Chromosomal rearrangements in patients with clinical features of Silver-Russell syndrome

Clinical characterization of PLAG1- related Silver-Russell syndrome：A clinical report

BACKGROUND

Silver-Russell syndrome (SRS) is a rare genetic disorder that is mainly associated with prenatal and postnatal growth retardation. Loss of methylation on chromosome 11p15 and maternal uniparental disomy on chromosome 7 (upd(7)mat) are two common causes, accounting for approximately 50% and 10% of all patients, respectively. Pathogenic variants of genes, such as HMGA2, IGF2, CDKN1C, and PLAG1, have also been detected in patients with SRS. So far, SRS caused by PLAG1 alterations have only been described in two sporadic cases and three families.

PATIENT PRESENTATION

The genetic and clinical manifestations of SRS in a patient carrying a novel variant of PLAG1 were reported and these results were compared with those of five previously reported cases. Trio-based whole-exome sequencing revealed a heterozygous variation in PLAG1 (NM_002655.3: c.131del; p.(Asn44Thrfs*6)) in an infant girl with clinical suspicion of SRS. Familial studies confirmed that the mutation was inherited from her father. As seen in previously reported cases, the patient presented with prenatal and postnatal growth retardation, relative macrocephaly at birth, prominent forehead during infancy, and triangular face. However, no clinical characteristics such as feeding difficulties, hypothyroidism, or psychomotor and speech delay.

CONCLUSIONS

This study identified the sixth documented case of PLAG1 variants leading to SRS and expanded our knowledge of the molecular spectrum of SRS phenotypes.

Maternal UPD of chromosome 7 in a patient with Silver-Russell syndrome and Pendred syndrome

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.

Cri-du-chat syndrome mimics Silver-Russell syndrome depending on the size of the deletion: a case report

BACKGROUND

Silver-Russell Syndrome (SRS) is a rare growth-related genetic disorder mainly characterized by prenatal and postnatal growth failure. Although molecular causes are not clear in all cases, the most common mechanisms involved in SRS are loss of methylation on chromosome 11p15 (≈50%) and maternal uniparental disomy for chromosome 7 (upd(7)mat) (≈10%).

CASE PRESENTATION

We present a girl with clinical suspicion of SRS (intrauterine and postnatal growth retardation, prominent forehead, triangular face, mild psychomotor delay, transient neonatal hypoglycemia, mild hypotonia and single umbilical artery). Methylation and copy number variations at chromosomes 11 and 7 were studied by methylation-specific multiplex ligation-dependent probe amplification and as no alterations were found, molecular karyotyping was performed. A deletion at 5p15.33p15.2 was identified (arr[GRCh37] 5p15.33p15.2(25942-11644643)× 1), similar to those found in patients with Cri-du-chat Syndrome (CdCS). CdCS is a genetic disease resulting from a deletion of variable size occurring on the short arm of chromosome 5 (5p-), whose main feature is a high-pitched mewing cry in infancy, accompanied by multiple congenital anomalies, intellectual disability, microcephaly and facial dysmorphism.

CONCLUSIONS

The absence of some CdCS features in the current patient could be due to the fact that in her case the critical regions responsible do not lie within the identified deletion. In fact, a literature review revealed a high degree of concordance between the clinical manifestations of the two syndromes.

Effect of Cyproheptadine on Weight and Growth Velocity in Children With Silver-Russell Syndrome

OBJECTIVES

Nutritional management of children with Silver-Russell syndrome (SRS) is crucial, especially before initiating growth hormone therapy. Since cyproheptadine (CYP) has been reported to be orexigenic, we retrospectively investigated the effects of CYP on changes in weight and height in patients with SRS.

METHODS

Anthropometric parameters (weight [W], length or height [H], weight on expected weight for height [W/H], and body mass index) were recorded for 34 children with SRS receiving CYP. We specifically analyzed the anthropometric parameters (expressed in median) in a group of 23 patients treated with CYP at baseline (M0-CYP) and every 3 months (M3 to M12-CYP) after the initiation of CYP treatment.

RESULTS

The 23 children with SRS treated by CYP only had weight stagnation during the months preceding the start of treatment. Anthropometric parameters, especially the weight, differed significantly between M0-CYP and all other times (M3, M6, M9, M12-CYP). After 1 year of treatment, a gain in overall length/height and weight was observed (W: +1.1 standard deviations from the mean [SDS]; H: +0.5 SDS). At M3, significant improvements in W/H (74.9% vs 79.3% [P = 0.01]) and body mass index (-3.4 vs -2.4 SDS [P = 0.001]) were also observed. Twenty-one patients (91%) improved their weight by at least +0.5 SDS, and 12 (52%) by at least +1 SDS.

CONCLUSIONS

Our results show that CYP can be effective in patients with SRS with significant improvements in growth velocity and nutritional status before initiation of growth hormone therapy. Further prospective studies are required to confirm these results.

Structural and sequence variants in patients with Silver-Russell syndrome or similar features-Curation of a disease database

Silver-Russell syndrome (SRS) is a clinically and molecularly heterogeneous disorder involving prenatal and postnatal growth retardation, and the term SRS-like is broadly used to describe individuals with clinical features resembling SRS. The main molecular subgroups are loss of methylation of the distal imprinting control region (H19/IGF2:IG-DMR) on 11p15.5 (50%) and maternal uniparental disomy of chromosome 7 (5%-10%). Through a comprehensive literature search, we identified 91 patients/families with various structural and small sequence variants, which were suggested as additional molecular defects leading to SRS/SRS-like phenotypes. However, the molecular and phenotypic data of these patients were not standardized and therefore not comparable, rendering difficulties in phenotype-genotype comparisons. To overcome this challenge, we curated a disease database including (epi)genetic phenotypic data of these patients. The clinical features are scored according to the Netchine-Harbison clinical scoring system (NH-CSS), which has recently been accepted as standard by consensus. The structural and sequence variations are reviewed and where necessary redescribed according to recent recommendations. Our study provides a framework for both research and diagnostic purposes through facilitating a standardized comparison of (epi)genotypes with phenotypes of patients with structural/sequence variants.

Genetic disruption of the oncogenic HMGA2-PLAG1-IGF2 pathway causes fetal growth restriction

Purpose

Fetal growth is a complex process involving maternal, placental and fetal factors. The etiology of fetal growth retardation remains unknown in many cases. The aim of this study is to identify novel human mutations and genes related to Silver–Russell syndrome (SRS), a syndromic form of fetal growth retardation, usually caused by epigenetic downregulation of the potent fetal growth factor IGF2.

Methods

Whole-exome sequencing was carried out on members of an SRS familial case. The candidate gene from the familial case and two other genes were screened by targeted high-throughput sequencing in a large cohort of suspected SRS patients. Functional experiments were then used to link these genes into a regulatory pathway.

Results

We report the first mutations of the PLAG1 gene in humans, as well as new mutations in HMGA2 and IGF2 in six sporadic and/or familial cases of SRS. We demonstrate that HMGA2 regulates IGF2 expression through PLAG1 and in a PLAG1-independent manner.

Conclusion

Genetic defects of the HMGA2–PLAG1–IGF2 pathway can lead to fetal and postnatal growth restriction, highlighting the role of this oncogenic pathway in the fine regulation of physiological fetal/postnatal growth. This work defines new genetic causes of SRS, important for genetic counseling.

Maternally derived 15q11.2-q13.1 duplication and H19-DMR hypomethylation in a patient with Silver-Russell syndrome

Silver-Russell syndrome (SRS) is a congenital developmental disorder characterized by intrauterine and postnatal growth failure, craniofacial features (including a triangular shaped face and broad forehead), relative macrocephaly, protruding forehead, body asymmetry and feeding difficulties. Hypomethylation of the H19 differentially methylated region (DMR) on chromosome 11p15.5 is the most common cause of the SRS phenotype. We report the first SRS patient with hypomethylation of the H19-DMR and maternally derived 15q11.2-q13.1 duplication. Although her clinical manifestations overlapped with those of previously reported SRS cases, the patient's intellectual disability and facial dysmorphic features were inconsistent with the SRS phenotype. Methylation analyses, array comparative genomic hybridization, and a FISH analysis revealed the hypomethylation of the H19-DMR and a maternally derived interstitial 5.7 Mb duplication at 15q11.2-q13.1 encompassing the Prader-Willi/Angelman critical region in the patient. On the basis of the genetic and clinical findings in the present and previously reported cases, it is unlikely that the 15q duplication in the patient led to the development of hypomethylation of the H19-DMR and it is reasonable to consider that the characteristic phenotype in the patient was caused by the coexistence of the two (epi)genetic conditions. Further studies are needed to clarify the mechanisms leading to methylation aberrations in SRS.

Diagnosis and management of Silver-Russell syndrome: first international consensus statement

This Consensus Statement summarizes recommendations for clinical diagnosis, investigation and management of patients with Silver-Russell syndrome (SRS), an imprinting disorder that causes prenatal and postnatal growth retardation. Considerable overlap exists between the care of individuals born small for gestational age and those with SRS. However, many specific management issues exist and evidence from controlled trials remains limited. SRS is primarily a clinical diagnosis; however, molecular testing enables confirmation of the clinical diagnosis and defines the subtype. A 'normal' result from a molecular test does not exclude the diagnosis of SRS. The management of children with SRS requires an experienced, multidisciplinary approach. Specific issues include growth failure, severe feeding difficulties, gastrointestinal problems, hypoglycaemia, body asymmetry, scoliosis, motor and speech delay and psychosocial challenges. An early emphasis on adequate nutritional status is important, with awareness that rapid postnatal weight gain might lead to subsequent increased risk of metabolic disorders. The benefits of treating patients with SRS with growth hormone include improved body composition, motor development and appetite, reduced risk of hypoglycaemia and increased height. Clinicians should be aware of possible premature adrenarche, fairly early and rapid central puberty and insulin resistance. Treatment with gonadotropin-releasing hormone analogues can delay progression of central puberty and preserve adult height potential. Long-term follow up is essential to determine the natural history and optimal management in adulthood.

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

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

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

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

New developments in Silver-Russell syndrome and implications for clinical practice

Silver-Russell syndrome is a clinically and genetically heterogeneous disorder, characterized by prenatal and postnatal growth restriction, relative macrocephaly, body asymmetry and characteristic facial features. It is one of the imprinting disorders, which results as a consequence of aberrant imprinted gene expressions. Currently, maternal uniparental disomy of chromosome 7 accounts for approximately 10% of Silver-Russell syndrome cases, while ~50% of patients have hypomethylation at imprinting control region 1 at chromosome 11p15.5 locus, leaving ~40% of cases with unknown etiologies. This review aims to provide a comprehensive list of molecular defects in Silver-Russell syndrome reported to date and to highlight the importance of multiple-loci/tissue testing and trio (both parents and proband) screening. The epigenetic and phenotypic overlaps with other imprinting disorders will also be discussed.

Familial 1.3-Mb 11p15.5p15.4 Duplication in Three Generations Causing Silver-Russell and Beckwith-Wiedemann Syndromes

Silver-Russell syndrome (SRS) and Beckwith-Wiedemann syndrome (BWS) are 2 opposite growth-affecting disorders. The common molecular cause for both syndromes is an abnormal regulation of genes in chromosomal region 11p15, where 2 imprinting control regions (ICR) control fetal and postnatal growth. Also, many submicroscopic chromosomal disturbances like duplications in 11p15 have been described among SRS and BWS patients. Duplications involving both ICRs cause SRS or BWS, depending on which parent the aberration is inherited from. We describe to our knowledge the smallest familial pure 1.3-Mb duplication in chromosomal region 11p15.5p15.4 that involves both ICRs and is present in 3 generations causing an SRS or BWS phenotype.

12q14 Microdeletions: Additional Case Series with Confirmation of a Macrocephaly Region

To date, there have been only a few reports of patients carrying a microdeletion in chromosome 12q14. These patients usually present with pre- and postnatal growth retardation, and developmental delay. Here we report on two additional patients with both genotype and phenotype differences. Similar to previously published cases, one patient has haploinsufficiency of the HMGA2 gene and shows severe short stature and developmental delay. The second patient is only one of a handful without the loss of the HMGA2 gene and shows a much better growth profile, but with absolute macrocephaly. This patient's deletion is unique and hence defines a likely macrocephaly locus that contributes to the general phenotype characterising the 12q14 syndrome.

A prospective study validating a clinical scoring system and demonstrating phenotypical-genotypical correlations in Silver-Russell syndrome

Background

Multiple clinical scoring systems have been proposed for Silver-Russell syndrome (SRS). Here we aimed to test a clinical scoring system for SRS and to analyse the correlation between (epi)genotype and phenotype.

Subjects and methods

Sixty-nine patients were examined by two physicians. Clinical scores were generated for all patients, with a new, six-item scoring system: (1) small for gestational age, birth length and/or weight ≤−2SDS, (2) postnatal growth retardation (height ≤−2SDS), (3) relative macrocephaly at birth, (4) body asymmetry, (5) feeding difficulties and/or body mass index (BMI) ≤−2SDS in toddlers; (6) protruding forehead at the age of 1–3 years. Subjects were considered to have likely SRS if they met at least four of these six criteria. Molecular investigations were performed blind to the clinical data.

Results

The 69 patients were classified into two groups (Likely-SRS (n=60), Unlikely-SRS (n=9)). Forty-six Likely-SRS patients (76.7%) displayed either 11p15 ICR1 hypomethylation (n=35; 58.3%) or maternal UPD of chromosome 7 (mUPD7) (n=11; 18.3%). Eight Unlikely-SRS patients had neither ICR1 hypomethylation nor mUPD7, whereas one patient had mUPD7. The clinical score and molecular results yielded four groups that differed significantly overall and for individual scoring system factors. Further molecular screening led identifying chromosomal abnormalities in Likely-SRS-double-negative and Unlikely-SRS groups. Four Likely-SRS-double negative patients carried a DLK1/GTL2 IG-DMR hypomethylation, a mUPD16; a mUPD20 and a de novo 1q21 microdeletion.

Conclusions

This new scoring system is very sensitive (98%) for the detection of patients with SRS with demonstrated molecular abnormalities. Given its clinical and molecular heterogeneity, SRS could be considered as a spectrum.