The Contributions of Thrombophilic Mutations to Genetic Susceptibility to Deep Venous Thrombosis in Iraqi Patients

Diagnosis and treatment of venous thromboembolism during pregnancy relate to genetic polymorphism

OBJECTIVES

Previous research had shown that age, a positive family history, comorbidities, major surgical operations, gestation, and use of several medications could increase the incidence of venous thromboembolism (VTE). With the development of medical and clinical individualized treatment, many people exposed to above risk factors did not develop VTE, suggested that genetic factors are also involved in the development of VTE. In this review, we aim to summarize VTE diagnosis and treatment in pregnancy women related to gene polymorphism.

METHODS

A comprehensive electronic search using PubMed, MEDLINE, EMBASE and Web of Science was conducted to find relevant journal articles with key search terms including: "pregnancy OR pregnant," "venous thromboembolism OR VTE," "deep vein thrombosis OR DVT," "pulmonary embolism OR PE," and "genetic OR gene." Prominent publications from establishment of database till present were analysed to achieve a deeper understanding of VTE during pregnancy relate to genetic polymorphism, and the information was then collated to form this review.

RESULTS

The literature review revealed that inherited thrombophilia significantly associated with the development of VTE, especially the factor V Leiden (FVL) and prothrombin gene mutation (PGM). Furthermore, the role of methylenetetrahydrofolate reductase (MTHFR) gene mutation in the development of pregnancy-related VTE remains controversial, further study is required. In the present study, Marburg I polymorphism (G511 E), c.1538 G>A and c.1601 G>A in Factor V (FV), JAK2V617 F mutation were reported as an independent risk factor for VTE, there is no sufficient evidence to confirm the gene mutation is related to VTE during pregnancy, these factors appearing as another promising potential diagnostic marker of VTE during pregnancy. Besides, the dosages of heparin in the treatment of VTE during pregnancy need be adjusted according to gene polymorphism of these population, particularly FVL or PGM carriers, and this area is not studied deeply, it is worth further study.

CONCLUSION

Inherited thrombophilia significantly associated with the development of VTE, especially the FVL and PGM, however the relation between MTHFR gene mutation and pregnancy-related VTE remains controversial, further study is needed. In addition, the dosages of heparin in the treatment of VTE during pregnancy suggested to adjusted based on gene polymorphism in FVL and PGM, and establish better prediction models is a direction of future research.

Impact of Genetic Variations on Thromboembolic Risk in Saudis with Sickle Cell Disease

BACKGROUND

Sickle cell disease (SCD) is a Mendelian disease characterized by multigenic phenotypes. Previous reports indicated a higher rate of thromboembolic events (TEEs) in SCD patients. A number of candidate polymorphisms in certain genes (e.g., FVL, PRT, and MTHFR) were previously reported as risk factors for TEEs in different clinical conditions. This study aimed to genotype these genes and other loci predicted to underlie TEEs in SCD patients.

METHODOLOGY

A multi-center genome-wide association study (GWAS) involving Saudi SCD adult patients with a history of TEEs (n = 65) and control patients without TEE history (n = 285) was performed. Genotyping used the 10× Affymetrix Axiom array, which includes 683,030 markers. Fisher's exact test was used to generate p-values of TEE associations with each single-nucleotide polymorphism (SNP). The haplotype analysis software tool version 1.05, designed by the University of Göttingen, Germany, was used to identify the common inherited haplotypes.

RESULTS

No association was identified between the targeted single-nucleotide polymorphism rs1801133 in MTHFR and TEEs in SCD (p = 0.79). The allele frequency of rs6025 in FVL and rs1799963 in PRT in our cohort was extremely low (<0.01); thus, both variants were excluded from the analysis as no meaningful comparison was possible. In contrast, the GWAS analysis showed novel genome-wide associations (p < 5 × 10-8) with seven signals; five of them were located on Chr 11 (rs35390334, rs331532, rs317777, rs147062602, and rs372091), one SNP on Chr 20 (rs139341092), and another on Chr 9 (rs76076035). The other 34 SNPs located on known genes were also detected at a signal threshold of p < 5 × 10-6. Seven of the identified variants are located in olfactory receptor family 51 genes (OR51B5, OR51V1, OR51A1P, and OR51E2), and five variants were related to family 52 genes (OR52A5, OR52K1, OR52K2, and OR52T1P). The previously reported association between rs5006884-A in OR51B5 and fetal hemoglobin (HbF) levels was confirmed in our study, which showed significantly lower levels of HbF (p = 0.002) and less allele frequency (p = 0.003) in the TEE cases than in the controls. The assessment of the haplotype inheritance pattern involved the top ten significant markers with no LD (rs353988334, rs317777, rs14788626882, rs49188823, rs139349992, rs76076035, rs73395847, rs1368823, rs8888834548, and rs1455957). A haplotype analysis revealed significant associations between two haplotypes (a risk, TT-AA-del-AA-ins-CT-TT-CC-CC-AA, and a reverse protective, CC-GG-ins-GG-del-TT-CC-TT-GG-GG) and TEEs in SCD (p = 0.024, OR = 6.16, CI = 1.34-28.24, and p = 0.019, OR = 0.33, CI = 0.13-0.85, respectively).

CONCLUSIONS

Seven markers showed novel genome-wide associations; two of them were exonic variants (rs317777 in OLFM5P and rs147062602 in OR51B5), and less significant associations (p < 5 × 10-6) were identified for 34 other variants in known genes with TEEs in SCD. Moreover, two 10-SNP common haplotypes were determined with contradictory effects. Further replication of these findings is needed.

A genetic risk factor for thrombophilia in a Han Chinese family

Thrombophilia is a multifactorial disorder involving environmental and genetic factors. Well‑known factors that result in predisposition to congenital disorders associated with thrombophilia include antithrombin deficiency, protein C and S deficiency, Factor V Leiden mutation, abnormal prothrombin and antiphospholipid syndrome. The present study revealed an association between a mutation of the F2 gene, which codes for coagulation factor II, thrombin, and the risk of thrombophilia in a Han Chinese family, of which four members (I‑2, II‑2, II‑3 and III‑1) had a history of deep venous thromboembolism. The disease was measured in this family using laboratory measurements and computed tomography angiography. To identify the abnormality underlying the increased thrombophilia risk, whole‑exome sequencing technology was used to analyze two affected individuals (II‑2 and III‑1). An exonic missense F2 mutation, T165M (NM_000506:c.C494T:p.T165M;rs5896), was identified from a total of 2,222 and 2,203 genetic variations observed in the two affected individuals, respectively, which were subsequently filtered and confirmed using Sanger sequencing. I‑2, II‑3 and III‑1 shared this mutation with the proband (II‑2), and II‑6 had a heterozygous form of the mutation. This deleterious mutation was not identified in normal controls. The present study may improve understanding of the function of the F2 gene.

Association of Methylenetetrahydrofolate Reductase C677T Polymorphism with Hyperhomocysteinemia and Deep Vein Thrombosis in the Iranian Population

PURPOSE

Deep venous thrombosis (DVT) is a common but elusive condition characterized by a high morbidity and mortality rate. The aim of the present study was to investigate the correlation between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism with plasma total homocysteine (tHcy) levels and DVT risk in an Iranian population.

MATERIALS AND METHODS

Our study population consisted of 67 patients with a diagnosis of DVT and 67 healthy subjects as controls. Genotyping of MTHFR C677T polymorphism was performed by the polymerase chain reaction technique combined with restriction enzyme fragment length polymorphism (PCR-RFLP) and measurement of tHcy levels was done by enzyme immunoassay method.

RESULTS

Plasma tHcy levels were significantly higher in DVT patients than controls (18.09±7.6 vs. 10.5±4.3, P=0.001). Also, plasma tHcy levels were significantly higher in MTHFR 677TT genotypes compared to 677CC genotypes in both DVT patients (P=0.016) and controls (P=0.03). Neither heterozygote nor homozygote genotypes of MTHFR C677T polymorphism was significantly correlated with DVT (P>0.05). The distribution of MTHFR C677T genotypes was similar between men and women in both DVT patients and controls (P>0.05). Moreover, the frequency of mutant 677T allele did not differ significantly between the two groups (28.3% vs. 21.6%, P=0.15).

CONCLUSION

Based on this study, we propose that hyperhomocysteinemia but not homozygosity for MTHFR C677T polymorphism is a significant risk factor for DVT in the Iranian population. Also, MTHFR 677TT genotype is a determinant of elevated plasma tHcy levels.