Thromb Haemost 2008; 99(03): 523-530
DOI: 10.1160/TH07-12-0723
Blood Coagulation, Fibrinolysis and Cellular Haemostasis
Schattauer GmbH

Molecular characterization of two novel mutations causing factor XI deficiency: A splicing defect and a missense mutation responsible for a CRM+ defect

Ilaria Guella
1   Department of Biology and Genetics for Medical Sciences, University of Milan, Milan, Italy
,
Giulia Soldà
1   Department of Biology and Genetics for Medical Sciences, University of Milan, Milan, Italy
,
Silvia Spena
1   Department of Biology and Genetics for Medical Sciences, University of Milan, Milan, Italy
,
Rosanna Asselta
1   Department of Biology and Genetics for Medical Sciences, University of Milan, Milan, Italy
,
Rossella Ghiotto
1   Department of Biology and Genetics for Medical Sciences, University of Milan, Milan, Italy
,
Maria Luisa Tenchini
1   Department of Biology and Genetics for Medical Sciences, University of Milan, Milan, Italy
,
Giancarlo Castaman
2   Department of Hematology and Hemophilia and Thrombosis Center, San Bortolo Hospital, Vicenza, Italy
,
Stefano Duga
1   Department of Biology and Genetics for Medical Sciences, University of Milan, Milan, Italy
› Author Affiliations
Financial support: S. Duga is a recipient of a Bayer Hemophilia Early Career Investigator Award 2006. This work was also supported by MIUR (Ministero dell’Istruzione, dell’Università e della Ricerca): FIRST 2006 (Fondo per gli Investimenti Ricerca Scientifica e Tecnologica).
Further Information

Publication History

Received: 06 December 2007

Accepted after major revision: 26 January 2008

Publication Date:
07 December 2017 (online)

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Summary

Severe factor XI (FXI) deficiency is a bleeding disorder generally inherited as an autosomal recessive trait and characterized by haemorrhagic symptoms mainly associated with injury or surgery. So far, more than 150 causative molecular defects have been identified throughout the F11 gene. In the present study, we investigated the molecular basis of FXI deficiency in two Italian patients. Mutational screening of the F|| gene disclosed a novel missense substitution (Arg184Gly) in exon 7 and two splicing mutations: a novel G>A transition affecting the last nucleotide of exon 4 (325G>A), and the already known IVS6+3A>G. RT-PCR assays were performed on total RNA extracted from platelets and lymphocytes of each patient. Se- quencing of RT-PCR products demonstrated that both 325G>A and IVS6+3A>G mutations abolish the corresponding donor splice site, causing the skipping of the affected exon; this in turn results in a frameshift introducing a premature termination codon. Expression of recombinant FXI-Arg184Gly revealed a 70% reduction in FXI activity, suggesting that the Arg184Gly mutation might cause a cross-reactive material positive (CRM+) deficiency. In conclusion, the functional consequences of two splicing mutations leading to FXI deficiency have been elucidated. Moreover, we report a novel missense mutation in the FIX-binding region of the FXI A3 domain leading to a CRM+ deficiency.