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Annual Review of Neuroscience Jul 2022Mounting evidence indicates that microglia, which are the resident immune cells of the brain, play critical roles in a diverse array of neurodevelopmental processes... (Review)
Review
Mounting evidence indicates that microglia, which are the resident immune cells of the brain, play critical roles in a diverse array of neurodevelopmental processes required for proper brain maturation and function. This evidence has ultimately led to growing speculation that microglial dysfunction may play a role in neurodevelopmental disorder (NDD) pathoetiology. In this review, we first provide an overview of how microglia mechanistically contribute to the sculpting of the developing brain and neuronal circuits. To provide an example of how disruption of microglial biology impacts NDD development, we also highlight emerging evidence that has linked microglial dysregulation to autism spectrum disorder pathogenesis. In recent years, there has been increasing interest in how the gut microbiome shapes microglial biology. In the last section of this review, we put a spotlight on this burgeoning area of microglial research and discuss how microbiota-dependent modulation of microglial biology is currently thought to influence NDD progression.
Topics: Autism Spectrum Disorder; Brain; Gastrointestinal Microbiome; Humans; Microglia; Neurodevelopmental Disorders
PubMed: 35436413
DOI: 10.1146/annurev-neuro-110920-023056 -
International Journal of Molecular... Sep 2021Methyl CpG binding protein 2 () is located at Xq28 and is a multifunctional gene with ubiquitous expression. Loss-of-function mutations in are associated with Rett... (Review)
Review
Methyl CpG binding protein 2 () is located at Xq28 and is a multifunctional gene with ubiquitous expression. Loss-of-function mutations in are associated with Rett syndrome (RTT), which is a well-characterized disorder that affects mainly females. In boys, however, mutations in 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 , which further complicate the diagnosis of these children. Conversely, the entire duplication of the gene is related to 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 variants and alterations that can be found in males, and explore several genotype-phenotype correlations, although there is still a lot to understand.
Topics: Brain Diseases; Cognitive Dysfunction; Genetic Association Studies; Genotype; Humans; Male; Mental Retardation, X-Linked; Methyl-CpG-Binding Protein 2; Mutation; Phenotype; Rett Syndrome
PubMed: 34502518
DOI: 10.3390/ijms22179610 -
International Journal of Molecular... Aug 2019Rett syndrome (RTT) is an early-onset neurodevelopmental disorder that primarily affects females, resulting in severe cognitive and physical disabilities, and is one of... (Review)
Review
Rett syndrome (RTT) is an early-onset neurodevelopmental disorder that primarily affects females, resulting in severe cognitive and physical disabilities, and is one of the most prevalent causes of intellectual disability in females. More than fifty years after the first publication on Rett syndrome, and almost two decades since the first report linking RTT to the gene, the research community's effort is focused on obtaining a better understanding of the genetics and the complex biology of RTT and Rett-like phenotypes without mutations. Herein, we review the current molecular genetic studies, which investigate the genetic causes of RTT or Rett-like phenotypes which overlap with other genetic disorders and document the swift evolution of the techniques and methodologies employed. This review also underlines the clinical and genetic heterogeneity of the Rett syndrome spectrum and provides an overview of the RTT-related genes described to date, many of which are involved in epigenetic gene regulation, neurotransmitter action or RNA transcription/translation. Finally, it discusses the importance of including both phenotypic and genetic diagnosis to provide proper genetic counselling from a patient's perspective and the appropriate treatment.
Topics: Animals; Gene Expression Regulation; Genetic Heterogeneity; Humans; Methyl-CpG-Binding Protein 2; Mutation; Rett Syndrome; Signal Transduction
PubMed: 31409060
DOI: 10.3390/ijms20163925 -
Systematic Reviews Jan 2023Rett syndrome is a rare, severe neurodevelopmental disorder. Almost all cases occur in girls, in association with spontaneous (non-inherited) mutations involving the... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Rett syndrome is a rare, severe neurodevelopmental disorder. Almost all cases occur in girls, in association with spontaneous (non-inherited) mutations involving the methyl-CpG-binding protein 2 gene located on the X chromosome. Diagnostic criteria for typical Rett syndrome require a period of regression, followed by recovery or stabilization, and fulfillment of all four main criteria (loss of purposeful hand skills, loss of spoken language, gait abnormalities, and stereotypic hand movements). Our objective was to estimate the prevalence of Rett syndrome in the general population, stratified by sex.
METHODS
We conducted a search of PubMed, Embase, Web of Science, Cochrane Library, LILACS, and LIVIVO to retrieve studies published in English between Jan. 1, 2000, and June 30, 2021. Pooled prevalence with a 95% confidence interval (CI) was estimated using a random-effects meta-analysis based on a generalized linear mixed model with a logit link.
RESULTS
Ten eligible studies were identified (all in females), with a combined sample size of 9.57 million women and 673 Rett syndrome cases. The pooled prevalence estimate (random effects) was 7.1 per 100,000 females (95% CI: 4.8, 10.5, heterogeneity p < 0.001). Despite greatly variable precision of estimation, all estimates were compatible with a prevalence range of approximately 5 to 10 cases per 100,000 females based on their respective 95% CIs.
CONCLUSION
These findings may facilitate planning of therapeutic trials in this indication in terms of target sample size and accrual times.
Topics: Humans; Female; Rett Syndrome; Methyl-CpG-Binding Protein 2; Prevalence; Mutation
PubMed: 36642718
DOI: 10.1186/s13643-023-02169-6 -
Neuropsychiatric Disease and Treatment 2022Rett syndrome (RTT) is a neurodevelopmental disorder caused predominantly by loss-of-function mutations in the gene (), which encodes the MeCP2 protein. RTT is a... (Review)
Review
Rett syndrome (RTT) is a neurodevelopmental disorder caused predominantly by loss-of-function mutations in the gene (), which encodes the MeCP2 protein. RTT is a -related disorder, along with duplication syndrome (MDS), caused by gain-of-function duplications of . Nearly two decades of research have advanced our knowledge of MeCP2 function in health and disease. The following review will discuss MeCP2 protein function and its dysregulation in the -related disorders RTT and MDS. This will include a discussion of the genetic underpinnings of these disorders, specifically how sporadic X-chromosome mutations arise and manifest in specific populations. We will then review current diagnostic guidelines and clinical manifestations of RTT and MDS. Next, we will delve into MeCP2 biology, describing the dual landscapes of methylated DNA and its reader MeCP2 across the neuronal genome as well as the function of MeCP2 as a transcriptional modulator. Following this, we will outline common mutations and genotype-phenotype correlations in both diseases, with particular focus on mutations associated with relatively mild disease in RTT. We will also summarize decades of disease modeling and resulting molecular, synaptic, and behavioral phenotypes associated with RTT and MDS. Finally, we list several therapeutics in the development pipeline for RTT and MDS and available evidence of their safety and efficacy.
PubMed: 36471747
DOI: 10.2147/NDT.S371483 -
Developmental Medicine and Child... Feb 2023Rett syndrome (RTT) is an X-linked neurogenetic disorder caused by mutations of the MECP2 (methyl-CpG-binding protein 2) gene. Over two decades of work established MeCP2... (Review)
Review
Rett syndrome (RTT) is an X-linked neurogenetic disorder caused by mutations of the MECP2 (methyl-CpG-binding protein 2) gene. Over two decades of work established MeCP2 as a protein with pivotal roles in the regulation of the epigenome, neuronal physiology, synaptic maintenance, and behaviour. Given the genetic aetiology of RTT and the proof of concept of its reversal in a mouse model, considerable efforts have been made to design therapeutic approaches to re-express MeCP2. By being at the forefront of the development of innovative gene therapies, research on RTT is of paramount importance for the treatment of monogenic neurological diseases. Here we discuss the recent advances and challenges of promising genetic strategies for the treatment of RTT including gene replacement therapies, gene/RNA editing strategies, and reactivation of the silenced X chromosome. WHAT THIS PAPER ADDS: Recent advances shed light on the promises of gene replacement therapy with new vectors designed to control the levels of MeCP2 expression. New developments in DNA/RNA editing approaches or reactivation of the silenced X chromosome open the possibility to re-express the native MeCP2 locus at endogenous levels. Current strategies still face limitations in transduction efficiency and future work is needed to improve brain delivery.
Topics: Mice; Animals; Humans; Rett Syndrome; Art Therapy; Methyl-CpG-Binding Protein 2; Brain; Mutation; Neurons
PubMed: 36056801
DOI: 10.1111/dmcn.15383 -
Contemporary Clinical Trials Mar 2022Rett syndrome (RTT) is a debilitating neurodevelopmental disorder with no approved treatments. Trofinetide is a synthetic analog of glycine-proline-glutamate, the... (Randomized Controlled Trial)
Randomized Controlled Trial
INTRODUCTION
Rett syndrome (RTT) is a debilitating neurodevelopmental disorder with no approved treatments. Trofinetide is a synthetic analog of glycine-proline-glutamate, the N-terminal tripeptide of insulin-like growth factor 1. In a phase 2, placebo-controlled trial in 82 females with RTT aged 5-15 years, a significant (p ≤ 0.042) improvement over placebo was observed with the highest trofinetide dose (200 mg/kg twice daily [BID]) on three measures: Rett Syndrome Behaviour Questionnaire (RSBQ), Clinical Global Impression-Improvement (CGI-I), and RTT-Clinician Domain Specific Concerns-Visual Analog Scale (RTT-DSC-VAS). Trofinetide was well tolerated at all doses (50, 100, and 200 mg/kg BID). A phase 3 trial utilizing disease-specific and novel scales was designed to investigate the efficacy and safety of trofinetide in girls and women with RTT.
METHODS
This 12-week, double-blind, randomized, placebo-controlled study (LAVENDER; NCT04181723) will evaluate trofinetide in 187 females, aged 5-20 years, with RTT. Co-primary endpoints are the RSBQ and CGI-I scales. Clinical domains of the CGI-I include communication, ambulation, hand use, seizures, attentiveness, and social (eye contact) and autonomic (breathing) aspects. Secondary endpoints will leverage four novel RTT-specific clinician ratings (derived from the RTT-DSC-VAS) of hand function, ambulation, ability to communicate, and verbal communication, and existing scales, to evaluate other core symptoms of RTT, quality of life and caregiver burden. A 40-week, open-label extension study will follow.
DISCUSSION
This study was designed using disease-specific scales optimized to demonstrate changes in core symptoms of RTT and may provide the first phase 3 data demonstrating drug efficacy in individuals with RTT.
TRIAL REGISTRATION
Clinicaltrials.govNCT04181723.
Topics: Adolescent; Child; Child, Preschool; Double-Blind Method; Female; Glutamates; Humans; Outcome Assessment, Health Care; Quality of Life; Rett Syndrome
PubMed: 35149233
DOI: 10.1016/j.cct.2022.106704 -
Genes Aug 2023Over the last 20 years, the understanding and natural history of Rett syndrome has advanced, but to date no cure has emerged, with multidisciplinary management being... (Review)
Review
Over the last 20 years, the understanding and natural history of Rett syndrome has advanced, but to date no cure has emerged, with multidisciplinary management being symptomatic and supportive. This study provides a comprehensive review of the clinical features, comorbidities and multidisciplinary management of a well-characterized cohort of females with classical Rett syndrome. We aim to improve awareness and understanding of Rett syndrome amongst pediatricians, pediatric subspecialists and allied health professionals to enable early diagnosis and a streamlined enrolment approach for future clinical trials. Rett syndrome, a complex X-linked condition, affecting mainly females, is due to pathogenic variants of the gene in most affected individuals. The Rett syndrome Multidisciplinary Management clinic at The Children's Hospital at Westmead, Sydney, Australia, was established in 2000. This retrospective analysis of individuals who attended the clinic from 2000 to 2020 was performed to identify the incidence and predicted age of onset of Rett syndrome related comorbidities, disease progression and to review management principles. Data collected included age of Rett syndrome diagnosis, genotype, clinical features and medical comorbidities, such as sleep disturbance, seizures, breathing irregularities, scoliosis, mobility, hand stereotypies, hand function, constipation, feeding ability, use of gastrostomy, communication skills, QTc prolongation, anthropometry, and bruxism. Analysis of 103 girls who fulfilled the clinical diagnostic criteria for classical Rett syndrome with a pathogenic variant of the gene showed a median age of diagnosis of 3 years. The most frequent variant was c.502 C>T.
Topics: Female; Humans; Child; Child, Preschool; Male; Rett Syndrome; Retrospective Studies; Scoliosis; Constipation; Seizures
PubMed: 37628658
DOI: 10.3390/genes14081607 -
Nature Medicine Jun 2023Rett syndrome is a rare, genetic neurodevelopmental disorder. Trofinetide is a synthetic analog of glycine-proline-glutamate, the N-terminal tripeptide of the... (Randomized Controlled Trial)
Randomized Controlled Trial
Rett syndrome is a rare, genetic neurodevelopmental disorder. Trofinetide is a synthetic analog of glycine-proline-glutamate, the N-terminal tripeptide of the insulin-like growth factor 1 protein, and has demonstrated clinical benefit in phase 2 studies in Rett syndrome. In this phase 3 study ( https://clinicaltrials.gov identifier NCT04181723 ), females with Rett syndrome received twice-daily oral trofinetide (n = 93) or placebo (n = 94) for 12 weeks. For the coprimary efficacy endpoints, least squares mean (LSM) change from baseline to week 12 in the Rett Syndrome Behaviour Questionnaire for trofinetide versus placebo was -4.9 versus -1.7 (P = 0.0175; Cohen's d effect size, 0.37), and LSM Clinical Global Impression-Improvement at week 12 was 3.5 versus 3.8 (P = 0.0030; effect size, 0.47). For the key secondary efficacy endpoint, LSM change from baseline to week 12 in the Communication and Symbolic Behavior Scales Developmental Profile Infant-Toddler Checklist Social Composite score was -0.1 versus -1.1 (P = 0.0064; effect size, 0.43). Common treatment-emergent adverse events included diarrhea (80.6% for trofinetide versus 19.1% for placebo), which was mostly mild to moderate in severity. Significant improvement for trofinetide compared with placebo was observed for the coprimary efficacy endpoints, suggesting that trofinetide provides benefit in treating the core symptoms of Rett syndrome.
Topics: Female; Humans; Rett Syndrome; Treatment Outcome; Glutamates; Double-Blind Method
PubMed: 37291210
DOI: 10.1038/s41591-023-02398-1