No mitochondrial DNA deletions but more D-loop point mutations in repeated pregnancy loss

Cytochrome c oxidase IV isoform 1 (COX4-1) regulates the proliferation, migration and invasion of trophoblast cells via modulating mitochondrial function

INTRODUCTION

Spontaneous miscarriage is a common complication of early pregnancy. Previous studies have shown that mitochondrial function plays an important role in establishment of a successful pregnancy. Cytochrome c oxidase subunit 4 isoform 1 (COX4I1), a component of electron transport chain complex Ⅳ, is required for coupling the rate of ATP production to energetic requirements. However, there is very limited research on its role in trophoblast biology and how its dysfunction may contribute to spontaneous miscarriage.

METHODS

Placental villi (7-10 weeks gestational age) collected from either induced termination of pregnancy or after spontaneous miscarriage were examined for expression of COX4I1. COX4I1 was knocked down by siRNA transfection of primary isolates of EVT cells. Real-time cell analysis (RTCA) and 5-Ethynyl-2'-deoxyuridine (EdU) were used to detect changes in proliferation ability after COX4I1 knockdown of EVT cells. Migration and invasion indices were determined by RTCA. Mitochondrial morphology was observed via MitoTracker staining. Oxidative phosphorylation, ATP production, and glycolysis in COX4I1-deficient cells and controls were assessed by a cellular energy metabolism analyzer (Seahorse).

RESULTS

In placental villous tissue, COX4I1 expression was significantly decreased in the spontaneous miscarriage group. Knockdown of COX4I1 inhibited EVT cell proliferation, increased the migration and invasion ability and mitochondrial fusion of EVT cells. Mitochondrial respiration and glycolysis were impaired in COX4I1-deficient EVT cells. Knockdown of MMP1 could rescue the increased migration and invasion induced by COX4I1 silencing.

DISCUSSION

Low expression of COX4I1 leads to mitochondrial dysfunction in EVT, resulting in altered trophoblast function, and ultimately to pregnancy loss.

Variations in mitochondrial DNA coding and D-loop region are associated with early embryonic development defects in infertile women

Mitochondrial DNA (mtDNA) plays a critical role in oocyte maturation, fertilization, and early embryonic development. Defects in mtDNA may determine the alteration of the mitochondrial function, affecting cellular oxidative phosphorylation and ATP supply, leading to impaired oocyte maturation, abnormal fertilization, and low embryonic developmental potential, ultimately leading to female infertility. This case-control study was established to investigate the correlation between mtDNA variations and early embryonic development defects. Peripheral blood was collected for next-generation sequencing from women who suffered the repeated failures of in vitro fertilization (IVF) and/or intracytoplasmic sperm injection (ICSI) cycles due to early embryonic development defects as well as in-house healthy controls, and the sequencing results were statistically analyzed for all subjects. This study found that infertile women with early embryonic development defects carried more mtDNA variants, especially in the D-loop region, ATP6 gene, and CYTB gene. By univariate logistic regression analysis, 16 mtDNA variants were associated with an increased risk of early embryonic development defects (OR > 1, p < 0.05). Furthermore, we identified 16 potentially pathogenic mtDNA variants only in infertile cases. The data proved that mtDNA variations were associated with early embryonic development defects in infertile Chinese women.

Genetics of Oocyte Maturation Defects and Early Embryo Development Arrest

Various pathogenic factors can lead to oogenesis failure and seriously affect both female reproductive health and fertility. Genetic factors play an important role in folliculogenesis and oocyte maturation but still need to be clarified. Oocyte maturation is a well-organized complex process, regulated by a large number of genes. Pathogenic variants in these genes as well as aneuploidy, defects in mitochondrial genome, and other genetic and epigenetic factors can result in unexplained infertility, early pregnancy loss, and recurrent failures of IVF/ICSI programs due to poor ovarian response to stimulation, oocyte maturation arrest, poor gamete quality, fertilization failure, or early embryonic developmental arrest. In this paper, we review the main genes, as well as provide a description of the defects in the mitochondrial genome, associated with female infertility.

Mitochondrial DNA Copy Number in Cleavage Stage Human Embryos-Impact on Infertility Outcome

A retrospective case control study was undertaken at the molecular biology department of a private center for reproductive medicine in order to determine whether any correlation exists between mitochondrial DNA (mtDNA) content of cleavage-stage preimplantation embryos and their developmental potential. A total of 69 couples underwent IVF treatment (averaged women age: 36.5, SD 4.9) and produced a total of 314 embryos. A single blastomere was biopsied from each embryo at the cleavage stage (day-3 post-fertilization) subjected to low-pass next generation sequencing (NGS), for the purpose of detecting aneuploidy. For each sample, the number of mtDNA reads obtained after analysis using NGS was divided by the number of reads attributable to the nuclear genome. The mtDNA copy number amount was found to be higher in aneuploid embryos than in those that were euploid (mean mtDNA ratio ± SD: 6.3 ± 7.5 versus 7.1 ± 5.8, p < 0.004; U Mann−Whitney test), whereas no statistically significant differences in mtDNA content were seen in relation to embryo morphology (6.6 ± 4.8 vs. 8.5 ± 13.6, p 0.09), sex (6.6 ± 4.1 vs. 6.2 ± 6.8, p 0.16), maternal age (6.9 ± 7.8 vs. 6.7 ± 4.5, p 0.14) or its ability to implant (7.4 ± 6.6 vs. 5.1 ± 4.6, p 0.18). The mtDNA content cannot serve as a useful biomarker at this point in development. However, further studies investigating both quantitative and qualitative aspects of mtDNA are still required to fully evaluate the relationship between mitochondrial DNA and human reproduction.

Mitochondrial DNA in Fresh versus Frozen Embryo Culture Media of Polycystic Ovarian Syndrome Patients Undergoing Invitro Fertilization: A Possible Predictive Marker of a Successful Pregnancy

Purpose

Frozen embryos transfer (ET) may improve the live-birth and reduce rates of ovarian hyperstimulation in polycystic ovary syndrome (PCOS) patients. Morphological criteria are the classical way for embryo selection, yet recently, many biochemical and genetic markers have been developed. This study aimed to compare fresh and frozen ET using the mtDNA/gDNA ratio of embryo secretome and the possibility of using this ratio as a predictive marker of PCOS pregnancy rate.

Subjects and Methods

One hundred PCOS patients undergoing IVF were chosen according to Rotterdam criteria and divided into two groups. Group I (50 with fresh ET), group II (50 with frozen ET), and otherwise 33 apparently healthy women as a control group with fresh ET. We then carried out absolute quantification of embryo culture media mtDNA and gDNA by real-time PCR.

Results

mtDNA/gDNA ratio was significantly low in PCOS embryo culture media in comparison with control. Additionally, while the mtDNA/gDNA ratio was significantly high in pregnant PCOS embryo culture media, it was high, though not statistically significant, in the fresh ET than frozen ET group. mtDNA/gDNA ratio sensitivity and specificity in PCOS embryo culture media as a predictive value of pregnancy rate were (86% and 96%, respectively).

Conclusion

mtDNA/gDNA ratio measurement in PCOS embryo culture media is a novel marker that can be clinically applied as a predictive value of the quality of the morphologically good embryo.

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Deep sequencing shows that accumulation of potentially pathogenic mtDNA mutations rather than mtDNA copy numbers may be associated with early embryonic loss

PURPOSE

To explore the relationship between mitochondrial DNA quantity and heteroplasmy and early embryonic loss.

METHODS

A total of 150 villous samples from patients with spontaneous abortion (SA, n = 75) or induced abortion (IA, n = 75) were collected. qPCR and next-generation sequencing (NGS) were used to test mitochondrial DNA quantity and heteroplasmy. Missense mutations with a CADD score > 15 and heteroplasmy ≥ 70% were defined as potentially pathogenic mutations.

RESULTS

With respect to mitochondrial DNA copy numbers, there was no significant difference between the SA and IA groups (median (IQR), 566 (397-791) vs. 614 (457-739); P = 0.768) or between the euploid and aneuploid groups (median (IQR), 516 (345-730) vs. 599 (423-839); P = 0.107). mtDNA copy numbers were not associated with spontaneous abortion using logistic regression analysis (P = 0.196, 95% CI 1.000-1.001). In addition, more patients harbored possibly pathogenic mtDNA mutations in their chorionic villi in the SA group (70.7%, 53/75) compared with the IA group (54.7%, 41/75; P < 0.05). However, there was no statistical difference between the euploid (80%, 24/30) and aneuploid groups (64.4%, 29/45; p = 0.147).

CONCLUSION

Early embryonic loss and the formation of aneuploidy were not related to mtDNA copy number. Patients with spontaneous abortion were more likely to have possibly pathogenic mutations in their mtDNA, and this may assist in purifying pathogenic mtDNA. However, whether the accumulation of these potentially morbific mtDNA mutations caused early embryonic loss requires further investigation.

Placental mitochondrial DNA mutations and copy numbers in intrauterine growth restricted (IUGR) pregnancy

Intrauterine Growth Restriction (IUGR) is a common and significant complication that arises during pregnancy wherein the fetus fails to attain its full growth potential. Mitochondria being one of the primary sources of energy, plays an important role in placentation and fetal development. In IUGR pregnancy, increased oxidative stress due to inadequate oxygen and nutrient supply could possibly alter mitochondrial functions and homeostasis. In this study, we evaluated the biochemical and molecular changes in mitochondria as biosignature for early and better characterization of IUGR pregnancies. We identified significant increase in mtDNA copy number in both IUGR (p = 0.0001) and Small for Gestational Age (SGA) but healthy (p = 0.0005) placental samples when compared to control. Whole mitochondrial genome sequencing identified novel mutations in both coding and non-coding regions of mtDNA in multiple IUGR placental samples. Sirtuin-3 (Sirt3) protein expression was significantly downregulated (p = 0.027) in IUGR placenta but there was no significant difference in Nrf1 expression in IUGR when compared to control group. Our study provides an evidence for altered mitochondrial homeostasis and paves a way towards interrogating mitochondrial abnormalities in IUGR pregnancies.

Deleterious mtDNA mutations are common in mature oocytes

Heritable mitochondrial DNA (mtDNA) mutations are common, yet only a few recurring pathogenic mtDNA variants account for the majority of known familial cases in humans. Purifying selection in the female germline is thought to be responsible for the elimination of most harmful mtDNA mutations during oogenesis. Here we show that deleterious mtDNA mutations are abundant in ovulated mature mouse oocytes and preimplantation embryos recovered from PolG mutator females but not in their live offspring. This implies that purifying selection acts not in the maternal germline per se, but during post-implantation development. We further show that oocyte mtDNA mutations can be captured and stably maintained in embryonic stem cells and then reintroduced into chimeras, thereby allowing examination of the effects of specific mutations on fetal and postnatal development.

Mitochondrial Polymorphisms, in The D-Loop Area, Are Associated with Brain Tumors

Objective

This study was carried out to evaluate the relationship between mtDNA D-loop variations and the pathogenesis of a brain tumor.

Materials and Methods

In this experimental study, 25 specimens of brain tumor tissue with their adjacent tissues from patients and 454 blood samples from different ethnic groups of the Iranian population, as the control group, were analysed by the polymerase chain reaction (PCR)-sequencing method.

Results

Thirty-six variations of the D-loop area were observed in brain tumor tissues as well as the adjacent normal tissues. A significant difference of A750G (P=0.046), T15936C (P=0.013), C15884G (P=0.013), C16069T (P=0.049), T16126C (P=0.006), C16186T (P=0.022), T16189C (P=0.041), C16193T (P=0.045), C16223T (P=0.001), T16224C (P=0.013), C16234T (P=0.013), G16274A (P=0.009), T16311C (P=0.038), C16327T (P=0.045), C16355T (P=0.003), T16362C (P=0.006), G16384A (P=0.042), G16392A (P=0.013), G16394A (P=0.013), and G16477A (P=0.013) variants was found between the patients and the controls.

Conclusion

The results indicated individuals with C16069T [odds ratio (OR): 2.048], T16126C (OR: 2.226), C16186T (OR: 3.586), G16274A (OR: 4.831), C16355T (OR: 7.322), and T16362C (OR: 6.682) variants with an OR more than one are probably associated with a brain tumor. However, given the multifactorial nature of cancer, more investigation needs to be done to confirm this association.

Potential genetic causes of miscarriage in euploid pregnancies: a systematic review

BACKGROUND

Approximately 50% of pregnancy losses are caused by chromosomal abnormalities, such as aneuploidy. The remainder has an apparent euploid karyotype, but it is plausible that there are cases of pregnancy loss with other genetic aberrations that are not currently routinely detected. Studies investigating the use of exome sequencing and chromosomal microarrays in structurally abnormal pregnancies and developmental disorders have demonstrated their clinical application and/or potential utility in these groups of patients. Similarly, there have been several studies that have sought to identify genes that are potentially causative of, or associated with, spontaneous pregnancy loss, but the evidence has not yet been synthesized.

OBJECTIVE AND RATIONALE

The objective was to identify studies that have recorded monogenic genetic contributions to pregnancy loss in euploid pregnancies, establish evidence for genetic causes of pregnancy loss, identify the limitations of current evidence, and make recommendations for future studies. This evidence is important in considering additional research into Mendelian causes of pregnancy loss and appropriate genetic investigations for couples experiencing recurrent pregnancy loss.

SEARCH METHODS

A systematic review was conducted in MEDLINE (1946 to May 2018) and Embase (1974 to May 2018). The search terms ‘spontaneous abortion’, ‘miscarriage’, ‘pregnancy loss’, or ‘lethal’ were used to identify pregnancy loss terms. These were combined with search terms to identify the genetic contribution including ‘exome’, ‘human genome’, ‘sequencing analysis’, ‘sequencing’, ‘copy number variation’, ‘single-nucleotide polymorphism’, ‘microarray analysis’, and ‘comparative genomic hybridization’. Studies were limited to pregnancy loss up to 20 weeks in humans and excluded if the genetic content included genes that are not lethal in utero, PGD studies, infertility studies, expression studies, aneuploidy with no recurrence risk, methodologies where there is no clinical relevance, and complex genetic studies. The quality of the studies was assessed using a modified version of the Newcastle–Ottawa scale.

OUTCOMES

A total of 50 studies were identified and categorized into three themes: whole-exome sequencing studies; copy number variation studies; and other studies related to pregnancy loss including recurrent molar pregnancies, epigenetics, and mitochondrial DNA aberrations. Putatively causative variants were found in a range of genes, including CHRNA1 (cholinergic receptor, nicotinic, alpha polypeptide 1), DYNC2H1 (dynein, cytoplasmic 2, heavy chain 1), and RYR1 (ryanodine receptor 1), which were identified in multiple studies. Copy number variants were also identified to have a causal or associated link with recurrent miscarriage.

WIDER IMPLICATIONS

Identification of genes that are causative of or predisposing to pregnancy loss will be of significant individual patient impact with respect to counselling and treatment. In addition, knowledge of specific genes that contribute to pregnancy loss could also be of importance in designing a diagnostic sequencing panel for patients with recurrent pregnancy loss and also in understanding the biological pathways that can cause pregnancy loss.

Assessing ICSI outcome by combining non-invasive indicators: Early time-lapse morphokinetics and apoptosis in associated cumulus cells among women with the polycystic ovarian syndrome

Cumulus cells features and embryo developmental events can be considered as noninvasive indicators for embryo selection and clinical outcomes. A combination of time-lapse morphokinetic parameters and cumulus cell apoptosis in women with polycystic ovarian syndrome (PCOS) was evaluated for predicting pregnancy outcome. We assessed a total of 547 embryos from 100 intracytoplasmic sperm injection (ICSI) cycles. Time-lapse records were interpreted in time to pronuclear fading (tPNf), time to 2 to 8 cells (t2-t8), direct cleavage, reverse cleavage, and also for the presence of multinucleation. Percentages of apoptosis were identified in 100 associated cumulus cell samples using the TDT-mediated dUTP-biotin nick end-labeling assay. The significant decrease of apoptotic cumulus cells was detected in patients with chemical and clinical pregnancies as well as live birth among patients PCOS and in the tubal infertility group (p > 0.05). Furthermore, significantly higher implantation rate and also significantly lower cases of early pregnancy loss were observed in the group of oocytes with less apoptotic cumulus cells. Multivariate logistic regression analysis showed that tPNf together with cumulus cell apoptosis were independent prognostic factors of chemical pregnancy, clinical pregnancy rate, and live birth. Time-lapse embryo parameters may not reflect the cumulus cell apoptosis rate. However, the rate of apoptotic cumulus cells is significantly associated with ICSI outcome using Day 3 embryo transfer.

Association of genetic variations in the mitochondrial DNA control region with presbycusis

Background

The prominent role of mitochondria in the generation of reactive oxygen species, cell death, and energy production contributes to the importance of this organelle in the intracellular mechanism underlying the progression of the common sensory disorder of the elderly, presbycusis. Reduced mitochondrial DNA (mtDNA) gene expression and coding region variation have frequently been reported as being associated with the development of presbycusis. The mtDNA control region regulates gene expression and replication of the genome of this organelle. To comprehensively understand of the role of mitochondria in the progression of presbycusis, we compared variations in the mtDNA control region between subjects with presbycusis and controls.

Methods

A total of 58 presbycusis patients and 220 control subjects were enrolled in the study after examination by the otolaryngologist and audiology tests. Variations in the mtDNA control region were investigated by polymerase chain reaction and Sanger sequencing.

Results

A total of 113 sequence variants were observed in mtDNA, and variants were detected in 100% of patients, with 84% located in hypervariable regions. The frequencies of the variants, 16,223 C>T, 16,311 T>C, 16,249 T>C, and 15,954 A>C, were significantly different between presbycusis and control subjects.

Conclusion

The statistically significant difference in the frequencies of four nucleotide variants in the mtDNA control region of presbycusis patients and controls is in agreement with previous experimental evidence and supports the role of mitochondria in the intracellular mechanism underlying presbycusis development. Moreover, these variants have potential as diagnostic markers for individuals at a high risk of developing presbycusis. The data also suggest the possible presence of changes in the mtDNA control region in presbycusis, which could alter regulatory factor binding sites and influence mtDNA gene expression and copy number.

A Review on Various Uses of N-Acetyl Cysteine

N-acetyl cysteine (NAC), as a nutritional supplement, is a greatly applied antioxidant in vivo and in vitro. NAC is a precursor of L-cysteine that results in glutathione elevation biosynthesis. It acts directly as a scavenger of free radicals, especially oxygen radicals. NAC is a powerful antioxidant. It is also recommended as a potential treatment option for different disorders resulted from generation of free oxygen radicals. Additionally, it is a protected and endured mucolytic drug that mellows tenacious mucous discharges. It has been used for treatment of various diseases in a direct action or in a combination with some other medications. This paper presents a review on various applications of NAC in treatment of several diseases.

Mitochondrial Copy Number and D-Loop Variants in Pompe Patients

Objective

Pompe disease is a rare neuromuscular genetic disorder and is classified into two forms of early and late-onset. Over the past two decades, mitochondrial abnor- malities have been recognized as an important contributor to an array of neuromuscular diseases. We therefore aimed to compare mitochondrial copy number and mitochondrial displacement-loop sequence variation in infantile and adult Pompe patients.

Materials and Methods

In this retrospective study, the mitochondrial D-loop sequence was analyzed by polymerase chain reaction (PCR) and direct sequencing to detect pos- sible variation in 28 Pompe patients (17 infants and 11 adults). Results were compared with 100 healthy controls and sequences of all individuals were compared with the Cam- bridge reference sequence. Real-time PCR was used to quantify mitochondrial DNA copy number.

Results

Among 59 variants identified, 37(62.71%) were present in the infant group, 14(23.333%) in the adult group and 8(13.333%) in both groups. Mitochondrial copy number in infant patients was lower than adults (P<0.05). A significant frequency differ- ence was seen between the two groups for 12 single nucleotide polymorphism (SNP). A novel insertion (317-318 ins CCC) was observed in patients and six SNPs were iden- tified as neutral variants in controls. There was an inverse association between mito- chondrial copy number and D-loop variant number (r=0.54).

Conclusion

The 317-318 ins CCC was detected as a new mitochondrial variant in Pompe patients.

Effects of ovarian hyperstimulation on mitochondria in oocytes and early embryos

A mouse model was used to compare the number and function of mitochondria in oocytes and embryos obtained by superovulation and in a natural cycle (control group). The superovulation group had a higher number of total oocytes, MII oocytes, embryos with two pronuclei, 2-cell embryos and blastocysts than the control group (P<0.05 for all). The superovulation group had high proportion of MII oocytes with low number of mitochondrial (mt) DNA copies. The average number of mtDNA copies, ATP level and mitochondrial membrane potential ( Collapse

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Association of genetic variations in the mitochondrial D-loop with β-thalassemia

Beta-thalassemia, one of the most common single-gene disorders, is the result of reduced or absent production of β-globin chains. Patients with β-thalassemia show weak genotype-phenotype correlations. Mitochondrial DNA polymorphisms are a potential source for different physiological and pathological characteristics and have been found to be associated as genetic modifiers with various pathophysiologies, including cancers and neurodegenerative diseases. A group of 35 patients with β-thalassemia was investigated for the presence of mtDNA D-loop polymorphisms in comparison with 504 normal controls. We found four mtDNA D-loop polymorphisms at nucleotides 16,069C > T, 16,189T > C, 16,319G > A, and 16,519T > C that showed significant differences between patients and normal subjects. There is no strong proof for the association of these polymorphisms with β-thalassemia. It is hypothesized that iron overload or its effects on sequestration of calcium or zinc can lead to oxidative stress and ROS production inside the mitochondria. Therefore, possible accompanying of mtDNA polymorphisms with β-thalassemia disease may complicate the genotype-phenotype correlation and could affect the clinical outcomes in the patients.

The mitochondrial C16069T polymorphism, not mitochondrial D310 (D-loop) mononucleotide sequence variations, is associated with bladder cancer

Background

Bladder cancer is a relatively common and potentially life-threatening neoplasm that ranks ninth in terms of worldwide cancer incidence. The aim of this study was to determine deletions and sequence variations in the mitochondrial displacement loop (D-loop) region from the blood specimens and tumoral tissues of patients with bladder cancer, compared to adjacent non-tumoral tissues.

Methods

The DNA from blood, tumoral tissues and adjacent non-tumoral tissues of twenty-six patients with bladder cancer and DNA from blood of 504 healthy controls from different ethnicities were investigated to determine sequence variation in the mitochondrial D-loop region using multiplex polymerase chain reaction (PCR), DNA sequencing and southern blotting analysis.

Results

From a total of 110 variations, 48 were reported as new mutations. No deletions were detected in tumoral tissues, adjacent non-tumoral tissues and blood samples from patients. Although the polymorphisms at loci 16189, 16261 and 16311 were not significantly correlated with bladder cancer, the C16069T variation was significantly present in patient samples compared to control samples (p < 0.05). Interestingly, there was no significant difference (p > 0.05) of C variations, including C7TC6, C8TC6, C9TC6 and C10TC6, in D310 mitochondrial DNA between patients and control samples.

Conclusion

Our study suggests that 16069 mitochondrial DNA D-Loop mutations may play a significant role in the etiology of bladder cancer and facilitate the definition of carcinogenesis-related mutations in human cancer.

Low expression of Mfn2 is associated with mitochondrial damage and apoptosis in the placental villi of early unexplained miscarriage

INTRODUCTION

Early miscarriage is the most common complication of pregnancy and in many cases the etiology is not clearly understood. We aim to profile the expression of Mfn2 and mitochondrial damage in villous tissues, in order to determine the underlying mechanism of unexplained miscarriage.

METHODS

We investigated placental villous samples of 30 women with early unexplained miscarriage (miscarriage group) and 30 women with normal pregnancy (control group). Immunohistochemistry and western blotting were used to detect the Mfn2 expression. We observed trophoblastic cell apoptosis with TUNEL and analyzed Bcl-2 and Bax levels by western blotting. Transmission electron microscopy was used to analyze mitochondrial morphology and phosphomolybdic acid colorimetric method was used to measure the ATP content of all villous samples.

RESULTS

Mfn2 staining showed extra-nuclear localization in the trophoblastic cells. Compared with the control group, the levels of Mfn2 and Bcl-2 were markedly decreased (P < 0.01), while both the levels of Bax protein and apoptosis index (AI) were increased in the miscarriage group (P < 0.01). Mfn2 levels positively correlated with Bcl-2, but negatively correlated with Bax. Moreover, compared to the control group (33.8 ± 6.5 μmol/g), ATP levels in the miscarriage group were significantly decreased (15.8 ± 4.8 μmol/g). In addition, obvious impairment of mitochondrial function was observed in trophoblastic cells from the unexplained miscarriage group.

CONCLUSION

Mitochondrial morphologic and functional changes were observed in trophoblastic cells, and in relation with apoptosis, may be correlated with low levels of Mfn2. Deficient expression of Mfn2 in trophoblastic cells could be an important cause of early miscarriage.

T4216C mutation in NADH dehydrogenase I gene is associated with recurrent pregnancy loss

Several genetic factors are involved with recurrent pregnancy loss (RPL). However, few attempts have been made to associate mitochondrial DNA (mtDNA) variations with RPL. Therefore, we investigated the possible effect of the T4216C mutation in the mitochondrial NADH dehydrogenase I (ND1) gene of 33 women with RPL and 100 controls, using polymerase chain reaction amplification and DNA sequence analysis. Our results showed a statistically significant association of the T4216C mutation (p <  0.05) between patients and controls, which are 30% and 11%, respectively. In conclusion, more research is essentially needed to understand the effect and role of the T4216C mutation in the progress of RPL, which may vary among individuals and different ethnic groups.

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.