Search Results (190)

Rett syndrome is a severe neurodevelopmental disorder caused predominantly by loss-of-function mutations in the X-linked gene MECP2. In addition to a vast array of neurological and physiological impairments, patients also frequently develop severe osteopenia with increased fracture risk; however, the mechanisms underlying these skeletal defects are not completely understood. Previous work in Mecp2-null mouse models has suggested that osteopenia is mainly due to impaired osteoblast function and reduced bone formation. Here, we examined bone mass, microarchitecture, and remodeling parameters in a Mecp2-null mouse model during postnatal development, with a particular focus on osteoclast involvement. Microcomputed tomography and histomorphometric analyses showed reduced bone mineral density and trabecular bone volume, which are associated with increased trabecular separation and cortical thinning. These structural alterations were accompanied by increased osteoclast number per bone surface, elevated urinary deoxypyridinoline, and higher expression of osteoclast-associated genes, including Cathepsin K. Furthermore, gene expression analysis revealed an age-dependent shift in bone remodeling. At postnatal day 35, mutant mice showed reduced expression of Dlx5 and Dlx6, consistent with low bone turnover. By postnatal day 55, Rankl and Cathepsin K were markedly upregulated, suggesting an increase in osteoclast resorptive activity, while key osteoblast markers and the RANKL/OPG ratio did not change significantly. A potential cell-autonomous contribution of Mecp2 to osteoclast maturation is also suggested by the analysis of public transcriptomic datasets on human osteoclast differentiation. Together, our findings identify increased osteoclast activity as a significant contributor to Rett-associated osteopenia and suggest that skeletal pathology in Mecp2 deficiency progresses from an early low-turnover state to a later phase of increased osteoclast resorption. Full article

Background: Cognitive and psychiatric disorders are caused by a complex interplay between genetic predisposition, environmental exposures, and dynamic molecular regulation in the brain. Animal models provide a controlled environment for examining these mechanisms, and advances in transcriptome and epigenomic technologies have greatly expanded our knowledge of disease-relevant pathways. Objective: This scoping review systematically maps and synthesizes the epigenetic and transcriptomic findings from the established animal models of four neuropsychiatric conditions—autism spectrum disorder (ASD), schizophrenia, depression, and Rett syndrome—drawing on a PRISMA-ScR-guided literature search. The review characterizes the breadth of evidence, identifies convergent and divergent molecular pathways, and highlights the translational gaps and therapeutic implications. Methods: Research employing chromatin accessibility testing, genome-wide DNA methylation mapping, single-cell and bulk RNA sequencing, histone modification profiling, and multi-omics integration in mouse and other validated animal models was thoroughly reviewed. A quality appraisal of the primary experimental studies (n = 63) was performed using a modified CAMARADES checklist. Results: Beyond generalized cellular stress responses, multi-omics analysis emphasizes the cell-type- and context-dependent nature of epigenetic changes in animal models, including isoform-specific histone modifications and model-dependent binding of HDAC/MeCP2 complexes to genes involved in synaptic plasticity. Single-cell RNA sequencing analyses have uniformly shown transcriptional changes in parvalbumin-positive (PV+) interneurons. Conclusions: The specific convergence of epigenetic disruptions in neural circuits involved in synaptic structure and inhibitory function could play a role in the generation of neuropsychiatric phenotypes in animal models, highlighting the importance of circuit- and cell-type-specific epigenetics while pointing to potential therapeutic avenues. Full article

Background: Rett Syndrome (RTT) is a progressive neurodevelopmental disorder caused by MECP2 gene mutations. MeCP2 protein binding to methylated DNA is involved in normal brain development and function. T158M is a common RTT-associated mutation, where a threonine is replaced with a methionine, affecting protein function and stability. RTT has recently been identified as a neurometabolic disorder, with metformin emerging as a potential candidate drug. Metformin is a safe and accessible drug, commonly used for Type 2 diabetes. Our team previously studied the regulatory role of metformin on the expression of RTT-related genes/proteins using in vitro and in vivo approaches. However, the phenotypical and behavioral impact of metformin in transgenic mice carrying the common T158M mutation was not explored. Methods: Wild type (WT) and mutant Mecp2^T158M (Mecp2^tm4.1Bird) male mice were subjected to daily intraperitoneal injection of metformin for 20 days. The control mice received a daily intraperitoneal injection of the solvent. The main RTT-like phenotypical criteria were assessed daily. Behavioral tests included the open field test and elevated plus maze. Results: Behavioral tests indicated no significant effect of metformin on the anxiety levels, locomotion, and exploratory behaviors in the hemizygous male Mecp2^T158M mice, despite our observation of increased anxiety levels in the WT counterparts. In hemizygous male Mecp2^T158M mice, metformin treatment showed beneficial effects on RTT-like phenotypes, including breathing irregularities, gait abnormalities, hindlimb clasping, and overall total score. The positive effect of metformin was also observed on the body weight in the hemizygous male Mecp2^T158M mice. Conclusions: Our findings provide evidence for potential therapeutic effects of metformin for MeCP2-associated neurological disorders. Full article

Background/Objectives: Autophagy is an evolutionarily conserved degradation and recycling pathway through which cells deliver cytoplasmic components, including toxic or damaged proteins and organelles, to lysosomes for clearance. In neurons, which are largely post-mitotic, degradative pathways are essential to prevent the accumulation of cellular waste and to maintain nutrient and energy homeostasis. Increasing evidence suggests that autophagy plays a critical role during early brain development, when neuronal circuits are established, synaptic connections are refined, and activity-dependent mechanisms shape network architecture. However, the developmental regulation of autophagy-related genes and the composition of the autophagic machinery at synapses remain poorly understood. This study aimed to characterize the maturation-dependent dynamics of autophagy–lysosomal genes and to investigate the synaptic autophagy-associated proteome during cortical development. Methods: Genome-wide transcriptomic analyses were performed in the cortical brain region across developmental stages to assess changes in the expression of autophagy–lysosomal genes. In parallel, synaptosomes were isolated and subjected to proteomic analysis to identify autophagy-related proteins associated with synaptic compartments. Results: Transcriptomic profiling revealed stage-dependent regulation of autophagy–lysosomal genes during cortical maturation. Proteomic analysis of synaptosomes identified multiple autophagy-associated proteins enriched at synaptic sites, suggesting that components of the autophagic machinery are present at synapses and may participate in synaptic remodeling and function during key phases of neuronal network formation. Conclusions: These findings provide new insights into the developmental regulation of autophagy in the brain and highlight the potential contribution of synaptic autophagy to neuronal circuit maturation. Understanding these mechanisms may help identify novel therapeutic targets for neurological disorders associated with impaired synaptic and cellular homeostasis. Full article

Rett syndrome (RTT) is a neurodevelopmental disorder characterized by motor deficits, partly attributed to cerebellar dysfunction. RTT is primarily caused by mutations in the gene encoding the methyl-CpG-binding protein 2 (MECP2), which has been implicated in cholesterol homeostasis by mechanisms that remain poorly understood. Given that brain cholesterol is primarily synthesized de novo and that disrupted cholesterol homeostasis is linked to various neurological disorders, we aimed to investigate cholesterol regulation in the cerebellum of Mecp2-null mice, a well-established RTT model. We measured total cholesterol levels in cerebellar tissue and cerebellar synaptosomes and assessed the expression of genes involved in cholesterol biosynthesis and intracellular transport. Our results show significantly elevated total cholesterol in both cerebellar tissue and synaptosomes. Furthermore, we identified a marked reduction in CYP46A1 expression, which is essential for the elimination of encephalon sterols. In contrast, key cholesterol biosynthetic regulators (Srebp2, Hmgcs1, Sqle) showed no significant changes in expression, suggesting an impaired cerebellar cholesterol turnover—driven by defective clearance—rather than enhanced synthesis may underlie the metabolic imbalance observed in the cerebellum of the RTT mouse model. Altogether, these findings provide a mechanistic insight into how MeCP2 deficiency disrupts cerebellar cholesterol homeostasis and highlight cholesterol clearance pathways as potential contributors to RTT pathology and a factor to consider for further RTT therapeutic approaches. Full article

Background/Objectives: Factors modulating phenotypic variability in Rett syndrome (RTT, OMIM 312750) include X chromosome inactivation (XCI), type of MECP2 variant, and/or disease modifiers. Emerging evidence also points to multi-locus genetic variants. Understanding the phenotypic variability associated with multi-locus genetic diagnoses in individuals with RTT and MECP2-related disorders would be important not only for accurate diagnosis, risk stratification and clinical management but also to explain symptoms that might not be typically associated with RTT. Methods: We present a case series of five individuals with a diagnosis of RTT or an MECP2-related disorder with co-occurring genetic findings, including pathogenic variants, variants of unknown significance and chromosome duplications. Clinical features such as neurodevelopmental history and comorbid medical conditions were assessed alongside the genetic findings. Results: A review of 200 cases with RTT identified five cases (all females aged 7–27 years) with a co-occurring genetic finding. Each case harboured at least one additional genetic variant that included a beta thalassaemia trait, Calmodulin 3 (CALM3) missense variant, maternally inherited 22q12.3 to q13.1 duplication, 7p14.3 and Dynein Cytoplasmic 1 Heavy Chain 1 (DYNC1H1) variants of uncertain significance and a pathogenic Set Domain-containing protein 5 (SETD5) variant. A rare triple genetic finding was illustrated in a single case, combining MECP2, CALM3, and DYNC1H1 variants. Conclusions: This case series supports the premise that RTT and MECP2-related disorders exist in a more complex neurogenetic spectrum than previously defined. It also emphasises the complexity within MECP2-related disorders. They are not static, and in the context of severe treatment resistant epilepsy, MECP2 disorders can evolve over time, necessitating diagnostic reclassification. Although the co-occurrence of multiple genetic disorders in RTT and MECP2-related disorders is rare, these cases underscore the importance of considering cumulative genetic burden when evaluating individuals with atypical features or evolving neurodevelopmental phenotypes. Full article

Chromatin organization during postnatal development is very important for establishing neuronal function and may be disrupted in neurodevelopmental disorders that are associated with impaired brain function. Both the Methyl CpG-binding protein 2 (MeCP2) and the linker histone H1 are important chromatin regulators. Still, their developmental expression patterns and functional interactions across diverse genetic backgrounds are not well understood. This study examined changes in histone H1, histone H3, and MeCP2 levels in CD1 and C57BL/6 mice in two different strains, in the liver, cerebellum, and cerebral hemispheres obtained at two adolescent developmental stages [P21 (postnatal day 21) and P56]. We show that both strains have significant cerebral-specific increases in MeCP2 and H1, while H3 levels remain consistent. The CD1 strain exhibited hepatic H1 elevation between early (P21) and late (P56) adolescence, which was absent in the C57BL/6 strain. This highlights possible strain-dependent postnatal dynamic chromatin organization. Analysis of Mecp2^T158M (Mecp2^tm4.1Bird) mutant mice showed compensatory H1 elevation in the Purkinje layer of the cerebellum, indicating possible functional relation between these two chromatin-bound proteins. Despite having minimal MeCP2 protein levels, mutant mice had higher amounts of Mecp2 transcripts, suggesting post-transcriptional/post-translational regulations. Our results demonstrate that H1 and MeCP2 are subject to coordinated developmental control with possible interplay with the chromatin structure. Full article

This year, the selection criteria for highly cited articles in the ‘Molecular and Cellular Neuroscience’ section of Brain Sciences were focused on publications that achieved a citation count of 10 or more during 2024. Applying this metric, the Editorial Office, in collaboration with myself as Associate Editor of the ‘Molecular and Cellular Neuroscience’ section of the journal, identified eight articles that not only exemplified the mission of this section but also made significant scientific contributions by advancing our current understanding of the molecular and cellular mechanisms underlying major and rare neurological disorders. These articles encompass miscellaneous topics, including Alzheimer’s disease (AD), chronic alcoholism, glioblastoma multiforme (GBM), amyotrophic lateral sclerosis (ALS), cognitive impairment, cerebrovascular disease, and Rett syndrome (RTT). Importantly, several contributions highlight experimental therapeutic strategies aimed at mitigating pathogenic mechanisms, offering promising avenues for translational research and future clinical applications. Full article

Rett Syndrome (RTT) is a neurodevelopmental disorder characterized by mutations in the MeCP2 gene, predominantly affecting females. Recent work with MeCP2-deficient mouse models showed a significant role in glutamatergic transmission, specifically microglia-produced glutamate and glutaminase upregulation, in RTT pathology. The glutamine antagonist 6-diazo-5-oxo-L-norleucine (DON) is a potent glutaminase inhibitor; however, its use is limited due to systemic toxicities arising from its non-specific inhibition of glutamine-utilizing reactions. In this work, we determined whether dendrimer conjugation of a DON analog, TTM020 (or D-TTM020), results in targeted microglial glutaminase inhibition and behavioral changes in Mecp2 KO and heterozygous mice upon systemic administration. D-TTM020 at 1 mg/kg (drug basis) selectively and significantly inhibits glutaminase enzyme activity in the microglia of Mecp2 KO mice. Biweekly systemic treatment with 1 mg/kg of D-TTM020 improved the neurobehavioral phenotype in symptomatic Mecp2 KO and het mice. D-TTM020 also restored long-term retrieval of conditioned fear memory and improved cue responses during fear extinction after 8 weeks of treatment in symptomatic Mecp2 het mice. Our data indicate that selectively targeting glutamine metabolism in dysregulated glia using dendrimers represents a promising strategy that may offer a therapeutic approach for addressing glutamate dysregulation in RTT. Full article

Nonsense mutations, responsible for ~11% of gene lesions causing human monogenic diseases, introduce premature termination codons (PTCs) that lead to truncated proteins and nonsense-mediated mRNA decay (NMD). In the central nervous system (CNS), these mutations drive severe, progressive neurological conditions such as spinal muscular atrophy, Rett syndrome, and Duchenne muscular dystrophy. Readthrough therapies—strategies to override PTCs and restore full-length protein expression—have evolved from early aminoglycosides to modern precision tools including suppressor tRNAs, RNA editing, and CRISPR-based platforms. Yet clinical translation remains hampered by inefficient CNS delivery, variable efficacy, and the absence of personalized stratification. In this review, we propose a translational framework—the 4 Ds of Readthrough Therapy—to systematically address these barriers. The framework dissects the pipeline into Detection (precision patient identification and biomarker profiling), Delivery (engineered vectors for CNS targeting), Decoding (context-aware molecular correction), and Durability (long-term safety and efficacy). By integrating advances in machine learning, nanocarriers, base editing, and adaptive trial designs, this roadmap provides a structured strategy to bridge the translational gap. We advocate that a synergistic, modality-tailored approach will transform nonsense suppression from palliative care to durable, precision-based cures for once-untreatable neurological disorders. Full article

Background/Objectives: The Rett Syndrome Behavior Questionnaire (RSBQ) is a widely used caregiver-reported instrument for assessing behavioral and neurological features of Rett syndrome (RTT). However, a validated Korean version has not been available. This study aimed to translate the RSBQ into Korean (K-RSBQ) and to evaluate its psychometric properties in a Korean RTT population. Methods: The RSBQ was translated and back-translated using standardized procedures and refined through a Delphi process. Primary caregivers of individuals with clinically diagnosed RTT completed an online survey including the K-RSBQ and the Childhood Autism Rating Scale (CARS). Test–retest reliability was assessed in a subset of caregivers who completed the questionnaire twice within one week, and inter-rater reliability was evaluated when an additional caregiver was available. Results: Sixty-six primary caregivers participated. The K-RSBQ demonstrated high internal consistency for the total score (Cronbach’s α = 0.912) and moderate-to-high consistency across most subscales. Test–retest reliability for the total score was moderate (weighted κ = 0.594), while inter-rater reliability between primary and secondary caregivers was generally low. The hand behavior subscale showed low and non-significant test–retest reliability. The K-RSBQ total score exhibited a low-to-moderate correlation with the CARS total score, and the general mood subscale showed a moderate correlation with the CARS emotional response item. Caregivers reported minimal difficulty in understanding the questionnaire items. Conclusions: The K-RSBQ demonstrates acceptable internal consistency and test–retest reliability when administered to primary caregivers, with preliminary evidence supporting its construct validity. Although limitations exist regarding criterion validation and inter-rater agreement, the K-RSBQ represents a feasible and culturally adapted tool for assessing RTT-related behavioral features in Korean clinical and research settings. Full article

Rett syndrome (RTT) is a rare neurodevelopmental disorder that causes severe motor and cognitive impairments, limiting voluntary communication. Gaze-based technologies and virtual reality (VR) offer innovative ways to assess and enhance attention, happiness, and learning in individuals with minimal motor control. This study investigated and compared visual-attentional and emotional engagement in girls with RTT and typically developing (TD) peers during exploration of a virtual forest presented in 2D and immersive 3D (VR) formats across four progressively complex tasks. Twelve girls with RTT and 12 TD peers completed eye-tracking tasks measuring reaction time, fixation duration, disengagement events, and observed happiness. Girls with RTT showed slower responses and more disengagements overall, but VR significantly improved attentional efficiency in both groups, resulting in faster reaction times (η²_p = 0.36), longer fixations (η²_p = 0.31), and fewer disengagements (η²_p = 0.27). These effects were stronger in the RTT group. Both groups also showed greater happiness in VR settings (RTT: p = 0.011; TD: p = 0.015), and in participants with RTT, peaks in attention coincided with peak happiness, indicating a link between happiness and cognitive engagement. Immersive VR thus appears to enhance attention and affect in RTT, supporting its integration into personalized neurorehabilitation. Full article

Pridopidine is a highly selective sigma-1 receptor (S1R) agonist in clinical development for Huntington’s disease (HD) and amyotrophic lateral sclerosis (ALS). The S1R is a ubiquitous chaperone protein enriched in the central nervous system and regulates multiple pathways critical for neuronal cell function and survival, including cellular stress responses, mitochondrial function, calcium signaling, protein folding, and autophagy. S1R has a crucial role in the ER mitochondria-associated membrane (MAM), whose dysfunction is implicated in several neurodegenerative diseases. By activating the S1R, pridopidine corrects multiple cellular pathways necessary to the cell’s ability to respond to stress, which are disrupted in neurodegenerative diseases. Pridopidine restores MAM integrity; rescues Ca²⁺ homeostasis and autophagy; mitigates ER stress, mitochondrial dysfunction, and oxidative damage; and enhances brain-derived neurotrophic factor (BDNF) axonal transport and secretion, synaptic plasticity, and dendritic spine density. Pridopidine demonstrates neuroprotective effects in in vivo models of neurodegenerative diseases (NDDs). Importantly, pridopidine demonstrates the biphasic dose response characteristic of S1R agonists. In clinical trials in HD and ALS, pridopidine has shown benefits across multiple endpoints. Pridopidine’s mechanism of action, modulating core cellular survival pathways, positions it as a promising candidate for disease modification for different nervous system disorders. Its broad therapeutic potential includes neurodevelopmental disorders, and rare diseases including Wolfram syndrome, Rett syndrome, and Vanishing White Matter Disease. Here, we review the experimental data demonstrating pridopidine’s S1R-mediated neuroprotective effects. These findings underscore the therapeutic relevance of S1R activation and support further investigation of pridopidine for the treatment of different neurodegenerative diseases including ALS and HD. Full article

Rett syndrome (RTT) presents with a wide range of symptoms spanning various clinical areas. Capturing symptom change as the disorder progresses is challenging. Wearable sensors offer a non-invasive and objective means of monitoring disease states in neurodevelopmental disorders. The goal of this study was to conduct a systematic literature review to critically appraise the literature on the use of wearable sensors in individuals with RTT. The PRISMA criteria were used to search four databases without time restriction and identified 226 records. After removing duplicates, the titles and abstracts of 184 records were screened, 147 were excluded, and 37 were assessed for eligibility. Ten (10) articles remained, and a further two were included after additional searching. In total, 12 articles were included in the final analysis. The sample size ranged from 7 to 47 subjects with an age range of 1 to 41 years. Different wearable biosensor devices were used across studies, with the Empatica E4 wearable device being most frequently used in 33% (4/12) of the studies. All the studies demonstrated a high methodological quality with a low risk of bias. Evidence from wearable sensors, combined with machine learning methods, enabled the prediction of different sleep patterns and clinical severity in RTT. Given the small sample size and the limitations of available data for training machine learning models, we highlight areas for consideration. The review emphasises the need to enhance research on the application of wearable sensors in epilepsy and gastrointestinal manifestations/morbidity in RTT. Increased electrodermal activity (EDA), % of maximum heart rate (HRmax%) and the heart rate to low-frequency power (HR/LF) ratio were identified as physiological measures potentially associated with disease states. Based on the evidence synthesis, the role of physiological parameters and their association with symptom management in RTT is discussed. Full article

Rett syndrome (RTT) is a severe neurodevelopmental disorder caused primarily by mutations in the gene encoding the methyl-CpG-binding protein 2 (Mecp2). Mecp2 binds to methylated cytosines, playing a crucial role in chromatin organization and transcriptional regulation. At the neurobiological level, RTT is characterized by dendritic spine dysgenesis and altered excitation–inhibition balance, drawing attention to the mechanisms that scale from mutations in a nuclear protein to altered neuronal connectivity. Although Mecp2 dysfunction disrupts multiple neuronal processes, emerging evidence highlights altered calcium (Ca²⁺) signaling as a central contributor to RTT pathophysiology. This review explores the link between Mecp2 and Ca²⁺ regulation by highlighting how Mecp2 affects Ca²⁺-dependent transcriptional pathways, while Ca²⁺ modulates Mecp2 function by inducing post-translational modifications. We discuss this crosstalk in light of evidence from RTT models, with a particular focus on the brain-derived neurotrophic factor BDNF-miR132-Mecp2 axis and the dysregulation of ryanodine receptors (RyRs). Additionally, we examine how these perturbations contribute to the reduced structural plasticity and the altered activity-driven gene expression that characterizes RTT. Understanding the intersection between Mecp2 function and Ca²⁺ homeostasis will provide critical insights into RTT pathogenesis and potential therapeutic targets aimed at restoring neuronal connectivity. Full article