Search

Silver-Russel syndrome (SRS) is a representative imprinting disorder (ID) characterized by growth failure and diagnosed by clinical features. Recently, international consensus has recommended using the Netchine-Harbison clinical scoring system (NH-CSS) as clinical diagnostic criteria. Loss of methylation of H19/IGF2:intergenic differentially methylated region (H19LOM) and maternal uniparental disomy chromosome 7 (UPD(7)mat) are common etiologies of SRS; however, other IDs, pathogenic variants (PVs) of genes, and pathogenic copy number variants (PCNVs) have been reported in patients meeting NH-CSS. To clarify the frequency and clinical characteristics of each etiology, we conducted (epi)genetic analysis in 173 patients satisfying NH-CSS. H19LOM and UPD(7)mat were identified in 34.1%. PCNVs, other IDs, and PVs were in 15.0%. Patients with all six NH-CSS items were most frequently observed with H19LOM and UPD(7)mat. This study confirmed the suitability of NH-CSS as clinical diagnostic criteria, the (epi)genetic heterogeneity of SRS, and showed the necessity of further discussion regarding the "SRS spectrum".

Objective: Silver–Russell syndrome (SRS) causes short stature. Growth hormone (GH) treatment aims to increase adult height. However, data are limited on the long-term outcomes of GH in patients with molecularly confirmed SRS. This study evaluated height, body mass index (BMI) and GH treatment in molecularly confirmed SRS. Design: An observational study with retrospective data collection. Patients: Individuals with molecularly confirmed SRS aged ≥13 years. Measurements: Data were collected on height, height gain (change in height standard deviation score [SDS] from childhood to final or near-final height), BMI and gain in BMI (from childhood to adulthood) and previous GH treatment. Results: Seventy-one individuals (40 female) were included. The median age was 22.0 years (range 13.2–69.7). The molecular diagnoses: H19/IGF2:IG-DMR LOM in 80.3% (57/71); upd(7)mat in 16.9% (12/71) and IGF2 mutation in 2.8% (2/71). GH treatment occurred in 77.5% (55/71). Total height gain was greater in GH-treated individuals (median 1.53 SDS vs. 0.53 SDS, p =.007), who were shorter at treatment initiation (−3.46 SDS vs. −2.91 SDS, p =.04) but reached comparable heights to GH-untreated individuals (−2.22 SDS vs. −2.74 SDS, p =.7). In GH-treated individuals, BMI SDS was lower at the most recent assessment (median −1.10 vs. 1.66, p =.002) with lower BMI gain (2.01 vs. 3.58, p =.006) despite similar early BMI SDS to GH-untreated individuals (median −2.65 vs. −2.78, p =.3). Conclusions: These results support the use of GH in SRS for increasing height SDS. GH treatment was associated with lower adult BMI which may reflect improved metabolic health even following discontinuation of therapy.

BackgroundHemihyperplasia and hemihypoplasia result in leg length discrepancy (LLD) by causing skeletal asymmetry. Beckwith–Wiedemann syndrome (BWS) and Silver–Russell syndrome (SRS) are opposite growth-affecting disorders caused by opposite epigenetic alterations at the same chromosomal locus, 11p15, to induce hemihyperplasia and hemihypoplasia, respectively. Because of their somatic mosaicism, BWS and SRS show a wide spectrum of clinical phenotypes. We evaluated the underlying epigenetic alterations and potential epigenotype-phenotype correlations, focusing on LLD, in a group of individuals with isolated hemihyperplasia/hemihypoplasia.ResultsWe prospectively collected paired blood-tissue samples from 30 patients with isolated hemihyperplasia/hemihypoplasia who underwent surgery for LLD. Methylation-specific multiplex-ligation-dependent probe amplification assay (MS-MLPA) and bisulfite pyrosequencing for differentially methylated regions 1 and 2 (DMR1 and DMR2) on chromosome 11p15 were performed using the patient samples. Samples from patients showing no abnormalities in MS-MLPA or bisulfite pyrosequencing were analyzed by single nucleotide polymorphism (SNP) microarray andCDKN1CSanger sequencing. We introduced a metric named as the methylation difference, defined as the difference in DNA methylation levels between DMR1 and DMR2. The correlation between the methylation difference and the predicted LLD at skeletal maturity, calculated using a multiplier method, was evaluated. Predicted LLD was standardized for stature. Ten patients (33%) showed epigenetic alterations in MS-MLPA and bisulfite pyrosequencing. Of these, six and four patients had epigenetic alterations related to BWS and SRS, respectively. The clinical diagnosis of hemihyperplasia/hemihypoplasia was not compatible with the epigenetic alterations in four of these ten patients. No patients showed abnormalities in SNP array or theirCDKN1Csequences. The standardized predicted LLD was moderately correlated with the methylation difference using fat tissue (r = 0.53;p = 0.002) and skin tissue (r = 0.50;p = 0.005) in all patients.ConclusionsIsolated hemihyperplasia and hemihypoplasia can occur as a spectrum of BWS and SRS. Although the accurate differentiation between isolated hemihyperplasia and isolated hemihypoplasia is important in tumor surveillance planning, it is often difficult to clinically differentiate these two diseases without epigenetic tests. Epigenetic tests may play a role in the prediction of LLD, which would aid in treatment planning.

Epigenetic and genomic imprinting alterations of the 11p15.5 region cause excessive or deficient growth, which result in Beckwith-Wiedemann syndrome (BWS) or Silver-Russell syndrome (SRS), respectively.To evaluate the methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) methylation analysis technique in the diagnosis of BWS and SRS.11p15.5 methylation and variants were evaluated in patients with clinical diagnosis of BWS and SRS using the MS-MLPA technique in peripheral blood DNA.Paternal uniparental disomy and loss of maternal IC2 methylation were identified in two patients with BWS who had omphalocele and macroglossia, respectively. Paternal IC1hypomethylation was recorded in two patients with SRS of classic phenotype.Adequate genotype-phenotype correlation was observed with the methylation defects that were identified, which confirms the usefulness of MLPA as a first-line study in patients diagnosed with BWS and SRS.Las alteraciones epigenéticas y genómicas de la región improntada 11p15.5 producen crecimiento excesivo o deficiente, que se manifiesta como síndrome de Beckwith-Wiedemann o síndrome de Silver-Russell, respectivamente.Evaluar la técnica de análisis de metilación MLPA (MS-MLPA, methylation-specific multiplex ligation-dependent probe amplification) en el diagnóstico de los síndromes de Beckwith-Wiedemann y de Silver-Russell.Se evaluó la metilación y las variantes de 11p15.5 en pacientes con diagnóstico clínico de síndrome de Beckwith-Wiedemann y síndrome de Silver-Russell mediante la técnica MS-MLPA en ADN de sangre periférica.Se identificó disomía uniparental paterna y pérdida de metilación del IC2 materno en dos pacientes con síndrome de Beckwith-Wiedemann, quienes presentaron onfalocele y macroglosia, respectivamente. Se registró hipometilación paterna del IC1 en dos pacientes con síndrome de Silver-Russell de fenotipo clásico.Se observó adecuada correlación genotipo-fenotipo con los defectos de metilación encontrados, lo que confirma la utilidad del MLPA como estudio de primera línea en pacientes con diagnóstico de síndrome de Beckwith-Wiedemann y síndrome de Silver-Russell.

Silver-Russell syndrome is an imprinting disorder characterised by pre- and post-natal growth retardation and several heterogeneous molecular defects affecting different human genomic loci. In the majority of cases, the molecular defect is the loss of methylation (LOM) of the

Silver–Russell syndrome (SRS) is a rare imprinting disorder associated with prenatal and postnatal growth retardation. Loss of methylation (LOM) on chromosome 11p15 is observed in 40 to 60% of patients and maternal uniparental disomy (mUPD) for chromosome 7 (upd(7)mat) in ~5 to 10%. Patients with LOM or mUPD 14q32 can present clinically as SRS. Delta like non-canonical Notch ligand 1 (DLK1) is one of the imprinted genes expressed from chromosome 14q32. Dlk1-null mice display fetal growth restriction (FGR) but no genetic defects of DLK1 have been described in human patients born small for gestational age (SGA). We screened a cohort of SGA patients with a SRS phenotype for DLK1 variants using a next-generation sequencing (NGS) approach to search for new molecular defects responsible for SRS. Patients born SGA with a clinical suspicion of SRS and normal methylation by molecular testing at the 11p15 or 14q32 loci and upd(7)mat were screened for DLK1 variants using targeted NGS. Among 132 patients, only two rare variants of DLK1 were identified (NM_003836.6:c.103 G > C (p.(Gly35Arg) and NM_003836.6: c.194 A > G p.(His65Arg)). Both variants were inherited from the mother of the patients, which does not favor a role in pathogenicity, as the mono-allelic expression of DLK1 is from the paternal-inherited allele. We did not identify any pathogenic variants in DLK1 in a large cohort of SGA patients with a SRS phenotype. DLK1 variants are not a common cause of SGA.

BackgroundSilver-Russell syndrome (SRS) is an imprinting disorder characterised by prenatal and postnatal growth restriction, but its clinical features are non-specific and its differential diagnosis is broad. Known molecular causes of SRS include imprinting disturbance, single nucleotide variant (SNV), CNV or UPD affecting several genes; however, up to 40% of individuals with a clinical diagnosis of SRS currently receive no positive molecular diagnosis.MethodsTo determine whether whole-genome sequencing (WGS) could uncover pathogenic variants missed by current molecular testing, we analysed data of 72 participants recruited to the 100,000 Genomes Project within the clinical category of SRS.ResultsIn 20 participants (27% of the cohort) we identified genetic variants plausibly accounting for SRS. Coding SNVs were identified in genes including CDKN1C, IGF2, IGF1R and ORC1. Maternal-effect variants were found in mothers of five participants, including two participants with imprinting disturbance and one with multilocus imprinting disorder. Two regions of homozygosity were suggestive of UPD involving imprinted regions implicated in SRS and Temple syndrome, and three plausibly pathogenic CNVs were found, including a paternal deletion of PLAGL1. In 48 participants with no plausible pathogenic variant, unbiased analysis of SNVs detected a potential association with STX4.ConclusionWGS analysis can detect UPD, CNV and SNV and is potentially a valuable addition to diagnosis of SRS and related growth-restricting disorders.

ObjectiveThe psychosocial impact of growing up with Silver-Russell syndrome (SRS), characterised by growth failure and short stature in adulthood, has been explored in adults; however, there are no accounts of contemporary lived experience in adolescents. Such data could inform current healthcare guidance and transition to adult services. We aimed to explore the lived experience of adolescents with SRS.Design/setting/patientsIn-depth, semi-structured interviews were conducted between January 2015 and October 2016 with a sample of eight adolescents aged 13–18 (five girls) with genetically confirmed SRS from the UK. Qualitative interviews were transcribed and coded to identify similarities and differences using thematic analysis; codes were then grouped to form overarching themes.ResultsWe identified four themes from the interview data: (1) the psychosocial challenges of feeling and looking different; (2) pain, disability and fatigue; (3) anticipated stigma; and (4) building resilience and acceptance. Despite adolescents accepting SRS in their lives, they described ongoing psychosocial challenges and anticipated greater problems to come, such as stigma from prospective employers.ConclusionsAdolescents with SRS may experience psychosocial difficulties from as young as 10 years old related to feeling and looking different; pain, disability and fatigue; anticipated stigma; and future challenges around employment. We discuss these findings in relation to recommendations for the care of adolescents with SRS to prepare them for adult life.

A Silver–Russell-szindróma jellegzetes minor anomáliák mellett (relatív macrocephalia, kiemelkedő homlok, kék sclera, lefelé ívelő szájzug, micrognathia, alacsonyan ülő fülek, illetve arc-, skeletalis és végtagi aszimmetria) súlyos, méhen belüli és születést követő növekedési zavarral jár. Az endokrin rendszert érintő eltérések is kiemelt jelentőségűek. Kialakulásának molekuláris háttere összetett, de a leggyakrabban a 11-es kromoszóma és/vagy a 7-es kromoszóma Silver–Russell-szindróma szempontjából kritikus régióinak érintettsége okozza. A molekuláris géndiagnosztika mellett a Netchine–Harbison-féle klinikai diagnosztikai pontrendszer segíti a diagnózis felállítását. Bár a tünetegyüttes többnyire sporadikus megjelenésű, rendkívül ritka familiáris halmozódást bemutató esetünkben a négy testvérből három gyermeknél Silver–Russell-szindróma került felismerésre. A Silver–Russell-szindróma korai, lehetőleg már újszülöttkori diagnosztizálása kulcsfontosságú a megfelelő táplálásvezetés, a korai fejlesztés, majd a növekedésihormon-kezelés időben történő elkezdése szempontjából. A betegek gondozása és megfelelő utánkövetése kiemelkedő jelentőségű a szindrómához társuló potenciális szövődmények időben történő felismerése és megfelelő kezelése céljából. Orv Hetil. 2022; 163(45): 1775–1781.

ContextData on pubertal timing in Silver Russell syndrome (SRS) are limited.Design and methodsRetrospective observational study including twenty-three SRS patients [11p15 loss of methylation, (11p15 LOM, n=10) and maternal uniparental disomy of chromosome 7 (mUPD7, n=13)] and 21 small for gestational age (SGA). Clinical (thelarche in females; testis volume ≥ 4 ml in males; pubarche), BMI SD trend from the age of 5 to 9 years to the time of puberty, biochemical parameters of puberty onset [Luteinizing hormone (LH), 17-β-estradiol, testosterone], and bone age progression were evaluatedResultsPubertal onset and pubarche occurred significantly earlier in children with SRS than in SGA (p 0.03 and p 0.001, respectively) and clinical signs of puberty onset occurred earlier in mUPD7 than in 11p15LOM group (p 0.003). Five SRS children experienced central precocious puberty and LH, 17-β-estradiol, testosterone were detected earlier in SRS than in SGA (p 0.01; p 0.0001). Bone age delay in SRS children was followed by rapid advancement; the delta between bone age and chronological age in SRS group became significantly higher than in SGA group at the age of 9-11 years (p 0.007). 11p15LOM patients were underweight at the age of 5 years and showed a progressive normalization of BMI that was significantly higher than in mUPD7 (p 0.04) and SGA groups (p 0.03) at puberty onset.ConclusionTiming of puberty is affected in SRS and occurred earlier in mUPD7 compared to 11p15LOM. The impact of early puberty on adult height and metabolic status deserves long-term evaluation.

Silver Russell syndrome (SRS) is a congenital disorder characterised by intrauterine growth retardation (IUGR), feeding difficulties and postnatal growth retardation. In a small number of cases PLAG1 variants have been described (OMIM #618907). PLAG1 haploinsufficiency decreases IGF2 expression and produces a Silver Russell syndrome like phenotype. Here, we describe the phenotype and molecular features of a 26 months girl with clinical features of SRS and a de novo 2.1 Mb deletion encompassing PLAG1 is reported in association with clinical features suggestive of SRS. This manuscript has been published in "Clinical Dysmorphology". https://journals.lww.com/clindysmorphol/Abstract/2021/10000/Silver_Russell_syndrome_in_a_preterm_girl_with.7.aspxMust be cited as follows: Fernandez-Fructuoso JR, De la Torre-Sandoval C, Harbison MD, Chantot-Bastaraud S, Temple K, Lloreda-Garcia JM, Olmo-Sanchez M, Netchine I. Silver Russell syndrome in a preterm girl with 8q12.1 deletion encompassing PLAG1. Clin Dysmorphol. 2021 Oct 1;30(4):194-196. doi: 10.1097/MCD.0000000000000375. PMID: 34480472.

Background(Epi)genetic disorders associated with small-for-gestational-age with short stature (SGA-SS) include imprinting disorders (IDs). Silver-Russell syndrome (SRS) is a representative ID in SGA-SS and has heterogenous (epi)genetic causes.Subjects and MethodsTo clarify the contribution of IDs to SGA-SS and the molecular and phenotypic spectrum of SRS, we recruited 269 patients with SGA-SS, consisting of 103 and 166 patients referred to us for genetic testing for SGA-SS and SRS, respectively. After excluding 20 patients with structural abnormalities detected by comparative genomic hybridization analysis using catalog array, 249 patients were classified into 3 subgroups based on the Netchine-Harbison clinical scoring system (NH-CSS), SRS diagnostic criteria. We screened various IDs by methylation analysis for differentially methylated regions (DMRs) related to known IDs. We also performed clinical analysis.ResultsThese 249 patients with SGA-SS were classified into the “SRS-compatible group” (n = 148), the “non-SRS with normocephaly or relative macrocephaly at birth group” (non-SRS group) (n = 94), or the “non-SRS with relative microcephaly at birth group” (non-SRS with microcephaly group) (n = 7). The 44.6% of patients in the “SRS-compatible group,” 21.3% of patients in the “non-SRS group,” and 14.3% in the “non-SRS with microcephaly group” had various IDs. Loss of methylation of the H19/IGF2:intergenic-DMR and uniparental disomy chromosome 7, being major genetic causes of SRS, was detected in 30.4% of patients in the “SRS-compatible group” and in 13.8% of patients in the “non-SRS group.”ConclusionWe clarified the contribution of IDs as (epi)genetic causes of SGA-SS and the molecular and phenotypic spectrum of SRS. Various IDs constitute underlying factors for SGA-SS, including SRS.

BackgroundZNF597, encoding a zinc-finger protein, is the human-specific maternally expressed imprinted gene located on 16p13.3. The parent-of-origin expression of ZNF597 is regulated by the ZNF597:TSS-DMR, of which only the paternal allele acquires methylation during postimplantation period. Overexpression of ZNF597 may contribute to some of the phenotypes associated with maternal uniparental disomy of chromosome 16 (UPD(16)mat), and some patients with UPD(16)mat presenting with Silver-Russell syndrome (SRS) phenotype have recently been reported.MethodsA 6-year-old boy presented with prenatal growth restriction, macrocephaly at birth, forehead protrusion in infancy and clinodactyly of the fifth finger. Methylation, expression, microsatellite marker, single nucleotide polymorphism array and trio whole-exome sequencing analyses were conducted.ResultsIsolated hypomethylation of the ZNF597:TSS-DMR and subsequent loss of imprinting and overexpression of ZNF597 were confirmed in the patient. Epigenetic alterations, such as UPD including UPD(16)mat and other methylation defects, were excluded. Pathogenic sequence or copy number variants affecting his phenotypes were not identified, indicating that primary epimutation occurred postzygotically.ConclusionWe report the first case of isolated ZNF597 imprinting defect, showing phenotypic overlap with SRS despite not satisfying the clinical SRS criteria. A novel imprinting disorder entity involving the ZNF597 imprinted domain can be speculated.

Silver-Russell syndrome (SRS) is a representative imprinting disorder. A major cause is the loss of methylation (LOM) of imprinting control region 1 (ICR1) within the IGF2/H19 domain. ICR1 is a gametic differentially methylated region (DMR) consisting of two repeat blocks, with each block including three CTCF target sites (CTSs). ICR1-LOM on the paternal allele allows CTCF to bind to CTSs, resulting in IGF2 repression on the paternal allele and biallelic expression of H19. We analysed 10 differentially methylated sites (DMSs) (ie, seven CTSs and three somatic DMRs within the IGF2/H19 domain, including two IGF2-DMRs and the H19-promoter) in five SRS patients with ICR1-LOM. Four patients showed consistent hypomethylation at all DMSs; however, one exhibited a peculiar LOM pattern, showing LOM at the centromeric region of the IGF2/H19 domain but normal methylation at the telomeric region. This raised important points: there may be a separate regulation of DNA methylation for the two repeat blocks within ICR1; there is independent control of somatic DMRs under each repeat block; sufficient IGF2 repression to cause SRS phenotypes occurs by LOM only in the centromeric block; and the need for simultaneous methylation analysis of several DMSs in both blocks for a correct molecular diagnosis.

Context Silver-Russell syndrome (SRS) is a clinical and molecular heterogeneous disorder associated with short stature, typical facial gestalt, and body asymmetry. Though molecular causes of SRS can be identified in a significant number of patients, about one-half of patients currently remain without a molecular diagnosis. However, determination of the molecular cause is required for a targeted treatment and genetic counselling. Objective The aim of this study was to corroborate the role of HMGA2 as an SRS-causing gene and reevaluate its mode of inheritance. Design, Setting, Patients Patients were part of an ongoing study aiming on SRS-causing genes. They were classified according to the Netchine-Harbison clinical scoring system, and DNA samples were investigated by whole exome sequencing. Common molecular causes of SRS were excluded before. Results Three novel pathogenic HMGA2 variants were identified in 5 patients from 3 SRS families, and fulfilling diagnostic criteria of SRS. For the first time, homozygosity for a variant in HMGA2 could be identified in a severely affected sibpair, whereas parents carrying heterozygous variants had a mild phenotype. Treatment with recombinant growth hormone led to a catch-up growth in 1 patient, whereas all others did not receive growth hormone and stayed small. One patient developed type 2 diabetes at age 30 years. Conclusions Identification of novel pathogenic variants confirms HMGA2 as an SRS-causing gene; thus, HMGA2 testing should be implemented in molecular SRS diagnostic workup. Furthermore, inheritance of HMGA2 is variable depending on the severity of the variant and its consequence for protein function.

Silver-Russell syndrome is a rare genetic imprinting disorder. Two molecular causes of Silver-Russell syndrome have been identified: loss of methylation on chromosome 11p15 (11p15 LOM) and maternal uniparental disomy for chromosome 7 (matUPD7). Current understanding of the cognitive and behavioral phenotypes associated with these two molecular subtypes is limited. This study aimed to address this gap in the literature. The Social Responsiveness Scale (SRS-2) was used to assess autistic traits in individuals with 11p15 LOM (n = 47) and matUPD7 (n = 32). A subset of participants with 11p15 LOM (n = 18) and matUPD7 (n = 15) completed in-person assessments: the Autism Diagnostic Observation Schedule (ADOS-2) and the British Ability Scales (BAS3). Overall, 37.50% of the matUPD7 group and 10.64% of the 11p15 LOM group scored above the SRS-2 severe clinical cut-off. Based on the ADOS-2, 33.33% of the matUPD7 participants and 11.11% of the 11p15 LOM participants scored above cut-off for autism spectrum/autism. Intellectual ability was significantly lower in the matUPD7 group (M = 79.86) compared with the 11p15 LOM group (M = 98.56). However, there was no evidence of an uneven cognitive profile associated with either group or of an association between autistic traits and intellectual ability. Although both 11p15 LOM and matUPD7 have the same clinical diagnosis of Silver-Russell syndrome, there are some differences in the cognitive and behavioral phenotypes between these two molecular subtypes. This has implications for considering access to services, intervention, and support within these populations, particularly in relation to learning and behavior. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

The overgrowth disorder Beckwith-Wiedemann syndrome and the growth restriction disorder Silver-Russell syndrome have been described as 'mirror' syndromes, in both their clinical features and molecular causes. Clinically, their nonspecific features, focused around continuous variables of atypical growth, make it hard to set diagnostic thresholds that are pragmatic without potentially excluding some cases. Molecularly, both are imprinting disorders, classically associated with 'opposite' genetic and epigenetic changes to genes on chromosome 11p15, but both are associated with somatic mosaicism as well as an increasing range of alternative (epi)genetic changes to other genes, which make molecular diagnosis an increasingly complex process. In this Current Opinion, we explore how the understanding of Beckwith-Wiedemann syndrome and Silver-Russell syndrome has evolved in recent years, stretching the canonical 'mirror' designations in different ways for the two disorders and how this is changing clinical and molecular diagnosis. We suggest some possible directions of travel toward more timely and stratified diagnosis, so that patients can access the early interventions that are so critical for good outcome.

Context Children born small-for-gestational-age with short stature (SGA-SS) is associated with (epi)genetic defects, including imprinting disorders (IDs), pathogenic copy number variants (PCNVs), and pathogenic variants of genes involved in growth. However, comprehensive studies evaluating these 3 factors are very limited. Objective To clarify the contribution of PCNVs and candidate pathogenic variants to SGA-SS. Design Comprehensive molecular analyses consisting of methylation analysis, copy number analysis, and multigene sequencing. Methods We enrolled 140 patients referred to us for genetic testing for SGA-SS. Among them, we excluded 42 patients meeting Netchine–Harbison clinical scoring system criteria for Silver–Russell syndrome and 4 patients with abnormal methylation levels of the IDs-related differentially methylated regions. Consequently, we conducted copy number analysis and multigene sequencing for 86 SGA-SS patients with sufficient sample volume. We also evaluated clinical phenotypes of patients with PCNVs or candidate pathogenic variants. Results We identified 8 (9.3%) and 11 (12.8%) patients with PCNVs and candidate pathogenic variants, respectively. According to the American College of Medical Genetics standards and guidelines, 5 variants were classified as pathogenic and the remaining 6 variants were classified as variants of unknown significance. Genetic diagnosis was made in 12 patients. All patients with PCNVs or candidate pathogenic variants did not correspond perfectly to characteristic clinical features of each specific genetic cause. Conclusion We clarified the contribution of PCNVs and pathogenic variants to SGA-SS without IDs. Comprehensive molecular analyses, including copy number analysis and multigene sequencing, should be considered for patients with unknown SGA-SS etiology.

Funder: National Institute for Health Research (NIHR), Funder: RWTH Aachen University, BACKGROUND: Imprinting disorders, which affect growth, development, metabolism and neoplasia risk, are caused by genetic or epigenetic changes to genes that are expressed from only one parental allele. Disease may result from changes in coding sequences, copy number changes, uniparental disomy or imprinting defects. Some imprinting disorders are clinically heterogeneous, some are associated with more than one imprinted locus, and some patients have alterations affecting multiple loci. Most imprinting disorders are diagnosed by stepwise analysis of gene dosage and methylation of single loci, but some laboratories assay a panel of loci associated with different imprinting disorders. We looked into the experience of several laboratories using single-locus and/or multi-locus diagnostic testing to explore how different testing strategies affect diagnostic outcomes and whether multi-locus testing has the potential to increase the diagnostic efficiency or reveal unforeseen diagnoses. RESULTS: We collected data from 11 laboratories in seven countries, involving 16,364 individuals and eight imprinting disorders. Among the 4721 individuals tested for the growth restriction disorder Silver-Russell syndrome, 731 had changes on chromosomes 7 and 11 classically associated with the disorder, but 115 had unexpected diagnoses that involved atypical molecular changes, imprinted loci on chromosomes other than 7 or 11 or multi-locus imprinting disorder. In a similar way, the molecular changes detected in Beckwith-Wiedemann syndrome and other imprinting disorders depended on the testing strategies employed by the different laboratories. CONCLUSIONS: Based on our findings, we discuss how multi-locus testing might optimise diagnosis for patients with classical and less familiar clinical imprinting disorders. Additionally, our compiled data reflect the daily life experiences of diagnostic laboratories, with a lower diagnostic yield than in clinically well-characterised cohorts, and illustrate the need for systematising clinical and molecular data.

Clin Epigenetics 14, 41 (2022). doi:10.1186/s13148-022-01259-x, Published by BioMed Central, [S.l.]

A 14-year-old girl presented to our pediatric neurology clinic with complaints of hand jerks noticed since age 6. The girl reported jerky hand movements that became more severe with time and interfered with daily tasks, particularly eating and writing. Jerks worsened with action and with sudden sound stimulus, were not voluntarily suppressed, and sometimes resulted in accidental item dropping. Responsiveness to alcohol was unknown.

Imprinting disorders (ImpDis) represent a small group of rare congenital diseases primarily affecting growth, development, and the hormonal and metabolic systems. The aim of present study was to identify the prevalence of the ImpDis in Estonia, to describe trends in the live birth prevalence of these disorders between 1998 and 2016, and to compare the results with previously published data. We retrospectively reviewed the records of all Estonian patients since 1998 with both molecularly and clinically diagnosed ImpDis. A prospective study was also conducted, in which all patients with clinical suspicion for an ImpDis were molecularly analyzed. Eighty-seven individuals with ImpDis were identified. Twenty-seven (31%) of them had Prader–Willi syndrome (PWS), 15 (17%) had Angelman syndrome (AS), 15 (17%) had Silver–Russell syndrome (SRS), 12 (14%) had Beckwith–Wiedemann syndrome (BWS), 10 (11%) had pseudo- or pseudopseudohypoparathyroidism, four had central precocious puberty, two had Temple syndrome, one had transient neonatal diabetes mellitus, and one had myoclonus-dystonia syndrome. One third of SRS and BWS cases fulfilled the diagnostic criteria for these disorders, but tested negative for genetic abnormalities. Seventy-six individuals were alive as of January 1, 2018, indicating the total prevalence of ImpDis in Estonia is 5.8/100,000 (95% CI 4.6/100,000–7.2/100,000). The minimum live birth prevalence of all ImpDis in Estonia in 2004–2016 was 1/3,462, PWS 1/13,599, AS 1/27,198, BWS 1/21,154, SRS 1/15,866, and PHP/PPHP 1/27,198. Our results are only partially consistent with previously published data. The worldwide prevalence of SRS and GNAS-gene-related ImpDis is likely underestimated and may be at least three times higher than expected.

International audience; Silver-Russell syndrome (SRS) is a rare genetic disorder (estimated incidence 1/30,000 to 100,000 live births). So far, only a few studies have focused on the cognitive profile of individuals with SRS, and these were conducted some time ago, concentrated on pediatric cohorts, and included patients who had been diagnosed using a variety of clinical diagnostic systems. There has yet to be any research on the intellectual functioning of adults with SRS. This study sought to establish the intelligence, strengths and weaknesses within intellectual profile of adults with SRS, compared with normative data. Ten individuals with 11p15 epimutation aged 18–39 years completed the Wechsler Adult Intelligence Scale-Fourth Edition. Measures of interest included participants’ intelligence (Full Scale Intelligence Quotient [FSIQ]) and four domains of cognitive functioning: verbal comprehension, perceptual reasoning, working memory and processing speed. Discrepancy scores were calculated, and descriptive statistical and linear correlations were used to investigate factors associated with IQ outcome. Clinical and medical information such as rehabilitation, and perceived difficulties in daily life were collected by interviews and questionnaires. Results showed that the mean FSIQ score was in the average range (M = 95.40, SD = 18.55) and they performed best on verbal comprehension. Frequent daily difficulties were reported by patients and/or their families: learning disabilities and low self-esteem were perceived by 60% of adults. Early intervention and multidisciplinary care from childhood to adulthood are important in SRS for care potential medical, cognitive and psychosocial problems. This is the first study to document the intellectual functioning of adults with SRS.

Background The main symptoms of congenital chloride diarrhea (CCD) main symptoms are watery diarrhea, hypochloremia, and hypokalemic metabolic alkalosis. Silver–Russell syndrome (SRS) is a heterogeneous imprinting disorder characterized by severe intrauterine retardation, poor postnatal growth, and facial dysmorphism. Methods Parent‐offspring trio whole‐exome sequencing was used to identify the causal variants. Sequencing reads were mapped to the reference of human genome version hg19. Sanger sequencing was performed as a confirmatory experiment. Results The proband was a patient with SRS caused by maternal uniparental disomy 7. The CCD of the proband was caused by homozygous variant c.1515–1 (IVS13) G>A; both mutated alleles were inherited from her mother. Conclusion We report the first clinical case of CCD and SRS occurring together. Patients with milder phenotypes may be difficult to diagnose in early stage, but close monitoring of potential complications is important for identification., We report the first case of a female child presenting with CCD accompanied by maternal segmental UPD of chromosome 7 confirmed by molecular diagnosis. The proband was the only patient in the family and harbored a SLC26A3 variant (NM_000111.3:c.1515‐1G>A). The mother of the patient was heterozygous, whereas the father was wild‐type. After treatment of CCD, the patient still failed to thrive and had a typical dysmorphic feature. In the second genetic analysis, we found that at least 86.51 Mb of genome 7q11q36 (chr7: 65446986–151960086) was maternal uniparental disomy. We revised the diagnosis to CCD combined with SRS.

Genes 12(4), 585 (2021). doi:10.3390/genes12040585 special issue: "Special Issue "Genomic Imprinting and the Regulation of Growth and Metabolism" / Special Issue Editors: Miguel Constancia, Guest Editor; Marika Charalambous, Guest Editor; Ionel Sandovici, Guest Editor; Eamonn Maher, Guest Editor", Published by MDPI, Basel

Molecular defects altering the expression of the imprinted genes of the 11p15.5 cluster are responsible for the etiology of two congenital disorders characterized by opposite growth disturbances, Silver–Russell syndrome (SRS), associated with growth restriction, and Beckwith–Wiedemann syndrome (BWS), associated with overgrowth. At the molecular level, SRS and BWS are characterized by defects of opposite sign, including loss (LoM) or gain (GoM) of methylation at the H19/IGF2:intergenic differentially methylated region (H19/IGF2:IG-DMR), maternal or paternal duplication (dup) of 11p15.5, maternal (mat) or paternal (pat) uniparental disomy (upd), and gain or loss of function mutations of CDKN1C. However, while upd(11)pat is found in 20% of BWS cases and in the majority of them it is segmental, upd(11)mat is extremely rare, being reported in only two SRS cases to date, and in both of them is extended to the whole chromosome. Here, we report on two novel cases of mosaic upd(11)mat with SRS phenotype. The upd is mosaic and isodisomic in both cases but covers the entire chromosome in one case and is restricted to 11p14.1-pter in the other case. The segmental upd(11)mat adds further to the list of molecular defects of opposite sign in SRS and BWS, making these two imprinting disorders even more specular than previously described.

Silver Russell Syndrome (SRS, MIM #180860) is a rare growth retardation disorder in which clinical diagnosis is based on six features: pre- and postnatal growth failure, relative macrocephaly, prominent forehead, body asymmetry, and feeding difficulties (Netchine–Harbison clinical scoring system (NH-CSS)). The molecular mechanisms consist in (epi)genetic deregulations at multiple loci: the loss of methylation (LOM) at the paternal H19/IGF2:IG-DMR (chr11p15.5) (50%) and the maternal uniparental disomy of chromosome 7 (UPD(7)mat) (10%) are the most frequent causes. Thus far, about 40% of SRS remains undiagnosed, pointing to the need to define the rare mechanisms in such a consistent fraction of unsolved patients. Within a cohort of 176 SRS with an NH-CSS ≥ 3, a molecular diagnosis was disclosed in about 45%. Among the remaining patients, we identified in 3 probands (1.7%) with UPD(20)mat (Mulchandani–Bhoj–Conlin syndrome, OMIM #617352), a molecular mechanism deregulating the GNAS locus and described in 21 cases, characterized by severe feeding difficulties associated with failure to thrive, preterm birth, and intrauterine/postnatal growth retardation. Our patients share prominent forehead, feeding difficulties, postnatal growth delay, and advanced maternal age. Their clinical assessment and molecular diagnostic flowchart contribute to better define the characteristics of this rare imprinting disorder and to rank UPD(20)mat as the fourth most common pathogenic molecular defect causative of SRS.

Silver-Russell syndrome (SRS) is a congenital disorder characterized by prenatal and postnatal growth failure and craniofacial features. Hypomethylation of the H19/IGF2:IG-differential methylated region (H19LOM) is observed in 50% of SRS patients, and 15% of SRS patients with H19LOM had multilocus imprinting disturbance (MLID). Schimke immuno-osseous dysplasia (SIOD), characterized by spondyloepiphyseal dysplasia and nephropathy, is an autosomal recessive disorder caused by mutations in SMARCAL1 on chromosome 2. We report a patient with typical SRS-related features, spondyloepiphyseal dysplasia, and severe nephropathy. Molecular analyses showed H19LOM, paternal uniparental isodisomy of chromosome 2 (iUPD(2)pat), and a paternally inherited homozygous frameshift variant in SMARCAL1. Genome-wide methylation analysis showed MLID in this patient, although it showed no MLID in another patient with SIOD without SRS phenotype. These results suggest that iUPD(2)pat unmasked the recessive mutation in SMARCAL1 and that the SMARCAL1 gene mutation may have no direct effect on the patient's methylation defects.

Clinical epigenetics 13, 30 (2021). doi:10.1186/s13148-021-01020-w, Published by BioMed Central, [S.l.]

Orphanet journal of rare diseases 16(1), 42 (2021). doi:10.1186/s13023-021-01683-x, Published by BioMed Central, London

Background Imprinting disorders (IDs) show overlapping phenotypes, particularly in Silver–Russell syndrome (SRS), Temple syndrome (TS14), and Prader–Willi syndrome (PWS). These three IDs include fetal and postnatal growth failure, feeding difficulty, and muscular hypotonia as major clinical features. However, the mechanism that causes overlapping phenotypes has not been clarified. To investigate the presence or absence of methylation signatures associated with overlapping phenotypes, we performed genome-wide methylation analysis (GWMA). Results GWMA was carried out on 36 patients with three IDs (SRS [n = 16], TS14 [n = 7], PWS [n = 13]) and 11 child controls using HumanMethylation450 BeadChip including 475,000 CpG sites across the human genome. To reveal an aberrantly methylated region shared by SRS, TS14, and PWS groups, we compared genome-wide methylation data of the three groups with those of control subjects. All the identified regions were known as SRS-, TS14-, and PWS-related imprinting-associated differentially methylated regions (iDMRs), and there was no hypermethylated or hypomethylated region shared by different ID groups. To examine the methylation pattern shared by SRS, TS14, and PWS groups, we performed clustering analysis based on GWMA data. The result focusing on 620 probes at the 62 known iDMRs (except for SRS-, TS14-, and PWS-related iDMRs) classified patients into two categories: (1) category A, grossly normal methylation patterns mainly consisting of SRS group patients; and (2) category B, broad and mild hypermethylation patterns mainly consisting of TS14 and PWS group patients. However, we found no obvious relationship between these methylation patterns and phenotypes of patients. Conclusions GWMA in three IDs found no methylation signatures shared by SRS, TS14, and PWS groups. Although clustering analysis showed similar mild hypermethylation patterns in TS14 and PWS groups, further study is needed to clarify the effect of methylation patterns on the overlapping phenotypes.

BackgroundSilver-Russell syndrome is an imprinting disorder that restricts growth, resulting in short adult stature that may be ameliorated by treatment. Approximately 50% of patients have loss of methylation of the imprinting control region (H19/IGF2:IG-DMR) on 11p15.5 and 5%–10% have maternal uniparental disomy of chromosome 7. Most published research focuses on the childhood phenotype. Our aim was to describe the phenotypic characteristics of older patients with SRS.MethodsA retrospective cohort of 33 individuals with a confirmed molecular diagnosis of SRS aged 13 years or above were carefully phenotyped.ResultsThe median age of the cohort was 29.6 years; 60.6% had a height SD score (SDS) ≤−2 SDS despite 70% having received growth hormone treatment. Relative macrocephaly, feeding difficulties and a facial appearance typical of children with SRS were no longer discriminatory diagnostic features. In those aged ≥18 years, impaired glucose tolerance in 25%, hypertension in 33% and hypercholesterolaemia in 52% were noted. While 9/33 accessed special education support, university degrees were completed in 40.0% (>21 years). There was no significant correlation between quality of life and height SDS. 9/25 were parents and none of the 17 offsprings had SRS.ConclusionHistorical treatment regimens for SRS were not sufficient for normal adult growth and further research to optimise treatment is justified. Clinical childhood diagnostic scoring systems are not applicable to patients presenting in adulthood and SRS diagnosis requires molecular confirmation. Metabolic ill-health warrants further investigation but SRS is compatible with a normal quality of life including normal fertility in many cases.

Clinical epigenetics 12(1), 152 (2020). doi:10.1186/s13148-020-00945-y, Published by BioMed Central, [S.I.]

Backgrounds The proportion of assisted reproductive technology (ART)-conceived livebirths of patients with imprinting disorders (IDs) is higher than that of the general population. Whether this is due to ART or confounding effects of advanced parental age was not investigated. We examined the association of ART and parental ages at childbirth for the development of eight epimutation-mediated imprinting disorders (epi-IDs). Results We enrolled 136 patients with epi-IDs and obtained general population ART data from the Japanese robust nationwide registry. We compared the proportion of ART-conceived livebirths and maternal childbearing ages between patients with epi-IDs and the general population. The proportion of ART-conceived livebirths in patients with epi-IDs was higher than that in mothers aged ≥ 30 years, the age group in which more than 90% of ART procedures performed. The maternal childbearing ages of patients with epi-IDs were widely distributed from 19 to 45 (median: 32) within the approximate 2.5th to 97.5th percentiles of maternal childbearing ages of the general population. In addition, we compared the proportion of ART-conceived livebirths and parental ages at childbirth across patients with eight epi-IDs. We demonstrated that more than 90% of ART-conceived patients with epi-IDs were found in Silver-Russell syndrome (SRS) and Beckwith-Wiedemann syndrome (BWS) patients, and parental ages were almost consistent in patients with eight epi-IDs, except Prader-Willi syndrome. Conclusions According to the prerequisite that most of the ART procedures in Japan are performed on mothers aged ≥ 30 years, ART can be a risk factor for the development of epi-IDs, particularly SRS and BWS, for mothers aged ≥ 30 years.

Background Silver‐Russell syndrome (SRS) is a heterogeneous imprinting disorder featuring severe intrauterine and postnatal growth retardation and dysmorphic features. Pendred syndrome (PDS) is an autosomal recessive disorder caused by mutations in the SLC26A4 gene characterized by sensorineural hearing loss. Methods Karyotyping analysis was performed to investigate any chromosomal abnormalities. Whole‐genome copy number variation and loss of heterozygosity were analyzed using an Affymetrix CytoScan 750 K Microarray. Variant screening was performed by targeted next‐generation sequencing on all known deafness‐causing genes. Results The proband was a patient with SRS caused by maternal uniparental disomy 7. The PDS of the proband was caused by homozygous variant c.919‐2A > G of SLC26A4; both mutated alleles were inherited from his mother. Conclusion This is the first report of uniparental disomy 7 leading to SRS and Pendred syndrome. Patients with intrauterine growth retardation or those born small for gestational age and exhibiting postnatal growth failure should undergo molecular testing to reach a clinical diagnosis.

Background Silver-Russell Syndrome (SRS) is a genetic disorder characterized by intrauterine and postnatal growth restriction and normal head circumference with consequent relative macrocephaly. Addictional findings are protruding forehead in early life, body asymmetry (of upper and lower limbs) and substantial feeding difficulties. Although several genetic mechanisms that cause the syndrome are known, more than 40% of patients with a SRS-like phenotype remain without an etiological diagnosis. In the last few years, different clinical reports have suggested that mutations or deletions of the HMGA2 gene can be responsible for a SRS-like phenotype in patients with negative results of the common diagnostic tests for this syndrome. Case presentation We present a 3-year-old male patient with clinical diagnosis of Silver-Russell Syndrome (SRS) associated with a de novo heterozygous deletion of the long arm of the chromosome 12 (12q14.3) encompassing the HMGA2 gene. Conclusions Our report confirms the etiological role of HMGA2 as a disease gene in the development of a SRS-like phenotype.

The clinical impact of duplications affecting the 11p15.5 region is difficult to predict, and depends on the parent-of-origin of the affected allele as well as on the type (deletion, duplication), the extent and genomic content of the variant. Three unrelated families with inheritance of duplications affecting the IC1 region in 11p15.5 through two generations but different phenotypes (Beckwith-Wiedemann and Silver-Russell syndromes, normal phenotype) are reported. The inconsistent phenotypic patterns of carriers of the same variant strongly indicate the impact of cis- and/or trans-acting modifiers on the clinical outcome of IC1 duplication carriers.

Background Silver-Russell syndrome (SRS) is a pre- or post-natal growth retardation disorder caused by (epi)genetic alterations. We evaluated the molecular basis and clinical value of sequential epigenetic analysis in pediatric patients with SRS. Methods Twenty-eight patients who met≥3 Netchine-Harbison clinical scoring system (NH-CSS) criteria for SRS were enrolled;26 (92.9%) were born small for gestational age, and 25 (89.3%) showed postnatal growth failure. Relative macrocephaly, body asymmetry, and feeding difficulty were noted in 18 (64.3%), 13 (46.4%), and 9 (32.1%) patients, respectively. Methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) on chromosome 11p15 was performed as the first diagnostic step. Subsequently, bisulfite pyrosequencing (BP) for imprinting center 1 and 2 (IC1 and IC2) at chromosome 11p15, MEST on chromosome 7q32.2, and MEG3 on chromosome 14q32.2 was performed. Results . Seventeen (60.7%) patients exhibited methylation defects, including loss of IC1 methylation (N=14; 11 detected by MS-MLPA and three detected by BP) and maternal uniparental disomy 7 (N=3). The diagnostic yield was comparable between patients who met three or four of the NH-CSS criteria (53.8% vs 50.0%). Patients with methylation defects responded better to growth hormone treatment. Conclusions NH-CSS is a powerful tool for SRS screening. However, in practice, genetic analysis should be considered even in patients with a low NH-CSS score. BP analysis detected additional methylation defects that were missed by MS-MLPA and might be considered as a first-line diagnostic tool for SRS.

Silver-Russell syndrome is characterized by asymmetrical intrauterine growth retardation, with normal head circumference and small, pointed chin, which results in a triangular face. It can also include body asymmetry, among other characteristics. Its global incidence is estimated at 1 in 30 000-100 000 births, even though this figure may be underestimated. In approximately 60 % of cases, a molecular cause can be identified, and the main one is hypomethylation of the paternal allele at the imprinting control region 1 located at 11p15.5-p15.4. It is necessary to make the diagnosis of this entity, exclude differential diagnoses, and know (epi)genotype-phenotype correlations in order to ensure an adequate follow-up, provide available therapeutic options, and offer a timely family genetic counseling. The objective of this article is to describe the current status of the Silver-Russell syndrome, a model of genomic imprinting disorder.El síndrome de Silver-Russell se caracteriza por retraso del crecimiento intrauterino asimétrico, con circunferencia craneal normal, barbilla pequeña y puntiaguda, que proporciona un aspecto de rostro triangular. Puede, además, presentar asimetría corporal, entre otros. Tiene una incidencia mundial estimada de 1 en 30 000- 100 000 nacimientos, aunque este número es, probablemente, subestimado. En alrededor del 60 % de los casos, se puede identificar una causa molecular y la principal es la hipometilación del alelo paterno en la región de control de impresión 1 localizado en 11p15.5-p15.4. Realizar el diagnóstico de esta entidad, excluir los diagnósticos diferenciales y conocer las correlaciones (epi)genotipo-fenotipo son necesarios para realizar el adecuado seguimiento, brindar las opciones terapéuticas disponibles y el oportuno asesoramiento genético familiar. El objetivo del presente artículo es mostrar el estado actual del síndrome de Silver-Russell, un ejemplo de trastorno de impronta genómica.

Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS) are imprinting-related disorders associated with genetic/epigenetic alterations of the 11p15.5 region, which harbours two clusters of imprinted genes (IGs). 11p15.5 IGs are regulated by the methylation status of imprinting control regions ICR1 and ICR2. 3D chromatin structure is thought to play a pivotal role in gene expression control; however, chromatin architecture models are still poorly defined in most cases, particularly for IGs. Our study aimed at elucidating 11p15.5 3D structure, via 3C and 3D FISH analyses of cell lines derived from healthy, BWS or SRS children. We found that, in healthy cells, IGF2/H19 and CDKN1C/KCNQ1OT1 domains fold in complex chromatin conformations, that facilitate the control of IGs mediated by distant enhancers. In patient-derived cell lines, we observed a profound impairment of such a chromatin architecture. Specifically, we identified a cross-talk between IGF2/H19 and CDKN1C/KCNQ1OT1 domains, consisting in in cis, monoallelic interactions, that are present in healthy cells but lost in patient cell lines: an inter-domain association that sees ICR2 move close to IGF2 on one allele, and to H19 on the other. Moreover, an intra-domain association within the CDKN1C/KCNQ1OT1 locus seems to be crucial for maintaining the 3D organization of the region.

Genomic imprinting, a phenomenon in which the two parental alleles are regulated differently, is observed in mammals, marsupials and a few other species, including seed-bearing plants. Dysregulation of genomic imprinting can cause developmental disorders such as Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS). In this Review, we discuss (1) how various (epi)genetic lesions lead to the dysregulation of clinically relevant imprinted loci, and (2) how such perturbations may contribute to the developmental defects in BWS and SRS. Given that the regulatory mechanisms of most imprinted clusters are well conserved between mice and humans, numerous mouse models of BWS and SRS have been generated. These mouse models are key to understanding how mutations at imprinted loci result in pathological phenotypes in humans, although there are some limitations. This Review focuses on how the biological findings obtained from innovative mouse models explain the clinical features of BWS and SRS., Summary: Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS) can be caused by various (epi)genetic lesions leading to the dysregulation of genomic imprinting. This Review focuses on the mouse models used to understand how such perturbations contribute to the human BWS/SRS phenotypes.

Imprinting diseases (IDs) are rare congenital disorders caused by aberrant dosages of imprinted genes. Rare IDs are comprised by a group of several distinct disorders that share a great deal of homology in terms of genetic etiologies and symptoms. Disruption of genetic or epigenetic mechanisms can cause issues with regulating the expression of imprinted genes, thus leading to disease. Genetic mutations affect the imprinted genes, duplications, deletions, and uniparental disomy (UPD) are reoccurring phenomena causing imprinting diseases. Epigenetic alterations on methylation marks in imprinting control centers (ICRs) also alters the expression patterns and the majority of patients with rare IDs carries intact but either silenced or overexpressed imprinted genes. Canonical CRISPR/Cas9 editing relying on double-stranded DNA break repair has little to offer in terms of therapeutics for rare IDs. Instead CRISPR/Cas9 can be used in a more sophisticated way by targeting the epigenome. Catalytically dead Cas9 (dCas9) tethered with effector enzymes such as DNA de- and methyltransferases and histone code editors in addition to systems such as CRISPRa and CRISPRi have been shown to have high epigenome editing efficiency in eukaryotic cells. This new era of CRISPR epigenome editors could arguably be a game-changer for curing and treating rare IDs by refined activation and silencing of disturbed imprinted gene expression. This review describes major CRISPR-based epigenome editors and points out their potential use in research and therapy of rare imprinting diseases.

The Silver–Russell syndrome (SRS) is a rare disorder characterized by heterogeneous clinical features, including growth retardation, typical facial dysmorphisms, and body asymmetry. Genetic alterations causative of SRS mostly affect imprinted genes located on chromosomes 7 or 11. Hypomethylation of the Imprinting Center 1 (IC1) of the chromosome 11p15.5 is the most common cause of SRS, while the Imprinting Center 2 (IC2) has been more rarely involved. Specifically, maternally inherited 11p15.5 deletions including the IC2 have been associated with the Beckwith–Wiedemann Syndrome (BWS), while paternal deletions with a variable spectrum of phenotypes. Here, we describe the case of a girl with a mild SRS phenotype associated with a paternally inherited 1.4 kb deletion of IC2. The father of the proband inherited the deletion from his mother and showed normal growth, while the paternal grandmother had the deletion on her paternal chromosome and exhibited short stature. Together with previous findings obtained in mouse and humans, our data support the notion that deletion of the paternal copy of IC2 can cause SRS.

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, andPLAG1mutations 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, andGNAS 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%:IGF2in two patients,CDKN1C, andPLAG1), and five pathogenic variants in causative genes for known genetic syndromes presenting with growth failure (5.4%:IGF1Rabnormality (IGF1R), SHORT syndrome (PIK3R1), Floating-Harbor syndrome (SRCAP), Pitt-Hopkins syndrome (TCF4), and Noonan syndrome (PTPN11)). Functional analysis indicated the pathogenicity of theCDKN1Cvariant. The variants we detected inCDKN1CandPLAG1were the second and third variants leading to SRS, respectively. Our patients withCDKN1CandPLAG1variants showed similar phenotypes to previously reported patients. Furthermore, our data confirmedIGF1Rabnormality, 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.