Identification of the first Alu-mediated large deletion involving the F5 gene in a compound heterozygous patient with severe factor V deficiencyFinancial support: The financial support of PRIN (Programmi di Ricerca Scientifica di Rilevante Interesse Nazionale, Grant n. 2008RXFZ38_002) is gratefully acknowledged.
Received: 04 March 2011
Accepted after major revision: 11 May 2011
25 November 2017 (online)
Factor V (FV) deficiency is a rare autosomal recessive haemorrhagic disorder associated with moderate to severe bleeding symptoms. Conventional mutational screening leads to a complete molecular genetic diagnosis only in about 80–90% of cases. Large gene rearrangements, which could explain at least part of the “missing alleles” have not been reported so far in FV-deficient patients. In this work, we investigated a family with hereditary FV deficiency, in which the proband is compound heterozygous for a 205-Kb deletion, involving the first seven exons of F5, and the entire selectin P, L, and E genes, and for a novel splicing mutation (IVS12+5G>A). The deletion breakpoints, determined by using a combination of semi-quantitative real-time PCR and long PCR assays, occurred within AluY repeat sequences, suggesting an Alu-mediated unequal homologous recombination as the mechanism responsible for the deletion. The in vitro characterisation of the IVS12+5G>A mutation demonstrated that this mutation causes the skipping of exon 12 and the activation of a cryptic splice site. Low levels of residual wild-type splicing were also detectable, in agreement with the notion that the complete absence of FV may be not compatible with life.
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