Related Experiment Video
Updated: Aug 16, 2026
A Phenotyping Regimen for Genetically Modified Mice Used to Study Genes Implicated in Human Diseases of Aging
Published on: July 14, 2016
Genetic analysis and functional characterization of prothrombins Corpus Christi (Arg382-Cys), Dhahran (Arg271-His),
A S O'Marcaigh1, W L Nichols, N L Hassinger
1Section of Pediatric Hematology, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
Insights
Two new prothrombin variants, Corpus Christi and Dhahran, reveal distinct functional defects and bleeding tendencies. Mutations impact thrombin
Area of Science:
- Hematology
- Molecular Biology
- Genetics
Background:
- Hereditary dysprothrombinemia involves dysfunctional prothrombin variants.
- Understanding these variants is crucial for diagnosing bleeding disorders.
Observation:
- Two kindreds presented with distinct prothrombin variants: Corpus Christi and Dhahran.
- Prothrombin Corpus Christi showed reduced clotting activity but normal amidolytic and platelet activity.
- Prothrombin Dhahran exhibited reduced clotting activity but normal amidolytic activity.
Findings:
- Prothrombin Corpus Christi mutation (Cys382) affects the fibrinogen-binding exosite.
- Prothrombin Dhahran mutation (His271) abolishes Factor Xa cleavage, producing meizothrombin.
- Both mutations, along with a premature stop codon variant, occurred at CpG sites, common in dysprothrombinemia.
- Homozygous prothrombin Dhahran individuals had severe bleeding (5-7% activity), unlike prothrombin Corpus Christi probands (2% activity).
Implications:
- Thrombin's role in hemostasis extends beyond fibrinogen clotting.
- Genetic analysis of prothrombin variants aids in understanding bleeding disorder mechanisms.
- CpG dinucleotides are hotspots for mutations in hereditary dysprothrombinemia.
Abstract:
The structural abnormalities and functional characteristics of dysfunctional prothrombin variants in two new kindreds have been determined. Prothrombin Corpus Christi (family 1) was purified and found to have markedly reduced fibrinogen clotting activity, yet normal amidolytic and near-normal platelet aggregating activity. A transition (C to T) at nucleotide position 8885, present in the heterozygous form in affected family members, resulted in the substitution of Cys for Arg 382. This substitution results in the loss of a positive charge within the fibrinogen-binding exosite of thrombin, thus accounting for the observed functional defect. A heterozygous C to T transition was also present at position 19994 in other family members with a hypoprothrombinemic phenotype. This mutation results in the replacement of Gln 541 (CAA) by a premature stop codon (TAA). Prothrombin Dhahran (family 2) was found to have markedly reduced fibrinogen clotting activity, but normal amidolytic activity. Affected family members were found to have a G to A transition at nucleotide position 7312 resulting in the substitution of His for Arg 271. This substitution results in the abolition of a factor Xa cleavage site, yielding meizothrombin rather than thrombin, on activation of prothrombin Dhahran by factor Xa. All but one of the above mutations occur at CpG dinucleotides, thus further supporting the observation of a high incidence of CpG transitions in hereditary dysprothrombinemia. The significant bleeding tendencies of individuals homozygous for prothrombin Dhahran (prothrombin clotting activity 5% to 7%) contrast sharply with the absence of significant chronic bleeding in the proband expressing prothrombin Corpus Christi (prothrombin clotting activity 2%). Our findings underscore the capacity of thrombin to contribute to clinical hemostasis by mechanisms other than its fibrinogen clotting activity.
