MECP2 Research Articles

Neurophysiological markers that link genes and behavior in humans: examples from rare genetic syndromes associated with autism spectrum disorders

Rare genetic syndromes associated with autism spectrum disorders have several noninvasive neurophysiological markers that can be linked with molecular genetic characteristics and behavioral characteristics in these diseases. For the recently discovered Potocki–Lupski syndrome associated with disturbances on the 17p11.2 segment, a previously undescribed epileptiform activity was detected, characterized by a saw-like hypersynchronization at a frequency of 13 Hz, which may indicate a certain type of disturbance in the excitation/inhibition balance in neural networks. For a rare case of microduplication in SH3 and ankyrin repeat domains 3 (SHANK3), also associated with the Phelan–McDermid syndrome, we described a pathway from a violation in the functioning of the SHANK3 protein, through a distorted interaction of excitatory and inhibitory neurons, primarily associated with hypofunction of N-methyl-D-aspartate receptors on inhibitory neurons, to reduced temporal resolution in the auditory cortex, reflected in the absence of response following 40 Hz auditory stimulation (40 Hz auditory steady-state response) and underlying problems in speech development. For the Rett syndrome, which is caused by a mutation in methyl CpG binding protein 2 (MECP2), which has a very wide influence on many other genes, the neurophysiological findings were also diverse. Among the most promising are changes in sensorimotor rhythm, potentially associated with a key symptom of the disease, namely, stereotyped hand movements, as well as more delayed latency of the main components of the event-related potentials, which can have a cascading effect on information processing and affect the perception of basic information, including speech. This review focuses on the presentation of the concept of a neurophysiological profile, the construction of which can help not only to objectify the diagnosis of developmental disorders, but also in the construction of a mechanistic chain from gene to behavior.

The Effects of Larval Cryopreservation on the Epigenetics of the Pacific Oyster Crassostrea gigas.

High mortalities and highly variable results during the subsequent development of post-thaw larvae have been widely considered as key issues restricting the application of cryopreservation techniques to support genetic improvement programs and hatchery production in farmed marine bivalve species. To date, few studies have been undertaken to investigate the effects of cryodamage at the molecular level in bivalves. This study is the first to evaluate the effect of larval cryopreservation on the epigenetics of the resultant progenies of the Pacific oyster Crassostrea gigas. The results show that the level of DNA methylation was significantly (p < 0.05) higher and lower than that of the control when the trochophore larvae were revived and when they developed to D-stage larvae (day 1 post-fertilization), respectively, but the level returned to the control level from day 8 post-fertilization onwards. The expression of the epigenetic regulator genes DNMT3b, MeCP2, JmjCA, KDM2 and OSA changed significantly (p < 0.05) when the trochophore larvae were thawed, and then they reverted to the control levels at the D- and later larval developmental stages. However, the expression of other epigenetic regulator genes, namely, MBD2, DNMT1, CXXC1 and JmjD6, did not change at any post-thaw larval developmental stage. For the newly thawed trochophore larvae, the amount of methylated H3K4Me1 and H3K27Me1 significantly changed, and the expression of all Jumonji orthologs, except that of Jumonji5, significantly (p < 0.05) decreased. These epigenetic results agree with the data collected on larval performances (e.g., survival rate), suggesting that the effect period of the published cryopreservation technique on post-thaw larvae is short in C. gigas.

Rett and Rett-related disorders: Common mechanisms for shared symptoms?

Rett syndrome is a neurodevelopmental disorder caused by loss-of-function mutations in the methyl-CpG binding protein-2 (MeCP2) gene that is characterized by epilepsy, intellectual disability, autistic features, speech deficits, and sleep and breathing abnormalities. Neurologically, patients with all three disorders display microcephaly, aberrant dendritic morphology, reduced spine density, and an imbalance of excitatory/inhibitory signaling. Loss-of-function mutations in the cyclin-dependent kinase-like 5 (CDKL5) and FOXG1 genes also cause similar behavioral and neurobiological defects and were referred to as congenital or variant Rett syndrome. The relatively recent realization that CDKL5 deficiency disorder (CDD), FOXG1 syndrome, and Rett syndrome are distinct neurodevelopmental disorders with some distinctive features have resulted in separate focus being placed on each disorder with the assumption that distinct molecular mechanisms underlie their pathogenesis. However, given that many of the core symptoms and neurological features are shared, it is likely that the disorders share some critical molecular underpinnings. This review discusses the possibility that deregulation of common molecules in neurons and astrocytes plays a central role in key behavioral and neurological abnormalities in all three disorders. These include KCC2, a chloride transporter, vGlut1, a vesicular glutamate transporter, GluD1, an orphan-glutamate receptor subunit, and PSD-95, a postsynaptic scaffolding protein. We propose that reduced expression or activity of KCC2, vGlut1, PSD-95, and AKT, along with increased expression of GluD1, is involved in the excitatory/inhibitory that represents a key aspect in all three disorders. In addition, astrocyte-derived brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1), and inflammatory cytokines likely affect the expression and functioning of these molecules resulting in disease-associated abnormalities.

The Use of tDCS in a Patient with MECP2 Gene Mutation Presenting with Recurrent Catatonia: A Case Report.

The Use of tDCS in a Patient with MECP2 Gene Mutation Presenting with Recurrent Catatonia: A Case Report.

Generation of an integration-free induced pluripotent stem cell line, FJMUUHi002-A, from a Rett syndrome patient with a heterozygous mutation p. R133C in MeCP2

The human iPS cell line, hiPS-RTT (FJMUi002-A), is derived from peripheral blood mononuclear cells (PBMCs) from a 12-year-old female RTT patient carrying a heterozygous p. R133C (c.397C > T) mutation in the MeCP2 gene. The hiPS-RTT cell line was generated by non-integrative reprogramming vectors encoding OCT3/4, SOX2, KLF4, and c-MYC and was free of genomically integrated reprogramming genes. The hiPS-RTT cell line had a normal karyotype, expressed pluripotency markers, and had capacity to form three germ layers in vitro and in vivo, which offering a useful resource to study the pathogenesis and treatment strategies of RTT.

Trofinetide in Rett syndrome: A brief review of safety and efficacy.

Rett syndrome (RTT) is a rare genetic neurological disorder that primarily affects girls and is caused by mainly mutations in the methyl-CpG-binding protein 2 (MECP2) gene, leading to critical issues in normal brain function. The condition has a global prevalence of 5 to 10 cases per 100,000 females, and there is currently no cure for RTT. However, therapy is available to manage the symptoms and improve quality of life. Trofinetide, an insulin-like growth factor 1, was originally developed as a stroke medication and progressed to Phase II clinical trials, where it exhibited favorable safety and efficacy profiles by improving several core RTT symptoms. Recently, Trofinetide received the US Food and Drug Administration (FDA) approval and orphan drug designation for the treatment of RTT, making it the first approved drug for this rare genetic disorder. It has also shown to be safe, well-tolerated and with no known drug interactions. These findings suggest that Trofinetide is a promising treatment option for individuals with RTT.

RETT SYNDROME: A CASE REPORT

RETT syndrome is a rare,genetic neurodevelopmental disorder that mainly affect girls, at the first 6 months of live the child have a normal psychomotor and cognitive development, then appears a psychomotor regression with loss of hand use and the appearance of manual stereotypies. This syndrome is essentially related to a mutation in the MECP2 gene. We report the case of an 8-year-old girl with RETT syndrome, who showed normal neurological development up to the age of 8 months, with psychomotor regression and manual stereotypy, and no other neurological signs, thus, no epileptic seizures or respiratory disorders such as hyperpnea. Electroencephalography and genetic studies were in favor of RETT syndrome.

LTP is Absent in the CA1 Region of the Hippocampus of Male and Female Rett Syndrome Mouse Models

Rett syndrome (RTT) is a debilitating neurodevelopmental disorder caused by mutations in the X-linked methyl-CpG-binding protein 2 (MeCP2) gene, resulting in severe deficits in learning and memory. Alterations in synaptic plasticity have been reported in RTT, however most electrophysiological studies have been performed in male mice only, despite the fact that RTT is primarily found in females. In addition, most studies have focused on excitation, despite the emerging evidence for the important role of inhibition in learning and memory. Here, we performed an electrophysiological characterization in the CA1 region of the hippocampus in both males and females of RTT mouse models with a focus on neurogliaform (NGF) interneurons, given that they are the most abundant dendrite-targeting interneuron subtype in the hippocampus. We found that theta-burst stimulation (TBS) failed to induce long-term potentiation (LTP) in either pyramidal neurons or NGF interneurons in male or female RTT mice, with no apparent changes in short-term plasticity (STP). This failure to induce LTP was accompanied by excitation/inhibition (E/I) imbalances and altered excitability, in a sex- and cell-type specific manner. Specifically, NGF interneurons of male RTT mice displayed increased intrinsic excitability, a depolarized resting membrane potential, and decreased E/I balance, while in female RTT mice, the resting membrane potential was depolarized. Understanding the role of NGF interneurons in RTT animal models is crucial for developing targeted treatments to improve cognition in individuals with this disorder.

Neuronal-type-specific epigenome editing to decrease SNCA expression: Implications for precision medicine in synucleinopathies

Overexpression of SNCA has been implicated in the pathogenesis of synucleinopathies, particularly Parkinson's disease (PD) and dementia with Lewy bodies (DLB). While PD and DLB share some clinical and pathological similarities, each disease presents distinct characteristics, including the primary affected brain region and neuronal type. We aimed to develop neuronal-type-specific SNCA-targeted epigenome therapies for synucleinopathies. The system is based on an all-in-one lentiviral vector comprised of CRISPR-dSaCas9 and guide RNA (gRNA) targeted at SNCA intron 1 fused with a synthetic repressor molecule of Krüppel-associated box (KRAB)/ methyl CpG binding protein 2 (MeCp2) transcription repression domain (TRD). To achieve neuronal-type specificity for dopaminergic and cholinergic neurons, the system was driven by tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) promoters, respectively. Delivering the system into human induced pluripotent stem cell (hiPSC)-derived dopaminergic and cholinergic neurons from a patient with the SNCA triplication resulted in efficient and neuronal-type-specific downregulation of SNCA-mRNA and protein. Furthermore, the reduction in SNCA levels by the gRNA-dSaCas9-repressor system rescued disease-related cellular phenotypes including Ser129-phophorylated α-synuclein, neuronal viability, and mitochondrial dysfunction. We established a novel neuronal-type-specific SNCA-targeted epigenome therapy and provided invitro proof of concept using human-based disease models. Our results support the therapeutic potential of our system for PD and DLB and provide the foundation for further preclinical studies in animal models toward investigational new drug (IND) enablement and clinical trials.

Inhibitory synaptic transmission is impaired in the Kölliker-Fuse of male, but not female, Rett syndrome mice.

Rett syndrome (RTT) is a severe neurodevelopmental disorder that mainly affects females due to silencing mutations in the X-linked MECP2 gene. One of the most troubling symptoms of RTT is breathing irregularity, including apneas, breath-holds, and hyperventilation. Mice with silencing mutations in Mecp2 exhibit breathing abnormalities similar to human patients and serve as useful models for studying mechanisms underlying breathing problems in RTT. Previous work implicated the pontine, respiratory-controlling Kölliker-Fuse (KF) in the breathing problems in RTT. The goal of this study was to test the hypothesis that inhibitory synaptic transmission is deficient in KF neurons from symptomatic male and female RTT mice. We performed whole cell voltage-clamp recordings from KF neurons in acute brain slices to examine spontaneous and electrically evoked inhibitory post-synaptic currents (IPSCs) in RTT mice and age- and sex-matched wild-type mice. The frequency of spontaneous IPSCs was reduced in KF neurons from male RTT mice but surprisingly not in female RTT mice. In addition, electrically evoked IPSCs were less reliable in KF neurons from male, but not female, RTT mice, which was positively correlated with paired-pulse facilitation, indicating decreased probability of release. KF neurons from male RTT mice were also more excitable and exhibited shorter-duration action potentials. Increased excitability of KF neurons from male mice was not explained by changes in axon initial segment length. These findings indicate impaired inhibitory neurotransmission and increased excitability of KF neurons in male but not female RTT mice and suggest that sex-dependent mechanisms contribute to breathing problems in RTT.NEW & NOTEWORTHY Kölliker-Fuse (KF) neurons in acute brain slices from male Rett syndrome (RTT) mice receive reduced inhibitory synaptic inputs compared with wild-type littermates. In female RTT mice, inhibitory transmission was not different in KF neurons compared with controls. The results from this study show that sex-specific alterations in synaptic transmission occur in the KF of RTT mice.

MiR-488-3p facilitates wound healing through CYP1B1-mediated Wnt/β-catenin signaling pathway by targeting MeCP2.

Diabetic wounds are difficult to heal, but the pathogenesis is unknown. MicroRNAs (miRNAs) are thought to play important roles in wound healing. The effect of miR-488-3p in wound healing was studied in this article. The gene methylation was measured by methylation specific PCR (MSP) assay. A dual-luciferase reporter assay was adopted to analyze the interaction between miR-488-3p and MeCP2. Cytochrome P450 1B1 (CYP1B1) is a monooxygenase belonging to the cytochrome P450 family that aids in wound healing. Our findings showed that the miR-488-3p and CYP1B1 expression levels were much lower in wound tissues of diabetics with skin defects, but the methyl-CpG-binding protein 2 (MeCP2) level was significantly higher than that in control skin tissues. MiR-488-3p overexpression increased cell proliferation and migration, as well as HUVEC angiogenesis, while inhibiting apoptosis, according to function experiments. In vitro, MeCP2 inhibited wound healing by acting as a target of miR-488-3p. We later discovered that MeCP2 inhibited CYP1B1 expression by enhancing its methylation state. In addition, CYP1B1 knockdown inhibited wound healing. Furthermore, MeCP2 overexpression abolished the promoting effect of miR-488-3p on wound healing. It also turned out that CYP1B1 promoted wound healing by activating the Wnt4/β-catenin pathway. Animal experiments also showed that miR-488-3p overexpression could accelerate wound healing in diabetic male SD rats. MiR-488-3p is a potential therapeutic target for diabetic wound healing since it improved wound healing by activating the CYP1B1-mediated Wnt4/-catenin signaling cascade via MeCP2.

A Review on Rett Syndrome: A Debilitating Neurodevelopmental Disorder

Rett syndrome is a neurodevelopmental disorder primarily affecting females, characterised by slowed growth, developmental regression, loss of fine motor skills, communication difficulties, and stereotypical hand movements. It is strongly associated with mutations in the MECP2 gene, while other variations have been linked to FOXG1 and CDKL5 mutations. This review provides an in-depth understanding of Rett syndrome, including its causes, symptoms, and available treatments. The epidemiology of Rett syndrome indicates a varying prevalence across different regions. Males with Rett syndrome, though rare, have been reported. The aetiology of Rett syndrome involves MECP2 mutations that lead to functional loss, affecting synapse development and maintenance. Mitochondrial dysfunction and oxidative stress have also been implicated in the disorder. Neuropathological findings reveal specific abnormalities in various brain regions. The symptoms of Rett syndrome include slowed head growth, abnormal gait, loss of intentional hand movements, breathing difficulties, and loss of speech. Complications such as metabolic issues, epilepsy, scoliosis, and gastrointestinal dysfunction are common. The diagnosis relies on clinical criteria and genetic testing for MECP2 mutations. Treatment for Rett syndrome is symptomatic and includes individualised rehabilitation therapies such as physical therapy, applied behaviour analysis, environmental enrichment, hydrotherapy, and music therapy. The review emphasises the importance of early intervention and family involvement in rehabilitation programmes.

Neuronal MeCP2 in the dentate gyrus regulates mossy fiber sprouting of mice with temporal lobe epilepsy

Sprouting of mossy fibers, one of the most consistent findings in tissue from patients with mesial temporal lobe epilepsy, exhibits several uncommon axonal growth features and has been considered a paradigmatic example of circuit plasticity that occurs in the adult brain. Clarifying the mechanisms responsible may provide new insight into epileptogenesis as well as axon misguidance in the central nervous system. Methyl-CpG-binding protein 2 (MeCP2) binds to methylated genomic DNA to regulate a range of physiological functions implicated in neuronal development and adult synaptic plasticity. However, exploring the potential role of MeCP2 in the documented misguidance of axons in the dentate gyrus has not yet been attempted. In this study, a status epilepticus-induced decrease of neuronal MeCP2 was observed in the dentate gyrus (DG). An essential regulatory role of MeCP2 in the development of functional mossy fiber sprouting (MFS) was confirmed through stereotaxic injection of a recombinant adeno-associated virus (AAV) to up- or down-regulate MeCP2 in the dentate neurons. Chromatin immunoprecipitation sequencing (ChIP-seq) was performed to identify the binding profile of native MeCP2 using micro-dissected dentate tissues. In both dentate tissues and HT22 cell lines, we demonstrated that MeCP2 could act as a transcription repressor on miR-682 with the involvement of the DNA methylation mechanism. Further, we found that miR-682 could bind to mRNA of phosphatase and tensin homolog (PTEN) in a sequence specific manner, thus leading to the suppression of PTEN and excessive activation of mTOR. This study therefore presents a novel epigenetic mechanism by identifying MeCP2/miR-682/PTEN/mTOR as an essential signal pathway in regulating the formation of MFS in the temporal lobe epileptic (TLE) mice. Significance statementUnderstanding the mechanisms that regulate axon guidance is important for a better comprehension of neural disorders. Sprouting of mossy fibers, one of the most consistent findings in patients with mesial temporal lobe epilepsy, has been considered a paradigmatic example of circuit plasticity in the adult brain. Although abnormal regulation of DNA methylation has been observed in both experimental rodents and humans with epilepsy, the potential role of DNA methylation in this well-documented example of sprouting of dentate axon remains elusive. This study demonstrates an essential role of methyl-CpG-binding protein 2 in the formation of mossy fiber sprouting. The underlying signal pathway has been also identified. The data hence provide new insight into epileptogenesis as well as axon misguidance in the central nervous system.

Rare variants in the MECP2 gene in girls with central precocious puberty

Rare variants in the MECP2 gene in girls with central precocious puberty

Effect of presentation rate on auditory processing in Rett syndrome: event-related potential study

BackgroundRett syndrome (RS) is a rare neurodevelopmental disorder characterized by mutations in the MECP2 gene. Patients with RS have severe motor abnormalities and are often unable to walk, use hands and speak. The preservation of perceptual and cognitive functions is hard to assess, while clinicians and care-givers point out that these patients need more time to process information than typically developing peers. Neurophysiological correlates of auditory processing have been also found to be distorted in RS, but sound presentation rates were relatively quick in these studies (stimulus onset asynchrony, SOA < 1000 ms). As auditory event-related potential (ERP) is typically increased with prolongation of SOA we aim to study if SOA prolongation might compensate for observed abnormalities.MethodsWe presented a repetitive stimulus (1000 Hz) at three different SOAs of 900 ms, 1800 ms, and 3600 ms in children with RS (N = 24, Mean age = 9.0 ± 3.1) and their typical development (TD) peers (N = 27, Mean age = 9.7 ± 3.4) while recording 28-channels electroencephalogram, EEG. Some RS participants (n = 10) did not show clear ERP and were excluded from the analysis.ResultsMajor ERP components (here assessed as N1P1 and P2N1 peak-to-peak values) were smaller at SOA 900 than at longer SOAs in both groups, pointing out that the basic mechanism of adaptation in the auditory system is preserved in at least in RS patients with evident ERPs. At the same time the latencies of these components were significantly delayed in the RS than in TD. Moreover, late components (P2N1 and N2P2) were drastically reduced in Rett syndrome irrespective of the SOA, suggesting a largely affected mechanism of integration of upcoming sensory input with memory. Moreover, developmental stagnation of auditory ERP characterized patients with RS: absence of typical P2N1 enlargement and P1 and N1 shortening with age at least for shortest SOA.LimitationsWe could not figure out the cause for the high percentage of no-evident ERP RS participants and our final sample of the RS group was rather small. Also, our study did not include a control clinical group.ConclusionsThus, auditory ERPs inform us about abnormalities within auditory processing that cannot be fully overcomed by slowing presentation rate.

OR04-06 Mkrn3, Dlk1 And Mecp2 Have Distinct Hypothalamic Expression Patterns Across Pubertal Maturation In Male And Female Mice

Abstract Disclosure: F.R. Tinano: None. S.A. Pereira: None. N.P. Boris: None. D.B. Macedo: None. A.P. Canton: None. A. Abreu: None. R.S. Carroll: None. A. Latronico: None. U.B. Kaiser: None. Context: Central precocious puberty (CPP) results from premature re-activation of the hypothalamic-pituitary-gonadal (HPG) axis. The most prevalent genetic cause of CPP is loss-of-function mutations in makorin ring finger 3 (MKRN3), with loss-of-function mutations in delta-like 1 homolog (DLK1) occurring less frequently. While the mechanisms by which MKRN3 regulates puberty onset have been partially elucidated in recent years, the manner by which DLK1 regulates HPG axis maturation remains unknown. Methyl CpG binding protein 2 (MeCP2) is associated with the neurodevelopmental Rett syndrome, with reports of early pubertal development among affected patients. Recently, rare variants in MeCP2 were identified in children with CPP with or without neurologic abnormalities. The pathways by which MECP2 may influence pubertal timing have not been determined. The aim of this study was to characterize Mkrn3, Dlk1 and Mecp2 expression patterns in the hypothalamus of male and female mice at different pubertal stages.Methods and Results: Male and female wild type C57BL/6 mice were euthanized at postnatal (P) age 10, 15, 22, 30 and 60 days. The mediobasal hypothalamus (MBH) and pre-optic area (POA) were isolated from the brains of each mouse. mRNA levels of Mkrn3, Dlk1 and Mecp2 were quantified by RT-qPCR and compared across the ages studied. Mkrn3 expression in both MBH and POA was highest at P10, then significantly lower at P15 and P22, remaining low until adulthood, with a similar pattern in male and female mice. In contrast, Dlk1 expression was higher at P60 compared to P22 in the MBH of male mice, while in female mice it was higher at P22 and P30 compared to P10. In the POA of male mice, Dlk1 expression was higher at P30 and P60 compared to P10, while no significant difference with age was seen in the POA of female mice. Mecp2 had higher expression in the MBH at P10 compared to P15 and P22 in male mice, and compared to P15, P30 and P60 in female mice. Mecp2 expression in the POA of both male and female mice was higher at P10 compared to all the other ages. No differences were observed in the hypothalamic expression of the three genes between male and female mice. Statistical significance was set at p &amp;lt; 0.05. Conclusions:Mkrn3 and Mecp2 had decreased hypothalamic expression in male and female mice with age, suggesting inhibitory roles on the HPG axis, consistent with the phenotype of CPP in patients with loss-of-function mutations in these genes. In contrast, hypothalamic expression of Dlk1 increased in both male and female mice toward adulthood, which is intriguing considering the association of loss-of-function mutations in this gene with CPP and suggests that the role of Dlk1 in the HPG axis is distinct from those of Mkrn3 and Mecp2. Defining the changes in hypothalamic expression of these three genes across pubertal development is critical to understanding their roles and mechanisms of action in regulating the HPG axis. Presentation: Thursday, June 15, 2023

Dendrimer nanotherapy targeting of glial dysfunction improves inflammation and neurobehavioral phenotype in adult female Mecp2-heterozygous mouse model of Rett syndrome.

Rett syndrome is an X-linked neurodevelopmental disorder caused by mutation of Mecp2 gene and primarily affects females. Glial cell dysfunction has been implicated in in Rett syndrome (RTT) both in patients and in mouse models of this disorder and can affect synaptogenesis, glial metabolism and inflammation. Here we assessed whether treatment of adult (5-6 months old) symptomatic Mecp2-heterozygous female mice with N-acetyl cysteine conjugated to dendrimer (D-NAC), which is known to target glia and modulate inflammation and oxidative injury, results in improved behavioral phenotype, sleep and glial inflammatory profile. We show that unbiased global metabolomic analysis of the hippocampus and striatum in adult Mecp2-heterozygous mice demonstrates significant differences in lipid metabolism associated with neuroinflammation, providing the rationale for targeting glial inflammation in this model. Our results demonstrate that treatment with D-NAC (10 mg/kg NAC) once weekly is more efficacious than equivalently dosed free NAC in improving the gross neurobehavioral phenotype in symptomatic Mecp2-heterozygous female mice. We also show that D-NAC therapy is significantly better than saline in ameliorating several aspects of the abnormal phenotype including paw clench, mobility, fear memory, REM sleep and epileptiform activity burden. Systemic D-NAC significantly improves microglial proinflammatory cytokine production and is associated with improvements in several aspects of the phenotype including paw clench, mobility, fear memory, and REM sleep, and epileptiform activity burden in comparison to saline-treated Mecp2-hetereozygous mice. Systemic glial-targeted delivery of D-NAC after symptom onset in an older clinically relevant Rett syndrome model shows promise in improving neurobehavioral impairments along with sleep pattern and epileptiform activity burden. These findings argue for the translational value of this approach for treatment of patients with Rett Syndrome.

Methylated Nucleotide-Based Proteolysis-Targeting Chimera Enables Targeted Degradation of Methyl-CpG-Binding Protein 2.

Methyl-CpG-binding protein 2 (MeCP2), a reader of DNA methylation, has been extensively investigated for its function in neurological and neurodevelopmental disorders. Emerging evidence indicates that MeCP2 exerts an oncogenic function in cancer; however, the endeavor to develop a MeCP2-targeted therapy remains a challenge. This work attempts to address it by introducing a methylated nucleotide-based targeting chimera termed methyl-proteolysis-targeting chimera (methyl-PROTAC). The methyl-PROTAC incorporates a methylated cytosine into an oligodeoxynucleotide moiety to recruit MeCP2 for targeted degradation in a von Hippel-Lindau- and proteasome-dependent manner, thus displaying antiproliferative effects in cancer cells reliant on MeCP2 overexpression. This selective cytotoxicity endows methyl-PROTAC with the capacity to selectively eliminate cancer cells that are addicted to the overexpression of the MeCP2 oncoprotein. Furthermore, methyl-PROTAC-mediated MeCP2 degradation induces apoptosis in cancer cells. These findings underscore the therapeutic potential of methyl-PROTAC to degrade undruggable epigenetic regulatory proteins. In summary, the development of methyl-PROTAC introduces an innovative strategy by designing a modified nucleotide-based degradation approach for manipulating epigenetic factors, thereby representing a promising avenue for the advancement of PROTAC-based therapeutics.

Parental age effects and Rett syndrome.

Rett syndrome (RTT) is a progressive neurodevelopmental disorder, and pathogenic Methyl-CpG-binding Protein 2 (MECP2) variants are identified in >95% of individuals with typical RTT. Most of RTT-causing variants in MECP2 are de novo and usually on the paternally inherited X chromosome. While paternal age has been reported to be associated with increased risk of genetic disorders, it is unknown whether parental age contributes to the risk of the development of RTT. Clinical data including parental age, RTT diagnostic status, and clinical severity are collected from 1226 participants with RTT and confirmed MECP2 variants. Statistical analyses are performed using Student t-test, single factor analysis of variance (ANOVA), and multi-factor regression. No significant difference is observed in parental ages of RTT probands compared to that of the general population. A small increase in parental ages is observed in participants with missense variants compared to those with nonsense variants. When we evaluate the association between clinical severity and parental ages by multiple regression analysis, there is no clear association between clinical severity and parental ages. Advanced parental ages do not appear to be a risk factor for RTT, and do not contribute to the clinical severity in individuals with RTT.

Non-canonical C-terminal variant of MeCP2 R344W exhibits enhanced degradation rate

Rett Syndrome (RTT) is a neurodevelopmental disorder caused by pathogenic variants in the MECP2 gene. While the majority of RTT-causing variants are clustered in the methyl-CpG binding domain and NCoR/SMRT interaction domain, we report a female patient with a functionally uncharacterized MECP2 variant in the C-terminal domain, c.1030C>T (R344W). We functionally characterized MECP2-R344W in terms of protein stability, NCoR/SMRT complex interaction, and protein nuclear localization in vitro. MECP2-R344W cells showed an increased protein degradation rate without significant change in NCoR/SMRT complex interaction and nuclear localization pattern, suggesting that enhanced MECP2 degradation is sufficient to cause a Rett Syndrome-like phenotype. This study highlights the pathogenicity of the C-terminal domain in Rett Syndrome, and demonstrates the potential of targeting MECP2 protein stability as a therapeutic approach.