Identification of the first Alu-mediated large deletion involving the F5 gene in a compound heterozygous patient with severe factor V deficiency

Ilaria Guella; Elvezia Maria Paraboschi; Willem A. van Schalkwyk; Rosanna Asselta; Stefano Duga

doi:10.1160/TH11-03-0149

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 2011; 106(02): 296-303
DOI: 10.1160/TH11-03-0149

Blood Coagulation, Fibrinolysis and Cellular Haemostasis

Schattauer GmbH

Identification of the first Alu-mediated large deletion involving the F5 gene in a compound heterozygous patient with severe factor V deficiency

Ilaria Guella

¹Dipartimento di Biologia e Genetica per le Scienze Mediche, Università degli Studi di Milano, Milan, Italy

,

Elvezia Maria Paraboschi

¹Dipartimento di Biologia e Genetica per le Scienze Mediche, Università degli Studi di Milano, Milan, Italy

,

Willem A. van Schalkwyk

²Department of Haematology, University of Cape Town and National Health Laboratory Service, Red Cross Children’s Hospital, Cape Town, South Africa

,

Rosanna Asselta

¹Dipartimento di Biologia e Genetica per le Scienze Mediche, Università degli Studi di Milano, Milan, Italy

,

Stefano Duga

¹Dipartimento di Biologia e Genetica per le Scienze Mediche, Università degli Studi di Milano, Milan, Italy

› Author Affiliations

Abstract

Summary

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.

Keywords

Coagulation factor V - factor V deficiency - large deletion - Alu sequence - splicing mutation

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References

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