Spectrum and time course of epilepsy and the associated cognitive decline in MECP2 duplication syndrome

Effects of MeCP2 on chronic seizures and cognitive function in mice with temporal lobe epilepsy

Mutations in methyl CpG binding protein 2 (MeCP2) are linked to Rett syndrome, in which epilepsy is one of the most well-described disorders. However, little is known about the specific role of MeCP2 during epileptogenesis. Our previous study has demonstrated that MeCP2 has a unique control on the development of mossy fiber sprouting (MFS) in the epileptic hippocampus. This study aimed to (1) examine whether MeCP2 affects spontaneous recurrent seizures (SRSs) and cognitive deficits in mice with pilocarpine-induced epilepsy, and (2) profile MeCP2's downstream molecular events. In the dentate gyrus (DG), we found that over-expression or suppression of MeCP2 significantly reduced or increased the frequency, duration, and number of stage 5 seizures of SRSs during the chronic stage after the SE. Over-expression of MeCP2 improved cognitive deficits in TLE mice, while exacerbated cognitive performances were observed following MeCP2 knockdown. Chromatin immunoprecipitation sequencing (ChIP-seq) and RNA-sequence analyses revealed that MeCP2-targeted genes have far‑reaching impacts on the pathophysiological events during epileptogenesis, including neuron differentiation, neurogenesis, axon guidance, and so on.

Comprehensive assessment reveals numerous clinical and neurophysiological differences between MECP2-allelic disorders

OBJECTIVE

Rett syndrome (RTT) and MECP2 duplication syndrome (MDS) result from under- and overexpression of MECP2, respectively. Preclinical studies using genetic-based treatment showed robust phenotype recovery for both MDS and RTT. However, there is a risk of converting MDS to RTT, or vice versa, if accurate MeCP2 levels are not achieved. The aim of this study was to identify biomarkers distinguishing RTT from MDS.

MATERIALS AND METHODS

We prospectively enrolled 11 MDS and 6 male RTT like (MRL) individuals for a panel of clinical and neurophysiological assessments over two visits, 8-10 months apart.

RESULTS

We identified numerous clinical and physiological features as promising biomarkers. MRL individuals exhibited large amplitude whole body tremor, midline stereotypies (vs. hand flapping at sides in MDS), earlier neuromotor regression, and earlier onset but less commonly refractory epilepsy. In the neurophysiological domain, we observed several marked differences in sleep physiology between MDS/MRL and typically developing (TD) individuals including reduced sleeping time, increased delta power during rapid eye movement (REM) sleep, decreased occipital alpha and increased brain-wide delta power during wakefulness, and reduced spindle density and duration. MRL individuals also had much lower delta power during NREM 2 and 3 stages than the TD group. We found differences in spindle duration in the temporal lobes and spindle amplitude in the frontal lobes between MDS and MRL.

DISCUSSION

Our study revealed distinct clinical features of MDS and MRL that can be monitored during a clinical trial and may serve as target engagement, disease progression, or safety biomarkers for interventional studies.

An RNA editing strategy rescues gene duplication in a mouse model of MECP2 duplication syndrome and nonhuman primates

Duplication of methyl-CpG-binding protein 2 (MECP2) gene causes MECP2 duplication syndrome (MDS). To normalize the duplicated MECP2 in MDS, we developed a high-fidelity Cas13Y (hfCas13Y) system capable of targeting the MECP2 (hfCas13Y-gMECP2) messenger RNA for degradation and reducing protein levels in the brain of humanized MECP2 transgenic mice. Moreover, the intracerebroventricular adeno-associated virus (AAV) delivery of hfCas13Y-gMECP2 in newborn or adult MDS mice restored dysregulated gene expression and improved behavior deficits. Notably, treatment with AAV9-hfCas13Y-gMECP2 extended the median survival of MECP2 transgenic mice from 156.5 to 226 d. Furthermore, studies with monkeys showed a single injection of AAV9-hfCas13Y-gMECP2 was sufficient to drive robust expression of hfCas13Y in widespread brain regions, with MECP2 knockdown efficiency reaching 52.19 ± 0.03% and significantly decreased expression of biomarker gene GDF11. Our results demonstrate that the RNA-targeting hfCas13Y-gMECP2 system is an effective intervention for MDS, providing a potential strategy for treating other dosage-sensitive diseases.

Structural variant allelic heterogeneity in MECP2 duplication syndrome provides insight into clinical severity and variability of disease expression

BACKGROUND

MECP2 Duplication Syndrome, also known as X-linked intellectual developmental disorder Lubs type (MRXSL; MIM: 300260), is a neurodevelopmental disorder caused by copy number gains spanning MECP2. Despite varying genomic rearrangement structures, including duplications and triplications, and a wide range of duplication sizes, no clear correlation exists between DNA rearrangement and clinical features. We had previously demonstrated that up to 38% of MRXSL families are characterized by complex genomic rearrangements (CGRs) of intermediate complexity (2 ≤ copy number variant breakpoints < 5), yet the impact of these genomic structures on regulation of gene expression and phenotypic manifestations have not been investigated.

METHODS

To study the role of the genomic rearrangement structures on an individual's clinical phenotypic variability, we employed a comprehensive genomics, transcriptomics, and deep phenotyping analysis approach on 137 individuals affected by MRXSL. Genomic structural information was correlated with transcriptomic and quantitative phenotypic analysis using Human Phenotype Ontology (HPO) semantic similarity scores.

RESULTS

Duplication sizes in the cohort ranging from 64.6 kb to 16.5 Mb were classified into four categories comprising of tandem duplications (48%), terminal duplications (22%), inverted triplications (20%), and other CGRs (10%). Most of the terminal duplication structures consist of translocations (65%) followed by recombinant chromosomes (23%). Notably, 65% of de novo events occurred in the Terminal duplication group in contrast with 17% observed in Tandem duplications. RNA-seq data from lymphoblastoid cell lines indicated that the MECP2 transcript quantity in MECP2 triplications is statistically different from all duplications, but not between other classes of genomic structures. We also observed a significant (p < 0.05) correlation (Pearson R = 0.6, Spearman p = 0.63) between the log-transformed MECP2 RNA levels and MECP2 protein levels, demonstrating that genomic aberrations spanning MECP2 lead to altered MECP2 RNA and MECP2 protein levels. Genotype-phenotype analyses indicated a gradual worsening of phenotypic features, including overall survival, developmental levels, microcephaly, epilepsy, and genitourinary/eye abnormalities in the following order: Tandem duplications, Other complex duplications, Terminal duplications/Translocations, and Triplications encompassing MECP2.

CONCLUSION

In aggregate, this combined analysis uncovers an interplay between MECP2 dosage, genomic rearrangement structure and phenotypic traits. Whereas the level of MECP2 is a key determinant of the phenotype, the DNA rearrangement structure can contribute to clinical severity and disease expression variability. Employing this type of analytical approach will advance our understanding of the impact of genomic rearrangements on genomic disorders and may help guide more targeted therapeutic approaches.

Imbalance between hippocampal projection cell and parvalbumin interneuron architecture increases epileptic susceptibility in mouse model of methyl CpG binding protein 2 duplication syndrome

OBJECTIVE

Methyl CpG-binding protein 2 (MECP2) duplication syndrome is a rare X-linked genomic disorder affecting predominantly males, which is usually manifested as epilepsy and autism spectrum disorder (ASD) comorbidity. The transgenic line MeCP2Tg1 was used for mimicking MECP2 duplication syndrome and showed autism-epilepsy co-occurrence. Previous works suggested that the excitatory/inhibitory (E/I) imbalance is a potential common mechanism for both epilepsy and ASD. The projection neurons and parvalbumin (PV) interneurons account for the majority of E/I balance in the hippocampus. Therefore, we explored how structural changes of projection and PV+ neurons occur in the hippocampus of MeCP2Tg1 mice and whether these morphological changes contribute to epilepsy susceptibility.

METHODS

We used the interneuron Designer receptors exclusively activated by designer drugs mouse model to inhibit inhibitory neurons in the hippocampus to verify the epilepsy susceptibility of MeCP2Tg1 (FVB, an inbred strain named as sensitivity to Friend leukemia virus) mice. Electroencephalograms were recorded for the definition of seizure. We performed retro-orbital injection of virus in MeCP2Tg1 (FVB):CaMKIIα-Cre (C57BL/6) mice or MeCP2Tg1:PV-Cre (C57BL/6) mice and their littermate controls to specifically label projection and PV+ neurons for structural analysis.

RESULTS

Epilepsy susceptibility was increased in MeCP2Tg1 mice. There was a reduced number of PV neurons and reduced dendritic complexity in the hippocampus of MeCP2Tg1 mice. The dendritic complexity in MeCP2Tg1 mice was increased compared to wild-type mice, and total dendritic spine density in dentate gyrus of MeCP2Tg1 mice was also increased. Total dendritic spine density was increased in CA1 of MeCP2Tg1 mice.

SIGNIFICANCE

Overexpression of MeCP2 may disrupt crucial signaling pathways, resulting in decreased dendritic complexity of PV interneurons and increased dendritic spine density of projection neurons. This reciprocal modulation of excitatory and inhibitory neuronal structures associated with MeCP2 implies its significance as a potential target in the development of epilepsy and offers a novel perspective on the co-occurrence of autism and epilepsy.

X-Linked Epilepsies: A Narrative Review

X-linked epilepsies are a heterogeneous group of epileptic conditions, which often overlap with X-linked intellectual disability. To date, various X-linked genes responsible for epilepsy syndromes and/or developmental and epileptic encephalopathies have been recognized. The electro-clinical phenotype is well described for some genes in which epilepsy represents the core symptom, while less phenotypic details have been reported for other recently identified genes. In this review, we comprehensively describe the main features of both X-linked epileptic syndromes thoroughly characterized to date (PCDH19-related DEE, CDKL5-related DEE, MECP2-related disorders), forms of epilepsy related to X-linked neuronal migration disorders (e.g., ARX, DCX, FLNA) and DEEs associated with recently recognized genes (e.g., SLC9A6, SLC35A2, SYN1, ARHGEF9, ATP6AP2, IQSEC2, NEXMIF, PIGA, ALG13, FGF13, GRIA3, SMC1A). It is often difficult to suspect an X-linked mode of transmission in an epilepsy syndrome. Indeed, different models of X-linked inheritance and modifying factors, including epigenetic regulation and X-chromosome inactivation in females, may further complicate genotype-phenotype correlations. The purpose of this work is to provide an extensive and updated narrative review of X-linked epilepsies. This review could support clinicians in the genetic diagnosis and treatment of patients with epilepsy featuring X-linked inheritance.

MECP2-related disorders while gene-based therapies are on the horizon

The emergence of new genetic tools has led to the discovery of the genetic bases of many intellectual and developmental disabilities. This creates exciting opportunities for research and treatment development, and a few genetic disorders (e.g., spinal muscular atrophy) have recently been treated with gene-based therapies. MECP2 is found on the X chromosome and regulates the transcription of thousands of genes. Loss of MECP2 gene product leads to Rett Syndrome, a disease found primarily in females, and is characterized by developmental regression, motor dysfunction, midline hand stereotypies, autonomic nervous system dysfunction, epilepsy, scoliosis, and autistic-like behavior. Duplication of MECP2 causes MECP2 Duplication Syndrome (MDS). MDS is found mostly in males and presents with developmental delay, hypotonia, autistic features, refractory epilepsy, and recurrent respiratory infections. While these two disorders share several characteristics, their differences (e.g., affected sex, age of onset, genotype/phenotype correlations) are important to distinguish in the light of gene-based therapy because they require opposite solutions. This review explores the clinical features of both disorders and highlights these important clinical differences.

Exploring gastrointestinal health in MECP2 duplication syndrome

BACKGROUND

MECP2 duplication syndrome (MDS) is a rare neurogenetic syndrome caused by duplications of MECP2 at the Xq28 region. Although constipation and gastrointestinal reflux are reported in MDS, a comprehensive characterization of gastrointestinal health has not been fully explored.

METHODS

We conducted a parent survey to explore the characteristics of gastrointestinal health in individuals with MDS using a secure online registry and compared differences in gastrointestinal symptoms between individuals with MDS and those with Rett syndrome (RTT).

KEY RESULTS

One hundred six surveys were analyzed. Symptoms commonly associated with constipation occurred in 72% to 89% of MDS individuals. Eleven percent of MDS individuals underwent surgery for complications associated with constipation. We observed a bimodal distribution for gastroesophageal reflux disease (GERD) and gastrostomy feeding, with higher prevalence in 0-3 and >12-year-old MDS individuals. Constipation and GERD were significantly more common, and gas bloating was significantly less common in MDS than in RTT. Biliary tract disease requiring surgery was an unrecognized problem in 5% of MDS individuals. We determined that gastrointestinal problems in MDS individuals contribute to caretaker burden.

CONCLUSION AND INFERENCES

Our study is the first in-depth investigation that characterizes gastrointestinal health in MDS and enumerates differences in gastrointestinal symptoms between MDS and RTT. Strategies to reduce gastrointestinal symptoms will alleviate caregiver burden in MDS. Further studies are needed to examine the mechanisms that cause gastrointestinal problems in MDS.

How Families Manage the Complex Medical Needs of Their Children with MECP2 Duplication Syndrome

MECP2 duplication syndrome (MDS) is a rare, X-linked, neurodevelopmental disorder resulting from the duplication of the methyl-CpG-binding protein 2 (MECP2) gene. The clinical features of MDS include severe intellectual disability, global developmental delay, seizures, recurrent respiratory infections, and gastrointestinal problems. The aim of this qualitative study was to explore how the parents of children with MDS manage their child's seizures, recurrent respiratory infections, and gastrointestinal symptoms, and the impact on them as parents. The data were coded into three categories: (1) complex care needs in the home, (2) highly skilled caregivers, and (3) impact on caregivers and families. Complex 24 h care was required and parents developed complex skillsets to ensure that this was delivered well to their child. The provision of extensive complex medical care in the home had an impact on parent mental and physical health, family dynamics, and finances. This study captures the management of high-burden comorbidities in MDS at home. Investigations into how best to support caregiver wellbeing to reduce their stresses, whilst maintaining optimal child health and wellbeing, are needed.

Duplication within two regions distal to MECP2: clinical similarity with MECP2 duplication syndrome

BACKGROUND

X-linked methyl-CpG-binding protein 2 (MECP2) duplication syndrome is prevalent in approximately 1% of X-linked intellectual disabilities. Accumulating evidence has suggested that MECP2 is the causative gene of MECP2 duplication syndrome. We report a case of a 17-year-old boy with a 1.2 Mb duplication distal to MECP2 on chromosome Xq28. Although this region does not contain MECP2, the clinical features and course of the boy are remarkably similar to those observed in MECP2 duplication syndrome. Recently, case reports have described duplication in the region distal to, and not containing, MECP2. These regions have been classified as the K/L-mediated Xq28 duplication region and int22h1/int22h2-mediated Xq28 duplication region. The case reports also described signs similar to those of MECP2 duplication syndrome. To the best of our knowledge, ours is the first case to include these two regions.

CASE PRESENTATION

The boy presented with a mild to moderate regressive intellectual disability and progressive neurological disorder. He developed epilepsy at the age of 6 years and underwent a bilateral equinus foot surgery at 14 years of age because of the increasing spasticity in lower extremities since the age of 11. Intracranial findings showed hypoplasia of the corpus callosum, cerebellum, and brain stem; linear hyperintensity in the deep white matter; and decreased white matter capacity. During his childhood, he suffered from recurrent infection. However, genital problems, skin abnormalities and gastrointestinal manifestations (gastroesophageal reflux) were not observed.

CONCLUSIONS

Cases in which duplication was observed in the region of Xq28 that does not include MECP2 also showed symptoms similar to those of MECP2 duplication syndrome. We compared four pathologies: MECP2 duplication syndrome with minimal regions, duplication within the two distal regions without MECP2, and our case including both regions. Our results suggest that MECP2 alone may not explain all symptoms of duplication in the distal part of Xq28.

Assessing the Burden on Caregivers of MECP2 Duplication Syndrome

BACKGROUND

MECP2 duplication syndrome (MDS) is a rare neurogenetic disorder characterized by severe neurodevelopmental disorder, refractory epilepsy, recurrent infections, and functional gastrointestinal problems. Because of the significant clinical problems and lifelong disability of children with this disorder we hypothesized that the burden on parents/caregivers of these children is significant. However, there are no reports of the impact on caregivers of individuals with MDS.

METHODS

We developed and validated a burden scale to investigate the challenges of caregivers of children and adults with MDS and identified factors contributing to the burden on caregivers. We developed a Health Insurance Portability and Accountability Act-compliant patient registry for families with MDS and delivered caregiver burden survey through the registry.

RESULTS

Of 237 completed surveys, 101 were eligible for the study. We identified increased levels of self-perceived anxiety, depression, and emotional exhaustion in caregivers that correlated with higher burden scores. Epilepsy was the only clinical feature that caused a higher burden in caregivers of individuals with MDS. In addition, a higher burden was found in Hispanic caregivers. The duration of care negatively correlated with burden score.

CONCLUSIONS

This is the first study to investigate the burden on caregivers of individuals with MDS and identify several factors contributing to increased burden. Addressing these concerns has the potential to improve the health of individuals with MDS and contribute to the well-being of their caretakers.

Epigenetic genes and epilepsy - emerging mechanisms and clinical applications

An increasing number of epilepsies are being attributed to variants in genes with epigenetic functions. The products of these genes include factors that regulate the structure and function of chromatin and the placing, reading and removal of epigenetic marks, as well as other epigenetic processes. In this Review, we provide an overview of the various epigenetic processes, structuring our discussion around five function-based categories: DNA methylation, histone modifications, histone-DNA crosstalk, non-coding RNAs and chromatin remodelling. We provide background information on each category, describing the general mechanism by which each process leads to altered gene expression. We also highlight key clinical and mechanistic aspects, providing examples of genes that strongly associate with epilepsy within each class. We consider the practical applications of these findings, including tissue-based and biofluid-based diagnostics and precision medicine-based treatments. We conclude that variants in epigenetic genes are increasingly found to be causally involved in the epilepsies, with implications for disease mechanisms, treatments and diagnostics.

Exploring the characteristics and most bothersome symptoms in MECP2 duplication syndrome to pave the path toward developing parent-oriented outcome measures

BACKGROUND

MECP2 Duplication Syndrome (MDS), resulting from the duplication of Xq28 region, including MECP2, is a rare disorder with a nascent understanding in clinical features and severity. Studies using antisense oligonucleotides revealed a broad phenotypic rescue in transgenic mice. With human clinical trials on the horizon, there is a need to develop clinical outcome measures for MDS.

METHODS

We surveyed caregivers of MDS individuals to explore the frequency and severity of MDS clinical features, and identify the most meaningful symptoms/domains that need to be included in the outcome measure scales.

RESULTS

A total of 101 responses were eligible for the survey. The top six most meaningful symptoms to caregivers in descending order included epilepsy, gross motor, fine motor, communication, infection, and constipation problems. Epilepsy was present in 58.4% of the subjects and 75% were drug-resistant, Furthermore, ~12% required intensive care unit (ICU) admission. Infections were present in 55% of the subjects, and one-fourth of them required ICU admission. Constipation was present in ~85% of the subjects and one-third required enemas/suppositories.

CONCLUSION

Our study is one of the largest cohorts conducted on MDS individuals characterizing the frequency and severity of MDS symptoms. Additionally, these study results will contribute to establishing a foundation to develop parent-reported outcomes in MDS.

Medical Comorbidities in MECP2 Duplication Syndrome: Results from the International MECP2 Duplication Database

Since the discovery of MECP2 duplication syndrome (MDS) in 1999, efforts to characterise this disorder have been limited by a lack of large datasets, with small case series often favouring the reporting of certain conditions over others. This study is the largest to date, featuring 134 males and 20 females, ascertained from the international MECP2 Duplication Database (MDBase). We report a higher frequency of pneumonia, bronchitis, bronchiolitis, gastroesophageal reflux and slow gut motility in males compared to females. We further examine the prevalence of other medical comorbidities such as epilepsy, gastrointestinal problems, feeding difficulties, scoliosis, bone fractures, sleep apnoea, autonomic disturbance and decreased pain sensitivity. A novel feature of urinary retention is reported and requires further investigation. Further research is required to understand the developmental trajectory of this disorder and to examine the context of these medical comorbidities in a quality of life framework.

A brief history of MECP2 duplication syndrome: 20-years of clinical understanding

MECP2 duplication syndrome (MDS) is a rare, X-linked, neurodevelopmental disorder caused by a duplication of the methyl-CpG-binding protein 2 (MECP2) gene-a gene in which loss-of-function mutations lead to Rett syndrome (RTT). MDS has an estimated live birth prevalence in males of 1/150,000. The key features of MDS include intellectual disability, developmental delay, hypotonia, seizures, recurrent respiratory infections, gastrointestinal problems, behavioural features of autism and dysmorphic features-although these comorbidities are not yet understood with sufficient granularity. This review has covered the past two decades of MDS case studies and series since the discovery of the disorder in 1999. After comprehensively reviewing the reported characteristics, this review has identified areas of limited knowledge that we recommend may be addressed by better phenotyping this disorder through an international data collection. This endeavour would also serve to delineate the clinical overlap between MDS and RTT.

Sleep Disorders in Rett Syndrome and Rett-Related Disorders: A Narrative Review

Rett Syndrome (RTT) is a rare and severe X-linked developmental brain disorder that occurs primarily in females, with a ratio of 1:10.000. De novo mutations in the Methyl-CpG Binding protein 2 (MECP2) gene on the long arm of X chromosome are responsible for more than 95% cases of classical Rett. In the remaining cases (atypical Rett), other genes are involved such as the cyclin-dependent kinase-like 5 (CDKL5) and the forkhead box G1 (FOXG1). Duplications of the MECP2 locus cause MECP2 duplication syndrome (MDS) which concerns about 1% of male patients with intellectual disability. Sleep disorders are common in individuals with intellectual disability, while the prevalence in children is between 16 and 42%. Over 80% of individuals affected by RTT show sleep problems, with a higher prevalence in the first 7 years of life and some degree of variability in correlation to age and genotype. Abnormalities in circadian rhythm and loss of glutamate homeostasis play a key role in the development of these disorders. Sleep disorders, epilepsy, gastrointestinal problems characterize CDKL5 Deficiency Disorder (CDD). Sleep impairment is an area of overlap between RTT and MECP2 duplication syndrome along with epilepsy, regression and others. Sleep dysfunction and epilepsy are deeply linked. Sleep deprivation could be an aggravating factor of epilepsy and anti-comitial therapy could interfere in sleep structure. Epilepsy prevalence in atypical Rett syndrome with severe clinical phenotype is higher than in classical Rett syndrome. However, RTT present a significant lifetime risk of epilepsy too. Sleep disturbances impact on child's development and patients' families and the evidence for its management is still limited. The aim of this review is to analyze pathophysiology, clinical features, the impact on other comorbidities and the management of sleep disorders in Rett syndrome and Rett-related syndrome.

MECP2 duplication syndrome: The electroclinical features of a case with long-term evolution

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A longitudinal spectrum of electroclinical features can be defined in MECP2 duplication syndrome (MDS).

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Burst suppression pattern is a new finding in MDS, appearing in later stages of disease.

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Sleep study in MDS may provide further information on disease progression.

MECP2 duplication syndrome (MDS) is a rare and severe neurodevelopmental disorder frequently associated with epilepsy. Different seizure types and electroencephalographic (EEG) patterns were described in patients with MDS, although it lacks a specific phenotype.

We report on an adult patient with long-term epilepsy showing an evolution of the EEG pattern that progressively changed into burst suppression (BS) during sleep. As BS has not been previously reported in MDS, this report expands the neurophysiological phenotype of MDS and further suggest the possible occurrence of a longitudinal spectrum of seizure types and EEG patterns in MDS.

Molecular and clinical insights into complex genomic rearrangements related to MECP2 duplication syndrome

MECP2 duplication syndrome (MDS) is caused by copy number variation (CNV) spanning the MECP2 gene at Xq28 and is a major cause of intellectual disability (ID) in males. Herein, we describe two unrelated males harboring non-recurrent complex Xq28 rearrangements associated with MDS. Copy number gains were initially detected by quantitative real-time polymerase chain reaction and further delineated by high-resolution array comparative genomic hybridization, familial segregation, expression analysis and X-chromosome inactivation (XCI) evaluation in a carrier mother. SNVs within the rearrangements and/or fluorescent in situ hybridization (FISH) were used to assess the parental origin of the rearrangements. Patient 1 exhibited an intrachromosomal rearrangement, whose structure is consistent with a triplicated segment presumably embedded in an inverted orientation between two duplicated sequences (DUP-TRP/INV-DUP). The rearrangement was inherited from the carrier mother, who exhibits extreme XCI skewing and subtle psychiatric symptoms. Patient 2 presented a de novo (X;Y) unbalanced translocation resulting in duplication of Xq28 and deletion of Yp, originated in the paternal gametogenesis. Neurodevelopmental trajectory and non-neurological symptoms were consistent with previous reports, with the exception of cerebellar vermis hypoplasia in patient 2. Although both patients share the core MDS phenotype, patient 1 showed MECP2 transcript levels in blood similar to controls. Understanding the molecular mechanisms related to MDS is essential for designing targeted therapeutic strategies.

Electroclinical Features in MECP2 Duplication Syndrome: Pediatric Case Series

OBJECTIVE

MECP2 duplication syndrome (MECP2DS) is an x-linked recessive syndrome characterized by infantile hypotonia, severe neurodevelopmental delay, intellectual disability, progressive spasticity, recurrent infections, and seizures. More than 50% of cases have been associated with epilepsy. Seizure semiology and electroencephalogram (EEG) findings in these patients are poorly described.

METHODS

In this case series, the authors describe the electroclinical features of children with MECP2DS presenting to their institution. In addition, they reviewed seizure types and therapies used.

RESULTS

Eight out of 9 patients with MECP2DS developed epilepsy, with 56% having normal initial EEG. Generalized slowing with generalized and focal/multifocal discharges was the most common EEG pattern which is consistent with prior studies. Atonic seizure was the most common semiology. Majority were pharmacoresistant (63%).

CONCLUSION

The goal of this case series is to better define the clinical and electrophysiological aspects of the epilepsy associated with MECP2 duplication syndrome and provide practical guidance regarding management.

Hip Displacement in MECP2 Disorders: Prevalence and Risk Factors

BACKGROUND

Methyl-CpG binding protein 2 (MECP2) disorders, including Rett syndrome and MECP2 duplication syndrome, are typified by profound intellectual disability, spasticity, and decline in gross motor function. Unlike scoliosis, linked to disease severity, little has been reported regarding the hip. The aim of this study was to report the prevalence and risk factors of hip displacement (HD) in MECP2 disorders.

METHODS

This was a retrospective, comparative study. Children with a genetically confirmed MECP2 disorder were included. The primary outcome measure was the prevalence of HD (migration percentage>30%). Secondary outcomes included age at HD onset, ambulatory status, presence of clinically relevant scoliosis, genetic severity, presence of seizures, and associated comorbidities. Analysis of proportions of categorical variables was performed using χ2 testing (P=0.05).

RESULTS

Fifty-six patients (54 Rett syndrome and 2 MECP2 duplication syndrome), diagnosed at 6.6 (SD: 4.7) years, met the inclusion criteria. The prevalence of HD was 36% [onset, 7.7 (SD: 3.8) y]. Risk factors for HD were nonwalker status (P=0.04), scoliosis (P=0.001), and refractory epilepsy (P=0.04).

CONCLUSIONS

The prevalence of HD in MECP2 disorders is comparable to cerebral palsy, associated with proxy measures of disease severity. These results can be used to develop hip surveillance programs for MECP2 disorders, allowing for timely management.

LEVEL OF EVIDENCE

Level III.

MECP2-Related Disorders in Males

Methyl CpG binding protein 2 (MECP2) is located at Xq28 and is a multifunctional gene with ubiquitous expression. Loss-of-function mutations in MECP2 are associated with Rett syndrome (RTT), which is a well-characterized disorder that affects mainly females. In boys, however, mutations in MECP2 can generate a wide spectrum of clinical presentations that range from mild intellectual impairment to severe neonatal encephalopathy and premature death. Thus, males can be more difficult to classify and diagnose than classical RTT females. In addition, there are some variants of unknown significance in MECP2, which further complicate the diagnosis of these children. Conversely, the entire duplication of the MECP2 gene is related to MECP2 duplication syndrome (MDS). Unlike in RTT, in MDS, males are predominantly affected. Usually, the duplication is inherited from an apparently asymptomatic carrier mother. Both syndromes share some characteristics, but also differ in some aspects regarding the clinical picture and evolution. In the following review, we present a thorough description of the different types of MECP2 variants and alterations that can be found in males, and explore several genotype-phenotype correlations, although there is still a lot to understand.

Genomic Investigation of Infantile and Childhood Epileptic Encephalopathies in Kazakhstan: An Urgent Priority

Objectives: Infantile and childhood epileptic encephalopathies are a group of severe epilepsies that begin within the first year of life and often portend increased morbidity. Many of them are genetically determined. The medical strategy for their management depends on the genetic cause. There are no facilities for genetic testing of children in Kazakhstan but we have a collection of data with already defined genes responsible for clinical presentations.

Methods: We analyzed children with epileptic encephalopathies that began in the first 3 years of life and were accompanied by a delay/arrest of intellectual development, in the absence of structural changes in the brain. Such patients were recommended to undergo genetic testing using epileptic genetic panels in laboratories in different countries.

Results: We observed 350 infants with clinical presentation of epileptic encephalopathies. 4.3% of them followed our recommendations and underwent genetic testing privately. In total 12/15 children became eligible for targeted treatment, 3/15 were likely to have non-epileptic stereotypies/movements, 2/15 were unlikely to respond to any therapy and all had a high chance of intellectual disability, behavioral and social communication disorders.

Conclusion: The genetic results of 15/350 (4.3% of patients) have demonstrated the potential and enormous impact from gene panel analysis in management of epileptic encephalopathy. Availability of genetic testing within the country will improve management of children with genetic epilepsies and help to create a local database of pathogenic variants.

Reviewing Evidence for the Relationship of EEG Abnormalities and RTT Phenotype Paralleled by Insights from Animal Studies

Rett syndrome (RTT) is a rare neurodevelopmental disorder that is usually caused by mutations of the MECP2 gene. Patients with RTT suffer from severe deficits in motor, perceptual and cognitive domains. Electroencephalogram (EEG) has provided useful information to clinicians and scientists, from the very first descriptions of RTT, and yet no reliable neurophysiological biomarkers related to the pathophysiology of the disorder or symptom severity have been identified to date. To identify consistently observed and potentially informative EEG characteristics of RTT pathophysiology, and ascertain areas most worthy of further systematic investigation, here we review the literature for EEG abnormalities reported in patients with RTT and in its disease models. While pointing to some promising potential EEG biomarkers of RTT, our review identify areas of need to realize the potential of EEG including (1) quantitative investigation of promising clinical-EEG observations in RTT, e.g., shift of mu rhythm frequency and EEG during sleep; (2) closer alignment of approaches between patients with RTT and its animal models to strengthen the translational significance of the work (e.g., EEG measurements and behavioral states); (3) establishment of large-scale consortium research, to provide adequate Ns to investigate age and genotype effects.

Early diagnosis of MECP2 duplication syndrome: Insights from a nationwide survey in Japan

This study aimed to elucidate the clinical characteristics of MECP2 duplication syndrome (MDS), particularly at initial presentation, and to provide clinical clues for the early diagnosis of this condition. We conducted a nationwide survey for MDS by sending questionnaires to 575 hospitals where board-certified pediatric neurologists were working and 195 residential hospitals for persons with severe motor and intellectual disabilities in Japan. This survey found 65 cases of MDS, and clinical data of 24 cases in which the diagnosis was genetically confirmed were analyzed. More than half of the patients (52%) had visited a hospital at least once during infancy due to symptoms associated with MDS, with a median age at the initial visit of 7 months. The symptoms that were frequently prevalent at the first visit were facial dysmorphic features, hypotonia, motor developmental delay, and recurrent infections. Dysmorphic features included small mouth, tented upper lip, tapered fingers, and hypertelorism. Other symptoms, including epilepsy, intellectual disabilities, autistic features, stereotypic movements, and gastrointestinal problems, generally appeared later with age. Some symptoms of MDS were found to be age-dependent and may not be noticeable in infancy. Recognition of these clinical characteristics may facilitate the early diagnosis and proper treatment of patients with MDS, improve their long-term outcomes, and help adapt appropriate genetic counseling.

Identification of hsa-miR-1275 as a Novel Biomarker Targeting MECP2 for Human Epilepsy of Unknown Etiology

Epilepsy affects around 70 million people worldwide, with a 65% rate of unknown etiology. This rate is known as epilepsy of unknown etiology (EUE). Dysregulation of microRNAs (miRNAs) is recognized to contribute to mental disorders, including epilepsy. However, miRNA dysregulation is poorly understood in EUE. Here, we conducted miRNA expression profiling of EUE by microarray technology and identified 57 pathogenic changed miRNAs with significance. The data and bioinformatic analysis results indicated that among these miRNAs, hsa-microRNA (miR)-1275 was highly associated with neurological disorders. Subsequently, new samples of serum and cerebrospinal fluid were collected for validation of hsa-miR-1275 expression by TaqMan assays. Results show that hsa-miR-1275 in serums of EUE were increased significantly, but in cerebrospinal fluid, the miRNA was decreased. Moreover, the MECP2 gene was selected as a hsa-miR-1275 target based on target prediction tools and gene ontology analysis. Validation of in vitro tests proved that MECP2 expression was specifically inhibited by hsa-miR-1275. Additionally, overexpression of hsa-miR-1275 can elevate expression of nuclear factor κB (NF-κB) and promote cell apoptosis. Taken together, hsa-miR-1275 might represent a novel biomarker targeting MECP2 for human EUE.

Phenotypic features in MECP2 duplication syndrome: Effects of age

BACKGROUND

MECP2 Duplication syndrome (MDS) is a rare X-linked genomic disorder that is caused by interstitial chromosomal duplications at Xq28 encompassing the MECP2 gene. Although phenotypic features in MDS have been described, there is a limited understanding of the range of severity of these features, and how they evolve with age.

METHODS

The cross-sectional results of N = 69 participants (ages 6 months-33 years) enrolled in a natural history study of MDS are presented. Clinical severity was assessed using a clinician-report measure as well as a parent-report measure. Data was also gathered related to the top 3 concerns of parents as selected from the most salient symptoms related to MDS. The Child Health Questionnaire was also utilized to obtain parental reports of each child's quality of life to establish disease burden.

RESULTS

The results of linear regression from the clinician-reported measure show that overall clinical severity scores, motor dysfunction, and functional skills are significantly worse with increasing age. Top concerns rated by parents included lack of effective communication, abnormal walking/balance issues, constipation, and seizures. Higher levels of clinical severity were also related to lower physical health quality of life scores as reported by parents.

CONCLUSIONS

The data suggest that increasing levels of clinical severity are noted with older age, and this is primarily attributable to motor dysfunction, and functional skills. The results provide an important foundation for creating an MDS-specific severity scale highlighting the most important domains to target for treatment trials and will help clinicians and researchers define clinically meaningful changes.

Advances in understanding of Rett syndrome and MECP2 duplication syndrome: prospects for future therapies

The X-linked gene encoding MECP2 is involved in two severe and complex neurodevelopmental disorders. Loss of function of the MeCP2 protein underlies Rett syndrome, whereas duplications of the MECP2 locus cause MECP2 duplication syndrome. Research on the mechanisms by which MeCP2 exerts effects on gene expression in neurons, studies of animal models bearing different disease-causing mutations, and more in-depth observations of clinical presentations have clarified some issues even as they have raised further questions. Yet there is enough evidence so far to suggest possible approaches to therapy for these two diseases that could go beyond attempting to address specific signs and symptoms (of which there are many) and instead target the pathophysiology underlying MECP2 disorders. Further work could bring antisense oligonucleotides, deep brain stimulation, and gene therapy into the clinic within the next decade or so.

Rodent genetic models of neurodevelopmental disorders and epilepsy

Neurodevelopmental disorders (NDDs) are characterised by cognitive, social and motor deficits and are highly comorbid with intractable epilepsies. Through advances in genetic sequencing technologies a vast number of genes have been implicated in NDDs. State-of-the-art gene-editing techniques have led to the generation of hundreds of mouse models of NDDs. As an example, rodent models of Rett and Dravet syndromes as well as the syndromes caused by mutations in CDKL5 and Syngap1 display cognitive deficits in conjunction with seizure phenotypes. These models allow researchers to understand the underlying mechanisms as well as develop novel treatment strategies that can potentially be translated to the clinic. Furthermore, it may be possible to gain insights into the contribution of epilepsy to the progression of cognitive, social and motor phenotypes in NDDs.