and regular checks (the Disabled Act, recommendations by the German Medical Council, the Transfusion Act). Thus, at the haemophilia centre in Bonn we have established a special quality management and quality assurance system taking into account the great number of patients (> 800), the often considerable distance between the centre and the patient, and the aforementioned regulations and laws. Quality management involves dealing with daily practicalities such as 24-h availability of a physician, medical technologist and nurse, careful instruction of patient and family in home care, genetic counselling, regular laboratory tests (especially recovery time, half-life, inhibitors and gene defects, clinical chemistry and serology) and clinical investigations (especially joint and muscle status). It also includes co-operation with family doctors and different departments at our university hospital (e.g. orthopaedic, microbiology), daily conferences with staff, information for nursery schools, schools, training institutions and/or the workplace in case of emergency, and cooperation with German haemophilia foundations. For quality assurance, several self-controlling systems are in place, such as distribution of concentrate, laboratory data, treatment protocols, joint and muscle status and bleeding tendencies. All these and more are double-checked and interactive, controlling data and activities with the help of EDP. Exceptional staff motivation and patient compliance are important for this quality system.

Alloantibodies (inhibitors) against factor VIII (FVIII) develop in 20-30% of patients with severe haemophilia A and render classical FVIII substitution therapy ineffective. Several studies have shown that genetic factors, the type of FVIII gene mutation and immune response genes (e.g. the Major Histocompatibility Complexes), influence the risk of inhibitor formation. In particular, the type of FVIII gene mutation has proven to be a decisive risk factor. Patients with severe molecular gene defects (e.g. large deletions, nonsense mutations, intron-22 inversion) and no endogenous FVIII synthesis have a 7-10 times higher inhibitor prevalence than patients with milder molecular gene defects (e.g. missense mutations, small deletions, splice site mutations). To date, at least 10 distinct classes of mutations have been shown which have differing risks of associated inhibitor formation. A challenging observation in inhibitor patients is the heterogeneity of the antibody epitopes with respect to their number and their specificity. At least five epitopes in the FVIII molecule have been identified that constitute the targets for antibodies in most inhibitor patients. These epitopes are located in the ar3 region and the A2, A3, C1, C2 domains which correspond to the functional binding sites of the ligands of the FVIII protein. At present, the determinants of the characteristics of these epitopes and the subsequent inhibitor titre are unknown. A relationship of the mutation site and the epitope localization has been shown for some individual patients with mild haemophilia A. However, in severely affected haemophilia A patients, the influence of patient genetics on inhibitor titre and epitope specificity has yet to be elucidated.

Haemophilia represents the most common hereditary severe bleeding disorder in humans. About 100 families with this condition live in Lithuania, one of the Baltic states with a population of 3.7 million. Haemophilia care and genetic counselling are still rendered difficult owing to limited availability of clotting factor concentrate and molecular genetic diagnosis. In the present study, a haemophilia registry, comprising phenotypic and genotypic data of the majority of Lithuanian haemophilia A and B patients, was established. The phenotype includes the degree of severity, factor VIII:C, factor VIII:Ag, factor IX:C, von Willebrand factor and antigen (VWF:RiCoF, vWF:Ag) and inhibitor status. Genotyping of the factor VIII and IX genes was performed using mutation screening methods and direct sequencing. In 61 out of 63 patients with haemophilia A (96.8%) and all eight patients with haemophilia B (100%), the causative mutations could be detected. Nineteen of the factor VIII gene defects and two of the factor IX gene mutations are reported for the first time. Identified mutations allowed direct carrier diagnosis in 83 female relatives revealing 44 carriers, 38 non-carriers and one somatic mosaicism. The information provided by this registry will be helpful for monitoring the treatment of Lithuanian haemophilia patients and also for reliable genetic counselling of the affected families in the future.

Hemophilia A and B are X-linked bleeding disorders caused by mutations within the factor VIII and factor IX genes, respectively. Although both disorders can be easily treated by substitution with concentrates of functional factor VIII and factor IX, considerable effort has been undertaken to develop a gene therapy for hemophilia in order to improve patients' life quality and reduce high costs of therapy. The principle of gene therapy is the introduction of an intact copy of the factor VIII/factor IX gene in somatic cells, compensating for the defective gene. To do this, retroviral, adenoviral, and adeno-associated virus (AAV) vector systems, among others, were used. Encouraged by the results of preliminary experiments using preponderant mouse and canine models, three clinical phase I studies on hemophilia A and B patients have been initiated, one of which has been preliminarily reported successful.

A complex network of hemostasis proteins maintains the blood flow and integrity of the vascular system. Molecular biology techniques have led to identification and cloning of the corresponding genes, thereby providing the basis for development of various recombinant clotting factor concentrates. Further analysis of these genes allowed for phenotype and genotype correlations in patients with hemorrhagic or thromboembolic disorders and analysis of structure and function relationships of the involved proteins. All these efforts result in a greatly advanced understanding of the hemostatic network. The aim of this article is to illustrate this progress by reporting on the recent results in representative hereditary hemorrhagic and such thromboembolic conditions as hemophilia, von Willebrand disease, and thrombotic disorders.

The mechanisms responsible for the low factor VIII (fVIII) activity in the plasma of patients with mild/moderate hemophilia A are poorly understood. In such patients, we have identified a series of fVIII mutations (Ile2098Ser, Ser2119Tyr, Asn2129Ser, Arg2150His, and Pro2153Gln) clustered in the C1 domain and associated with reduced binding of fVIII to von Willebrand factor (vWf). For each patient plasma, the specific activity of mutated fVIII was close to that of normal fVIII. Scatchard analysis showed that the affinity for vWf of recombinant Ile2098Ser, Ser2119Tyr, and Arg2150His fVIII mutants was reduced 8-fold, 80-fold, and 3-fold, respectively, when compared with normal fVIII. Given the importance of vWf for the stability of fVIII in plasma, these findings suggested that the reduction of fVIII binding to vWf resulting from the above-mentioned mutations could contribute to patients' low fVIII plasma levels. We, therefore, analyzed the effect of vWf on fVIII production by Chinese hamster ovary (CHO) cells transfected with expression vectors for recombinant B domain-deleted normal, Ile2098Ser, Ser2119Tyr, and Arg2150His fVIII. These 3 mutations impaired the vWf-dependent accumulation of functional fVIII in culture medium. Analysis of fVIII production by transiently transfected CHO cells indicated that, in addition to the impaired stabilization by vWf, the secretion of functional Ile2098Ser and Arg2150His fVIII was reduced about 2-fold and 6-fold, respectively, by comparison to Ser2119Tyr and normal fVIII. These findings indicate that C1-domain mutations resulting in reduced fVIII binding to vWf are an important cause of mild/moderate hemophilia A. ispartof: Blood vol:96 issue:3 pages:958-65 ispartof: location:United States status: published

Factor VIII gene analysis in a large consanguinous Danish family comprising 24 affected males and four homozygously affected females revealed an Asn694Ile mutation within the A2 domain. The factor VIII gene mutation led to a mild haemophilia A phenotype with factor VIII function displaying discordance between one-stage clotting and chromogenic two-stage assays. In one-stage assays, values ranged from 0·05 to 0·30 IU/ml (males) and from 0·19 to 0·29 IU/ml (homozygous affected females), whereas the chromogenic two-stage assay produced values of around only 50% of the one-stage result [0·02–0·12 IU/ml (males); 0·06–0·10 IU/ml (females)]. The differences are suggested to be caused by the effect of the mutation on the active cleaved form of the factor (F)VIII protein. As the original amino acid (Asn) is conserved in all known FVIII A2 sequences, but not in ceruloplasmin, we suggest that Asn694 is involved in an A2-specific functional role. Examination of a homology model of the A domains predicts that the Asn694Ile mutation (i) results in the loss of two potential hydrogen–bonding interactions and (ii) hampers the integration of the bulky side-chain of Ile into the A2 domain core, probably causing an altered stability and/or folding of the protein. Interestingly, the disease in this Danish family was originally proposed to be von Willebrand–Jurgens disease. However, the current study rules out the co-existence of either von Willebrand's disease or the presence of the Normandy variant of von Willebrand factor (type 2N).

The treatment of inhibitors is one of the most challenging fields in haemophilia care. The present study reports the results of 60 haemophilia A inhibitor patients treated according to the 'Bonn Protocol' and evaluates predictors for the duration and outcome of therapy. Successful immune tolerance could be achieved in 52 patients (86.7%) while the therapy failed in eight patients (13.3%). The immune tolerance achieved was longlasting in all 52 patients, with no inhibitor relapse in up to 20-years follow-up. The course of ITT was influenced by several factors. Interruptions of treatment during the ITT course led to a substantial prolongation of ITT duration (median 39.9 months vs 14.1 months in continuously treated patients). Infections of intravenous central lines appeared to be frequently coincided with ITT prolongation and sometimes even ITT failure. Further negative predictors towards the ITT duration were high inhibitor titres at enrollment or during ITT. There was also a tendency towards longer ITT duration in patients exhibiting the prevalent intron 22 inversion. As a consequence of our data treatment interruptions and infections of intravenous central lines should be avoided during the course of ITT. Furthermore our data suggest, that ITT should be started at low inhibitor titres preferably with a high factor VIII dosage protocol.

ZusammenfassungDie Hämophilie ist die häufigste genetisch bedingte Form einer schweren Blutungsneigung. Ursächlich für die Erkrankung sind Defekte im Faktor-Vlll-Gen bei den betroffenen Patienten, welche zu einer Verminderung der Faktor-Vlll- Aktivität, mit einer vom Ausmaß der Störung abhängigen Blutungsneigung führen. Nachdem zunächst die Größe des Faktor-Vlll-Gens die Mutationssuche bei den Patienten sehr erschwert hatte, können seit kurzem die für die Erkrankung ursächlichen Gendefekte routinemäßig identifiziert werden. Dies hat zu entscheidenden Verbesserungen in der Diagnostik und dem Verständnis der Pathogenese der Hämophilie-A-Erkrankung geführt. So ist nach Identifizierung des Gendefektes in einer betroffenen Familie für alle Ratsuchenden eine schnelle und sichere Konduktorinnendiagnostik möglich. Die Korrelation des Gendefektes mit dem klinischen Verlauf der Patienten hat gezeigt, daß die Art der Mutation einen wichtigen genetischen Prädispositionsfaktor für die heutzutage schwerste Komplikation der Hämophilie-Behandlung, die Hemmkörperbildung, darstellt. Ein kürzlich entwickeltes molekulares Modell des Faktor-Vlll- Proteins erlaubt die gezielte Untersuchung der Auswirkungen einer Mutation auf das Faktor-VlII-Molekül und hat neue Erkenntnisse über die Wechselwirkungen von Faktor VIII mit anderen Faktoren der Gerinnungskaskade hervorgebracht.

The conversion of androgens to estrogens by CYP19 (cytochrome P450AROM, aromatase) is an important step in the mechanism of androgen action in the brain. CYP19 expression has been demonstrated in various animal species, but studies in human postnatal brain tissue are lacking. Therefore, we investigated CYP19 mRNA expression in human temporal lobe tissues. We studied biopsy materials removed at neurosurgery from 34 women, 32 men and 10 children with temporal lobe epilepsy. Quantification of CYP19 mRNA was achieved by nested competitive reverse transcription-PCR. CYP19 mRNA concentrations did not differ significantly between women (2.6 +/- 0.6 arbitrary units, aU; mean +/- SEM) and men (1.6 +/- 0.3 aU) nor between cerebral cortex tissue (2.0 +/- 0.4 aU) and subcortical white matter tissue of adults (2.4 +/- 0.7 aU), but they were significantly lower in cerebral cortex specimens of children (0.9 +/- 0.6 aU) than in those of adults (p0.02). In conclusion, CYP19 mRNA is expressed in the temporal lobe of children and adults. CYP19 mRNA concentrations are significantly lower in specimens of children than in those of adults.

The eighth edition of the haemophilia B database (http://www.umds.ac. uk/molgen/haemBdatabase.htm ) lists in an easily accessible form all known factor IX mutations due to small changes (base substitutions and short additions and/or deletions of

Screening of the factor VIII (FVIII) gene which spans 186 kb and codes for 26 exons, was originally hampered by its size but is now feasible because rapid DNA scanning methodologies have been developed. The present study for the first time directly compares the three most widely applied screening methods, denaturing gradient gel electrophoresis (DGGE), single-stranded conformational polymorphism (SSCP) and chemical mismatch cleavage (CMC) for their sensitivity of mutation detection in a selected group of ten haemophilia A patients. Nine of these patients are known to be cross-reacting material positive and eight exhibited a mild to moderate phenotype. Of the ten patients screened, we identified mutations in nine by all three screening methods. Of the mutations characterised, two are previously unpublished. T to C (S373P) and G to A (D525N). In one mildly affected haemophiliac, we identified a second T to C sequence change in the 5' untranslated region at -601 bp, probably having no effect on FVIII gene expression. Modelling studies were performed on those mutations lying within the A domains of FVIII (D525N, R527W, I566T) to study the possible effect of these mutations on structure and/or function. When the three methods are performing optimally and have been standardised, our experience is that CMC and DGGE are equally efficient at sequence variation detection while SSCP is slightly less sensitive.

SummaryMolecular genetic studies have shown that development of antibodies to factor VIII (inhibitors) occurs most frequently in patients with severe haemophilia due to major gene lesions including inversions, stop codons and large deletions. Previous studies of HLA type were performed on inhibitor and non-inhibitor patients with diverse uncharacterised mutations which may have confounded detection of significant associations. We therefore selected a group of patients with a single mutation type, the prevalent intron 22 inversion, with or without inhibitors, to determine HLA genotype. Seventy-one such patients, 42 without and 29 with inhibitors (13 high, 9 low and 7 transient responders) were genotyped for MHC Class I HLA-A, -B, -C and Class II HLA-DQA, -DQB and -DRB loci. No strong correlation of any HLA-allele to inhibitor or non-inhibitor status was found. However, alleles of the haplotype HLA-A3, HLA-B7, HLA-C7, HLA-DQA0102, HLA-DQB0602, HLA-DR15 occurred more often in inhibitor patients. Since the alleles of this extended haplotype are common in the North European population only a very strong association would achieve statistical significance. Further studies of groups of patients similar to those studied here will be needed to confirm or exclude this association.

Although many examples of unrelated hemophilia A patients carrying identical point mutations in the factor VIII (FVIII) gene have been reported, the clinical phenotype is not always the same among patients sharing the same molecular defect. Possible explanations for this discrepancy include undetected additional mutations in the FVIII gene or coinheritance of mutations at other genetic loci that modulate FVIII function. We report molecular genetic analysis of potential modifying genes in two sets of unrelated patients carrying common FVIII missense mutations but exhibiting different levels of clinical severity. Both mutations (FVIII R1689C and R2209Q) are associated with severe hemophilia A in some patients and mild/moderate disease in others. The common von Willebrand disease type 2N mutation (R91Q) was excluded as a modifying factor in these groups of patients. However, analysis of the recently described factor V (FV) R506Q mutation (leading to activated protein C resistance) identified a correlation of inheritance of this defect with reduced hemophilia A severity. Two moderately affected hemophilia A patients, each with either of two FVIII gene mutations, were heterozygous for FV R506Q, whereas two severely affected patients and two moderately affected patients were homozygous normal at the FV locus. Our results suggest that coinheritance of the FV R506Q mutation may be an important determinant of clinical phenotype in hemophilia A and that modification of the protein C pathway may offer a new strategy for the treatment of FVIII deficiency.

The sixth edition of the haemophilia B database lists in easily accessible form all known factor IX mutations due to small changes (base substitutions and short additions and/or deletions of

SummaryA screening program for the detection of patients with von Willebrand disease type 2N (VWD 2N) was carried out in 177 unrelated patients previously diagnosed with haemophilia A and in 199 unrelated patients with VWD type 1 in comparison. By measuring the factor VIII (FVIII) binding capacity of von Willebrand factor (VWF), we detected 13 patients with VWD 2N within 8 unrelated families. The former diagnosis has been haemophilia A in 5 index patients, and VWD in the remaining 3. Included in this study were 14 patients with suspected haemophilia A, whose molecular analysis for mutations in the FVIII gene was unsuccessful. Five of them had VWD 2N. In all patients with the VWD 2N phenotype we were able to identify specific molecular defects in the corresponding DNA sequence of the FVIII binding domain of VWF. The most common defect was R91Q. Four patients from 4 families were homozygous for R91Q, six patients from 3 families were compound heterozygous for R91Q and a silent yet unidentified allele. The VWD 2N phenotype of father, daughter, and son in one family, was based on 2 different genotypes, compound heterozygosity for R91Q and VWD type 1 in the father and the daughter, and homozygosity for R91Q in the son. Two patients from one family were compound heterozygous for T28M and ΔC2680-2685 in exon 18, and one patient was compound heterozygous for a novel candidate missense mutation in exon 18 (E24K) and ΔC2680-2685 in exon 18 which is regarded the most common defect causing severe VWD type 3. FVIII:C values of 0.07 and 0.14 IU/ml were observed in patients with the genotype T28MIΔC2680-2685 whereas in patients being homozygous or compound heterozygous for R91Q, FVIII:C was 0.19 ° 0.071 IU/ml. In contrast to the other genotypes, E24KIΔC2680-2685 is correlated with a more severe haemophilic phenotype with a FVIII residual activity of only 0.01-0.02 IU/ml. This emphasizes the need for inclusion of the factor VIII binding assay in the diagnostic workup of suspected haemophilia A.

Summary. To Screen for mutations within the factor VIII gene of 101 patients (85 unrelated), we used denaturing gradient gel electrophoresis (DGGE) after DNA amplification of target regions, including all coding regions except for the middle part (amino acid 757 to amino acid 1649) of the B domain. With this method, missense mutations were identified in 86% of unrelated patients. 41 different mutations were identified; 25 of them have not been described previously. Five of the genotypes are associated with CRM+ and 26 with CRMred status. Patients who are definitely related to each other showed no differences in DNA sequence. One patient showed two different base pair alterations, the first at amino acid 469 [ala(GCAgly(GGA)] and the second at position 473 [tyr(TAT)cys(TGT)]. One patient with an amino acid change at position 1689 [arg(CGC)his(CAC)] has developed an inhibitor against factor VIII.

SummaryThe formation of factor VIII antibodies is a major problem for replacement therapy of haemophilia A patients. Antibodies occur in 5-30% of patients with severe haemophilia A. The reason for antibody formation is still unknown. In this study we correlate for the first time different factor VIII gene mutations, stop- and missense mutations, large and small deletions and intrachromosomal intron 22 recombinations to antibody formation. A total of 364 patients with known inhibitor status of our institute, of the database, and of 3 studies representing intron-22-inversion data are included. The results show that the risk for developing factor VIII antibodies is strongly related to stop mutations, large deletions and intrachromosomal recombinations. A probable explanation could be the complete lack of endogenous circulating factor VIII protein in these cases. Other factors that might be important for the pathogenesis of inhibitor formation, e. g. the antenatal period, as well as possible therapeutic effects, are discussed.

LINE-1 repeats account for ~17% of the human genome. Little is known about their individual methylation patterns, because their repetitive, almost identical sequences make them difficult to be individually targeted. Here, we used bisulfite conversion to study methylation at individual LINE-1 repeats. The loci studied included 39 X-linked loci and 5 autosomal loci. On the X chromosome in women, we found statistically significant less methylation at almost all L1Hs compared with men. Methylation at L1P and L1M did not correlate with the inactivation status of the host DNA, while the majority of L1Hs that were possible to be studied lie in inactivated regions. To investigate whether the male-female differences at L1Hs on the X are linked to the inactivation process itself rather than to a mere influence of gender, we analyzed six of the L1Hs loci on the X chromosome in Turners and Klinefelters which have female and male phenotype, respectively, but with reversed number of X chromosomes. We could confirm that all samples with two X chromosomes are hypomethylated at the L1Hs loci. Therefore, the inactive X is hypomethylated at L1Hs; the latter could play an exclusive role in the X chromosome inactivation process. At autosomal L1Hs, methylation levels showed a correlation tendency between methylation level and genome size, with higher methylation observed at most loci in individuals with one X chromosome and the lowest in XXY individuals. In summary, loci-specific LINE-1 methylation levels show considerable plasticity and depend on genomic position and constitution.

ZusammenfassungInnerhalb dieser Übersicht sollen Direktsequenzierung, Voruntersuchungsmethoden und spezifische Mutationstests für die molekulargenetische Diagnostik von hereditären Gerinnungsstörungen vorgestellt und deren unterschiedliche Einsatzmöglichkeiten diskutiert werden. Wenn eine familienspezifische Mutation gefunden ist, kann allen Angehörigen eine direkte Überträgerdiagnostik angeboten werden. Da in vielen betroffenen Familien die für die Erkrankung ursächliche Mutation nicht bekannt ist, werden die Prinzipien der indirekten Überträgerdiagnostik ebenfalls vorgestellt.

Ziel: In dieser Arbeit geben wir einen Überblick über den Stand der Hämophilie-A-Forschung mit den Schwerpunkten Molekularbiologie und Überträgerdiagnostik. Ursächlich für die X-chromosomal, rezessiv vererbte Hämophilie A ist ein fehlendes oder zumindest defektes Faktor-VIII-Protein. Quellen: Die Grundlagen für diese Übersicht bilden vorwiegend Originalarbeiten, aber auch Übersichtsartikel zu einzelnen Teilgebieten sowie eigene Untersuchungs-ergebnisse. Auswahlkriterien: Es werden die Faktor-VIII-Synthese, die posttranslationale Modifikation und der bisherige Wissensstand über die funktionellen Faktor-VIII-Protein-domänen anhand von identifizierten Mutationen und Proteinstudien beschrieben. Weiter wird die Bedeutung der gefundenen Mutationen für die Uberträgerdiagnose bei den betroffenen Hämophilie-A-Familien dargestellt. Ergebnisse: Bisher sind nur wenige funktionelle Bereiche des Faktors VIII auf-geklärt worden. Mit neuen, jetzt verfügbar gewordenen Mutationssuchmethoden kann die Mutation im Faktor-VIII-Gen derzeit bei 60% aller Hämophilie-A-Patien-ten gefunden werden. Diese Form der direkten Uberträgerdiagnose verbessert die schon vorhandenen Möglichkeiten der Überträgerbestimmung mittels Polymorphismen- und Labordaten erheblich. Schluβfolgerung: Die neu identifizierten Mutationen werden es ermöglichen, einen weiteren Beitrag zur Klärung der Wirkungsweise des Faktor-VIII-Proteins zu leisten. Trotz dieses Fortschritts muβ weiter daran gearbeitet werden, jede Mutation zu entdecken, da jede zusätzlich erkannte Mutation die Uberträgerdiagnose verbessert.

In humans, considerable variation in methylation at single loci and repetitive elements in various cells and tissues is observed. Recently, several inter- and intra-tissue correlations for DNA methylation have been reported. To investigate the extent and reproducibility of such correlations, we investigated inter- and intra-tissue methylation correlations among seven different loci in 9 different tissues in a population of 100 healthy seven-week-old CD1 outbred mice. We used a highly quantitative approach to measure methylation levels to high accuracy at two single loci in the alpha-actin and myosine light chain promoters, at three differentially methylated regions of the Peg3, Snrpn and Lit1 genes associated with imprinted loci, and at two repetitive elements in the Line-1 and IAP-LTR genes in the various tissues. In this population of mice, methylation at several loci was sex-associated and intra-tissue correlations among the studied loci were observed for brain and spleen. Inter-tissue correlations were rarely observed. To investigate method-dependent experimental variability, we re-analyzed the same spleen and tongue samples using SIRPH and pyrosequencing methods and reconfirmed intra-tissue correlations for spleen and sex-associated correlations for DNA methylation for tongue. When we repeated DNA methylation measurements for a second mouse population raised under similar conditions three months later, we did not detect sex-associated or intra-tissues correlations. Additional studies that examine large numbers of loci may be required to further understand the factors that influence stability of DNA methylation.

Transmission of infectious diseases via the use of plasma concentrates has lent special significance to the manufacture of recombinant coagulation factor concentrates. At present, two factor VIII concentrates manufactured by recombinant DNA technology, produced by Baxter (Recombinate) and Bayer/Miles (Kogenate), are undergoing clinical trials. At the haemophilia centres in Bonn and Frankfurt am Main a total of 4.1 million IU have been used by twelve patients for prophylaxis and treatment for bleeding between 1989 and 1990. The clinical efficacy, particularly in the treatment of bleeding episodes was good and corresponded with that of plasma-derived concentrates. There were no allergic reactions, development of inhibitors or other serious side effects. In laboratory investigations no adverse results were encountered.

Previously, we reported on inter-individual and gender specific variations of LINE-1 methylation in healthy individuals. In this study, we investigated whether this variability could be influenced by age or sex hormones in humans. To this end, we studied LINE-1 methylation in vivo in blood-derived DNA from individuals aged 18 to 64 years and from young healthy females at various hormone levels during the menstrual cycle. Our results show that no significant association with age was observed. However, the previously reported increase of LINE-1 methylation in males was reconfirmed. In females, although no correlation between LINE-1 or Alu methylation and hormone levels was observed, a significant stable individual specific level of methylation was noted. In vitro results largely confirmed these findings, as neither estrogen nor dihydrotestosterone affected LINE-1 or Alu methylation in Hek293T, HUVEC, or MDA-kb2 cell lines. In contrast, a decrease in methylation was observed in estrogen-treated T47-Kbluc cell lines strongly expressing estrogen receptor. The very low expression of estrogen receptor in blood cells could explain the observed insensitivity of methylation at LINE-1 to natural hormonal variations in females. In conclusion, neither natural cycle of hormones nor age has a detectable effect on the LINE-1 methylation in peripheral blood cells, while gender remains an important factor.

Background: Approximately 25% of severe hemophilia A (HA) patients develop antibodies to factor VIII protein. Patients: In the present case-controlled cohort study, 260 severely affected, mutation-type-matched HA patients were studied for association of human leukocyte antigen (HLA) class II molecules and polymorphisms in the genes encoding interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-alpha) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) and development of inhibitors. Results: Our results demonstrate a higher frequency of DRB1*15 and DQB1*0602 alleles as well as of the haplotype DRB1*15/DQB1*0602 in inhibitor patients [odds ratio (OR) 1.9; P A polymorphism was found with higher frequency in the inhibitor cohort (0.22 vs. 0.13, OR 1.80). This finding was more pronounced for the homozygous A/A genotype (OR 4.7). For IL-10, the -1082G allele was observed more frequently in patients with inhibitors (0.55 vs. 0.43; P = 0.008). The functional cytokine phenotype was determined for the first time, on the basis of the genetic background, and this showed that 12% of patients with inhibitors were high-TNF-alpha/high-IL-10 producers, as compared with 3% of non-inhibitor patients (OR 4.4). A trend for a lower frequency of the A allele of the CT60 polymorphism in CTLA-4 was found in inhibitor patients (0.42 vs. 0.50). Conclusions: In conclusion, the reported data clearly highlighted the participation of HLA molecules in inhibitor formation in a large cohort of patients. The higher frequencies of the -308G > A polymorphism in TNF-alpha and -1082A > G in IL-10 in inhibitor patients confirmed the earlier published data. The CT60 single-nucleotide polymorphism in CTLA-4 is of apparently less importance.

The murine monoclonal antibodies ESH2, ESH4, ESH5, and ESH8 specifically bind and inhibit the procoagulant activity of human coagulation factor VIII (FVIII). They are frequently used as a model of inhibitors which are raised against injected FVIII in about 25% of hemophiliacs as a serious side effect of substitution therapy. However, binding kinetics of the interaction of these antibodies with FVIII and their influence on FVIII activity (inhibition) have not yet been examined systematically. For this, we examined association and dissociation of protein:antibody interaction using surface plasmon resonance (SPR) and determined their ability to inhibit the FVIII activity in a one-stage and a two-stage assay. SPR-analysis revealed that the equilibrium dissociation constants (K(D)) of ESH8 and ESH4 are low and in a similar range (ESH8: K(D(ESH8)) = 0.542 nM; ESH4: K(D(ESH4)) = 0.761 nM). A 5.7 times higher K(D) than for ESH4 was observed for ESH2 (4.33 nM), whereas ESH5 showed the highest K(D) of 28.8 nM. In accordance with the lowest K(D), ESH8, and ESH4 reduced FVIII activity of normal human plasma almost completely in a one-stage clot inhibition assay (ESH8: 91.9%; ESH4: 90.1%). However, ESH8 inhibited FVIII activity more efficiently as only 1.0 microg/ml ESH8 was sufficient to obtain maximum inhibition compared to up to 600 microg/ml of ESH4. Despite its attenuated K(D), ESH2 inhibits FVIII:C still efficiently, reducing 61.3% of FVIII activity at a concentration of 9 microg/ml in the one-stage clotting assay. However, a discrepancy of inhibitory efficiency was found depending on the method used to measure FVIII activity. These effects seem to be mainly caused by differences of activation time of FVIII during both FVIII activity assays. The systematic assessment of these results should support FVIII interaction studies, and can provide data to rationally test peptides/mimotopes to remove or neutralize inhibitors of FVIII activity.

SummaryThe G1691A (Leiden) mutation of the factor V gene is the most prevalent identified cause of venous thrombosis. Therefore, we developed a new genetic test using the TaqMan system. With this assay which combines PCR amplification and detection reaction in one closed tube, a cohort of 234 patients with a history of thrombosis was screened. In parallel, amplification products of the same patients were screened with a previously described test using endonuclease digestion of PCR products followed by gel electrophoresis. Identical results were obtained by both methods. Among cases, 122 (52%) individuals were homozygous normal, 99 (42%) were heterozygous affected and 13 (5.5%) showed homozygous pattern for the Factor V Leiden mutation. Thus, it could be demonstrated that the new TaqMan assay is a robust, rapid and automated method for high throughput application which avoids time consuming and difficult post-PCR steps.

The B-cell epitope of the monoclonal anti-factor VIII antibody ESH8 characterized by peptide array analysis

Elevated levels of human factor IX (hFIX) in subjects with an objectively con- firmed first episode of deep vein thrombosis (DVT) increase the risk of DVT by a factor of 2 to 3 [3]. A useful marker of increased procoagulant activity, which has already been shown to be associated with DVT and VT as well as other clinical conditions, is the D-dimer [1]

The seventh edition of the haemophilia B database lists in easily accessible form all known factor IX mutations due to small changes (base substitutions and short additions and/or deletions of

Hemophilia A (HA) is caused by partial or total deficiency of F8 protein activity. In a small group, about 1.8% of patients with HA, no mutation is found in the F8 gene. Among this group, we report here on one patient with severe HA in whom no mRNA of the F8 gene was detected. Using 2 common polymorphisms in F8 exon 14, we were able to show that the same allele shared by the patient, his mother, and his sister was not detected by reverse transcription-polymerase chain reaction (RT-PCR) from total blood mRNA. Skewed X-chromosome inactivation in both the mother and the sister was excluded by studying the methylation profile of the androgen receptor gene (HUMARA locus). These findings strongly suggest that the cause of HA in this patient is either absence or rapid degradation of the F8 mRNA, which points to a novel mechanism leading to HA.

Haemophilia is caused by hundreds of different mutations and manifests itself in clinical conditions of varying severity. Despite being inherited in monogenic form, the clinical features of haemophilia can be influenced by other genetic factors, thereby confounding the boundary between monogenic and multifactorial disease. Unlike sufferers of other genetic diseases, haemophiliacs can be treated successfully by intravenous substitution of coagulation factors. Haemophilia is also the most attractive model for developing gene-therapy protocols, as the normal life expectancy of haemophiliacs allows the side effects of gene therapy, as well as its efficiency, to be monitored over long periods.

Summary. Background: haemophilia A (HA) is characterized by partial or total deficiency of factor VIII (FVIII) protein activity. It is caused by a broad spectrum of mutations in the FVIII gene. Despite tremendous improvements in mutation screening methods, in about 2% of HA patients no DNA change could be found, even after sequencing the whole coding part of the FVIII gene including the flanking splice sites, as well as the promotor and the 3′ UTR regions. Objectives, patients and methods: In the present study we performed a detailed RNA analysis of three groups of patients. The first included control patients with known splicing defects, the second included two patients with already identified nucleotide changes close to splicing sites, that could potentially alter the normal splicing process, and a third group of 11 unrelated patients whose genomic DNA have already been screened for mutations by DHPLC and direct sequencing with no mutation being identified. Results: Both candidate splice site mutations were shown to result in either skipping or alternative splicing of at least one exon, therefore these DNA changes must be considered as causal for the patients' HA phenotype. In contrast, no abnormalities on the RNA level were observed in any of 11 unrelated patients without mutations in the FVIII gene. Conclusions: These findings exclude mutations that could be located deep in the introns and affecting either normal splicing or lead to mechanisms causing some unknown rearrangements of the FVIII gene. In fact, our results point to the presence of still unknown factor(s) causing HA, which might be either allelic or in the close proximity of the FVIII gene or non-allelic associated with other genetic loci that are involved in the processing of the FVIII protein.

SummaryVon Willebrand disease type Normandy (VWD 2N) is caused by mutations at the factor VIII (FVIII) binding site of VWF, located at the amino-terminus of mature VWF. It is inherited in a recessive fashion and both homozygous and compound heterozygous mutations have been identified. Homozygous mutations are correlated with a clinical phenotype indistinguishable from mild hemophilia A by conventional laboratory tests, whereas compound heterozygosity with a quantitative defect may appear as VWD type 1 (VWD1). We have now identified and expressed a novel heterozygous mutation (Y795C) which is responsible for both, a defective FVIII-binding and aberrant multimers in a female patient with mild FVIII deficiency. Additionally we expressed another mutation (E787K), previously identified by us in a male patient with a severe ‘pseudohemophilic’ phenotype. Analysis of the FVIII binding and the multimer structure of the respective recombinant VWF mutants reproduced the observed phenotype: the FVIII binding defect in addition to the aberrant multimer structure of the patient with Y795C and the FVIII binding defect only, in the patient with E787K. Our results demonstrate the causative nature of the two mutations and emphasize the impact of ‘cysteine mutations’ on the multimer structure of VWF.