title: A novel congenital dysprothrombinemia leading to defective prothrombin maturation.
abstract: BACKGROUND
  Prothrombin deficiency is a very rare disorder caused by mutations in the F2 gene that generate hypoprothrombinemia or dysprothrombinemia and is characterized by bleeding manifestations that can vary from clinically irrelevant to life-threatening.
  
  
  OBJECTIVE
  Here we characterize a patient with a novel missense mutation in F2, c.1090T/A (p.Val322Glu), that causes severe dysprothrombinemia.
  
  
  METHODS
  Coagulation assays, prothrombin Western Blotting, FII activation by Ecarin, fibrinogen degradation products quantification and thrombin generation assay were carried out to assess prothrombin expression and function. PCR followed by direct sequencing was carried out to characterize the mutation. In silico analysis for missense variant and molecular modeling were applied to predict the mechanism that leads to dysprothrombinemia.
  
  
  CONCLUSIONS
  The homozygous patient had a markedly prolonged prothrombin time, strongly reduced FII activity (0.82%) but normal antigen levels. In the thrombin generation assay the lag time and the peak height were unmeasurable, suggesting that the Val322Glu mutation results in the inability of the mutant prothrombin to be fully activated to thrombin. In fact, prothrombin activation by ecarin was defective, with a massive accumulation of the meizothrombin intermediate. Molecular modeling and dynamic simulation studies showed that the Val322Glu mutation interferes with protein flexibility at Arg271 and Arg320. This impairs the switch of the protein from zymogen to proteinase, thus preventing the formation of thrombin. Accumulated meizothrombin, however, maintains some fibrinogen-degrading activity, as shown by the formation of FDPs, and this probably explains the patient's mild bleeding phenotype.
authors.affiliation: Medical Genetics, Department of Clinical and Experimental Medicine, University of Foggia, Foggia, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Bafunno
authors.affiliation: Department of Medicine, Section of Internal and Cardiovascular Medicine, University of Perugia, Perugia, Italy.
authors.forename: Loredana
authors.initials: L
authors.lastname: Bury
authors.affiliation: Atherosclerosis and Thrombosis Unit, Research Department, Istituto di Ricovero e Cura a Carattere Scientifico, Casa Sollievo della Sofferenza, S. Giovanni Rotondo, Foggia, Italy.
authors.forename: Giovanni Luca
authors.initials: GL
authors.lastname: Tiscia
authors.affiliation: Department of Medicine, Section of Internal and Cardiovascular Medicine, University of Perugia, Perugia, Italy.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Fierro
authors.affiliation: Atherosclerosis and Thrombosis Unit, Research Department, Istituto di Ricovero e Cura a Carattere Scientifico, Casa Sollievo della Sofferenza, S. Giovanni Rotondo, Foggia, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Favuzzi
authors.affiliation: Institute of Crystallography, Consiglio Nazionale delle Ricerche, Bari, Italy.
authors.forename: Rocco
authors.initials: R
authors.lastname: Caliandro
authors.affiliation: Medical Genetics, Department of Clinical and Experimental Medicine, University of Foggia, Foggia, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Sessa
authors.affiliation: Atherosclerosis and Thrombosis Unit, Research Department, Istituto di Ricovero e Cura a Carattere Scientifico, Casa Sollievo della Sofferenza, S. Giovanni Rotondo, Foggia, Italy.
authors.forename: Elvira
authors.initials: E
authors.lastname: Grandone
authors.affiliation: Medical Genetics, Department of Clinical and Experimental Medicine, University of Foggia, Foggia, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Margaglione
authors.affiliation: Department of Medicine, Section of Internal and Cardiovascular Medicine, University of Perugia, Perugia, Italy. Electronic address: paolo.gresele@unipg.it.
authors.forename: Paolo
authors.initials: P
authors.lastname: Gresele
mesh_terms: D001777:Blood Coagulation; D025861:Blood Coagulation Disorders, Inherited / Q000097:blood / Q000235:genetics* / Q000378:metabolism; D004792:Enzyme Precursors / Q000378:metabolism; D005260:Female; D006720:Homozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D056004:Molecular Dynamics Simulation; D020125:Mutation, Missense; D010375:Pedigree; D011516:Prothrombin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D013917:Thrombin / Q000378:metabolism; D013925:Thromboplastin
chemical_list: D004792:Enzyme Precursors; D011516:Prothrombin; D013925:Thromboplastin; D013917:Thrombin; C026812:meizothrombin
keywords: Dysprothrombinemia; Factor II; Meizothrombin; Molecular modeling; Prothrombin activation