Another case of imprinting defect in a girl with Angelman syndrome who was conceived by intracytoplasmic semen injection

Progenitor cells for regenerative medicine and consequences of ART and cloning-associated epimutations

The "holy grail" of regenerative medicine is the identification of an undifferentiated progenitor cell that is pluripotent, patient specific, and ethically unambiguous. Such a progenitor cell must also be able to differentiate into functional, transplantable tissue, while avoiding the risks of immune rejection. With reports detailing aberrant genomic imprinting associated with assisted reproductive technologies (ART) and reproductive cloning, the idea that human embryonic stem cells (hESCs) derived from surplus in vitro fertilized embryos or nuclear transfer ESCs (ntESCs) harvested from cloned embryos may harbor dangerous epigenetic errors has gained attention. Various progenitor cell sources have been proposed for human therapy, from hESCs to ntESCs, and from adult stem cells to induced pluripotent stem cells (iPS and piPS cells). This review highlights the advantages and disadvantages of each of these technologies, with particular emphasis on epigenetic stability.

In vitro fertilization and embryo culture strongly impact the placental transcriptome in the mouse model

Background

Assisted Reproductive Technologies (ART) are increasingly used in humans; however, their impact is now questioned. At blastocyst stage, the trophectoderm is directly in contact with an artificial medium environment, which can impact placental development. This study was designed to carry out an in-depth analysis of the placental transcriptome after ART in mice.

Methodology/Principal Findings

Blastocysts were transferred either (1) after in vivo fertilization and development (control group) or (2) after in vitro fertilization and embryo culture. Placentas were then analyzed at E10.5. Six percent of transcripts were altered at the two-fold threshold in placentas of manipulated embryos, 2/3 of transcripts being down-regulated. Strikingly, the X-chromosome harbors 11% of altered genes, 2/3 being induced. Imprinted genes were modified similarly to the X. Promoter composition analysis indicates that FOXA transcription factors may be involved in the transcriptional deregulations.

Conclusions

For the first time, our study shows that in vitro fertilization associated with embryo culture strongly modify the placental expression profile, long after embryo manipulations, meaning that the stress of artificial environment is memorized after implantation. Expression of X and imprinted genes is also greatly modulated probably to adapt to adverse conditions. Our results highlight the importance of studying human placentas from ART.

Skewed X inactivation and IVF-conceived infants

The objective of this study was to investigate whether skewed X chromosome inactivation (XCI) is associated with IVF. A retrospective cohort study was performed comprising 30 female infants conceived by IVF and 44 naturally conceived control infants matched for gestational age and sex. Cord blood DNA samples were obtained and XCI patterns were analysed using a methylation-sensitive assay. Eight IVF samples and 13 control samples were excluded from the study because they were either homozygous or alleles were too similar for the assay to determine skewing. Mildly skewed XCI (80-90% inactivation of one allele) was present in two of 22 (9.1%) IVF samples and two of 31 (6.5%) control samples. Extremely skewed XCI (>90% inactivation of one allele) was found in two of 22 (9.1%) IVF samples and none of 31 control samples. Neither difference was statistically significant. However, the mean degree of skewed XCI in the IVF group was 72.0% and in the control group was 62.4% (P=0.002). Larger studies are needed to clarify the relationship between IVF and skewed XCI.

Human imprinting syndromes

Human imprinting disorders can provide critical insights into the role of imprinted genes in human development and health, and the molecular mechanisms that regulate genomic imprinting. To illustrate these concepts we review the clinical and molecular features of several human imprinting syndromes including Beckwith–Wiedemann syndrome, Silver–Russell syndrome, Angelman syndrome, Prader–Willi syndrome, pseudohypoparathyroidism, transient neonatal diabetes, familial complete hydatidiform moles and chromosome 14q32 imprinting domain disorders.

Growth of children conceived by IVF and ICSI up to 12years of age

Recent studies have given conflicting results regarding growth in children born following assisted reproductive treatments up to the age of 18years. It has been suggested that children conceived via IVF may be taller than naturally conceived children and that this may due to subtle epigenetic alteration of imprinted genes as a result of the IVF process. A prospective match-controlled study was performed to investigate the growth of children born in the UK following standard IVF and intracytoplasmic sperm injection (ICSI) up to the age of 12years. The study assessed 143 IVF and 166 ICSI children with 173 matched naturally conceived controls. Primary end-points were height and weight at various time points: birth, 5years, 7-9years and 10-12years. In addition, head circumference was assessed at birth. No significant differences were observed regarding head circumference, height and weight between the three groups at any of the time points. In conclusion, this preliminary study provides reassuring information regarding the growth of IVF and ICSI children up to 12years. Further studies must continue to investigate the growth and other outcomes in assisted-conception children as they develop through puberty into early adulthood.

Intrauterine environment-genome interaction and children's development (3): Assisted reproductive technologies and developmental disorders

In vitro fertilization (IVF) and other assisted reproductive technologies (ART) are widely used clinically as infertility treatments. Although ART procedures are generally considered safe, some studies have suggested an increase in the occurrence of major malformations and some other complications in babies conceived by ART. Further, it has recently been suggested that ART are associated with imprinting disorders in the offspring such as Beckwith-Wiedemann syndrome and Angelman syndrome. We review the human and animal studies investigating the outcome of ART pregnancies and discuss the potential risk of ART to pre- and perinatal development.

Imprinting disorders and assisted reproductive technology

Worldwide use of assisted reproductive technology (ART) accounts for an estimated 1 to 3% of births. Since 2002, a series of reports have suggested an increased risk of imprinting disorders (Beckwith-Wiedemann syndrome and Angelman syndrome) in children conceived by ART. Definitive conclusions are difficult to substantiate due to the rarity of imprinting disorders and the variability in ART protocols. Despite these limitations, there is biological plausibility for alteration in nongenomic inheritance caused by ART. Animal studies have shown that ART procedures can alter normal imprinting, specifically DNA methylation patterns. Collectively, studies suggest an association between ART and loss of maternal methylation. More recent reports examined a possible association between ART and global hypomethylation of DNA. Three other imprinting disorders (Silver-Russell syndrome, maternal hypomethylation syndrome, and retinoblastoma) have also been implicated, but there is insufficient evidence to establish an association of these syndromes with ART. Based on current evidence, the absolute risk of imprinting disorders after ART remains small and does not warrant routine screening. Large prospective studies are needed to better understand the risks associated with imprinting disorders, imprinting defects, and ART.

Epigenetics and assisted reproduction

PURPOSE OF REVIEW

Epigenetics encompasses multiple mechanisms by which DNA transcription is altered in various tissues and at different times without changing the underlying gene sequence. Epigenetics plays a key role, especially during embryo and trophoblast development. As assisted reproduction technologies (ARTs) are used during these periods, a potential window of vulnerability exists during which epigenetic alterations may occur.

RECENT FINDINGS

Evidence for epigenetic alterations following ARTs was established based on an increased incidence of imprinting disorders, a particular epimutation in gametes. Recent work suggests induced ovulation and oocytes with potentially less stable imprints may contribute to a higher rate of the maternal imprint disorders noted. Alternatively, new findings of imprinting abnormalities in oligospermatic men again raise the question as to whether subfertility itself is associated with epimutations.

SUMMARY

Currently, our understanding of epigenetics and assisted reproduction is incomplete. Further searches for ART infants with imprinting diseases are hampered by their rare nature. Perhaps more importantly attention has turned to understanding imprinting and epigenetics in placental function. Further analysis of placental epimutations may provide insight into the higher rates of adverse outcomes such as growth restriction that follow ARTs.

Does assisted reproductive technology cause birth defects?

PURPOSE OF REVIEW

Observational studies have reported small but increased risk of birth defects associated with assisted reproductive technology (ART) pregnancies. We intend to review the current data on this issue to provide essential information for patient counseling.

RECENT FINDINGS

There is lack of consensus on whether ART per se increases the risk of birth defects, genetic and imprinting disorders, mostly due to the bias inherent to the observational studies, which suggest 30-40% increased risk of birth defects with ART. Recent reports suggest that apparent risks for adverse outcome following ART may be largely related to parental infertility-linked factors. Criteria used to define birth defects bring challenges as well.

SUMMARY

All couples undergoing these procedures should be counseled about the current information suggesting elevated risks of birth defects, genetic abnormalities and imprinting disorders associated with infertility and the infertility treatment with ART. In order to elucidate the controversy whether ART is associated with adverse outcome in the offspring, a multinational collaborative effort is needed, as the required sample size is between 10 000 and 84 000 or more.

Long-term health implications for children conceived by IVF/ICSI

In vitro fertilisation and intra-cytoplasmic sperm injection are well recognised techniques for assisted reproduction, helping over 85% of infertile couples conceive within a year, contributing to over 1% of the annual birth rate in the western world. There is currently limited data on the health of these children in later life as the techniques are relatively new. Certain trends have started to emerge with high order births proving to be responsible for a large proportion of premature and low-birth weight infants. The increased risk of perinatal morbidity and mortality associated with singleton births has been linked to the infertility of the couple rather than the techniques used. This theory has also been suggested to account for the increase in congenital malformations observed. No discrepancies in neurodevelopmental outcome of these children have been established and no detrimental psychological effects on the families have been reported. There has been an increase in childhood illness observed and the future fertility of these children is a major concern for many parents. Further follow up of these children is needed to fully establish the long-term health implications of in vitro fertilisation and intra-cytoplasmic sperm injection.

Genetic and epigenetic characteristics of ICSI children

The outcome of pregnancy and the developmental wellbeing of children conceived from 12,866 consecutive intracytoplasmic sperm injection (ICSI) cycles was assessed. A total of 3277 couples delivered 5891 neonates. There was a higher than normal incidence of de-novo chromosomal abnormalities in a small sample of ICSI offspring. Controlling for maternal age showed that the incidence of low birth weight and gestational length were comparable with the naturally conceived counterpart. Rates of malformation in ICSI offspring ranged from 3.5 to 6.2%. At 3 years of age (n = 811), the proportion of children at risk for developmental delays was 10.4% in ICSI and 10.7% in IVF singletons. However, high order gestations were characterized by 19.4% of the children having compromised development. Epigenetic analysis of assisted reproductive technique conceptuses found minor imprinted gene expression imbalances. ICSI offspring presented with genetic defects that were inherited or arose de novo. Obstetric and neonatal outcomes of singleton pregnancies appeared to be dependent upon maternal age. ICSI and IVF appeared to exert a negative effect on the wellbeing of offspring mainly because of the association with multiple gestations. All assisted reproduction procedures should be monitored for the eventual effect of environmental aggressors on offspring epigenesis.

Malignant conditions in children born after assisted reproductive technology

This article reviews the risks of childhood malignancies and imprinting disorders in children born after assisted reproductive technology (ART). It is recognized that there is a theoretical potential of developing an excess of malignancies in children born after ART. With the advancement and introduction of newer techniques in ART there is an increase in the micromanipulation of gametes and embryos in vitro and extended exposure to the in vitro environment. These include the use of gonadotropins for superovulation, intracytoplasmic sperm injection, blastocyst culture, assisted hatching, and preimplantation genetic diagnosis. Although these approaches aim to enhance pregnancy rates and its outcome, the risk of associated long-term health hazards cannot be disregarded. More recently there is some evidence suggesting a link between ART and epigenetic alterations leading to DNA modifications and imprinting disorders. Two of these genetic imprinting disorders that are known to cause birth defects and childhood malignancies, Beckwith-Wiedmann syndrome and Angelman syndrome have been associated with ART. Systemic reviews of the literature identified published studies, but were unable to identify the precise risks of imprinting disorders and childhood cancers in children conceived with ART. Overall, most studies have not shown any increase in the incidence of childhood cancers after ART. With more women resorting to ART, careful counseling should be offered to all couples especially those requiring intracytoplasmic sperm injection for abnormal sperm parameters.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to distinguish for patients the lack of irrefutable evidence for an increased risk of childhood malignancies in children conceived using assisted reproductive technology (ART), explain potential mechanisms of injury to the gametes and/or embryo during ART which might predispose to childhood illness, and appraise future articles on this topic for credibility both to likelihood of true relationship to possible childhood cancers as well as biologic basis for potential relationship.

Imprinting disorders and assisted reproductive technology

OBJECTIVE

To review currently available literature on the association between imprinting disorders (Beckwith-Wiedemann syndrome [BWS], Angelman syndrome [AS] and retinoblastoma) and assisted reproductive technology (ART) in humans.

DESIGN

Publications related to imprinting/epigenetic disorders including BWS, AS, and retinoblastoma with ART, as well as articles publishing outcome of ART, including IVF and ICSI from July 1978 to February 2008, were identified using PubMed, Medline, and EMBASE.

RESULT(S)

Considerable evidence in animal studies has demonstrated alteration in gene imprinting of embryos cultured in vitro. Publications from Europe, the United States, and Australia have suggested an association between ART and BWS. Importantly, more than 90% of children with BWS that were born after ART had imprinting defects, compared with 40%-50% of children with BWS and conceived without ART. Moreover, there have been other reports suggesting an association between AS and ART. The majority of children with AS born after ART had an imprinting defect as the underlying etiology, specifically loss of methylation of the maternal allele. There was a single report suggesting an increased incidence of retinoblastoma in children conceived with ART.

CONCLUSION(S)

Because the absolute incidence of imprinting disorders is small (<1:12,000 births), routine screening for imprinting disorders in children conceived by ART is not recommended. Additional large cohort studies of children born after ART are needed to determine whether there is a genuine association between ART and imprinting disorders.

Follow-up of children born after ART

Assisted reproductive therapies (ART), namely in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI), have become widely used in the treatment of human infertility. Children conceived using ART represent a substantial proportion of the population. Follow-up of these children is necessary in order to evaluate the risks of infertility treatment upon subsequently conceived offspring. In recent years there has been considerable work in this field. This review summarises current evidence regarding the health of children conceived following ART, encompassing neonatal outcomes, the risk of congenital malformations, neurodevelopmental outcome, physical health, psychosocial well being, and the risk of cancer. The main risks for the future well being of ART children remain multiple pregnancies and low birth weight. Evidence regarding the outcome of singletons born at term following ART is generally reassuring. It is essential that follow-up of ART children continues as they progress through adolescence into adulthood.

Nutrition in early life, and risk of cancer and metabolic disease: alternative endings in an epigenetic tale?

There is substantial evidence which shows that constraints in the early life environment are an important determinant of risk of metabolic disease and CVD. There is emerging evidence that higher birth weight, which reflects a more abundant prenatal environment, is associated with increased risk of cancer, in particular breast cancer and childhood leukaemia. Using specific examples from epidemiology and experimental studies, this review discusses the hypothesis that increased susceptibility to CVD, metabolic disease and cancer have a common origin in developmental changes induced in the developing fetus by aspects of the intra-uterine environment including nutrition which involve stable changes to the epigenetic regulation of specific genes. However, the induction of specific disease risk is dependent upon the nature of the environmental challenge and interactions between the susceptibility set by the altered epigenome and the environment throughout the life course.

Effects of ooplasm manipulation on DNA methylation and growth of progeny in mice

New techniques to boost male and female fertility are being pioneered at a rapid pace in fertility clinics to increase the efficiency of assisted reproduction methods in couples in which natural conception has not been achieved. This study investigates the possible epigenetic effects of ooplasm manipulation methods on postnatal growth and development using a mouse genetic model, with particular emphasis on the possible effects of intergenotype manipulations. We performed interstrain and control intrastrain maternal pronuclear transfers, metaphase-II spindle transfers, and ooplasm transfer between C57BL/6 and DBA/2 mice, and found no major, long-term growth defects or epigenetic abnormalities, in either males or females, associated with intergenotype transfers. Ooplasm transfer itself was associated with reduced viability, and additional subtle effects of ooplasm strain of origin were observed. Both inter- and intrastrain ooplasm transfer were associated with subtle, transient effects on growth early in life. We also performed inter- and intrastrain germinal vesicle transfers (GVTs). Interstrain GVT females, but not males, had significantly lower body weights at birth and thereafter compared with the intrastrain GVT and non-GVT controls. No GVT-associated changes were observed in DNA methylation of the Mup1, Rasgrf1, H19, Snrpn, or Peg3 genes, nor any difference in expression of the imprinted Rasgrf1, Igf2r, or Mest genes. These results indicate that some ooplasm manipulation procedures may exert subtle effects on growth early in life, while intergenotype GVT can result in significant growth deficiencies after birth.

Low frequency of imprinting defects in ICSI children born small for gestational age

Although there is an increased frequency of low birth weight after assisted reproduction, the mechanisms underlying this association are unclear. We have proposed that some of the children conceived by intracytoplasmic sperm injection (ICSI) with low birth weight might have an epimutation (faulty methylation pattern) in one of the imprinted genes involved in fetal growth control, eg, KCNQ1OT1, PEG1, PEG3, GTL2, IGF2/H19 and PLAGL1. Using bisulfite DNA sequencing and sequence-based quantitative methylation analysis (SeQMA), we determined the methylation pattern of these genes in buccal smears from 19 ICSI children born small for gestational age (SGA, birth weight <3rd percentile) and from 29 term-born normal weight children after spontaneous conception. We detected clear hypermethylation of KCNQ1OT1 and borderline hypermethylation of PEG1 in one and the same ICSI child. The other children and the parents of the affected child have normal methylation patterns. Imprinting defects appear to be a rare finding in ICSI children born SGA. Methylation of the paternal KCNQ1OT1 and PEG1 alleles may be a previously unrecognized cause of SGA. The epimutations found in the SGA child, whose father had oligozoospermia, probably result from an imprint erasure defect in the paternal germ line and therefore appear to be linked to the fertility problem of the father and not to in vitro fertilization/ICSI.

[Parental imprinting related to Assisted Reproductive Technologies]

Until the introduction of Assisted Reproductive Technologies (ART), many studies were conducted in order to evaluate their impact upon the children's health born in such a way. The epigenetic-risk notion was invoked and a link between ART and diseases associated with imprinting alterations was suggested with different examples, such as Beckwith-Wiedemann syndrome (BWS), Angelman syndrome (AS) and Silver-Russell syndrome (SRS). The epigenetic "life cycle" of imprinting (germline erasure, germline establishment, and somatic maintenance) concerns all the phases from gametogenesis, gamete maturation, fertilization, to early embryo development and appears particularly vulnerable to perturbations induced by superovulation, in vitro fertilization, embryo culture and embryo transfer. The studies, performed in model animal, provide a basis of the understanding of imprinting alterations induced by the ART and clinically useful information in order to improve the ART.

Epigenetic consequences of assisted reproduction and infertility on the human preimplantation embryo

Epigenetic information, which is essential for normal mammalian development, is acquired during gametogenesis and further regulated during preimplantation development. The epigenetic consequences of assisted reproductive technologies (ARTs) and infertility on the health and quality of the human preimplantation embryo are considered in this review. In the zygote, the epigenetic information that is inherited from the sperm and the oocyte intersects and must be appropriately recognized, regulated and then propagated during preimplantation development so as to regulate gene expression in an appropriate manner. A growing body of evidence suggests that ARTs and/or infertility itself may affect these complex processes leading to epigenetic diseases that include disorders of genomic imprinting. The epigenetic safety of human gametes and embryos is of paramount importance. Unfortunately, morphological methods of assessing embryo quality are incapable of detecting epigenetic errors. Further research is therefore critical to resolve these issues.

A review of known imprinting syndromes and their association with assisted reproduction technologies

An association between assisted reproduction technologies (ART) and abnormal genomic imprinting in humans has been recognized for several years; however, the magnitude of this risk and the spectrum of imprinting syndromes to which the risk applies remains unknown. Nine human imprinting syndromes have been identified but current evidence links ART with only three: Beckwith-Wiedemann syndrome, Angelman syndrome and the newly described maternal hypomethylation syndrome. There is currently a lack of evidence linking ART with the remaining six imprinting syndromes: Prader-Willi syndrome, Russell-Silver syndrome, maternal and paternal uniparental disomy of chromosome 14, pseudohypoparathyroidism type 1b and transient neonatal diabetes. Evidence from clinical reports suggests that the association between imprinting syndromes and ART may be restricted to syndromes where the imprinting change takes the form of hypomethylation on the maternal allele. In contrast, studies of gametes and early embryos suggest that ART can be associated with hypermethylation as well as hypomethylation, with imprinting changes occurring on paternal as well as maternal alleles. The health effects of ART-associated imprinting changes may also extend beyond the nine recognized imprinting syndromes.

The road to pluripotence: the research response to the embryonic stem cell debate

The controversies surrounding embryonic stem cell research have prompted scientists to invent beyond restrictive national policy and moral concerns. The impetus behind these reports comes from different sources, including individually held moral beliefs, societal pressures and resource constraints, both biological and financial. Along with other contributions to public policy such as advocacy or public testimony, experimentation and scientific curiosity are perhaps more natural responses scientists use to surmount impediments to research. In a research context, we review the history of the first stem cell discoveries, and describe scientific efforts leading up to recent reports of pluripotent lines made without the use of human embryos and eggs. We argue that despite the promise of these new lines, we must not lose sight of fundamental questions remaining at the frontiers of embryology and early human development. The answers to these questions will impact studies of genetics, cell biology and diseases such as cancer, autoimmunity and disorders of development. Human embryonic stem cell research is barely a decade old. The recent pace of discovery--in spite of federal restrictions--is testament to the potential of these cells to uncover some of biology's most intractable mysteries.

Maternal and zygotic Dnmt1 are necessary and sufficient for the maintenance of DNA methylation imprints during preimplantation development

Parental origin-specific DNA methylation regulates the monoallelic expression of the mammalian imprinted genes. The methylation marks or imprints are established in the parental germline and maintained throughout embryonic development. However, it is unclear how the methylation imprints are maintained through extensive demethylation in cleavage-stage preimplantation embryos. Previous reports suggested that DNA methyltransferase(s) other than Dnmt1 is involved in the maintenance of the imprints during cleavage. Here we demonstrate, by using conditional knockout mice, that the other known DNA methyltransferases Dnmt3a and Dnmt3b are dispensable for the maintenance of the methylation marks at most imprinted loci. We further demonstrate that a lack of both maternal and zygotic Dnmt1 results in complete demethylation of all imprinted loci examined in blastocysts. Consistent with these results we find that zygotic Dnmt1 is expressed in the preimplantation embryo. Thus, contrary to the previous reports, Dnmt1 alone is sufficient to maintain the methylation marks of the imprinted genes.

Epigenetic regulation during mammalian oogenesis

The advent of the epigenetic era has sparked a new frontier in molecular research and the understanding of how development can be regulated beyond direct alterations of the genome. Thus far, the focal point of epigenetic regulation during development has been chromatin modifications that control differential gene expression by DNA methylation and histone alterations. But what of events that alter gene expression without direct influence on the DNA itself? The present review focuses on epigenetic pathways regulating development from oogenesis to organogenesis and back that do not involve methylation of cytosine in DNA. We discuss target components of epigenetic modification such as organelle development, compartmentalisation of maternal factors and molecular mediators in the oocyte and how these factors acting during oogenesis impact on later development. Epigenetic regulation of development, be it via cytosine methylation or not, has wide-ranging effects on the subsequent success of a pregnancy and the intrinsic health of offspring. Perturbations in epigenetic regulation have been clearly associated with disease states in adult offspring, including Type II diabetes, hypertension, cancers and infertility. A clear understanding of all epigenetic mechanisms is paramount when considering the increased use of assisted reproductive techniques and the risks associated with their use.

Multiple orofacial malformations in a boy who was conceived by intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) and other assisted reproductive technologies (ART) are effective treatments for infertility and are widely used at infertility clinics. Although ICSI is generally considered safe, some studies have suggested an excess occurrence of major birth defects resulting from the procedure. Here, we present a rare case of a boy with multiple orofacial malformations who was conceived by ICSI. We suggest therefore that the risk of genetics abnormalities should be discussed in detail with the parents and sufficient informed consent should be obtained before starting ICSI procedures.

Elective cryopreservation of all day 5 blastocysts is more effective than using day 6 blastocysts for improving pregnancy outcome in stimulated cycles

Aim:  To evaluate the efficacy of cryopreservation of all blastocysts for future transfers in stimulated cycles. Methods:  We carried out fresh blastocyst transfer cycles on day 5 (n = 290) or day 6 (n = 119) and thawed blastocyst transfer cycles that were frozen on day 5 (n = 136), day 6 (n = 71) or day 6 electively (n = 21). We retrospectively compared the clinical outcome of fresh blastocyst transfers with thawed blastocyst transfers according to the day of blastocyst transfer or freezing. Results:  The clinical implantation rates in women with stimulated cycles were significantly higher after the transfer of thawed blastocysts compared with the transfer of fresh blastocysts (day 5, P < 0.0005; day 6, P < 0.00005). Although the implantation rate of fresh day 6 transfer cycles was lower than that of elective day 6 frozen-thawed cycles, this difference was not statistically significant (P = 0.17). Conclusions:  Thawed blastocysts demonstrated a better potential for implantation when compared with fresh blastocysts in stimulated cycles. We concluded that elective cryopreservation of all blastocysts on day 5 is an effective option to improve the clinical outcome in stimulated cycles. Additionally, with cryopreservation of all day 6 blastocysts, the implantation rates of first embryo transfers may increase by allowing the best-quality blastocysts to be transferred in thawed cycles. (Reprod Med Biol 2008; 7: 75-83).

Growth retardation versus overgrowth: Silver-Russell syndrome is genetically opposite to Beckwith-Wiedemann syndrome

Human growth is a complex process that requires the appropriate interaction of many players. Central members in the growth pathways are regulated epigenetically and thereby reflect the profound significance of imprinting for correct mammalian ontogenesis. In this review, we show that the growth retardation disorder Silver-Russell syndrome (SRS) is a suitable model to decipher the role of imprinting in growth. As we will show, SRS should not only be regarded as the genetically (and clinically) opposite disease to Beckwith-Wiedemann syndrome, but it also represents the first human disorder with imprinting disturbances that affect two different chromosomes (i.e. chromosomes 7 and 11). Thus, a functional interaction between factors encoded by chromosomes 7 and 11 is likely.

Role of epigenetics in mental disorders

The purpose of this paper was to selectively review the literature on the role of epigenetics in mental illnesses. Aberrant epigenetic regulation has been clearly implicated in the aetiology of some human illnesses. In recent years a growing body of evidence has highlighted the possibility that epigenetics may also play a key role in the origins and expression of mental disorders. Epigenetic phenomena may help explain some of the complexity of mental illnesses and provide a basis for discovering novel pharmacological targets to treat these disorders.

The risk of malformation following assisted reproduction

INTRODUCTION

Intracytoplasmatic sperm injection (ICSI) is currently the most frequently used human reproductive technology in Germany. ICSI was introduced as routine, insurance-funded medical care in 2002 by the Federal Joint Committee. A re-evaluation of published literature on malformation rates in children born of ICSI pregnancies within a period of three years formed part of the committee's decision. The analysis investigated whether ICSI increases the risk of malformation in the offspring, compared to in vitro fertilization (IVF) and natural conception.

METHODS

Systematic literature review.

RESULTS

929 studies were identified. Three meta-analyses, 15 studies investigating malformations, and 12 studies analyzing imprinting disorders were included. The risk of malformation was not significantly different in nine studies comparing ICSI versus IVF. Two meta-analyses and three of eight cohort studies and retrospective analysis showed significantly more severe malformations after assisted reproduction than after natural conception. The remaining five studies displayed no significant results. Current evidence does not show a higher risk of major malformations in the offspring resulting from the use of ICSI compared to IVF. However, there is evidence that both techniques increase the risk for major malformations considerably, compared to natural conception, and further research is needed. The validity of the results is low since the studies were heterogeneous and the cohorts used in the studies had limited comparability.

Growth and development of children born after in vitro fertilization

OBJECTIVE

To evaluate growth and development of children born after IVF treatment.

DESIGN

Literature review.

CONCLUSION(S)

At present there is substantial evidence that children born after IVF are at increased risk for adverse perinatal outcome, congenital malformations, and rare epigenetic defects. It is still unclear whether observed health problems originate from the IVF procedure itself or the underlying subfertility problems of the parents. Current follow-up studies regarding postnatal growth and morbidity rates are scarce with conflicting results and other areas of long-term research in children born after IVF are still in its infancy. The importance of the worldwide continuing monitoring of children born after IVF to investigate potential long-term consequences including the development of cardiovascular diseases is therefore highlighted.

Epigenetic epidemiology of the developmental origins hypothesis

Extensive human epidemiologic and animal model data indicate that during critical periods of prenatal and postnatal mammalian development, nutrition and other environmental stimuli influence developmental pathways and thereby induce permanent changes in metabolism and chronic disease susceptibility. The biologic mechanisms underlying this "developmental origins hypothesis" are poorly understood. This review focuses on the likely involvement of epigenetic mechanisms in the developmental origins of health and disease (DOHaD). We describe permanent effects of transient environmental influences on the developmental establishment of epigenetic gene regulation and evidence linking epigenetic dysregulation with human disease. We propose a definition of "epigenetic epidemiology" and delineate how this emerging field provides a basis from which to explore the role of epigenetic mechanisms in DOHaD. We suggest strategies for future human epidemiologic studies to identify causal associations between early exposures, long-term changes in epigenetic regulation, and disease, which may ultimately enable specific early-life interventions to improve human health.

Assisted Reproductive Technology affects developmental kinetics, H19 Imprinting Control Region methylation and H19 gene expression in individual mouse embryos

BACKGROUND

In the last few years, an increase in imprinting anomalies has been reported in children born from Assisted Reproductive Technology (ART). Various clinical and experimental studies also suggest alterations of embryo development after ART. Therefore, there is a need for studying early epigenetic anomalies which could result from ART manipulations, especially on single embryos. In this study, we evaluated the impact of superovulation, in vitro fertilization (IVF) and embryo culture conditions on proper genomic imprinting and blastocyst development in single mouse embryos. In this study, different experimental groups were established to obtain embryos from superovulated and non-superovulated females, either from in vivo or in vitro fertilized oocytes, themselves grown in vitro or not. The embryos were cultured either in M16 medium or in G1.2/G2.2 sequential medium. The methylation status of H19 Imprinting Control Region (ICR) and H19 promoter was assessed, as well as the gene expression level of H19, in individual blastocysts. In parallel, we have evaluated embryo cleavage kinetics and recorded morphological data.

RESULTS

We show that: 1. The culture medium influences early embryo development with faster cleavage kinetics for culture in G1.2/G2.2 medium compared to M16 medium. 2. Epigenetic alterations of the H19 ICR and H19 PP are influenced by the fertilization method since methylation anomalies were observed only in the in vitro fertilized subgroup, however to different degrees according to the culture medium. 3. Superovulation clearly disrupted H19 gene expression in individual blastocysts. Moreover, when embryos were cultured in vitro after either in vivo or in vitro fertilization, the percentage of blastocysts which expressed H19 was higher in G1.2/G2.2 medium compared to M16.

CONCLUSION

Compared to previous reports utilizing pools of embryos, our study enables us to emphasize a high individual variability of blastocysts in the H19 ICR and H19 promoter methylation and H19 gene expression, with a striking effect of each manipulation associated to ART practices. Our results suggest that H19 could be used as a sensor of the epigenetic disturbance of the utilized techniques.

A survey of assisted reproductive technology births and imprinting disorders

BACKGROUND

Genomic imprinting is an epigenetic process in which allele-specific gene expression is dependent on the parental inheritance. Although only a minority of human genes are imprinted, those that have been identified to date have been preferentially implicated in prenatal growth and neurodevelopment. Mutations or epimutations in imprinted genes or imprinting control centres are associated with imprinting disorders such as Angelman syndrome (AS) and Beckwith-Wiedemann syndrome (BWS). Recently, an increased frequency of assisted reproductive technology (ART) conceptions has been reported in children with BWS and AS. However, the risk of imprinting disorders in ART children is unknown.

METHODS

We undertook a survey of 2492 children born after ART in the Republic of Ireland and Central England with the aim of detecting cases (both clinically diagnosed and previously unrecognized) of BWS and AS in this cohort. The response rate to an initial questionnaire was 61%, corresponding to data for 1524 children. After evaluation of the questionnaire, 70 children were invited for a detailed clinical assessment, and 47 accepted (response rate of 67%).

RESULTS

In this entire cohort, we detected one case of BWS and no cases of AS. We did not find evidence that there exists a significant group of ART children with unrecognized milder forms of AS or BWS.

CONCLUSIONS

Although previous studies have suggested an increased relative risk of BWS and AS after ART, our findings suggest that the absolute risk of imprinting disorders in children conceived by ART is small (<1%). Precise risk estimates of risk are difficult to define because of the rarity of the conditions and incomplete response rates to the questionnaire and clinical examination invitations. Hence further investigations are indicated to (i) refine the absolute and relative risks of imprinting disorders after ART and (ii) ensure that changes in ART protocols are not associated with increased frequencies of epigenetic changes and imprinting disorders in children born after ART.

In vitro spermatogenesis as a method to bypass pre-meiotic or post-meiotic barriers blocking the spermatogenetic process: genetic and epigenetic implications in assisted reproductive technology

Pregnancies achieved by assisted reproduction technologies and particularly by ooplasmic injections of either in vivo or in vitro generated immature male germ cells are susceptible to genetic risks inherent to the male population treated with assisted reproduction and additional risks inherent to these innovative procedures. The documented, as well as the theoretical risks, are discussed in this review. These risks represent mainly the consequences of genetic abnormalities underlying male infertility and may become stimulators for the development of novel approaches and applications in the treatment of infertility. Recent data suggest that techniques employed for in vitro spermatogenesis, male somatic cell haploidization, stem cell differentiation in vitro and assisted reproductive technology may also affect the epigenetic characteristics of the male gamete, the female gamete, or may have an impact on early embryogenesis. They may be also associated with an increased risk for genomic imprinting abnormalities. Production of haploid male gametes in vitro may not allow the male gamete to undergo all the genetic and epigenetic alterations that the male gamete normally undergoes during in vivo spermatogenesis.

Manipulations of mouse embryos prior to implantation result in aberrant expression of imprinted genes on day 9.5 of development

In vitro culture of mouse embryos results in loss of imprinting. The aim of the present study was to examine how two of the techniques commonly used during assisted reproduction, namely embryo culture and embryo transfer, affect genomic imprinting after implantation in the mouse. F1 hybrid mouse embryos were subjected to three experimental conditions: control (unmanipulated), embryo transfer and in-vitro-culture followed by embryo transfer. Concepti were collected on d9.5 of development and allelic expression determination of ten imprinted genes (H19, Snrpn, Igf2, Kcnq1ot1, Cdkn1c, Kcnq1, Mknr3, Ascl2, Zim1, Peg3) was performed. Although control concepti had monoallelic imprinted gene expression in all tissues, both manipulated groups had aberrant expression of one or more imprinted genes in the yolk sac and placenta. Culture further exacerbated the effects of transfer by increasing the number of genes with aberrant allelic expression in extraembryonic, as well as embryonic tissues. Additionally, placentae of both groups of manipulated concepti exhibited reduced levels of Igf2 mRNA and increased levels of Ascl2 mRNA when compared with their unmanipulated counterparts. Furthermore, we show that biallelic expression of Kcnq1ot1 coincided with loss of methylation on the maternal allele of the KvDMR1 locus, a phenotype often associated with the human syndrome Beckwith-Wiedemann. In conclusion, our results show that even the most basic manipulation used during human-assisted reproduction, namely, embryo transfer, can lead to misexpression of several imprinted genes during post-implantation development. Additionally, our results serve as a cautionary tale for gene expression studies in which embryo transfer is used.

Aberrant DNA methylation of imprinted loci in sperm from oligospermic patients

Recent studies suggest that assisted reproductive technologies (ART), which involve the isolation, handling and culture of gametes and early embryos, are associated with an increased incidence of rare imprinting disorders. Major epigenetic events take place during this time and the process of ART may expose the epigenome to external influences, preventing the proper establishment and maintenance of genomic imprints. However, the risks of ART cannot be simply evaluated because the patients who receive ART may differ both demographically and genetically from the general population at reproductive age. In this study, we examined the DNA methylation status of seven imprinted genes using a combined bisulphite-PCR restriction analysis and sequencing technique on sperm DNA obtained from 97 infertile men. We found an abnormal paternal methylation imprint in 14 patients (14.4%) and abnormal maternal imprint in 20 patients (20.6%). The majority of these doubly defective samples were in men with moderate or severe oligospermia. These abnormalities were specific to imprinted loci as we found that global DNA methylation was normal in these samples. The outcome of ART with sperm shown to have an abnormal DNA methylation pattern was generally poor. However, one sample of sperm with both paternal and maternal methylation errors used in ICSI produced a child of normal appearance without any abnormalities in their imprinted methylation pattern. Our data suggest that sperm from infertile patients, especially those with oligospermia, may carry a higher risk of transmitting incorrect primary imprints to their offspring, highlighting the need for more research into ART.

Pregnancy outcomes after assisted reproductive technology

OBJECTIVE

To review the effect of assisted reproductive technology (ART) on perinatal outcomes, to provide guidelines to optimize obstetrical management and counselling of Canadian women using ART, and to identify areas specific to birth outcomes and ART requiring further research.

OPTIONS

Perinatal outcomes of ART pregnancies in subfertile women are compared with those of spontaneously conceived pregnancies. Perinatal outcomes are compared between different types of ART.

OUTCOMES

This guideline discusses the adverse outcomes that have been recorded in association with ART, including obstetrical complications, adverse perinatal outcomes, multiple gestations, structural congenital abnormalities, chromosomal abnormalities, imprinting disorders, and childhood cancer.

EVIDENCE

The Cochrane Library and MEDLINE were searched for English-language articles from 1990 to February 2005, relating to assisted reproduction and perinatal outcomes. Search terms included assisted reproduction, assisted reproductive technology, ovulation induction, intracytoplasmic sperm injection (ICSI), embryo transfer, and in vitro fertilization (IVF). Additional publications were identified from the bibliographies of these articles as well as the Science Citation Index. Studies assessing gamete intrafallopian transfer (GIFT) and zygote intrafallopian transfer (ZIFT) were excluded since they are rarely used in Canada. All study types were reviewed. Randomized controlled trials were considered evidence of the highest quality, followed by cohort studies. Key studies and supporting data for each recommendation are summarized with evaluative comments and referenced.

VALUES

The evidence collected was reviewed by the Genetics Committee and the Reproductive Endocrinology Infertility Committee of the Society of Obstetricians and Gynaecologists of Canada (SOGC) and quantified using the Evaluation of Evidence Guidelines developed by the Canadian Task Force on the Periodic Health Examination.

BENEFITS, HARMS, AND COSTS

The type and magnitude of benefits, harms, and costs expected for patients from guideline implementation. This guideline has been reviewed by the Genetics Committee and the Reproductive Endocrinology and Infertility Committee, and approved by the Executive and Council of the Society of Obstetricians and Gynaecologists of Canada and the Board of the Canadian Fertility and Andrology Society.

RECOMMENDATIONS

1. Spontaneous pregnancies in untreated infertile women may be at higher risk for obstetrical complications and perinatal mortality than spontaneous pregnancies in fertile women. Further research is required to clarify the contribution of infertility itself to adverse obstetrical and perinatal outcomes. (II-2A) 2. All men with severe oligozoospermia or azoospermia should be offered genetic/clinical counselling for informed consent and offered karyotyping for chromosomal abnormalities before attempting IVF-ICSI. They should be made aware of the availability of tests for Y chromosome microdeletion. Some patients may consider the option of donor insemination. (II-3B) 3. Couples exploring IVF-ICSI when the man has obstructive azoospermia should be offered genetic/clinical counselling for informed consent and offered genetic testing for alterations in genes associated with cystic fibrosis (CF) before attempting IVF-ICSI. (II-2A) 4. Pregnancies achieved by ovarian stimulation with gonadotropins and intrauterine insemination are at higher risk for perinatal complications, and close surveillance during pregnancy should be considered. It remains unclear if these increased risks are attributable to the underlying infertility, characteristics of the infertile couple, or use of assisted reproductive techniques. Multiple gestations remain a significant risk of gonadotropin treatment. (II-2A) 5. Pregnancies achieved by IVF with or without ICSI are at higher risk for obstetrical and perinatal complications than spontaneous pregnancies, and close surveillance during pregnancy should be considered. It remains unclear if these increased risks are attributable to the underlying infertility, characteristics of the infertile couple, or use of assisted reproductive techniques. (II-2A) 6. Women undergoing ART should be informed about the increased rate of obstetrical interventions such as induced labour and elective Caesarean delivery. (II-2A) 7. Couples suffering from infertility who are exploring treatment options should be made aware of the psychosocial implications of ART. Further research into the psychosocial impact of ART is needed. (II-2A) 8. Singleton pregnancies achieved by assisted reproduction are at higher risk than spontaneous pregnancies for adverse perinatal outcomes, including perinatal mortality, preterm delivery, and low birth weight, and close surveillance during pregnancy should be available as needed. (II-2A) 9. A significant risk of ART is multiple pregnancies. Infertile couples need to be informed of the increased risks of multifetal pregnancies. Although dichorionic twins are most common, the incidence of monochorionic twins is also increased. Risks of multiple pregnancies include higher rates of perinatal mortality, preterm birth, low birth weight, gestational hypertension, placental abruption, and placenta previa. Perinatal mortality in assisted conception twin pregnancies appears to be lower than in spontaneously conceived twin pregnancies. (II-2A) 10. When multifetal reduction is being considered for high-order multiple pregnancies, psychosocial counselling should be readily available. Careful surveillance for fetal growth problems should be undertaken after multifetal reduction. (II-2A) 11. To reduce the risks of multiple pregnancies associated with ART and to optimize pregnancy rates, national guidelines should be developed on the number of embryos replaced according to characteristics such as patient's age and grade of embryos. (II-2A) 12. Further epidemiologic and basic science research is needed to help determine the etiology and extent of the increased risks to childhood and long-term growth and development associated with ART. (II-2A) 13. Discussion of options for prenatal screening for congenital structural abnormalities in pregnancies achieved by ART is recommended, including appropriate use of biochemical and sonographic screening. (II-2A) 14. Further epidemiologic and basic science research is needed to help determine the etiology and extent of the increased risks of congenital abnormalities associated with ART. (II-2A) 15. Couples considering IVF-ICSI for male-factor infertility should receive information, and if necessary formal genetic counselling, about the increased risk of de novo chromosomal abnormalities (mainly sex chromosomal anomalies) associated with their condition. Prenatal diagnosis by chorionic villus sampling (CVS) or amniocentesis should be offered to these couples if they conceive. (II-2A) 16. Further epidemiologic and basic science research is needed to help determine the etiology and extent of the increased risks of chromosomal abnormalities associated with ART. (II-2A) 17. Discussion of options for prenatal screening and testing for aneuploidy in pregnancies achieved by ART, adapted for maternal age and number of fetuses, is recommended, including appropriate use of biochemical and sonographic screening. (II-2A) 18. The precise risks of imprinting and childhood cancer from ART remain unclear but cannot be ignored. Further clinical research, including long-term follow-up, is urgently required to evaluate the prevalence of imprinting disorders and cancers associated with ART. (II-2A) 19. The clinical application of preimplantation genetic diagnosis must balance the benefits of avoiding disease transmission with the medical risks and financial burden of in vitro fertilization. Further ethical discussion and clinical research is required to evaluate appropriate indications for preimplantation genetic diagnosis. (III-B).