Russell-Silver syndrome

Placental Mosaicism for Autosomal Trisomies: Comprehensive Follow-up of 528 Danish Cases (1983-2021): Placental mosaicism for autosomal trisomies

BACKGROUND

Mosaicism, characterized by the presence of two or more chromosomally distinct cell lines, is detected in 2-4% of chorionic villus samples. In these cases, the aberration may be confined to the placenta or additionally present in the fetus. Fetal involvement may manifest as fetal malformations, while confined placental mosaicism poses risks such as preterm birth and low birth weight. Differentiating between true fetal mosaicism and confined placental mosaicism at the time of the chorionic villus sampling is challenging and requires follow-up by an amniocentesis and ultrasonography.

OBJECTIVES

To estimate the risk of fetal involvement or adverse pregnancy outcomes for specific chromosomes after detecting mosaicism for an autosomal trisomy in a chorionic villus sample and identify high (red), intermediate (yellow) and low (green) risk chromosomes. Further, to explore possible associations with level of mosaicism and screening parameters.

STUDY DESIGN

A retrospective descriptive study of all singleton pregnancies with mosaicism detected in chorionic villus samples from 1983-2021 identified in the Danish Cytogenetic Central Registry and the Danish Fetal Medicine Database.

RESULTS

Of 90,973 chorionic villus samples, 528 cases had mosaicism involving an autosomal trisomy and where genetic follow-up had been performed. The overall risk of fetal involvement was 13% (69/528) with extensive variations depending on which chromosome was involved (e.g., trisomy 7: 0% (0/55) or trisomy 21: 46% (19/41)). Higher levels of mosaicism in the chorionic villus sample suggested fetal involvement as mean mosaic level was 55% in true fetal mosaics vs 28% in cases confined to the placenta (p=0.0002). In cases with confined placental mosaicism (459/528), the risk of delivering small-for-gestational-age neonates was 14% (48/341). The risk of preterm birth (before 37 weeks) was 15% (51/343). The collective risk of adverse outcome was 22% (76/343) in pregnancies that continued and where information on birth weight and gestational age at birth was available. Adverse outcomes varied substantially between chromosomes. Also, multiple-of-the-median (MoM) values of pregnancy-associated plasma protein A was predictive of these issues as it was significantly lower in cases with adverse outcome compared to cases with a normal outcome (small for gestational age: 0.23 MoM vs 0.47 MoM, p<0.0001) or preterm birth: 0.25 MoM vs 0.47 MoM, p<0.0001). After the introduction of combined first trimester screening in 2004, the detection of cases with fetal involvement seemed to increase as the risk before 2004 was 9% (16/174) compared to 15% (53/354) after 2004 (risk ratio: 1.7 (95% CI: 1.0;2.8)). The risk of adverse outcome in confined placental mosaicism pregnancies increased from 16% (22/139) before 2004 to 27% (55/204) after 2004 (risk ratio 1.7 (95% CI: 1.1;2.7)) CONCLUSIONS: Introducing combined first trimester screening increased the detection of placental mosaicism with fetal involvement and confined placental mosaicism with adverse outcome. In cases of mosaicism in chorionic villus samples, the risk of fetal involvement and adverse outcomes varied considerably between chromosomes. Importantly, adverse outcomes were seen in confined placental mosaicism for many trisomies besides trisomy 16.

Multi-locus imprinting disturbance (MLID): interim joint statement for clinical and molecular diagnosis

BACKGROUND

Imprinting disorders are rare diseases resulting from altered expression of imprinted genes, which exhibit parent-of-origin-specific expression patterns regulated through differential DNA methylation. A subgroup of patients with imprinting disorders have DNA methylation changes at multiple imprinted loci, a condition referred to as multi-locus imprinting disturbance (MLID). MLID is recognised in most but not all imprinting disorders and is also found in individuals with atypical clinical features; the presence of MLID often alters the management or prognosis of the affected person. Some cases of MLID are caused by trans-acting genetic variants, frequently not in the patients but their mothers, which have counselling implications. There is currently no consensus on the definition of MLID, clinical indications prompting testing, molecular procedures and methods for epigenetic and genetic diagnosis, recommendations for laboratory reporting, considerations for counselling, and implications for prognosis and management. The purpose of this study is thus to cover this unmet need.

METHODS

A comprehensive literature search was conducted resulting in identification of more than 100 articles which formed the basis of discussions by two working groups focusing on clinical diagnosis (n = 12 members) and molecular testing (n = 19 members). Following eight months of preparations and regular online discussions, the experts from 11 countries compiled the preliminary documentation and determined the questions to be addressed during a face-to-face meeting which was held with the attendance of the experts together with four representatives of patient advocacy organisations.

RESULTS

In light of available evidence and expert consensus, we formulated 16 propositions and 8 recommendations as interim guidance for the clinical and molecular diagnosis of MLID.

CONCLUSIONS

MLID is a molecular designation, and for patients with MLID and atypical phenotypes, we propose the alternative term multi-locus imprinting syndrome. Due to the intrinsic variability of MLID, the guidelines underscore the importance of involving experts from various fields to ensure a confident approach to diagnosis, counselling, and care. The authors advocate for global, collaborative efforts in both basic and translational research to tackle numerous crucial questions that currently lack answers, and suggest reconvening within the next 3-5 years to evaluate the research advancements and update this guidance as needed.

Silver-Russell syndrome-like features in a child with recombinant chromosome 11 derived from maternal pericentric inversion

Silver-Russell syndrome (SRS) is a well-known syndrome but with heterogeneous etiologies. We present the case of a child with severe SRS-like features resulting from a complex rearrangement of chromosome 11 inherited from his mother. We studied the index case with karyotyping, MS-MLPA and molecular karyotyping. The mother was studied with karyotyping and subtelomeric FISH. We found a child with marked developmental delay and fatal outcome due to failure to thrive, carrying an 11p15 duplication and an 11q25 deletion of maternal origin. We discovered that the mother was a carrier of a pericentric inversion of chromosome 11, with a history of recurrence in other family members who had severe growth retardation and early death. To our knowledge, no similar SRS-like cases have been described in the literature. This report supports the importance of identification the causative genetic mechanism in SRS-like individuals with duplication in 11p15 region due to high risk of recurrence and to provide an appropriate genetic counseling to the family.

Novel 14q32.2 paternal deletion encompassing the whole DLK1 gene associated with Temple syndrome

BACKGROUND

Temple syndrome (TS14) is a rare imprinting disorder caused by maternal UPD14, imprinting defects or paternal microdeletions which lead to an increase in the maternal expressed genes and a silencing the paternally expressed genes in the 14q32 imprinted domain. Classical TS14 phenotypic features include pre- and postnatal short stature, small hands and feet, muscular hypotonia, motor delay, feeding difficulties, weight gain, premature puberty along and precocious puberty.

METHODS

An exon array comparative genomic hybridization was performed on a patient affected by psychomotor and language delay, muscular hypotonia, relative macrocephaly, and small hand and feet at two years old. At 6 years of age, the proband presented with precocious thelarche. Genes dosage and methylation within the 14q32 region were analyzed by MS-MLPA. Bisulfite PCR and pyrosequencing were employed to quantification methylation at the four known imprinted differentially methylated regions (DMR) within the 14q32 domain: DLK1 DMR, IG-DMR, MEG3 DMR and MEG8 DMR.

RESULTS

The patient had inherited a 69 Kb deletion, encompassing the entire DLK1 gene, on the paternal allele. Relative hypermethylation of the two maternally methylated intervals, DLK1 and MEG8 DMRs, was observed along with normal methylation level at IG-DMR and MEG3 DMR, resulting in a phenotype consistent with TS14. Additional family members with the deletion showed modest methylation changes at both the DLK1 and MEG8 DMRs consistent with parental transmission.

CONCLUSION

We describe a girl with clinical presentation suggestive of Temple syndrome resulting from a small paternal 14q32 deletion that led to DLK1 whole-gene deletion, as well as hypermethylation of the maternally methylated DLK1-DMR.

Contribution of uniparental disomy to fetal growth restriction: a whole-exome sequencing series in a prenatal setting

Fetal growth restriction (FGR), a leading cause of perinatal morbidity and mortality, is caused by fetal, maternal, and placental factors. Uniparental disomy (UPD) is a rare condition that leads to imprinting effects, low-level mosaic aneuploidies and homozygosity for pathogenic variants. In the present study, UPD events were detected in 5 women with FGR by trio exome sequencing (trio-WES) of a cohort of 150 FGR cases. Furthermore, noninvasive prenatal testing results of the 5 patients revealed a high risk of rare autosomal trisomy. Trio-WES showed no copy-number variations (CNVs) or nondisease-causing mutations associated with FGR. Among the 5 women with FGR, two showed gene imprinting, and two exhibited confined placental mosaicism (CPM) by copy number variant sequencing (CNV-seq). The present study showed that in FGR patients with UPD, the detection of imprinted genes and CPM could enhance the genetic diagnosis of FGR.

Case report: Paternal uniparental disomy on chromosome 7 and homozygous SUGCT mutation in a fetus with overweight after birth

Background: Paternal uniparental disomy (UPD) of chromosome 7 is extremely rare, and only a few postnatal cases have been reported. The effects on growth were discordant in these cases, and the relevance of paternal UPD(7) to growth caused by imprinting remains questionable. Case presentation: Here, we report a prenatal case that underwent invasive prenatal diagnosis due to the high risk of Down's syndrome and failed noninvasive prenatal screening. The fetus had a normal karyotype and no apparent copy number variation. Homozygous copy-neutral regions on chromosome 7 were identified using a single nucleotide polymorphism (SNP) array; the data for the parent-child trios showed that the fetus carried the whole paternal isodisomy of chromosome 7. Whole exome and Sanger sequencing revealed a homozygous frameshift mutation in SUGCT at 7p14.1, from the heterozygous carrier father, with no contribution from the mother. The parents decided to continue with the pregnancy after genetic counseling, and the neonate had normal physical findings at birth and showed overweight after birth during a long-term intensive follow-up. Conclusion: We report the first prenatal case who carried paternal UPD(7) and homozygous SUGCT mutation with an overweight phenotype after birth. The overweight may be caused by paternal UPD(7) or homozygous frameshift mutation of SUGCT, or both of them, but it is unclear which contributes more.

Odontoma and other congenital dental anomalies: Implications for forensic identification

Forensic odontology plays a crucial role in establishing the identity in mass disasters and criminal cases with high accuracy. Dental anomalies and features help in such situations. Congenital and developmental dental anomalies can be easily documented to establish distinctive and individualistic characteristics of an individual. The location, number of teeth involved, and the type of anomaly vary between individuals. Similarly, dental malformations also assist greatly in the identification process. Many types of dental anomalies have been studied in the past for their individualistic characteristics in forensic examinations. One such dental anomaly is odontoma, which is a benign odontogenic malformation. This malformation may also help in the identification of the deceased, when recorded and examined accurately. An odontome is a malformed teeth-like structures consisting of enamel, dentin, and pulpal tissue, formed due to the growth of completely differentiated epithelial and mesenchymal cells. If antemortem (AM) dental records incorporate information regarding odontomes and other dental anomalies, including in radiographs, orthopantomograms or microradiographs, positive identification may be established by comparison of these records with postmortem (PM) records. In the present communication, a rare case of compound composite odontoma in the anterior mandible with multiple denticles has been discussed with a brief overview of congenital and developmental dental anomalies. The authors emphasize the importance of such rare dental anomalies and malformations which may be used for identifying the deceased in mass disasters and forensic identification.

Further Introduction of DNA Methylation (DNAm) Arrays in Regular Diagnostics

Methylation tests have been used for decades in regular DNA diagnostics focusing primarily on Imprinting disorders or specific loci annotated to specific disease associated gene promotors. With the introduction of DNA methylation (DNAm) arrays such as the Illumina Infinium HumanMethylation450 Beadchip array or the Illumina Infinium Methylation EPIC Beadchip array (850 k), it has become feasible to study the epigenome in a timely and cost-effective way. This has led to new insights regarding the complexity of well-studied imprinting disorders such as the Beckwith Wiedemann syndrome, but it has also led to the introduction of tests such as EpiSign, implemented as a diagnostic test in which a single array experiment can be compared to databases with known episignatures of multiple genetic disorders, especially neurodevelopmental disorders. The successful use of such DNAm tests is rapidly expanding. More and more disorders are found to be associated with discrete episignatures which enables fast and definite diagnoses, as we have shown. The first examples of environmentally induced clinical disorders characterized by discrete aberrant DNAm are discussed underlining the broad application of DNAm testing in regular diagnostics. Here we discuss exemplary findings in our laboratory covering this broad range of applications and we discuss further use of DNAm tests in the near future.

The Methylation Status in the Chromosome 11p15.5 Region and Metabolic Disorders in Children with Syndromic and Nonsyndromic Intrauterine Growth Restriction

Loss of methylation (LoM) of the imprinting control region 1 (ICR1) in the chromosome 11p15.5 domain is detected in patients with Silver-Russell syndrome (SRS), characterized by asymmetric pre- and postnatal growth restriction, and typical craniofacial features. The patients with intrauterine growth restriction (IUGR) possess a high risk for adult metabolic problems. This study is aimed to investigate the methylation levels of the chromosome 11p15.5 region and metabolic problems in children with syndromic and nonsyndromic IUGR. Methylation analysis was performed for chromosome 11p15.5 in 49 patients (33 with suspected SRS and 16 nonsyndromic IUGR) with Netchine-Harbison clinical scoring (NHCS); uniparental disomy for chromosomes 6, 7, 14, and 20 was evaluated for those who were negative. LoM of ICR1 was detected in 14 of 33 suspected SRS patients with 3 or more criteria of NHCS, 5 had borderline LoM. Maternal uniparental disomy of the chromosomes 7 and 14 was found in 2 patients. The overall detection rate of SRS was 45.5%. While clinical findings were similar in patients with LoM and borderline LoM of ICR1, typical craniofacial findings were significantly less in the patients with normal methylation. Methylation patterns were not found to be impaired in the nonsyndromic IUGR group. Metabolic complications were evaluated in a total of 63 patients including 33 SRS-suspicious, 16 nonsyndromic IUGR, and 14 patients with 3M or SHORT syndrome. Increased rates of hypercalciuria, insulin resistance, and dyslipidemia were detected in patients with both syndromic and nonsyndromic IUGR. We would like to emphasize that detecting typical facial findings is effective in the diagnosis of SRS and paying attention to metabolic problems in the follow-up of patients with IUGR is recommended.

Epigenotype, Genotype, and Phenotype Analysis of Taiwanese Patients with Silver-Russell Syndrome

Background: Silver–Russell syndrome (SRS) is a clinically and genetically heterogeneous disorder characterized by severe intrauterine growth retardation, poor postnatal growth, characteristic facial features, and body asymmetry. Hypomethylation of the imprinted genes of the chromosome 11p15.5 imprinting gene cluster and maternal uniparental disomy of chromosome 7 (mUPD7) are the major epigenetic disturbances. The aim of this study was to characterize the epigenotype, genotype, and phenotype of these patients in Taiwan. Methods: Two hundred and six subjects with clinically suspected SRS were referred for diagnostic testing, which was performed by profiling the methylation of H19-associated imprinting center (IC) 1 and the imprinted PEG1/MEST region using methylation-specific multiplex ligation-dependent probe amplification and high-resolution melting analysis with a methylation-specific polymerase chain reaction assay. We also applied a whole genome strategy to detect copy number changes and loss of heterozygosity. Clinical manifestations were recorded and analyzed according to the SRS scoring system proposed by Bartholdi et al. Results: Among the 206 referred subjects, 100 were classified as having a clinical diagnosis of SRS (score ≥ 8, maximum = 15) and 106 had an SRS score ≤ 7. Molecular lesions were detected in 45% (45/100) of the subjects with a clinical diagnosis of SRS, compared to 5% (5/106) of those with an SRS score ≤ 7. Thirty-seven subjects had IC1 hypomethylation, ten subjects had mUPD7, and three subjects had microdeletions. Several clinical features were found to be statistically different (p < 0.05) between the “IC1 hypomethylation” and “mUPD7” groups, including relative macrocephaly at birth (89% vs. 50%), triangular shaped face (89% vs. 50%), clinodactyly of the fifth finger (68% vs. 20%), and SRS score (11.4 ± 2.2 vs. 8.3 ± 2.5). Conclusions: The SRS score was positively correlated with the molecular diagnosis rate (p < 0.001). The SRS subjects with mUPD7 seemed to have fewer typical features and lower SRS scores than those with IC1 hypomethylation. Careful clinical observation and timely molecular confirmation are important to allow for an early diagnosis and multidisciplinary management of these patients.

Clinical Application of Sequential Epigenetic Analysis for Diagnosis of Silver-Russell Syndrome

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.

Association of Assisted Reproductive Technology Treatments with Imprinting Disorders

Assisted reproductive technology (ART) is a broad field in infertility that encompasses different types of treatments. These revolutionary treatment methods aimed to aid infertile or subfertile couples. Treatment was expanded exponentially, as 1 to 3% of the births worldwide takes place with ART procedures. However, treatment is not flawless. Gametes and embryos are exposed to different chemicals and stress through treatment, which leads to disturbance in proper embryo development and results in prenatal and congenital anomalies. When compared with in-vivo development of gametes and preimplantation embryos in mice, in-vitro conditions during ART treatments have been suggested to disturb the gene expression levels, especially imprinted genes. Therefore, ART has been suggested to be associated with increased incidences of different imprinting disorders such as Beckwith–Wiedemann syndrome, Angelman syndrome, and Silver–Russell syndrome, as proved by different case reports and studies. This literature review aims to explain the association of imprinting disorders with this revolutionary treatment procedure.

Role of Imprinting Disorders in Short Children Born SGA and Silver-Russell Syndrome Spectrum

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 METHODS

To 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.

RESULTS

These 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."

CONCLUSION

We 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.

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

Objective

Uniparental 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.

Methods

A combination of clinical, molecular, and imaging data and functional studies in patient-derived fibroblasts.

Results

We 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.

Conclusions

This 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.

DNA methylation as an epigenetic biomarker in imprinting disorders

Epigenetic modifications control gene expression and enable the same genotype to lead to various phenotypes, thus exhibiting extensive variability in human cells function. DNA methylation is one of the most often investigated epigenetic modifications, playing a key part in genomic imprinting. Genomic imprinting is an epigenetic process by which the male and the female germ cells confer specific marks (imprints). Maternal chromatin marks differ from paternal ones, leading to expression of specific genes from only one allele. Disturbance in imprinting process results in epimutations, which are epigenetic defects, including DNA methylation changes. These abnormalities are identified in a group of imprinting disorders, associated with abnormal growth, development, behaviour and metabolism. Epimutations can occur spontaneously without any accompanying variant in DNA genomic sequence (a primary epimutation), whose defect can be a result of environmental factors. They can also be caused by changes in DNA sequence of genes involved in imprinting process (a secondary epimutation). DNA methylation in imprinting control regions is a very useful epigenetic biomarker and its detection is applied in the diagnostics of imprinting disorders. At present, various techniques for DNA methylation analysis are employed, which allow for investigations of one to several imprinted loci or the whole genome. DNA methylation studies are important not only in medical molecular diagnostics but are crucial in the search for therapies that would restore normal epigenetic status in patients.

ZNF597 is a maternally expressed imprinted gene in the Holstein breed

Genomic imprinting is an epigenetic phenomenon that leads to the preferential expression of genes from either the paternal or maternal allele. Imprinted genes play important roles in mammalian growth and development and a central role in placental function. ZNF597 and NAA60 are two paternally imprinted genes in the human ZNF597-NAA60 imprinted locus, both of which show biallelic expression in the mouse, but their imprinting status in cattle is still unknown. In this study, we examined the allelic expression of ZNF597 and NAA60 in adult bovine placental and somatic tissues. By comparing the mRNA-based genotypes with the genomic DNA-based genotypes, we identified monoallelic expression of ZNF597 in the placenta and in seven other tissues, including the cerebrum, heart, liver, spleen, lung, kidney, and muscle. Nevertheless, analysis revealed biallelic expression of the NAA60 gene in these tissues. Moreover, we tested the imprinting status of ZNF597 and confirmed that the maternal allele is expressed in the bovine placenta. To determine the role of DNA methylation in regulating monoallelic/imprinted expression of bovine ZNF597, the methylation status of two CpG-enriched regions in the bovine ZNF597-NAA60 locus was analyzed using the bisulfite sequencing method. Differentially methylated regions were detected on ten CpG loci in the bovine ZNF597 promoter region. In summary, the bovine ZNF597 gene is a maternally expressed gene, and its expression is regulated by DNA methylation, whereas the NAA60 gene is not imprinted in cattle.

Novel facial characteristics in congenital rubella syndrome: a study of 115 cases in a cardiac hospital of Bangladesh

OBJECTIVE

To establish novel facial characteristics unique to congenital rubella syndrome (CRS) as prediagnostic criteria to supplement disease diagnosis in patients with or without a history of maternal rubella infection.

DESIGN

An analysis of 115 CRS case series (2018-2020) based on the presence of any of the triad features.

SETTING

Outpatient department of a tertiary care referral cardiac hospital in Dhaka, Bangladesh.

PARTICIPANTS

In total, 115 participants (53.1% men) were enrolled. Participants underwent echocardiography if they presented with suspected cardiac symptoms along with deafness, cataract or microcephaly.

MAIN OUTCOME MEASURES

Age, sex and socioeconomic status of the participants; history of maternal vaccination and infection; facial characteristics unique to CRS (triangular face, prominent nose, wide forehead and a whorl on either side of the anterior hairline) named 'rubella facies' and frequency of systemic involvements in CRS.

RESULTS

The median patient age was 2 years. The income of 50.4% of the participating families was <US$1500. Further, 32 mothers (27.8%) were infected with rubella during the first trimester of pregnancy, 15 (13.0%) during the second trimester and 3 (2.6%) during the third trimester. The remainder (65.2%) recalled no history of infection during pregnancy. Rubella facies presented as a triangular-shaped face in 95 (82.6%) cases, a broad forehead in 88 (76.5%) and a prominent nose in 75 (65.2%). A rubella whorl was present on the right or left side of the anterior hairline in 80% and 18.2% of cases, respectively. IgG and IgM antibodies were present in 91.3% and 8.6% of children, respectively. Cataract, deafness, microcephaly, and congenital heart disease were detected in 53.0%, 75.6%, 68.6% and 98.2% of cases, respectively.

CONCLUSIONS

Rubella facies, a set of unique facial characteristics, can support early CRS diagnosis and treatment and may supplement the existing CRS triad.

Russell-Silver syndrome with cleft palate: a case report

BACKGROUND

Russell-Silver syndrome (RSS) is characterized by intrauterine growth retardation, short stature without postnatal catch-up growth, and an inverted triangular face with relative macrocephaly. There have been few case reports of RSS with cleft palate, in which perioperative problems such as difficult intubation due to trismus and impossibility to wear a mouth gag due to growth failure of the mandible were described. The case of a female RSS patient with cleft palate who underwent palatoplasty is reported.

CASE PRESENTATION

Although her weight was particularly low (5920 g), palatoplasty was performed under general anesthesia at 3 years and 6 months of age. Despite limited mouth opening, intubation was relatively easy. Although her mandibular alveolar width was narrow, a Dingman mouth gag could be tightly fastened around her mouth. Postoperatively, the patient was transferred to the intensive care unit without extubation due to pharyngeal edema. On the following day, since the pharyngeal edema had improved, the endotracheal tube was extubated, and her respiratory status was subsequently stable.

CONCLUSIONS

In RSS patients with cleft palate, there have been a few reports of pharyngeal edema. Thus, the risk of pharyngeal edema must be considered in such patients.

Segmental Maternal UPD of Chromosome 7q in a Patient With Pendred and Silver Russell Syndromes-Like Features

Pendred syndrome (PS) is an autosomal recessive disorder due to mutations in the SLC26A4 gene (chr7q22. 3) and characterized by sensorineural hearing loss and variable thyroid phenotype. Silver-Russell syndrome (SRS) is a heterogeneous imprinting disorder including severe intrauterine and postnatal growth retardation, and dysmorphic features. Maternal uniparental disomy of either the whole chromosome 7 (upd(7)mat) or 7q (upd(7q)mat) is one of the multiple mechanisms impacting the expression of imprinted genes in SRS, and is associated with milder clinical features. Here, we report genetic and clinical characterization of a female child with PS, postnatal growth retardation, and minor dysmorphic features. A gross homozygous deletion of SLC26A4 exons 17-20 was suspected by Sanger sequencing and then confirmed by array-CGH. Moreover, an insertion of about 1 kb of the CCDC126 gene (7p15.3), which does not appear to be clinically relevant, was detected. The possible occurrence of a balanced rearrangement between 7p and 7q was excluded. The absence of the deletion in the father led to the investigation of upd, and microsatellite segregation analysis revealed a segmental 7q (upd(7q)mat), leading to SLC26A4 homozygosity and responsible for both PS and SRS-like traits. The proband matched 3 out of 6 major SRS criteria. In conclusion, this is the first report of uniparental isodisomy encompassing almost the whole long arm of chromosome 7 resulting in PS and SRS-like features. Whereas, the inner ear phenotype of PS is typical, the clinical features suggestive of SRS might have been overlooked.

Short children born small for gestational age outcomes in the era of growth hormone therapy

Small-for-gestational age (SGA) infants are at risk for short and long term medical and metabolic complications. Most SGA infants (85-90%) demonstrate spontaneous catch-up growth, typically in the first year after birth. Although catch-up growth (CUG) is a desired goal, it is important to note if CUG is too rapid the infants are at increased risk for insulin resistance and type 2 diabetes mellitus as they become adults. On the flip side, infants who do not exhibit CUG are also at increased risk of adverse adult outcomes including those for cardiovascular disease, insulin resistance and type 2 diabetes mellitus, neurodevelopmental and cognitive impairments, in addition to adult short stature. Treatment with growth hormone is safe and effective not only in increasing adult height, but also in improving body composition and decreasing metabolic complications. The aims of this review are to summarize the current knowledge on what constitutes "healthy" catch-up growth in children born SGA as well as provide an update on the role of growth hormone treatment for short children born SGA.

Severe hypotonia and postnatal growth impairment in a girl with a missense mutation in COL1A1: Implication of expanded phenotypic spectrum of type I collagenopathy

BACKGROUND

It is known that type I collagenopathy has a broad-spectrum phenotypic variability. Here, we report a case of a Korean girl with a heterozygous COL1A1 mutation who had an atypical presentation.

CASE PRESENTATION

A 26-month-old girl presented with delayed motor development and failure to thrive. She had severe growth retardation. She exhibited right-sided plagiocephaly, blue sclerae, and facial dysmorphism, including a small pointed chin, frontal bossing, and a triangular face, but had microcephaly. Whole-exome sequencing revealed a novel de novo heterozygous sequence variant in COL1A1 (p.Gly1127Asp), which was validated by Sanger sequencing. Radiological finding showed generalized osteoporosis with progressive scoliosis of the spine without evidence of platyspondyly related to fractures and bowing of the long bones, and markedly delayed carpal bone age. Muscle pathology showed a marked size variation of myofibers and selective type 1 atrophy.

CONCLUSIONS

This study expanded the clinical and genetic spectrum of type I collagenopathy with a COL1A1 variant. Therefore, we suggest that type I collagenopathy should be considered in the patients who have some features of osteogenesis imperfecta simultaneously with atypical features such as facial dysmorphism.

Li-Fraumeni Syndrome Disease Model: A Platform to Develop Precision Cancer Therapy Targeting Oncogenic p53

Li-Fraumeni syndrome (LFS) is a rare hereditary autosomal dominant cancer disorder. Germline mutations in TP53, the gene encoding p53, are responsible for most cases of LFS. TP53 is also the most commonly mutated gene in human cancers. Because inhibition of mutant p53 is considered to be a promising therapeutic strategy to treat these diseases, LFS provides a perfect genetic model to study p53 mutation-associated malignancies as well as to screen potential compounds targeting oncogenic p53. In this review we briefly summarize the biology of LFS and current understanding of the oncogenic functions of mutant p53 in cancer development. We discuss the strengths and limitations of current LFS disease models, and touch on existing compounds targeting oncogenic p53 and in vitro clinical trials to develop new ones. Finally, we discuss how recently developed methodologies can be integrated into the LFS induced pluripotent stem cell (iPSC) platform to develop precision cancer therapy.

Genome-wide microRNA expression profiling in placentae from frozen-thawed blastocyst transfer

Background

Frozen-thawed embryo transfer (FET) is increasingly available for the improvement of the success rate of assisted reproductive technologies other than fresh embryo transfer (ET). There have been numerous findings that FET provides better obstetric and perinatal outcomes. However, the birth weight of infants conceived using FET is heavier than that of those conceived via ET. In addition, some reports have suggested that FET is associated with perinatal diseases such as placenta accreta and pregnancy-induced hypertension (PIH).

Results

In this study, we compared the microRNA (miRNA) expression profiles in term placentae derived from FET, ET, and spontaneous pregnancy (SP). We identified four miRNAs, miR-130a-3p, miR-149-5p, miR-423-5p, and miR-487b-3p, that were significantly downregulated in FET placentae compared with those from SP and ET. We found that DNA methylation of MEG3-DMR, not but IG-DMR, was associated with miRNA expression of the DLK1-DIO3 imprinted domain in the human placenta. In functional analyses, GO terms and signaling pathways related to positive regulation of gene expression, growth, development, cell migration, and type II diabetes mellitus (T2DM) were enriched.

Conclusions

This study supports the hypothesis that the process of FET may increase exposure of epigenome to external influences.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-017-0379-6) contains supplementary material, which is available to authorized users.

The methylation levels of the H19 differentially methylated region in human umbilical cords reflect newborn parameters and changes by maternal environmental factors during early pregnancy

H19 is a tumor-suppressor gene, and changes in the methylation of the H19-differential methylation region (H19-DMR) are related to human health. However, little is known about the factors that regulate the methylation levels of H19-DMR. Several recent studies have shown that maternal environmental factors during pregnancy, such as smoking, drinking, chemical exposure, and nutrient intake, can alter the methylation levels of several genes in fetal tissues. In this study, we examined the effects of maternal factors on changes in the methylation levels of H19-DMR in the human umbilical cord (UC), an extra-embryonic tissue. Participants from the Chiba study of Mother and Children's Health (C-MACH) were enrolled in this study. Genomic DNA was extracted from UC samples, and the methylation level of H19-DMR was evaluated by methylation-sensitive high resolution melting analysis. Individual maternal and paternal factors and clinical information for newborns at birth were examined using questionnaires prepared in the C-MACH study, a brief-type self-administered diet history questionnaire (BDHQ) during early pregnancy (gestational age of 12 weeks), and medical records. Univariate and multivariate logistic regression analyses indicated that reduced H19-DMR methylation (<50% methylation) in UC tissues was positively related to decreased head circumference in newborns [odds ratio (OR) =2.82; 95% confidence intervals (CI): 1.21-6.87; p=0.0183 and OR =2.51; 95% CI: 1.02-6.46; p=0.0499, respectively]. Moreover, multiple comparison test showed that H19-DMR methylation in UC tissues was significantly reduced in the low calorie group (intake of less than 1,000kcal/day; methylation level: 40.98%; 95% CI: 33.86-48.11) compared with that in the middle (1,000-1,999kcal/day; methylation level: 51.28%; 95% CI: 48.28-54.27) and high (≥2,000kcal/day; methylation level: 52.16%; 95% CI: 44.81-59.51) calorie groups (p=0.0054 and 0.047, respectively). In the subpopulations with low to moderate calorie intake (<2,000kcal/day), reduced H19-DMR methylation in UC tissues was significantly related to serum homocysteine concentration (OR =0.520; 95% CI: 0.285-0.875; p=0.019), maternal age (OR =1.22; 95% CI: 1.01-1.52; p=0.049), and serum folate levels (OR =0.917; 95% CI: 0.838-0.990; p=0.040). These data indicated that H19-DMR methylation levels in human UC tissues could be modulated by maternal factors during early pregnancy and may affect fetal and newborn growth.

Maintenance of Mest imprinted methylation in blastocyst-stage mouse embryos is less stable than other imprinted loci following superovulation or embryo culture

Assisted reproductive technologies are fertility treatments used by subfertile couples to conceive their biological child. Although generally considered safe, these pregnancies have been linked to genomic imprinting disorders, including Beckwith-Wiedemann and Silver-Russell Syndromes. Silver-Russell Syndrome is a growth disorder characterized by pre- and post-natal growth retardation. The Mest imprinted domain is one candidate region on chromosome 7 implicated in Silver-Russell Syndrome. We have previously shown that maintenance of imprinted methylation was disrupted by superovulation or embryo culture during pre-implantation mouse development. For superovulation, this disruption did not originate in oogenesis as a methylation acquisition defect. However, in comparison to other genes, Mest exhibits late methylation acquisition kinetics, possibly making Mest more vulnerable to perturbation by environmental insult. In this study, we present a comprehensive evaluation of the effects of superovulation and in vitro culture on genomic imprinting at the Mest gene. Superovulation resulted in disruption of imprinted methylation at the maternal Mest allele in blastocysts with an equal frequency of embryos having methylation errors following low or high hormone treatment. This disruption was not due to a failure of imprinted methylation acquisition at Mest in oocytes. For cultured embryos, both the Fast and Slow culture groups experienced a significant loss of maternal Mest methylation compared to in vivo-derived controls. This loss of methylation was independent of development rates in culture. These results indicate that Mest is more susceptible to imprinted methylation maintenance errors compared to other imprinted genes.

Genome-wide analysis of differential DNA methylation in Silver-Russell syndrome

Silver-Russell Syndrome (SRS) is clinically heterogeneous disorder characterized by low birth weight, postnatal growth restriction, and variable dysmorphic features. Current evidence strongly implicates imprinted genes as an important etiology of SRS. Although almost half of the patients showed DNA hypomethylation at the H19/IGF2 imprinted domain, and approximately 7%-10% of SRS patients have maternal uniparental disomy of chromosome 7 (UPD (7) mat); the rest of the SRS patients shows unknown etiology. In this study, we investigate whether there are further DNA methylation defects in SRS patients. We measured DNA methylation in seven SRS patients and five controls at more than 485,000 CpG sites using DNA methylation microarrays. We analyzed methylation changes genome-wide and identified the differentially methylated regions (DMRs) using bisulfite sequencing and digital PCR. Our analysis identifies epimutations at the previously characterized domains of H19/IGF2, providing proof of principle that our methodology can detect the changes in DNA methylation at imprinted loci. In addition, our results showed a novel SRS associated imprinted gene OSBPL5 located on chromosome 11p14 with the probe cg25963939, which is hypomethylated in 4/7 patients (P=0.023, β=-0.243). We also report DMRs in other genes including TGFβ3, HSF1, GAP43, NOTCH4 and MYH14. These DMRs were found to be associated with SRS using GO pathway analysis. In this study, we identified the probe cg25963939, located at the 5'UTR of imprinted gene OSBPL5, as a novel DMR that is associated with SRS. This finding provides new insights into the mechanism of SRS etiology and aid the further stratification of SRS patients by molecular phenotypes.

Systemic and maxillofacial characteristics of 11 Japanese children with Russell-Silver syndrome

Russell-Silver syndrome (RSS) is a congenital anomaly characterized by intrauterine and postnatal growth retardation, typical facial features, fifth-finger clinodactyly, and skeletal asymmetry. Although data on intrauterine and postnatal growth retardation have been reported, there are few reports concerning the typical maxillofacial morphology in individuals with RSS. The aim of this study was to describe the details of this systemic condition and to characterize maxillofacial morphology based on cephalograms in 11 Japanese patients (age range, 3.9-12.0 years) with RSS. All 11 individuals had intrauterine and postnatal growth retardation. In addition, most showed mandibular retrognathia and relative macrocephaly. Lateral cephalogram measurements showed that mandibular retrognathia resulted from short mandibular body length, whereas the depth of the cranial base was close to normal. Although asymmetry of hand, foot, and limb length were present in most individuals, obvious facial asymmetry was not common. Differences between left and right skeletal and dental age were not observed, indicating that children with RSS might show asymmetry because of quantitative differences in skeletal growth rather than delayed growth rate. Our findings not only provide important information about the maxillofacial characteristics of RSS, but also help to clarify the association between these characteristics and genetics, which will add to the body of information on clinical symptoms.

Two maternal duplications involving the CDKN1C gene are associated with contrasting growth phenotypes

Background

The overgrowth-associated Beckwith-Wiedemann syndrome (BWS) and the undergrowth-associated Silver-Russell syndrome (SRS) are characterized by heterogeneous molecular defects affecting a large imprinted gene cluster at chromosome 11p15.5-p15.4. While maternal and paternal duplications of the entire cluster consistently result in SRS and BWS, respectively, the phenotypes associated with smaller duplications are difficult to predict due to the complexity of imprinting regulation. Here, we describe two cases with novel inherited partial duplications of the centromeric domain on chromosome 11p15 associated with contrasting growth phenotypes.

Findings

In a male patient affected by intrauterine growth restriction and postnatal short stature, we identified an in cis maternally inherited duplication of 0.88 Mb including the CDKN1C gene that was significantly up-regulated. The duplication did not include the long non-coding RNA KCNQ1OT1 nor the imprinting control region of the centromeric domain (KCNQ1OT1:TSS-DMR or ICR2) in which methylation was normal. In the mother, also referring a growth restriction phenotype in her infancy, the duplication was de novo and present on her paternal chromosome. A different in cis maternal duplication, 1.13 Mb long and including the abovementioned duplication, was observed in a child affected by Tetralogy of Fallot but with normal growth. In this case, the rearrangement also included most of the KCNQ1OT1 gene and resulted in ICR2 loss of methylation (LOM). In this second family, the mother carried the duplication on her paternal chromosome and showed a normal growth phenotype as well.

Conclusions

We report two novel in cis microduplications encompassing part of the centromeric domain of the 11p15.5-p15.4 imprinted gene cluster and both including the growth inhibitor CDKN1C gene. Likely, as a consequence of the differential involvement of the regulatory KCNQ1OT1 RNA and ICR2, the smaller duplication is associated with growth restriction on both maternal and paternal transmissions, while the larger duplication, although it includes the smaller one, does not result in any growth anomaly.

Our study provides further insights into the phenotypes associated with imprinted gene alterations and highlights the importance of carefully evaluating the affected genes and regulatory elements for accurate genetic counselling of the 11p15 chromosomal rearrangements.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0236-z) contains supplementary material, which is available to authorized users.

Twin Legacies: Victor and Vincent McKusick / Twin Studies: Twinning Rates I; Twinning Rates II; MZ Twin Discordance for Russell–Silver Syndrome; Twins’ Language Skills / Headlines: Babies Born to Identical Twin Couples; Identity Exchange; Death of Princess Ashraf (Twin); Yahoo CEO Delivers Identical Twins

The lives of the illustrious monozygotic (MZ) twins, Victor A. and Vincent L. McKusick, are described. Victor earned the distinction as the ‘Father of Medical Genetics’, while Vincent was a legendary Chief Justice of the Maine Supreme Court. This dual biographical account is followed by two timely reports of twinning rates, a study of MZ twin discordance for Russell–Silver Syndrome (RSS) and a study of twins’ language skills. Twin stories in the news include babies born to identical twin couples, a case of switched identity, the death of Princess Ashraf (Twin) and a new mother of twins who is also Yahoo's CEO.

Regulation of Long Bone Growth in Vertebrates; It Is Time to Catch Up

The regulation of organ size is essential to human health and has fascinated biologists for centuries. Key to the growth process is the ability of most organs to integrate organ-extrinsic cues (eg, nutritional status, inflammatory processes) with organ-intrinsic information (eg, genetic programs, local signals) into a growth response that adapts to changing environmental conditions and ensures that the size of an organ is coordinated with the rest of the body. Paired organs such as the vertebrate limbs and the long bones within them are excellent models for studying this type of regulation because it is possible to manipulate one member of the pair and leave the other as an internal control. During development, growth plates at the end of each long bone produce a transient cartilage model that is progressively replaced by bone. Here, we review how proliferation and differentiation of cells within each growth plate are tightly controlled mainly by growth plate-intrinsic mechanisms that are additionally modulated by extrinsic signals. We also discuss the involvement of several signaling hubs in the integration and modulation of growth-related signals and how they could confer remarkable plasticity to the growth plate. Indeed, long bones have a significant ability for "catch-up growth" to attain normal size after a transient growth delay. We propose that the characterization of catch-up growth, in light of recent advances in physiology and cell biology, will provide long sought clues into the molecular mechanisms that underlie organ growth regulation. Importantly, catch-up growth early in life is commonly associated with metabolic disorders in adulthood, and this association is not completely understood. Further elucidation of the molecules and cellular interactions that influence organ size coordination should allow development of novel therapies for human growth disorders that are noninvasive and have minimal side effects.

Cerebral aneurysms and accelerated atherosclerosis in Russell-Silver syndrome: a new subtype? Case report

The authors describe the case of a 32-year-old woman known to have Russell-Silver syndrome who presented with repeated aneurysmal subarachnoid hemorrhage. Multiple intracranial aneurysms and advanced peripheral vascular disease were demonstrated. The authors postulate a link between these vascular features and the patient's genetic condition.

Modeling familial cancer with induced pluripotent stem cells

In vitro modeling of human disease has recently become feasible with induced pluripotent stem cell (iPSC) technology. Here, we established patient-derived iPSCs from a Li-Fraumeni syndrome (LFS) family and investigated the role of mutant p53 in the development of osteosarcoma (OS). LFS iPSC-derived osteoblasts (OBs) recapitulated OS features including defective osteoblastic differentiation as well as tumorigenic ability. Systematic analyses revealed that the expression of genes enriched in LFS-derived OBs strongly correlated with decreased time to tumor recurrence and poor patient survival. Furthermore, LFS OBs exhibited impaired upregulation of the imprinted gene H19 during osteogenesis. Restoration of H19 expression in LFS OBs facilitated osteoblastic differentiation and repressed tumorigenic potential. By integrating human imprinted gene network (IGN) into functional genomic analyses, we found that H19 mediates suppression of LFS-associated OS through the IGN component DECORIN (DCN). In summary, these findings demonstrate the feasibility of studying inherited human cancer syndromes with iPSCs.

A statistical method for single sample analysis of HumanMethylation450 array data: genome-wide methylation analysis of patients with imprinting disorders

BACKGROUND

The Illumina Infinium HumanMethylation450 BeadChip is an array-based technology for analysing DNA methylation at approximately 475,000 differentially methylated cytosines across the human genome. Hitherto, the array has been used for case-control studies, where sample numbers can be sufficient to yield statistically robust data on a genome-wide basis. We recently reported an informatic pipeline capable of yielding statistically and biologically significant results using only five cases, which expanded the use of this technology to rare disease studies. However, the clinical application of these technologies requires the ability to perform robust analysis of individual patients.

RESULTS

Here we report a novel informatic approach for methylation array analysis of single samples, using the Crawford-Howell t-test. We tested our approach on patients with ultra-rare imprinting disorders with aberrant DNA methylation at multiple locations across the genome, which was previously detected by targeted testing. However, array analysis outperformed targeted assays in three ways: it detected loci not normally analysed by targeted testing, detected methylation changes too subtle to detect by the targeted testing and reported broad and consistent methylation changes across genetic loci not captured by point testing.

CONCLUSIONS

This method has potential clinical utility for human disorders where DNA methylation change may be a biomarker of disease.

Prevalence and management of gastrointestinal manifestations in Silver-Russell syndrome

OBJECTIVES

Silver-Russell syndrome (SRS) is an imprinted disorder characterised by intrauterine growth retardation, relative macrocephaly, failure to thrive, typical facial phenotype and frequent body asymmetry. Feeding difficulties are frequently noted, but no study described evolution of gastrointestinal signs during infancy and their management in SRS. The aim of this study was to describe these abnormalities in a large cohort of children with SRS.

DESIGN

We included 75 patients (median age 24.3 months (5.1-135.2)) in the study. We retrospectively analysed nutritional status before growth hormone therapy, the frequency of gastrointestinal signs, such as gastroesophageal reflux (GER), vomiting, constipation and feeding difficulties, and nutritional management.

RESULTS

Maternal uniparental disomy for chromosome 7 was found in 10 patients and 11p15 hypomethylation in 65 patients. Malnutrition (defined as a weight/expected weight for height ratio <80%) was detected in 70% of the children. Gastrointestinal signs were found in 77%, including severe vomiting before the age of 1 year in 50% of cases, persistent vomiting from the age of 1 year in 29% of cases and constipation in 20% of cases. Severe GER was diagnosed in 55% of children by 24 h oesophageal pH-metry. Feeding difficulties were described in 65% of cases, with indications for dietary enrichment in 49%. Enteral nutrition by gastrostomy was indicated in 22% of cases.

CONCLUSIONS

Digestive signs (GER, constipation) and malnutrition are frequent in children with SRS. The systematic exploration and management of these signs are crucial to improve the nutritional status of these children before initiating growth hormone therapy.

Silver-Russell syndrome without body asymmetry in three patients with duplications of maternally derived chromosome 11p15 involving CDKN1C

We report duplications of maternally derived chromosome 11p15 involving CDKN1C encoding a negative regulator for cell proliferation in three Japanese patients (cases 1 and 2 from family A and case 3 from family B) with Silver-Russell syndrome (SRS) phenotype lacking hemihypotrophy. Chromosome analysis showed 46,XX,der(16)t(11;16)(p15.3;q24.3)mat in case 1, 46,XY,der(16)t(11;16)(p15.3;q24.3)mat in case 2 and a de novo 46,XX,der(17)t(11;17)(p15.4;q25.3) in case 3. Genomewide oligonucleotide-based array comparative genomic hybridization, microsatellite analysis, pyrosequencing-based methylation analysis and direct sequence analysis revealed the presence of maternally derived extra copies of the distal chromosome 11p involving the wild-type CDKN1C (a ~7.98 Mb region in cases 1 and 2 and a ~4.43 Mb region in case 3). The results, in conjunction with the previous findings in patients with similar duplications encompassing CDKN1C and in those with intragenic mutations of CDKN1C, imply that duplications of CDKN1C, as well as relatively mild gain-of-function mutations of CDKN1C lead to SRS subtype that usually lack hemihypotrophy.

Epimutations of the IG-DMR and the MEG3-DMR at the 14q32.2 imprinted region in two patients with Silver-Russell Syndrome-compatible phenotype

Maternal uniparental disomy 14 (UPD(14)mat) and related (epi)genetic aberrations affecting the 14q32.2 imprinted region result in a clinically recognizable condition which is recently referred to as Temple Syndrome (TS). Phenotypic features in TS include pre- and post-natal growth failure, prominent forehead, and feeding difficulties that are also found in Silver–Russell Syndrome (SRS). Thus, we examined the relevance of UPD(14)mat and related (epi)genetic aberrations to the development of SRS in 85 Japanese patients who satisfied the SRS diagnostic criteria proposed by Netchine et al and had neither epimutation of the H19-DMR nor maternal uniparental disomy 7. Pyrosequencing identified hypomethylation of the DLK1-MEG3 intergenic differentially methylated region (IG-DMR) and the MEG3-DMR in two cases. In both cases, microsatellite analysis showed biparental transmission of the homologs of chromosome 14, with no evidence for somatic mosaicism with full or segmental maternal isodisomy involving the imprinted region. FISH and array comparative genomic hybridization revealed neither deletion of the two DMRs nor discernible copy number alteration in the 14q32.2 imprinted region. Methylation patterns were apparently normal in other six disease-associated DMRs. In addition, a thorough literature review revealed a considerable degree of phenotypic overlap between SRS and TS, although body asymmetry was apparently characteristic of SRS. The results indicate the occurrence of epimutation affecting the IG-DMR and the MEG3-DMR in the two cases, and imply that UPD(14)mat and related (epi)genetic aberrations constitute a rare but important underlying factor for SRS.

Complex tissue-specific epigenotypes in Russell-Silver Syndrome associated with 11p15 ICR1 hypomethylation

Russell-Silver Syndrome (RSS) is a prenatal and postnatal growth retardation syndrome caused mainly by 11p15 ICR1 hypomethylation. Clinical presentation is heterogeneous in RSS patients with 11p15 ICR1 hypomethylation. We previously identified a subset of RSS patients with 11p15 ICR1 and multilocus hypomethylation. Here, we examine the relationships between IGF2 expression, 11p15 ICR1 methylation, and multilocus imprinting defects in various cell types from 39 RSS patients with 11p15 ICR1 hypomethylation in leukocyte DNA. 11p15 ICR1 hypomethylation was more pronounced in leukocytes than in buccal mucosa cells. Skin fibroblast IGF2 expression was correlated with the degree of ICR1 hypomethylation. Different tissue-specific multilocus methylation defects coexisted in 38% of cases, with some loci hypomethylated and others hypermethylated within the same cell type in some cases. Our new results suggest that tissue-specific epigenotypes may lead to clinical heterogeneity in RSS.

Tissue-specific insulator function at H19/Igf2 revealed by deletions at the imprinting control region

Parent-of-origin-specific expression at imprinted genes is regulated by allele-specific DNA methylation at imprinting control regions (ICRs). This mechanism of gene regulation, where one element controls allelic expression of multiple genes, is not fully understood. Furthermore, the mechanism of gene dysregulation through ICR epimutations, such as loss or gain of DNA methylation, remains a mystery. We have used genetic mouse models to dissect ICR-mediated genetic and epigenetic regulation of imprinted gene expression. The H19/insulin-like growth factor 2 (Igf2) ICR has a multifunctional role including insulation, activation and repression. Microdeletions at the human H19/IGF2 ICR (IC1) are proposed to be responsible for IC1 epimutations associated with imprinting disorders such as Beckwith-Wiedemann syndrome (BWS). Here, we have generated and characterized a mouse model that mimics BWS microdeletions to define the role of the deleted sequence in establishing and maintaining epigenetic marks and imprinted expression at the H19/IGF2 locus. These mice carry a 1.3 kb deletion at the H19/Igf2 ICR [Δ2,3] removing two of four CCCTC-binding factor (CTCF) sites and the intervening sequence, ∼75% of the ICR. Surprisingly, the Δ2,3 deletion does not perturb DNA methylation at the ICR; however, it does disrupt imprinted expression. While repressive functions of the ICR are compromised by the deletion regardless of tissue type, insulator function is only disrupted in tissues of mesodermal origin where a significant amount of CTCF is poly(ADP-ribosyl)ated. These findings suggest that insulator activity of the H19/Igf2 ICR varies by cell type and may depend on cell-specific enhancers as well as posttranslational modifications of the insulator protein CTCF.

[Clinical profile of a cohort of Silver-Russell syndrome patients followed at the Hospital Infantil de México Federico Gómez from 1998 to 2012]

BACKGROUND

Patients with Silver-Russell syndrome suffer from severe intrauterine and postnatal growth retardation, relative macrocephaly and body asymmetry, among other characteristics. It is caused by several genetic and epigenetic mechanisms in 11p15.5 in 40% of the cases and maternal uniparental disomy of chromosome 7 in 10%.

METHODS

Twenty patients with a diagnosis of Silver-Russell syndrome who were seen at the HIMFG from 1998 to 2012, were evaluated according to international clinical criteria confirming the diagnosis in nine of the subjects.

RESULTS

All patients showed intrauterine and postnatal growth retardation and short stature, both considered as major criteria of Silver-Russell syndrome. Relative macrocephaly was present in 78% of the patients and asymmetry in 33%. Other characteristics such as renal tubular acidosis were present > 50% of the cases.

CONCLUSIONS

The clinical diagnosis of Silver-Russell syndrome is complex. Short stature is the main reason for seeking medical attention and is helpful in the identification of a differential diagnosis. This situation underlines the importance of growth and development evaluation of all patients and particularly in those with short stature to identify those cases that may require molecular studies, with implications in management, prognosis and genetic counseling.

Molecular Karyotyping of a Dysmorphic Girl from Saudi Arabia with CYP1B1-negative Primary Congenital Glaucoma

PURPOSE

To report the results of molecular karyotyping for a dysmorphic girl with CYP1B1-negative primary congenital glaucoma from Saudi Arabia, where CYPB1 mutations account for over 90% of cases of primary congenital glaucoma and the remaining cases are idiopathic.

METHODS

CYP1B1 sequencing in the affected child; high-resolution array comparative genomic hybridization (array CGH) of the affected child and both unaffected parents (Affymetrix Cytogenetics Whole-Genome 2.7M array; Affymetrix Inc., Santa Clara, CA, USA).

RESULTS

The girl did not harbor CYP1B1 mutation by Sanger sequencing. Array CGH revealed 2 de novo 7p heterozygous duplications (7p21 - 7p14, encompassing 223 genes, and 7p14-7p11.2, encompassing 225 genes) and a 4p homozygous microdeletion (4p14) encompassing one gene only, DTHD1.

CONCLUSIONS

The fact that this dysmorphic girl is Saudi Arabian and has CYP1B1-negative primary congenital glaucoma suggests that her glaucoma phenotype is related to her de novo copy number variation. Loss or gain of one or more of the genes encompassed in the identified chromosomal areas may be associated with primary congenital glaucoma and/or other observed phenotypic features.

Identifying biological pathways that underlie primordial short stature using network analysis

Mutations in CUL7, OBSL1 and CCDC8, leading to disordered ubiquitination, cause one of the commonest primordial growth disorders, 3-M syndrome. This condition is associated with i) abnormal p53 function, ii) GH and/or IGF1 resistance, which may relate to failure to recycle signalling molecules, and iii) cellular IGF2 deficiency. However the exact molecular mechanisms that may link these abnormalities generating growth restriction remain undefined. In this study, we have used immunoprecipitation/mass spectrometry and transcriptomic studies to generate a 3-M 'interactome', to define key cellular pathways and biological functions associated with growth failure seen in 3-M. We identified 189 proteins which interacted with CUL7, OBSL1 and CCDC8, from which a network including 176 of these proteins was generated. To strengthen the association to 3-M syndrome, these proteins were compared with an inferred network generated from the genes that were differentially expressed in 3-M fibroblasts compared with controls. This resulted in a final 3-M network of 131 proteins, with the most significant biological pathway within the network being mRNA splicing/processing. We have shown using an exogenous insulin receptor (INSR) minigene system that alternative splicing of exon 11 is significantly changed in HEK293 cells with altered expression of CUL7, OBSL1 and CCDC8 and in 3-M fibroblasts. The net result is a reduction in the expression of the mitogenic INSR isoform in 3-M syndrome. From these preliminary data, we hypothesise that disordered ubiquitination could result in aberrant mRNA splicing in 3-M; however, further investigation is required to determine whether this contributes to growth failure.

Genome-wide DNA methylation analysis of patients with imprinting disorders identifies differentially methylated regions associated with novel candidate imprinted genes

BACKGROUND

Genomic imprinting is allelic restriction of gene expression potential depending on parent of origin, maintained by epigenetic mechanisms including parent of origin-specific DNA methylation. Among approximately 70 known imprinted genes are some causing disorders affecting growth, metabolism and cancer predisposition. Some imprinting disorder patients have hypomethylation of several imprinted loci (HIL) throughout the genome and may have atypically severe clinical features. Here we used array analysis in HIL patients to define patterns of aberrant methylation throughout the genome.

DESIGN

We developed a novel informatic pipeline capable of small sample number analysis, and profiled 10 HIL patients with two clinical presentations (Beckwith-Wiedemann syndrome and neonatal diabetes) using the Illumina Infinium Human Methylation450 BeadChip array to identify candidate imprinted regions. We used robust statistical criteria to quantify DNA methylation.

RESULTS

We detected hypomethylation at known imprinted loci, and 25 further candidate imprinted regions (nine shared between patient groups) including one in the Down syndrome critical region (WRB) and another previously associated with bipolar disorder (PPIEL). Targeted analysis of three candidate regions (NHP2L1, WRB and PPIEL) showed allelic expression, methylation patterns consistent with allelic maternal methylation and frequent hypomethylation among an additional cohort of HIL patients, including six with Silver-Russell syndrome presentations and one with pseudohypoparathyroidism 1B.

CONCLUSIONS

This study identified novel candidate imprinted genes, revealed remarkable epigenetic convergence among clinically divergent patients, and highlights the potential of epigenomic profiling to expand our understanding of the normal methylome and its disruption in human disease.

Genome-wide parent-of-origin DNA methylation analysis reveals the intricacies of human imprinting and suggests a germline methylation-independent mechanism of establishment

Differential methylation between the two alleles of a gene has been observed in imprinted regions, where the methylation of one allele occurs on a parent-of-origin basis, the inactive X-chromosome in females, and at those loci whose methylation is driven by genetic variants. We have extensively characterized imprinted methylation in a substantial range of normal human tissues, reciprocal genome-wide uniparental disomies, and hydatidiform moles, using a combination of whole-genome bisulfite sequencing and high-density methylation microarrays. This approach allowed us to define methylation profiles at known imprinted domains at base-pair resolution, as well as to identify 21 novel loci harboring parent-of-origin methylation, 15 of which are restricted to the placenta. We observe that the extent of imprinted differentially methylated regions (DMRs) is extremely similar between tissues, with the exception of the placenta. This extra-embryonic tissue often adopts a different methylation profile compared to somatic tissues. Further, we profiled all imprinted DMRs in sperm and embryonic stem cells derived from parthenogenetically activated oocytes, individual blastomeres, and blastocysts, in order to identify primary DMRs and reveal the extent of reprogramming during preimplantation development. Intriguingly, we find that in contrast to ubiquitous imprints, the majority of placenta-specific imprinted DMRs are unmethylated in sperm and all human embryonic stem cells. Therefore, placental-specific imprinting provides evidence for an inheritable epigenetic state that is independent of DNA methylation and the existence of a novel imprinting mechanism at these loci.