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Maternal loss of imprinting (LOI) at the H19/IGF2 locus results in biallelic IGF2 and reduced H19 expression and is associated with Beckwith--Wiedemann syndrome (BWS). We use mouse models for LOI to understand the relative importance of Igf2 and H19 mis-expression in BWS phenotypes. Here we focus on cardiovascular phenotypes and show that neonatal cardiomegaly is exclusively dependent on increased Igf2 . Circulating IGF2 binds cardiomyocyte receptors to hyperactivate mTOR signaling, resulting in cellular hyperplasia and hypertrophy. These Igf2 -dependent phenotypes are transient: cardiac size returns to normal once Igf2 expression is suppressed postnatally. However, reduced H19 expression is sufficient to cause progressive heart pathologies including fibrosis and reduced ventricular function. In the heart, H19 expression is primarily in endothelial cells (ECs) and regulates EC differentiation both in vivo and in vitro. Finally, we establish novel mouse models to show that cardiac phenotypes depend on H19 lncRNA interactions with Mirlet7 microRNAs., Competing Interests: KP, HL, ZY, JN, AM, CK, RK, DS, CG, BK, KP None, BR none

Genomic imprinting is an epigenetic process regulated by germline-derived DNA methylation that is resistant to embryonic reprogramming, resulting in parental origin-specific monoallelic gene expression. A subset of individuals affected by imprinting disorders (IDs) displays multi-locus imprinting disturbances (MLID), which may result from aberrant establishment of imprinted differentially methylated regions (DMRs) in gametes or their maintenance in early embryogenesis. Here we investigated the extent of MLID in a family harbouring a ZFP57 truncating variant and characterize the interactions between human ZFP57 and the KAP1 co-repressor complex. By ectopically targeting ZFP57 to reprogrammed loci in mouse embryos using a dCas9 approach, we confirm that ZFP57 recruitment is sufficient to protect oocyte-derived methylation from reprogramming. Expression profiling in human pre-implantation embryos and oocytes reveals that unlike in mice, ZFP57 is only expressed following embryonic-genome activation, implying that other KRAB-zinc finger proteins (KZNFs) recruit KAP1 prior to blastocyst formation. Furthermore, we uncover ZNF202 and ZNF445 as additional KZNFs likely to recruit KAP1 to imprinted loci during reprogramming in the absence of ZFP57. Together, these data confirm the perplexing link between KZFPs and imprint maintenance and highlight the differences between mouse and humans in this respect., (© The Author(s) 2020. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Beckwith-Wiedemann syndrome (BWS) is a representative imprinting disorder. Gain of methylation at imprinting control region 1 (ICR1-GOM), leading to the biallelic expression of IGF2 and silencing of H19, is one of the causative alterations in BWS. Twenty percent of BWS patients with ICR1-GOM have genetic defects in ICR1. Evidence of methylation anticipation in familial BWS patients with ICR1 genetic defects has been reported. However, the precise methylation pattern and extent of anticipation in these patients remain elusive. In addition, although age-related IGF2-DMR0 hypomethylation has been reported in the normal population, the period of its occurrence is unknown. In this study, we analyzed 10 sites (IGF2-DMR0, IGF2-DMR2, CTCF binding sites 1-7, and the H19 promoter) within the IGF2/H19 domain in familial BWS patients harboring a pathogenic variant in ICR1. We found that sites near the variant had relatively higher methylation in the first affected generation and observed methylation anticipation through maternal transmission in the next generation. The extent of anticipation was greater at sites far from the variant than nearby sites. The extended and severe GOM might be due to the insufficient erasure/demethylation of pre-acquired ICR1-GOM in primordial germ cells or during the preimplantation stage. In the normal population, age-related IGF2-DMR0 hypomethylation occurred; it became established by young adulthood and continued to old age. Further studies are needed to clarify (1) the precise mechanism of anticipation in patients with familial BWS and (2) the mechanism and biological significance of constitutive hypomethylation of IGF2-DMR0 and/or other imprinted differentially methylated regions.

Beckwith-Wiedemann syndrome (BWS; OMIM #130650) is an imprinting disorder caused by genetic or epigenetic alterations of one or both imprinting control regions on chromosome 11p15.5. Hypomethylation of the centromeric imprinting control region (KCNQ1OT1:TSS-DMR, ICR2) is the most common molecular cause of BWS and is present in about half of the cases. Based on a BWS family with a maternal deletion of the 5' part of KCNQ1 we have recently hypothesised that transcription of KCNQ1 is a prerequisite for the establishment of methylation at the KCNQ1OT1:TSS-DMR in the oocyte. Further evidence for this hypothesis came from a mouse model where methylation failed to be established when a poly(A) truncation cassette was inserted into this locus to prevent transcription through the DMR. Here we report on a family where a balanced translocation disrupts the KCNQ1 gene in intron 9. Maternal inheritance of this translocation is associated with hypomethylation of the KCNQ1OT1:TSS-DMR and BWS. This finding strongly supports our previous hypothesis that transcription of KCNQ1 is required for establishing the maternal methylation imprint at the KCNQ1OT1:TSS-DMR.

The loss of insulin-secreting β cells is characteristic among type I and type II diabetes. Stimulating proliferation to expand sources of β cells for transplantation remains a challenge because adult β cells do not proliferate readily. The cell cycle inhibitor p57 has been shown to control cell division in human β cells. Expression of p57 is regulated by the DNA methylation status of the imprinting control region 2 (ICR2), which is commonly hypomethylated in Beckwith-Wiedemann syndrome patients who exhibit massive β cell proliferation. We hypothesized that targeted demethylation of the ICR2 using a transcription activator-like effector protein fused to the catalytic domain of TET1 (ICR2-TET1) would repress p57 expression and promote cell proliferation. We report here that overexpression of ICR2-TET1 in human fibroblasts reduces p57 expression levels and increases proliferation. Furthermore, human islets overexpressing ICR2-TET1 exhibit repression of p57 with concomitant upregulation of Ki-67 while maintaining glucose-sensing functionality. When transplanted into diabetic, immunodeficient mice, the epigenetically edited islets show increased β cell replication compared with control islets. These findings demonstrate that epigenetic editing is a promising tool for inducing β cell proliferation, which may one day alleviate the scarcity of transplantable β cells for the treatment of diabetes.

Background: Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder with a population frequency of approximately 1 in 10,000. The most common epigenetic defect in BWS is a loss of methylation (LOM) at the 11p15.5 imprinting centre, KCNQ1OT1 TSS-DMR, and affects 50% of cases. We hypothesised that genetic factors linked to folate metabolism may play a role in BWS predisposition via effects on methylation maintenance at KCNQ1OT1 TSS-DMR., Results: Single nucleotide variants (SNVs) in the folate pathway affecting methylenetetrahydrofolate reductase (MTHFR), methionine synthase reductase (MTRR), 5-methyltetrahydrofolate-homocysteine S-methyltransferase (MTR), cystathionine beta-synthase (CBS) and methionine adenosyltransferase (MAT1A) were examined in 55 BWS patients with KCNQ1OT1 TSS-DMR LOM and in 100 unaffected cases. MTHFR rs1801133: C>T was more prevalent in BWS with KCNQ1OT1 TSS-DMR LOM (p < 0.017); however, the relationship was not significant when the Bonferroni correction for multiple testing was applied (significance, p = 0.0036). None of the remaining 13 SNVs were significantly different in the two populations tested. The DNMT1 locus was screened in 53 BWS cases, and three rare missense variants were identified in each of three patients: rs138841970: C>T, rs150331990: A>G and rs757460628: G>A encoding NP&#95;001124295 p.Arg136Cys, p.His1118Arg and p.Arg1223His, respectively. These variants have population frequencies of less than 1 in 1000 and were absent from 100 control cases. Functional characterization using a hemimethylated DNA trapping assay revealed a reduced methyltransferase activity relative to wild-type DNMT1 for each variant ranging from 40 to 70% reduction in activity., Conclusions: This study is the first to examine folate pathway genetics in BWS and to identify rare DNMT1 missense variants in affected individuals. Our data suggests that reduced DNMT1 activity could affect maintenance of methylation at KCNQ1OT1 TSS-DMR in some cases of BWS, possibly via a maternal effect in the early embryo. Larger cohort studies are warranted to further interrogate the relationship between impaired MTHFR enzymatic activity attributable to MTHFR rs1801133: C>T, dietary folate intake and BWS.

Imprinted genes occur in discrete clusters that are coordinately regulated by shared DNA elements called Imprinting Control Regions. H19 and Igf2 are linked imprinted genes that play critical roles in development. Loss of imprinting (LOI) at the IGF2/H19 locus on the maternal chromosome is associated with the developmental disorder Beckwith Wiedemann Syndrome (BWS) and with several cancers. Here we use comprehensive genetic and genomic analyses to follow muscle development in a mouse model of BWS to dissect the separate and shared roles for misexpression of Igf2 and H19 in the disease phenotype. We show that LOI results in defects in muscle differentiation and hypertrophy and identify primary downstream targets: Igf2 overexpression results in over-activation of MAPK signaling while loss of H19 lncRNA prevents normal down regulation of p53 activity and therefore results in reduced AKT/mTOR signaling. Moreover, we demonstrate instances where H19 and Igf2 misexpression work separately, cooperatively, and antagonistically to establish the developmental phenotype. This study thus identifies new biochemical roles for the H19 lncRNA and underscores that LOI phenotypes are multigenic so that complex interactions will contribute to disease outcomes., (Published by Oxford University Press on behalf of Nucleic Acids Research 2017.)

Beckwith-Wiedemann syndrome (BWS) is a human stem cell disorder, and individuals with this disease have a substantially increased risk (~800-fold) of developing tumors. Epigenetic silencing of β2-spectrin (β2SP, encoded by SPTBN1), a SMAD adaptor for TGF-β signaling, is causally associated with BWS; however, a role of TGF-β deficiency in BWS-associated neoplastic transformation is unexplored. Here, we have reported that double-heterozygous Sptbn1+/- Smad3+/- mice, which have defective TGF-β signaling, develop multiple tumors that are phenotypically similar to those of BWS patients. Moreover, tumorigenesis-associated genes IGF2 and telomerase reverse transcriptase (TERT) were overexpressed in fibroblasts from BWS patients and TGF-β-defective mice. We further determined that chromatin insulator CCCTC-binding factor (CTCF) is TGF-β inducible and facilitates TGF-β-mediated repression of TERT transcription via interactions with β2SP and SMAD3. This regulation was abrogated in TGF-β-defective mice and BWS, resulting in TERT overexpression. Imprinting of the IGF2/H19 locus and the CDKN1C/KCNQ1 locus on chromosome 11p15.5 is mediated by CTCF, and this regulation is lost in BWS, leading to aberrant overexpression of growth-promoting genes. Therefore, we propose that loss of CTCF-dependent imprinting of tumor-promoting genes, such as IGF2 and TERT, results from a defective TGF-β pathway and is responsible at least in part for BWS-associated tumorigenesis as well as sporadic human cancers that are frequently associated with SPTBN1 and SMAD3 mutations.

Oxidative stress is a distinctive sign in several genetic disorders characterized by cancer predisposition, such as Ataxia-Telangiectasia, Fanconi Anemia, Down syndrome, progeroid syndromes, Beckwith-Wiedemann syndrome, and Costello syndrome. Recent literature unveiled new molecular mechanisms linking oxidative stress to the pathogenesis of these conditions, with particular regard to mitochondrial dysfunction. Since mitochondria are one of the major sites of ROS production as well as one of the major targets of their action, this dysfunction is thought to be the cause of the prooxidant status. Deeper insight of the pathogenesis of the syndromes raises the possibility to identify new possible therapeutic targets. In particular, the use of mitochondrial-targeted agents seems to be an appropriate clinical strategy in order to improve the quality of life and the life span of the patients.

Background: Beckwith-Wiedemann syndrome (BWS) is an overgrowth syndrome with an increased risk of cancer. Most BWS patients show a molecular defect in the 11p15 region that contains imprinted genes. BWS has been associated with malignant neoplasms during infancy. Descriptions of benign tumors, especially in adult patients, are rarer., Methods/results: We report the case of a BWS patient with pituitary adenoma caused by loss of methylation (LOM) at ICR2 (locus CDKN1C/KCNQ1OT1). The patient was referred to an endocrinology unit for suspicion of Cushing's disease due to a history of macroglossia and hemihyperplasia. Biological tests led to the diagnosis of ACTH-dependent hypercortisolism. MRI showed a microadenoma of the pituitary gland, confirming the diagnosis of Cushing's disease. DNA methylation analysis revealed LOM at ICR2 that was in a mosaic state in the patient's leukocytes, but was present in nearly all cells of the pituitary adenoma. The epigenetic defect was associated with a somatic USP8 mutation in the adenoma., Conclusion: Pituitary adenoma rarely occurs in patients with BWS. However, BWS should be considered in cases of pituitary adenoma with minor and/or major signs of BWS. The association between ICR2 LOM and USP8 mutation in the adenoma is questionable. © 2016 S. Karger AG, Basel.

Aims: To study the frequency of methylation abnormalities among Estonian patients selected according to published clinical diagnostic scoring systems for Silver-Russell syndrome (SRS) and Beckwith-Wiedemann syndrome (BWS)., Materials and Methods: Forty-eight patients with clinical suspicion of SRS (n = 20) or BWS (n = 28) were included in the study group, to whom methylation-specific multiplex ligation-dependant probe amplification analysis of 11p15 region was made. In addition, to patients with minimal diagnostic score for either SRS or BWS, multilocus methylation-specific single nucleotide primer extension assay was performed., Results: Five (38%) SRS patients with positive clinical scoring had abnormal methylation pattern at chromosome 11p15, whereas in the BWS group, only one patient was diagnosed with imprinting control region 2 (ICR2) hypomethylation (8%). An unexpected hypomethylation of the PLAGL1 (6q24) and IGF2R (6q25) genes in the patient with the highest BWS scoring was found., Conclusions: Compared to BWS, diagnostic criteria used for selecting SRS patients gave us a similar detection rate of 11p15 imprinting disorders as seen in other studies. A more careful selection of patients with possible BWS should be considered to improve the detection of molecularly confirmed cases. Genome-wide multilocus methylation tests could be used in routine clinical practice as it increases the detection rates of imprinting disorders.

Context: Several patients with Beckwith-Wiedemann Syndrome (BWS) with multiple imprinting defects found by genetic analysis have been described. However, only two cases have been described with both genetic and clinical signs and symptoms of multiple diseases caused by imprinting defects., Case Description: The girl in this case presented at the age of 6 months with morbid obesity (body mass index, +7.5 SDS) and a large umbilical hernia. Genetic analysis showed BWS (hypomethylation of the KCNQ1OT1 gene). Calcium homeostasis was normal, and she had no signs of Albright hereditary osteodystrophy. At the age of 10 years, she presented with fatigue, and laboratory analyses showed marked hypocalcemia with signs of PTH resistance, but without evidence for Albright hereditary osteodystrophy, thus suggesting pseudohypoparathyroidism type 1B. Consistent with this diagnosis, methylation analysis of the GNAS complex revealed hypomethylation (about 20%) of the GNAS exon 1A, NESPAS, and GNASXL loci and hypermethylation (100% methylation) of the NESP locus., Conclusions: Imprinting defects at several different loci can occur in some patients, thus causing multiple different diseases. Symptoms of pseudohypoparathyroidism type 1B may be absent at diagnosis of BWS, yet prolonged subclinical hypocalcemia and/or hyperphosphatemia can have negative consequences (eg, intracerebral calcifications, myocardial dysfunction). We therefore suggest that patients with an imprinting disorder should be monitored for elevations in PTH, and epigenetic analysis of the GNAS complex locus should be considered.

Isolated gain of methylation (GOM) at the IGF2/H19 imprinting control region 1 (ICR1) accounts for about 10% of patients with BWS. A subset of these patients have genetic defects within ICR1, but the frequency of these defects has not yet been established in a large cohort of BWS patients with isolated ICR1 GOM. Here, we carried out a genetic analysis in a large cohort of 57 BWS patients with isolated ICR1 GOM and analyzed the methylation status of the entire domain. We found a new point mutation in two unrelated families and a 21 bp deletion in another unrelated child, both of which were maternally inherited and affected the OCT4/SOX2 binding site in the A2 repeat of ICR1. Based on data from this and previous studies, we estimate that cis genetic defects account for about 20% of BWS patients with isolated ICR1 GOM. Methylation analysis at eight loci of the IGF2/H19 domain revealed that sites surrounding OCT4/SOX2 binding site mutations were fully methylated and methylation indexes declined as a function of distance from these sites. This was not the case in BWS patients without genetic defects identified. Thus, GOM does not spread uniformly across the IGF2/H19 domain, suggesting that OCT4/SOX2 protects against methylation at local sites. These findings add new insights to the mechanism of the regulation of the ICR1 domain. Our data show that mutations and deletions within ICR1 are relatively common. Systematic identification is therefore necessary to establish appropriate genetic counseling for BWS patients with isolated ICR1 GOM., (© The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Oxidative stress plays a key role in carcinogenesis. Oxidative damage to cell components can lead to the initiation, promotion and progression of cancer. Oxidative stress is also a distinctive sign in several genetic disorders characterized by a cancer predisposition such as ataxia-telangiectasia, Fanconi anemia, Down syndrome, Beckwith-Wiedemann syndrome and Costello syndrome. Taking into account the link between oxidative stress and cancer, the capacity of antioxidant agents to prevent or delay neoplastic development has been tested in various studies, both in vitro and in vivo, with interesting and promising results. In recent years, research has been conducted into the molecular mechanisms linking oxidative stress to the pathogenesis of the genetic syndromes we consider in this review, with the resulting identification of possible new therapeutic targets. The aim of this review is to focus on the oxidative mechanisms intervening in carcinogenesis in cancer-prone genetic disorders and to analyze the current status and future prospects of antioxidants.

Beckwith-Wiedemann syndrome (BWS) is caused by dysregulation of imprinted genes on chromosome 11.p15.5. The syndrome includes overgrowth, macroglossia, organomegaly, abdominal wall defects, hypoglycemia, and long-term malignancy risk. No patient who has BWS has been reported with hypopituitarism. We describe a patient who presented at birth with macrosomia, macroglossia, respiratory distress, jaundice, and hypoglycemia, and who was followed for 4.5 years. Genetic test for BWS was performed, which detected loss of maternal methylation on region KvDMR1 (11p15.5). The hypoglycemia was attributable to hyperinsulinism and was treated with diazoxide and chlorothiazide. She responded well, but the hypoglycemia returned after reducing the diazoxide. It was possible to stop the diazoxide after 2.5 years. On routine follow-up she was noted to be developing short stature. Baseline pituitary and growth hormone (GH) stimulation tests detected GH deficiency and secondary hypothyroidism. A brain MRI showed a small anterior pituitary gland. Thereafter, thyroxine and replacement therapy with GH were started, which resulted in a remarkable improvement in growth velocity. This is the first patient to be reported as having hypopituitarism and BWS. It is unclear if the BWS and the hypopituitarism are somehow connected; however, further investigations are necessary. Hypopituitarism explains the protracted hypoglycemia and the short stature. In our patient, GH therapy seems to be safe, but strict follow-up is required given the increased cancer risk related to BWS.

Beckwith-Wiedemann syndrome (BWS) is a congenital disorder of imprinting caused by epimutations and mutations affecting two imprinted loci on chromosome 11p15. Its clinical features are heterogeneous, including macrosomia, macroglossia, hemihyperplasia, abdominal wall defects, neonatal hypoglycemia, and increased risk of embryonal tumors such as Wilms tumor, adrenocortical carcinoma, hepatoblastoma, and neuroblastoma. The molecular and clinical heterogeneity of BWS makes the diagnosis challenging, but essential, since different etiologies of BWS have different clinical prognoses - most crucially, patients with gain of maternal methylation at imprinting control region type 1 (ICR1) are at significant risk of Wilms tumor or hepatoblastoma. We present three cases of BWS with different symptomatology and two different molecular diagnoses. The authors emphasize the importance of molecular studies in the long-term follow-up of children with BWS, including refinement of phenotype-genotype correlation and its connection with optimal management and tumor surveillance.

Genomic imprinting is a parent-of-origin allele-specific epigenetic process that is critical for normal development and health. The establishment and maintenance of normal imprinting is dependent on both cis-acting imprinting control centers, which are marked by differentially (parental allele specific) methylated marks, and trans mechanisms, which regulate the establishment and/or maintenance of the correct methylation epigenotype at the imprinting control centers. Studies of rare human imprinting disorders such as familial hydatidiform mole, Beckwith-Wiedemann syndrome and familial transient neonatal diabetes mellitus have enabled the identification of genetic (e.g., mutations in KHDC3L [C6ORF221], NLRP2 [NALP2], NLRP7 [NALP7] and ZFP57) and environmental (assisted reproductive technologies) factors that can disturb the normal trans mechanisms for imprinting establishment and/or maintenance. Here we review the clinical and molecular aspects of these imprinting disorders in order to demonstrate how the study of rare inherited disorders can illuminate the molecular characteristics of fundamental epigenetic processes, such as genomic imprinting.

Aims: Placental mesenchymal dysplasia (PMD) is a rare condition which is associated with the disparate fetal outcomes of Beckwith-Wiedemann syndrome (BWS), fetal growth restriction or intrauterine and neonatal death. We aimed to investigate the potential epigenetic/genetic anomalies associated with PMD and their relationship with the different causes of BWS., Methods: Eight archival cases in which PMD, BWS or both were diagnosed were investigated by correlating morphology with p57 Kip2 expression, XY fluorescence in situ hybridisation (FISH) analysis and DNA genotyping., Results: Placentae from BWS cases caused by aberrant IC2 methylation, leading to abnormal p57 Kip2 expression, did not show PMD but had a striking excess of extravillous trophoblast. PMD in the absence of BWS was caused by androgenetic/biparental mosaicism. The single case of BWS with PMD was due to mosaic uniparental disomy of 11p15.5. In the latter two aetiologies, our results indicate that the uniparental disomy is confined to the villous mesenchyme., Conclusions: These results suggest that the link between PMD and BWS is uniparental disomy of genes confined to the telomeric IC1 region of 11p15.5. A strong candidate gene is IGF2, a known growth factor of placental mesenchyme.

IMAGe syndrome (intrauterine growth restriction, metaphyseal dysplasia, adrenal hypoplasia congenita and genital anomalies) is an undergrowth developmental disorder with life-threatening consequences. An identity-by-descent analysis in a family with IMAGe syndrome identified a 17.2-Mb locus on chromosome 11p15 that segregated in the affected family members. Targeted exon array capture of the disease locus, followed by high-throughput genomic sequencing and validation by dideoxy sequencing, identified missense mutations in the imprinted gene CDKN1C (also known as P57KIP2) in two familial and four unrelated patients. A familial analysis showed an imprinted mode of inheritance in which only maternal transmission of the mutation resulted in IMAGe syndrome. CDKN1C inhibits cell-cycle progression, and we found that targeted expression of IMAGe-associated CDKN1C mutations in Drosophila caused severe eye growth defects compared to wild-type CDKN1C, suggesting a gain-of-function mechanism. All IMAGe-associated mutations clustered in the PCNA-binding domain of CDKN1C and resulted in loss of PCNA binding, distinguishing them from the mutations of CDKN1C that cause Beckwith-Wiedemann syndrome, an overgrowth syndrome.

The insulin-like growth factor (IGF) signaling pathway has many important roles in normal cell growth and development. Remarkably, all of the components of this system (IGFs, receptors, and binding proteins) are expressed in human fetal adrenals. Beckwith-Wiedemann syndrome, a congenital overgrowth disorder characterized by a high risk of development of childhood tumors, is also distinguished by a high incidence of adrenocortical carcinomas. This disease has been associated with structural abnormalities at the 11p15 locus, which harbors the IGF2 gene as well as the genes coding for insulin, H19, and p57kip2. Notably, rearrangements at the 11p15 locus and overexpression of IGF2 were also described in sporadic adrenocortical tumors. In addition, the IGF2 overexpression was exclusively demonstrated in adults with adrenocortical tumors as a frequent feature of the malignant state. More recent studies demonstrated that the interaction of IGF-2 with IGF receptor type 1 (IGF-1R) plays also a pivotal role in adrenocortical tumorigenesis. IGF1R expression levels were significantly higher in pediatric adrenocortical carcinomas, suggesting that IGF1R expression represents a potential prognostic marker in this group of patients. These findings indicate that the IGF system is an important pathway for autonomous growth of adrenocortical cells and potential inhibitors of this system could be a rational therapeutic target for adrenocortical tumors., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

A cluster of imprinted genes at chromosome 11p15.5 is associated with the growth disorders, Silver-Russell syndrome (SRS) and Beckwith-Wiedemann syndrome (BWS). The cluster is divided into two domains with independent imprinting control regions (ICRs). We describe two maternal 11p15.5 microduplications with contrasting phenotypes. The first is an inverted and in cis duplication of the entire 11p15.5 cluster associated with the maintenance of genomic imprinting and with the SRS phenotype. The second is a 160 kb duplication also inverted and in cis, but resulting in the imprinting alteration of the centromeric domain. It includes the centromeric ICR (ICR2) and the most 5' 20 kb of the non-coding KCNQ1OT1 gene. Its maternal transmission is associated with ICR2 hypomethylation and the BWS phenotype. By excluding epigenetic mosaicism, cell clones analysis indicated that the two closely located ICR2 sequences resulting from the 160 kb duplication carried discordant DNA methylation on the maternal chromosome and supported the hypothesis that the ICR2 sequence is not sufficient for establishing imprinted methylation and some other property, possibly orientation-dependent, is needed. Furthermore, the 1.2 Mb duplication demonstrated that all features are present for correct imprinting at ICR2 when this is duplicated and inverted within the entire cluster. In the individuals maternally inheriting the 160 kb duplication, ICR2 hypomethylation led to the expression of a truncated KCNQ1OT1 transcript and to down-regulation of CDKN1C. We demonstrated by chromatin RNA immunopurification that the KCNQ1OT1 RNA interacts with chromatin through its most 5' 20 kb sequence, providing a mechanism likely mediating the silencing activity of this long non-coding RNA.

Beckwith–Wiedemann syndrome (BWS) is one of the most prevalent congenital disorders predominantly caused by epigenetic alterations. Here we present an extensive case study of a monozygotic monochorionic male twin pair discordant for BWS. Our analysis allows to correlate BWS symptoms, like a protruding tongue, indented ears and transient neonatal hypoglycaemia, to an abnormal methylation at the KvDMR1. DNAs extracted from peripheral blood, skin fibroblasts, saliva and buccal swab of both twins, their sister and parents were analysed at 11 differentially methylated regions (DMRs) including all four relevant DMRs of the BWS region. The KvDMR1 was exclusively found to be hypomethylated in all cell types of the affected BWS twin, while the unaffected twin and the relatives showed normal methylation in fibroblasts, buccal swab and saliva DNA. Interestingly, the twins share a common blood-specific hypomethylation phenotype most probably caused by a feto-fetal transfusion between both twins. Because microsatellite analysis furthermore revealed a normal biparental karyotype for chromosome 11, our results point to an exclusive correlation of the observed BWS symptoms to locally restricted epimutations at the KvDMR1 of the maternal chromosome., (© 2010 John Wiley & Sons A/S.)

Hyper- and hypomethylation at the IGF2-H19 imprinting control region (ICR) result in reciprocal changes in IGF2-H19 expression and the two contrasting growth disorders, Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS). DNA methylation of the ICR controls the reciprocal imprinting of IGF2 and H19 by preventing the binding of the insulator protein, CTCF. We here show that local changes in histone modifications and CTCF--cohesin binding at the ICR in BWS and SRS together with DNA methylation correlate with the higher order chromatin structure at the locus. In lymphoblastoid cells from control individuals, we found the repressive histone H3K9me3 and H4K20me3 marks associated with the methylated paternal ICR allele and the bivalent H3K4me2/H3K27me3 mark together with H3K9ac and CTCF--cohesin associated with the non-methylated maternal allele. In patient-derived cell lines, the mat/pat asymmetric distribution of these epigenetic marks was lost with H3K9me3 and H4K20me3 becoming biallelic in the BWS and H3K4me2, H3K27me3 and H3K9ac together with CTCF-cohesin becoming biallelic in the SRS. We further show that in BWS and SRS cells, there is opposing chromatin looping conformation mediated by CTCF--cohesin binding sites surrounding the locus. In normal cells, lack of CTCF--cohesin binding at the paternal ICR is associated with monoallelic interaction between two CTCF sites flanking the locus. CTCF--cohesin binding at the maternal ICR blocks this interaction by associating with the CTCF site downstream of the enhancers. The two alternative chromatin conformations are differently favoured in BWS and SRS likely predisposing the locus to the activation of IGF2 or H19, respectively.

Imprinted genes are commonly clustered in domains across the mammalian genome, suggesting a degree of coregulation via long-range coordination of their monoallelic transcription. The distal end of mouse chromosome 7 (Chr 7) contains two clusters of imprinted genes within a approximately 1 Mb domain. This region is conserved on human 11p15.5 where it is implicated in the Beckwith-Wiedemann syndrome. In both species, imprinted regulation requires two critical cis-acting imprinting centres, carrying different germline epigenetic marks and mediating imprinted expression in the proximal and distal sub-domains. The clusters are separated by a region containing the gene for tyrosine hydroxylase (Th) as well as a high density of short repeats and retrotransposons in the mouse. We have used the Cre-loxP recombination system in vivo to engineer an interstitial deletion of this approximately 280-kb intervening region previously proposed to participate in the imprinting mechanism or to act as a boundary between the two sub-domains. The deletion allele, Del(7AI), is silent with respect to epigenetic marking at the two flanking imprinting centres. Reciprocal inheritance of Del(7AI) demonstrates that the deleted region, which represents more than a quarter of the previously defined imprinted domain, is associated with intrauterine growth restriction in maternal heterozygotes. In homozygotes, the deficiency behaves as a Th null allele and can be rescued pharmacologically by bypassing the metabolic requirement for TH in utero. Our results show that the deleted interval is not required for normal imprinting on distal Chr 7 and uncover a new imprinted growth phenotype.

Progress in the identification of the (epi)genetic basis of imprinting disorders has provided greater insight into the central role of imprinted genes in regular human growth. In addition to the well-known Prader-Willi, Angelman, and Beckwith-Wiedemann syndromes, imprinting disturbances have recently been identified in transient neonatal diabetes mellitus, uniparental disomy (14) syndromes and Silver- Russell syndrome (SRS). Among these diseases, the growth retardation disorder SRS is unique because it is the first human disorder associated with epigenetic mutations that affect two different chromosomes. In addition to maternal uniparental disomy of chromosome 7, hypomethylation of the imprinting control region 1 in 11p15 and maternal duplication of 11p15 have recently been described as major (epi)genetic disturbances in SRS. Interestingly, opposite (epi)- mutations are involved in the overgrowth disease Beckwith-Wiedemann syndrome (BWS). Thus SRS and BWS can be regarded as two genetically and clinically opposite clinical pictures. Although not yet completely understood, SRS and BWS can be used as models to decipher the functional link between the observed (epi)genetic mutations and the clinical features in individuals with disturbed growth. Future studies will clarify the complex basis of human growth and hopefully contribute to better-directed therapies., (Copyright 2009 S. Karger AG, Basel.)

Background: Beckwith-Wiedemann syndrome (BWS) is a congenital overgrowth syndrome that is clinically and genetically heterogeneous. Hyperinsulinemic hypoglycemia occurs in about 50% of children with BWS and, in the majority of infants, it resolves spontaneously. However, in a small group of patients the hypoglycemia can be persistent and may require pancreatectomy. The mechanism of persistent hyperinsulinemic hypoglycemia in this group of patients is unclear., Patients and Methods: Using patch-clamp techniques on pancreatic tissue obtained at the time of surgery, we investigated the electrophysiological properties of ATP-sensitive K(+) (K(ATP)) channels in pancreatic beta-cells in a patient with BWS and severe medically-unresponsive hyperinsulinemic hypoglycemia., Results: Persistent hyperinsulinism was found to be caused by abnormalities in K(ATP) channels of the pancreatic beta-cell. Immunofluorescence studies using a SUR1 antibody revealed perinuclear pattern of staining in the BWS cells, suggesting a trafficking defect of the SUR1 protein. No mutations were found in the genes ABCC8 and KCNJ11 encoding for the two subunits, SUR1 and KIR6.2, respectively, of the K(ATP) channel. Genetic analysis of this patients BWS showed evidence of mosaic paternal isodisomy., Conclusions: In this novel case of BWS with mosaic paternal uniparental disomy for 11p15, persistent hyperinsulinism was due to abnormalities in K(ATP) channels of the pancreatic beta-cell. The mechanism/s by which mosaic paternal uniparental disomy for 11p15 causes a trafficking defect in the SUR1 protein of the K(ATP) channel remains to be elucidated.

Aim: To compare the expression of p57 as indirect marker of genomic imprinting of CDKN1C in a series of infantile hemangiomas (IH) of patients with and without Beckwith-Wiedemann syndrome., Materials and Methods: Cases of mammary, salivary gland, liver (one each), and placental (2 cases) capillary hemangiomas all with histological features akin to IH as well as typical examples of cutaneous (8 cases) IH were analyzed by immunohistochemistry with antibody against p57(KIP2). This protein is the product of CDKN1C an imprinted, maternally expressed gene. The liver hemangioma and both chorioangiomas were from patients with Beckwith-Wiedemann syndrome. Positive and negative controls included normal placental tissue and complete hydatidiform mole, respectively. Positive staining was localized to nuclei., Results: Endothelial cells from the skin, breast and salivary gland hemangiomas were p57(KIP2) positive while chorioangiomas and liver IH presenting in patients with Beckwith-Wiedemann syndrome were negative. Controls reacted appropriately., Conclusions: Endothelial cells of IH not associated with BWS normally express p57(KIP2) while chorioangiomas and IH of the liver associated with BWS do not. These results suggest that the BWS IH may result from dysregulation of the cell cycle.

We report a case of extensive fatty change in a Wilms' tumour after chemotherapy demonstrated on CT associated with an increase in tumour volume, in a 10-month-old girl with Beckwith-Wiedemann syndrome. Changes in tumour characteristics after chemotherapy on imaging usually reflect necrosis, haemorrhage and calcification. Assessment of response to therapy is dependent on a documented reduction in tumour volume. In this case, CT showed an increase in tumour size with development of an extensive fatty component following treatment. Subsequent histological examination on the nephrectomy specimen confirmed an extensive fatty component with no evidence of residual blastema. The development of such an extensive fatty component is very unusual. In this case such fatty change was an indicator of tumour sensitivity and response to treatment.

Rhabdomyosarcoma (RMS) is a soft tissue tumor of childhood frequently diagnosed between the first and fifth year of life. Children with the Beckwith-Wiedemann syndrome (BWS), a congenital overgrowth syndrome characterized by exomphalos, macroglossia, and macrosomia, have an increased risk of developing childhood tumors including Wilms tumor, hepatoblastoma, neuroblastoma, and RMS. Although an association between RMS and the BWS is well accepted, only four cases have been reported to date, and of these, three were reported as embryonal RMS. Based on these data, an association between BWS and embryonal RMS has been proposed. We report three additional cases of BWS with RMS and review the clinical data for each patient as well as the pathology of their tumors. All three cases of BWS had histology consistent with alveolar RMS and were diagnosed at 6 weeks and 5 and 13 years of age. In two of these BWS cases, constitutional defects of 11p15 imprinting were demonstrated. Furthermore, cytogenetic analysis of the tumors did not detect the t(2;13) or t(1;13) translocations that generate the PAX3- or PAX7-FKHR fusion proteins common to alveolar RMS. These observations suggest that the development of alveolar RMS tumors in BWS may occur without the chromosomal rearrangement producing the PAX-FKHR fusion protein. In summary, we present three new cases of RMS demonstrating a new association between BWS and an uncommon subtype of alveolar RMS. The absence of the translocations commonly associated with alveolar rhabdomyosarcoma suggests a common 11p15 pathway for alveolar RMS and BWS.

Complex phenotypes and genotypes characterize the human disease, Beckwith--Wiedemann syndrome (BWS). Genetic and epigenetic mutations are found in five different genes which all lie within a 1 Mb imprinted domain on human chromosome 11p15. Only two of these genes, p57(KIP2) (CDKN1C) and IGF2, are likely to be functionally involved in this disease. The presence of the additional mutations therefore suggests a role for the regulation of these two genes by distant cis-elements. The mouse Igf2 gene is regulated by enhancers and imprinting elements which lie >120 kb downstream of its promoter. Here we show that key elements for expression of the mouse p57(Kip2) (Cdkn1c) gene also lie at a distance. Enhancers for expression within skeletal muscle and cartilage lie >25 kb downstream of the gene. In addition, we find no evidence for allele-specific expression of p57(Kip2) (Cdkn1c) from our bacterial artificial chromosome transgenes that span 315 kb around the locus. This suggests that a key imprinting element for p57(Kip2) (Cdkn1c) also lies at a distance. Therefore, BWS in humans may result from disruption of appropriate expression of the p57(KIP2) (CDKN1C) gene through mutations that occur at a substantial distance from the gene.

In mice, the imprinted Igf2 gene (expressed from the paternal allele), which encodes a growth-promoting factor (IGF-II), is linked closely to the reciprocally imprinted H19 locus on chromosome 7. Also imprinted (expressed from the maternal allele) is the Igf2r gene on chromsome 17 encoding the type 2 IGF receptor that is involved in degradation of excess IGF-II. Double mutant embryos carrying a deletion around the H19 region and also a targeted Igf2r allele, both inherited maternally, have extremely high levels of IGF-II (7- and 11-fold higher than normal in tissues and serum, respectively) as a result of biallelic Igf2 expression (imprint relaxation by deletion of H19-associated sequence) in combination with lack of the IGF2R-mediated IGF-II turnover. This excess of IGF-II causes somatic overgrowth, visceromegaly, placentomegaly, omphalocele, and cardiac and adrenal defects, which are also features of the Beckwith-Wiedemann syndrome (BWS), a genetically complex human disorder associated with chromosomal abnormalities in the 11p15.5 region where the IGF2 gene resides. In addition, the double mutant mouse embryos exhibit skeletal defects and cleft palate, which are manifestations observed frequently in the Simpson-Golabi-Behmel syndrome, another overgrowth disorder overlapping phenotypically, but not genetically, with BWS.

Mice lacking the imprinted Cdk inhibitor p57(KIP2) have altered cell proliferation and differentiation, leading to abdominal muscle defects; cleft palate; endochondral bone ossification defects with incomplete differentiation of hypertrophic chondrocytes; renal medullary dysplasia; adrenal cortical hyperplasia and cytomegaly; and lens cell hyperproliferation and apoptosis. Many of these phenotypes are also seen in patients with Beckwith-Wiedemann syndrome, a pleiotropic hereditary disorder characterized by overgrowth and predisposition to cancer, suggesting that loss of p57(KIP2) expression may play a role in the condition.

The Beckwith-Wiedemann syndrome (BWS) is genetically linked to chromosome 11p15.5, and a variety of observations suggest that deregulation of imprinted genes in this region is causally involved in the pathogenesis of the disease. It has been shown that in some patients without cytogenetic abnormalities the otherwise repressed maternal copy of the insulin-like growth factor 2 (IGF2) gene is expressed, leading to biallelic expression of IGF2. In some of these cases, this is accompanied by repression and DNA methylation of the maternal (otherwise active) copy of the neighbouring H19 gene. Hence, it is attractive to think that mutations may interfere with some aspect of H19 imprinting, thus leading to an inactive maternal allele, and indirectly to activation of the maternal IGF2 allele as reported in mice with an H19 gene deletion. However, no mutations have been identified so far in these patients. The only known mutations associated with BWS are maternally transmitted translocations, which are clustered in two locations centrometric to IGF2. The first cluster is 200-400 kb from IGF2 and the second is several megabases away. Hence, genes located far from the translocation breakpoints are potentially deregulated by them. Here we provide the first evidence of alteration of imprinting in a translocation family, with biallelic expression of IGF2 and altered DNA replication patterns in the IGF2 region. Interestingly, H19 imprinting was normal, suggesting an H19-independent pathway to biallelic IGF2 transcription. DNA methylation in IGF2 remained monoallelic, suggesting that the mutation in this family had uncoupled allele-specific methylation from expression.

Genomic imprinting in mammals is an important genetic mechanism by which genes are expressed or repressed depending on which parent they have been inherited from. Some properties of the imprinting mechanism are already established; notably, some of the effects of imprinting on mammalian development can be explained by the phenotypic effects of a number of specific imprinted genes, which include major fetal growth factors. An evolutionary explanation of imprinting has also been suggested. Some of the molecular mechanisms of imprinting are known, and these include the modification of DNA and chromosomes in the form of DNA methylation and possibly heritable chromatin structures. Loss of imprinting or altered imprinting is implicated in a large number of genetic diseases and cancers. Many important issues remain to be resolved; these include the precise molecular mechanisms and, in particular, the nature of the primary imprints that are inherited from the parental gametes, and the genes that control the imprinting process. Isolation of the majority of imprinted genes and the elucidation of their phenotypic effects and physiology are major goals for the future. These studies will provide important insights into human genetics, and will connect evolutionary understanding with physiology, genetic disease and human behaviour.

Beckwith-Wiedemann syndrome is a rare condition (1/13,700 live births) occurring in both inherited and sporadic forms in the population. It is manifest as a fetal overgrowth syndrome, in which hypertrophy dominates the clinical picture. An additional complication is that these children are predisposed to a specific subset of childhood neoplasms, amongst which are Wilms' tumour and adrenocortical carcinoma. We report here the synthesis by an associated adrenal tumour of large quantities of a high molecular weight form of insulin-like growth factor II (IGF-II), associated with profound suppression of circulating IGFs in the patient's serum. As with other tumours of this type, the tumours showed loss of material on chromosome 11p.

Overstimulation by insulin-like growth factor II is implied in several overgrowth conditions and childhood cancers. We have therefore studied spatial and temporal expression patterns of the insulin-like growth factor II gene (IGF2) and the insulin-like growth factor type 1 receptor gene during normal human development (5.5 to 23.0 weeks postfertilization). The set of cell types with the most abundant IGF2 expression correlated strikingly to the organomegaly and tumor predisposition of the Beckwith-Wiedemann syndrome. Intrauterine growth and postnatal organ weights of a prematurely born child with a full-blown syndrome are presented. The cell type-specific IGF2 expression of these organs and of multifocal Wilms' tumors from two other children affected by the Beckwith-Wiedemann syndrome were also studied. The results clarify and extend previous findings concerning human prenatal IGF2 expression and are consistent with a short range overstimulatory role of locally produced IGF II ensuing after the first trimester in the Beckwith-Wiedemann syndrome.

We have examined insulin-like growth factor 1 receptor (IGF1R) gene expression for evidence of imprinting in 15 informative patients with embryonal tumours. Biallelic expression was observed in all but one sample of normal juvenile kidney and liver, and in 9/10 associated Wilms' tumours, 3/3 hepatoblastomas and 2/2 adrenal tumours. A single patient with Beckwith-Wiedemann Syndrome (BWS) demonstrated monoallelic expression of the maternally derived IGF1R allele in normal kidney, associated Wilms' tumour and in peripheral blood lymphocytes. The observed biallelic expression of the IGF1R gene in all but one patient strongly suggests that the human gene is not normally imprinted.

The Wiedemann-Beckwith syndrome (WBS) comprises an accumulation of multiple congenital anomalies. Exomphalos, macroglossia and gigantism are considered the most common manifestations, hence the alternative designation EMG-syndrome. The syndrome carries with it an increased risk of developing specific tumours. One of the more frequent metabolic changes is transient neonatal hypoglycaemia, the result of increased insulin secretion. Inheritance of the syndrome remains uncertain. Most cases are sporadic, but a number of familial cases have been reported. Present evidence suggests that WBS is an autosomal dominant trait with variable expressivity. This review summarizes the abundant literature on the subject and discusses recent molecular genetic developments that may explain the interrelationship between the clinical abnormalities, metabolic disturbances and development of tumours.

A follow up examination was carried out in a 10 year old child who had been diagnosed as having Wiedemann-Beckwith syndrome soon after birth. Macrosomy was seen to persist and body asymmetry and some dysmorphic aspects had become more pronounced over the years. The presence of moderate mental deficiency had led to difficulty in social relationships. In the prepuberty phase, the reappearance of hypoglycemia crises, which were also noted in the neonatal age, was of particular interest.