Der Forschungsschwerpunkt unserer Arbeitsgruppe liegt bei den Enzymen des Vitamin K Zyklus (VKORC1 und GGCX) und den Vitamin K abhängigen Proteinen. Neben diesen bildet die Untersuchung heriditärer Störungen des Gerinnungssystems, insbesondere Defekte im Faktor VIII und IX (Hämophilie A und B), im Faktor XIII sowie im VWF die Grundlage weiterer wichtiger Projekte.
Unsere Forschungsaktivitäten werden durch Förderung seitens des BMBF (Nationales Genom Forschungs-Netzwerk- Cardiovaskuläre Erkrankungen), der DFG, der Universitätsklinik Bonn (BONFOR Programm) und der Industrie unterstützt.
Key research objects of our group are enzymes of the vitamin K cycle: VKORC1, VKORC1L1 und ã-glutamyl carboxylase (GGCX). Vitamin K hydroquinone, produced by VKORC1, is an essential cofactor for posttranslational modification of vitamin K dependent proteins. Only by this modification, these proteins are able to bind to Ca2+ and fulfill their specific function. As vitamin K content of normal nutrition is minimal and no storage exist in the body, vitamin K epoxide must be recycled to ensure sufficient ã-carboxylation of all vitamin K dependent proteins. This recycling mechanisms is performed Vitamin K Epoxid Oxido-Reduktase (VKORC1), which we were able to clone in 2004. In the following, we identified rare homozygous / compound heterozygous missense mutations in VKORC1 or GGCX as cause for hereditary combinde deficiency of vitamin K dependent coagulation factors (VKCFD 1 and VKCFD2) and heterozygous missense mutations as cause for pronounced coumarin resistence. Furthermore, we identified the warfarin binding site of VKORC1 at the boundary layer between ER membrane and ER lumen. Recently, we could proof that the mutation p.Arg98Trp in the VKORC1 gene associated with VKCFD2 affects a di-arginine motiv (amino acids 97 - 100, Leu-Arg-Thr-Arg), essential for correct ER membrane localisation.
Another focus of our work is the homolog VKORC1L1. In contrast to VKORC1, this enzyme is incapable of activating of vitamin K dependent proteins. However, we could show that VKORC1L1 inhibits lipid peroxidation and increases cell viability by continous vitamin K-hydroquinon production in the context of cellular antioxidation.
Dr. Matthias Watzka
-Dr. Katrin Czogalla-Nitsche (BONFOR Nachwuchsgruppe)
PhD Student Suvoshree Ghosh,
PhD Student Francesco Forin,
MTA Katrin Kraus,
MTA Heike Höfer
Prof. Schweitzer, Institute for Biochemistry und Molecular Biologie, University Bonn
Prof. Hornung, Institute of Molecular Medicine, University Bonn
Stand: 22. Oktober 2014
Phenotype-Genotype Correlation in blood coagulation disorders
In the department of molecular haemostaseology 25 genes involved in blood coagulation are routinely investigated. The scientific interests of the group are focused on genotype-phenotype correlation in patients with rare blood coagulation disorders. Haemophilia, a deficiency of coagulation factor VIII and IX is of special interest. Different genetic defects have been identified and functionally studied. New insights in the genetic alteration as deep intronic changes leading to haemophilia are thoroughly explored. An interesting issue addressed in our group is the association F8 missense mutations and their impact on the FVIII activity, especially in the context of discrepancy between one stage clotting and chromogenic assays. Inhibitor development, is of special interest and different genetic factors as mutation type, polymorphisms in the immune-response genes and HLA are currently investigated. Another scientific area focuses on factor 5 gene. New mutations, leading to APC resistance have been identified and structurally and functionally studied.
The group is involved in a number of national and international studies including ABIRISK, analyzing the mechanisms and consequences of immunization against biopharmaceutical products and OBSITI aiming to evaluate patient and therapy related variables on immune tolerance induction course.
Priv.-Doz. Dr. Anna Pavlova, MD, PhD
Dr. Behnaz Pezeshkpoor, PhD
Dr. Thilo Albert, PhD
Selection of publications:
1. Goodeve AC, Pavlova A, Oldenburg J. Genomics of bleeding disorders. Haemophilia. 2014 May;20 Suppl 4:50-3.
2. Pavlova A, Delev D, Pezeshkpoor B, Müller J, Oldenburg J. Haemophilia A mutations in patients with non-severe phenotype associated with a discrepancy between one-stage and chromogenic factor VIII activity assays. Thromb Haemost.2014 May 5;111(5):851-61.
3. Pahl S, Pavlova A, Driesen J, Oldenburg J. Effect of F8 B domain gene variants on synthesis, secretion, activity and stability of factor VIII protein. Thromb Haemost. 2014 Jan;111(1):58-66.
4. Pezeshkpoor B, Pavlova A, Oldenburg J, El-Maarri O. F8 genetic analysis strategies when standard approaches fail. Hamostaseologie. 2014;34(2):167-73.
5. Pavlova A, Oldenburg J. Defining severity of hemophilia: more than factor levels. Semin Thromb Hemost. 2013 Oct;39(7):702-10. doi: 10.1055/s-0033-1354426. Epub 2013 Sep 11. Review.
6. Pavlova A. F8 gene and phenotype: single player in a team? Blood. 2013 May,9;121(19):3784-5.
7. Pahl S, Pavlova A, Driesen J, Müller J, Pötzsch B, Oldenburg J. In vitro characterization of recombinant factor VIII concentrates reveals significant differences in protein content, activity and thrombin activation profile.Haemophilia. 2013 May;19(3):392-8.
8. Schwaab R, Pavlova A, Albert T, Caspers M, Oldenburg J. Significance of F8 missense mutations with respect to inhibitor formation. Thromb Haemost. 2013 Mar;109(3):464-70. doi: 10.1160/TH12-07-0521. Epub 2013 Jan 10. PubMed PMID: 23306409
9. Caspers M, Pavlova A, Driesen J, Harbrecht U, Klamroth R, Kadar J, Fischer R,Kemkes-Matthes B, Oldenburg J. Deficiencies of antithrombin, protein C andprotein S - practical experience in genetic analysis of a large patient cohort.Thromb Haemost. 2012 Aug;108(2):247-57.
10. Luxembourg B, Delev D, Geisen C, Spannagl M, Krause M, Miesbach W, Heller C, Bergmann F, Schmeink U, Grossmann R, Lindhoff-Last E, Seifried E, Oldenburg J,Pavlova A. Molecular basis of antithrombin deficiency. Thromb Haemost. 2011Apr;105(4):635-46.
11. Pavlova A, Delev D, Lacroix-Desmazes S, Schwaab R, Mende M, Fimmers R, Astermark J, Oldenburg J. Impact of polymorphisms of the major histocompatibility complex class II, interleukin-10, tumor necrosis factor-alpha and cytotoxic T-lymphocyte antigen-4 genes on inhibitor development in severe hemophilia A. J Thromb Haemost. 2009 Dec;7(12):2006-2015. doi: 10.1111/j.1538-7836.2009.03636.x. PubMed PMID: 19817985.
Stand: 02. Dezember 2014
Plasma Factor XIII is a protransglutaminase circulating as a heterotetramer composed of two catalytic A and two protective B subunits. It functions by crosslinking preformed fibrin clots and also by crosslinking fibrinolytic inhibitors like alpha 2-antiplasmin to the fibrin clot making the clot mechanically and chemically stronger and resistant to premature fibrinolysis. Deficiency of this protein can result in a bleeding predisposition commonly known as Factor XIII deficiency. Factor XIII deficiency can be inherited or acquired. The inherited form is of two types: A) a rare severe form (1 in 1 to 4 million prevalence and B) a more frequent mild heterozygous form. The inherited form of this deficiency is characterized by mutations occurring in the F13A1 and F13B genes; the genes for the A and B subunits respectively.
The Factor XIII group works on two aspects: A) The genotypic and phenotypic diagnosis of patients suffering from severe and mild Factor XIII deficiency and B) The structure-functional aspects of Factor XIII. The Factor XIII group has in the past characterized and reported a large number of Factor XIII deficiency patients with mutations in F13A and F13B genes. The efforts of the Factor XIII group in the last few years have brought the otherwise lesser known mild Factor XIII deficiency into focus. This group also is one of the few groups in the world that is involved in determining the molecular etiology of heterozygous mutations reported from mild Factor XIII deficiency patients. Current efforts include expressing these mutations in heterologous systems and evaluating the in vitro expression phenotype in a multitude of assays each phenotypically representing a unique aspect of Factor XIII. Current efforts are also directed towards solving the Factor XIII A2B2 heterotetramer structure and eventually characterizing it in terms of complex dynamics.
Dr. (biol.) Arijit Biswas, Scientist
Priv.-Doz. Dr. (med.) Vytautas Ivaskevicius, Clinician
Ms. Sneha Gupta, Ph.D student
Recent publications from this group are:
Stand: 02. Dezember 2014
Genotype-phenotype correlation in von Willebrand disease
Von Willebrand disease (VWD) project is focused on understanding of the molecular basis of different types of VWD to establish phenotype-genotype correlations.
In VWD project, we explore genotype and phenotype characteristics of a cohort of patients with VWD with the aim of dissecting the distribution of mutations in different types of VWD and correlate them to the clinical disease severity. In addition, our project intends to elucidate the pathophysiological mechanisms of detected novel missense and potential splice mutations by in vitro gene expression studies in mammalian cell lines and in vivo transcript analysis respectively. Moreover, possible structural impact of the mutations on VWF protein is studied by in silico homology modeling. Additionally, we plan to study behavior of the recombinant wilde-type and mutant VWF strings in vitro under shear-stress conditions resembling the blood flow in vessels using an automated shear-controlling device.
Dr. Hamideh Yadegari, PhD
Stand: 02. Dezember 2014