The epsilon-sarcoglycan gene (SGCE), mutated in myoclonus-dystonia syndrome, is maternally imprinted

The landscape of allelic expression and DNA methylation at the bovine SGCE/PEG10 locus

Genomic imprinting is an epigenetic regulation in mammals in which a small subset of genes is monoallelically expressed dependent on their parental origin. A large imprinted domain, SGCE/PEG10 locus, is located on human chromosome 7q21s and mouse proximal chromosome 6. However, genomic imprinting of bovine SGCE/PEG10 cluster has not been systematically studied. In this study, we investigated allele expression of 14 genes of the SGCE/PEG10 locus in bovine somatic tissues and term placenta using a single nucleotide polymorphism (SNP)-based sequencing method. In addition to SGCE and PEG10, two conserved paternally expressed genes in human and mice, five other genes (TFPI2, GNG11, ASB4, PON1, and PON3) were paternally expressed. Three genes, BET1, COL1A2, and CASD1, exhibited tissue-specific monoallelic expression. CALCR showed monoallelic expression in tissues but biallelic expression in the placenta. Three genes, GNGT1, PPP1R9A, and PON2, showed biallelic expression in cattle. Five differentially methylated regions (DMRs) were found to be associated with the allelic expression of TFPI2, COL1A2, SGCE/PEG10, PON3, and ASB4 genes, respectively. The SGCE/PEG10 DMR is a maternally hypermethylated germline DMR, but TFPI2, COL1A2, PON3, and ASB4 DMRs are secondary DMRs. In summary, we identified five novel bovine imprinted genes (GNG11, BET1, COL1A2, CASD1, and PON1) and four secondary DMRs at the SGCE/PEG10 locus.

Novel SGCE Mutation in a Patient With Myoclonus-Dystonia: A Case Report

Objectives

Characterize the presentation, workup, and management of SGCE myoclonus-dystonia, a rare genetic condition, in a patient with atypical presenting symptoms and no family history of movement abnormalities.

Methods

A woman with myoclonus and dystonia was identified based on clinical history and physical examination. Workup was conducted to determine the cause of her symptoms, including whole-exome sequencing. Myoclonus-dystonia is associated with more than 100 distinct mutations in MYC/DYT-SGCE that account for only half of the total myoclonus-dystonia patients. As such, this case required intensive genetic analyses rather than screening only for a small subset of well-characterized mutations.

Results

Childhood onset myoclonus and worsening dystonia with age were identified in a young woman. She underwent screening for common causes of twitching movements, followed by whole-exome sequencing which identified a de novo novel variant in the SGCE gene, resulting in a diagnosis of SGCE myoclonus-dystonia.

Discussion

Myoclonus-dystonia should be considered in patients with symptoms of head and upper extremity myoclonus early in life, especially with co-occurring dystonia, even in the absence of a family history of similar symptoms. Diagnosis of this condition should take place using sequencing, as new mutations continue to be discovered.

Osteogenesis Imperfecta and Split Foot Malformation due to 7q21.2q21.3 Deletion Including COL1A2, DLX5/6 Genes: Review of the Literature

Copy number variation in loss of 7q21 is a genetic disorder characterized by split hand/foot malformation, hearing loss, developmental delay, myoclonus, dystonia, joint laxity, and psychiatric disorders. Osteogenesis imperfecta caused by whole gene deletions of COL1A2 is a very rare condition. We report a Turkish girl with ectrodactyly, joint laxity, multiple bone fractures, blue sclera, early teeth decay, mild learning disability, and depression. A copy number variant in loss of 4.8 Mb at chromosome 7 (q21.2q21.3) included the 58 genes including DLX5, DLX6, DYNC1I1, SLC25A13, SGCE, and COL1A2 . They were identified by chromosomal microarray analysis. We compared the findings in our patients with those previously reported. This case report highlights the importance of using microarray to identify the genetic etiology in patients with ectrodactyly and osteogenesis imperfecta.

Imprinting at the KBTBD6 locus involves species-specific maternal methylation and monoallelic expression in livestock animals

BACKGROUND

The primary differentially methylated regions (DMRs) which are maternally hypermethylated serve as imprinting control regions (ICRs) that drive monoallelic gene expression, and these ICRs have been investigated due to their implications in mammalian development. Although a subset of genes has been identified as imprinted, in-depth comparative approach needs to be developed for identification of species-specific imprinted genes. Here, we examined DNA methylation status and allelic expression at the KBTBD6 locus across species and tissues and explored potential mechanisms of imprinting.

RESULTS

Using whole-genome bisulfite sequencing and RNA-sequencing on parthenogenetic and normal porcine embryos, we identified a maternally hypermethylated DMR between the embryos at the KBTBD6 promoter CpG island and paternal monoallelic expression of KBTBD6. Also, in analyzed domesticated mammals but not in humans, non-human primates and mice, the KBTBD6 promoter CpG islands were methylated in oocytes and/or allelically methylated in tissues, and monoallelic KBTBD6 expression was observed, indicating livestock-specific imprinting. Further analysis revealed that these CpG islands were embedded within transcripts in porcine and bovine oocytes which coexisted with an active transcription mark and DNA methylation, implying the presence of transcription-dependent imprinting.

CONCLUSIONS

In this study, our comparative approach revealed an imprinted expression of the KBTBD6 gene in domesticated mammals, but not in humans, non-human primates, and mice which implicates species-specific evolution of genomic imprinting.

Two-Generation Epsilon-Sarcoglycan Gene (SGCE) Mutation-Associated Myoclonus-Dystonia (DYT-SGCE) Misdiagnosed as Tourette's Syndrome: A Case Series

This case series provides a diagnosis of myoclonus-dystonia syndrome (MDS) in two patients whose original presentation was thought to be Tourette's syndrome. The first patient presented with dystonia and myoclonus, which progressively worsened with age, and was diagnosed with an epsilon-sarcoglycan gene (SGCE) mutation. The patient's father, who was diagnosed in his childhood with Tourette's syndrome, also received genetic testing, which proved that to be a misdiagnosis and confirmed that he was the carrier of the SGCE mutation. Both patients were subjected to a levodopa trial, which proved to be an effective treatment. To our knowledge, these are the first reported cases of heterozygous pathogenic mutation of SGCE in Puerto Rico.

Translating Genetic Discovery into a Mechanistic Understanding of Pediatric Movement Disorders: Lessons from Genetic Dystonias and Related Disorders

The era of next-generation sequencing has increased the pace of gene discovery in the field of pediatric movement disorders. Following the identification of novel disease-causing genes, several studies have aimed to link the molecular and clinical aspects of these disorders. This perspective presents the developing stories of several childhood-onset movement disorders, including paroxysmal kinesigenic dyskinesia, myoclonus-dystonia syndrome, and other monogenic dystonias. These stories illustrate how gene discovery helps focus the research efforts of scientists trying to understand the mechanisms of disease. The genetic diagnosis of these clinical syndromes also helps clarify the associated phenotypic spectra and aids the search for additional disease-causing genes. Collectively, the findings of previous studies have led to increased recognition of the role of the cerebellum in the physiology and pathophysiology of motor control-a common theme in many pediatric movement disorders. To fully exploit the genetic information garnered in the clinical and research arenas, it is crucial that corresponding multi-omics analyses and functional studies also be performed at scale. Hopefully, these integrated efforts will provide us with a more comprehensive understanding of the genetic and neurobiological bases of movement disorders in childhood.

Mechanisms underlying phenotypic variation in neurogenetic disorders

Neurological diseases associated with pathogenic variants in a specific gene, or even with a specific pathogenic variant, can show profound phenotypic variation with regard to symptom presentation, age at onset and disease course. Highlighting examples from a range of neurogenetic disorders, this Review explores emerging mechanisms that are involved in this variability, including environmental, genetic and epigenetic factors that influence the expressivity and penetrance of pathogenic variants. Environmental factors, some of which can potentially be modified to prevent disease, include trauma, stress and metabolic changes. Dynamic patterns of pathogenic variants might explain some of the phenotypic variations, for example, in the case of disorders caused by DNA repeat expansions such as Huntington disease (HD). An important role for modifier genes has also been identified in some neurogenetic disorders, including HD, spinocerebellar ataxia and X-linked dystonia-parkinsonism. In other disorders, such as spastic paraplegia, the basis for most of the phenotypic variability remains unclear. Epigenetic factors have been implicated in disorders such as SGCE-related myoclonus-dystonia and HD. Knowledge of the mechanisms underlying phenotypic variation is already starting to influence management strategies and clinical trials for neurogenetic disorders.

Perampanel as a novel treatment for subcortical myoclonus in myoclonus-dystonia syndrome

BACKGROUND

Myoclonus-dystonia (MD) is a syndrome characterized by subcortical myoclonus and milder dystonia. The main causative gene is the epsilon sarcoglycan gene (SGCE), but other genes may be involved. Response to medications is variable, with poor tolerability limiting their use.

CASE PRESENTATION

We present the case of a patient with severe myoclonic jerks and mild dystonia since childhood. At first neurological visit at the age of 46 years old, she presented brief myoclonic jerks predominating in the upper limbs and neck, mild at rest and elicited by action, posture and tactile stimulus. Myoclonus was accompanied by mild neck and right arm dystonia. Neurophysiological tests suggested subcortical origin of myoclonus, brain MRI was unremarkable. Myoclonus-dystonia was diagnosed, and genetic testing identified a novel mutation in SGCE gene (c.907delC) in heterozygosis. Over time she assumed a large variety of anti-epileptics without beneficial effect on myoclonus and low tolerability. Add-on treatment with Perampanel was started, with a beneficial effect. No adverse events were reported. Perampanel is the first selective non-competitive AMPA receptor antagonist approved in add-on for focal and generalized tonic-clonic seizures. To our knowledge, this is the first trial of Perampanel in MD.

CONCLUSIONS

We presented the case of a patient with MD due to SGCE mutation who was treated with Perampanel with beneficial effects. We propose Perampanel as a novel treatment for myoclonus in MD.

Early recognition of SGCE-myoclonus-dystonia in children

AIM

To evaluate early dystonic features in children and adolescents with SGCE-myoclonus-dystonia.

METHOD

In this cross-sectional study, 49 patients (26 females and 23 males) with SGCE-myoclonus-dystonia (aged 15y 2mo, SD 12y) with childhood-onset (2y 10mo, SD 1y 10mo) dystonia were examined using a standardized video recorded protocol. Dystonia was rated using the Writer's Cramp and Gait Dystonia Rating Scales. Disability and impairment for handwriting and walking were also rated.

RESULTS

Dystonia was present at rest (n=1), posture (n=12), and during specific motor tasks (n=45) such as writing (n=35), walking (n=23), and running (n=20). Most children reported disability while performing these tasks. Early dystonic patterns were identified for writer's cramp and gait dystonia, the latter named the 'circular shaking leg', 'dragging leg', and 'hobby-horse gait' patterns. Sensory tricks were used by five and eight children to improve dystonia and myoclonus during writing and walking respectively. The rating scales accurately measured the severity of action dystonia and correlated with self-reported disability.

INTERPRETATION

Children with SGCE-myoclonus-dystonia show recognizable dystonic patterns and sensory tricks that may lead to an early diagnosis and timely therapeutic approach. Isolated writer's cramp is a key feature in childhood and should prompt SCGE analysis. The proposed action dystonia scales could be used to monitor disease course and response to treatment.

WHAT THIS PAPER ADDS

Most children with SGCE-myoclonus-dystonia got writer's cramp and had walking and running dystonia. Writer's cramp was a key feature and should prompt SGCE genetic investigation. 'Circular shaking leg', 'dragging leg', and 'hobby-horse gait' were recognized as early gait patterns. Children used sensory tricks to improve myoclonus and dystonia, suggesting common pathophysiological mechanisms. Action dystonia rating scales are valid tools to assess severity in children.

Cortical neuronal hyperexcitability and synaptic changes in SGCE mutation-positive myoclonus dystonia

Myoclonus Dystonia is a childhood-onset hyperkinetic movement disorder with a combined motor and psychiatric phenotype. It represents one of the few autosomal dominant inherited dystonic disorders and is caused by mutations in the ε-sarcoglycan (SGCE) gene. Work to date suggests that dystonia is caused by disruption of neuronal networks, principally basal ganglia-cerebello-thalamo-cortical circuits. Investigation of cortical involvement has primarily focused on disruption to interneuron inhibitory activity, rather than the excitatory activity of cortical pyramidal neurons. Here, we have sought to examine excitatory cortical glutamatergic activity using two approaches; the CRISPR/Cas9 editing of a human embryonic cell line, generating an SGCE compound heterozygous mutation, and three patient-derived induced pluripotent stem cell lines (iPSC) each gene edited to generate matched wild-type SGCE control lines. Differentiation towards a cortical neuronal phenotype demonstrated no significant differences in neither early- (PAX6, FOXG1) nor late-stage (CTIP2, TBR1) neurodevelopmental markers. However, functional characterisation using Ca2+ imaging and MEA approaches identified an increase in network activity, while single-cell patch clamp studies found a greater propensity towards action potential generation with larger amplitudes and shorter half-widths associated with SGCE-mutations. Bulk-RNA-seq analysis identified gene ontological enrichment for neuron projection development, synaptic signalling, and synaptic transmission. Examination of dendritic morphology found SGCE-mutations to be associated with a significantly higher number of branches and longer branch lengths, together with longer ion-channel dense axon initial segments, particularly towards the latter stages of differentiation (D80 and D100). Gene expression and protein quantification of key synaptic proteins (synaptophysin, synapsin and PSD95), AMPA and NMDA receptor subunits found no significant differences between the SGCE-mutation and matched wild-type lines. By contrast, significant changes to synaptic adhesion molecule expression were identified, namely higher pre-synaptic neurexin-1 and lower post-synaptic neuroligin-4 levels in the SGCE mutation carrying lines. Our study demonstrates an increased intrinsic excitability of cortical glutamatergic neuronal cells in the context of SGCE mutations, coupled with a more complex neurite morphology and disruption to synaptic adhesion molecules. These changes potentially represent key components to the development of the hyperkinetic clinical phenotype observed in Myoclonus Dystonia, as well a central feature to the wider spectrum of dystonic disorders, potentially providing targets for future therapeutic development.

Detection of a new deleterious SGCE gene variant in Moroccan family with inherited myoclonus-dystonia

Myoclonus-dystonia (M-D) is a pleiotropic neuropsychiatric disorder with autosomal dominant mode of inheritance with variable severity and incomplete penetrance. Pathogenic variants in ξ-sarcoglycan gene SGCE are the most frequently known genetic cause of M-D with maternal imprinting, and in most cases, a symptomatic individual inherits the pathogenic variant from his or her father. This work reported a missense mutation c.662G> T inherited in the M-D Moroccan family described for the first time, which is deleterious based on protein modeling analysis.

Identification of Monoallelically Expressed Genes Associated with Economic Traits in Hanwoo (Korean Native Cattle)

Hanwoo, an indigenous Korean cattle breed, has been genetically improved by selecting superior sires called Korean-proven bulls. However, cows still contribute half of the genetic stock of their offspring, and allelic-specific expressed genes have potential, as selective targets of cows, to enhance genetic gain. The aim of this study is to identify genes that have MAEs based on both the genome and transcriptome and to estimate their effects on breeding values (BVs) for economically important traits in Hanwoo. We generated resequencing data for the parents and RNA-sequencing data for the muscle, fat, and brain tissues of the offspring. A total of 3801 heterozygous single nucleotide polymorphisms (SNPs) in offspring were identified and they were located in 1569 genes. Only 14 genes showed MAE (seven expressing maternal alleles and seven expressing paternal alleles). Tissue-specific MAE was observed, and LANCL1 showed maternal allele expression across all tissues. MAE genes were enriched for the biological process of cell death and angiogenesis, which included ACKR3 and PDCL3 genes, whose SNPs were significantly associated with BVs of lean meat production-related traits, such as weight at 12 months of age, carcass weight, and loin eye area. In the current study, monoallelically expressed genes were identified in various adult tissues and these genes were associated with genetic capacity in Hanwoo.

Genomic Imprinting at the Porcine DIRAS3 Locus

Simple Summary

DNA methylation associated with one of the two alleles from parents is an important mechanism that causes a silencing of that allele, leading to expression of another allele only. There has been a lack of detailed studies on DNA methylation and expression patterns that are related to the DIRAS3 gene in pigs. The objective of this study was to provide a comprehensive overview of DNA methylation and expression associated with the DIRAS3 gene in pigs by generating an embryonic pig model and analyzing next-generation sequencing using pig embryos and adult pigs. Our results clearly showed the presence of DNA methylation near the DIRAS3 gene in pigs and high expression of DIRAS3 in the hypothalamus from adult pigs and expression of only one allele in all the tested tissues including the hypothalamus. In summary, our findings suggested DNA methylation might be related to those unique gene expression patterns during the development of pigs.

Abstract

The epigenetic mechanisms underlying genomic imprinting include DNA methylation and monoallelic expression of genes in close proximity. Although genes imprinted in humans and mice have been widely characterized, there is a lack of detailed and comprehensive studies in livestock species including pigs. The purpose of this study was to investigate a detailed methylation status and parent-of-origin-specific gene expression within the genomic region containing an underexamined porcine DIRAS3 locus. Through whole-genome bisulfite sequencing (WGBS) and RNA sequencing (RNA-seq) of porcine parthenogenetic embryos and analyses of public RNA-seq data from adult pigs, DNA methylation and monoallelic expression pattern were investigated. As a result, maternal hypermethylation at the DIRAS3 locus and hypothalamus-specific and monoallelic expression of the DIRAS3 gene were found in pigs. In conclusion, the findings from this study suggest that the presence of maternal hypermethylation, or imprints, might be maintained and related to monoallelic expression of DIRAS3 during pig development.

ε-Sarcoglycan: Unraveling the Myoclonus-Dystonia Gene

Myoclonus-dystonia (MD) is a rare childhood-onset movement disorder, with an estimated prevalence of about 2 per 1,000,.000 in Europe, characterized by myoclonic jerks in combination with focal or segmental dystonia. Pathogenic variants in the gene encoding ε-sarcoglycan (SGCE), a maternally imprinted gene, are the most frequent genetic cause of MD. To date, the exact role of ε-sarcoglycan and the pathogenic mechanisms that lead to MD are still unknown. However, there are more than 40 reported isoforms of human ε-sarcoglycan, pointing to a complex biology of this protein. Additionally, some of these are brain-specific isoforms, which may suggest an important role within the central nervous system. In the present review, we aim to provide an overview of the current state of knowledge of ε-sarcoglycan. We will focus on the genetic landscape of SGCE and the presence and plausible role of ε-sarcoglycan in the brain. Finally, we discuss the importance of the brain-specific isoforms and hypothesize that SGCE may play essential roles in normal synaptic functioning and their alteration will be strongly related to MD.

Challenges in Clinicogenetic Correlations: One Gene - Many Phenotypes

Background

Progress in genetics – particularly the advent of next‐generation sequencing (NGS) – has enabled an unparalleled gene discovery and revealed unmatched complexity of genotype–phenotype correlations in movement disorders. Among other things, it has emerged that mutations in one and the same gene can cause multiple, often markedly different phenotypes. Consequently, movement disorder specialists have increasingly experienced challenges in clinicogenetic correlations.

Objectives

To deconstruct biological phenomena and mechanistic bases of phenotypic heterogeneity in monogenic movement disorders and neurodegenerative diseases. To discuss the evolving role of movement disorder specialists in reshaping disease phenotypes in the NGS era.

Methods

This scoping review details phenomena contributing to phenotypic heterogeneity and their underlying mechanisms.

Results

Three phenomena contribute to phenotypic heterogeneity, namely incomplete penetrance, variable expressivity and pleiotropy. Their underlying mechanisms, which are often shared across phenomena and non‐mutually exclusive, are not fully elucidated. They involve genetic factors (ie, different mutation types, dynamic mutations, somatic mosaicism, intragenic intra‐ and inter‐allelic interactions, modifiers and epistatic genes, mitochondrial heteroplasmy), epigenetic factors (ie, genomic imprinting, X‐chromosome inactivation, modulation of genetic and chromosomal defects), and environmental factors.

Conclusion

Movement disorders is unique in its reliance on clinical judgment to accurately define disease phenotypes. This has been reaffirmed by the NGS revolution, which provides ever‐growing sequencing data and fuels challenges in variant pathogenicity assertions for such clinically heterogeneous disorders. Deep phenotyping, with characterization and continual updating of “core” phenotypes, and comprehension of determinants of genotype–phenotype complex relationships are crucial for clinicogenetic correlations and have implications for the diagnosis, treatment and counseling.

Functional and Molecular Properties of DYT-SGCE Myoclonus-Dystonia Patient-Derived Striatal Medium Spiny Neurons

Myoclonus-dystonia (DYT-SGCE, formerly DYT11) is characterized by alcohol-sensitive, myoclonic-like appearance of fast dystonic movements. It is caused by mutations in the SGCE gene encoding ε-sarcoglycan leading to a dysfunction of this transmembrane protein, alterations in the cerebello-thalamic pathway and impaired striatal plasticity. To elucidate underlying pathogenic mechanisms, we investigated induced pluripotent stem cell (iPSC)-derived striatal medium spiny neurons (MSNs) from two myoclonus-dystonia patients carrying a heterozygous mutation in the SGCE gene (c.298T>G and c.304C>T with protein changes W100G and R102X) in comparison to two matched healthy control lines. Calcium imaging showed significantly elevated basal intracellular Ca2+ content and lower frequency of spontaneous Ca2+ signals in SGCE MSNs. Blocking of voltage-gated Ca2+ channels by verapamil was less efficient in suppressing KCl-induced Ca2+ peaks of SGCE MSNs. Ca2+ amplitudes upon glycine and acetylcholine applications were increased in SGCE MSNs, but not after GABA or glutamate applications. Expression of voltage-gated Ca2+ channels and most ionotropic receptor subunits was not altered. SGCE MSNs showed significantly reduced GABAergic synaptic density. Whole-cell patch-clamp recordings displayed elevated amplitudes of miniature postsynaptic currents and action potentials in SGCE MSNs. Our data contribute to a better understanding of the pathophysiology and the development of novel therapeutic strategies for myoclonus-dystonia.

Mutation in ε-Sarcoglycan Induces a Myoclonus-Dystonia Syndrome-Like Movement Disorder in Mice

Myoclonus dystonia syndrome (MDS) is an inherited movement disorder, and most MDS-related mutations have so far been found in the ε-sarcoglycan (SGCE) coding gene. By generating SGCE-knockout (KO) and human 237 C > T mutation knock-in (KI) mice, we showed here that both KO and KI mice exerted typical movement defects similar to those of MDS patients. SGCE promoted filopodia development in vitro and inhibited excitatory synapse formation both in vivo and in vitro. Loss of function of SGCE leading to excessive excitatory synapses that may ultimately contribute to MDS pathology. Indeed, using a zebrafish MDS model, we found that among 1700 screened chemical compounds, Vigabatrin was the most potent in readily reversing MDS symptoms of mouse disease models. Our study strengthens the notion that mutations of SGCE lead to MDS and most likely, SGCE functions to brake synaptogenesis in the CNS.

The Landscape of Genomic Imprinting at the Porcine SGCE/PEG10 Locus from Methylome and Transcriptome of Parthenogenetic Embryos

In mammals, imprinted genes often exist in the form of clusters in specific chromosome regions. However, in pigs, genomic imprinting of a relatively few genes and clusters has been identified, and genes within or adjacent to putative imprinted clusters need to be investigated including those at the SGCE/PEG10 locus. The objective of this study was to, using porcine parthenogenetic embryos, investigate imprinting status of genes within the genomic region spans between the COL1A2 and ASB4 genes in chromosome 9. Whole-genome bisulfite sequencing (WGBS) and RNA sequencing (RNA-seq) were conducted with normal and parthenogenetic embryos, and methylome and transcriptome were analyzed. As a result, differentially methylated regions (DMRs) between the embryos were identified, and parental allele-specific expressions of the SGCE and PEG10 genes were verified. The pig imprinted interval was limited between SGCE and PEG10, since both the COL1A2 and CASD1 genes at the centromere-proximal region and the genes between PPP1R9A and ASB4 toward the telomere were non-imprinted and biallelically expressed. Consequently, our combining analyses of methylome, transcriptome, and informative polymorphisms revealed the boundary of imprinting cluster at the SGCE/PEG10 locus in pig chromosome 9 and consolidated the landscape of genomic imprinting in pigs.

Acute cerebellar knockdown of Sgce reproduces salient features of myoclonus-dystonia (DYT11) in mice

Myoclonus dystonia (DYT11) is a movement disorder caused by loss-of-function mutations in SGCE and characterized by involuntary jerking and dystonia that frequently improve after drinking alcohol. Existing transgenic mouse models of DYT11 exhibit only mild motor symptoms, possibly due to rodent-specific developmental compensation mechanisms, which have limited the study of neural mechanisms underlying DYT11. To circumvent potential compensation, we used short hairpin RNA (shRNA) to acutely knock down Sgce in the adult mouse and found that this approach produced dystonia and repetitive, myoclonic-like, jerking movements in mice that improved after administration of ethanol. Acute knockdown of Sgce in the cerebellum, but not the basal ganglia, produced motor symptoms, likely due to aberrant cerebellar activity. The acute knockdown model described here reproduces the salient features of DYT11 and provides a platform to study the mechanisms underlying symptoms of the disorder, and to explore potential therapeutic options.

Twenty years on: Myoclonus-dystonia and ε-sarcoglycan - neurodevelopment, channel, and signaling dysfunction

Myoclonus-dystonia is a clinical syndrome characterized by a typical childhood onset of myoclonic jerks and dystonia involving the neck, trunk, and upper limbs. Psychiatric symptomatology, namely, alcohol dependence and phobic and obsessive-compulsive disorder, is also part of the clinical picture. Zonisamide has demonstrated effectiveness at reducing both myoclonus and dystonia, and deep brain stimulation seems to be an effective and long-lasting therapeutic option for medication-refractory cases. In a subset of patients, myoclonus-dystonia is associated with pathogenic variants in the epsilon-sarcoglycan gene, located on chromosome 7q21, and up to now, more than 100 different pathogenic variants of the epsilon-sarcoglycan gene have been described. In a few families with a clinical phenotype resembling myoclonus-dystonia associated with distinct clinical features, variants have been identified in genes involved in novel pathways such as calcium channel regulation and neurodevelopment. Because of phenotypic similarities with epsilon-sarcoglycan gene-related myoclonus-dystonia, these conditions can be collectively classified as "myoclonus-dystonia syndromes." In the present article, we present myoclonus-dystonia caused by epsilon-sarcoglycan gene mutations, with a focus on genetics and underlying disease mechanisms. Second, we review those conditions falling within the spectrum of myoclonus-dystonia syndromes, highlighting their genetic background and involved pathways. Finally, we critically discuss the normal and pathological function of the epsilon-sarcoglycan gene and its product, suggesting a role in the stabilization of the dopaminergic membrane via regulation of calcium homeostasis and in the neurodevelopmental process involving the cerebello-thalamo-pallido-cortical network. © 2019 International Parkinson and Movement Disorder Society.

Movement Disorders in Children

PURPOSE OF REVIEW

This article provides an overview of the clinical features and disorders associated with movement disorders in childhood. This article discusses movement disorder phenomena and their clinical presentation in infants and children and presents a diagnostic approach to suspected genetic disorders with a focus on treatable conditions.

RECENT FINDINGS

Technologic advances in molecular genetic testing over the past decade continue to lead to the discovery of new diseases. This article discusses the clinical presentation and early experience with treatment for several recently described genetic forms of infantile-onset and childhood-onset dystonia and chorea.

SUMMARY

The clinical spectrum of pediatric movement disorders is broad and heterogeneous, ranging from acute or transient self-limited conditions to conditions that cause profound lifelong motor disability. Most movement disorders in childhood are chronic, and the large number of rare, genetic conditions associated with pediatric movement disorders can pose a significant diagnostic challenge. Recognition of distinctive diagnostic clues in the history and examination can facilitate the diagnosis of potentially treatable disorders.

Screening for SGCE mutations in Moroccan sporadic patients with Myoclonus-Dystonia syndrome

Myoclonus-Dystonia (M-D) is a rare autosomal-dominant movement disorder characterized by myoclonic jerks in combination with dystonia and psychiatric features. Mutations in the Epsilon-sarcoglycan (SGCE, DYT11) gene have been found to cause M-D in 30%-50% of familial M-D. Sporadic cases have also been reported. The aim of study was to investigate whether the M-D phenotype is associated with the existence of SGCE mutations in Moroccan sporadic patients with M-D syndrome. The study included 12 M-D patients. We sequenced the entire coding region of the SGCE gene. We identified two different heterozygous SGCE mutations (c.769A > C ; c.391-3T > C). Our finding confirm that SGCE mutations can occur in sporadic patients when the phenotype is consistent with M-D. Further functional studies are needed to show how changes in SGCE protein function lead to the M-D phenotype.

Analysis of experience-regulated transcriptome and imprintome during critical periods of mouse visual system development reveals spatiotemporal dynamics

Visual system development is light-experience dependent, which strongly implicates epigenetic mechanisms in light-regulated maturation. Among many epigenetic processes, genomic imprinting is an epigenetic mechanism through which monoallelic gene expression occurs in a parent-of-origin-specific manner. It is unknown if genomic imprinting contributes to visual system development. We profiled the transcriptome and imprintome during critical periods of mouse visual system development under normal- and dark-rearing conditions using B6/CAST F1 hybrid mice. We identified experience-regulated, isoform-specific and brain-region-specific imprinted genes. We also found imprinted microRNAs were predominantly clustered into the Dlk1-Dio3 imprinted locus with light experience affecting some imprinted miRNA expression. Our findings provide the first comprehensive analysis of light-experience regulation of the transcriptome and imprintome during critical periods of visual system development. Our results may contribute to therapeutic strategies for visual impairments and circadian rhythm disorders resulting from a dysfunctional imprintome.

Faithful SGCE imprinting in iPSC-derived cortical neurons: an endogenous cellular model of myoclonus-dystonia

In neuropathology research, induced pluripotent stem cell (iPSC)-derived neurons are considered a tool closely resembling the patient brain. Albeit in respect to epigenetics, this concept has been challenged. We generated iPSC-derived cortical neurons from myoclonus-dystonia patients with mutations (W100G and R102X) in the maternally imprinted ε-sarcoglycan (SGCE) gene and analysed properties such as imprinting, mRNA and protein expression. Comparison of the promoter during reprogramming and differentiation showed tissue-independent differential methylation. DNA sequencing with methylation-specific primers and cDNA analysis in patient neurons indicated selective expression of the mutated paternal SGCE allele. While fibroblasts only expressed the ubiquitous mRNA isoform, brain-specific SGCE mRNA and ε-sarcoglycan protein were detected in iPSC-derived control neurons. However, neuronal protein levels were reduced in both mutants. Our phenotypic characterization highlights the suitability of iPSC-derived cortical neurons with SGCE mutations for myoclonus-dystonia research and, in more general terms, prompts the use of iPSC-derived cellular models to study epigenetic mechanisms impacting on health and disease.

Bilateral pallidal deep brain stimulation in myoclonus-dystonia: our experience in three cases and their follow-up

BACKGROUND

Myoclonus-dystonia syndrome (MDS) is an autosomal dominant movement disorder caused by mutations in the SGCE gene. MDS is characterized by mild dystonia and myoclonic jerks, and a constellation of psychiatric manifestations. Deep brain stimulation (DBS) of bilateral internal globus pallidus (GPi) has recently been introduced as a new and beneficial technique to improve motor symptoms in MDS.

METHODS

We report three proven genetically MDS cases with successful response to DBS, and their clinical evolution over years.

RESULTS

DBS improves significantly the Unified Myoclonus Rating Scale and Burke-Fahn-Marsden Dystonia Rating Scale in all three patients. This improvement is sustained over the years and no major adverse events were recorded. DBS stimulation parameters employed are justified and compared with cases reported throughout the literature.

DISCUSSION

DBS of bilateral GPi is an effective and safe therapy to be considered in MDS refractory cases. Careful neuropsychological evaluation is essential inside the presurgery planning. Correct location of the DBS electrodes and individualized selection of stimulation parameters in each case are the main determinants of the best clinical response.

Analysis of Genome-Wide Monoallelic Expression Patterns in Three Major Cell Types of Mouse Visual Cortex Using Laser Capture Microdissection

Genomic imprinting is an epigenetic mechanism causing monoallelic expression in a parent-of-origin-specific manner. Disruption of imprinted genes causes various neurological and psychiatric disorders. However, the role of imprinted genes in the brain is largely unknown. Different cell types within distinct brain regions can influence the genomic imprinting status, but imprinted genes in single cell types within distinct brain regions have not been characterized on a genome-wide scale. To address this critical question, we used a multi-stage approach, which combined genetically engineered mice with fluorescence-based laser capture microdissection (LCM) to capture excitatory neurons, inhibitory neurons and astrocytes as single cells in layer 2/3 of mouse visual cortex. RNA sequencing determined parental expression patterns on a genome-wide scale in the captured cells within specific brain regions. The expression level of cell-type-specific genes for excitatory neurons (13 genes), inhibitory neurons (16 genes) and astrocytes (20 genes) confirmed the LCM-captured cells maintained their cellular identities. The parent-of-origin-specific expression pattern of imprinted genes, including maternally expressed Meg3 and paternally expressed Peg3, provided evidence that the status of known imprinted genes was also maintained. Although our platform remains to be improved, our findings demonstrate the parental expression pattern can be analysed not only at the level of a single cell type but also at the level of specific cortical layers. Our approach has the potential to reveal novel regulatory modules associated with plasticity through genomic imprinting mechanisms in different cell types, not only in the visual cortex but also in other brain regions.

Speech-activated Myoclonus Mimicking Stuttering in a Patient with Myoclonus-Dystonia Syndrome

BACKGROUND

Acquired neurogenic stuttering has been considered a fairly uncommon clinical occurrence; speech-activated myoclonus is a rare entity that can mimic stuttering and is caused by a wide array of etiologies.

CASE REPORT

Here we report a patient with myoclonus-dystonia syndrome (MDS), due to an identified disease-causing mutation, who displayed speech-activated myoclonus mimicking stuttering.

DISCUSSION

In MDS, myoclonus has only infrequently been reported to affect speech. This case further expands the spectrum of conditions causing the rare clinical phenomenon of speech-activated myoclonus.

Distribution and Coexistence of Myoclonus and Dystonia as Clinical Predictors of SGCE Mutation Status: A Pilot Study

Introduction

Myoclonus–dystonia (M–D) is a young onset movement disorder typically involving myoclonus and dystonia of the upper body. A proportion of the cases are caused by mutations to the autosomal dominantly inherited, maternally imprinted, epsilon-sarcoglycan gene (SGCE). Despite several sets of diagnostic criteria, identification of patients most likely to have an SGCE mutation remains difficult.

Methods

Forty consecutive patients meeting pre-existing diagnostic clinical criteria for M–D underwent a standardized clinical examination (20 SGCE mutation positive and 20 negative). Each video was reviewed and systematically scored by two assessors blinded to mutation status. In addition, the presence and coexistence of myoclonus and dystonia was recorded in four body regions (neck, arms, legs, and trunk) at rest and with action.

Results

Thirty-nine patients were included in the study (one case was excluded owing to insufficient video footage). Based on previously proposed diagnostic criteria, patients were subdivided into 24 “definite,” 5 “probable,” and 10 “possible” M–D. Motor symptom severity was higher in the SGCE mutation-negative group. Myoclonus and dystonia were most commonly observed in the neck and upper limbs of both groups. Truncal dystonia with action was significantly seen more in the mutation-negative group (p < 0.05). Coexistence of myoclonus and dystonia in the same body part with action was more commonly seen in the mutation-negative cohort (p < 0.05).

Conclusion

Truncal action dystonia and coexistence of myoclonus and dystonia in the same body part with action might suggest the presence of an alternative mutation in patients with M–D.

Sporadic and familial myoclonic dystonia: Report of three cases and review of literature

Myoclonic dystonia refers to a clinical syndrome characterized by rapid jerky movements along with dystonic posturing of the limbs. Clinically, it is characterized by sudden, brief, electric shock-like movements, mostly involving the upper extremities, shoulders, neck and trunk. Characteristically, the movements wane with consumption of small dose of alcohol in about 50% of cases. Additionally, dystonic contractions are observed in most of the patients in the affected body parts and some patients may exhibit cervical dystonia or graphospasm as well. It may manifest as an autosomal dominant condition or sometimes, as a sporadic entity, though there are doubts whether these represent cases with reduced penetrance. The condition is usually treated with a combination of an anticholinergic agent like, benztropine, pimozide and tetrabenazine. We report one sporadic case and one familial case where the father and the son are affected. The cases were collected from the Movement Disorders Clinic of Bangur Institute of Neurosciences, Kolkata, West Bengal in a period of ten months. Myoclonic dystonia is a rare condition and to the best of our knowledge, this series is the first one reported from our country. Videos of the patients are also provided with the article.

Progression of neuropsychiatric and cognitive features due to exons 2 to 5 deletion in the epsilon-sarcoglycan gene: a case report

Physical symptoms of myoclonus dystonia due to epsilon-sarcoglycan mutations are well documented; however, the progression of neuropsychiatric and cognitive symptoms remains unclear. We present a case of a 34-year-old woman with early childhood onset of myoclonic jerks, dystonic posture and developmental delay due to exons 2 to 5 deletion in the epsilon-sarcoglycan gene. Over time, she developed neuropsychiatric symptoms. She underwent bilateral deep brain stimulation of the ventral intermediate nucleus of the thalamus for her motor symptoms, which greatly improved but she exhibited slow deterioration of her neuropsychiatric and cognitive symptoms, particularly apathy, aggression and severe executive dysfunction.

SGCE and myoclonus dystonia: motor characteristics, diagnostic criteria and clinical predictors of genotype

Myoclonus dystonia syndrome (MDS) is a young-onset movement disorder. A proportion of cases are due to mutations in the maternally imprinted SGCE gene. We assembled the largest cohort of MDS patients to date, and determined the frequency and type of SGCE mutations. The aim was to establish the motor phenotype in mutation carriers and utility of current diagnostic criteria. Eighty-nine probands with clinical features compatible with MDS were recruited from the UK and Ireland. Patients were phenotypically classified as "definite", "probable" or "possible" MDS according to previous guidelines. SGCE was analyzed using direct sequencing and copy number variant analysis. In those where no mutation was found, DYT1 (GAG deletion), GCH1, THAP1 and NKX2.1 genes were also sequenced. Nineteen (21.3%) probands had an SGCE mutation. Three patterns of motor symptoms emerged: (1) early childhood onset upper body myoclonus and dystonia, (2) early childhood onset lower limb dystonia, progressing later to more pronounced myoclonus and upper body involvement, and (3) later childhood onset upper body myoclonus and dystonia with evident cervical involvement. Five probands had large contiguous gene deletions ranging from 0.7 to 2.3 Mb in size with distinctive clinical features, including short stature, joint laxity and microcephaly. Our data confirms that SGCE mutations are most commonly identified in MDS patients with (1) age at onset ≤10 years and (2) predominant upper body involvement of a pure myoclonus-dystonia. Cases with whole SGCE gene deletions had additional clinical characteristics, which are not always predicted by deletion size or gene involvement.

Where genotype is not predictive of phenotype: towards an understanding of the molecular basis of reduced penetrance in human inherited disease

Some individuals with a particular disease-causing mutation or genotype fail to express most if not all features of the disease in question, a phenomenon that is known as 'reduced (or incomplete) penetrance'. Reduced penetrance is not uncommon; indeed, there are many known examples of 'disease-causing mutations' that fail to cause disease in at least a proportion of the individuals who carry them. Reduced penetrance may therefore explain not only why genetic diseases are occasionally transmitted through unaffected parents, but also why healthy individuals can harbour quite large numbers of potentially disadvantageous variants in their genomes without suffering any obvious ill effects. Reduced penetrance can be a function of the specific mutation(s) involved or of allele dosage. It may also result from differential allelic expression, copy number variation or the modulating influence of additional genetic variants in cis or in trans. The penetrance of some pathogenic genotypes is known to be age- and/or sex-dependent. Variable penetrance may also reflect the action of unlinked modifier genes, epigenetic changes or environmental factors. At least in some cases, complete penetrance appears to require the presence of one or more genetic variants at other loci. In this review, we summarize the evidence for reduced penetrance being a widespread phenomenon in human genetics and explore some of the molecular mechanisms that may help to explain this enigmatic characteristic of human inherited disease.

Identification of novel gene targets and functions of p21-activated kinase 1 during DNA damage by gene expression profiling

P21-activated kinase 1 (PAK1), a serine/threonine protein kinase, modulates many cellular processes by phosphorylating its downstream substrates. In addition to its role in the cytoplasm, PAK1 also affects gene transcription due to its nuclear localization and association with chromatin. It is now recognized that PAK1 kinase activity and its nuclear translocation are rapidly stimulated by ionizing radiation (IR), and that PAK1 activation is a component of the DNA damage response. Owing to the role of PAK1 in the cell survival, its association with the chromatin, and now, stimulation by ionizing radiation, we hypothesize that PAK1 may be contributing to modulation of genes with roles in cellular processes that might be important in the DNA damage response. The purpose of this study was to identify new PAK1 targets in response to ionizing radiation with putative role in the DNA damage response. We examined the effect of IR on the gene expression patterns in the murine embryonic fibroblasts with or without Pak1 using microarray technology. Differentially expressed transcripts were identified using Gene Spring GX 10.0.2. Pathway, network, functional analyses and gene family classification were carried out using Kyoto Encyclopedia of Genes and Genomes (KEGG), Ingenuity Pathway, Gene Ontology and PANTHER respectively. Selective targets of PAK1 were validated by RT-qPCR. For the first time, we provide a genome-wide analysis of PAK1 and identify its targets with potential roles in the DNA damage response. Gene Ontology analysis identified genes in the IR-stimulated cells that were involved in cell cycle arrest and cell death. Pathway analysis revealed p53 pathway being most influenced by IR responsive, PAK1 targets. Gene family of transcription factors was over represented and gene networks involved in DNA replication, repair and cellular signaling were identified. In brief, this study identifies novel PAK1 dependent IR responsive genes which reveal new aspects of PAK1 biology.

Recent advances in the molecular pathogenesis of dystonia-plus syndromes and heredodegenerative dystonias

The majority of studies investigating the molecular pathogenesis and cell biology underlying dystonia have been performed in individuals with primary dystonia. This includes monogenic forms such as DYT1and DYT6 dystonia, and primary focal dystonia which is likely to be multifactorial in origin. In recent years there has been renewed interest in non-primary forms of dystonia including the dystonia-plus syndromes and heredodegenerative disorders. These are caused by a variety of genetic mutations and their study has contributed to our understanding of the neuronal dysfunction that leads to dystonia These findings have reinforced themes identified from study of primary dystonia including abnormal dopaminergic signalling, cellular trafficking and mitochondrial function. In this review we highlight recent advances in the understanding of the dystonia-plus syndromes and heredodegenerative dystonias.

[Dystonia genes and elucidation of their roles in dystonia pathogenesis]

Identification of causative genes for hereditary dystonia and elucidation of their functions are crucial for better understanding of dystonia pathogenesis. As seen in other hereditary neurologic disorders, intra- and inter-familial clinical variations have been demonstrated in hereditary dystonia. Asymptomatic carriers can be found due to alterations in penetrance, generally reduced in succeeding generations. Current known dystonia genes include those related to dopamine metabolism, transcription factor, cytoskeleton, transport of glucose and sodium ion, etc. It has been reported that effects of deep brain stimulation can vary significantly depending on genotype. Accumulation of genotype-outcome correlations would contribute to treatment decisions for dystonia patients.

The genetics of dystonia: new twists in an old tale

Dystonia is a common movement disorder seen by neurologists in clinic. Genetic forms of the disease are important to recognize clinically and also provide valuable information about possible pathogenic mechanisms within the wider disorder. In the past few years, with the advent of new sequencing technologies, there has been a step change in the pace of discovery in the field of dystonia genetics. In just over a year, four new genes have been shown to cause primary dystonia (CIZ1, ANO3, TUBB4A and GNAL), PRRT2 has been identified as the cause of paroxysmal kinesigenic dystonia and other genes, such as SLC30A10 and ATP1A3, have been linked to more complicated forms of dystonia or new phenotypes. In this review, we provide an overview of the current state of knowledge regarding genetic forms of dystonia—related to both new and well-known genes alike—and incorporating genetic, clinical and molecular information. We discuss the mechanistic insights provided by the study of the genetic causes of dystonia and provide a helpful clinical algorithm to aid clinicians in correctly predicting the genetic basis of various forms of dystonia.

SGCE mutations cause psychiatric disorders: clinical and genetic characterization

Myoclonus dystonia syndrome is a childhood onset hyperkinetic movement disorder characterized by predominant alcohol responsive upper body myoclonus and dystonia. A proportion of cases are due to mutations in the maternally imprinted SGCE gene. Previous studies have suggested that patients with SGCE mutations may have an increased rate of psychiatric disorders. We established a cohort of patients with myoclonus dystonia syndrome and SGCE mutations to determine the extent to which psychiatric disorders form part of the disease phenotype. In all, 89 patients with clinically suspected myoclonus dystonia syndrome were recruited from the UK and Ireland. SGCE was analysed using direct sequencing and for copy number variants. In those patients where no mutation was found TOR1A (GAG deletion), GCH1, THAP1 and NKX2-1 were also sequenced. SGCE mutation positive cases were systematically assessed using standardized psychiatric interviews and questionnaires and compared with a disability-matched control group of patients with alcohol responsive tremor. Nineteen (21%) probands had a SGCE mutation, five of which were novel. Recruitment of family members increased the affected SGCE mutation positive group to 27 of whom 21 (77%) had psychiatric symptoms. Obsessive-compulsive disorder was eight times more likely (P < 0.001) in mutation positive cases, compulsivity being the predominant feature (P < 0.001). Generalized anxiety disorder (P = 0.003) and alcohol dependence (P = 0.02) were five times more likely in mutation positive cases than tremor controls. SGCE mutations are associated with a specific psychiatric phenotype consisting of compulsivity, anxiety and alcoholism in addition to the characteristic motor phenotype. SGCE mutations are likely to have a pleiotropic effect in causing both motor and specific psychiatric symptoms.

Myoclonus-dystonia and Silver-Russell syndrome resulting from maternal uniparental disomy of chromosome 7

Myoclonus-dystonia (M-D) is a movement disorder that is often associated with mutations in epsilon-sarcoglycan (SGCE), a maternally imprinted gene at 7q21.3. We report a 24-year-old male with short stature (<5th percentile) and a movement disorder clinically consistent with M-D. Single nucleotide polymorphism (SNP) array did not identify significant copy number changes, but revealed three long continuous stretches of homozygosity on chromosome 7 suggestive of uniparental disomy. Parental SNP arrays confirmed that the proband had maternal uniparental disomy of chromosome 7 (mUPD7) with regions of heterodisomy and isodisomy. mUPD7 is the cause of approximately 5-10% of Silver-Russell syndrome (SRS), a disorder characterized by prenatal and postnatal growth retardation. Although SRS was not suspected in our patient, these findings explain his short stature. SGCE methylation testing showed loss of the unmethylated paternal allele. Our findings provide a unifying diagnosis for his short stature and M-D and help to optimize his medication regimen. In conclusion, we show that M-D is a clinical feature that may be associated with SRS due to mUPD7. Individuals with mUPD7 should be monitored for the development of movement disorders. Conversely, individuals with M-D and short stature should be evaluated for SRS.

Incomplete nonsense-mediated decay facilitates detection of a multi-exonic deletion mutation in SGCE

Mutations in SGCE represent the major cause of the myoclonus-dystonia syndrome (DYT11), an autosomal dominant disorder of reduced penetrance. Virtually all affected individuals have myoclonus, which is concentrated in the upper extremities, neck and trunk. Over half of patients have dystonia, usually affecting the neck or arms. SGCE is maternally imprinted. Of the more than 70 SGCE mutations reported in the literature, 18 are large deletions disrupting at least one exon. Therefore, testing for exonic deletions should be considered in individuals with a classic phenotype in whom Sanger sequencing is unrevealing. However, standard methodologies for detection of exonic deletion mutations are expensive, labor intensive and can produce false negatives. Herein, we report the use of cDNA derived from leukocyte RNA to identify a deletion mutation (exons 4 and 5) of SGCE in a family with DYT11. Residual RNA from incomplete nonsense-mediated decay permitted reverse transcription to cDNA. Breakpoints of the 8939 bp heterozygous deletion were then defined with long-range polymerase chain reaction and Sanger sequencing. Use of cDNA generated by reverse transcription of leukocyte RNA can reduce the costs associated with diagnostic genetic testing and can facilitate detection of deletion mutations.

Beckwith-Wiedemann syndrome in sibs discordant for IC2 methylation

Genetically heterogeneous imprinting disorders include Beckwith-Wiedemann syndrome (BWS) and multiple maternal hypomethylation syndrome (MMHS). Using DNA sequencing, quantitative PCR, SNuPE, pyrosequencing, and hybridization to the Illumina GoldenGate Methylation Cancer Panel 1 array, we characterized the genomic DNA of two brothers with BWS who were discordant for loss of methylation at several differentially methylated regions (DMR), including imprinting center 2 (IC2) on chromosome band 11p15.5, which is often hypomethylated in BWS. In keeping with MMHS, the elder child had hypomethylation of SGCE and PLAGL1 as well as of IC2, whereas the younger brother demonstrated no loss of methylation at these DMRs. Although this discordance is consistent with the observation that 15-20% of individuals with BWS do not have detectable genetic or epigenetic alterations of 11p15.5, this is the first report of familial recurrence of BWS with discordance for chromosomal 11p15.5 alterations. We hypothesize that this apparent discordance arises either from mosaicism precluding identification of IC2 hypomethylation in blood or buccal mucosa DNA of the younger child, or from hypomethylation at a site not interrogated by our molecular studies.