title: Implication of novel CYP2C9*57 (p.Asn204His) variant in coumarin hypersensitivity.
abstract: BACKGROUND
  Polymorphisms in CYP2C9 can vary the rate of metabolic clearance of oral anticoagulants, risking toxicity in patients. The present study focused on exploring the genetic etiology of idiopathic hyper sensitivity to coumarin anticoagulants in a patient who presented with multiple bleeding episodes and supra-elevated International Normalized Ratios.
  
  
  METHODS
  Bidirectional gene sequencing of CYP2C9 and VKORC1 was carried out. Using allele-specific polymerase chain reaction, the identified novel variant was genotyped in 309 patients on anticoagulation therapy. The pharmacoproteomic significance of the novel genetic variant was elucidated by structural demonstration of binding of coumarin molecules within the mutant CYP2C9 204His protein model and in silico bioinformatic evolutionary analyses. Three-dimensional structure model of the mutant protein was constructed on the basis of the published X-ray crystal structure of human CYP2C9 protein (Protein Data Bank, 1R9O).
  
  
  RESULTS
  The patient was identified to have a novel heterozygous missense mutation in exon 4 of CYP2C9 gene (g.9172A > C; p.Asn204His; CYP2C9*57). The variant was absent in the 309 genotyped patients. In silico bioinformatic analyses indicated the variant to have a deleterious effect on the protein. Analysis of 3D structure model of the mutant protein revealed that the substituted His204 led to restricted binding of the coumarin drug within the binding site of CYP2C9 enzyme, thereby inhibiting its metabolic clearance and thus explaining the enhanced pharmacologic effect and bleeding in the patient.
  
  
  CONCLUSIONS
  The study elucidates the structurally deleterious role of the novel CYP2C9*57 missense mutation in coumarin toxicity.
authors.affiliation: Center of Medical Genetics, Sir Ganga Ram Hospital, New Delhi, India. rishanahar@gmail.com
authors.forename: Risha
authors.initials: R
authors.lastname: Nahar
authors.forename: Divya
authors.initials: D
authors.lastname: Dube
authors.forename: Rajiv
authors.initials: R
authors.lastname: Parakh
authors.forename: Roumi
authors.initials: R
authors.lastname: Deb
authors.forename: Renu
authors.initials: R
authors.lastname: Saxena
authors.forename: Tej P
authors.initials: TP
authors.lastname: Singh
authors.forename: Ishwar C
authors.initials: IC
authors.lastname: Verma
mesh_terms: D000074:Acenocoumarol / Q000378:metabolism; D000925:Anticoagulants / Q000009:adverse effects* / Q000378:metabolism; D001189:Aryl Hydrocarbon Hydroxylases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D003374:Coumarins / Q000009:adverse effects* / Q000378:metabolism; D065729:Cytochrome P-450 CYP2C9; D005260:Female; D005480:Flurbiprofen / Q000378:metabolism; D005838:Genotype; D006470:Hemorrhage / Q000139:chemically induced*; D006801:Humans; D019934:International Normalized Ratio; D008875:Middle Aged; D062105:Molecular Docking Simulation; D020125:Mutation, Missense; D011485:Protein Binding; D014859:Warfarin / Q000378:metabolism
chemical_list: D000925:Anticoagulants; D003374:Coumarins; D005480:Flurbiprofen; D014859:Warfarin; C030123:coumarin; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; D000074:Acenocoumarol