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Molecular defects in CRM+ factor VII deficiencies: modelling of missense mutations in the catalytic domain of FVII
F Bernardi1, D L Liney, P Patracchini
1Centro Studi Biochimici delle Patologie del Genoma Umano-Istituto di Chimica Biologica, Ferrara, Italy.
Abstract:
The molecular defects causing CRM+ factor VII deficiency were investigated in seven unrelated subjects and several members of their families. Four missense mutations located in the catalytic domain of factor VII were found. The previously reported 304Arg-->Gln substitution was present in the homozygous and heterozygous forms, with different polymorphic haplotypes, thus demonstrating that it is recurrent and frequent in the Italian population. The 310Cys-->Phe substitution was found in the homozygous form and in the compound heterozygous condition with the nonsense mutation 356Trp-->stop. Two missense mutations, 298Met-->Ile and 342Gly-->Arg, were found in the homozygous and in the heterozygous condition respectively. Molecular heterogeneity was further increased by finding of the 353Arg-->Gln polymorphism in the doubly heterozygous condition with the 304 and 342 mutations. Plausible explanations for loss of FVII function were found by inspecting a model of the serine protease domain of factor VIIa. Inefficient activation of the catalytic site is predicted for 298Met-->Ile. 342Gly-->Arg would directly distort the geometry of the 'oxyanion hole' preventing formation of a substrate enzyme intermediate. 310Cys-->Phe is predicted to have an adverse effect on tissue factor interaction. These mutations point to important regions of the factor VII molecule.
Insights
Researchers identified four novel mutations in factor VII (FVII) causing factor VII deficiency. These genetic defects impact FVII function and highlight key regions of the FVII molecule.
Area of Science:
- Genetics
- Molecular Biology
- Hematology
Background:
- Congenital factor VII deficiency is a rare bleeding disorder.
- Understanding the molecular basis of CRM+ factor VII deficiency is crucial for diagnosis and treatment.
Purpose of the Study:
- To identify and characterize the molecular defects responsible for CRM+ factor VII deficiency in seven unrelated subjects.
- To correlate identified mutations with FVII function using structural modeling.
Main Methods:
- DNA sequencing to identify mutations in the factor VII gene.
- Haplotype analysis to assess mutation recurrence.
- Structural modeling of the factor VIIa serine protease domain to predict functional impact.
Main Results:
- Four missense mutations (304Arg-->Gln, 310Cys-->Phe, 298Met-->Ile, 342Gly-->Arg) were identified in the catalytic domain of factor VII.
- The 304Arg-->Gln mutation is recurrent and frequent in the Italian population.
- Structural modeling predicted impaired catalytic site activation, altered substrate interaction, and reduced tissue factor binding for the identified mutations.
Conclusions:
- Identified mutations provide insights into the molecular mechanisms underlying CRM+ factor VII deficiency.
- These findings underscore the importance of specific regions within the factor VII molecule for its function.
- The study contributes to the understanding of genetic heterogeneity in factor VII deficiency.