SummaryCoagulation factor XI (FXI) deficiency is an inherited autosomal recessive mild bleeding disorder. In this study, we report the molecular genetic analysis of FXI deficiency in six unrelated families of Portuguese origin. The Jewish type II mutation was found in two families, of seemingly Portuguese origin. Haplotype analysis in these families demonstrated that this mutation is of Jewish origin. In the remaining families, five novel FXI mutations have been identified. Two of these mutations (FXI IVS K -10T→A and FXI 1026G→T, cd 324) affect the FXI pre-mRNA splicing. A further two (FXI 307 ins AAGCAAT, cd 85 and FXI 1072 del A, cd 340) introduce frameshifts leading to premature termination codons. The FXI splicing mutation, 1026G→T cd 324, was found in compound heterozygosity with missense mutation FXI K518N. Analysis of the FXI mRNA from the latter genotype demonstrated new donor splice site usage. All reported mutations most likely result in functional null-alleles. In addition, three novel polymorphisms have been identified: at nt -138 in intron A, at codon D125 in exon 5 and at codon T249 in exon 8.

SummaryWe report the application of single-stranded conformation polymorphism (SSCP) analysis to the screening of 15 functionally important Protein S (PS) gene (PSα) regions (4.243 Kb) in 6 unrelated families with PS deficiencies. Direct sequencing of the fragments with altered migration patterns led to the identification of the corresponding molecular alterations. A missense mutation, G to T transversion at codon Cys598, and two different alterations, leading either to allelic exclusion, or premature termination of the protein translation: a G to A transition at codon Trp465 and a 1 nt (T) insertion at codon 265, were identified. The 1 nt insertion was observed in three apparently unrelated families but with a common geographical origin and the mutated allele was undetectable in platelet mRNAs of affected individuals. Family analysis confirmed, in each case, a perfect cosegregation of the mutation with the PS deficiency. We conclude that these alterations represent the causative mutations.

Antithrombin (AT), the most important coagulation serine proteases inhibitor, plays an important role in maintaining the hemostatic balance. Inherited AT deficiency, mainly characterized by predisposition to recurrent venous thromboembolism, is transmitted in an autosomal dominant manner. In this study, we analyzed the underlying genetic alterations in 12 unrelated Portuguese thrombophilic families with AT deficiency. At the same time, the modulating effect of the FV Leiden mutation, PT 20210A, PAI-1 4G, and MTHFR 677T allelic variants, on the thrombotic risk of AT deficient patients was also evaluated. Three novel frameshift alterations, a 4-bp deletion in exon 4 and two 1-bp insertions in exon 6, were identified in six unrelated type I AT deficient families. A novel missense mutation in exon 3a, which changes the highly conserved F147 residue, and a novel splice site mutation in the invariant acceptor AG dinucleotide of intron 2 were also identified in unrelated type I AT deficient families. In addition to these, two previously reported missense mutations changing the AT reactive site bond (R393-S394) and leading to type II-RS deficiency, and a previously reported cryptic splice site mutation (IVS4-14GfiA), were also identified. In these families, increased thrombotic risk associated with co-inheritance of the FV Leiden mutation and of the PAI-1 4G variant was also observed. In conclusion, we present the first data regarding the underlying genetic alterations in Portuguese thrombophilic families with AT deficiency, and confirm that the FV Leiden mutation and probably the PAI-1 4G variant represent additional thrombotic risk factors in these families. Am.

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