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- Kunz, G, et al.
(författare)
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Naturally occurring mutations in the thrombomodulin gene leading to impaired expression and function
- 2002
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Ingår i: Blood. - 1528-0020. ; 99:10, s. 3646-3653
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Tidskriftsartikel (refereegranskat)abstract
- Sporadic mutations in the thrombomodulin (TM) gene occur in patients with both arterial and venous thrombosis, but the effects of these mutations on expression and function are largely unexplored. Full-length wild-type TM complementary DNA (cDNA) was incorporated into vector pcDNA6 for transfection into COS-7 cells for transient expression. Mutagenesis was performed to create 7 TM mutants with natural mutations either previously identified (Ala25Thr, Gly6lAla, Asp468Tyr, Pro477Ser, Pro483Leu) or reported here (an 11-base pair [bp] deletion, del791-801, leading to STOP306, and a missense mutation, Arg385Ser). Four mutations were found to detrimentally affect the level of expression of the TM protein. Of the missense mutations, 3 had reduced expression compared to wild-type TM (100%), Arg385Ser (50.2% +/- 5%, P < .001), Pro477Ser (76.8% +/-11%, P <.001), Pro483Leu (82.1% +/- 8%, P < .007). No TM protein expression could be detected on the cell surface for mutation del791-801. The cofactor activity of TM in protein C activation was also evaluated. The Michaelis constant (K,) for wild-type thrombin-TM complex was 634 +/- 6 nmol/L. Two mutants, with Arg385Ser and Pro477Ser, had Increased (P < .0001) K, 2967 +/- 283 nM, and 2342 +/- 219 nM, respectively, demonstrating impaired function of the thrombin-TM complex. This work presents biochemical evidence that certain (but not all) natural mutations In the TM gene reduce expression and impair function of the protein on the cell surface, and helps clarify the suggested contribution that these mutations might make to the risk of thromboembolic disease.
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2. |
- Norlund, Lena, et al.
(författare)
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A common thrombomodulin amino acid dimorphism is associated with myocardial infarction
- 1997
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Ingår i: Thrombosis and Haemostasis. - 0340-6245. ; 77:2, s. 51-248
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Tidskriftsartikel (refereegranskat)abstract
- Endothelial dysfunction and haemostatic imbalance are believed to be important aetiological factors in the development of acute coronary syndromes. Thrombomodulin (TM) is an integral membrane protein crucial for normal endothelial function and activation of the protein C anticoagulant pathway. We have investigated the importance of a common C/T dimorphism in the TM gene (nucleotide 1418) for development of premature myocardial infarction (MI). The C/T dimorphism predicts an Ala455 to Val replacement in the sixth EGF-like domain of TM. The dimorphism was investigated in 97 MI survivors and 159 healthy controls. The C allele was significantly more frequent among patients than controls (p = 0.035). The allele frequency for the C allele was 0.82 in the patients and 0.72 in the control group. The plasma concentration of TM was investigated among healthy controls but was not related to the C/T dimorphism. In conclusion, the association of the C allele with premature MI, suggests that the TM gene and the C/T dimorphism may be aetiological factors involved in the pathogenesis of MI. Possibly, the Ala455 to Val replacement may affect the function of the TM molecule and the activation of the protein C anticoagulant pathway.
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