[Show abstract][Hide abstract] ABSTRACT: Factor XII (FXII) deficiency is a recessive Mendelian trait due to mutations in the F12 gene. There is no bleeding associated with FXII deficiency, but FXII deficiency has been reported to be associated with risk of thrombosis in some studies.
We examined the functional effect of two naturally-occurring mutations in two Spanish FXII deficient families: a C/G substitution at position -8, and a C/T substitution at position -13. Both mutations were located on a putative HNF4 binding site of F12 gene promoter. We also analyzed the F12 C46T polymorphism (rs1801020), associated with a decrease in the FXII levels, which also segregated in both families. A fragment containing each one of both -8 and -13 mutations, was cloned 5' of a reporter gene. We compared the in vitro expression of these constructs to the wild type expression.
Our analyses confirm that the -8C/G and the -13C/T mutations decreased expression levels, demonstrating that both mutations are involved in the observed FXII deficiency. In addition, electrophoretic shift analyses suggest that they alter the union of nuclear proteins to the promoter. Coinheritance of these mutations with the C46T polymorphism, result in a significant genotype-phenotype correlation.
We have identified two naturally-occurring mutations in the F12 promoter that drastically reduce FXII levels. Knowing rare genetic alterations in the F12 gene, together with the C46T common variant, may yield further understanding about the genetic architecture of FXII levels, which may have a role in the risk of thrombosis.
Thrombosis Research 09/2009; 125(2):e55-60. DOI:10.1016/j.thromres.2009.08.019 · 2.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We studied 3 Spanish patients with <1% FXII levels. DNA sequencing of the whole F12 gene identified 15 genetic variants. Molecular analyses of F12 mRNA demonstrated that the deficiency was caused by 5281delG in exon 9 of Patient 1 (in the homozygous state) and the 6306delG in exon 12 and another deletion of 23 bp in intron 8 of Patient 2 (both in the heterozygous state). Finally, a G-8C transversion was found in the homozygous state in Patient 3. Based on previous data, including a mouse model, the G-8C might be responsible for the FXII deficiency. None of these variants were present in 40 controls.