SummaryRett syndrome is a debilitating neurodevelopmental disorder with cerebral processing impairments caused byMECP2loss-of-function mutations. Mecp2-deficient mouse models reveal disruptions of microscale cortical circuits. Yet how cellular-scale information processing is altered in Mecp2-deficient microscale functional networks is unknown. We investigated the development of functional connectivity, network topology, and dynamics in microelectrode array (MEA) recordings of primary cortical cultures from Mecp2-deficient and wild-type mice. Mecp2-deficient cortical networks developed more slowly and showed decreased functional connectivity compared to wild-type, leading to smaller network size, density, and strength of connectivity. Altered network topological features in Mecp2-deficient microscale circuits predicted decreased efficiency and information-sharing capacity. This reveals developmental deficits in microscale functional networks, which may in turn underlie the cortical decline and severe cognitive disability in Rett syndrome. These findings also offer circuit-level targets and an in-vitro approach for evaluating new therapeutic products for restoring microscale network function.

Lipid peroxidation-induced cell death in Rett syndrome.

Actigraphy is being increasingly used to assess sleep and circadian rhythms among populations with intellectual and developmental disabilities and genetic syndromes, including Rett syndrome and related disorders, but the reliability of these measures in these populations is unclear. The primary purpose of the current study was to evaluate the impact of recording duration on the reliability of various measures of sleep and circadian rhythm in Rett and related syndromes. Two 14-day recordings were collected between 4 and 12 weeks apart in a sample of 30 individuals (aged 2-36 years; 97% female). Reliability was estimated by calculating statistics based on 3, 5, 7, 10 or 13-14 nights of recording. Most measures of average sleep quality could be reliably estimated with 7-10 nights. Measures of night-to-night variability in sleep timing showed poor reliability at all recording durations, whereas night-to-night variability in sleep duration showed adequate reliability at 5-7 days of recording. The reliability of measures of circadian rhythm was highly variable. The results suggest that the optimal recording durations for actigraphy in this population vary based on the specific metrics of interest, but most can be measured reliably.

Ghrelin restores D1 receptor-mediated dopamine neurotransmission and enhances attentive behaviour in Mecp2 KO mice.

EPH205 Real-World Treatment Patterns of Trofinetide in Rett Syndrome: Analysis of Medical Pharmacy-Linked Claims Database in the United States

Natural history of epilepsy in FOXG1 Syndrome.

Real-world benefits and tolerability of trofinetide for the treatment of Rett syndrome: The LOTUS study.

Social memory impairments in Mecp2 knockout (KO) mice result from altered neuronal activity in the monosynaptic projection from the ventral hippocampus (vHIP) to the medial prefrontal cortex (mPFC). The hippocampal network is hyperactive in this model for Rett syndrome (RTT), and such atypically heightened neuronal activity propagates to the mPFC through this monosynaptic projection, resulting in altered mPFC network activity and social memory deficits. However, the underlying mechanism of cellular dysfunction within this projection between vHIP pyramidal neurons (PYRs) and mPFC PYRs and parvalbumin interneurons (PV-INs) resulting in social memory impairments in Mecp2 KO mice has yet to be elucidated. We confirmed social memory (but not sociability) deficits in Mecp2 KO mice using a new four-chamber social memory arena, designed to minimize the impact of the tethering to optical fibers required for simultaneous in vivo fiber photometry of Ca2+-sensor signals during social interactions. mPFC PYRs of wild-type (WT) mice showed increases in the amplitude of population Ca2+ signals during explorations of a novel toy mouse and interactions with both familiar and novel mice, whereas PYRs of Mecp2 KO mice showed smaller population Ca2+ signals during interactions only with live mice. On the other hand, mPFC PV-INs of Mecp2 KO mice showed larger population Ca2+ signals during interactions with a familiar cage-mate compared with those signals in PYRs, a difference absent in the WT mice. These observations suggest atypically heightened inhibition and impaired excitation in the mPFC network of Mecp2 KO mice during social interactions, potentially driving their deficit in social memory.NEW & NOTEWORTHY The hippocampus is hyperactive in a mouse model for Rett syndrome, and such atypically heightened activity propagates to the medial prefrontal cortex (mPFC) through a monosynaptic projection, resulting in altered mPFC activity and social memory deficits. Here, we used fiber photometry of population Ca2+ signals as surrogates of neuronal activity, and show that atypically heightened inhibition from pyramidal neuron (PYR)-targeting GABAergic parvalbumin interneurons, and impaired PYR activity in the mPFC of Rett mice during social interactions, driving their deficit in social memory.

EPH66 Durable Medical Equipment and Ancillary Service Use in Rett Syndrome Management: A Global Comprehensive Review of Literature

Pre-operative zoledronate is safe for children with medical complexity undergoing posterior spinal fusion for neuromuscular scoliosis.

Loss-of-function mutations in methyl-CpG binding protein 2 (MECP2) cause Rett syndrome. While we know that MeCP2 binds to methylated cytosines on DNA, the full breadth of the molecular mechanisms by which MeCP2 regulates gene expression remains incompletely understood. Here, using a genetic modifier screen, we identify the super elongation complex, a P-TEFb–containing elongation factor that releases promoter-proximally paused RNA polymerase II, as a genetic interactor of MECP2. MeCP2 physically interacts with SEC subunits and directly binds AFF4, the scaffold of the SEC, via the transcriptional repression domain. Furthermore, MeCP2 facilitates the binding of AFF4 on a subset of genes in the mouse brain regulating synaptic plasticity and concordantly promotes the binding of RNA polymerase II on these genes. Last, while haploinsufficiency of Aff4 does not exhibit any behavioral deficits in mice, it exacerbates the impaired contextual learning behavior of Mecp2 hypomorphic mice. We propose a previously unknown mechanism by which MePC2 regulates gene expression underlying synaptic plasticity.

To systematically review and characterize the spectrum of non-epileptic paroxysmal events in individuals with Rett syndrome (RTT). We conducted adescriptive systematic review of observational evidence. Searches were conducted across the PubMed, Embase, and OVID databases for studies published from January 1962 to September 2024. Eligible studies included case reports, case series, cohort studies, and small clinical trials that described non-epileptic events in individuals with clinically or genetically confirmed RTT. Data were extracted on study design, participant characteristics, and event types. Events were categorized into respiratory, neuromotor, and behavioural domains. Sixty-two studies met the inclusion criteria, representing a wide age range of individuals with RTT. The most frequently reported paroxysmal non-epileptic events were respiratory disturbances, including breath-holding and hyperventilation, followed by vacant spells, involuntary movements, and behavioural episodes such as agitation and inappropriate laughter. Discrepancies were noted between the diagnostic attribution of clinician-reported and family-reported events. The term 'Rett episodes' was used by a minority of authors. A wide range of non-epileptic paroxysmal events requiring different treatment approaches are experienced by patients with RTT. Enhancing clinician awareness and developing clearer diagnostic frameworks are key to improving classification accuracy and preventing unnecessary treatment.

Adenosine deaminases acting on RNA (ADAR) catalyze the deamination of adenosine to inosine in double-stranded RNA. Because inosine is read as guanosine during translation, this process enables programmable A-to-G recoding at the transcript level. ADARs can be harnessed for therapeutic correction of pathogenic mutations through site-directed RNA editing with guide RNAs. To expand the design space of editing-enabling guides, we applied EMERGe, a high-throughput screening platform, to identify motifs targeting a premature termination codon in the MeCP2 transcript associated with Rett syndrome. This uncovered a guide RNA motif that supported efficient ADAR2-mediated editing in vitro, featuring a 5'-GUG-3' sequence predicted to form an asymmetric loop. To enable therapeutic application, structure-activity relationship studies and chemical optimization were performed, yielding a fully modified guide RNA with 2'-O-methyl, 2'-fluoro, and phosphorothioate linkages. This stabilized guide retained the activity of unmodified RNA and showed enhanced nuclease resistance. The optimized guide induces dose-dependent editing at two MECP2 loci in reporter assays in HEK293T cells, demonstrating that EMERGe-selected motifs can be rendered viable in cells through targeted chemical modification. These findings highlight the utility of EMERGe as a discovery platform and establish a pipeline for identifying and optimizing editing-enabling guide RNA features beyond traditional design rules.

Epidemiology and Healthcare Resource Utilization of Rett Syndrome in Canada: the Ontario experience.

The role of tryptophan metabolism has been recognized in a wide range of physiological and pathological processes but is still only partially understood. Growing evidence highlights the importance of maintaining tryptophan homeostasis throughout life, with its disruption now linked to various neuropsychiatric conditions spanning from early life to aging. While it is increasingly evident that alterations in tryptophan metabolism have significant implications for both neurodevelopmental and neurodegenerative disorders, research has predominantly focused on the latter, leaving neurodevelopmental aspects comparatively underexplored. This review provides a comprehensive overview of both preclinical and clinical studies, highlighting the intricate relationship between tryptophan metabolism and neurodevelopment. Particular focus is given to the kynurenine pathway and gut microbiota-derived indole production, two interconnected metabolic branches with profound effects on brain maturation, plasticity, and immune regulation. Finally, we examine the pathophysiological consequences of tryptophan dysregulation in neurodevelopmental disorders, including autism spectrum disorder, attention-deficit/hyperactivity disorder, and Rett syndrome. We also discuss potential therapeutic strategies targeting tryptophan metabolism in these conditions.

Rett Syndrome is a rare, x-linked genetic neurological disorder caused by MECP2 gene mutations. This progressive neurodevelopmental disorder hinders patients' ability to breathe and eat normally. It is unclear how Mecp2- deficiency results in a high percentage of dysphagia and aspiration pneumonia in patients with Rett syndrome. We aim to determine the effects of Mecp2 -deficiency on swallow related neuromuscular mechanisms contributing to dysphagia in Rett syndrome. Swallow and breathing were detected using electrophysiology in the submental and laryngeal muscle complexes and the hypoglossal and vagus nerves. Several medullary motoneuron populations involved in swallowing were examined by immunohistochemistry in pre and post symptomatic Mecp2 -deficient male and female mice. Swallow-related submental complex duration and amplitude were significantly decreased in both Mecp2 -/y and Mecp2 +/-compared to wild-type, due to decreased motor unit activation. In both Mecp2- deficient mice, cholinergic staining in hypoglossal, facial, and trigeminal nuclei were decreased. We noted a significant increase in the transition time from inspiration to swallow, swallow to the subsequent inspiration, and impaired respiratory rhythm regeneration in Mecp2 -/y, but not Mecp2 +/- mice. Mecp2- deficiency resulted in impaired brainstem cholinergic signaling, which contribute to weakened submental muscle complex activity, and impaired swallow related laryngeal vestibular closure. These results suggest Mecp2- deficient mice are a viable pre-clinical model to further study dysphagia in Rett syndrome.

Rett syndrome (RTT) is a devastating neurodevelopmental disorder with developmental regression affecting motor, sensory, and cognitive functions. Sensory disruptions contribute to the complex behavioral and cognitive difficulties and represent an important target for therapeutic interventions. Although genetic medicine-based therapies targeting MeCP2 have successfully restored motor and respiratory functions in animal models, their ability to reverse sensory deficits across levels of the visual pathway remains largely unexplored. Using genetically reversible mouse models of MeCP2 deficiency (Mecp2stop/y and Mecp2stop/x), we applied advanced electrophysiological, anatomical, and behavioral techniques to evaluate visual function, a critical sensory domain impaired in both animal models and RTT patients. In Mecp2stop/y mice, initiating MeCP2 expression after postnatal day 35 (P35) reversed progressive cortical dysfunction, prevented thalamic circuit disorganization, and restored visual function, despite some remaining cortical anatomical abnormalities. Even in fully regressed adult Mecp2stop/x heterozygous female mice, MeCP2 reactivation was sufficient to reduce the symptoms. These findings highlight the remarkable sensitivity of cortical circuits to MeCP2 expression in both developing and mature brain. Importantly, restoring just 60%-70% of MeCP2 protein levels was sufficient to rescue sensory functions, even after the onset of regression. This underscores the transformative potential of genetic medicine-based therapies in RTT, suggesting that even partial restoration of MeCP2 can meaningfully improve sensory processing and quality of life for patients.

Butyrate modifies epigenetic and immune pathways in peripheral mononuclear cells from children with neurodevelopmental disorders associated with chromatin dysregulation.

CDKL5-deficiency disorder or CDD, which results in intellectual disability, speech and motor deficits, and seizures that can start as early as six weeks after birth, is caused by de novo mutations in the CDKL5 gene. In early 2022, the FDA approved Ganaxolone (Commercial name: Ztalmy) for treatment of seizures in CDD patients 2 years and older. Ganaxolone has been reported to act as a GABAA receptor agonist that helps reduce neuronal excitability; however, based on its chemical structure we hypothesized that ganaxolone may also act as a PTP1B inhibitor. We observed that ganaxalone was able to inhibit PTP1B activity both in an in vitro assay of enzyme activity and in different cell models, in a comparable way to known inhibitors of PTP1B, including MSI-1436, which has a similar chemical structure. Additionally, inhibition of PTP1B in differentiating SH-SY5Y cells increased TRKB/BDNF signaling. This effect was prominent in CDKL5-KO cells, where inhibition of PTP1B brought TRKB levels and BDNF signaling to levels similar to those of wild-type cells and the observed signaling changes also coincided with restoration of cellular morphology. Finally, loss of CDKL5 function resulted in increased levels of PTP1B. Our results suggest that, like in Rett syndrome, targeting PTP1B may be a beneficial therapeutic strategy for CDD.

To assess the risk of developing ocular alignment disorders, refractive errors, amblyopia, and nystagmus in patients with Rett syndrome. This retrospective cohort study used de-identified patient data from the TriNetX US Collaborative network and compared a Rett syndrome and a control cohort. Propensity score matching was conducted to balance demographics and well-characterized comorbidities. Statistical analysis calculated risk ratios (RRs) and 95% confidence intervals (CIs), with significance defined by excluding CIs between 0.9 and 1.1. Patients with Rett syndrome had an increased risk of developing strabismus (RR: 3.39; CI: 2.47 to 4.65) and risk for the specific horizontal subtypes of esotropia (RR: 4.06; CI: 2.26 to 7.26) and exotropia (RR: 2.92; CI: 1.83 ro 4.68). Additionally, patients with Rett syndrome had an increased risk of developing amblyopia (RR: 1.90; CI: 1.28 to 2.82) and nystagmus (RR: 1.98; CI: 1.12 to 3.53). No differences in risk were found for astigmatism, myopia, and hyperopia development given Rett syndrome diagnosis. These findings demonstrate the importance of regularly monitoring ocular health in patients with Rett syndrome and a need for further investigation into the underlying mechanisms linking the disease with these specific ocular pathologies.