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CORRESPONDENCE Plasma TAFI antigen (Ag) levels are almost entirely under the
control of the TAFI gene.1-3 Several
polymorphisms found to be associated with TAFI Ag levels have been
already described,1-4 but a recently performed
segregation-linkage analysis indicates that the TAFI-linked
quantitative trait loci is unlikely to be one of these already
identified polymorphisms.5 Recently, Brouwers et al reported the identification a new
polymorphism, 1040C/T, in the coding region of the TAFI
gene that results in the Thr325Ile
substitution.6 This polymorphism is of particular interest
because, besides its association with TAFI plasma levels, studies using
recombinant proteins have demonstrated a functional effect of the
Thr325Ile substitution on the stability of activated TAFI resulting in
altered antifibrinolytic activity, TAFI-Ile325 having a 60% greater
antifibrinolytic activity than TAFI-Thr325.7 We evaluated the contribution of this polymorphism to the risk of
myocardial infarction (MI) using a large European multicentric case-control study, the HIFMECH study. It consisted of white
male patients younger than 60 years who survived a first
MI (excluding patients with familial hypercholesterolemia and
insulin-dependent diabetes mellitus) and population-based men of the
same age recruited from 4 different centers (Stockholm, London,
Marseilles, San Giovanni Rotondo). Consecutive patients were invited to
participate along with randomly selected healthy individuals from the
same catchment areas. In all, a total of 533 postinfarction patients
and 575 controls were included in the study. Patients were
studied 3 to 6 months after the acute event. Patients and
control subjects were examined in parallel in the early morning after
an overnight fast. Genotyping was performed in 1096 individuals, and citrate plasma was
available for TAFI Ag determination in 914 individuals. In controls,
the genotype distribution of Thr325Ile polymorphism was in
Hardy-Weinberg equilibrium in each center, and there was no significant
evidence of a difference in this distribution by center
(P = .14), the overall frequency of the Ile allele being 0.31 (95% CI, 0.28-0.34). This polymorphism was in strong linkage disequilibrium with the previously described Ala147Thr and
C1542>G polymorphisms of the TAFI gene (D' = In conclusion, in this large multicentric case/control study, the Thr325Ile polymorphism of the TAFI gene does not influence the risk of MI. But as pointed out by Brouwers et al,6 the fact that the Thr325 allele could have the opposite effect by increasing TAFI Ag levels and decreasing TAFI antifibrinolytic activity at the same time deserves to be further studied to assess its influence on the risk of thrombosis.
Pierre E. Morange, Mireille Henry, Corinne Frere, and Irène Juhan-Vague, on behalf of the
HIFMECH study group
References
1.
Crainich P, Tang Z, Macy EM, et al.
A polymorphism at position
2.
Henry M, Aubert H, Morange PE, et al.
Identification of polymorphisms in the promoter and the 3' region of the TAFI gene: evidence that plasma TAFI antigen levels are strongly genetically controlled.
Blood.
2001;97:2053-2058
3.
Franco RF, Fagundes MG, Meijers JCM, et al.
Identification of polymorphisms in the 5'-untranslated region of the TAFI gene: relationship with plasma TAFI levels and risk of venous thrombosis.
Haematologica.
2001;86:510-517 4. Zhao L, Morser J, Bajzar L, Nesheim M, Nagashima M. Identification and characterization of two thrombin-activable fibrinolysis inhibitor isoforms. Thromb Haemost. 1998;80:949-955[Medline] [Order article via Infotrieve]. 5. Tregouet DA, Aubert H, Henry M, et al. Combined segregation-linkage analysis of plasma thrombin activatable fibrinolysis inhibitor (TAFI) antigen levels with TAFI gene polymorphisms. Hum Genet. 2001;109:191-197[CrossRef][Medline] [Order article via Infotrieve].
6.
Brouwers GJ, Vos HL, Leebeek FWG, et al.
A novel, possibly functional, single nucleotide polymorphism in the coding region of the thrombin-activatable fibrinolysis inhibitor (TAFI) gene is also associated with TAFI levels.
Blood.
2001;98:1992-1993 7. Schneider M, Boffa M, Stewart R, Rahman ML, Koschinsky M, Nesheim M. Two naturally occurring variants of TAFI (Thr 325 and Ile 325) differ substantially with respect to thermal stability and antifibrinolytic activity of the enzyme. J Biol Chem. Prepublished on October 29, 2001, as 10.1074/jbc.M104444200. This article has been cited by other articles:
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