Submitted September 27, 2002
Accepted March 19, 2003
Factor VII gene intronic mutation in a lethal Factor VII deficiency: effects on splice-site selection
Keren Borensztajn, Marie-Laure Sobrier, Anne-Marie Fischer, Ouerdia Chafa, Serge Amselem, and Jacqueline Tapon-Bretaudiere*
INSERM, Unite 428, Faculte des Sciences Pharmaceutiques et Biologiques, Universite Paris V, Paris, France; Laboratoire d'Hematologie, Hopital Europeen Georges Pompidou, Paris, France
INSERM, Unite 468, Hopital Henri Mondor, Creteil, France
CHU Mustapha, Alger Centre, Algeria
* Corresponding author; email: jacqueline.tapon-bretaudiere{at}hop.egp.ap-hop-paris.fr.
In a patient with lethal Factor (F) VII deficiency, two homozygous nucleotide substitutions were identified in the FVII gene: a IVS7+2T>G transversion involving the IVS7 donor splice site, followed by a mutation at nucleotide 10588 that would result in a missense variation (R224Q). The mutated splice site, located within the first repeat of a minisatellite, is followed by a variable number of pseudo-sites, normally silent. To investigate the consequences of this mutation on FVII splicing, we designed normal and mutant minigenes, spanning exons 5 to 8. In cells transfected with the mutant construct, no normal splicing occurred. Only spliced transcripts including the first minisatellite repeat were observed, resulting from the activation of the most proximal wild-type pseudo-site, which would generate truncated proteins (stop codon located upstream of nucleotide 10588). These findings, which suggest the existence of a mechanism selecting one single splice site among multiple cryptic sites, explain the patient's phenotype.
