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Prepublished online as a Blood First Edition Paper on April 3, 2003; DOI 10.1182/blood-2002-09-2951.
Blood, 15 July 2003, Vol. 102, No. 2, pp. 561-563 Factor VII gene intronic mutation in a lethal factor VII deficiency: effects on splice-site selectionFrom the Institut National de la Santé et de la Recherche Médicale (INSERM) U428, Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris V, Paris, France; Hôpital Européen Georges Pompidou, Laboratoire d'Hématologie, Paris, France; INSERM U468, Hôpital Henri Mondor, Créteil, France; and CHU Mustapha, Alger, Algeria
In a patient with lethal factor VII (FVII) deficiency, 2 homozygous nucleotide substitutions were identified in the F7 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 (Arg224Gln). 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 F7 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 a truncated protein (stop codon 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.
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