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Genes Jul 2021Progress in the clinical application of next-generation-sequencing-based techniques has resulted in a dramatic increase in the recognized genetic heterogeneity of the... (Review)
Review
INTRODUCTION
Progress in the clinical application of next-generation-sequencing-based techniques has resulted in a dramatic increase in the recognized genetic heterogeneity of the Rett syndrome spectrum (RSS). Our awareness of the considerable overlap with pediatric-onset epilepsies and epileptic/developmental encephalopathies (EE/DE) genes is also growing, and the presence of variable clinical features inside a general frame of commonalities has drawn renewed attention into deep phenotyping.
METHODS
We decided to review the medical literature on atypical Rett syndrome and "Rett-like" phenotypes, with special emphasis on described cases with pediatric-onset epilepsies and/or EE-DE, evaluating Neul's criteria for Rett syndrome and associated movement disorders and notable stereotypies.
RESULTS
"Rett-like" features were described in syndromic and non-syndromic monogenic epilepsy- and DE/EE-related genes, in "intellectual disability plus epilepsy"-related genes and in neurodegenerative disorders. Additionally, prominent stereotypies can be observed in monogenic complex neurodevelopmental disorders featuring epilepsy with or without autistic features outside of the RSS.
CONCLUSIONS
Patients share a complex neurodevelopmental and neurological phenotype (developmental delay, movement disorder) with impaired gait, abnormal tone and hand stereotypies. However, the presence and characteristics of regression and loss of language and functional hand use can differ. Finally, the frequency of additional supportive criteria and their distribution also vary widely.
Topics: Brain Diseases; Epilepsy; Humans; Male; Rett Syndrome
PubMed: 34440332
DOI: 10.3390/genes12081157 -
Andes Pediatrica : Revista Chilena de... Jan 2023Rett syndrome (RS) is a rare neurodevelopmental disorder first described in 1966. It is characterized by the arrest and regression of intellectual, motor, and...
Rett syndrome (RS) is a rare neurodevelopmental disorder first described in 1966. It is characterized by the arrest and regression of intellectual, motor, and communicative developmental milestones, followed by the appearance of hand stereotypies after an apparently normal development period. Pathogenic variants in the MECP2 gene have been identified as a cause in most cases. The following review focuses on analyzing updated information regarding the medical and social aspects of RS globally, with a special emphasis of the situation in Chile. A multiple database search for updated information on RS was performed, selecting 68 articles published between 1995 and 2022, 56 on medical aspects, 11 on social aspects, and 1 on both. Additionally, information regarding certain social aspects was collected from government websites. Regarding medical aspects, the review focuses on RS' clinical features, diagnosis and classification, genetics, pathophysiology, and management. In relation to social aspects, the review presents the psychic and emotional stress that RS can cause on affected families based on international studies and, lastly, the opportunities and tools available to Chilean patients. RS is a complex disorder affecting multiple organ systems. Its management requires a multidisciplinary approach, having an important psychological and socioeconomic impact on the family. In Chile, Laws N° 20,422 and 21,292, the National Disability Service, and the creation of the "Caminamos por Ellas y Ellos" (We Walk for Them) foundation are positive milestones met in the journey of supporting these families.
Topics: Humans; Rett Syndrome; Chile; Communication
PubMed: 37906876
DOI: 10.32641/andespediatr.v94i1.4014 -
Nature Apr 2021Mutations in the X-linked gene MECP2 cause Rett syndrome, a progressive neurological disorder in which children develop normally for the first one or two years of life...
Mutations in the X-linked gene MECP2 cause Rett syndrome, a progressive neurological disorder in which children develop normally for the first one or two years of life before experiencing profound motor and cognitive decline. At present there are no effective treatments for Rett syndrome, but we hypothesized that using the period of normal development to strengthen motor and memory skills might confer some benefit. Here we find, using a mouse model of Rett syndrome, that intensive training beginning in the presymptomatic period dramatically improves the performance of specific motor and memory tasks, and significantly delays the onset of symptoms. These benefits are not observed when the training begins after symptom onset. Markers of neuronal activity and chemogenetic manipulation reveal that task-specific neurons that are repeatedly activated during training develop more dendritic arbors and have better neurophysiological responses than those in untrained animals, thereby enhancing their functionality and delaying symptom onset. These results provide a rationale for genetic screening of newborns for Rett syndrome, as presymptomatic intervention might mitigate symptoms or delay their onset. Similar strategies should be studied for other childhood neurological disorders.
Topics: Animals; Biomedical Enhancement; Disease Models, Animal; Electrophysiology; Female; Male; Mice; Morris Water Maze Test; Neurons; Prodromal Symptoms; Psychomotor Performance; Rett Syndrome; Rotarod Performance Test; Spatial Learning; Time Factors
PubMed: 33762729
DOI: 10.1038/s41586-021-03369-7 -
Frontiers in Genetics 2021
PubMed: 34539761
DOI: 10.3389/fgene.2021.755076 -
Neurotherapeutics : the Journal of the... Jan 2021There are multiple disorders of neurodevelopment that present with co-occurring sleep disturbances. Many of these neurodevelopmental disorders (NDD) include sleep... (Review)
Review
There are multiple disorders of neurodevelopment that present with co-occurring sleep disturbances. Many of these neurodevelopmental disorders (NDD) include sleep disturbances in their diagnostic criteria. Neurobiological, genetic, and environmental factors overlap to cause different sleep disorders in individuals with NDD. Caregivers often present reporting either insomnia or hypersomnia, and based on the clinical history and findings from diagnostic tests, an appropriate diagnosis can be made. It is crucial that clinicians understand the different presentations of sleep disturbances in individuals with NDD.
Topics: Humans; Neurodevelopmental Disorders; Sleep; Sleep Wake Disorders
PubMed: 33403472
DOI: 10.1007/s13311-020-00982-8 -
Human Genomics Sep 2023Rett syndrome (RTT) is a neurodevelopmental disorder mainly caused by mutations in the methyl-CpG-binding protein 2 gene (MECP2). MeCP2 is a multi-functional protein...
BACKGROUND
Rett syndrome (RTT) is a neurodevelopmental disorder mainly caused by mutations in the methyl-CpG-binding protein 2 gene (MECP2). MeCP2 is a multi-functional protein involved in many cellular processes, but the mechanisms by which its dysfunction causes disease are not fully understood. The duplication of the MECP2 gene causes a distinct disorder called MECP2 duplication syndrome (MDS), highlighting the importance of tightly regulating its dosage for proper cellular function. Additionally, some patients with mutations in genes other than MECP2 exhibit phenotypic similarities with RTT, indicating that these genes may also play a role in similar cellular functions. The purpose of this study was to characterise the molecular alterations in patients with RTT in order to identify potential biomarkers or therapeutic targets for this disorder.
METHODS
We used a combination of transcriptomics (RNAseq) and proteomics (TMT mass spectrometry) to characterise the expression patterns in fibroblast cell lines from 22 patients with RTT and detected mutation in MECP2, 15 patients with MDS, 12 patients with RTT-like phenotypes and 13 healthy controls. Transcriptomics and proteomics data were used to identify differentially expressed genes at both RNA and protein levels, which were further inspected via enrichment and upstream regulator analyses and compared to find shared features in patients with RTT.
RESULTS
We identified molecular alterations in cellular functions and pathways that may contribute to the disease phenotype in patients with RTT, such as deregulated cytoskeletal components, vesicular transport elements, ribosomal subunits and mRNA processing machinery. We also compared RTT expression profiles with those of MDS seeking changes in opposite directions that could lead to the identification of MeCP2 direct targets. Some of the deregulated transcripts and proteins were consistently affected in patients with RTT-like phenotypes, revealing potentially relevant molecular processes in patients with overlapping traits and different genetic aetiology.
CONCLUSIONS
The integration of data in a multi-omics analysis has helped to interpret the molecular consequences of MECP2 dysfunction, contributing to the characterisation of the molecular landscape in patients with RTT. The comparison with MDS provides knowledge of MeCP2 direct targets, whilst the correlation with RTT-like phenotypes highlights processes potentially contributing to the pathomechanism leading these disorders.
Topics: Humans; Rett Syndrome; Multiomics; Mental Retardation, X-Linked; RNA Processing, Post-Transcriptional
PubMed: 37710353
DOI: 10.1186/s40246-023-00532-1 -
Frontiers in Genetics 2024The emergence of new genetic tools has led to the discovery of the genetic bases of many intellectual and developmental disabilities. This creates exciting opportunities... (Review)
Review
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. is found on the X chromosome and regulates the transcription of thousands of genes. Loss of 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 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.
PubMed: 38410154
DOI: 10.3389/fgene.2024.1332469 -
The Lancet. Diabetes & Endocrinology Aug 2023Identification of genetic causes of central precocious puberty have revealed epigenetic mechanisms as regulators of human pubertal timing. MECP2, an X-linked gene,...
BACKGROUND
Identification of genetic causes of central precocious puberty have revealed epigenetic mechanisms as regulators of human pubertal timing. MECP2, an X-linked gene, encodes a chromatin-associated protein with a role in gene transcription. MECP2 loss-of-function mutations usually cause Rett syndrome, a severe neurodevelopmental disorder. Early pubertal development has been shown in several patients with Rett syndrome. The aim of this study was to explore whether MECP2 variants are associated with an idiopathic central precocious puberty phenotype.
METHODS
In this translational cohort study, participants were recruited from seven tertiary centres from five countries (Brazil, Spain, France, the USA, and the UK). Patients with idiopathic central precocious puberty were investigated for rare potentially damaging variants in the MECP2 gene, to assess whether MECP2 might contribute to the cause of central precocious puberty. Inclusion criteria were the development of progressive pubertal signs (Tanner stage 2) before the age of 8 years in girls and 9 years in boys and basal or GnRH-stimulated LH pubertal concentrations. Exclusion criteria were the diagnosis of peripheral precocious puberty and the presence of any recognised cause of central precocious puberty (CNS lesions, known monogenic causes, genetic syndromes, or early exposure to sex steroids). All patients included were followed up at the outpatient clinics of participating academic centres. We used high-throughput sequencing in 133 patients and Sanger sequencing of MECP2 in an additional 271 patients. Hypothalamic expression of Mecp2 and colocalisation with GnRH neurons were determined in mice to show expression of Mecp2 in key nuclei related to pubertal timing regulation.
FINDINGS
Between Jun 15, 2020, and Jun 15, 2022, 404 patients with idiopathic central precocious puberty (383 [95%] girls and 21 [5%] boys; 261 [65%] sporadic cases and 143 [35%] familial cases from 134 unrelated families) were enrolled and assessed. We identified three rare heterozygous likely damaging coding variants in MECP2 in five girls: a de novo missense variant (Arg97Cys) in two monozygotic twin sisters with central precocious puberty and microcephaly; a de novo missense variant (Ser176Arg) in one girl with sporadic central precocious puberty, obesity, and autism; and an insertion (Ala6_Ala8dup) in two unrelated girls with sporadic central precocious puberty. Additionally, we identified one rare heterozygous 3'UTR MECP2 insertion (36_37insT) in two unrelated girls with sporadic central precocious puberty. None of them manifested Rett syndrome. Mecp2 protein colocalised with GnRH expression in hypothalamic nuclei responsible for GnRH regulation in mice.
INTERPRETATION
We identified rare MECP2 variants in girls with central precocious puberty, with or without mild neurodevelopmental abnormalities. MECP2 might have a role in the hypothalamic control of human pubertal timing, adding to the evidence of involvement of epigenetic and genetic mechanisms in this crucial biological process.
FUNDING
Fundação de Amparo à Pesquisa do Estado de São Paulo, Conselho Nacional de Desenvolvimento Científico e Tecnológico, and the Wellcome Trust.
Topics: Animals; Child; Female; Humans; Male; Mice; Brazil; Cohort Studies; Follicle Stimulating Hormone; Gonadotropin-Releasing Hormone; Luteinizing Hormone; Puberty, Precocious; Rett Syndrome
PubMed: 37385287
DOI: 10.1016/S2213-8587(23)00131-6 -
Cell Reports Dec 2023A unique signature of neurons is the high expression of the longest genes in the genome. These genes have essential neuronal functions, and disruption of their...
A unique signature of neurons is the high expression of the longest genes in the genome. These genes have essential neuronal functions, and disruption of their expression has been implicated in neurological disorders. DNA topoisomerases resolve DNA topological constraints and facilitate neuronal long gene expression. Conversely, the Rett syndrome protein, methyl-CpG-binding protein 2 (MeCP2), can transcriptionally repress long genes. How these factors regulate long genes is not well understood, and whether they interact is not known. Here, we identify and map a functional interaction between MeCP2 and topoisomerase IIβ (TOP2β) in mouse neurons. We profile neuronal TOP2β activity genome wide, detecting enrichment at regulatory regions and gene bodies of long genes, including MeCP2-regulated genes. We show that loss and overexpression of MeCP2 alter TOP2β activity at MeCP2-regulated genes. These findings uncover a mechanism of TOP2β inhibition by MeCP2 in neurons and implicate TOP2β dysregulation in disorders caused by MeCP2 disruption.
Topics: Animals; Mice; Methyl-CpG-Binding Protein 2; Neurons; Rett Syndrome
PubMed: 38096051
DOI: 10.1016/j.celrep.2023.113538 -
Brain and Behavior Jul 2022The onset of severe, drug-resistant seizures in early childhood is characteristic of the rare epileptic disorders Lennox-Gastaut syndrome (LGS), Dravet syndrome (DS),... (Review)
Review
INTRODUCTION
The onset of severe, drug-resistant seizures in early childhood is characteristic of the rare epileptic disorders Lennox-Gastaut syndrome (LGS), Dravet syndrome (DS), and CDKL5 deficiency disorder (CDD) and is frequently observed in the rare genetic conditions tuberous sclerosis complex (TSC) and Rett syndrome (RTT). High-quality treatment guidelines are needed for optimal management of these conditions. This review aimed to assess content, availability, and development of treatment guidelines for these disorders in the Nordics region (Denmark, Finland, Iceland, Norway, and Sweden).
METHODS
A targeted literature review (TLR) was therefore conducted in November/December 2020 by manually searching online rare disease and guideline databases in addition to relevant health technology assessment and regulatory agency websites to identify pharmacological treatment guidelines for DS, LGS, TSC, RTT, and CDD. Search terms for each disorder were translated to identify country-specific guidelines. Treatment recommendations, geographical focus, and guideline development methodology was extracted into a predetermined extraction grid.
RESULTS
Most of the 24 eligible guidelines identified (16/24; 66%) were specific to particular countries; Sweden was the most represented (7/24 [29%] guidelines), while no guidelines were identified for Iceland. Guideline development methodologies were heterogeneous, including systematic literature reviews/TLRs and expert consultation; several methodologies did not report details on the evidence sources used (7/24 [29%] guidelines). Treatment recommendation availability was variable across disorders, ranging from 126 treatment recommendations (LGS) to none (RTT, CDD).
CONCLUSION
Comprehensive, consensus-based treatment guidance developed via international collaboration within the Nordics region is necessary to optimize patient care in these five rare epileptic conditions.
Topics: Child, Preschool; Epilepsies, Myoclonic; Epilepsy; Epileptic Syndromes; Humans; Lennox Gastaut Syndrome; Rett Syndrome; Spasms, Infantile
PubMed: 35765698
DOI: 10.1002/brb3.2622