title: Assessment of the  F9  genotype-specific FIX inhibitor risks and characterisation of 10 novel severe  F9  defects in the first molecular series of Argentinian patients with haemophilia B.
abstract: In haemophilia B (HB) (factor IX [FIX] deficiency),  F9  genotype largely determines clinical phenotype. Aimed to characterise Argentinian families with HB, this study presents  F9  genotype frequencies and their specific FIX inhibitor risk and 10 novel  F9  mutations. Ninety-one DNA samples from HB patients and relatives were subjected to a new scheme: a primary screen for large deletions, a secondary screen for point mutations using conformation sensitive gel electrophoresis, DNA-sequencing and bioinformatic analysis. Our unbiased HB population (N=52) (77% with severe, 11.5% moderate and 11.5% mild HB) showed 32 missense (61.5%), including three novel mutations predicting specific structural/functional defects  in silico , seven nonsense (13.5%) (one novel), five large deletions, four splice including three novel mutations affecting predicted splicing scores, three indels (two novel) and one Leiden mutation. Our comprehensive HB population included five patients with long-lasting FIX inhibitors: three nonsense (p.E35* (novel), p.R75*, p.W240*) and two entire- F9  deletions. Another patient with an indel (p.A26Rfs*14) developed transient inhibitors. A case-control analysis, based on our global prevalence of 3.05% for developing inhibitors in HB revealed that missense mutations were associated with a low risk odds ratio (OR) of 0.05 and a prevalence of 0.39%, whereas nonsense and entire- F9  deletions had significantly higher risks (OR 11.0 and 32.7) and prevalence (14.3% and 44.5%, respectively). Our cost-effective practical approach enabled identification of the causative mutation in all 55 Argentine families with HB, analysis of the molecular pathology of novel  F9  defects and determination of mutation-associated FIX inhibitor risks.
authors.affiliation: Molecular Genetics of Haemophilia Laboratory, Instituto de Medicina Experimental IMEX, CONICET-Academia Nacional de Medicina, Pacheco de Melo 3081, Ciudad de Buenos Aires 1425, Argentina. pradic@hematologia.anm.edu.ar
authors.forename: Claudia Pamela
authors.initials: CP
authors.lastname: Radic
authors.forename: Liliana Carmen
authors.initials: LC
authors.lastname: Rossetti
authors.forename: Miguel Martín
authors.initials: MM
authors.lastname: Abelleyro
authors.forename: Miguel
authors.initials: M
authors.lastname: Candela
authors.forename: Raúl
authors.initials: R
authors.lastname: Pérez Bianco
authors.forename: Miguel
authors.initials: M
authors.lastname: de Tezanos Pinto
authors.forename: Irene Beatriz
authors.initials: IB
authors.lastname: Larripa
authors.forename: Anne
authors.initials: A
authors.lastname: Goodeve
authors.forename: Carlos  Daniel
authors.initials: C
authors.lastname: De Brasi
mesh_terms: D001118:Argentina / Q000453:epidemiology; D001323:Autoantibodies / Q000097:blood; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D018389:Codon, Nonsense; D019295:Computational Biology; D004252:DNA Mutational Analysis / Q000379:methods; D005164:Factor IX / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D002836:Hemophilia B / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D006487:Hemostasis / Q000235:genetics*; D006801:Humans; D054643:INDEL Mutation; D008297:Male; D009154:Mutation; D020125:Mutation, Missense; D016017:Odds Ratio; D010375:Pedigree; D010641:Phenotype; D017354:Point Mutation; D015995:Prevalence; D011487:Protein Conformation; D012307:Risk Factors; D017384:Sequence Deletion; D012720:Severity of Illness Index; D013329:Structure-Activity Relationship
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D018389:Codon, Nonsense; D005164:Factor IX