Increased risk of Silver-Russell syndrome after in vitro fertilization?

Silver-Russell Syndrome and Beckwith-Wiedemann Syndrome: Opposite Phenotypes with Heterogeneous Molecular Etiology

Silver-Russell syndrome (SRS) and Beckwith-Wiedemann syndrome (BWS) are 2 clinically opposite growth-affecting disorders belonging to the group of congenital imprinting disorders. The expression of both syndromes usually depends on the parental origin of the chromosome in which the imprinted genes reside. SRS is characterized by severe intrauterine and postnatal growth retardation with various additional clinical features such as hemihypertrophy, relative macrocephaly, fifth finger clinodactyly, and triangular facies. BWS is an overgrowth syndrome with many additional clinical features such as macroglossia, organomegaly, and an increased risk of childhood tumors. Both SRS and BWS are clinically and genetically heterogeneous, and for clinical diagnosis, different diagnostic scoring systems have been developed. Six diagnostic scoring systems for SRS and 4 for BWS have been previously published. However, neither syndrome has common consensus diagnostic criteria yet. Most cases of SRS and BWS are associated with opposite epigenetic or genetic abnormalities in the 11p15 chromosomal region leading to opposite imbalances in the expression of imprinted genes. SRS is also caused by maternal uniparental disomy 7, which is usually identified in 5-10% of the cases, and is therefore the first imprinting disorder that affects 2 different chromosomes. In this review, we describe in detail the clinical diagnostic criteria and scoring systems as well as molecular causes in both SRS and BWS.

Imprinting methylation errors in ART

There has been an increase in incidence reports of rare imprinting disorders associated with assisted reproductive technology (ART). ART, including in vitro fertilization and intracytoplasmic sperm injections, is an important treatment for infertile people of reproductive age and increasingly produces children. The identification of epigenetic changes at imprinted loci in ART infants has led to the suggestion that ART techniques themselves may predispose embryos to acquire imprinting errors and diseases. In this review, we note that the particular steps of ART may be prone to induction of imprinting methylation errors during gametogenesis, fertilization and early embryonic development. In addition, we explain imprint-associated diseases and their causes. Moreover, from a Japanese nationwide epidemiological study of imprint-associated diseases, we determine their associations with ART. Epigenetic studies will be required to understand the pathogenesis, ART-related risk factor(s) and what precautions can be taken to prevent the occurrence of input methylation errors. We hope that the constitution of children born after each ART procedure will reveal the safest and most ethical approach to use, which will be invaluable for the future development of standard ART.

Silver-Russell syndrome due to paternal H19/IGF2 hypomethylation in a twin girl born after in vitro fertilization

Silver–Russell syndrome (SRS) is a clinically and genetically heterogeneous syndrome characterized by severe intrauterine and postnatal growth retardation, facial dysmorphism and body asymmetry. One of the main molecular mechanisms leading to the syndrome involves methylation abnormalities of chromosome 11p15. In the last decades, an increase of imprinting disorders have been reported in children born from assisted reproductive technology (ART); however there is currently little evidence linking SRS and ART. Only few infants with SRS born using ART, supported by molecular analysis, have been described. We report on a twin-girl conceived using intracytoplasmic sperm injection (ICSI) diagnosed with SRS. Molecular studies revealed a hypomethylation of the paternal H19/IGF2 Imprinting Control Region. Her twin sister had a normal prenatal and postnatal growth and a normal methylation pattern of the chromosome 11p15. This is the second reported case of a twin infant with SRS conceived using ART with hypomethylation of H19/IGF2; it provides additional evidence of a possible relationship between ART procedures and methylation defects observed in SRS. Given the clinical heterogeneity of SRS, and the increased risk of multiple and preterm births in the ART-conceived children, it is possible that a number of cases of SRS remains undiagnosed in this population. Future studies should investigate the possible link between ART and SRS, in order to better understand the causes of epimutations in ART pregnancies, and to help clinicians to adequately counsel parents who approach to ART and to assess the opportunity of a long-term follow-up of children conceived using ART. © 2013 Wiley Periodicals, Inc.

Role of ART in imprinting disorders

Assisted reproductive technologies (ART) offer revolutionary infertility treatments for millions of childless couples around the world. Currently, ART accounts for 1 to 3% of annual births in industrialized countries and continues to expand rapidly. Except for an increased incidence of premature births, these technologies are considered safe. However, new evidence published during the past decade has suggested an increased incidence of imprinting disorders in children conceived by ART. Specifically, an increased risk was reported for Beckwith-Wiedemann syndrome (BWS), Angelman syndrome (AS), Silver-Russell syndrome, and retinoblastoma. In contrast, some studies have found no association between ART and BWS, AS, Prader-Willi syndrome, transient neonatal diabetes mellitus, and retinoblastoma. The variability in ART protocols and the rarity of imprinting disorders complicate determining the causative relationship between ART and an increased incidence of imprinting disorders. Nevertheless, compelling experimental data from animal studies also suggest a link between increased imprinting disorders and ART. Further comprehensive, appropriately powered studies are needed to better address the magnitude of the risk for ART-associated imprinting disorders. Large longitudinal studies are particularly critical to evaluate long-term effects of ART not only during the perinatal period but also into adulthood. An important consideration is to determine if the implicated association between ART and imprinting disorders is actually related to the procedures or to infertility itself.

Similar DNA methylation levels in specific imprinting control regions in children conceived with and without assisted reproductive technology: a cross-sectional study

Background

While a possible link between assisted reproductive technology (ART) and rare imprinting disorders has been found, it is not clear if this is indicative of subtler disruptions of epigenetic mechanisms. Results from previous studies have been mixed, but some methylation differences have been observed.

Methods

Children conceived through ART and children conceived spontaneously were recruited for this cross-sectional study. Information about reproductive history, demographic factors, birth characteristics, and infertility treatment was obtained from maternal interview and medical records. Peripheral blood lymphocytes and buccal cell samples were collected from participating children. Methylation analysis was performed on five loci using pyrosequencing. Statistical analysis of methylation differences was performed using linear regression with generalized estimating equations. Results are reported as differences with 95% confidence intervals (CI).

Results

A total of 67 ART children and 31 spontaneously conceived (SC) children participated. No significant difference in methylation in lymphocyte samples was observed between groups for any loci. Possible differences were found in buccal cell samples for IGF2 DMR0 (Difference: 2.07; 95% confidence interval (CI): -0.28, 4.42; p = 0.08) and IGF2R (Difference: -2.79; 95% CI: -5.74, 0.16; p = 0.06). Subgroup analysis indicated potential lower methylation in those whose parents used ART for unexplained infertility.

Conclusions

Observed differences in methylation between the ART and SC groups were small for all loci in the two sample types examined and no statistical differences were observed. It is still unclear whether or not small differences observed in several studies represent a real difference between groups and if this difference is biologically meaningful. Larger studies with long term follow-up are needed to fully answer these questions.

Assisted reproduction treatment and epigenetic inheritance

BACKGROUND

The subject of epigenetic risk of assisted reproduction treatment (ART), initiated by reports on an increase of children with the Beckwith–Wiedemann imprinting disorder, is very topical. Hence, there is a growing literature, including mouse studies.

METHODS

In order to gain information on transgenerational epigenetic inheritance and epigenetic effects induced by ART, literature databases were searched for papers on this topic using relevant keywords.

RESULTS

At the level of genomic imprinting involving CpG methylation, ART-induced epigenetic defects are convincingly observed in mice, especially for placenta, and seem more frequent than in humans. Data generally provide a warning as to the use of ovulation induction and in vitro culture. In human sperm from compromised spermatogenesis, sequence-specific DNA hypomethylation is observed repeatedly. Transmittance of sperm and oocyte DNA methylation defects is possible but, as deduced from the limited data available, largely prevented by selection of gametes for ART and/or non-viability of the resulting embryos. Some evidence indicates that subfertility itself is a risk factor for imprinting diseases. As in mouse, physiological effects from ART are observed in humans.

In the human, indications for a broader target for changes in CpG methylation than imprinted DNA sequences alone have been found. In the mouse, a broader range of CpG sequences has not yet been studied. Also, a multigeneration study of systematic ART on epigenetic parameters is lacking.

CONCLUSIONS

The field of epigenetic inheritance within the lifespan of an individual and between generations (via mitosis and meiosis, respectively) is growing, driven by the expansion of chromatin research. ART can induce epigenetic variation that might be transmitted to the next generation.

Genetic variant in the promoter of connective tissue growth factor gene confers susceptibility to nephropathy in type 1 diabetes

BACKGROUND The evidence for genetic susceptibility in the pathogenesis of diabetic nephropathy is well recognised, but the genes involved remain to be identified. It is hypothesised that mutations within the gene encoding connective tissue growth factor (CTGF/CCN2) will increase the propensity of diabetic subjects to develop nephropathy. METHODS AND RESULTS Genomic screening was performed for single nucleotide polymorphisms (SNPs) within the CTGF gene in 862 subjects from the DCCT/EDIC cohort of type 1 diabetes. A novel SNP was identified in the promoter region that changes a C-G at the position -20. The frequency of GG genotype in microalbuminuric patients (albumin excretion rate (AER) >40 mg/24 h) is significantly greater than diabetics with AER <40 mg/24 h, p<0.0001. The relative risk (RR) to develop microalbuminuria in diabetic subjects with the polymorphism is 3X higher than diabetic subjects without the polymorphism (RR 3.142, 95% CI 1.9238 to 5.1249; p<0.05). Kaplan-Meier survival curves demonstrated that the GG genotype group developed microalbuminuria and macroalbuminuria at a more rapid rate than the GC or CC genotypes. Functional studies demonstrated that the basal activity of the substituted allele/promoter (-20 GG allele) was significantly greater than that of the wild type promoter (-20 CC genotype). This higher level of basal activity of substituted allele CTGF/CCN2 promoter was abrogated upon suppression of Smad1 levels, indicating that SNP region in the CTGF/CCN2 promoter plays a vital role in the gene expression. CONCLUSIONS These findings provide the first evidence that variants within the promoter region of the CTGF/CCN2 gene predisposes diabetic subjects to develop albuminuria and demonstrate that Smad1 [corrected] controls the expression of CTGF/CCN2 promoter through this region.

Epigenotype-phenotype correlations in Silver-Russell syndrome

Background

Silver–Russell syndrome (SRS) is characterised by intrauterine growth restriction, poor postnatal growth, relative macrocephaly, triangular face and asymmetry. Maternal uniparental disomy (mUPD) of chromosome 7 and hypomethylation of the imprinting control region (ICR) 1 on chromosome 11p15 are found in 5–10% and up to 60% of patients with SRS, respectively. As many features are non-specific, diagnosis of SRS remains difficult. Studies of patients in whom the molecular diagnosis is confirmed therefore provide valuable clinical information on the condition.

Methods

A detailed, prospective study of 64 patients with mUPD7 (n=20) or ICR1 hypomethylation (n=44) was undertaken.

Results and conclusions

The considerable overlap in clinical phenotype makes it difficult to distinguish these two molecular subgroups reliably. ICR1 hypomethylation was more likely to be scored as ‘classical’ SRS. Asymmetry, fifth finger clinodactyly and congenital anomalies were more commonly seen with ICR1 hypomethylation, whereas learning difficulties and referral for speech therapy were more likely with mUPD7. Myoclonus-dystonia has been reported previously in one mUPD7 patient. The authors report mild movement disorders in three further cases. No correlation was found between clinical severity and level of ICR1 hypomethylation. Use of assisted reproductive technology in association with ICR1 hypomethylation seems increased compared with the general population. ICR1 hypomethylation was also observed in affected siblings, although recurrence risk remains low in the majority of cases. Overall, a wide range of severity was observed, particularly with ICR1 hypomethylation. A low threshold for investigation of patients with features suggestive, but not typical, of SRS is therefore recommended.

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.

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.

DNA methylation errors at imprinted loci after assisted conception originate in the parental sperm

There is an increased prevalence of imprinting disorders, such as Beckwith–Wiedemann syndrome, associated with human assisted reproductive technologies (ART). Work on animal models suggests that in vitro culture may be the source of these imprinting errors. However, in this study we report that, in some cases, the errors are inherited from the father. We analyzed DNA methylation at seven autosomal imprinted loci and the XIST locus in 78 paired DNA samples. In seven out of seventeen cases where there was abnormal DNA methylation in the ART sample (41%), the identical alterations were present in the parental sperm. Furthermore, we also identified DNA sequence variations in the gene encoding DNMT3L, which were associated with the abnormal paternal DNA methylation. Both the imprinting errors and the DNA sequence variants were more prevalent in patients with oligospermia. Our data suggest that the increase in the incidence of imprinting disorders in individuals born by ART may be due, in some cases, to the use of sperm with intrinsic imprinting mutations.

Methylation defects of imprinted genes in human testicular spermatozoa

OBJECTIVE

To study the methylation imprinting marks of two oppositely imprinted genes, H19 and MEST/PEG1, in human testicular spermatozoa from azoospermic patients with different etiologies. Testicular spermatozoa are often used in intracytoplasmic sperm injection for treatment of male factor infertility, but the imprinting status of these cells is currently unknown.

DESIGN

Experimental prospective study.

SETTING

University research laboratory and private in vitro fertilization (IVF) clinic.

PATIENT(S)

A total of 24 men, five with anejaculation, five with secondary obstructive azoospermia, five with primary obstructive azoospermia, and nine with secretory azoospermia due to hypospermatogenesis.

INTERVENTION(S)

Spermatozoa were isolated by micromanipulation from testicular biopsies.

MAIN OUTCOME MEASURE(S)

DNA methylation patterns were analyzed using bisulfite genomic sequencing with cloning analysis.

RESULT(S)

We found H19 complete methylation was statistically significantly reduced in secretory azoospermic patients with hypospermatogenesis, with one patient presenting complete unmethylation. Hypomethylation also affected the CTCF-binding site 6, involved in regulation of IGF2 expression. Regarding the MEST gene, all patients presented complete unmethylation although this was statistically significantly reduced in the anejaculation group.

CONCLUSION(S)

Testicular spermatozoa from men with abnormal spermatogenesis carry methylation defects in the H19 imprinted gene which also affect the CTCF-binding site, further supporting an association between the occurrence of imprinting errors and disruptive spermatogenesis.

Hypomethylation of the H19 gene causes not only Silver-Russell syndrome (SRS) but also isolated asymmetry or an SRS-like phenotype

The H19 differentially methylated region (DMR) controls the allele-specific expression of both the imprinted H19 tumor-suppressor gene and the IGF2 growth factor. Hypermethylation of this DMR--and subsequently of the H19 promoter region--is a major cause of the clinical features of gigantism and/or asymmetry seen in Beckwith-Wiedemann syndrome or in isolated hemihypertrophy. Here, we report a series of patients with hypomethylation of the H19 locus. Their main clinical features of asymmetry and growth retardation are the opposite of those seen in patients with hypermethylation of this region. In addition, we show that complete hypomethylation of the H19 promoter is found in two of three patients with the full clinical spectrum of Silver-Russell syndrome. This syndrome is also characterized by growth retardation and asymmetry, among other clinical features. We conclude that patients with these clinical features should be analyzed for H19 hypomethylation.