MECP2 duplication syndrome (MDS) is an X-linked neurodevelopmental disorder caused by the gain of dose of at least the genes MECP2 and IRAK1 and is characterised by intellectual disability (ID), developmental delay, hypotonia, epilepsy and recurrent infections. It mainly affects males, and females can be affected or asymptomatic carriers. Rett syndrome (RTT) is mainly triggered by loss of function mutations in MECP2 and is a well described syndrome that presents ID, epilepsy, lack of purposeful hand use and impaired speech, among others. As a result of implementing omics technology, altered biological pathways in human RTT samples have been reported, but such molecular characterisation has not been performed in patients with MDS. We gathered human skin fibroblasts from 17 patients with MDS, 10 MECP2 duplication carrier mothers and 21 patients with RTT, and performed multi-omics (RNAseq and proteomics) analysis. Here, we provide a thorough description and compare the shared and specific dysregulated biological processes between the cohorts. We also highlight the genes TMOD2, SRGAP1, COPS2, CNPY2, IGF2BP1, MOB2, VASP, FZD7, ECSIT and KIF3B as biomarker and therapeutic target candidates due to their implication in neuronal functions. Defining the RNA and protein profiles has shown that our four cohorts are less alike than expected by their shared phenotypes.

Extracting common patterns of neural circuit computations in the autism spectrum and confirming them as a cause of specific core traits of autism is the first step toward identifying cell-level and circuit-level targets for effective clinical intervention. Studies in humans with autism have identified functional links and common anatomic substrates between core restricted behavioral repertoire, cognitive rigidity, and overstability of visual percepts during visual rivalry. To study these processes with single-cell precision and comprehensive neuronal population coverage, we developed the visual bistable perception paradigm for mice based on ambiguous moving plaid patterns consisting of two transparent gratings drifting at an angle of 120°. This results in spontaneous reversals of the perception between local component motion (plaid perceived as two separate moving grating components) and integrated global pattern motion (plaid perceived as a fused moving texture). This robust paradigm does not depend on the explicit report of the mouse, since the direction of the optokinetic nystagmus (OKN) is used to infer the dominant percept. Using this paradigm, we found that the rate of perceptual reversals between global and local motion interpretations is reduced in the methyl-CpG-binding protein 2 duplication syndrome (MECP2-ds) mouse model of autism. Moreover, the stability of local motion percepts is greatly increased in MECP2-ds mice at the expense of global motion percepts. Thus, our model reproduces a subclass of the core features in human autism (reduced rate of visual rivalry and atypical perception of visual motion). This further offers a well-controlled approach for dissecting neuronal circuits underlying these core features.

Recent advances in the understanding of neurodevelopmental disorders such as Rett syndrome (RTT) have enabled the discovery of novel therapeutic approaches that require formal clinical evaluation of efficacy. Clinical trial success depends on outcome measures that assess clinical features that are most impactful for affected individuals. To determine the top concerns in RTT and RTT-related disorders we asked caregivers to list the top caregiver concerns to guide the development and selection of appropriate clinical trial outcome measures for these disorders.
Caregivers of participants enrolled in the US Natural History Study of RTT and RTT-related disorders (n = 925) were asked to identify the top 3 concerning problems impacting the affected participant. We generated a weighted list of top caregiver concerns for each of the diagnostic categories and compared results between the disorders. Further, for classic RTT, caregiver concerns were analyzed by age, clinical severity, and common RTT-causing mutations in MECP2.
The top caregiver concerns for classic RTT were effective communication, seizures, walking/balance issues, lack of hand use, and constipation. The frequency of the top caregiver concerns for classic RTT varied by age, clinical severity, and specific mutations, consistent with known variation in the frequency of clinical features across these domains. Caregivers of participants with increased seizure severity often ranked seizures as the first concern, whereas caregivers of participants without active seizures often ranked hand use or communication as the top concern. Comparison across disorders found commonalities in the top caregiver concerns between classic RTT, atypical RTT, MECP2 duplication syndrome, CDKL5 deficiency disorder, and FOXG1 syndrome; however, distinct differences in caregiver concerns between these disorders are consistent with the relative prevalence and impact of specific clinical features.
The top caregiver concerns for individuals with RTT and RTT-related disorders reflect the impact of the primary clinical symptoms of these disorders. This work is critical in the development of meaningful therapies, as optimal therapy should address these concerns. Further, outcome measures to be utilized in clinical trials should assess these clinical issues identified as most concerning by caregivers.

UNASSIGNED: Recent advances in the understanding of neurodevelopmental disorders such as Rett syndrome (RTT) has enabled development of novel therapeutic approaches that are currently undergoing clinical evaluation or are proposed to move into clinical development. Clinical trial success depends on outcome measures that assess clinical features that are most impactful for affected individuals. To determine the top concerns in RTT and RTT-related disorders we asked caregivers to list the top clinical concerns in order to gain information to guide the development and selection of outcome measures for future clinical trials.
UNASSIGNED: Caregivers of participants enrolled in the US Natural History Study of RTT and related disorders were asked to identify the top 3 concerning problems impacting the affected participant. We generated a weighted list of top caregiver concerns for each of the diagnostic categories and compared results between the disorders. Further, for Classic RTT, caregiver concerns were analyzed by age, clinical severity, and common RTT-causing mutations in MECP2.
UNASSIGNED: The top caregiver concerns for Classic RTT were effective communication, seizures, walking/balance issues, lack of hand use, and constipation. The rank order of the frequency of the top caregiver concerns for Classic RTT varied by age, clinical severity, and specific mutations, consistent with known variation in the frequency of clinical features across these domains. The frequency of caregiver concern for seizures, hand use, and spoken language increased in relation to clinician assessed severity in these clinical domains, showing consistency between clinician assessments and caregiver concerns. Comparison across disorders found commonalities in the top caregiver concerns between Classic RTT, Atypical RTT, MECP2 Duplication Syndrome, CDKL5 Deficiency Disorder, and FOXG1 Syndrome; however, distinct differences in caregiver concerns between these disorders are consistent with the relative prevalence and impact of specific clinical features.
UNASSIGNED: The top caregiver concerns for individuals with RTT and the RTT-related disorders reflect the impact of the primary clinical symptoms of these disorders. This work is critical in the development of meaningful therapies, as optimal therapy should address these concerns. Further, outcome measures to be utilized in clinical trials should assess these clinical issues identified as most concerning by caregivers.

Transgenic animal models with homologous etiology provide a promising way to pursue the neurobiological substrates of the behavioral deficits in autism spectrum disorder (ASD). Gain-of-function mutations of MECP2 cause MECP2 duplication syndrome, a severe neurological disorder with core symptoms of ASD. However, abnormal brain developments underlying the autistic-like behavioral deficits of MECP2 duplication syndrome are rarely investigated. To this end, a human MECP2 duplication (MECP2-DP) rat model was created by the bacterial artificial chromosome transgenic method. Functional and structural magnetic resonance imaging (MRI) with high-field were performed on 16 male MECP2-DP rats and 15 male wildtype rats at postnatal 28 days, 42 days, and 56 days old. Multimodal fusion analyses guided by locomotor-relevant metrics and social novelty time separately were applied to identify abnormal brain networks associated with diverse behavioral deficits induced by MECP2 duplication. Aberrant functional developments of a core network primarily composed of the dorsal medial prefrontal cortex (dmPFC) and retrosplenial cortex (RSP) were detected to associate with diverse behavioral phenotypes in MECP2-DP rats. Altered developments of gray matter volume were detected in the hippocampus and thalamus. We conclude that gain-of-function mutations of MECP2 induce aberrant functional activities in the default-mode-like network and aberrant volumetric changes in the brain, resulting in autistic-like behavioral deficits. Our results gain critical insights into the biomarker of MECP2 duplication syndrome and the neurobiological underpinnings of the behavioral deficits in ASD.

Xq28 duplication syndrome (MIM# 300815) is a severe neurodevelopmental disorder in males due to MeCP2 overexpression. Most females with MECP2 duplication are asymptomatic carriers, but there are phenotypic heterogeneities. Skewed X-chromosome inactivation (XCI) can protect females from exhibiting clinical phenotypes. Herein we reported two asymptomatic females (mother and grandmother) with interstitial Xq28 duplication. AR and RP2 assays showed that both had extremely skewed XCI, the Xq28 duplicated chromosome was inactivated in the mother, but was surprisingly activated in the grandmother. Interestingly, by combining RNA sequencing and whole-exome sequencing, we confirmed that XIST only expressed in the Xq28 duplication chromosomes of the two females, indicating that the Xq28 duplication chromosomes were inactive. Meanwhile, MECP2 and most XCI genes in the duplicated X-chromosomes were not transcriptionally expressed or upregulated, precluding major clinical phenotypes in the two females, especially the grandmother. We showed that XCI status detected using RNA sequencing was more relevant for establishing the clinical phenotype of MECP2 duplication in females. It suggested that there were other factors maintaining the XCI status in addition to DNA methylation, a possible additional inhibition mechanism occurred at the transcriptional level in the unmethylated X-chromosome, counter balancing the MECP2 duplication\'s detrimental phenotype effects.

Methyl-CpG binding protein 2 (MeCP2) is a basic nuclear protein involved in the regulation of gene expression and microRNA processing. Duplication of MECP2-containing genomic segments causes MECP2 duplication syndrome, a severe neurodevelopmental disorder characterized by intellectual disability, motor dysfunction, heightened anxiety, epilepsy, autistic phenotypes, and early death. Reversal of the abnormal phenotypes in adult mice with MECP2 duplication (MECP2-TG) by normalizing the MeCP2 levels across the whole brain has been demonstrated. However, whether different brain areas or neural circuits contribute to different aspects of the behavioral deficits is still unknown. Here, we found that MECP2-TG mice showed a significant social recognition deficit, and were prone to display aversive-like behaviors, including heightened anxiety-like behaviors and a fear generalization phenotype. In addition, reduced locomotor activity was observed in MECP2-TG mice. However, appetitive behaviors and learning and memory were comparable in MECP2-TG and wild-type mice. Functional magnetic resonance imaging illustrated that the differences between MECP2-TG and wild-type mice were mainly concentrated in brain areas regulating emotion and social behaviors. We used the CRISPR-Cas9 method to restore normal MeCP2 levels in the medial prefrontal cortex (mPFC) and bed nuclei of the stria terminalis (BST) of adult MECP2-TG mice, and found that normalization of MeCP2 levels in the mPFC but not in the BST reversed the social recognition deficit. These data indicate that the mPFC is responsible for the social recognition deficit in the transgenic mice, and provide new insight into potential therapies for MECP2 duplication syndrome.

OBJECTIVE: The aim of this study was to assess the incidence and prevalence of MECP2 duplication syndrome in Australian children and further define its phenotype.
METHODS: The Australian Paediatric Surveillance Unit was used to identify children with MECP2 duplication syndrome between June 2014 and November 2017. Reporting clinicians were invited to complete a questionnaire. Clinician data (n = 20) were supplemented with information from the International Rett Syndrome Phenotype Database and from caregivers (n = 7). Birth prevalence and diagnostic incidence were calculated.
RESULTS: The birth prevalence of MECP2 duplication syndrome in Australia was 0.65/100 000 for all live births and 1/100 000 for males. Diagnostic incidence was 0.07/100 000 person-years overall and 0.12/100 000 person-years for males. The median age at diagnosis was 23.5 months (range 0 months-13 years). A history of pneumonia was documented in three quarters of the clinical cases, half of whom had more than nine episodes. Cardiovascular abnormalities were reported in three cases. A clinical vignette is presented for one child who died due to severe idiopathic pulmonary hypertension. The majority (13/15) of males had inherited the duplication from their mothers, and two had an unbalanced translocation.
CONCLUSIONS: MECP2 duplication syndrome is a rare but important diagnosis in children because of the burden of respiratory illness and recurrence risk. Pulmonary hypertension is a rare life-threatening complication. Array comparative genomic hybridisation testing is recommended for children with undiagnosed intellectual disability or global developmental delay. Early cardiac assessment and ongoing monitoring is recommended for MECP2 duplication syndrome.

Individuals with two or more copies of the MECP2 gene, located at Xq28, share clinical features and a distinct facial phenotype known as MECP2 Duplication syndrome. We have examined perinatal characteristics, early childhood development and medical co-morbidities in this disorder. The International Rett Syndrome Phenotype Database (InterRett), which collects information from caregivers and clinicians on individuals with Rett syndrome and MECP2 associated disorders, was used as the data source. Data were available on 56 cases (49 males and 7 females) with MECP2 Duplication syndrome. Median age at ascertainment was 7.9 years (range: 1.2-37.6 years) and at diagnosis 3.0 years (range: 3 weeks-37 years). Less than a third (29%) learned to walk. Speech deterioration was reported in 34% and only 20% used word approximations or better at ascertainment. Over half (55%) had been hospitalised for respiratory infections in the first 2 years of life. Just under half (44%) had seizures, occurring daily in nearly half of this group. The majority (89%) had gastrointestinal problems and a third had a gastrostomy. Following the recent demonstration of phenotype reversal in a mouse model of MECP2 Duplication, a clear understanding of the natural history is crucial to the design and implementation of future therapeutic strategies.

BACKGROUND: Chromosome Xq28 duplications encompassing methyl-CpG-binding protein 2 gene (MECP2) are observed most in males with a severe neurodevelopmental disorder associated with hypotonia, spasticity, severe learning disability, delayed psychomotor development, and recurrent pulmonary infections. Most female carriers are asymptomatic due to extremely or completely skewed X-inactivation.
METHODS: A retrospective clinical and molecular study was conducted to examine 16 patients and two fetuses from 10 families who were identified among patients with Xq28 duplications who presented at genetic clinics.
RESULTS: Of all 16 patients, 10 had a family history. Only one patient was female. All of the patients had no relevant pre-natal history. All of the patients exhibited severe psychomotor developmental delay, infantile hypotonia and recurrent infections. Some of the patients exhibited cardiac abnormalities, gastrointestinal mobility problems, hydrocele of tunica vaginalis, cryptorchidism, and autistic phenotypes. Additionally, neonatal kidney calculus, premature closure of the fontanel and pulmonary sequestration were found in the patients. Duplication sizes in these patients range from 0.21 to 14.391 Mb (most were smaller than 1 Mb), and all the duplications included host cell factor C1 (HCFC1), interleukin-1 receptor-associated kinase 1 (IRAK1), and MECP2. Bioinformatics analysis revealed that approximately half of the distal breakpoints were located within the low-copy repeats (LCRs), which may be involved in the recombination. The two fetuses were found to be healthy in the prenatal diagnosis.
CONCLUSIONS: This is the first large cohort of patients with MECP2 duplication syndrome, including a female, reported in China. Interestingly, neonatal kidney calculus, premature closure of the fontanel and pulmonary sequestration were first reported in this syndrome. However, it was difficult to distinguish if these patients represented unique cases or if these phenotypes can be considered as part of the syndrome. The correlation between the infrequent phenotypes and duplications/genes in the duplication region needs further systematic delineation. In conclusion, our study suggested that it is important to emphasize molecular genetic analysis in patients with developmental delay/intellectual disability and recurrent infections and that it is especially important for familial female carriers to accept prenatal diagnosis.