Common genetic variation in the Angelman syndrome imprinting centre affects the imprinting of chromosome 15

Roles of Epigenetics and Glial Cells in Drug-Induced Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by severe deficits in social communication and interaction, repetitive movements, abnormal focusing on objects, or activity that can significantly affect the quality of life of the afflicted. Neuronal and glial cells have been implicated. It has a genetic component but can also be triggered by environmental factors or drugs. For example, prenatal exposure to valproic acid or acetaminophen, or ingestion of propionic acid, can increase the risk of ASD. Recently, epigenetic influences on ASD have come to the forefront of investigations on the etiology, prevention, and treatment of this disorder. Epigenetics refers to DNA modifications that alter gene expression without making any changes to the DNA sequence. Although an increasing number of pharmaceuticals and environmental chemicals are being implicated in the etiology of ASD, here, we specifically focus on the molecular influences of the abovementioned chemicals on epigenetic alterations in neuronal and glial cells and their potential connection to ASD. We conclude that a better understanding of these phenomena can lead to more effective interventions in ASD.

Stem cell models of Angelman syndrome

Angelman syndrome (AS) is an imprinted neurodevelopmental disorder that lacks a cure, characterized by developmental delay, intellectual impairment, seizures, ataxia, and paroxysmal laughter. The condition arises due to the loss of the maternally inherited copy of the UBE3A gene in neurons. The paternally inherited UBE3A allele is unable to compensate because it is silenced by the expression of an antisense transcript (UBE3A-ATS) on the paternal chromosome. UBE3A, encoding enigmatic E3 ubiquitin ligase variants, regulates target proteins by either modifying their properties/functions or leading them to degradation through the proteasome. Over time, animal models, particularly the Ube3a mat-/pat+ Knock-Out (KO) mice, have significantly contributed to our understanding of the molecular mechanisms underlying AS. However, a shift toward human pluripotent stem cell models (PSCs), such as human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), has gained momentum. These stem cell models accurately capture human genetic and cellular characteristics, offering an alternative or a complement to animal experimentation. Human stem cells possess the remarkable ability to recapitulate neurogenesis and generate "brain-in-a-dish" models, making them valuable tools for studying neurodevelopmental disorders like AS. In this review, we provide an overview of the current state-of-the-art human stem cell models of AS and explore their potential to become the preclinical models of choice for drug screening and development, thus propelling AS therapeutic advancements and improving the lives of affected individuals.

Social attention and social-emotional modulation of attention in Angelman syndrome: an eye-tracking study

Individuals with Angelman syndrome (AS) present with severe intellectual disability alongside a social phenotype characterised by social communication difficulties and an increased drive for social engagement. As the social phenotype in this condition is poorly understood, we examined patterns of social attention and social modulation of attention in AS. Twenty-four individuals with AS and twenty-one young children with similar mental age were shown videos featuring unfamiliar actors who performed simple actions across two conditions: a playful condition, in which the actor showed positive facial emotions, and a neutral condition, in which the actor showed a neutral facial expression. During the passive observation of the videos, participants' proportion of time spent watching the two areas of interest (faces and actions) was examined using eye-tracking technology. We found that the playful condition elicited increased proportion of fixations duration to the actor's face compared to the neutral condition similarly across groups. Additionally, the proportion of fixations duration to the action area was similar across groups in the two conditions. However, children with AS looked towards the actor's face for a shorter duration compared to the comparison group across conditions. This pattern of similarities and differences provides novel insight on the complex social phenotype of children with AS.

Identification of differentially methylated regions in rare diseases from a single-patient perspective

BACKGROUND

DNA methylation (5-mC) is being widely recognized as an alternative in the detection of sequence variants in the diagnosis of some rare neurodevelopmental and imprinting disorders. Identification of alterations in DNA methylation plays an important role in the diagnosis and understanding of the etiology of those disorders. Canonical pipelines for the detection of differentially methylated regions (DMRs) usually rely on inter-group (e.g., case versus control) comparisons. However, these tools might perform suboptimally in the context of rare diseases and multilocus imprinting disturbances due to small cohort sizes and inter-patient heterogeneity. Therefore, there is a need to provide a simple but statistically robust pipeline for scientists and clinicians to perform differential methylation analyses at the single patient level as well as to evaluate how parameter fine-tuning may affect differentially methylated region detection.

RESULT

We implemented an improved statistical method to detect differentially methylated regions in correlated datasets based on the Z-score and empirical Brown aggregation methods from a single-patient perspective. To accurately assess the predictive power of our method, we generated semi-simulated data using a public control population of 521 samples and investigated how the size of the control population, methylation difference, and region size affect DMR detection. In addition, we validated the detection of methylation events in patients suffering from rare multi-locus imprinting disturbance and evaluated how this method could complement existing tools in the context of clinical diagnosis.

CONCLUSION

In this study, we present a robust statistical method to perform differential methylation analysis at the single patient level and describe its optimal parameters to increase DMRs identification performance. Finally, we show its diagnostic utility when applied to rare disorders.

Genomic Investigation of Infantile and Childhood Epileptic Encephalopathies in Kazakhstan: An Urgent Priority

Objectives: Infantile and childhood epileptic encephalopathies are a group of severe epilepsies that begin within the first year of life and often portend increased morbidity. Many of them are genetically determined. The medical strategy for their management depends on the genetic cause. There are no facilities for genetic testing of children in Kazakhstan but we have a collection of data with already defined genes responsible for clinical presentations.

Methods: We analyzed children with epileptic encephalopathies that began in the first 3 years of life and were accompanied by a delay/arrest of intellectual development, in the absence of structural changes in the brain. Such patients were recommended to undergo genetic testing using epileptic genetic panels in laboratories in different countries.

Results: We observed 350 infants with clinical presentation of epileptic encephalopathies. 4.3% of them followed our recommendations and underwent genetic testing privately. In total 12/15 children became eligible for targeted treatment, 3/15 were likely to have non-epileptic stereotypies/movements, 2/15 were unlikely to respond to any therapy and all had a high chance of intellectual disability, behavioral and social communication disorders.

Conclusion: The genetic results of 15/350 (4.3% of patients) have demonstrated the potential and enormous impact from gene panel analysis in management of epileptic encephalopathy. Availability of genetic testing within the country will improve management of children with genetic epilepsies and help to create a local database of pathogenic variants.

Long Noncoding RNA SNHG14 Promotes Ischemic Brain Injury via Regulating miR-199b/AQP4 Axis

BACKGROUND

Ischemic stroke is the leading cause of disability worldwide. Long noncoding RNAs (lncRNAs) play important roles in the pathogenesis of cerebral ischemia. This study aimed to investigate the role and mechanism of lncRNA small nucleolar RNA host gene 14 (SNHG14) in ischemic brain injury.

METHODS

Cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) in mice. The expression of SNHG14 in MCAO mouse model was detected by quantitative real-time PCR (qRT-PCR). The levels of SNHG14, microRNA-199b (miR-199b) and aquaporin 4 (AQP4) in oxygen-glucose deprivation (OGD)-stimulated BV2 cells were determined by qRT-PCR or western blot assay. Cell proliferation and apoptosis were assessed by Cell Counting Kit-8 (CCK-8) assay and flow cytometry. The levels of pro-inflammatory cytokines were measured by enzyme-linked immunosorbent assay (ELISA). The levels of oxidative stress markers were examined using commercial kits. The relationships among SNHG14, miR-199b and AQP4 were confirmed by dual-luciferase reporter assay, RNA immunoprecipitation assay and RNA pull-down assay.

RESULTS

SNHG14 was up-regulated in MCAO mouse model. Depletion of SNHG14 lessened cerebral ischemia in MCAO mouse model. SNHG14 silencing inhibited inflammation and oxidative stress in OGD-exposed BV2 cells. MiR-199b level was decreased, while AQP4 level was increased in OGD-treated BV2 cells. Knockdown of miR-199b reversed the effect of SNHG14 knockdown on ischemic damage in OGD-stimulated BV2 cells. Moreover, AQP4 overexpression abolished the effect of miR-199b on ischemic injury in OGD-treated BV2 cells. Furthermore, SNHG14 indirectly regulate AQP4 expression by sponging miR-199b.

CONCLUSIONS

Knockdown of SNHG14 attenuated ischemic brain injury by inhibiting inflammation and oxidative stress through the miR-199b/AQP4 axis.

Epigenetics in Prader-Willi Syndrome

Prader-Willi Syndrome (PWS) is a rare neurodevelopmental disorder that affects approximately 1 in 20,000 individuals worldwide. Symptom progression in PWS is classically characterized by two nutritional stages. Stage 1 is hypotonia characterized by poor muscle tone that leads to poor feeding behavior causing failure to thrive in early neonatal life. Stage 2 is followed by the development of extreme hyperphagia, also known as insatiable eating and fixation on food that often leads to obesity in early childhood. Other major features of PWS include obsessive-compulsive and hoarding behaviors, intellectual disability, and sleep abnormalities. PWS is genetic disorder mapping to imprinted 15q11.2-q13.3 locus, specifically at the paternally expressed SNORD116 locus of small nucleolar RNAs and noncoding host gene transcripts. SNORD116 is processed into several noncoding components and is hypothesized to orchestrate diurnal changes in metabolism through epigenetics, according to functional studies. Here, we review the current status of epigenetic mechanisms in PWS, with an emphasis on an emerging role for SNORD116 in circadian and sleep phenotypes. We also summarize current ongoing therapeutic strategies, as well as potential implications for more common human metabolic and psychiatric disorders.

Imitation in Angelman syndrome: the role of social engagement

Individuals with Angelman syndrome (AS) are characterized by severe cognitive impairments alongside an enhanced drive for social engagement. As knowledge on imitation skills in this population is limited, we conducted the first controlled study of imitation in AS. We examined how 23 individuals with AS and 21 typically developing young children with similar mental age imitated novel actions in response to socially or non-socially engaging models, and in response to video-recorded versus live demonstrations of novel actions. Individuals with AS imitated as frequently and as accurately as typical young children in response to live demonstrations; but they imitated less frequently and less accurately in response to video-recorded demonstrations. Further, imitation was modulated by whether the demonstrator was socially engaging or emotionally neutral in the AS group, while this modulation was not present in the comparison group. Individuals with higher mental age imitated more frequently and more accurately across groups. Imitation performance in AS appears to be more modulated by the social context compared to typical infants and young children with similar mental age, possibly reflecting an enhanced drive for social engagement. A socially engaging instructional style might facilitate imitative learning in this population.