Silver-Russell Syndrome Phenotype Research Articles

Comprehensive molecular and clinical findings in 29 patients with multi-locus imprinting disturbance

BackgroundMulti-locus imprinting disturbance (MLID) with methylation defects in various differentially methylated regions (DMRs) has recently been identified in approximately 150 cases with imprinting disorders (IDs), and deleterious variants have been found in genes related to methylation maintenance of DMRs, such as those encoding proteins constructing the subcortical maternal complex (SCMC), in a small fraction of patients and/or their mothers. However, integrated methylation analysis for DMRs and sequence analysis for MLID-causative genes in MLID cases and their mothers have been performed only in a single study focusing on Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS) phenotypes.ResultsOf 783 patients with various IDs we have identified to date, we examined a total of 386 patients with confirmed epimutation and 71 patients with epimutation or uniparental disomy. Consequently, we identified MLID in 29 patients with epimutation confirmed by methylation analysis for multiple ID-associated DMRs using pyrosequencing and/or methylation-specific multiple ligation-dependent probe amplification. MLID was detected in approximately 12% of patients with BWS phenotype and approximately 5% of patients with SRS phenotype, but not in patients with Kagami-Ogata syndrome, Prader-Willi syndrome, or Angelman syndrome phenotypes. We next conducted array-based methylation analysis for 78 DMRs and whole-exome sequencing in the 29 patients, revealing hypomethylation-dominant aberrant methylation patterns in various DMRs of all the patients, eight probably deleterious variants in genes for SCMC in the mothers of patients, and one homozygous deleterious variant in ZNF445 in one patient. These variants did not show gene-specific methylation disturbance patterns. Clinically, neurodevelopmental delay and/or intellectual developmental disorder (ND/IDD) was observed in about half of the MLID patients, with no association with the identified methylation disturbance patterns and genetic variants. Notably, seven patients with BWS phenotype were conceived by assisted reproductive technology (ART).ConclusionsThe frequency of MLID was 7.5% (29/386) in IDs caused by confirmed epimutation. Furthermore, we revealed diverse patterns of hypomethylation-dominant methylation defects, nine deleterious variants, ND/IDD complications in about half of the MLID patients, and a high frequency of MLID in ART-conceived patients.

Executive functioning in adolescents and adults with Silver-Russell syndrome.

Silver-Russell syndrome (SRS) is a rare imprinting disorder characterized by prenatal and postnatal growth retardation. The two principal causes of SRS are loss of methylation on chromosome 11p15 (11p15 LOM) and maternal uniparental disomy of chromosome 7 (UPD(7)mat). Knowledge of the neuropsychological profile of SRS remains sparse and incomplete even if several difficulties related to attention and learning have been reported both in the literature and by patients with SRS. These difficulties could be the result of troubles in different cognitive domains, but also of executive dysfunction. Nevertheless, executive functioning has never been investigated, even though executive functions play an essential role in psychological development, and are extensively involved in daily life. The present study explored the executive functioning of individuals with SRS due to UPD(7)mat or 11p15 LOM. A battery of executive tasks assessing cognitive flexibility, inhibitory control, and working memory, together with a task assessing sustained attention, was administered to 19 individuals with SRS (13-39 years) and 19 healthy controls. The Behavior Rating Inventory of Executive Function was also completed by the participants' families. The results showed that participants with SRS had similar performance (z-scores) to our controls, in a context of normal intellectual efficiency. Group comparisons with Bayesian statistics showed a single difference between the 11p15 LOM and control groups: the completion time for part A of the Trail Making Test appeared to be longer in the 11p15 LOM group than in the control group. However, at the clinical level, several participants with SRS had clinically significant scores on various measures of EFs. Thus, the cognitive phenotype of SRS did not appear to be characterized by executive dysfunction, but individuals with SRS could be at high risk of developing executive dysfunction or attention-deficit/hyperactivity disorder. These results provide new insights into the neuropsychological profile of individuals with SRS.

Dysregulated H19/Igf2 expression disrupts cardiac-placental axis during development of Silver-Russell syndrome-like mouse models.

Dysregulation of the imprinted H19/IGF2 locus can lead to Silver-Russell syndrome (SRS) in humans. However, the mechanism of how abnormal H19/IGF2 expression contributes to various SRS phenotypes remains unclear, largely due to incomplete understanding of the developmental functions of these two genes. We previously generated a mouse model with humanized H19/IGF2 imprinting control region (hIC1) on the paternal allele that exhibited H19/Igf2 dysregulation together with SRS-like growth restriction and perinatal lethality. Here, we dissect the role of H19 and Igf2 in cardiac and placental development utilizing multiple mouse models with varying levels of H19 and Igf2. We report severe cardiac defects such as ventricular septal defects and thinned myocardium, placental anomalies including thrombosis and vascular malformations, together with growth restriction in mouse embryos that correlated with the extent of H19/Igf2 dysregulation. Transcriptomic analysis using cardiac endothelial cells of these mouse models shows that H19/Igf2 dysregulation disrupts pathways related to extracellular matrix and proliferation of endothelial cells. Our work links the heart and placenta through regulation by H19 and Igf2, demonstrating that accurate dosage of both H19 and Igf2 is critical for normal embryonic development, especially related to the cardiac-placental axis.

Temple Syndrome: Clinical Findings, Body Composition and Cognition in 15 Patients.

Temple syndrome (TS14) is an imprinting disorder caused by a maternal uniparental disomy of chromosome 14 (UPD(14)mat), paternal deletion of 14q32 or an isolated methylation defect of the MEG3-DMR. Studies on phenotypical characteristics in TS14 are scarce and patients with TS14 often experience delay in diagnosis, which has adverse effects on their health. TS14 is often characterized as either Prader-Willi-like, Silver-Russell-like or as a Silver-Russell spectrum disorder. This study describes 15 patients with TS14 who visited the Dutch Reference Center for Prader-Willi-like from December 2018 to January 2022. Eight patients had UPD(14)mat and seven a methylation defect. The most common symptoms were intra-uterine growth retardation (IUGR) (100%), hypotonia (100%), precocious puberty (89%), small for gestational age (SGA) birth (67%), tube feeding after birth (53%) and psycho-behavioral problems (53%). Median (interquartile range (IQR)) IQ was 91.5 (84.25; 100.0), whilst many patients were enrolled in special education (54%). The median (IQR) fat mass % (FM%) SDS was 2.53 (2.26; 2.90) and lean body mass (LBM) SDS -2.03 (-3.22; -1.28). There were no significant differences in clinical characteristics between patients with a UPD(14)mat and a methylation defect. Our patients share a distinct phenotype consisting of IUGR, SGA birth, precocious puberty, hypotonia, tube feeding after birth, psycho-behavioral problems and abnormal body composition with a high FM% and low LBM. Whilst similarities with Prader-Willi syndrome (PWS) and Silver-Russell syndrome (SRS) exist, TS14 is a discernible syndrome, deserving a tailored clinical approach. Testing for TS14 should be considered in patients with a PWS or SRS phenotype in infancy if PWS/SRS testing is negative.

Blended Phenotype of Silver-Russell Syndrome and SPG50 Caused by Maternal Isodisomy of Chromosome 7.

ObjectiveUniparental isodisomy can lead to blended phenotypes of imprinting disorders and autosomal recessive diseases. To determine whether a complex neurodevelopmental disorder was caused by uniparental isodisomy, a detailed clinical and molecular characterization was performed.MethodsA combination of clinical, molecular, and imaging data and functional studies in patient-derived fibroblasts.ResultsWe report a 4-year-old female with a blended, complex phenotype of Silver-Russell syndrome (SRS) and hereditary spastic paraplegia type 50 (SPG50) caused by total maternal isodisomy of chromosome 7 (UPiD(7)mat) and a loss-of-function variant in AP4M1 (NM_00472.3: c.59-1G>C, IVS1-1G>C). Functional studies in patient-derived fibroblasts confirmed the loss of adaptor protein complex 4 function. Distinctive facial features, intrauterine growth restriction, short stature, feeding difficulties, and severe gastroesophageal reflux were consistent with SRS. Features associated with SPG50 included early-onset epilepsy, episodes of stereotypical laughter, and thinning of the corpus callosum and ventriculomegaly on brain MRI. Symptoms shared by both syndromes such as developmental delay, short stature, and axial and appendicular hypotonia were also present. Notably, other common manifestations of SPG50 such as microcephaly or spasticity had not developed yet.ConclusionsThis case highlights that atypical clinical features in patients with well-described imprinting disorders should lead to investigations for recessive conditions caused by variants in genes that localize to the region of homozygosity.

Recombinant Chromosome 7 Driven by Maternal Chromosome 7 Pericentric Inversion in a Girl with Features of Silver-Russell Syndrome

Maternal uniparental disomy of chromosome 7 is present in 5–10% of patients with Silver-Russell syndrome (SRS), and duplication of 7p including GRB10 (Growth Factor Receptor-Bound Protein 10), an imprinted gene that affects pre-and postnatal growth retardation, has been associated with the SRS phenotype. Here, we report on a 17 year old girl referred to array-CGH analysis for short stature, psychomotor delay, and relative macrocephaly. Array-CGH analysis showed two copy number variants (CNVs): a ~12.7 Mb gain in 7p13-p11.2, involving GRB10 and an ~9 Mb loss in 7q11.21-q11.23. FISH experiments performed on the proband’s mother showed a chromosome 7 pericentric inversion that might have mediated the complex rearrangement harbored by the daughter. Indeed, we found that segmental duplications, of which chromosome 7 is highly enriched, mapped at the breakpoints of both the mother’s inversion and the daughter’s CNVs. We postulate that pairing of highly homologous sequences might have perturbed the correct meiotic chromosome segregation, leading to unbalanced outcomes and acting as the putative meiotic mechanism that was causative of the proband’s rearrangement. Comparison of the girl’s phenotype to those of patients with similar CNVs supports the presence of 7p in a locus associated with features of SRS syndrome.

Contribution of gene mutations to Silver-Russell syndrome phenotype: multigene sequencing analysis in 92 etiology-unknown patients

BackgroundSilver-Russell syndrome (SRS) is characterized by growth failure and dysmorphic features. Major (epi)genetic causes of SRS are loss of methylation on chromosome 11p15 (11p15 LOM) and maternal uniparental disomy of chromosome 7 (upd(7)mat). However, IGF2, CDKN1C, HMGA2, and PLAG1 mutations infrequently cause SRS. In addition, other imprinting disturbances, pathogenic copy number variations (PCNVs), and monogenic disorders sometimes lead to SRS phenotype. This study aimed to clarify the frequency and clinical features of the patients with gene mutations among etiology-unknown patients with SRS phenotype.ResultsMultigene sequencing was performed in 92 out of 336 patients referred to us for genetic testing for SRS. The clinical features of the patients were evaluated based on the Netchine-Harbison clinical scoring system. None of the patients showed 11p15 LOM, upd(7)mat, abnormal methylation levels for six differentially methylated regions (DMRs), namely, PLAGL1:alt-TSS-DMR on chromosome 6, KCNQ1OT1:TSS-DMR on chromosome 11, MEG3/DLK1:IG-DMR on chromosome 14, MEG3:TSS-DMR on chromosome 14, SNURF:TSS-DMR on chromosome 15, and GNAS A/B:TSS-DMR on chromosome 20, PCNVs, or maternal uniparental disomy of chromosome 16. Using next-generation sequencing and Sanger sequencing, we screened four SRS-causative genes and 406 genes related to growth failure and/or skeletal dysplasia. We identified four pathogenic or likely pathogenic variants in responsible genes for SRS (4.3%: IGF2 in two patients, CDKN1C, and PLAG1), and five pathogenic variants in causative genes for known genetic syndromes presenting with growth failure (5.4%: IGF1R abnormality (IGF1R), SHORT syndrome (PIK3R1), Floating-Harbor syndrome (SRCAP), Pitt-Hopkins syndrome (TCF4), and Noonan syndrome (PTPN11)). Functional analysis indicated the pathogenicity of the CDKN1C variant. The variants we detected in CDKN1C and PLAG1 were the second and third variants leading to SRS, respectively. Our patients with CDKN1C and PLAG1 variants showed similar phenotypes to previously reported patients. Furthermore, our data confirmed IGF1R abnormality, SHORT syndrome, and Floating-Harbor syndrome are differential diagnoses of SRS because of the shared phenotypes among these syndromes and SRS. On the other hand, the patients with pathogenic variants in causative genes for Pitt-Hopkins syndrome and Noonan syndrome were atypical of these syndromes and showed partial clinical features of SRS.ConclusionsWe identified nine patients (9.8%) with pathogenic or likely pathogenic variants out of 92 etiology-unknown patients with SRS phenotype. This study expands the molecular spectrum of SRS phenotype.

Lack of hemizygosity for the insulin-like growth factor I receptor gene in a quantitative study of 33 Silver Russell syndrome probands and their families.

Previous studies have shown that individuals with a deletion of 15q26.1-->qter, which includes the insulin-like growth factor I receptor (IGFIR) gene, may exhibit phenotypic characteristics similar to those individuals with Silver-Russell Syndrome (SRS). Thirty-three SRS probands, with normal karyotypes, and their parents were investigated for the presence of both copies of IGFIR by gene dosage analysis of Southern blot hybridisation. All 33 SRS probands have both copies of IGFIR. Tetranucleotide repeat marker analysis for three locations on 15q also ruled out other deletions in these regions for those markers that were informative. Two important functional regions of IGFIR were also investigated for DNA mutations, using single-stranded conformational polymorphism analysis. No mutations were found in the cysteine-rich region involved in ligand binding (exon 3) or the ATP binding region (exon 16) which could contribute to the SRS phenotype. However, a silent mutation in the third position of one of the codons in the ATP region (3174G-->A, 1013 Glu-->Glu) was found.

A case report and review of the literature indicate that HMGA2 should be added as a disease gene for Silver-Russell syndrome

Patients with Silver-Russell syndrome (SRS), a syndromic growth retardation syndrome, usually harbor an epimutation at chromosome 11p15 or a maternal uniparental disomy of chromosome 7. However, to date the genetic cause remains unknown in around 40% of SRS cases, suggesting genetic heterogeneity and involvement of other genes.We present a 4-year-old female patient with the clinical diagnosis of SRS and negative results in common genetic SRS diagnostics. Whole exome sequencing identified a de novo heterozygous 7.3 kb deletion on chromosome 12q14.3 including exon 1 and 2 of HMGA2.HMGA2 encodes an architectural transcription factor and has already been linked to body size variations in various genome-wide association studies and mouse models. Reviewing the literature, we found additional four patients with a phenotype of SRS harboring point mutations or structural variants involving HMGA2. We conclude that genetic testing of HMGA2 should be considered in routine diagnostics in patients with the suspicion of SRS.

Behavioural abnormalities in a novel mouse model for Silver Russell Syndrome.

Silver Russell Syndrome (SRS) syndrome is an imprinting disorder involving low birth weight with complex genetics and diagnostics. Some rare SRS patients carry maternally inherited microduplications spanning the imprinted genes CDKN1C, PHLDA2, SLC22A18 and KCNQ1, suggesting that overexpression of one of more of these genes contributes to the SRS phenotype. While this molecular alteration is very rare, feeding difficulties are a very common feature of this condition. Given that SRS children also have very low body mass index, understanding the underpinning biology of the eating disorder is important, as well as potential co-occurring behavioural alterations. Here, we report that a mouse model of this microduplication exhibits a number of behavioural deficits. The mice had a blunted perception of the palatability of a given foodstuff. This perception may underpin the fussiness with food. We additionally report hypoactivity, unrelated to anxiety or motoric function, and a deficit in the appropriate integration of incoming sensory information. Importantly, using a second genetic model, we were able to attribute all altered behaviours to elevated expression of a single gene, Cdkn1c. This is the first report linking elevated Cdkn1c to altered behaviour in mice. Importantly, the findings from our study may have relevance for SRS and highlight a potentially underreported aspect of this disorder.

Humanized H19/Igf2 locus reveals diverged imprinting mechanism between mouse and human and reflects Silver–Russell syndrome phenotypes

Genomic imprinting affects a subset of genes in mammals, such that they are expressed in a monoallelic, parent-of-origin-specific manner. These genes are regulated by imprinting control regions (ICRs), cis-regulatory elements that exhibit allele-specific differential DNA methylation. Although genomic imprinting is conserved in mammals, ICRs are genetically divergent across species. This raises the fundamental question of whether the ICR plays a species-specific role in regulating imprinting at a given locus. We addressed this question at the H19/insulin-like growth factor 2 (Igf2) imprinted locus, the misregulation of which is associated with the human imprinting disorders Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS). We generated a knock-in mouse in which the endogenous H19/Igf2 ICR (mIC1) is replaced by the orthologous human ICR (hIC1) sequence, designated H19(hIC1) We show that hIC1 can functionally replace mIC1 on the maternal allele. In contrast, paternally transmitted hIC1 leads to growth restriction, abnormal hIC1 methylation, and loss of H19 and Igf2 imprinted expression. Imprint establishment at hIC1 is impaired in the male germ line, which is associated with an abnormal composition of histone posttranslational modifications compared with mIC1. Overall, this study reveals evolutionarily divergent paternal imprinting at IC1 between mice and humans. The conserved maternal imprinting mechanism and function at IC1 demonstrates the possibility of modeling maternal transmission of hIC1 mutations associated with BWS in mice. In addition, we propose that further analyses in the paternal knock-in H19(+/hIC1) mice will elucidate the molecular mechanisms that may underlie SRS.

NSD1 duplication in Silver-Russell syndrome (SRS): molecular karyotyping in patients with SRS features.

Silver-Russell syndrome (SRS) is a growth retardation syndrome characterized by intrauterine and postnatal growth retardation, relative macrocephaly and protruding forehead, body asymmetry and feeding difficulties. Nearly 50% of cases show a hypomethylation in 11p15.5, in 10% maternal uniparental disomy of chromosome 7 is present. A significant number of patients with SRS features also exhibit chromosomal aberrations. We analyzed 43 individuals referred for SRS genetic testing by molecular karyotyping. Pathogenic variants could be detected in five of them, including a NSD1 duplication in 5q35 and a 14q32 microdeletion. NSD1 deletions are detectable in overgrowth disorders (Sotos syndrome and Beckwith-Wiedemann syndrome), whereas NSD1 duplications are associated with growth retardation. The 14q32 deletion is typically associated with Temple syndrome (TS14), but the identification of a patient in our cohort reflects the clinical overlap between TS14 and SRS. As determination of molecular subtypes is the basis for a directed counseling and therapy, the identification of pathogenic variants in >10% of the total cohort of patients referred for SRS testing and in >16% of characteristic individuals with the characteristic SRS phenotype confirms the need to apply molecular karyotyping in this cohort.

Examinations of maternal uniparental disomy and epimutations for chromosomes 6, 14, 16 and 20 in Silver-Russell syndrome-like phenotypes.

BackgroundSilver-Russell syndrome (SRS) is a growth retardation disorder with a very broad molecular and clinical spectrum. Whereas the association of SRS with imprinting disturbances of chromosomes 11p15.5 and 7 is generally accepted, there are controversial discussions on the involvement of other molecular changes. The recent reports on the occurrence of maternal uniparental disomies of chromosomes 6, 16 and 20 (upd(6, 16, 20)mat), as well as 14q32 imprint alterations in patients with SRS phenotypes raise the question on the involvement of these mutations in the etiology of SRS.MethodsA cohort of 54 growth retarded patients with SRS features was screened for aberrant methylation patterns of chromsomes 6, 14, 16 and 20.ResultsOne carrier of a 14q32 epimutation was identified whereas epimutations and maternal UPD for chromosomes 6, 16 and 20 were excluded.ConclusionsOur data and those from the literature confirm that 14q32 disturbances significantly contribute to the mutation spectrum in this cohort. Furthermore, maternal uniparental disomy of chromosomes 6, 16 and 20 can be observed, but are rare. In case they occur they can be regarded as causative for clinical features.

Humanized H19/Igf2 locus reveals diverged imprinting mechanism between mouse and human and reflects Silver–Russell syndrome phenotypes

Humanized H19/Igf2 locus reveals diverged imprinting mechanism between mouse and human and reflects Silver–Russell syndrome phenotypes

A splicing mutation of the HMGA2 gene is associated with Silver-Russell syndrome phenotype.

Silver-Russell syndrome (SRS) is a heterogeneous disorder characterized by intrauterine and post-natal growth retardation, dysmorphic facial features and body asymmetry. About 50% of the patients carry (epi)genetic alterations involving chromosomes 7 or 11.The high proportion of patients with unidentified molecular etiology suggests the involvement of other genes. Interestingly, SRS patients share clinical features with the 12q14 microdeletion syndrome, characterized by several deletions with a 2.6 Mb region of overlap. Among the genes present in this interval, high mobility AT-hook 2 (HMGA2) appears to be the most likely cause of the growth deficiency, due to its described growth control function. To define the role of HMGA2 in SRS, we looked for 12q14 chromosome imbalances and HMGA2 mutations in a cohort of 45 patients with growth retardation and SRS-like phenotype but no 11p15 (epi)mutations or maternal uniparental disomy of chromosome 7 (matUPD7). We identified a novel 7 bp intronic deletion in HMGA2 present in heterozygosity in the proband and her mother both displaying the typical features of SRS. We demonstrated that the deletion affected normal splicing, indicating that it is a likely cause of HMGA2 deficiency. This study provides the first evidence that a loss-of-function mutation of HMGA2 can be associated with a familial form of SRS. We suggest that HMGA2 mutations leading to haploinsufficiency should be investigated in the SRS patients negative for the typical 11p15 (epi)mutations and matUPD7.

A cryptic familial rearrangement of 11p15.5, involving both imprinting centers, in a family with a history of short stature

Silver-Russell syndrome (SRS) is a heterogeneous disorder characterized by intrauterine and postnatal growth retardation, dysmorphic facial features and body asymmetry. Both hypomethylation of the telomeric imprinting control region 1 (ICR1) at 11p15.5 and maternal duplication of 11p15.5 have been implicated in the etiology of this disorder. Here we report the origin and segregation of the first reported between-arm intrachromosomal insertion of 11p15.5 that encompasses both ICR1 and ICR2 in a multigenerational family with a history of short stature. One (or any odd number) crossover within the centromeric segment during meiosis would produce recombinant chromosomes; one with a duplication of the inserted segment and the other a deletion. In this 4-generation family, there were six instances of transmission of the recombinant chromosome with duplication of the11p15.5 segment, which leads to a SRS phenotype when maternally inherited and a Beckwith-Wiedemann phenotype when paternally transmitted. The size of the duplicated region is ~1.9 Mb as determined by microarray analysis. This study provides further evidence that maternally inherited duplications of 11p15.5 result in a SRS phenotype that includes short stature and other variable features. The methylation status of the extra copy of the duplicated region of 11p15.5 ultimately predicts the resulting phenotype. Thus, the different phenotype based on parental mode of transmission is of importance in the genetic counseling of these patients.

Collagenopathy with a phenotype resembling silver–russell syndrome phenotype

Collagenopathy with a phenotype resembling silver–russell syndrome phenotype

What is the Evidence for Causal Epigenetic Influences on the Silver–Russell Syndrome Phenotype?

Clinical definition of Silver–Russell sydrome In 1953 the American pediatrician Henry Silver reported two children with low birthweight, postnatal growth restriction and growth asymmetry [1]. Without knowing of these two cases, in the following year, Alexander Russell from the UK described five similar cases [2]. This group of patients became known as having Silver–Russell syndrome (SRS) or, in the US, Russell–Silver syndrome [OMIM: 180860]. Since these initial reports, several hundred cases have been described in the literature. A predominantly sporadic condition, common features include preand post-natal growth restriction, relative macrocephaly, growth asymmetry and a characteristic facial appearance. The condition is phenotypically variable, making confident clinical diagnosis difficult in some cases [3,4]. Thus in 1999, based on their ana lysis of 57 cases, Price and colleagues proposed a set of clinical diagnostic criteria, at least four of which should be present for a diagnosis of ‘classical SRS’: birthweight >2 SD below the mean, short stature at the time of diagnosis, weight >2 SD below the mean; limb, body or facial asymmetry and fifth finger clinodactyly [5].

Role of Epigenetics in the Placenta: Alterations in DNA Promoter Mmethylation and Limprinted Genes

Many researchers are focusing on epigenetic regulation in the placenta. Because the proper development and function of the placenta are crucial for the normal healthy growth and survival of the developing fetus, the study of epigenetic alterations is providing critical insights into the biology of fetal development and the pathogenesis of complications in pregnancy. One epigenetic alteration is genomic imprinting. Alleles from both the father and mother are necessary for normal human and placental development. For example, the paternally expressed IGF2 gene and maternally expressed H19 gene are located in 11p15.5 and they are coordinately regulated by differentially methylated regions (DMRs). The main phenotype of Silver-Russell syndrome is severe fetal growth retardation (FGR) that is caused by a reduction in IGF2 transcription as a result of a loss of methylation at the H19 DMR. Hypermethylation at the H19 DMR is found in 30% of cases of Beckwith-Wiedemann syndrome and the overgrowth phenotype. The other main mechanism is a promoter DNA methylation. Hypomethylation of a promoter of the SERPINA3 gene in the placenta is associated with FGR and preeclampsia. These clues to the epigenetic phenomena involved in the processes of human development and disease in pregnancy have been found in recent years.

The KCNQ1OT1 imprinting control region and non-coding RNA: new properties derived from the study of Beckwith–Wiedemann syndrome and Silver–Russell syndrome cases

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.