Increased prevalence of imprinting defects in patients with Angelman syndrome born to subfertile couples

Imprinting disorders in children conceived with assisted reproductive technology in Sweden

OBJECTIVE

To assess whether the use of assisted reproductive technology (ART) therapy for conception is associated with imprinting disorders in children and the impact of parental factors related to infertility.

DESIGN

A nationwide register-based cohort study.

SETTING

Swedish national registers and nationwide quality IVF register.

PATIENT(S)

All liveborn singletons in Sweden (N = 2,084,127) between 1997 and 2017 with follow-up to December 31, 2018.

INTERVENTION(S)

The use of specific methods implemented in ART.

MAIN OUTCOME MEASURE(S)

The International Classification of Diseases version 10 was used to identify three distinct imprinting disorder groups: Beckwith-Wiedemann syndrome (BWS), Prader-Willi syndrome (PWS), and Silver-Russell syndrome (SRS), as well as central precocious puberty. The Cox model combined with inverse probability treatment weights was used to estimate the weighted hazard ratio (wHR) with a 95% confidence interval (CI), accounting for multiple confounders.

RESULT(S)

A total of 1,044 children were diagnosed with the disorders of interest, and 52 of them were conceived using ART therapy. The overall risk of being diagnosed with any of the studied imprinting disorders was elevated in children conceived using ART therapy compared with all other children (HR, 1.84; 95% CI, 1.38-2.45). After adjusting for parental background factors, the association was partially attenuated (wHR, 1.50; 95% CI, 0.97-2.32), but remained in the weighted comparison restricted to children of couples with known infertility (wHR, 1.52; 95% CI, 1.05-2.21). For the specific diagnoses of PWS/SRS, and BWS compared with children of couples with known infertility, children conceived with ART therapy showed a small excess risk, which could not be distinguished from the null (wHR, 1.56; 95% CI, 0.93-2.62 and 1.80; 95% CI, 0.99-3.28, respectively). Further subgroup analysis showed that the combined use of intracytoplasmic sperm injection and cryopreserved embryos was associated with a higher risk of both PWS/SRS (wHR, 4.60; 95% CI, 1.72-12.28) and BWS (wHR, 6.69; 95% CI, 2.09-21.45). The number of central precocious puberty cases in children conceived using ART therapy was too small (N = 3) to make any meaningful inference.

CONCLUSION(S)

The combined use of intracytoplasmic sperm injection and cryopreserved embryos was associated with small elevated risks of PWS/SRS, and BWS in children, independent of parental factors related to infertility.

Higher incidence of embryonic defects in mouse offspring conceived with assisted reproduction from fathers with sperm epimutations

Assisted reproductive technologies (ART) account for 1-6% of births in developed countries. While most children conceived are healthy, increases in birth and genomic imprinting defects have been reported; such abnormal outcomes have been attributed to underlying parental infertility and/or the ART used. Here, we assessed whether paternal genetic and lifestyle factors, that are associated with male infertility and affect the sperm epigenome, can influence ART outcomes. We examined how paternal factors, haploinsufficiency for Dnmt3L, an important co-factor for DNA methylation reactions, and/or diet-induced obesity, in combination with ART (superovulation, in vitro fertilization, embryo culture and embryo transfer), could adversely influence embryo development and DNA methylation patterning in mice. While male mice fed high-fat diets (HFD) gained weight and showed perturbed metabolic health, their sperm DNA methylation was minimally affected by the diet. In contrast, Dnmt3L haploinsufficiency induced a marked loss of DNA methylation in sperm; notably, regions affected were associated with neurodevelopmental pathways and enriched in young retrotransposons, sequences that can have functional consequences in the next generation. Following ART, placental imprinted gene methylation and growth parameters were impacted by one or both paternal factors. For embryos conceived by natural conception, abnormality rates were similar for WT and Dnmt3L+/- fathers. In contrast, paternal Dnmt3L+/- genotype, as compared to WT fathers, resulted in a 3-fold increase in the incidence of morphological abnormalities in embryos generated by ART. Together, the results indicate that embryonic morphological and epigenetic defects associated with ART may be exacerbated in offspring conceived by fathers with sperm epimutations.

DNA Methylation in the Fields of Prenatal Diagnosis and Early Detection of Cancers

The central objective of the metamorphosis of discovery science into biomedical applications is to serve the purpose of patients and curtail the global disease burden. The journey from the discovery of DNA methylation (DNAm) as a biological process to its emergence as a diagnostic tool is one of the finest examples of such metamorphosis and has taken nearly a century. Particularly in the last decade, the application of DNA methylation studies in the clinic has been standardized more than ever before, with great potential to diagnose a multitude of diseases that are associated with a burgeoning number of genes with this epigenetic alteration. Fetal DNAm detection is becoming useful for noninvasive prenatal testing, whereas, in very preterm infants, DNAm is also shown to be a potential biological indicator of prenatal risk factors. In the context of cancer, liquid biopsy-based DNA-methylation profiling is offering valuable epigenetic biomarkers for noninvasive early-stage diagnosis. In this review, we focus on the applications of DNA methylation in prenatal diagnosis for delivering timely therapy before or after birth and in detecting early-stage cancers for better clinical outcomes. Furthermore, we also provide an up-to-date commercial landscape of DNAm biomarkers for cancer detection and screening of cancers of unknown origin.

Assisted reproductive technology (ART) and epigenetic modifications in the placenta

Assisted reproductive technology (ART) has become common amongst couples with infertility issues. ART is known to be successful, but epidemiological data indicates that ART is associated with placental disorders. Additionally, reports show increased risks of short- and long-term complications in children born to mothers undergoing ART. However, the mechanisms responsible for these events are obscure. The placenta is considered as a key organ for programming of diseases and ART procedures are suggested to alter the placental function and intrauterine growth trajectories. Epigenetic changes in maternal and foetal tissues are suggested to be the underlying mechanisms for these outcomes. Epigenetic regulation is known to evolve following fertilisation and before implantation and subsequently across gestation. During these critical periods of epigenetic 'programming', DNA methylation and chromatin remodelling influence the placental structure and function by regulating the expression of various genes. ART treatment coinciding with epigenetic 'programming' events during gametogenesis and early embryo development may alter the programming phases leading to long-term consequences. Thus, disruptions in placental development observed in ART pregnancies could be associated with altered epigenetic regulation of vital genes in the placenta. The review summarises available literature on the influence of ART procedures on epigenetic changes in the placenta.

IVF outcomes following ICSI cycles using testicular sperm in obstructive (OA) vs. non-obstructive azoospermia (NOA) and the impact of maternal and paternal age: a SART CORS data registry

PURPOSE

To assess the differences in IVF outcomes between couples with obstructive azoospermia (OA), non-obstructive azoospermia (NOA), and male factor (MF).

METHODS

Using the SART CORS data from 2016 to 2017, we included all initial autologous cycles with a diagnosis of male factor with ejaculated and surgically obtained sperm. We analyzed 71,121 cycles, including 3467 with a diagnosis of azoospermia and 67,654 with other non-azoospermic MF. Using a multivariate binomial regression, we estimated adjusted risk ratios comparing outcomes for ICSI cycles using surgically acquired (OA and NOA) versus ejaculated sperm (MF). Outcomes reported per initial cycle included clinical pregnancy, live birth, biochemical pregnancy, and miscarriage. Outcomes reported per singleton pregnancy included full-term delivery (≥ 37 weeks), normal birth weight (≥ 2500 g), and delivery method.

RESULTS

After frozen embryo transfers (FET), patients with NOA had 7% higher odds of live birth compared to MF (aOR 1.23 (0.94-1.74)), and those with OA had 2.6% lower chance of live birth compared to MF (aOR 0.73 (95%CI 0.5-1.05)). After fresh ET, patients with NOA had 5% higher chance of live birth (aOR 1.11 (0.9-1.36)), and those with OA had a 2.5% higher chance of live birth (aOR 1.10 (95%CI 0.89-1.34)) compared to MF. All three subgroups had lower fresh live birth rates (LBR) compared to FETs.

CONCLUSION

Couples with either NOA or OA have overall comparable ART and perinatal outcomes to couples with MF, and their success is primarily dependent on both patient's and partner's age.

Catechin versus MoS2 Nanoflakes Functionalized with Catechin: Improving the Sperm Fertilizing Ability-An In Vitro Study in a Swine Model

Nowadays, the adoption of In Vitro Fertilization (IVF) techniques is undergoing an impressive increase. In light of this, one of the most promising strategies is the novel use of non-physiological materials and naturally derived compounds for advanced sperm preparation methods. Here, sperm cells were exposed during capacitation to MoS₂/Catechin nanoflakes and catechin (CT), a flavonoid with antioxidant properties, at concentrations of 10, 1, 0.1 ppm. The results showed no significant differences in terms of sperm membrane modifications or biochemical pathways among the groups, allowing the hypothesis that MoS₂/CT nanoflakes do not induce any negative effect on the parameters evaluated related to sperm capacitation. Moreover, the addition of CT alone at a specific concentration (0.1 ppm) increased the spermatozoa fertilizing ability in an IVF assay by increasing the number of fertilized oocytes with respect to the control group. Our findings open interesting new perspectives regarding the use of catechins and new materials obtained using natural or bio compounds, which could be used to implement the current strategies for sperm capacitation.

Risk of genetic and epigenetic alteration in children conceived following ART: Is it time to return to nature whenever possible?

Assisted reproductive technology may influence epigenetic signature as the procedures coincide with the extensive epigenetic modification occurring from fertilization to embryo implantation. However, it is still unclear to what extent ART alters the embryo epigenome. In vivo fertilization occurs in the fallopian tube, where a specific and natural environment enables the embryo's healthy development. During this dynamic period, major waves of epigenetic reprogramming, crucial for the normal fate of the embryo, take place. Over the past decade, concerns relating to the raised incidence of epigenetic anomalies and imprinting following ART have been raised by several authors. Epigenetic reprogramming is particularly susceptible to environmental conditions during the periconceptional period; therefore, unphysiological conditions, including ovarian stimulation, in vitro fertilization, embryo culture, cryopreservation of gametes and embryos, parental lifestyle, and underlying infertility, have the potential to contribute to epigenetic dysregulation independently or collectively. This review critically appraises the evidence relating to the association between ART and genetic and epigenetic modifications that may be transmitted to the offspring.

Relationships between challenging behavior and gastrointestinal symptoms, sleep problems, and internalizing and externalizing symptoms in children and adolescents with Angelman syndrome

BACKGROUND

Angelman syndrome (AS), is a rare genetic disorder. This study investigated the relationship between parent-reported comorbid symptoms including gastrointestinal symptoms, sleep problems, internalizing symptoms, and behavior problems in children and adolescents with AS.

METHOD

Parents of 98 children and adolescents with AS completed the Gastrointestinal Symptom Inventory, Children's Sleep Habits Questionnaire, Child Behavior Checklist, Social Communication Questionnaire, and the Behavior Problem Inventory-Short Form. Data were analyzed using descriptive statistics, Pearson's correlation coefficients, and hierarchical multiple regressions.

RESULTS

There was a high frequency of GI symptoms (99%), sleep problems (95.9%), challenging behavior (98%), internalizing symptoms (38%), and 72.4% of children and adolescents presented with ASD symptoms. Self-injurious behavior (SIB), aggressive/destructive behavior, and the frequency of stereotyped behavior positively correlated with GI symptoms and sleep problems and it was moderately negatively associated with age. Internalizing symptoms and age were positively associated with SIB. Aggression was significantly related to gender, but not the presence of ASD symptoms.

CONCLUSIONS

Findings highlight the relationships between comorbid conditions. They may lead to a deeper understanding of how comorbidities present in children and adolescents with Angelman Syndrome.

Atypical Teratoid Rhabdoid Tumor in a Newborn: Can IVF Be a Risk Factor?

BackgroundIn recent years, with the widespread use of assisted reproductive technologies, questions have arisen regarding the possible relationship between these infertile parents with assisted conception procedures and childhood cancers. Case report: We present a 23-day-old newborn conceived by in vitro fertilization (IVF) with a 53 × 46 × 38 mm intracranial mass detected by magnetic resonance imaging on the 15th postnatal day. The mass, removed on 23rd postnatal day, was an Atypical Teratoid Rhabdoid Tumor (ATRT), WHO grade 4. Conclusions: As far as we know, this is the only neonatally detected ATRT. Further studies are needed to investigate whether there is a causal relationship between IVF and childhood cancers.

Pre-Treatment of Swine Oviductal Epithelial Cells with Progesterone Increases the Sperm Fertilizing Ability in an IVF Model

Mammalian spermatozoa are infertile immediately after ejaculation and need to undergo a functional modification, called capacitation, in order to acquire their fertilizing ability. Since oviductal epithelial cells (SOECs) and progesterone (P4) are two major modulators of capacitation, here we investigated their impact on sperm functionality by using an IVF swine model. To that, we treated SOECs with P4 at 10, 100, and 1000 ng/mL before the coincubation with spermatozoa, thus finding that P4 at 100 ng/mL does not interfere with the cytoskeleton dynamics nor the cells’ doubling time, but it promotes the sperm capacitation by increasing the number of spermatozoa per polyspermic oocyte (p < 0.05). Moreover, we found that SOECs pre-treatment with P4 100 ng/mL is able to promote an increase in the sperm fertilizing ability, without needing the hormone addition at the time of fertilization. Our results are probably due to the downregulation in the expression of OVGP1, SPP1 and DMBT1 genes, confirming an increase in the dynamism of our system compared to the classic IVF protocols. The results obtained are intended to contribute to the development of more physiological and efficient IVF systems.

Placental Abnormalities are Associated With Specific Windows of Embryo Culture in a Mouse Model

Assisted Reproductive Technologies (ART) employ gamete/embryo handling and culture in vitro to produce offspring. ART pregnancies have an increased risk of low birth weight, abnormal placentation, pregnancy complications, and imprinting disorders. Embryo culture induces low birth weight, abnormal placental morphology, and lower levels of DNA methylation in placentas in a mouse model of ART. Whether preimplantation embryos at specific stages of development are more susceptible to these perturbations remains unresolved. Accordingly, we performed embryo culture for several discrete periods of preimplantation development and following embryo transfer, assessed fetal and placental outcomes at term. We observed a reduction in fetal:placental ratio associated with two distinct windows of preimplantation embryo development, one prior to the morula stage and the other from the morula to blastocyst stage, whereas placental morphological abnormalities and reduced imprinting control region methylation were only associated with culture prior to the morula stage. Extended culture to the blastocyst stage also induces additional placental DNA methylation changes compared to embryos transferred at the morula stage, and female concepti exhibited a higher loss of DNA methylation than males. By identifying specific developmental windows of susceptibility, this study provides a framework to optimize further culture conditions to minimize risks associated with ART pregnancies.

Prenatal and Neonatal Characteristics of Children with Prader-Willi Syndrome

Objective: Prader-Willi syndrome (PWS) is a rare genetic syndrome with a wide spectrum of clinical features in early life. Late diagnoses are still present. We characterized the perinatal and neonatal features of PWS, compared them with those of healthy newborns and assessed the prenatal and neonatal differences between the genetic subtypes. Design: A cohort study in children with PWS. The prevalence of variables was compared with healthy infants (PLUTO cohort) and to population statistics from literature. Patients: 244 infants with PWS and 365 healthy infants. Measurements: Data on prenatal and neonatal variables in both cohorts. Population statistics were collected through an extensive literature search. Results: A higher prevalence of maternal age >35 years was found in PWS compared to healthy infants and population statistics, and the highest maternal age was found in the mUPD group. Higher prevalence of polyhydramnios, caesarean section, labour induction and breech presentation, and lower birth weight SDS was found in PWS compared to healthy infants. High prevalences of decreased fetal movements (78.5%), hypotonia (100%), cryptorchism (95.9%) and poor sucking/tube feeding (93.9%) were found in PWS. Conclusions: This study presents an overview of prenatal and neonatal variables in infants with PWS compared to healthy infants. Our findings may increase clinical awareness of the early perinatal signs of PWS by obstetricians, neonatologists and all those involved in infant care, enabling early diagnosis and start of multidisciplinary treatment.

Is there any effect on imprinted genes H19, PEG3, and SNRPN during AOA?

Assisted oocyte activation (AOA) has been proposed as an effective technique to overcome the problem of impaired fertilization after intracytoplasmic sperm injection (ICSI) but the safety of AOA remains a concern. We aimed to investigate if AOA induces imprinting effects on embryos. We used 13 cleavage embryos, nine blastocysts, and eight placentas from 15 patients. The subjects were divided into six groups by tissue type and with or without AOA. The methylation levels of imprinted genes (H19, paternally expressed gene [PEG3] and small nuclear ribonucleoprotein polypeptide N [SNRPN]) were tested by pyrosequencing. We observed different methylation levels among cleavage embryos. The variability was much more remarkable between cleavage embryos than blastocysts and placenta tissues. The methylation levels were especially higher in SNRPN and lower in the H19 gene in AOA embryos than those without AOA. No significant difference was found either among blastocysts or among placenta tissues regardless of AOA. The methylation levels of the three genes in blastocysts were very similar to those in the placenta. Compared to conventional ICSI, AOA changed imprinting methylation rates at H19 and SNRPN in cleavage embryos but not in the blastocyst stage and placenta. We recommend that blastocyst transfer should be considered for patients undergoing AOA during in vitro fertilization.

Oxygen concentration affects de novo DNA methylation and transcription in in vitro cultured oocytes

BACKGROUND

Reproductive biology methods rely on in vitro follicle cultures from mature follicles obtained by hormonal stimulation for generating metaphase II oocytes to be fertilised and developed into a healthy embryo. Such techniques are used routinely in both rodent and human species. DNA methylation is a dynamic process that plays a role in epigenetic regulation of gametogenesis and development. In mammalian oocytes, DNA methylation establishment regulates gene expression in the embryos. This regulation is particularly important for a class of genes, imprinted genes, whose expression patterns are crucial for the next generation. The aim of this work was to establish an in vitro culture system for immature mouse oocytes that will allow manipulation of specific factors for a deeper analysis of regulatory mechanisms for establishing transcription regulation-associated methylation patterns.

RESULTS

An in vitro culture system was developed from immature mouse oocytes that were grown to germinal vesicles (GV) under two different conditions: normoxia (20% oxygen, 20% O₂) and hypoxia (5% oxygen, 5% O₂). The cultured oocytes were sorted based on their sizes. Reduced representative bisulphite sequencing (RRBS) and RNA-seq libraries were generated from cultured and compared to in vivo-grown oocytes. In the in vitro cultured oocytes, global and CpG-island (CGI) methylation increased gradually along with oocyte growth, and methylation of the imprinted genes was similar to in vivo-grown oocytes. Transcriptomes of the oocytes grown in normoxia revealed chromatin reorganisation and enriched expression of female reproductive genes, whereas in the 5% O₂ condition, transcripts were biased towards cellular stress responses. To further confirm the results, we developed a functional assay based on our model for characterising oocyte methylation using drugs that reduce methylation and transcription. When histone methylation and transcription processes were reduced, DNA methylation at CGIs from gene bodies of grown oocytes presented a lower methylation profile.

CONCLUSIONS

Our observations reveal changes in DNA methylation and transcripts between oocytes cultured in vitro with different oxygen concentrations and in vivo-grown murine oocytes. Oocytes grown under 20% O₂ had a higher correlation with in vivo oocytes for DNA methylation and transcription demonstrating that higher oxygen concentration is beneficial for the oocyte maturation in ex vivo culture condition. Our results shed light on epigenetic mechanisms for the development of oocytes from an immature to GV oocyte in an in vitro culture model.

Genetic counseling prior to assisted reproductive technology

BACKGROUND

Reproductive medicine deals with fertility and is closely related to heredity. In reproductive medicine, it is necessary to provide genetic information for the patients prior to assisted reproductive technology (ART). Japan Society for Reproductive Medicine (JSRM) requires doctors involved in reproductive medicine to have standard knowledge of reproductive genetics and knowledge of reproductive medicine, which is covered in their publication, "required knowledge of reproductive medicine."

METHODS

With the aim of providing straightforward explanations to patients in the clinical situation at pre-ART counseling, we provide the following five topics, such as (a) risk of birth defects in children born with ART, (b) chromosomal abnormalities, (c) Y chromosome microdeletions (YCMs), (d) possible chromosomal abnormal pregnancy in oligospermatozoa requiring ICSI (intracytoplasmic sperm injection), and (e) epigenetic alterations.

MAIN FINDINGS

The frequency of chromosome abnormalities in infertile patients is 0.595%-0.64%. YCMs are observed in 2%-10% of severe oligospermic men. High incidence of spermatozoa with chromosomal abnormalities has been reported in advanced oligospermia and asthenozoospermia that require ICSI. Some epigenetic alterations were reported in the children born with ART.

CONCLUSION

Certain genetic knowledge is important for professionals involved in reproductive medicine, even if they are not genetic experts.

Association of Assisted Reproductive Technology Treatments with Imprinting Disorders

Assisted reproductive technology (ART) is a broad field in infertility that encompasses different types of treatments. These revolutionary treatment methods aimed to aid infertile or subfertile couples. Treatment was expanded exponentially, as 1 to 3% of the births worldwide takes place with ART procedures. However, treatment is not flawless. Gametes and embryos are exposed to different chemicals and stress through treatment, which leads to disturbance in proper embryo development and results in prenatal and congenital anomalies. When compared with in-vivo development of gametes and preimplantation embryos in mice, in-vitro conditions during ART treatments have been suggested to disturb the gene expression levels, especially imprinted genes. Therefore, ART has been suggested to be associated with increased incidences of different imprinting disorders such as Beckwith–Wiedemann syndrome, Angelman syndrome, and Silver–Russell syndrome, as proved by different case reports and studies. This literature review aims to explain the association of imprinting disorders with this revolutionary treatment procedure.

The prolonged disease state of infertility is associated with embryonic epigenetic dysregulation

OBJECTIVE

To evaluate the epigenetic consequence of a prolonged disease state of infertility in euploid blastocysts.

DESIGN

Methylome analysis as well as targeted imprinted methylation and expression analysis on individual human euploid blastocysts examined in association with duration of patient infertility and time to live birth.

SETTING

Research study.

PATIENT(S)

One hundred four surplus cryopreserved euploid blastocysts of transferrable-quality were donated with informed patient consent and grouped based on time to pregnancy (TTP).

INTERVENTION(S)

None MAIN OUTCOME MEASURE(S): The Methyl Maxi-Seq platform (Zymo Research) was used to determine genome-wide methylation, while targeted methylation and expression analyses were performed by pyrosequencing and quantitative real-time polymerase chain reaction, respectively. Statistical analyses used Student's t test, 1-way ANOVA, Fisher's exact test, and pairwise-fixed reallocation randomization test, where appropriate.

RESULT(S)

The methylome analysis of individual blastocysts revealed significant alterations at 6,609 CpG sites associated with prolonged infertility (≥60 months) compared with those of fertile controls (0 months). Significant CpG alterations were localized to numerous imprinting control regions and imprinted genes, and several signaling pathways were highly represented among genes that were differentially methylated. Targeted imprinting methylation analysis uncovered significant hypomethylation at KvDMR and MEST imprinting control regions, with significant decreases in the gene expression levels upon extended TTP (≥36 months) compared to minimal TTP (≤24 months).

CONCLUSION(S)

The prolonged disease state of infertility correlates with an altered methylome in euploid blastocysts, with particular emphasis on genomic imprinting regulation, compared with assisted reproductive technologies alone.

Biophysical optimization of preimplantation embryo culture: what mechanics can offer ART

Owing to the rise of ART and mounting reports of epigenetic modification associated with them, an understanding of optimal embryo culture conditions and reliable indicators of embryo quality are highly sought after. There is a growing body of evidence that mechanical biomarkers can rival embryo morphology as an early indicator of developmental potential and that biomimetic mechanical cues can promote healthy development in preimplantation embryos. This review will summarize studies that investigate the role of mechanics as both indicators and promoters of mammalian preimplantation embryo development and evaluate their potential for improving future embryo culture systems.

Engineered nanoparticle-induced epigenetic changes: An important consideration in nanomedicine

Engineered nanoparticles (ENPs) are now being applied across a range of disciplines, and as a result numerous studies have now assessed ENP-related bioeffects. Among them, ENP-induced epigenetic changes including DNA methylation, histone modifications, and miRNA-mediated regulation of gene expression have recently attracted attention. In this review, we describe the diversity of ENP-induced epigenetic changes, focusing on their interplay with related functional biological events, especially oxidative stress, MAPK pathway activation, and inflammation. In doing so, we highlight the underlying mechanisms and biological effects of ENP-induced epigenetic changes. We also summarize how high-throughput technologies have helped to uncover ENP-induced epigenetic changes. Finally, we discuss future perspectives and the challenges related to ENP-induced epigenetic changes that still need to be addressed.

Imprinting disorders in children born after ART: a Nordic study from the CoNARTaS group

STUDY QUESTION:

Is the risk of imprinting disorders increased in children conceived after

SUMMARY ANSWER:

We found an adjusted odds ratio (AOR) of 2.84 [95% CI: 1.34–6.01] for Beckwith–Wiedemann syndrome in ART children, while the risk of Prader–Willi syndrome, Silver–Russell syndrome or Angelman syndrome was not increased in children conceived after ART.

WHAT IS KNOWN ALREADY:

Earlier studies, most of them small, have suggested an association between ART and imprinting disorders.

STUDY DESIGN, SIZE, DURATION:

This was a binational register-based cohort study. All children conceived by ART in Denmark (n = 45 393, born between 1994 and 2014) and in Finland (n = 29 244, born between 1990 and 2014) were identified. The full background populations born during the same time periods in the two countries were included as controls. Odds ratios of imprinting disorders in ART children compared with naturally conceived (NC) children were calculated. The median follow-up time was 8 years and 9 months for ART children and 11 years and 9 months for NC children.

PARTICIPANTS/MATERIALS, SETTING, METHODS:

From the national health registries in Denmark and Finland, we identified all children diagnosed with Prader–Willi syndrome (n = 143), Silver–Russell syndrome (n = 69), Beckwith–Wiedemann syndrome (n = 105) and Angelman syndrome (n = 72) born between 1994/1990 and 2014, respectively.

MAIN RESULTS AND THE ROLE OF CHANCE:

We identified a total of 388 children diagnosed with imprinting disorders; 16 of these were conceived after ART. The overall AOR for the four imprinting disorders in ART children compared with NC children was 1.35 [95% CI: 0.80–2.29], but since eight ART children were diagnosed with Beckwith–Wiedemann syndrome, the AOR for this specific imprinting disorder was 2.84 [95% CI: 1.34–6.01]. The absolute risk of Beckwith–Wiedemann syndrome in children conceived after ART was still low: 10.7 out of 100 000 newborns. The risks of Prader–Willi syndrome, Silver–Russell syndrome and Angelman syndrome were not increased in children conceived after ART.

LIMITATIONS, REASONS FOR CAUTION:

Imprinting disorders are rare events and our results are based on few ART children with imprinting disorders. The aetiology is complex and only partly clarified, and the clinical diagnoses are challenged by a broad phenotypic spectrum.

WIDER IMPLICATIONS OF THE FINDINGS:

In the existing studies, results on the risk of imprinting disorders in children conceived after ART are ambiguous. This study adds that the risk of imprinting disorders in ART children is very small and perhaps restricted to Beckwith–Wiedemann syndrome.

STUDY FUNDING/COMPETING INTEREST(S):

This work was supported by the Nordic Trial Alliance: a pilot project jointly funded by the Nordic Council of Ministers and NordForsk (grant number: 71450), the Nordic Federation of Obstetrics and Gynecology (grant numbers: NF13041, NF15058, NF16026 and NF17043) and the Interreg Öresund-Kattegat-Skagerak European Regional Development Fund (ReproUnion project). The authors have no conflicts of interest related to this work.

TRIAL REGISTRATION NUMBER:

N/A

Perturbations in imprinted methylation from assisted reproductive technologies but not advanced maternal age in mouse preimplantation embryos

Background

Over the last several decades, the average age of first-time mothers has risen steadily. With increasing maternal age comes a decrease in fertility, which in turn has led to an increase in the use of assisted reproductive technologies by these women. Assisted reproductive technologies (ARTs), including superovulation and embryo culture, have been shown separately to alter imprinted DNA methylation maintenance in blastocysts. However, there has been little investigation on the effects of advanced maternal age, with or without ARTs, on genomic imprinting. We hypothesized that ARTs and advanced maternal age, separately and together, alter imprinted methylation in mouse preimplantation embryos. For this study, we examined imprinted methylation at three genes, Snrpn, Kcnq1ot1, and H19, which in humans are linked to ART-associated methylation errors that lead to imprinting disorders.

Results

Our data showed that imprinted methylation acquisition in oocytes was unaffected by increasing maternal age. Furthermore, imprinted methylation was normally acquired when advanced maternal age was combined with superovulation. Analysis of blastocyst-stage embryos revealed that imprinted methylation maintenance was also not affected by increasing maternal age. In a comparison of ARTs, we observed that the frequency of blastocysts with imprinted methylation loss was similar between the superovulation only and the embryo culture only groups, while the combination of superovulation and embryo culture resulted in a higher frequency of mouse blastocysts with maternal imprinted methylation perturbations than superovulation alone. Finally, the combination of increasing maternal age with ARTs had no additional effect on the frequency of imprinted methylation errors.

Conclusion

Collectively, increasing maternal age with or without superovulation had no effect of imprinted methylation acquisition at Snrpn, Kcnq1ot1, and H19 in oocytes. Furthermore, during preimplantation development, while ARTs generated perturbations in imprinted methylation maintenance in blastocysts, advanced maternal age did not increase the burden of imprinted methylation errors at Snrpn, Kcnq1ot1, and H19 when combined with ARTs. These results provide cautious optimism that advanced maternal age is not a contributing factor to imprinted methylation errors in embryos produced in the clinic. Furthermore, our data on the effects of ARTs strengthen the need to advance clinical methods to reduce imprinted methylation errors in in vitro-produced embryos.

DNA variants are an unlikely explanation for the changing quality of spermatozoa within the same individual

It has recently been suggested that the human sperm genome is highly unstable, which may be a reasonable explanation as to why men, even fertile men, produce defective spermatozoa. Furthermore, an unstable genome may also explain why the semen profile of the same man changes from one ejaculate to the next. As such, we took multiple ejaculates (between 3 and 6) from 7 individuals over a 6-month period and isolated sperm through density gradients. We then compared the DNA of: (i) good and poor-quality spermatozoa within the same ejaculate; and (ii) from multiple ejaculates from the same individual. Our results suggest that on a global level, DNA present within spermatozoa is actually quite stable and similar between both good and poor sperm. This is important information for the assisted reproductive community when it comes to sperm selection.

Genomic imprinting disorders: lessons on how genome, epigenome and environment interact

Genomic imprinting, the monoallelic and parent-of-origin-dependent expression of a subset of genes, is required for normal development, and its disruption leads to human disease. Imprinting defects can involve isolated or multilocus epigenetic changes that may have no evident genetic cause, or imprinting disruption can be traced back to alterations of cis-acting elements or trans-acting factors that control the establishment, maintenance and erasure of germline epigenetic imprints. Recent insights into the dynamics of the epigenome, including the effect of environmental factors, suggest that the developmental outcomes and heritability of imprinting disorders are influenced by interactions between the genome, the epigenome and the environment in germ cells and early embryos.

Epigenetics, Assisted Reproduction, and Intracytoplasmic Sperm Injection: A Review of the Current Data

Since the birth of the first in vitro fertilisation baby in 1978, >5 million babies have been born worldwide using assisted reproductive technologies (ART). ART were initially considered safe, but, in recent years, concerns regarding the association between these procedures and the increasing incidence of imprinting diseases have developed. There are numerous steps involved in ART and there are many variables that must be considered; even parental infertility may play an important role in offspring epigenetic modifications. This review presents available data from the literature regarding the incidence of these epigenetic modifications after ART, with a primary focus on oocyte insemination methodology. The authors conclude that ART, especially intracytoplasmic sperm injection, may induce epigenetic changes that can be transmitted to the offspring, but additional data are necessary to evaluate the factors involved and to determine the safety of each ART step.

Superovulation alters global DNA methylation in early mouse embryo development

Assisted reproductive technologies are known to alter the developmental environment of gametes and early embryos during the most dynamic period of establishing the epigenome. This may result in the introduction of errors during active DNA methylation reprogramming. Controlled ovarian hyperstimulation, or superovulation, is a ubiquitously used intervention which has been demonstrated to alter the methylation of certain imprinted genes. The objective of this study was to investigate whether ovarian hyperstimulation results in genome-wide DNA methylation changes in mouse early embryos. Ovarian hyperstimulation was induced by treating mice with either low doses (5 IU) or high doses (10 IU) of PMSG and hCG. Natural mating (NM) control mice received no treatment. Zygotes and 8-cell embryos were collected from each group and DNA methylomes were generated by whole-genome bisulfite sequencing. In the NM group, mean CpG methylation levels slightly decreased from zygote to 8-cell stage, whereas a large decrease in mean CpG methylation level was observed in both superovulated groups. A separate analysis of the mean CpG methylation levels within each developmental stage confirmed that significant genome-wide erasure of CpG methylation from the zygote to 8-cell stage only occurred in the superovulation groups. Our results suggest that superovulation alters the genome-wide DNA methylation erasure process in mouse early pre-implantation embryos. It is not clear whether these changes are transient or persistent. Further studies are ongoing to investigate the impact of ovarian hyperstimulation on DNA methylation re-establishment in later stages of embryo development.

Cancer risk among children conceived by fertility treatment

Prior studies on the association between fertility treatment and childhood cancer risk have generated inconsistent results. We performed a systematic review and meta-analysis of observation studies to summarize the evidence regarding the relation of fertility treatment with childhood cancer risk. A systematic literature search of several databases was conducted through April 2018 to identify relevant studies. The outcomes of interest included overall cancer, haematological malignancies, neural tumours, other solid tumours, and eight specific cancers. The overall risk estimates and corresponding 95% confidence intervals (CIs) were pooled using random-effects meta-analysis. Sixteen cohort and thirteen case-control studies were included. Results showed that children conceived by fertility treatment had significantly higher risk for developing overall cancer (relative risk [RR]: 1.16, 95% CI: 1.01, 1.32), haematological malignancies (RR: 1.39, 95% CI: 1.21, 1.60) and other solid tumours (RR: 1.57, 95% CI: 1.14, 2.16). For specific cancers, fertility treatment was associated with a significantly increased risk of leukaemia (RR: 1.31, 95% CI: 1.09, 1.57) and hepatic tumours (RR: 2.26, 95% CI: 1.32, 3.85). Sensitivity analysis validated evidence of the robustness of the findings. The results may demonstrate a possible association between fertility treatment and an increased risk of cancer among the offspring. However, the findings cannot say whether this increased risk is due to the subfertility itself or to the fertility treatment. Further research is needed to address the underlying mechanisms.

Aberrant DNA Methylation of IGF2-H19 Locus in Human Fetus and in Spermatozoa From Assisted Reproductive Technologies

Given the higher risk of developing imprinting disorders in assisted reproductive technology (ART)-conceived children, we hypothesized that ART may affect DNA methylation of the insulin-like growth factor 2 (IGF2), H19, small nuclear ribonucleoprotein polypeptide N (SNRPN) differentially methylated regions (DMRs) at the fetal stage, which in turn may be associated with sperm abnormalities. A total of 4 patient groups were recruited, namely, multifetal reduction following in vitro fertilization (IVF)/ intracytoplasmic sperm injection (ICSI; n = 56), multifetal reduction following controlled ovarian hyperstimulation (COH; n = 42), male patients with normal semen parameters denoted as normozoospermia group (NZ) for IVF (n = 36), and male patients presenting with asthenozoospermia (OAZ) for ICSI (n = 38). The expression levels and the DNA methylation status of IGF2-H19 and SNRPN DMRs in the fetuses and the semen samples were evaluated by real-time quantitative polymerase chain reaction and pyrosequencing. In our results, the expression levels of H19 were significantly higher, whereas the methylation rates were lower in IVF-conceived fetuses compared to the control group (P < .05). Furthermore, higher methylation rates of IGF2 DMR2 and SNRPN DMR were detected both in IVF- and ICSI-conceived fetuses (P < .05). The data further indicated that the patients who presented with the majority of the CpG sites in the H19 DMR region that were lower methylated were those in the OAZ group. The results demonstrated that the epigenetic dysregulations of IGF2-H19 and SNRPN DMRs that were caused by ART were noted in the fetuses. Moreover, the present study suggested that epigenetic perturbations of the H19 DMR might be a key biomarker for spermatogenesis defects in humans.

Clinical outcomes following ICSI cycles using surgically recovered sperm and the impact of maternal age: 2004-2015 SART CORS registry

PURPOSE

The aims of this study were (1) to evaluate clinical outcomes after ICSI cycles using surgically recovered sperm and (2) to assess the influence of maternal age on those outcomes.

METHODS

A retrospective cohort study of 24,763 IVF cycles of fresh autologous oocytes and ICSI using surgically recovered sperm reported to the SART CORS database from 2004 to 2015.

RESULTS AND CONCLUSIONS

Older women had significantly longer stimulation (p < 0.001), a lower number of oocytes retrieved (p < 0.001), a lower number of 2PN zygotes (p < 0.001), a lower chance of having a blastocyst transferred (p < 0.001), and a higher number of fresh embryos transferred (p < 0.001). There was no significant association between the number of 2PNs per oocyte retrieved and maternal age (p = 0.214). Both clinical pregnancy rates and live birth rates (LBR) decreased with advanced maternal age (p < 0.001). LBR ranged from 50.4% in women < 30 to 7.2% in women > 42 years, and for cleavage-stage transfers, the LBR ranged from 47.3% in women< 30 to 6.3% in women > 42 years. There were no differences in gestational age at delivery, proportion of term deliveries, preterm deliveries, neonatal birth weight < 2500 g, neonatal birth weight > 4000 g and average birthweight of neonates for singleton pregnancies according to age. For twin pregnancies, women < 30 years had significantly higher number of live births, term deliveries, and lower preterm deliveries than older women. There was a similar number of female (6051) and male neonates (5858; p = 0.2). Overall, pregnancy outcomes with ICSI using surgically recovered sperm are reassuring and comparable to those of ICSI with ejaculated sperm.

An epigenetic association of malformations, adverse reproductive outcomes, and fetal origins hypothesis related effects

VACTERL, the prototype for associated congenital anomalies, also has connections with functional issues such as pregnancy losses, prematurity, growth delays, perinatal difficulties, and parental subfertility. This segues into a broader association with similar connections even in the absence of malformations. DNA methylation disturbances in the ovum are a likely cause, with epigenetic links to individual components and to folate effects before conception, explaining diverse fetal and placental findings and providing a link to fetal origin hypothesis-related effects. The association encompasses the following: (1) Pre- and periconceptual effects, with frequent fertility issues and occasional imprinting disorders. (2) Early malformations. (3) Adverse pregnancy outcomes (APOs), as above. (4) Developmental destabilization that resolves soon after birth. This potentiates other causes of association findings, introducing multiple confounders. (5) Long-term fetal origins hypothesis-related risks. The other findings are exceptional when the same malformations have Mendelian origins, supporting a distinct pathogenesis. Expressions are facilitated by one-carbon metabolic issues, maternal and fetal stress, and decreased embryo size. This may be one of the commonest causes of adverse reproductive outcomes, but multifactorial findings, variable onsets and phenotypes, and interactions with multiple confounders make recognition difficult. This association supports VACTERL as a continuum that includes isolated malformations, extends the fetal origins hypothesis, explains adverse effects linked to maternal obesity, and suggests possible interventions.

DNA methylation signatures in cord blood of ICSI children

STUDY QUESTION

Does ICSI induce specific DNA methylation changes in the resulting offspring?

SUMMARY ANSWER

Although several thousand analyzed CpG sites (throughout the genome) displayed significant between-group methylation differences, both ICSI and spontaneously conceived children varied within the normal range of methylation variation.

WHAT IS KNOWN ALREADY

Children conceived by ART have increased risks for medical problems at birth and to the extent of present knowledge also in later life (i.e. impaired metabolic and cardiovascular functions). One plausible mechanism mediating these ART effects are epigenetic changes originating in the germ cells and/or early embryos and persisting during further development.

STUDY DESIGN, SIZE, DURATION

We compared the cord blood methylomes and candidate gene methylation patterns of newborns conceived through ICSI or spontaneously.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Umbilical cord bloods were obtained from healthy newborn singletons conceived spontaneously (53 samples), through ICSI (89) or IVF (34). Bisulfite-converted DNA samples of 48 ICSI and 46 control pregnancies were used for genome-wide analyses with Illumina's 450K methylation arrays. Candidate genes from the methylation screen were analyzed in all three groups by bisulfite pyrosequencing.

MAIN RESULTS AND THE ROLE OF CHANCE

Altogether, 4730 (0.11%) of 428 227 analyzed CpG sites exhibited significant between-group methylation differences, but all with small (β < 10%) or very small (β < 1%) effect size. ICSI children showed a significantly decreased DNA methylation age at birth, lagging approximately half a week behind the controls. ART-susceptible CpGs were enriched in CpG islands with low methylation values (0-20%) and in imprinting control regions (ICRs). Eighteen promoter regions (six in microRNA and SNORD RNA genes), four CpG islands (three in genes including one long non-coding RNA), and two ICRs contained multiple significant sites. Three differentially methylated regions were studied in more detail by bisulfite pyrosequencing. ATG4C and SNORD114-9 could be validated in an independent ICSI group, following adjustment for maternal age and other confounding factors. ATG4C was also significant in the IVF group.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The observed epigenetic effects are small and there are numerous potential confounding factors such as parental age and infertility. Although our study meets current standards for epigenetic screens, sample size is still two orders of magnitude below that of genome-wide association studies.

WIDER IMPLICATIONS OF THE FINDINGS

Our study suggests an impact of ICSI on the offspring's epigenome(s), which may contribute to phenotypic variation and disease susceptibility in ART children. Epigenetic regulation of gene expression by different classes of non-coding RNAs may be a key mechanism for developmental programming through ART.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by a research grant (no. 692185) from the European Union (ERA of ART). There are no competing interests.

Comprehensive meta-analysis reveals association between multiple imprinting disorders and conception by assisted reproductive technology

PURPOSE

To determine whether a history of conception by assisted reproductive technology (ART) is associated with occurrence of one or more imprinting disorders of either maternal or paternal origin.

METHODS

We implemented a systematic review of scholarly literature followed by comprehensive meta-analysis to quantitatively synthesize data from reports relating to use of ART to occurrence of any imprinting disorder of humans, including Beckwith-Wiedemann (BWS), Angelman (AS), Prader-Willi (PWS), and Silver-Russell (SRS) syndromes, as well as transient neonatal diabetes mellitus (TNDB) and sporadic retinoblasoma (RB).

RESULTS

The systematic review identified 13 reports presenting unique data from 23 studies that related conception following ART to occurrence of imprinting disorders. Multiple studies of four disorder were identified, for which meta-analysis yielded the following summary estimates of associations with a history of ART: AS, summary odds ratio (sOR) = 4.7 (95% confidence interval (CI) 2.6-8.5, 4 studies); BWS, sOR = 5.8 (95% CI 3.1-11.1, 8 studies); PWS, sOR = 2.2 (95% CI 1.6-3.0, 6 studies); SRS, sOR = 11.3 (95% CI 4.5-28.5, 3 studies). Only one study reported on each of TNDB and RB.

CONCLUSION

Published data reveal positive associations between history of ART conception and each of four imprinting disorders. Reasons for these associations warrant further investigation.

Compromised oocyte quality and assisted reproduction contribute to sex-specific effects on offspring outcomes and epigenetic patterning

Clinical studies have revealed an increased incidence of growth and genomic imprinting disorders in children conceived using assisted reproductive technologies (ARTs), and aberrant DNA methylation has been implicated. We propose that compromised oocyte quality associated with female infertility may make embryos more susceptible to the induction of epigenetic defects by ART. DNA methylation patterns in the preimplantation embryo are dependent on the oocyte-specific DNA methyltransferase 1o (DNMT1o), levels of which are decreased in mature oocytes of aging females. Here, we assessed the effects of maternal deficiency in DNMT1o (Dnmt1Δ1o/+) in combination with superovulation and embryo transfer on offspring DNA methylation and development. We demonstrated a significant increase in the rates of morphological abnormalities in offspring collected from Dnmt1Δ1o/+  females only when combined with ART. Together, maternal oocyte DNMT1o deficiency and ART resulted in an accentuation of placental imprinting defects and the induction of genome-wide DNA methylation alterations, which were exacerbated in the placenta compared to the embryo. Significant sex-specific trends were also apparent, with a preponderance of DNA hypomethylation in females. Among genic regions affected, a significant enrichment for neurodevelopmental pathways was observed. Taken together, our results demonstrate that oocyte DNMT1o-deficiency exacerbates genome-wide DNA methylation abnormalities induced by ART in a sex-specific manner and plays a role in mediating poor embryonic outcome.

Epigenetic changes in preimplantation embryos subjected to laser manipulation

The advantage of using laser for assisted hatching in routine assisted reproductive technology (ART) practice is debatable. Recently, it has been shown that laser-manipulated mouse embryos had compromised genetic integrity. However, the impact of laser-assisted hatching (LAH) on the epigenetic integrity of the preimplantation embryos is not elucidated so far. Since continuous thermal stress on embryos was found to lower mRNA levels of de novo (bovine) methyl transferases in embryos, we hypothesize that thermal energy induced during LAH may alter the epigenetic signature through abnormal de novo methyl transferases (Dnmts) levels. Thus, using mouse model, we made an attempt to look into the expression of Dnmt3a and Dnmt3b in laser-manipulated embryos and their effects on global methylation. This experimental prospective study used mouse embryos from varying developmental stages (2-cell, 6-8-cell, and blastocyst) which were subjected to LAH using a 1480-nm diode laser. Two pulses of 350 μs frequency were applied to breach the zona pellucida, and then, embryos were assessed for the expression of two de novo methyl transferases (Dnmt3a and Dnmt3b) and LINE-1 (long interspersed element-1) methylation when LAH embryos developed to blastocyst stage. Results from this study have shown that blastocysts subjected to LAH at two-cell stage had significantly lower mRNA transcripts of Dnmt3a (P < 0.01) and Dnmt3b (P < 0.05) whereas LAH at six- to eight-cell and blastocyst stages did not affect the mRNA level significantly. On the other hand, LINE-1 methylation did not change significantly between LAH and control group in all the stages studied. These results suggest that two-cell-stage laser manipulation of embryos changes the mRNA level of Dnmts without affecting the global DNA methylation.

Pseudohypoparathyroidism type 1B associated with assisted reproductive technology

Evidence suggests an increased incidence of imprinting disorders in children conceived by assisted reproductive technologies (ART). Maternal loss-of-methylation at GNAS exon A/B, observed in pseudohypoparathyroidism type 1b (PHP1B), leads to decreased expression of the stimulatory Gsα. We present a patient conceived by ART, who presented at age 4 years with delayed neurocognitive development and persistently increased creatine kinase (CK). At 6 years an elevated PTH was detected with normal calcium and a low 25(OH) vitamin D level (25OHD). Physical exam showed a narrow forehead, nasal bridge hypoplasia and micropenis. After normalizing vitamin D, PTH remained elevated and PHP1B was therefore considered as the underlying diagnosis. An almost complete loss-of-methylation was observed at GNAS exons A/B and AS, but not at exon XL, which was associated with a gain-of-methylation at exon NESP. There was no evidence of a microdeletion within the GNAS/STX16 region and analysis of several microsatellite markers for the GNAS region on Chr.20q revealed no evidence for paternal uniparental disomy (patUPD20q). Established facts Increased incidence of imprinting disorders in children conceived by assisted reproductive technologies (ART) Pseudohypoparathyroidism is caused by imprinting abnormalities. Novel Insights First report of a possible association between a methylation defects that causes PHP1B and assisted conception Increased creatine kinase level was associated with an increase in PTH concentration.

Epigenetics of Autism Spectrum Disorder

Autism spectrum disorder (ASD), one of the most common childhood neurodevelopmental disorders (NDDs), is diagnosed in 1 of every 68 children. ASD is incredibly heterogeneous both clinically and aetiologically. The etiopathogenesis of ASD is known to be complex, including genetic, environmental and epigenetic factors. Normal epigenetic marks modifiable by both genetics and environmental exposures can result in epigenetic alterations that disrupt the regulation of gene expression, negatively impacting biological pathways important for brain development. In this chapter we aim to summarize some of the important literature that supports a role for epigenetics in the underlying molecular mechanism of ASD. We provide evidence from work in genetics, from environmental exposures and finally from more recent studies aimed at directly determining ASD-specific epigenetic patterns, focusing mainly on DNA methylation (DNAm). Finally, we briefly discuss some of the implications of current research on potential epigenetic targets for therapeutics and novel avenues for future work.

Genetic and epigenetic risks of assisted reproduction

Assisted reproductive technology (ART) is used primarily for infertility treatments to achieve pregnancy and involves procedures such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), and cryopreservation. Moreover, preimplantation genetic diagnosis (PGD) of ART is used in couples for genetic reasons. In ART treatments, gametes and zygotes are exposed to a series of non-physiological processes and culture media. Although the majority of children born with this treatment are healthy, some concerns remain regarding the safety of this technology. Animal studies and follow-up studies of ART-borne children suggested that ART was associated with an increased incidence of genetic, physical, or developmental abnormalities, although there are also observations that contradict these findings. As IVF, ICSI, frozen-thawed embryo transfer, and PGD manipulate gametes and embryo at a time that is important for reprogramming, they may affect epigenetic stability, leading to gamete/embryo origins of adult diseases. In fact, ART offspring have been reported to have an increased risk of gamete/embryo origins of adult diseases, such as early-onset diabetes, cardiovascular disease, and so on. In this review, we will discuss evidence related to genetic, especially epigenetic, risks of assisted reproduction.

Maternal fertility problems and risk for transient neonatal diabetes mellitus

AIMS

The study of imprinting disorders in the context of infertility and its treatment is important, as studies have indicated an increased risk. In this study, we evaluated the risk of transient neonatal diabetes mellitus (TNDM), defined here as diabetes mellitus presenting within the first six weeks of life, in children born to women with fertility problems.

METHODS

This nationwide register-based cohort study comprised all 2,107,837 children born in Denmark between 1977 and 2010. Of these, 121,044 (5.7%) children were born to women with fertility problems. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between maternal fertility status and the risk for TNDM.

RESULTS

A total of 103 children developed TNDM during the follow-up period. Children born to women with fertility problems had an elevated risk for TNDM, after adjustment for birth year, maternal age at birth and parental history of diabetes, although this was not statistically significant (HR = 1.49; 95% CI 0.73-3.03). The risk of children born in the period 1994-2010 (a period with more comprehensive information on maternal fertility problems and with more invasive fertility treatment procedures) was increased almost twofold (HR = 1.92; 95% CI 0.92-4.00) but was still not statistically significant.

CONCLUSIONS

Our results indicate that children born to women with fertility problems, particularly after 1993, may be at an elevated risk for TNDM. As the increased risks were not statistically significant, however, the finding may be due to chance.

Maintenance of Mest imprinted methylation in blastocyst-stage mouse embryos is less stable than other imprinted loci following superovulation or embryo culture

Assisted reproductive technologies are fertility treatments used by subfertile couples to conceive their biological child. Although generally considered safe, these pregnancies have been linked to genomic imprinting disorders, including Beckwith-Wiedemann and Silver-Russell Syndromes. Silver-Russell Syndrome is a growth disorder characterized by pre- and post-natal growth retardation. The Mest imprinted domain is one candidate region on chromosome 7 implicated in Silver-Russell Syndrome. We have previously shown that maintenance of imprinted methylation was disrupted by superovulation or embryo culture during pre-implantation mouse development. For superovulation, this disruption did not originate in oogenesis as a methylation acquisition defect. However, in comparison to other genes, Mest exhibits late methylation acquisition kinetics, possibly making Mest more vulnerable to perturbation by environmental insult. In this study, we present a comprehensive evaluation of the effects of superovulation and in vitro culture on genomic imprinting at the Mest gene. Superovulation resulted in disruption of imprinted methylation at the maternal Mest allele in blastocysts with an equal frequency of embryos having methylation errors following low or high hormone treatment. This disruption was not due to a failure of imprinted methylation acquisition at Mest in oocytes. For cultured embryos, both the Fast and Slow culture groups experienced a significant loss of maternal Mest methylation compared to in vivo-derived controls. This loss of methylation was independent of development rates in culture. These results indicate that Mest is more susceptible to imprinted methylation maintenance errors compared to other imprinted genes.

The epigenetic effects of assisted reproductive technologies: ethical considerations

The use of assisted reproductive technologies (ART) has increased significantly, allowing many coping with infertility to conceive. However, an emerging body of evidence suggests that ART could carry epigenetic risks for those conceived through the use of these technologies. In accordance with the Developmental Origins of Health and Disease hypothesis, ART could increase the risk of developing late-onset diseases through epigenetic mechanisms, as superovulation, fertilization methods and embryo culture could impair the embryo’s epigenetic reprogramming. Such epigenetic risks raise ethical issues for all stakeholders: prospective parents and children, health professionals and society. This paper focuses on ethical issues raised by the consideration of these risks when using ART. We apply two key ethical principles of North American bioethics (respect for autonomy and non-maleficence) and suggest that an ethical tension may emerge from conflicting duties to promote the reproductive autonomy of prospective parents on one hand, and to minimize risks to prospective children on the other. We argue that this tension is inherent to the entire enterprise of ART and thus cannot be addressed by individual clinicians in individual cases. We also consider the implications of the ‘non-identity problem’ in this context. We call for additional research that would allow a more robust evidence base for policy. We also call upon professional societies to provide clinicians with guidelines and educational resources to facilitate the communication of epigenetic risks associated with ART to patients, taking into consideration the challenges of communicating risk information whose validity is still uncertain.

Impacts of and interactions between environmental stress and epigenetic programming during early embryo development

The processes of assisted reproductive technologies (ART) involve a variety of interventions that impact on the oocyte and embryo. Critically, these interventions cause considerable stress and coincide with important imprinting events throughout gametogenesis, fertilisation and early embryonic development. It is now accepted that the IVM and in vitro development of gametes and embryos can perturb the natural course of development to varying degrees of severity. Altered gene expression and, more recently, imprinting disorders relating to ART have become a focused area of research. Although various hypotheses have been put forward, most research has been observational, with little attempt to discover the mechanisms and periods of sensitivity during embryo development that are influenced by the culture conditions following fertilisation. The embryo possesses innate survival factor signalling pathways, yet when an embryo is placed in culture, this signalling in response to in vitro stress becomes critically important in mitigating the effects of stresses caused by the in vitro environment. It is apparent that not all embryos possess this ability to adequately adapt to the stresses experienced in vitro, most probably due to an inadequate oocyte. It is speculated that it is important that embryos use their survival signalling mechanisms to maintain normal epigenetic programming. The seeming redundancy in the function of various survival signalling pathways would support this notion. Any invasion into the natural, highly orchestrated and dynamic process of sexual reproduction could perturb the normal progression of epigenetic programming. Therefore the source of gametes and the subsequent culture conditions of gametes and embryos are critically important and require careful attention. It is the aim of this review to highlight avenues of research to elucidate the effects of stress and the relationship with epigenetic programming. The short- and long-term health and viability of human and animal embryos derived in vitro will also be discussed.

DNA methylation changes at infertility genes in newborn twins conceived by in vitro fertilisation

BACKGROUND

The association of in vitro fertilisation (IVF) and DNA methylation has been studied predominantly at regulatory regions of imprinted genes and at just thousands of the ~28 million CpG sites in the human genome.

METHODS

We investigated the links between IVF and DNA methylation patterns in whole cord blood cells (n = 98) and cord blood mononuclear cells (n = 82) from newborn twins using genome-wide methylated DNA immunoprecipitation coupled with deep sequencing.

RESULTS

At a false discovery rate (FDR) of 5%, we identified one significant whole blood DNA methylation change linked to conception via IVF, which was located ~3 kb upstream of TNP1, a gene previously linked to male infertility. The 46 most strongly associated signals (FDR of 25%) included a second region in a gene also previously linked to infertility, C9orf3, suggesting that our findings may in part capture the effect of parental subfertility. Using twin modelling, we observed that individual-specific environmental factors appear to be the main overall contributors of methylation variability at the FDR 25% IVF-associated differentially methylated regions, although evidence for methylation heritability was also obtained at several of these regions. We replicated previous findings of differential methylation associated with IVF at the H19/IGF2 region in cord blood mononuclear cells, and we validated the signal at C9orf3 in monozygotic twins. We also explored the impact of intracytoplasmic sperm injection on the FDR 25% signals for potential effects specific to male or female infertility factors.

CONCLUSIONS

To our knowledge, this is the most comprehensive study of DNA methylation profiles at birth and IVF conception to date, and our results show evidence for epigenetic modifications that may in part reflect parental subfertility.

The influence of in vitro fertilization and embryo culture on the embryo epigenetic constituents and the possible consequences in the bovine model

Medically assisted reproductive technologies, such as in vitro embryo production, are increasingly being used to palliate infertility. Eggs are produced following a hormonal regimen that stimulates the ovaries to produce a large number of oocytes. Collected oocytes are then fertilized in vitro and allowed to develop in vitro until they are either frozen or transferred to mothers. There are controversial reports on the adverse impacts of these technologies on early embryos and their potential long-term effects. Using newly developed technological platforms that enable global gene expression and global DNA methylation profiling, we evaluated gene perturbations caused by such artificial procedures. We know that cells in the early embryo produce all cells in the body and are able to respond to their in vitro environment. However, it is not known whether gene perturbations are part of a normal response to the environment or are due to distress and will have long-term impacts. While the mouse is an established genetic model used for quality control of culture media in clinics, the bovine is a large mono-ovulating mammal with similar embryonic kinetics as humans during the studied developmental window. These model systems are critical to understand the effects of assisted reproduction without the confounding impact of infertility and without the limitations imposed by the scarcity of donated human samples and ethical issues. The data presented in this review come mostly from our own experimentation, publications, and collaborations. Together they demonstrate that the in vitro environment has a significant impact on embryos at the transcriptomic level and at the DNA methylation level.

Constitutional Epi/Genetic Conditions: Genetic, Epigenetic, and Environmental Factors

There are more than 4,000 phenotypes for which the molecular basis is at least partly known. Though defects in primary DNA structure constitute a major cause of these disorders, epigenetic disruption is emerging as an important alternative mechanism in the etiology of a broad range of congenital and developmental conditions. These include epigenetic defects caused by either localized (in cis) genetic alterations or more distant (in trans) genetic events but can also include environmental effects. Emerging evidence suggests interplay between genetic and environmental factors in the epigenetic etiology of several constitutional "epi/genetic" conditions. This review summarizes our broadening understanding of how epigenetics contributes to pediatric disease by exploring different classes of epigenomic disorders. It further challenges the simplistic dogma of "DNA encodes RNA encodes protein" to best understand the spectrum of factors that can influence genetic traits in a pediatric population.

Epigenetic Influences During the Periconception Period and Assisted Reproduction

The periconception period starts 6 months before conception and lasts until the tenth week of gestation. In this chapter, we will focus on epigenetic modifications to DNA and gene expression within this period and during assisted reproduction. There are two critical times during the periconception window when significant epigenetic 'reprogramming' occur: one during gametogenesis and another during the pre-implantation embryonic stage. Furthermore, assisted conception treatments, laboratory protocols and culture media can affect the embryo development and birth weights in laboratory animals. There is, however, an ongoing debate as to whether epigenetic changes in humans, causing embryo mal-development, placenta dysfunction and birth defects, result from assisted reproductive technologies or are consequences of pre-existing medical and/or genetic conditions in the parents. The periconception period starts from ovarian folliculogenesis, through resumption of oogenesis, fertilisation, peri-implantation embryo development, embryogenesis until the end of organogenesis. In men, it is the period from spermatogenesis to epididymal sperm storage and fertilisation. Gametes and developing embryos are sensitive to environmental factors during this period, and epigenetic modifications can occur in response to adverse lifestyles and environmental factors. We now know that lifestyle factors such as advanced parentage age, obesity or undernutrition, smoking, excessive alcohol and caffeine intake and recreational drugs used during gamete production and embryogenesis could induce epigenetic alterations, which could impact adversely on pregnancy outcomes and health of the offspring. Furthermore, these can also result in a permanent and irreversible effect in a dose-dependent manner, which can be passed on to the future generations.

Clinical and molecular analyses of Beckwith-Wiedemann syndrome: Comparison between spontaneous conception and assisted reproduction techniques

Beckwith-Wiedemann syndrome (BWS) is an overgrowth syndrome characterized by an excessive prenatal and postnatal growth, macrosomia, macroglossia, and hemihyperplasia. The molecular basis of this syndrome is complex and heterogeneous, involving genes located at 11p15.5. BWS is correlated with assisted reproductive techniques. BWS in individuals born following assisted reproductive techniques has been found to occur four to nine times higher compared to children with to BWS born after spontaneous conception. Here, we report a series of 187 patients with to BWS born either after assisted reproductive techniques or conceived naturally. Eighty-eight percent of BWS patients born via assisted reproductive techniques had hypomethylation of KCNQ1OT1:TSS-DMR in comparison with 49% for patients with BWS conceived naturally. None of the patients with BWS born via assisted reproductive techniques had hypermethylation of H19/IGF2:IG-DMR, neither CDKN1 C mutations nor patUPD11. We did not find differences in the frequency of multi-locus imprinting disturbances between groups. Patients with BWS born via assisted reproductive techniques had an increased frequency of advanced bone age, congenital heart disease, and decreased frequency of earlobe anomalies but these differences may be explained by the different molecular background compared to those with BWS and spontaneous fertilization. We conclude there is a correlation of the molecular etiology of BWS with the type of conception. © 2016 Wiley Periodicals, Inc.