Association of the R67X and W303X non-sense polymorphisms in the protein Z-dependent protease inhibitor gene with idiopathic recurrent miscarriage

Plasma concentration of protein Z-dependent protease inhibitor and ZPI exon 3 mutations in preeclampsia

Protein Z-dependent protease inhibitor (ZPI) serves as a cofactor of inhibition of FXa and FXIa by protein Z. The levels of protein Z and polymorphisms have been shown in preeclampsia (PE) patients, but the plasma levels of ZPI and ZPI gene mutations were not reported yet. The principal aim of this study was to identify the concentration of ZPI and gene polymorphism in PE. ZPI levels were determined in 113 PE patients (age: 29.9 ± 3.9 years) and in 106 controls (normal pregnancy, age: 27.0 ± 2.8 years). ZPI was measured by enzyme-linked immunosorbent assay kit, and the gene polymorphism was determined by polymerase chain reaction and sequencing. The results showed ZPI antigen was found to be significantly lower in PE patients than in controls (ZPI, 1.24 ± 0.29 mg/L vs. 1.94 ± 0.35 mg/L, p < 0.05). The exon-3 missense mutations were distributed in patients and controls and there was no convincing correlation between these mutations and PE. It was of interest to observe a close relationship between the genotypes of the exon 3 polymorphisms 181 A > G and 481 A > T in the ZPI gene.Impact statementWhat is already known on this subject? The occurrence of PE is closely related to dysfunction of coagulation, and it is known that the decrease of PZ level can increase the occurrence probability of PE, while the polymorphism of PZ is not related to the occurrence of PE. As a cofactor of PZ, the content and polymorphism of ZPI which related to the occurrence of PE is worth further study.What the results of this study add? ZPI antigen was found to be significantly lower in PE patients than in controls, but there was no convincing correlation between exon-3 mutations and PE.What the implications are of these findings for clinical practice and/or further research? Our results support the view that ZPI plays a significant role in anticoagulant, and the genotype of the 181 gene polymorphism in exon-3 and 481 gene polymorphism in exon-3 are closely related. Other mutations like 435T > G(Phe145Leu), 972G > A(Trp324X), 1151A > G(Gln384Arg) are necessary to confirm the association between ZPI and prothrombotic state including PE.

Protein Z, an anticoagulant protein with expanding role in reproductive biology

Protein Z (PZ) is a vitamin K-dependent factor characterized by its homology to other vitamin K-dependent factors (factors VII, IX, and X, protein C and protein S), but lacks any enzymatic activity. Instead, PZ acts as a cofactor for the inhibition of factor Xa through the serpin PZ-dependent protease inhibitor (ZPI). PZ deficiency is associated with a procoagulant state, highlighted by excessive FXa secretion and thrombin production, and is linked with several thrombotic disorders, including arterial vascular and venous thromboembolic diseases. A role for the PZ-ZPI complex in the regulation of physiological pregnancy has been demonstrated, highlighted by the progressive elevation in PZ levels in the first trimester of gestation, which then steadily decline toward delivery. An association between altered plasma PZ concentrations and adverse pregnancy outcomes (recurrent miscarriage, stillbirth, preeclampsia, intrauterine growth restriction, and placental abruption) has been reported. The mechanism by which PZ deficiency leads to adverse pregnancy outcomes is not clear, but it is multifactorial. It may be attributed to the anti-PZ IgG and IgM autoantibodies, which apparently act independently of classical antiphospholipid antibodies (lupus anticoagulant, anticardiolipin, and anti-β2-glycoprotein I antibodies). PZ deficiency has also been reported to be constitutional, and a number of variants in the PROZ (PZ) gene and SERPINA10 (ZPI) gene are linked with specific adverse pregnancy complications. This review summarizes the relationship between adverse pregnancy outcomes and acquired and constitutional PZ-ZPI deficiency, in order to understand whether or not PZ deficiency could be considered as a risk factor for poor pregnancy outcomes.

Genetics of recurrent miscarriage: challenges, current knowledge, future directions

Recurrent miscarriage (RM) occurs in 1-3% of couples aiming at childbirth. Due to multifactorial etiology the clinical diagnosis of RM varies. The design of genetic/"omics" studies to identify genes and biological mechanisms involved in pathogenesis of RM has challenges as there are several options in defining the study subjects (female patient and/or couple with miscarriages, fetus/placenta) and controls. An ideal study would attempt a trio-design focusing on both partners as well as pregnancies of the couple. Application of genetic association studies focusing on pre-selected candidate genes with potential pathological effect in RM show limitations. Polymorphisms in ∼100 genes have been investigated and association with RM is often inconclusive or negative. Also, implication of prognostic molecular diagnostic tests in clinical practice exhibits uncertainties. Future directions in investigating biomolecular risk factors for RM rely on integrating alternative approaches (SNPs, copy number variations, gene/protein expression, epigenetic regulation) in studies of single genes as well as whole-genome analysis. This would be enhanced by collaborative network between research centers and RM clinics.

Two missense mutations identified in venous thrombosis patients impair the inhibitory function of the protein Z dependent protease inhibitor

Protein Z-dependent protease inhibitor (ZPI) is a plasma inhibitor of factor (F)Xa and FXIa. In an earlier study, five mutations were identified within the ZPI gene of venous thrombosis patients and healthy controls. Two of these were nonsense mutations and three were missense mutations in important regions of the protein. Here we report that two of these latter three mutations, F145L and Q384R, impair the inhibitory function of ZPI in vitro. Recombinant wild-type and mutant proteins were prepared; stability in response to thermal challenge was similar. Inhibition of FXa in the presence of the cofactor protein Z was reduced 68-fold by the Q384R mutant; inhibition of FXIa by the F145L mutant was reduced two- to three-fold compared to the wild-type ZPI. An analysis of all five ZPI mutations was undertaken in a cohort of venous thrombosis patients (n=550) compared to healthy controls (n=600). Overall, there was a modest increase in incidence of these mutations in the thrombosis group (odds ratio 2.0, 1.05-3.7, p=0.044). However, in contrast to W324X (nonsense mutation), the Q384R missense mutation and R88X nonsense mutation were evenly distributed in patients and controls; F145L was rare. The final mutation (S143Y) was also rare and did not significantly alter ZPI function in laboratory studies. The F145L and particularly the Q384R mutation impaired the function of the coagulation inhibitor ZPI; however, there was no convincing association between these mutations and venous thrombosis risk. The functional role for ZPI in vivo has yet to be clarified.