Association of methionine synthase and thymidylate synthase genetic polymorphisms with idiopathic recurrent pregnancy loss

Understanding recurrent pregnancy loss: recent advances on its etiology, clinical diagnosis, and management

Recurrent pregnancy loss (RPL) has become an important reproductive health issue worldwide. RPL affects about 2%-3% of reproductive-aged women, and makes serious threats to women's physical and mental health. However, the etiology of approximately 50% of RPL cases remains unknown (unexplained RPL), which poses a big challenge for clinical management of these patients. RPL has been widely regarded as a complex disease where its etiology has been attributed to numerous factors. Heretofore, various risk factors for RPL have been identified, such as maternal ages, genetic factors, anatomical structural abnormalities, endocrine dysfunction, prethrombotic state, immunological factors, and infection. More importantly, development and applications of next generation sequencing technology have significantly expanded opportunities to discover chromosomal aberrations and single gene variants responsible for RPL, which provides new insight into its pathogenic mechanisms. Furthermore, based upon patients' diagnostic evaluation and etiologic diagnosis, specific therapeutic recommendations have been established. This review will highlight current understanding and recent advances on RPL, with a special focus on the immunological and genetic etiologies, clinical diagnosis and therapeutic management.

Evaluating the Association Between Genetic Polymorphisms Related to Homocysteine Metabolism and Unexplained Recurrent Pregnancy Loss in Women

Objective

To investigate the relationship between unexplained recurrent pregnancy loss (URPL) and polymorphisms of homocysteine metabolism-related genes in women.

Materials and Methods

A case–control study included 90 women with two or more consecutive unexplained pregnancy losses and 92 controlled women without miscarriage history; the female participants were in the age category of 18–35 years. The high-resolution melting technique was used to detect the single-nucleotide variants related to homocysteine metabolism disorder, namely MTHFR C677T, MTHFR A1298C, MTR A2756G, and MTRR A66G polymorphism.

Results

The MTHFR C677T polymorphism had significantly correlation with URPL. Indeed, the frequency of the677T allele and genotypes (677CT, 677TT) in the URPL group was significantly higher than that in the control group (p < 0.05). However, the allele, as well as genotype distribution of MTHFR A1298C, MTR A2756G, and MTRR A66G polymorphisms showed no significant difference (p > 0.05). MTHFR 677CT-1298AC genotype combination led to a 9.0-fold increased risk of URPL (OR 9.0; 95% CI, 2.25–35.99; p = 0.001), while the risk increased 10.0-fold (OR 10.0; 95% CI, 1.8–55.53; p = 0.008) when participants had more than the 3 variant loci.

Conclusion

The MTHFR C677T polymorphism was a risk factor for URPL, and determining the MTHFR C677T polymorphism had a potential prediction of URPL risk. Moreover, the MTHFR C677T and MTHFR A1298C joint mutants might have a synergistic effect on URPL. Conversely, there is a lack of evidence suggesting the URPL risk of MTHFR A1298C, MTR A2756G, and MTRR A66G polymorphisms.

MTR, MTRR and CBS Gene Polymorphisms in Recurrent Miscarriages: A Case Control Study from North India

Background:

According to various epidemiological studies, the aetiology of recurrent miscarriages (RMs) is multifactorial. The goal of this study is to learn more about the link between genetic polymorphisms and RM.

Aim:

To evaluate the association of 5-Methytetrahydrofolate-Homocysteine Methyltransferase (MTR) A2756G, 5-Methytetrahydrofolate-Homocysteine Methyltransferase Reductase (MTRR) A66G and cystathionine beta-synthase (CBS) 844INS68 genetic polymorphisms with RM and also to understand the combined effect of the selected genotypes.

Study Setting and Design:

This was a hospital-based, case–control, observational study.

Materials and Methods:

A total of 516 participants were recruited in the present study, of which 200 RM cases and 258 controls were included in the present study. Fasting blood sample (~5ml) was drawn from all the participants and were screened for genetic polymorphisms of MTR A2756G, MTRR A66G and CBS 844INS68.

Statistical Analysis:

The frequency, odd's ratio and Hardy-Weinberg equilibrium were evaluated. SPSS (version 21.0) was used for the data analysis.

Results:

MTR A2756G genetic polymorphism was not associated with the risk of RM. The ancestral allele of MTRR A66G and the mutant allele of CBS 844INS68 was causing an increased risk of more than two folds for RM. CBS 844INS68 in combination with MTR A2756G was found to pose an increased risk of more than two folds for RM.

Conclusion:

Genetic polymorphisms particularly MTRR A66G and CBS 844INS68 seems to be elevating the risk and hence making women susceptible for RM.

Genetic markers for inherited thrombophilia related pregnancy loss and implantation failure in Indian population - implications for diagnosis and clinical management

AIM

The biology of recurrent pregnancy loss and recurrent implantation failure (RPL-RIF) is complex with multi-factorial etiology, with defective thrombosis being one of the most important and highly prevalent causes. The role of several thrombophilia related genes and variants associated with RPL-RIF is widely reported, and this study aimed to identify the risk associated with these genes in the Indian population.

METHODS

Next generation sequencing (NGS) was employed for the current study. NGS enables sequencing of multiple genes, identification of new variants, and establishment of genetic correlations with reproductive failure in diverse population groups. The present NGS based study evaluates association of twenty-nine genotypes of ten coagulation pathway genes (F2, F5, F13, MTR, MTRR, MTHFR, ANXA5, PROZ, SERPINE1 and VEGFA) with RPL-RIF in 540 female subjects - 474 patients with early recurrent pregnancy loss, late pregnancy loss, pregnancy complications in late gestation and recurrent implantation failure, with 66 controls.

RESULTS

The results emphasize inclusion of genotypes of seven thrombophilia genes (MTHFR, MTRR, MTR, ANXA5, PROZ, SERPINE1, VEGFA) for diagnosis of inherited thrombophilia risk for RPL-RIF in Indian population, as against the common practice of testing limited to F2, F5 and MTHFR genes.

CONCLUSION

Deriving risk magnitude from Combined Risk Analysis and interpretation of high-risk haplotypes are crucial components for evidence based personalized management such as selection of drugs and dosage, and prenatal or pre-implantation recommendations, for high-risk patients in fertility and obstetric clinics.

Disruption of Folate Metabolism Causes Poor Alignment and Spacing of Mouse Conceptuses for Multiple Generations

Abnormal uptake or metabolism of folate increases risk of human pregnancy complications, though the mechanism is unclear. Here, we explore how defective folate metabolism influences early development by analysing mice with the hypomorphic Mtrr^gt mutation. MTRR is necessary for methyl group utilisation from folate metabolism, and the Mtrr^gt allele disrupts this process. We show that the spectrum of phenotypes previously observed in Mtrr^gt/gt conceptuses at embryonic day (E) 10.5 is apparent from E8.5 including developmental delay, congenital malformations, and placental phenotypes. Notably, we report misalignment of some Mtrr^gt conceptuses within their implantation sites from E6.5. The degree of misorientation occurs across a continuum, with the most severe form visible upon gross dissection. Additionally, some Mtrr^gt/gt conceptuses display twinning. Therefore, we implicate folate metabolism in blastocyst orientation and spacing at implantation. Skewed growth likely influences embryo development since developmental delay and heart malformations (but not defects in neural tube closure or trophoblast differentiation) associate with severe misalignment of Mtrr^gt/gt conceptuses. Typically, the uterus is thought to guide conceptus orientation. To investigate a uterine effect of the Mtrr^gt allele, we manipulate the maternal Mtrr genotype. Misaligned conceptuses were observed in litters of Mtrr^+/+, Mtrr^+/gt, and Mtrr^gt/gt mothers. While progesterone and/or BMP2 signalling might be disrupted, normal decidual morphology, patterning, and blood perfusion are evident at E6.5 regardless of conceptus orientation. These observations argue against a post-implantation uterine defect as a cause of conceptus misalignment. Since litters of Mtrr^+/+ mothers display conceptus misalignment, a grandparental effect is explored. Multigenerational phenotype inheritance is characteristic of the Mtrr^gt model, though the mechanism remains unclear. Genetic pedigree analysis reveals that severe conceptus skewing associates with the Mtrr genotype of either maternal grandparent. Moreover, the presence of conceptus skewing after embryo transfer into a control uterus indicates that misalignment is independent of the peri- and/or post-implantation uterus and instead is likely attributed to an embryonic mechanism that is epigenetically inherited. Overall, our data indicates that abnormal folate metabolism influences conceptus orientation over multiple generations with implications for subsequent development. This study casts light on the complex role of folate metabolism during development beyond a direct maternal effect.

Folate metabolizing gene polymorphisms and genetic vulnerability to preterm birth in Korean women

BACKGROUND

The folate metabolism that converts homocysteine to methionine is closely related to the accumulation of homocysteine. Increased homocysteine levels lead to an impaired antithrombotic function of the vascular endothelium and uterine-placental circulation, resulting in abnormal pregnancy outcomes. Previous studies have reported that gene polymorphisms in folate metabolism are associated with the development of preterm birth (PTB) in various populations.

OBJECTIVE

we performed a case-control study to evaluate the association between five polymorphisms in folate metabolic genes (MTHFR, MTR, MTRR, TCN2) and PTB.

METHODS

In this study, a total of 254 subjects were analyzed (111 patients with PTB and 143 women at ≥ 38 weeks of gestation). Genotype and allele frequency differences between patients and control groups and the Hardy-Weinberg equilibrium were assessed using a Chi-square test. For evaluation indicators, odds ratios (ORs) of 95% confidence intervals (CI) were estimated. In addition, we analyzed the combined genotype frequencies of SNPs of folate-metabolizing genes to measure gene-gene interactions for PTB.

RESULTS

Our results showed that the MTR rs1805087 GG (p = 0.031), and TCN2 rs1801198 CG genotype (OR 0.53, 95% CI 0.288-0.980, p = 0.042) were significantly associated with PTB. The MTHFR rs4846049 AA showed a marginal trend toward significance (OR 0.15, 95% CI 0.018-1.205, p = 0.041). In particular, the combined genotypes, including MTHFR rs1537514 CC-MTRR rs1801394 GG, MTHFR rs1537514 CC-TCN2 rs1801198 CG, and MTR rs1805087 AA-TCN2 rs1801198 CG, have significant interactions with PTB (OR 0.49, 95% CI 0.248-0.992, p < 0.05).

CONCLUSION

The polymorphisms of folate metabolic genes may have a genetic association with the development of PTB in Korean women. A larger sample set and functional studies are required to further elucidate our findings.

Increased homocysteine mediated oxidative stress as key determinant of hepatitis E virus (HEV) infected pregnancy complication and outcome: A study from Northeast India

With the background of association of oxidative stress and Hepatitis E virus (HEV) infection in pregnancy complications the present novel study aimed to evaluate the significance of changes in maternal homocysteine levels and the related mechanism(s) in the pathophysiology of HEV related pregnancy complications and negative outcomes. Term delivery (TD, N = 194) and HEV-IgM positive pregnancy cases [N = 109] were enrolled. Serum and placental homocysteine levels were evaluated by ELISA and immunofluorescence and in turn correlated with serum Vitamin B12 levels. Distribution of variant MTHFR C➔T and TYMS1494del6bp genotyping were studied by PCR-RFLP. Differential folate receptor alpha (FR-α) expression in placenta was evaluated by real-time PCR and immunofluorescence respectively. The HEV viral load was significantly higher in both FHF and AVH cases. Higher serum homocysteine levels was associated with preterm delivery (PTD) and fetal death in HEV infected cases and was significantly inversely correlated with serum VitaminB12 levels in HEV cases. Placental homocysteine expression was upregulated in HEV cases, and in cases with negative pregnancy outcome. A Homocysteine level was associated with MTHFR C677T status. Genetic alterations in folate pathway was associated with increased risk of PTD in HEV infected pregnancy cases, disease severity, and negative pregnancy outcome in AVH and FHF groups. FR-α expression was downregulated in placental tissues of HEV infected pregnancy.Placental stress caused by HEV inflicted increased homocysteine due to alterations in maternal vitamin B12 levels and folate pathway components is detrimental mechanism in PTD and negative pregnancy outcome in HEV infected pregnancy cases and holds prognostic and therapeutic significance.

Association between gene polymorphism of folate metabolism and recurrent spontaneous abortion in Asia: A Meta-analysis

To evaluate the association between gene polymorphisms of MTHFR (C677T, A1298C) and MTRR (A66G), and the recurrent spontaneous abortion (RSA) risk in Asia.Related case-control studies were collected, selected, and screened. A meta-analysis was conducted by Stata 12.0 software to assess the association between polymorphisms of target genes and RSA.Altogether 30 studies examining the relationship between genetic polymorphism of folate metabolism and RSA risk were included, among which 20 studies were related to MTHFR C677T, 11 to MTHFR A1298C and 6 to MTRR A66G. The studies suggested that MTHFR C677T polymorphism was closely connected with RSA risk under all models (P < .05). Furthermore according to the subgroup analysis of ethnicity, the correlation between C677T polymorphism and RSA was stronger in north of China when compared with south of China and other Asian countries (P > . 05). For MTHFR A1298C, it was closely related to RSA risk in all gene models except for (AC vs AA) (P < .05). However, when it comes to MTRR A66G, there was no significant correlation between gene A66G polymorphism and RSA risk except for the additive gene model (G vs A) (P < .05).The present evidence shows that the correlation between gene polymorphisms and RSA risk can be found in MTHFR C677T, A1298C (except for heterozygote model) and MTRR A66G (only in additive genotypes), and the detection of the correlated gene polymorphisms mentioned above is of certain guiding significance for preventing RSA and screening high-risk groups.

Study of the Association Between microRNA (miR-25T>C, miR-32C>A, miR-125C>T, and miR-222G>T) Polymorphisms and the Risk of Recurrent Pregnancy Loss in Korean Women

Recurrent pregnancy loss (RPL), which is defined as two pregnancy losses that occur before 20 weeks of gestation, is relatively common, occurring in approximately 1–5% of women. The underlying cause is often unclear, although numerous factors may contribute to RPL, including environmental and immunological factors, blood coagulation disorders, and genetics. In particular, single nucleotide variants have been associated with RPL, including those found in microRNAs (miRNAs). We investigated the association between four miRNA polymorphisms, miR-25T>C, miR-32C>A, miR-125aC>T, and miR-222G>T, and RPL in a cohort consisting of 361 RPL patients and 272 controls. Subjects were genotyped at miRNA loci by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis, and genotype frequencies were calculated. We then performed allele and genotype combination analyses and measured the association between miRNA polymorphisms and clinical variables in both RPL patients and controls. We detected a statistically significant association between RPL and the miR-25T/miR-32C/miR-125aT/miR-222T allele combination (adjusted odds ratio (AOR), 4.361; 95% confidence interval (CI), 1.496–12.72; P = 0.003). Three-gene combinations, including miR-32C/miR-125aT/miR-222T (AOR, 3.085; 95% CI, 1.254–7.588; P = 0.010) and miR-25T/miR-125aT/miR-222T (AOR, 2.929; 95% CI, 1.183–7.257; P = 0.015), and the two-gene combination miR-125aT/miR-222T (AOR, 2.417; 95% CI, 1.084–5.386; P = 0.026) were also associated with RPL. Analysis of variance (ANOVA) revealed that platelet counts and blood urea nitrogen levels were significantly different in RPL patients expressing different miR-125aC>T and miR-25T>C genotypes, respectively (P < 0.05). In addition, creatinine levels were lower in RPL patients expressing the minor alleles miR-25T>C and miR-32C>A. We investigated miRNAs (miR-25, miR-32, miR-125a, miR-222) in RPL patients and healthy controls. Significantly different allele frequencies were detected by ANOVA. We suggest that miRNAs and clinical factors can impact RPL occurrence.

Investigation of the association of idiopathic male infertility with polymorphisms in the methionine synthase (MTR) gene

OBJECTIVE

Spermatogenesis is a complex process that is regulated by a number of genes, some of which are involved in folate-dependent 1-carbon metabolism. Methionine synthase (encoded by MTR) is a key enzyme participating in this pathway. This study aimed to investigate the relationship of the MTR 2756A > G polymorphism with idiopathic male fertility in the Iranian population.

METHODS

The participants of this study included 100 men with idiopathic infertility and 100 healthy men as the control group. Genotyping of MTR 2756A > G was performed using the polymerase chain reaction and restriction fragment length polymorphism technique. The obtained data were analyzed using SPSS ver. 20.0 with a level of confidence of p< 0.05.

RESULTS

The frequencies of the A and G alleles at this locus were 77% and 23% in infertile patients and 84% and 16% in the control group, respectively. The frequencies of the GG, GA, and AA genotypes were 5%, 36%, and 59% in the infertile patients versus 3%, 27%, and 70% in the control group, respectively. No significant difference was observed in any genetic models.

CONCLUSION

In general, the findings of this study suggest that the MTR 2756A > G single-nucleotide polymorphism is not a predisposing factor for idiopathic infertility in men.

Genetics of recurrent pregnancy loss among Iranian population

Background

Recurrent pregnancy loss (RPL) is one of the most common reproductive disorders which is defined as the occurrence of recurrent miscarriage before 24 weeks of gestation and is observed among 1%–5% of women.

Methods

Various factors are associated with RPL such as immunological disorders, maternal age, obesity, alcohol, chromosomal abnormality, endocrine disorders, and uterine abnormalities. About half of the RPL cases are related with chromosomal abnormalities. Therefore, RPL genetic tests are mainly limited to karyotyping. However, there is a significant proportion of RPL cases without any chromosomal abnormalities that can be related to the single‐gene aberrations. Therefore, it is required to prepare a diagnostic panel of genetic markers besides karyotyping.

Results

In the present review, we have summarized all the significant reported genes until now which are associated with RPL among Iranian women. We categorized all the reported genes based on their cellular and molecular functions in order to determine the molecular bases of RPL in this population.

Conclusion

This review paves the way of introducing a population‐based diagnostic panel of genetic markers for the first time among Iranian RPL cases. Moreover, this review clarifies the genetic and molecular bases of RPL in this population.

Associations of MTRR and TSER polymorphisms related to folate metabolism with susceptibility to metabolic syndrome

BACKGROUND

Hyperhomocysteinemia is a potential risk factor for the development of metabolic syndrome (MetS). Among genes involved in homocysteine metabolism, polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene are known to be associated with MetS incidence. However, effects of polymorphisms of other folate metabolism-related genes on MetS susceptibility are not well known yet.

OBJECTIVE

This study was to determine whether methionine synthase (MTR) 2756A > G, methionine synthase reductase (MTRR) 66A > G, and thymidylate synthase enhancer region (TSER) 2R/3R polymorphisms might be associated with risks of MetS development in the Korean population.

METHODS

Genotype analysis of the three polymorphisms was performed for a total of 483 subjects including 236 MetS patients and 247 unrelated healthy controls using polymerase chain reaction-restriction fragment length polymorphism technique.

RESULTS

The present study revealed that MTRR and TSER polymorphisms were associated with susceptibility to MetS. Several genotypes and allele combinations from the three polymorphisms were also related to the MetS prevalence. When polymorphism data were stratified according to the risk components of MetS, MTR polymorphism was significantly associated with an increased risk of MetS in subjects with systolic blood pressure < 132.7 mmHg (AOR 1.842, 95% CI 1.039-3.266, P = 0.037) and fasting blood glucose level < 106.3 mg/dL (AOR 1.772, 95% CI 1.069-2.937, P = 0.027). MTRR polymorphism was significantly associated with a decreased risk of MetS in subjects with triglyceride level < 216.3 mg/dL (AOR 0.616, 95% CI 0.399-0.951, P = 0.029). To the best of our knowledge, this is the first to provide reliable evidence about the association of other folate metabolism-related gene polymorphisms besides MTHFR with MetS susceptibility and its risk factors.

CONCLUSION

Results of this study suggest that MTRR and TSER polymorphisms might be potential genetic markers for the risk of MetS development in Korean population.

Association of methionine synthase (rs1805087), methionine synthase reductase (rs1801394), and methylenetetrahydrofolate dehydrogenase 1 (rs2236225) genetic polymorphisms with recurrent implantation failure

One-carbon metabolism, in which folate plays an essential role, is important for maintaining pregnancy and foetal development. Here, polymorphisms in three genes involved in the methylation of homocysteine were examined: methionine synthase (MTR), methionine synthase reductase (MTRR), and methylenetetrahydrofolate dehydrogenase 1 (MTHFD1), each of which is involved in methionine metabolism, a component of the one-carbon metabolism process. This involved a case-control study of 343 Korean women: 118 patients with RIF and 225 controls with at least one live birth and no history of pregnancy loss. The MTHFD1 1958GA genotype was observed less frequently than the MTHFD1 1958GG genotype (IF ≥ 4, p = 0.015) in women with RIF. In addition, the MTRR 66A > G polymorphism was associated with increased plasma homocysteine levels (p = 0.019). Based on these results, we propose that the MTRR 66A > G and MTHFD1 1958G > A polymorphisms are predisposing factors for RIF development. This study is the first to examine a potential association between the MTHFD1 and MTRR polymorphisms and RIF susceptibility in Korean patients.

Association study of the three functional polymorphisms (TAS2R46G>A, OR4C16G>A, and OR4X1A>T) with recurrent pregnancy loss

This study was purposed to investigate whether genetic polymorphisms in the function of stop-gain are associated with a fetal or placental development play roles and a development of idiopathic recurrent pregnancy loss (RPL) in Korean females. Three stop-gain polymorphisms were selected using next-generation sequencing screening, which allows for the rigorous examination and discovery of previously uncharacterized stop-gain genes and stop-gain expression profiles. Accordingly, we investigated the association of stop-gain polymorphisms in Korean women with RPL. Three functional polymorphisms in the TAS2R46G>A (rs2708381), OR4C16G>A (rs1459101), and OR4X1A>T (rs10838851) genes were genotyped using polymerase chain reaction (PCR)-restriction fragment length polymorphism assays and real-time PCR analysis. We determined that the OR4C16G>A polymorphism was associated with idiopathic RPL in Korean women (Adjusted odds ratio [AOR] 1.782; 95% confidence interval [CI] 1.004-3.163; P = 0.048, and AOR 1.766; 95% CI 1.020-3.059; P = 0.042). In addition, the prevalence of RPL was increased in women with the OR4C16GA + AA genotype and blood coagulation measures of prothrombin time (PT) > 10.4 s (AOR 8.292; 95% CI 2.744-25.054). We suggest that the OR4C16G>A polymorphism might serve as a clinically useful biomarker for the development, prevention, and prognosis of RPL.

Associative role of TYMS6bpdel polymorphism and resulting hyperhomocysteinemia in the pathogenesis of preterm delivery and associated complications: A study from Northeast India

Aberrations including genetic alterations in folate pathway are detrimental in multiple disease pathogenesis, including pregnancy. The present study is based on the screening of the associative role of TYMS 14946bp deletion(del) polymorphism and associated hyperhomocysteinemia in susceptibility to preterm delivery (PTD), which is strongly associated with neonatal mortality and morbidity.

METHODS

A total of 209 PTD cases {extremely preterm (n=22), very preterm (n=43) and moderately preterm (n=144)} and 194 term delivery cases were evaluated for TYMS 14946bp deletion and its association with preterm delivery, pregnancy outcome, baby birth weight and homocysteine estimation.

RESULTS

The results showed that the distribution of TYMS 14946bp del/del genotype significantly increased the risk of PTD [OR=2.801, p=0.002] and is associated with fetal death. The TYMS 6bp ins/del and 6bp del/del genotype was associated with low birth weight (LBW) compared to 6bp ins/ins genotype in both term and PTD groups, and in case of very (p=0.024) and moderately (p=0.045) sub-cohorts of PTD significantly. Elevated serum homocysteine levels were significantly associated with PTD (p<0.001) and fetal death (p=0.013); and was also found to significantly correlate with TYMS 14946bp del/del genotype in all the pregnancy cases (p=0.008). TYMS 6bp del/del genotype was associated with higher homocysteine levels compared to ins/ins (p=0.005) and ins/del (p=0.062) genotypes within the PTD group.

CONCLUSION

The study provides crucial information regarding the importance of TYMS6bpdel/del genotype and associated hyperhomocysteinemia in susceptibility to PTD, fetal death and LBW; and thus indicating their prognostic significance of TYMS 6bp del/del genotype in PTD which is of clinical importance.

Genetic Variation of Methylenetetrahydrofolate Reductase (MTHFR) and Thymidylate Synthase (TS) Genes Is Associated with Idiopathic Recurrent Implantation Failure

The one-carbon metabolism pathway disorder was important role in successful pregnancy. The MTHFR and TS protein were crucial factor in one-carbon metabolism. To investigate the association between recurrent implantation failure (RIF) and enzymes in the one-carbon metabolism pathway. A total of 120 women diagnosed with RIF and 125 control subjects were genotyped for MTHFR 677C>T, 1298A>C, TSER 2R/3R and TS 1494del/ins by a polymerase chain reaction-restriction fragment length polymorphism assay. According to the gene-gene combination analysis, the MTHFR 677/MTHFR 1298 (TT/AA) and MTHFR 677/TS 1494 (TT/6bp6bp) genetic combinations were associated with relatively higher risks [adjusted odds ratio (AOR), 2.764; 95% CI, 1.065–7.174; P = 0.037 and AOR, 3.186; 95% CI, 1.241–8.178; P = 0.016] in RIF patients compared to the CC/AA (MTHFR 677/MTHFR 1298) and TT/6bp6bp (MTHFR 677/TS 1494) combinations, respectively. The results suggested that the combined MTHFR 677/MTHFR 1298 genotype might be associated with increased risk of RIF. To the best of our knowledge, this study is the first to elucidate the potential association of MTHFR, TS and TSER polymorphisms with RIF risk in Korean patients.

An Association Study of the SLC19A1 Gene Polymorphisms/Haplotypes with Idiopathic Recurrent Pregnancy Loss in an Iranian Population

AIMS

The genetics of folate metabolism is one of the most significant mechanisms influencing fetal growth and may underlie some cases of unexplained recurrent miscarriage. Reduced folate carrier 1, encoded by the SLC19A1 gene, is a transporter of folate. Folate deficiency and elevated levels of homocysteine could be disadvantageous for the female reproductive system health. Thus, the balance between homocysteine and folate status can be used to measure the risk of recurrent pregnancy loss.

METHODS

The purpose of this study was to determine the association between -43T>C, 80G>A, and 696C>T polymorphisms of the SLC19A1 gene in 147 women who had unexplained recurrent miscarriage in comparison with 150 healthy women. Amplification refractory mutation system-polymerase chain reaction was used to genotype the molecular polymorphisms of this gene.

RESULTS

The results indicated that the -43T>C single nucleotide of the SLC19A1 gene was significantly associated with a risk of recurrent miscarriage in Iranian women (p < 0.05). No significant association was observed for the other two polymorphisms. The haplotype frequency distribution of -43C/80G/696C, -;43C/80G/696T, -43C/80G, and 80G/696T was significantly different in patients than controls, which may represent a novel risk factor for idiopathic recurrent pregnancy loss.

CONCLUSIONS

Polymorphisms and haplotypes of the SLC19A1 gene can be considered risk factors for idiopathic recurrent pregnancy loss.

Altered folate metabolism modifies cell proliferation and progesterone secretion in human placental choriocarcinoma JEG-3 cells

Folate is an essential B vitamin required for de novo purine and thymidylate synthesis, and for the remethylation of homocysteine to form methionine. Folate deficiency has been associated with placenta-related pregnancy complications, as have SNP in genes of the folate-dependent enzymes, methionine synthase (MTR) and methylenetetrahydrofolate dehydrogenase 1 (MTHFD1). We aimed to determine the effect of altered folate metabolism on placental cell proliferation, viability and invasive capacity and on progesterone and human chorionic gonadotropin (hCG) secretion. Human placental choriocarcinoma (JEG-3) cells cultured in low folic acid (FA) (2 nM) demonstrated 13% (P<0.001) and 26% (P<0.001) lower proliferation, 5.5% (P=0.025) and 7.5% (P=0.004) lower invasion capacity, and 5 to 7.5% (P=0.004-0.025) lower viability compared with control (20 nM) or supplemented (100 nM) cells, respectively. FA concentration had no effect on progesterone or hCG secretion. Small interfering RNA (siRNA) knockdown of MTR gene and protein expression resulted in 17.7% (P<0.0001) lower proliferation and 61% (P=0.014) higher progesterone secretion, but had no effect on cell invasion and hCG secretion. siRNA knockdown of MTHFD1 gene expression in the absence of detectable changes in protein expression resulted in 10.3% (P=0.001) lower cell proliferation, but had no effect on cell invasion and progesterone or hCG secretion. Our data indicate that impaired folate metabolism can result in lower trophoblast proliferation, and could alter viability, invasion capacity and progesterone secretion, which may explain in part the observed associations between folate and placenta-related complications.

Localization of folate metabolic enzymes, methionine synthase and 5,10-methylenetetrahydrofolate reductase in human placenta

BACKGROUND

Normal fetal development requires adequate folate levels during pregnancy. Although folate metabolic enzymes have important roles in the maintenance of normal fetal development, the location of folate metabolic enzymes, methionine synthase (MTR) and 5,10-methylenetetrahydrofolate reductase (MTHFR), has not been previously examined.

METHODS

We investigated the expression of MTR and MTHFR in human term placenta obtained from normal and pregnancy-induced hypertension (PIH) patients.

RESULTS

MTR is expressed in the villous syncytiotrophoblast and MTHFR is expressed in the extravillous trophoblast. There was no difference in the quantity and location of these enzymes between control and PIH patients.

CONCLUSION

These results suggest that MTR in the villous trophoblast participates in the metabolism of homocysteine by using folate, and MTHFR in the extravillous trophoblast is associated with extratrophoblast invasion.

Genetic variants in microRNA machinery genes are associated [corrected] with idiopathic recurrent pregnancy loss risk

Objective

Key molecules involved in microRNA (miRNA) biogenesis, such as DROSHA, XPO5, and DICER, have been identified in trophoblast cells, confirming that the miRNA biogenesis pathway is active in human placenta. In addition, miRNAs regulate uterine gene expression associated with inflammatory responses during the peri-implantation period and participate in maternal-fetal immune tolerance. The purpose of this study was to demonstrate whether genetic polymorphisms in miRNA machinery genes show an association with idiopathic recurrent pregnancy loss (RPL) in Korean women.

Study design

We performed a case-control study with 238 controls and 338 women who had experienced at least two consecutive pregnancy losses between 1999 and 2010. Genotypes of miRNA machinery genes, including DICER rs3742330, DROSHA rs10719, RAN GTPase (RAN) rs14035, and exportin-5 (XPO5) rs11077 were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. The logistic odds ratios (ORs) of RPL were estimated with a 95% confidence interval (CI) in multivariate analysis after maternal age adjustment. Gene-gene interactions among the loci of the four gene polymorphisms were evaluated using the multifactor dimensionality reduction (MDR) method.

Results

The RAN rs14035 CC genotype and DICER rs3742330/DROSHA rs10719 GG/TC+CC, rs3742330/RAN rs14035 GG/CC, and DICER rs3742330/XPO5 rs11077 GG/AC+CC combinations were significantly associated with increased RPL risk, whereas the RAN rs14035 CT, DICER rs3742330/RAN rs14035 AA+AG/CT+TT, DROSHA rs10719/RAN rs14035 TC+CC/CT+TT, and RAN rs14035/XPO5 rs11077 CT+TT/AA combinations reduced RPL risk. The A-T-T-C and G-C-T-A allele combinations (DICER/DROSHA/RAN/XPO5) were 20 times more frequent in the RPL group than in the control group.

Conclusion

Our study demonstrates the relationship between RPL development and the polymorphism of the miRNA machinery gene RAN and combined genotype of DROSHA/DICER.

The association of idiopathic recurrent early pregnancy loss with polymorphisms in folic acid metabolism-related genes

The aim of this study was to investigate the association between polymorphisms in folic acid metabolism-related genes and idiopathic recurrent early pregnancy loss (REPL). A prospective case-control study was performed on a cohort of 82 REPL patients and 166 healthy controls. Genotyping of methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C was assessed by applying polymerase chain reaction for amplification followed by DNA sequencing, for methionine synthase reductase A66G, solute carrier family 19, member 1 (SLC19A1) G80A and C696T, and genotyping was done by utilizing the Sequenom MassARRAY system. The results revealed a significant association between MTHFR A1298C polymorphism and idiopathic REPL. Haplotype analysis indicated that the MTHFR 677C-MTHFR 1298C allele combination was associated with REPL (P < 0.001). The MTHFR 677C-MTHFR 1298A and SLC19A1 80G-SLC19A1 696C allele combinations had lower frequencies in patients with REPL, but with P > 0.05 (P = 0.093 and P = 0.084, respectively).