Factor VII gene intronic mutation in a lethal Factor VII deficiency: effects on splice-site selection Short title Splicing at cryptic site in lethal FVII deficiency Authors

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 a truncated protein (stop codon upstream of nt-10588). These findings, which suggest the existence of a mechanism selecting one single splice site among multiple cryptic sites, explain the patient’s phenotype. [email protected] For personal use only. on September 14, 2017. by guest www.bloodjournal.org From