Rare single nucleotide polymorphisms in the regulatory regions of the superoxide dismutase genes in autism spectrum disorder

UBE3A: The Role in Autism Spectrum Disorders (ASDs) and a Potential Candidate for Biomarker Studies and Designing Therapeutic Strategies

Published reports from the CDC's Autism and Development Disabilities Monitoring Networks have shown that an average of 1 in every 44 (2.3%) 8-year-old children were estimated to have ASD in 2018. Many of the ASDs exhibiting varying degrees of autism-like phenotypes have chromosomal anomalies in the Chr15q11-q13 region. Numerous potential candidate genes linked with ASD reside in this chromosomal segment. However, several clinical, in vivo, and in vitro studies selected one gene more frequently than others randomly and unbiasedly. This gene codes for UBE3A or Ubiquitin protein ligase E3A [also known as E6AP ubiquitin-protein ligase (E6AP)], an enzyme involved in the cellular degradation of proteins. This gene has been listed as one of the several genes with a high potential of causing ASD in the Autism Database. The gain of function mutations, triplication, or duplication in the UBE3A gene is also associated with ASDs like Angelman Syndrome (AS) and Dup15q Syndrome. The genetic imprinting of UBE3A in the brain and a preference for neuronal maternal-specific expression are the key features of various ASDs. Since the UBE3A gene is involved in two main important diseases associated with autism-like symptoms, there has been widespread research going on in understanding the link between this gene and autism. Additionally, since no universal methodology or mechanism exists for identifying UBE3A-mediated ASD, it continues to be challenging for neurobiologists, neuroscientists, and clinicians to design therapies or diagnostic tools. In this review, we focus on the structure and functional aspects of the UBE3A protein, discuss the primary relevance of the 15q11-q13 region in the cause of ASDs, and highlight the link between UBE3A and ASD. We try to broaden the knowledge of our readers by elaborating on the possible mechanisms underlying UBE3A-mediated ASDs, emphasizing the usage of UBE3A as a prospective biomarker in the preclinical diagnosis of ASDs and discuss the positive outcomes, advanced developments, and the hurdles in the field of therapeutic strategies against UBE3A-mediated ASDs. This review is novel as it lays a very detailed and comprehensive platform for one of the most important genes associated with diseases showing autistic-like symptoms. Additionally, this review also attempts to lay optimistic feedback on the possible steps for the diagnosis, prevention, and therapy of these UBE3A-mediated ASDs in the upcoming years.

The Role of Oxidative Stress in Autism Spectrum Disorder: A Narrative Literature Review

Autism spectrum disorder (ASD) is a multifaceted neurodevelopmental disorder that comprises a complex aetiology, where a genetic component has been suggested, together with multiple environmental risk factors. Because of its increasing incidence in the paediatric population and the lack of successful curative therapies, ASD is one of the most puzzling disorders for medicine. In the last two decades and more, the relationship between oxidative stress (OS) and ASD has been recurrently documented. For this reason, the former hypothesis, according to which reactive oxygen and nitrogen species (ROS and RNS) play an important role in ASD, is now a certainty. Thus, in this review, we will discuss many aspects of the role of OS in ASD. In addition, we will describe, in the context of the most recent literature, the possibility that free radicals promote lipid peroxidation, as well as an increase in other OS biomarkers. Finally, we will outline the possibility of novel nutritional interventions aimed at counteracting ROS production in people with ASD. In fact, new strategies have investigated the possibility that ASD symptoms, as well behavioral anomalies, may be improved after interventions using antioxidants as supplements or included in foods.

Heterozygous NPR2 Variants in Idiopathic Short Stature

Heterozygous variants in the NPR2 gene, which encodes the B-type natriuretic peptide receptor (NPR-B), a regulator of skeletal growth, were reported in 2-6% cases of idiopathic short stature (ISS). Using next-generation sequencing (NGS), we aimed to assess the frequency of NPR2 variants in our study cohort consisting of 150 children and adolescents with ISS, describe the NPR2 phenotypic spectrum with a growth pattern including birth data, and study the response to growth hormone (GH) treatment. A total of ten heterozygous pathogenic/likely pathogenic NPR2 variants and two heterozygous NPR2 variants of uncertain significance were detected in twelve participants (frequency of causal variants: 10/150, 6.7%). During follow-up, the NPR2 individuals presented with a growth pattern varying from low-normal to significant short stature. A clinically relevant increase in BMI (a mean gain in the BMI SDS of +1.41), a characteristic previously not reported in NPR2 individuals, was observed. In total, 8.8% participants born small for their gestational age (SGA) carried the NPR2 causal variant. The response to GH treatment was variable (SDS height gain ranging from -0.01 to +0.74). According to the results, NPR2 variants present a frequent cause of ISS and familial short stature. Phenotyping variability in growth patterns and variable responses to GH treatment should be considered.

Superoxide dismutase isozymes in cerebral organoids from autism spectrum disorder patients

Autism spectrum disorder is a pervasive neurodevelopmental disorder with a substantial contribution to the global disease burden. Despite intensive research efforts, the aetiopathogenesis remains unclear. The Janus-faced antioxidant enzymes superoxide dismutase 1-3 have been implicated in initiating oxidative stress and as such may constitute a potential therapeutic target. However, no measurement has been taken in human autistic brain samples. The aim of this study is to measure superoxide dismutase 1-3 in autistic cerebral organoids as an in vitro model of human foetal neurodevelopment. Whole brain organoids were created from induced pluripotent stem cells from healthy individuals (n = 5) and individuals suffering from autism (n = 4). Using Pierce bicinchoninic acid and enzyme-linked immunosorbent assays, the protein and superoxide dismutase 1, 2, and 3 concentrations were quantified in the cerebral organoids at days 22, 32, and 42. Measurements were normalized to the protein concentration. Results represented using medians and interquartile ranges. Using Wilcoxon matched-pairs signed-rank test, an abrupt rise in the superoxide dismutase concentration was observed at day 32 and onwards. Using Wilcoxon rank-sum test, no differences were observed between healthy (SOD1: 35.56 ng/mL ± 3.46; SOD2: 2435.80 ng/mL ± 1327.00; SOD3: 1854.88 ng/mL ± 867.94) and autistic (SOD1: 32.85 ng/mL ± 5.26; SOD2: 2717.80 ng/mL ± 1889.10; SOD3: 1690.18 ng/mL ± 615.49) organoids. Cerebral organoids recapitulate many aspects of human neurodevelopment, but the diffusion restriction may render efforts in modelling differences in oxidative stress futile due to the intrinsic hypoxia and central necrosis.

Identification of Chromosomal Regions Linked to Autism-Spectrum Disorders: A Meta-Analysis of Genome-Wide Linkage Scans

Background: Autism spectrum disorder (ASD) is a clinically and genetically heterogeneous group of pervasive neurodevelopmental disorders with a strong hereditary component. Although, genome-wide linkage scans (GWLS) and association studies (GWAS) have previously identified hundreds of ASD risk gene loci, the results remain inconclusive. Method: We performed a heterogeneity-based genome search meta-analysis (HEGESMA) of 15 genome scans of autism and ASD. Results: For strictly defined autism, data were analyzed across six separate genome scans. Region 7q22-q34 reached statistical significance in both weighted and unweighted analyses, with evidence of significantly low between-scan heterogeneity. For ASDs (data from 12 separate scans), chromosomal regions 5p15.33-5p15.1 and 15q22.32-15q26.1 reached significance in both weighted and unweighted analyses but did not reach significance for either low or high heterogeneity. Region 1q23.2-1q31.1 was significant in unweighted analyses with low between-scan heterogeneity. Finally, region 8p21.1-8q13.2 reached significant linkage peak in all our meta-analyses. When we combined all available genome scans (15), the same results were produced. Conclusions: This meta-analysis suggests that these regions should be further investigated for autism susceptibility genes, with the caveat that autism spectrum disorders have different linkage signals across genome scans, possibly because of the high genetic heterogeneity of the disease.

Re-emerging concepts of immune dysregulation in autism spectrum disorders

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by communication and social interaction deficits, and by restricted interests and stereotyped, repetitive behavior patterns. ASD has a strong genetic component and a complex architecture characterized by the interplay of rare and common genetic variants. Recently, increasing evidence suggest a significant contribution of immune system dysregulation in ASD. The present paper reviews the latest updates regarding the altered immune landscape of this complex disorder highlighting areas with potential for biomarkers discovery as well as personalization of therapeutic approaches. Cross-talk between the central nervous system and immune system has long been envisaged and recent evidence brings insights into the pathways connecting the brain to the immune system. Disturbance of cytokine levels plays an important role in the establishment of a neuroinflammatory milieu in ASD. Several other immune molecules involved in antigen presentation and inflammatory cellular phenotypes are also at play in ASD. Maternal immune activation, the presence of brain-reactive antibodies and autoimmunity are other potential prenatal and postnatal contributors to ASD pathophysiology. The molecular players involved in oxidative-stress response and mitochondrial system function, are discussed as contributors to the pro-inflammatory pattern. The gastrointestinal inflammation pathways proposed to play a role in ASD are also discussed. Moreover, the body of evidence regarding some of the genetic factors linked to the immune system dysregulation is reviewed and discussed. Last, but not least, the epigenetic traits and their interactions with the immune system are reviewed as an expanding field in ASD research. Understanding the immune-mediated pathways that influence brain development and function, metabolism, and intestinal homeostasis, may lead to the identification of robust diagnostic or predictive biomarkers for ASD individuals. Thus, novel therapeutic approaches could be developed, ultimately aiming to improve their quality of life.

Oxidative Stress in Adults with Autism Spectrum Disorder: A Case Control Study

Oxidative stress has been proposed as being important in the pathophysiology of autism spectrum disorders (ASD), and heightened levels of oxidative stress has found in children with ASD. Our aim was to investigate, whether this change is temporary or persist into adulthood. We included 89 adult patients with ASD and sex and age matched controls. Plasma levels of antioxidants superoxide dismutase 1 (SOD1) and superoxide dismutase 2 (SOD2) and pro-oxidant xanthine oxidase (XO) were measured. Individuals with ASD had higher levels of SOD1, which furthermore correlated with autism severity as measured by autism quotient-score. We found no difference regarding SOD2 and XO between ASD group and controls. However, SOD1 and SOD2 were elevated in males compared to females.

Mutation screening of the UBE3A gene in Chinese Han population with autism

BACKGROUND

15q11-13 region is one of the most complex chromosomal regions in the human genome. UBE3A is an important candidate gene of autism spectrum disorder (ASD), which located at the 15q11-13 region and encodes ubiquitin-protein ligase E3A. Previous studies about UBE3A gene and ASD have shown inconsistent results and few studies were performed in Chinese population. This study aimed to detect the genetic mutations of UBE3A gene in Chinese Han population with ASD and analyze genetic association between these variants and ASD.

METHODS

The samples consisted of 192 patients with autism according to the DSM-IV diagnostic criteria and 192 healthy controls. We searched for mutations at coding sequence (CDS) regions and their adjacent non-coding regions of UBE3A gene using the high resolution melting (HRM) and Sanger sequencing methods. We further increased sample size to validate the detected variants using HRM and conducted association analysis between case and control groups.

RESULTS

A known single nucleotide polymorphism (T > C, rs150331504) located at the CDS4 and a known 5 bp insertion/deletion variation (AACTC+/-, rs71127053) located at the intron region of the upstream 288 bp of the CDS2 of UBE3A gene were detected using Sanger sequencing method. The ASD samples of case group were 391 for rs71127053, 384 for rs150331504 and 384 healthy controls, which were used to make an association analysis. The results of association analysis suggested that there were no significant difference about the allele and genotype frequencies of rs71127053 and rs150331504 between case and control groups after extending the sample size. Besides, rs150331504 is a synonymous mutation and we compared the secondary structure and minimum free energy (MFE) of mRNA harboring the allele T or C of rs150331504 using RNAfold software. We found that the centroid secondary structure apparently differs along with the polymorphisms of rs150331504 T > C, the results suggested that this variant might change the secondary structure of mRNA of UBE3A gene. We did not detect mutations in other coding regions of UBE3A gene.

CONCLUSIONS

These findings showed that UBE3A gene might not be a major disease gene in Chinese ASD cases.

Oxidative stress, metabolic and mitochondrial abnormalities associated with autism spectrum disorder

Autism spectrum disorder is a neurodevelopmental disorder characterized by impaired development and by abnormal function in regards to social interaction, communication and restricted, repetitive behavior. It affects approximately 1% of the worldwide population. Like other psychiatric disorders the diagnosis is based on observation of, and interview with the patient and next of kin, and diagnostic tests. Many genes have been associated with autism, but only few highly penetrant. Some researchers have instead focused on oxidative stress, metabolic abnormalities and mitochondrial dysfunction as an explanation of the disorder. Currently no cure exists for the disorder, making these abnormalities interesting as they are possibly correctable with supplements or treatment. These various processes cannot be seen independently as they are influencing and interacting with each other. Furthermore many of the metabolic changes seen in autism have also been shown in other psychiatric disorders such as attention deficit hyperactivity disorder, schizophrenia and bipolar disorder along with often comorbid disorders like epilepsy and intellectual disability. As such some of these abnormalities are not specific, however, could indicate a similar mechanism for the development of these disorders, with symptomatology and severity varying according to the location and the amount of damage done to proteins, cells and DNA. Clinical studies trying to treat these abnormalities, have widely been successful in correcting the metabolic abnormalities seen, but only some studies have also shown bettering of autistic symptoms. Hopefully with increased knowledge of the pathophysiology of the disorder, future preventive measures or treatment can be developed.

High frequency of pathogenic ACAN variants including an intragenic deletion in selected individuals with short stature

CONTEXT

Defining the underlying etiology of idiopathic short stature (ISS) improves the overall management of an individual.

OBJECTIVE

To assess the frequency of pathogenic ACAN variants in selected individuals.

DESIGN

The single-center cohort study was conducted at a tertiary university children's hospital. From 51 unrelated patients with ISS, the 16 probands aged between 3 and 18 years (12 females) with advanced bone age and/or autosomal dominant inheritance pattern of short stature were selected for the study. Fifteen family members of ACAN-positive probands were included. Exome sequencing was performed in all probands, and additional copy number variation (CNV) detection was applied in selected probands with a distinct ACAN-associated phenotype.

RESULTS

Systematic phenotyping of the study cohort yielded 37.5% (6/16) ACAN-positive probands, with all novel pathogenic variants, including a 6.082 kb large intragenic deletion, detected by array comparative genomic hybridization (array CGH) and exome data analysis. All variants were co-segregated with short stature phenotype, except in one family member with the intragenic deletion who had an unexpected growth pattern within the normal range (-0.5 SDS). One patient presented with otosclerosis, a sign not previously associated with aggrecanopathy.

CONCLUSIONS

ACAN pathogenic variants presented a common cause of familial ISS. The selection criteria used in our study were suggested for a personalized approach to genetic testing of the ACAN gene in clinical practice. Our results expanded the number of pathogenic ACAN variants, including the first intragenic deletion, and suggested CNV evaluation in patients with typical clinical features of aggrecanopathy as reasonable. Intra-familial phenotypic variability in growth patterns should be considered.

Maternal diabetes induces autism-like behavior by hyperglycemia-mediated persistent oxidative stress and suppression of superoxide dismutase 2

Hyperglycemia induces persistent oxidative stress and superoxide dismutase 2 (SOD2) suppression in neurons. SOD2 suppression is caused by oxidative stress-mediated histone methylation and subsequent dissociation of Egr1 on the SOD2 promoter. Maternal diabetes induces autism-like behavior in offspring with SOD2 suppression in the amygdala in rats, while SOD2 overexpression in the amygdala ameliorates autism-like behavior. Postnatal treatment of the blood–brain barrier-permeable antioxidant resveratrol partly restores this effect. This study describes a potential mechanism for maternal diabetes-induced autism-like behavior in offspring.

Epidemiological studies show that maternal diabetes is associated with an increased risk of autism spectrum disorders (ASDs), although the detailed mechanisms remain unclear. The present study aims to investigate the potential effect of maternal diabetes on autism-like behavior in offspring. The results of in vitro study showed that transient hyperglycemia induces persistent reactive oxygen species (ROS) generation with suppressed superoxide dismutase 2 (SOD2) expression. Additionally, we found that SOD2 suppression is due to oxidative stress-mediated histone methylation and the subsequent dissociation of early growth response 1 (Egr1) on the SOD2 promoter. Furthermore, in vivo rat experiments showed that maternal diabetes induces SOD2 suppression in the amygdala, resulting in autism-like behavior in offspring. SOD2 overexpression restores, while SOD2 knockdown mimics, this effect, indicating that oxidative stress and SOD2 expression play important roles in maternal diabetes-induced autism-like behavior in offspring, while prenatal and postnatal treatment using antioxidants permeable to the blood–brain barrier partly ameliorated this effect. We conclude that maternal diabetes induces autism-like behavior through hyperglycemia-mediated persistent oxidative stress and SOD2 suppression. Here we report a potential mechanism for maternal diabetes-induced ASD.

Brain protein changes in Mecp2 mouse mutant models: Effects on disease progression of Mecp2 brain specific gene reactivation

Rett syndrome (RTT) is a leading cause of severe intellectual disability in females, caused by de novo loss-of function mutations in the X-linked methyl-CpG binding protein 2 (MECP2). To better investigate RTT disease progression/pathogenesis animal models of Mecp2 deficiency have been developed. Here, Mecp2 mouse models are employed to investigate the role of protein patterns in RTT. A proteome analysis was carried out in brain tissue from i) Mecp2 deficient mice at the pre-symptomatic and symptomatic stages and, ii) mice in which the disease phenotype was reversed by Mecp2 reactivation. Several proteins were shown to be differentially expressed in the pre-symptomatic (n = 18) and symptomatic (n = 20) mice. Mecp2 brain reactivated mice showed wild-type comparable levels of expression for twelve proteins, mainly related to proteostasis (n = 4) and energy metabolic pathways (n = 4). The remaining ones were found to be involved in redox homeostasis (n = 2), nitric oxide regulation (n = 1), neurodevelopment (n = 1). Ten out of twelve proteins were newly linked to Mecp2 deficiency. Our study sheds light on the relevance of the protein-regulation of main physiological process in the complex mechanisms leading from Mecp2 mutation to the RTT clinical phenotype. SIGNIFICANCE: We performed a proteomic study of a Mecp2^stop/y mouse model for Rett syndrome (RTT) at the pre-symptomatic and symptomatic Mecp2 deficient mice stage and for the brain specific reactivated Mecp2 model. Our results reveal major protein expression changes pointing out to defects in proteostasis or energy metabolic pathways other than, to a lesser extent, in redox homeostasis, nitric oxide regulation or neurodevelopment. The Mecp2 mouse rescued model provides the possibility to select target proteins more susceptible to the Mecp2 gene mutation, potential and promising therapeutical targets.

Redox Mechanisms in Migraine: Novel Therapeutics and Dietary Interventions

SIGNIFICANCE

Migraine represents the third most prevalent and the seventh most disabling human disorder. Approximately 30% of migraine patients experience transient, fully reversible, focal neurological symptoms (aura) preceding the attack. Recent Advances: Awareness of the hypothesis that migraine actually embodies a spectrum of illnesses-ranging from episodic to chronic forms-is progressively increasing and poses novel challenges for clarifying the underlying pathophysiological mechanisms of migraine as well as for the development of novel therapeutic interventions. Several theories have evolved to the current concept that a combination of genetic, epigenetic, and environmental factors may play a role in migraine pathogenesis, although their relative importance is still being debated.

CRITICAL ISSUES

One critical issue that deserves a particular attention is the role of oxidative stress in migraine. Indeed, potentially harmful oxidative events occur during the migraine attack and long-lasting or frequent migraine episodes may increase brain exposure to oxidative events that can lead to chronic transformation. Moreover, a wide variety of dietary, environmental, physiological, behavioral, and pharmacological migraine triggers may act through oxidative stress, with clear implications for migraine treatment and prophylaxis. Interestingly, almost all current prophylactic migraine agents exert antioxidant effects.

FUTURE DIRECTIONS

Increasing awareness of the role of oxidative stress and/or decreased antioxidant defenses in migraine pathogenesis and progression to a chronic condition lays the foundations for the design of novel prophylactic approaches, which, by reducing brain oxidative phenomena, could favorably modify the clinical course of migraine. Antioxid. Redox Signal. 28, 1144-1183.

Discovering the Unexpected with the Utilization of NGS in Diagnostics of Non-syndromic Hearing Loss Disorders: The Family Case of ILDR1-Dependent Hearing Loss Disorder

Sensorineural hearing loss (SNHL) is a heterogeneous family of hearing disabilities with congenital (including genetic) as well as acquired etiology. Congenital SNHL of genetic etiology is further sub-divided into autosomal dominant, autosomal recessive and X-linked SNHL. More than 60 genes are involved in the etiology of autosomal recessive non-syndromic hearing loss (ARNSHL) commonly manifesting as heterogeneous pre-lingual profound to severe non-progressive clinical phenotype. ILDR1-dependent ARNSHL (DFNB42, OMIM: # 609646) is a very rare sub-type of hearing disability, with unknown prevalence, caused by function-damaging genetic variants in ILDR1 gene reported in families of Middle-Eastern origin. ILDR1 (Immunoglobulin-Like Domain-containing Receptor 1) is involved in the development of semicircular canal, tricellular tight junction and auditory hair cells. An apparently non-consanguineous family of European ancestry with two affected siblings with profound progressive hearing loss characterized in their infancy and successfully treated with cochlear implants (CI) is presented. Genetic analysis of common ARNSHL genetic causes in the population of origin was negative, thus the next-generation sequencing (NGS) and family segregation analysis to identify underlying causative genetic variant was performed. Unexpectedly and atypical for the population of origin a homozygous non-sense variant ILDR1 c.942C > A (p.Cys314Ter) inherited from both heterozygous parents was identified in both patients. Contrary to the commonly reported phenotype, indices of a progressive hearing loss and potential compensatory mechanism of vestibular function were revealed with the analysis of clinical data. The utilization of NGS was demonstrated as an invaluable tool for the detection of atypical rare variants in diagnostics of unidentified hearing loss disorders.

Genetic and Epigenetic Mechanisms Linking Air Pollution and Congenital Heart Disease

Epidemiological studies strongly suggest that parental air pollutants exposure during the periconceptional period may play a major role in causing fetal/newborn malformations, including a frequent heterogeneity in the methods applied and a difficulty in estimating the clear effect of environmental toxicants. Moreover, only some couples exposed to toxicants during the pre-conception period give birth to a child with congenital anomalies. The reasons for such phenomena remain elusive but they can be explained by the individual, innate ability to metabolize these contaminants that eventually defines the ultimate dose of a biological active toxicant. In this paper, we reviewed the major evidence regarding the role of parental air pollutant exposure on congenital heart disease (CHD) risk as well as the modulating effect on detoxification systems. Finally, major epigenetic alterations induced by adverse environment contaminants have been revised as possible mechanisms altering a correct heart morphogenesis.

Reduced endogenous urinary total antioxidant power and its relation of plasma antioxidant activity of superoxide dismutase in individuals with autism spectrum disorder

Individuals with autism spectrum disorders (ASD) have impaired detoxification capacity. Investigating　the neurobiological bases of　impaired antioxidant capacity is thus a research priority in the pathophysiology of ASD.　We measured　the urinary levels of hexanoyl-lysine (HEL) which is a new oxidative stress　biomarker, total antioxidant power (TAP) and DNA methylation biomarker 8-hydroxy-2'-deoxyguanosine (8-OHdG), and the plasma levels of superoxide dismutase (SOD), which is a major antioxidant enzyme. We examined whether the urinary levels of these enzymes and biomarkers may be related to symptoms of social impairment in 20 individuals with ASD (meanage,11.1±5.2years) and 12 age- and gender-matched healthy controls (meanage,14.3±6.2years). Symptoms of social impairment were　assessed using the Social Responsiveness Scale (SRS). The dietary TAP of the fruit juice, chocolate, cookies, biscuits, jam and marmalade were significantly higher in the ASD group than in the control group, although the intake of nutrients was not significantly different between the groups. The urinary TAP levels were significantly lower in the ASD group than in the control group. There were no significantly differences in urinary HEL and 8-OHdG levels between the ASD and control groups. The SRS scores were significantly higher in the ASD group than in the control group. Stepwise regression analysis revealed that urinary TAP levels and plasma SOD levels can differences in the biomarkers and the SRS scores between the ASD group and the control group. The endogenous antioxidant capacity may be deficient without altered urinary HEL and 8-OHdG levels in individuals with ASD. The plasma SOD levels may be related to reduced endogenous antioxidant capacity.

Genetic architecture, epigenetic influence and environment exposure in the pathogenesis of Autism

Autism spectrum disorder (ASD) is a spectral neurodevelopment disorder affecting approximately 1% of the population. ASD is characterized by impairments in reciprocal social interaction, communication deficits and restricted patterns of behavior. Multiple factors, including genetic/genomic, epigenetic/epigenomic and environmental, are thought to be necessary for autism development. Recent reviews have provided further insight into the genetic/genomic basis of ASD. It has long been suspected that epigenetic mechanisms, including DNA methylation, chromatin structures and long non-coding RNAs may play important roles in the pathology of ASD. In addition to genetic/genomic alterations and epigenetic/epigenomic influences, environmental exposures have been widely accepted as an important role in autism etiology, among which immune dysregulation and gastrointestinal microbiota are two prominent ones.

Subcellular organization of UBE3A in neurons

Ubiquitination regulates a broad array of cellular processes, and defective ubiquitination is implicated in several neurological disorders. Loss of the E3 ubiquitin-protein ligase UBE3A causes Angelman syndrome. Despite its clinical importance, the normal role of UBE3A in neurons is still unclear. As a step toward deciphering its possible functions, we performed high-resolution light and electron microscopic immunocytochemistry. We report a broad distribution of UBE3A in neurons, highlighted by concentrations in axon terminals and euchromatin-rich nuclear domains. Our findings suggest that UBE3A may act locally to regulate individual synapses while also mediating global, neuronwide influences through the regulation of gene transcription. J. Comp. Neurol. 525:233-251, 2017. © 2016 Wiley Periodicals, Inc.

From UBE3A to Angelman syndrome: a substrate perspective

Angelman syndrome (AS) is a debilitating neurodevelopmental disorder that is characterized by motor dysfunction, intellectual disability, speech impairment, seizures and common features of autism spectrum disorders (ASDs). Some of these AS related phenotypes can be seen in other neurodevelopmental disorders (Williams, 2011; Tan et al., 2014). AS patients commonly carry mutations that render the maternally inherited UBE3A gene non-functional. Duplication of the chromosomal region containing the UBE3A gene is associated with ASDs. Although the causative role for UBE3A gene mutations in AS is well established, a long-standing challenge in AS research has been to identify neural substrates of UBE3A, an E3 ubiquitin ligase. A prevailing hypothesis is that changes in UBE3A protein levels would alter the levels of a collection of protein substrates, giving rise to the unique phenotypic aspects of AS and possibly UBE3A associated ASDs. Interestingly, proteins altered in AS are linked to additional ASDs that are not previously associated with changes in UBE3A, indicating a possible molecular overlap underlying the broad-spectrum phenotypes of these neurogenetic disorders. This idea raises the possibility that there may exist a “one-size-fits-all” approach to the treatment of neurogenetic disorders with phenotypes overlapping AS. Furthermore, while a comprehensive list of UBE3A substrates and downstream affected pathways should be developed, this is only part of the story. The timing of when UBE3A protein functions, through either changes in UBE3A or possibly substrate expression patterns, appears to be critical for AS phenotype development. These data call for further investigation of UBE3A substrates and their timing of action relevant to AS phenotypes.

Specific and global coagulation tests in patients with mild haemophilia A with a double mutation (Glu113Asp, Arg593Cys)

BACKGROUND

Heterogeneous bleeding phenotypes are observed in haemophilia A patients with the same mutation in the F8 gene. Specific mutations in the A2 domain of factor VIII are associated with mild haemophilia and a higher risk of inhibitor development. Double mutations in mild haemophilia A are rarely reported. In this study, we investigated the in vitro function of factor VIII, performing different specific and global coagulation assays, observed clinical characteristics and assessed the possible predictive diagnostic value of the differences.

MATERIALS AND METHODS

The clinical features of haemophiliacs with a mild phenotype were reviewed. Blood samples were obtained and analysed for mutations and coagulation assays: activated partial thromboplastin time, one-stage and chromogenic factor VIII activity, factor VIII antigen and rotational thromboelastometry.

RESULTS

We report on a cohort of 22 patients with double Glu113Asp, Arg593Cys mutations. All our patients have a quantitative defect of factor VIII and preserved similar functional activity. Factor VIII activities measured by the one-stage or chromogenic method were not discrepant, although the chromogenic assay resulted in 20% lower factor VIII activities. Waveform analysis showed a lower maximum value of the second derivative curve (Max2) of APTT with curve shape alternation, while thromboelastometry (INTEM) showed low sensitivity in comparison to results in a normal population.

DISCUSSION

In genotyping, the coexistence of a second mutation should never be excluded, especially in cases of discordant clinical presentation. Waveform analysis correlates better with factor VIII activity than thromboelastometry and the Max2 parameter could provide additional information in managing haemophilia patients. The utility of specific factor activity and global haemostatic assays in general practice still needs to be investigated.

Modulation of the genome and epigenome of individuals susceptible to autism by environmental risk factors

Diverse environmental factors have been implicated with the development of autism spectrum disorders (ASD). Genetic factors also underlie the differential vulnerability to environmental risk factors of susceptible individuals. Currently the way in which environmental risk factors interact with genetic factors to increase the incidence of ASD is not well understood. A greater understanding of the metabolic, cellular, and biochemical events involved in gene x environment interactions in ASD would have important implications for the prevention and possible treatment of the disorder. In this review we discuss various established and more alternative processes through which environmental factors implicated in ASD can modulate the genome and epigenome of genetically-susceptible individuals.