Cytogenetic abnormalities and fragile-X syndrome in Autism Spectrum Disorder

Screening for Fragile X Syndrome Among Filipino Children with Autism Spectrum Disorder

Individuals with autism spectrum disorder present with difficulties in social communication, restricted interests or behaviors and other co-morbidities. About 2 to 10% of cases of autism have a genetic cause, and Fragile X Syndrome (FXS) is reported in 0 to 6.5% of individuals with autism. However, the FXS and premutation prevalence among Filipino children has never been reported. The aim of the study was to establish the presence of FXS or premutation carriers among Filipino children with autism and to describe the phenotypic characteristic of cases identified. Blood was collected from 235 children aged 2-6 years old and diagnosed with autism. Samples were analyzed using PCR methods to amplify CGG repeats in the FMRI gene. The diagnosis of autism was confirmed through the Autism Diagnostic Observation Schedule-2. Additional characteristics were documented from a physical examination, Griffiths Scales of Child Development assessment and a parent-answered questionnaire using the Vineland Adaptive Behavior Scale. Fragile X testing through PCR methods in 235 children with diagnosed autism showed 220 (93.6%) were negative, no full mutations, 1 (0.436%) premutation carrier and 14 (5.95%) cases contained intermediate alleles. The FXS testing was limited to confirmed cases of autism, which is considered a high-risk group and does not provide prevalence for the general Filipino population. Subjects were self-referred or referred by clinicians, which may not represent the Filipino autism population with a bias towards those with means for clinical consultations and ability to travel to the place of testing. Samples were not measured for mosaicism, DNA methylation or AGG interspersion patterns. These may have effects on the CGG repeat expansion and overall presentation of FXS. Findings from a single premutation carrier cannot characterize features distinctly present in Filipinos with the mutation. Nevertheless, these results support the data that the prevalence of FXS in Asian populations may be lower than non-Asian populations. This can contribute to a better understanding of FXS and genetic causes of autism in the Philippines and other Asian populations.

Fragile X Syndrome in children

Fragile X syndrome is caused by the expansion of CGG triplets in the FMR1 gene, which generates epigenetic changes that silence its expression. The absence of the protein coded by this gene, FMRP, causes cellular dysfunction, leading to impaired brain development and functional abnormalities. The physical and neurologic manifestations of the disease appear early in life and may suggest the diagnosis. However, it must be confirmed by molecular tests. It affects multiple areas of daily living and greatly burdens the affected individuals and their families. Fragile X syndrome is the most common monogenic cause of intellectual disability and autism spectrum disorder; the diagnosis should be suspected in every patient with neurodevelopmental delay. Early interventions could improve the functional prognosis of patients with Fragile X syndrome, significantly impacting their quality of life and daily functioning. Therefore, healthcare for children with Fragile X syndrome should include a multidisciplinary approach.

The aberrant behavior profile in Indonesian individuals with fragile X syndrome with limited genetic services

Fragile X syndrome (FXS) is caused by the full mutation in the fragile x messenger ribonucleoprotein 1 (FMR1) gene leading to the absence of the fragile X protein (FXP). Previous studies show that individuals with FXS exhibit changing behavior over time; therefore, this study aimed to elucidate the aberrant behavior profile of FXS individuals. The Aberrant Behavior Checklist-Community (ABC-C) was used to measure the aberrant behavior profile of individuals with FXS, which was rated by the parent/caregiver combined with clinical impression. A total of 58 items were used to assess aberrant behaviors across five subscales. Forty-nine individuals with FXS were included (32 males, 17 females) with a mean age of 32.9 ± 14.62 years in males and 33.4 ± 13.98 years in females. The average score of irritability and hyperactivity was significantly higher in male FXS individuals (5.37 ± 6.231 and 10.28 ± 8.524) than in female individuals (3.24 ± 7.093 and 3.76 ± 3.327) with p = 0.046 and p = 0.001, respectively. Overall irritability in FXS individuals significantly decreased over time (ß = -0.141; p = 0.032). A modest worsening in lethargy/social withdrawal in males across age and a gentle improvement in hyperactivity/noncompliance in male of FXS individuals were observed. FXS males had higher hyperactivity problems than FXS female individuals across age.

Dog Therapy in Supporting the Rehabilitation Process of Children with Autism

Introduction: Autism is not a specific condition. It is, however, a comprehensive disorder of psychomotor and social development. A number of factors, both environmental (family-related) and genetic, are believed to be the cause of autism. The percentage of children affected by autism has been increasing over the past 20 years. It is assumed that statistically, approximately 20 children in every 10,000 will become affected by this condition. Autism is 4 times more common in boys than in girls. The disorder is characterised by impaired mental growth, and, consequently, social and motor development. Research objective: The aim of the article is to present the role of dog therapy in supporting the process of therapeutic rehabilitation among children with autism. In particular, the following aspects were taken into account: breeds of canines used in dog therapy, mechanisms of influence concerning dog therapy on the child's body, as well as the forms and results obtained. Material and methods: The work is a narrative review. It was written on the basis of the document analysis method with the use of quantitative and qualitative techniques, as well as database searches for Polish and foreign scientific literature on the subject, i.e. Web of Science, PubMed and Google Scholar. In the article, the research results are presented in relation to the efficiency of applying dog therapy in the treatment of autistic children between 2002 and 2017, with emphasis on foreign literature. Results: The most commonly used forms of dog therapy used are: Animal Assisted Activity (AAA), Animal Assisted Therapy (AAT) and Animal Assisted Education (AAE). Conclusions: The use of dogs in the process of therapeutic rehabilitation has positive influence both on the autistic child and his/her family environment. It helps cope better with many difficulties and motivates to take up more activities. Dog therapy affects all spheres of personal development, i.e. mental, motor and socio-emotional.

Behavior Problems and Social Competence in Fragile X Syndrome: A Systematic Review

Fragile X syndrome (FXS) causes intellectual disability and is the known leading cause of autism. Common problems in FXS include behavior and social problems. Along with syndromic characteristics and autism comorbidity, environmental factors might influence these difficulties. This systematic review focuses on the last 20 years of studies concerning behavior and social problems in FXS, considering environmental and personal variables that might influence both problems. Three databases were reviewed, leading to fifty-one studies meeting the inclusion criteria. Attention deficit hyperactivity disorder (ADHD) problems remain the greatest behavior problems, with behavioral problems and social competence being stable during the 20 years. Some developmental trajectories might have changed due to higher methodological control, such as aggressive behavior and attention problems. The socialization trajectory from childhood to adolescence remains unclear. Comorbidity with autism in individuals with FXS increased behavior problems and worsened social competence profiles. At the same time, comparisons between individuals with comorbid FXS and autism and individuals with autism might help define the comorbid phenotype. Environmental factors and parental characteristics influenced behavior problems and social competence. Higher methodological control is needed in studies including autism symptomatology and parental characteristics. More studies comparing autism in FXS with idiopathic autism are needed to discern differences between conditions.

Screening for FMR1 CGG Repeat Expansion in Thai Patients with Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a complex disorder with a heterogeneous etiology. Fragile X syndrome (FXS) is recognized as the most common single gene mutation associated with ASD. FXS patients show some autistic behaviors and may be difficult to distinguish at a young age from autistic children. However, there have been no published reports on the prevalence of FXS in ASD patients in Thailand. In this study, we present a pilot study to analyze the CGG repeat sizes of the FMR1 gene in Thai autistic patients. We screened 202 unrelated Thai patients (168 males and 34 females) with nonsyndromic ASD and 212 normal controls using standard FXS molecular diagnosis techniques. The distributions of FMR1 CGG repeat sizes in the ASD and normal control groups were similar, with the two most common alleles having 29 and 30 CGG repeats, followed by an allele with 36 CGG repeats. No FMR1 full mutations or premutations were found in either ASD individuals or the normal controls. Interestingly, three ASD male patients with high normal CGG and intermediate CGG repeats (44, 46, and 53 CGG repeats) were identified, indicating that the prevalence of FMR1 intermediate alleles in Thai ASD patients was approximately 1% while these alleles were absent in the normal male controls. Our study indicates that CGG repeat expansions of the FMR1 gene may not be a common genetic cause of nonsyndromic ASD in Thai patients. However, further studies for mutations other than the CGG expansion in the FMR1 gene are required to get a better information on FXS prevalence in Thai ASD patients.

The role of the endocannabinoid system as a therapeutic target for autism spectrum disorder: Lessons from behavioral studies on mouse models

Recent years have seen an impressive amount of research devoted to understanding the etiopathology of Autism Spectrum Disorder (ASD) and developing therapies for this syndrome. Because of the lack of biomarkers of ASD, this work has been largely based on the behavioral characterization of rodent models, based on a multitude of genetic and environmental manipulations. Here we highlight how the endocannabinoid system (ECS) has recently emerged within this context of mouse behavioral studies as an etiopathological factor in ASD and a valid potential therapeutic target. We summarize the most recent results showing alterations of the ECS in rodent models of ASD, and demonstrating ASD-like behaviors in mice with altered ECS, induced either by genetic or pharmacological manipulations. We also give a critical overview of the most relevant advances in designing treatments and novel mouse models for ASD targeting the ECS, highlighting the relevance of thorough and innovative behavioral approaches to investigate the mechanisms acting underneath the complex features of ASD.

Copy number variations in Japanese children with autism spectrum disorder

OBJECTIVE

Although autism spectrum disorder (ASD) occurs worldwide, most genomic studies on ASD were performed on those of Western ancestry. We hypothesized ASD-related copy number variations (CNVs) of Japanese individuals might be different from those of Western individuals.

METHODS

Subjects were recruited from the Hirosaki 5-year-old children's developmental health check-up (HFC) between 2013 and 2016 (ASD group; n = 68, control group; n = 124). This study conducted CNV analysis using genomic DNA from peripheral blood of 5-year-old Japanese children. Fisher's exact test was applied for profiling subjects and CNV loci.

RESULTS

Four ASD-related CNVs: deletion at 12p11.1, duplications at 4q13.2, 8p23.1 and 18q12.3 were detected (P = 0.015, 0.024, 0.009, 0.004, respectively). Specifically, the odds ratio of duplication at 18q12.3 was highest among the 4 CNVs (odds ratio, 8.13).

CONCLUSIONS

Four CNVs: microdeletion at 12p11.1, microduplications at 4q13.2, 8p23.1 and 18q12.3 were detected as ASD-related CNVs in Japanese children in this study. Although these CNVs were consistent with several reports by Western countries at cytoband levels, these did not consistent at detailed genomic positions and sizes. Our data indicate the possibility that these CNVs are characteristic of Japanese children with ASD. We conclude that Japanese individuals with ASD may harbor CNVs different from those of Western individuals with ASD.

Emerging Role of m6 A Methylome in Brain Development: Implications for Neurological Disorders and Potential Treatment

Dynamic modification of RNA affords proximal regulation of gene expression triggered by non-genomic or environmental changes. One such epitranscriptomic alteration in RNA metabolism is the installation of a methyl group on adenosine [N⁶-methyladenosine (m⁶A)] known to be the most prevalent modified state of messenger RNA (mRNA) in the mammalian cell. The methylation machinery responsible for the dynamic deposition and recognition of m⁶A on mRNA is composed of subunits that play specific roles, including reading, writing, and erasing of m⁶A marks on mRNA to influence gene expression. As a result, peculiar cellular perturbations have been linked to dysregulation of components of the mRNA methylation machinery or its cofactors. It is increasingly clear that neural tissues/cells, especially in the brain, make the most of m⁶A modification in maintaining normal morphology and function. Neurons in particular display dynamic distribution of m⁶A marks during development and in adulthood. Interestingly, such dynamic m⁶A patterns are responsive to external cues and experience. Specific disturbances in the neural m⁶A landscape lead to anomalous phenotypes, including aberrant stem/progenitor cell proliferation and differentiation, defective cell fate choices, and abnormal synaptogenesis. Such m⁶A-linked neural perturbations may singularly or together have implications for syndromic or non-syndromic neurological diseases, given that most RNAs in the brain are enriched with m⁶A tags. Here, we review the current perspectives on the m⁶A machinery and function, its role in brain development and possible association with brain disorders, and the prospects of applying the clustered regularly interspaced short palindromic repeats (CRISPR)–dCas13b system to obviate m⁶A-related neurological anomalies.

Towards a Change in the Diagnostic Algorithm of Autism Spectrum Disorders: Evidence Supporting Whole Exome Sequencing as a First-Tier Test

Autism spectrum disorder (ASD) is a prevalent and extremely heterogeneous neurodevelopmental disorder (NDD) with a strong genetic component. In recent years, the clinical relevance of de novo mutations to the aetiology of ASD has been demonstrated. Current guidelines recommend chromosomal microarray (CMA) and a FMR1 testing as first-tier tests, but there is increasing evidence that support the use of NGS for the diagnosis of NDDs. Specifically in ASD, it has not been extensively evaluated and, thus, we performed and compared the clinical utility of CMA, FMR1 testing, and/or whole exome sequencing (WES) in a cohort of 343 ASD patients. We achieved a global diagnostic rate of 12.8% (44/343), the majority of them being characterised by WES (33/44; 75%) compared to CMA (9/44; 20.4%) or FMR1 testing (2/44; 4.5%). Taking into account the age at which genetic testing was carried out, we identified a causal genetic alteration in 22.5% (37/164) of patients over 5 years old, but only in 3.9% (7/179) of patients under this age. Our data evidence the higher diagnostic power of WES compared to CMA in the study of ASD and support the implementation of WES as a first-tier test for the genetic diagnosis of this disorder, when there is no suspicion of fragile X syndrome.

Symptoms of Autism Spectrum Disorder in Children With Down Syndrome and Williams Syndrome

Research suggests that people with a Williams syndrome (WS) or Down syndrome (DS) diagnosis display an increased prevalence of autism spectrum disorder (ASD) when compared to the general population. This study aimed to examine characteristics of ASD in a group of children with DS or WS. Results suggest that children with DS and WS exhibit higher levels of autism symptoms than the general population, particularly in the area of unusual behaviors, and that these elevations are not solely due to deficits in adaptive behavior. There are many possible explanations for these elevations, such as issues with measurement, etiological overlap, or similar behavioral phenotypes. More research is needed to further our understanding of the overlap of ASD symptoms in these populations.

Experiences of the Molecular Diagnosis of Fragile X Syndrome in Ecuador

Fragile X syndrome (FXS) is the most common cause of hereditary intellectual disability and the second most common cause of intellectual disability of genetic etiology. This complex neurodevelopmental disorder is caused by an alteration in the CGG trinucleotide expansion in fragile X mental retardation gene 1 (FMR1) leading to gene silencing and the subsequent loss of its product: fragile X mental retardation protein 1 (FMRP). Molecular diagnosis is based on polymerase chain reaction (PCR) screening followed by Southern blotting (SB) or Triplet primer-PCR (TP-PCR) to determine the number of CGG repeats in the FMR1 gene. We performed, for the first time, screening in 247 Ecuadorian male individuals with clinical criteria to discard FXS. Analysis was carried out by the Genetics Service of the Hospital de Especialidades No. 1 de las Fuerzas Armadas (HE-1), Ecuador. The analysis was performed using endpoint PCR for CGG fragment expansion analysis of the FMR1 gene. Twenty-two affected males were identified as potentially carrying the full mutation in FMR1 and thus diagnosed with FXS that is 8.1% of the sample studied. The average age at diagnosis of the positive cases was 13 years of age, with most cases from the geographical area of Pichincha (63.63%). We confirmed the familial nature of the disease in four cases. The range of CGG variation in the population was 12-43 and followed a modal distribution of 27 repeats. Our results were similar to those reported in the literature; however, since it was not possible to differentiate between premutation and mutation cases, we can only establish a molecular screening approach to identify an expanded CGG repeat, which makes it necessary to generate national strategies to optimize molecular tests and establish proper protocols for the diagnosis, management, and follow-up of patients, families, and communities at risk of presenting FXS.

Association Between DCC Polymorphisms and Susceptibility to Autism Spectrum Disorder

Autism spectrum disorder (ASD) represents a group of childhood-onset lifelong neuro-developmental disorders. However, the association between single nucleotide polymorphisms (SNPs) in the deleted in colorectal carcinoma (DCC) gene and ASD susceptibility remains unclear. We investigated the association between ASD susceptibility and seven SNPs in DCC on the basis of a case-control study (231 ASD cases and 242 controls) in Chinese Han. We found that there was no association between ASD susceptibility and the seven SNPs in DCC; however, T-A haplotype (rs2229082-rs2270954), T-A-T-C haplotype (rs2229082-rs2270954-rs2292043-rs2292044), C-G-T-C-T haplotype (rs934345-rs17753970-rs2229082-rs2270954-rs2292043), C-G-T-C-T-G haplotype (rs934345-rs17753970-rs2229082-rs2270954-rs2292043-rs2292044), and G-G-T-C-C-C-C haplotype (rs934345-rs17753970-rs2229082-rs2270954-rs2292043-rs2292044-rs16956878) were associated with ASD susceptibility. Our results indicate that the haplotypes formed on the basis of the seven SNPs in DCC may be implicated in ASD.

Using Zebrafish to Model Autism Spectrum Disorder: A Comparison of ASD Risk Genes Between Zebrafish and Their Mammalian Counterparts

Autism spectrum disorders (ASDs) are a highly variable and complex set of neurological disorders that alter neurodevelopment and cognitive function, which usually presents with social and learning impairments accompanied with other comorbid symptoms like hypersensitivity or hyposensitivity, or repetitive behaviors. Autism can be caused by genetic and/or environmental factors and unraveling the etiology of ASD has proven challenging, especially given that different genetic mutations can cause both similar and different phenotypes that all fall within the autism spectrum. Furthermore, the list of ASD risk genes is ever increasing making it difficult to synthesize a common theme. The use of rodent models to enhance ASD research is invaluable and is beginning to unravel the underlying molecular mechanisms of this disease. Recently, zebrafish have been recognized as a useful model of neurodevelopmental disorders with regards to genetics, pharmacology and behavior and one of the main foundations supporting autism research (SFARI) recently identified 12 ASD risk genes with validated zebrafish mutant models. Here, we describe what is known about those 12 ASD risk genes in human, mice and zebrafish to better facilitate this research. We also describe several non-genetic models including pharmacological and gnotobiotic models that are used in zebrafish to study ASD.

Pathogenic Yield of Genetic Testing in Autism Spectrum Disorder

BACKGROUND AND OBJECTIVES

Genetic testing is recommended for individuals with autism spectrum disorder (ASD). Pathogenic yield varies by clinician and/or patient characteristics. Our objectives were to determine the pathogenic yield of genetic testing, the variability in rate of pathogenic results based on subject characteristics, and the percentage of pathogenic findings resulting in further medical recommendations in toddlers with a Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition diagnosis of ASD.

METHODS

We conducted a retrospective chart review of 500 toddlers, 18 to 36 months, diagnosed with Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition ASD (mean age: 25.8 months, 79% male). Subject demographics, medical and neuropsychological characteristics, and genetic test results were abstracted. Genetic results were divided into negative or normal, variants of unknown significance, and pathogenic. Subject characteristics were compared across results. Manual chart review determined if further recommendations were made after pathogenic results.

RESULTS

Over half of subjects (59.8%, n = 299) completed genetic testing, and of those, 36 (12.0%) had pathogenic findings. There were no significant differences in Bayley Scales of Infant Development cognitive (P = .112), language (P = .898), or motor scores (P = .488) among children with negative or normal findings versus a variant of unknown significance versus pathogenic findings. Medical recommendations in response to the genetic finding were made for 72.2% of those with pathogenic results.

CONCLUSIONS

Our findings reinforce the importance of genetic testing for toddlers diagnosed with ASD given the 12% yield and lack of phenotypic differences between subjects with and without pathogenic findings. The majority of pathogenic results lead to further medical recommendations.

Enhanced LTP of population spikes in the dentate gyrus of mice haploinsufficient for neurobeachin

Deletion of the autism candidate molecule neurobeachin (Nbea), a large PH-BEACH-domain containing neuronal protein, has been shown to affect synaptic function by interfering with neurotransmitter receptor targeting and dendritic spine formation. Previous analysis of mice lacking one allele of the Nbea gene identified impaired spatial learning and memory in addition to altered autism-related behaviours. However, no functional data from living heterozygous Nbea mice (Nbea^+/−) are available to corroborate the behavioural phenotype. Here, we explored the consequences of Nbea haploinsufficiency on excitation/inhibition balance and synaptic plasticity in the intact hippocampal dentate gyrus of Nbea^+/− animals in vivo by electrophysiological recordings. Based on field potential recordings, we show that Nbea^+/− mice display enhanced LTP of the granule cell population spike, but no differences in basal synaptic transmission, synapse numbers, short-term plasticity, or network inhibition. These data indicate that Nbea haploinsufficiency causes remarkably specific alterations to granule cell excitability in vivo, which may contribute to the behavioural abnormalities in Nbea^+/− mice and to related symptoms in patients.

Decreased reproducibility and abnormal experience-dependent plasticity of network dynamics in Fragile X circuits

Fragile X syndrome is a neurodevelopmental disorder associated with a broad range of neural phenotypes. Interpreting these findings has proven challenging because some phenotypes may reflect compensatory mechanisms or normal forms of plasticity differentially engaged by experiential differences. To help minimize compensatory and experiential influences, we used an ex vivo approach to study network dynamics and plasticity of cortical microcircuits. In Fmr1^−/y circuits, the spatiotemporal structure of Up-states was less reproducible, suggesting alterations in the plasticity mechanisms governing network activity. Chronic optical stimulation revealed normal homeostatic plasticity of Up-states, however, Fmr1^−/y circuits exhibited abnormal experience-dependent plasticity as they did not adapt to chronically presented temporal patterns in an interval-specific manner. These results, suggest that while homeostatic plasticity is normal, Fmr1^−/y circuits exhibit deficits in the ability to orchestrate multiple forms of synaptic plasticity and to adapt to sensory patterns in an experience-dependent manner—which is likely to contribute to learning deficits.

13q13.3 microdeletion associated with apparently balanced translocation of 46,XX,t(7;13) suggests NBEA involvement

BACKGROUND

Deletion of 13q13.3 is an extremely rare event.

CASE

We report on a 25-month-old girl with neurodevelopmental disorder and intellectual disability. She had dysmorphic facies characterized by synophrys, long and narrow palpebral fissures; and a large, round face with small organs such as the eyes and mouth positioned near the center. She was hypotonic and had autism-like behaviors. Blood tests and brain MRI revealed no specific findings. However, G-banding chromosome analysis showed an apparently balanced translocation: 46,XX,t(7,13)(q11.23;q12.3). Both parents had normal karyotypes. Furthermore, her abnormal phenotype and chromosomal breakpoint lesion were suspected to be associated. Hence, we conducted array comparative genomic hybridization, which revealed a 3.2 Mb novel pathological microdeletion at 13q13.3 involving 17 genes including neurobeachin (NBEA), a neurodevelopment disorder gene. Furthermore, fluorescence in situ hybridization using probes adjacent to the microdeletion suggested a concomitant occurrence of the deletion and translocation as the structural basis of this rare genomic variant.

CONCLUSION

NBEA may have roles in her neurodevelopmental phenotypes, whereas other genes within the 13q13.3 microdeletion may contribute to her dysmorphic features.

Autism spectrum disorder: definition, epidemiology, causes, and clinical evaluation

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social communication and the presence of restricted interests and repetitive behaviors. There have been recent concerns about increased prevalence, and this article seeks to elaborate on factors that may influence prevalence rates, including recent changes to the diagnostic criteria. The authors review evidence that ASD is a neurobiological disorder influenced by both genetic and environmental factors affecting the developing brain, and enumerate factors that correlate with ASD risk. Finally, the article describes how clinical evaluation begins with developmental screening, followed by referral for a definitive diagnosis, and provides guidance on screening for comorbid conditions.

Emerging biomarkers in autism spectrum disorder: a systematic review

Autism spectrum disorder (ASD) affects approximately 2% of children in the United States (US) yet its etiology is unclear and effective treatments are lacking. Therapeutic interventions are most effective if started early in life, yet diagnosis often remains delayed, partly because the diagnosis of ASD is based on identifying abnormal behaviors that may not emerge until the disorder is well established. Biomarkers that identify children at risk during the pre-symptomatic period, assist with early diagnosis, confirm behavioral observations, stratify patients into subgroups, and predict therapeutic response would be a great advance. Here we underwent a systematic review of the literature on ASD to identify promising biomarkers and rated the biomarkers in regards to a Level of Evidence and Grade of Recommendation using the Oxford Centre for Evidence-Based Medicine scale. Biomarkers identified by our review included physiological biomarkers that identify neuroimmune and metabolic abnormalities, neurological biomarkers including abnormalities in brain structure, function and neurophysiology, subtle behavioral biomarkers including atypical development of visual attention, genetic biomarkers and gastrointestinal biomarkers. Biomarkers of ASD may be found prior to birth and after diagnosis and some may predict response to specific treatments. Many promising biomarkers have been developed for ASD. However, many biomarkers are preliminary and need to be validated and their role in the diagnosis and treatment of ASD needs to be defined. It is likely that biomarkers will need to be combined to be effective to identify ASD early and guide treatment.

The Role of Non-Coding RNAs in Neurodevelopmental Disorders

Non-coding RNAs, a group of ribonucleic acids that are ubiquitous in the body and do not encode proteins, emerge as important regulatory factors in almost all biological processes in the brain. Extensive studies have suggested the involvement of non-coding RNAs in brain development and neurodevelopmental disorders, and dysregulation of non-coding RNAs is associated with abnormal brain development and the etiology of neurodevelopmental disorders. Here we provide an overview of the roles and working mechanisms of non-coding RNAs, and discuss potential clinical applications of non-coding RNAs as diagnostic and prognostic markers and as therapeutic targets in neurodevelopmental disorders.

Next-Generation Sequencing in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a common disorder that causes substantial distress. Heritability studies consistently show a strong genetic contribution, raising the hope that identifying ASD-associated genetic variants will offer insights into neurobiology and ultimately therapeutics. Next-generation sequencing (NGS) enabled the identification of disruptive variants throughout protein-coding regions of the genome. Alongside large cohorts and novel statistical methods, these NGS methods revolutionized ASD gene discovery. NGS methods have also contributed substantially to functional genetic data, such as gene expression, used to understand the neurobiological consequences of disrupting these ASD-associated genes. These functional data are also critical for annotating the noncoding genome as whole-genome sequencing (WGS) begins to provide initial insights outside of protein-coding regions. NGS methods still have a major role to play, as do similarly transformative advances in stem cell and gene-editing methods, in translating genetic discoveries into a first generation of ASD therapeutics.

Environmental and Genetic Factors in Autism Spectrum Disorders: Special Emphasis on Data from Arabian Studies

One of the most common neurodevelopmental disorders worldwide is autism spectrum disorder (ASD), which is characterized by language delay, impaired communication interactions, and repetitive patterns of behavior caused by environmental and genetic factors. This review aims to provide a comprehensive survey of recently published literature on ASD and especially novel insights into excitatory synaptic transmission. Even though numerous genes have been discovered that play roles in ASD, a good understanding of the pathophysiologic process of ASD is still lacking. The protein⁻protein interactions between the products of NLGN, SHANK, and NRXN synaptic genes indicate that the dysfunction in synaptic plasticity could be one reason for the development of ASD. Designing more accurate diagnostic tests for the early diagnosis of ASD would improve treatment strategies and could enhance the appropriate monitoring of prognosis. This comprehensive review describes the psychotropic and antiepileptic drugs that are currently available as effective pharmacological treatments and provides in-depth knowledge on the concepts related to clinical, diagnostic, therapeutic, and genetic perspectives of ASD. An increase in the prevalence of ASD in Gulf Cooperation Council countries is also addressed in the review. Further, the review emphasizes the need for international networking and multidimensional studies to design novel and effective treatment strategies.

Differentiating social preference and social anxiety phenotypes in fragile X syndrome using an eye gaze analysis: a pilot study

Background

Fragile X syndrome (FXS) is the leading inherited cause of autism spectrum disorder, but there remains debate regarding the clinical presentation of social deficits in FXS. The aim of this study was to compare individuals with FXS to typically developing controls (TDC) and individuals with idiopathic autism spectrum disorder (ASD) across two social eye tracking paradigms.

Methods

Individuals with FXS and age- and gender-matched TDC and individuals with idiopathic ASD completed emotional face and social preference eye tracking tasks to evaluate gaze aversion and social interest, respectively. Participants completed a battery of cognitive testing and caregiver-reported measures for neurobehavioral characterization.

Results

Individuals with FXS exhibited reduced eye and increased mouth gaze to emotional faces compared to TDC. Gaze aversive findings were found to correlate with measures of anxiety, social communication deficits, and behavioral problems. In the social interest task, while individuals with idiopathic ASD showed significantly less social preference, individuals with FXS displayed social preference similar to TDC.

Conclusions

These findings suggest fragile X syndrome social deficits center on social anxiety without the prominent reduction in social interest associated with autism spectrum disorder. Specifically designed eye tracking techniques clarify the nature of social deficits in fragile X syndrome and may have applications to improve phenotyping and evaluate interventions targeting social functioning impairments.

Imaging genetics in autism spectrum disorders: Linking genetics and brain imaging in the pursuit of the underlying neurobiological mechanisms

Autism spectrum disorders (ASD) include a wide range of heterogeneous neurodevelopmental conditions that affect an individual in several aspects of social communication and behavior. Recent advances in molecular genetic technologies have dramatically increased our understanding of ASD etiology through the identification of several autism risk genes, most of which serve important functions in synaptic plasticity and protein synthesis. However, despite significant progress in this field of research, the characterization of the neurobiological mechanisms by which common genetic risk variants might operate to give rise to ASD symptomatology has proven to be far more difficult than expected. The imaging genetics approach holds great promise for advancing our understanding of ASD etiology by bridging the gap between genetic variations and their resultant biological effects on the brain. This paper provides a conceptual overview of the contribution of genetics in ASD and discusses key findings from the emerging field of imaging genetics.

Early development of infants with neurofibromatosis type 1: a case series

Background

Prospective studies of infants at familial risk for autism spectrum disorder (ASD) have yielded insights into the earliest signs of the disorder but represent heterogeneous samples of unclear aetiology. Complementing this approach by studying cohorts of infants with monogenic syndromes associated with high rates of ASD offers the opportunity to elucidate the factors that lead to ASD.

Methods

We present the first report from a prospective study of ten 10-month-old infants with neurofibromatosis type 1 (NF1), a monogenic disorder with high prevalence of ASD or ASD symptomatology. We compared data from infants with NF1 to a large cohort of infants at familial risk for ASD, separated by outcome at age 3 of ASD (n = 34), atypical development (n = 44), or typical development (n = 89), and low-risk controls (n = 75). Domains assessed at 10 months by parent report and examiner observation include cognitive and adaptive function, sensory processing, social engagement, and temperament.

Results

Infants with NF1 showed striking impairments in motor functioning relative to low-risk infants; this pattern was seen in infants with later ASD from the familial cohort (HR-ASD). Both infants with NF1 and the HR-ASD group showed communication delays relative to low-risk infants.

Conclusions

Ten-month-old infants with NF1 show a range of developmental difficulties that were particularly striking in motor and communication domains. As with HR-ASD infants, social skills at this age were not notably impaired. This is some of the first information on early neurodevelopment in NF1. Strong inferences are limited by the sample size, but the findings suggest implications for early comparative developmental science and highlight motor functioning as an important domain to inform the development of relevant animal models. The findings have clinical implications in indicating an important focus for early surveillance and remediation in this early diagnosed genetic disorder.

Tactile Defensiveness and Impaired Adaptation of Neuronal Activity in the Fmr1 Knock-Out Mouse Model of Autism

Sensory hypersensitivity is a common symptom in autism spectrum disorders (ASDs), including fragile X syndrome (FXS), and frequently leads to tactile defensiveness. In mouse models of ASDs, there is mounting evidence of neuronal and circuit hyperexcitability in several brain regions, which could contribute to sensory hypersensitivity. However, it is not yet known whether or how sensory stimulation might trigger abnormal sensory processing at the circuit level or abnormal behavioral responses in ASD mouse models, especially during an early developmental time when experience-dependent plasticity shapes such circuits. Using a novel assay, we discovered exaggerated motor responses to whisker stimulation in young Fmr1 knock-out (KO) mice (postnatal days 14-16), a model of FXS. Adult Fmr1 KO mice actively avoided a stimulus that was innocuous to wild-type controls, a sign of tactile defensiveness. Using in vivo two-photon calcium imaging of layer 2/3 barrel cortex neurons expressing GCaMP6s, we found no differences between wild-type and Fmr1 KO mice in overall whisker-evoked activity, though 45% fewer neurons in young Fmr1 KO mice responded in a time-locked manner. Notably, we identified a pronounced deficit in neuronal adaptation to repetitive whisker stimulation in both young and adult Fmr1 KO mice. Thus, impaired adaptation in cortical sensory circuits is a potential cause of tactile defensiveness in autism.SIGNIFICANCE STATEMENT We use a novel paradigm of repetitive whisker stimulation and in vivo calcium imaging to assess tactile defensiveness and barrel cortex activity in young and adult Fmr1 knock-out mice, the mouse model of fragile X syndrome (FXS). We describe evidence of tactile defensiveness, as well as a lack of L2/3 neuronal adaptation in barrel cortex, during whisker stimulation. We propose that a defect in sensory adaptation within local neuronal networks, beginning at a young age and continuing into adulthood, likely contributes to sensory overreactivity in FXS and perhaps other ASDs.

Diagnostic Evaluation of Children with Autism Spectrum Disorders: Clinician Compliance with Published Guidelines

OBJECTIVE

To assess to what extent child neurologists (CNs) and developmental-behavioral pediatricians (DBPs) order diagnostic tests that are not recommended/indicated and/or fail to order tests that are recommended/indicated when evaluating children with an autism spectrum disorder (ASD).

METHOD

CNs and DBPs in the United States were asked which laboratory tests they would "routinely order" for a preschool child with ASD and IQ = 58 (ASD + Intellectual Disability (ID)), and a preschool child with ASD and IQ = 85 (ASD-ID). Chi-square tests were performed to identify differences (CNs vs DBPs) in laboratory testing.

RESULTS

The sample consisted of 267 respondents (127 CN's; 140 DBPs). When evaluating ASD + ID or ASD - ID, inappropriate tests (≥1) were ordered by 76.8% and 76.4% of MDs, respectively. There was no significant difference between specialties in compliance with evaluation guidelines for ASD + ID (CN = 20.5% vs DBP = 16.4%; χ = 0.73). No significant differences were noted (DBP vs CN) regarding the percent ordering inappropriate tests for either clinical case or within each specialty when comparing testing for ASD + ID versus ASD - ID. Relative to DBPs, CNs were more likely to order EEGs and MRIs when evaluating children with ASD + ID or ASD - ID. 10% and 40% of respondents did not order any recommended genetic tests when evaluating ASD + ID and ASD - ID, respectively.

CONCLUSION

When evaluating children with ASD, many CNs and DBPs fail to order tests that should be routinely performed and often order tests that are not routinely indicated yet are neither benign nor inexpensive. Recommended molecular genetic tests are often not ordered. Clinical guidelines must be updated and better promulgated.

Global transcriptome dysregulation in second trimester fetuses with FMR1 expansions

OBJECTIVE

We tested the hypothesis that FMR1 expansions would result in global gene dysregulation as early as the second trimester of human fetal development.

METHOD

Using cell-free fetal RNA obtained from amniotic fluid supernatant and expression microarrays, we compared RNA levels in samples from fetuses with premutation or full mutation allele expansions with control samples.

RESULTS

We found clear signals of differential gene expression relating to a variety of cellular functions, including ubiquitination, mitochondrial function, and neuronal/synaptic architecture. Additionally, among the genes showing differential gene expression, we saw links to related diseases of intellectual disability and motor function. Finally, within the unique molecular phenotypes established for each mutation set, we saw clear signatures of mitochondrial dysfunction and disrupted neurological function. Patterns of differential gene expression were very different in male and female fetuses with premutation alleles.

CONCLUSION

These results support a model for which genetic misregulation during fetal development may set the stage for late clinical manifestations of FMR1-related disorders. © 2016 John Wiley & Sons, Ltd.

The Role of MicroRNAs in Cerebellar Development and Autism Spectrum Disorder During Embryogenesis

MicroRNAs (miRNAs) are a class of small non-coding RNA molecules with wide-ranging and subtle effects on protein production. Their activity during the development of the cerebellum provides a valuable exemplar of how non-coding molecules may assist the development and function of the central nervous system and drive neurodevelopmental disorders. Three distinct aspects of miRNA contribution to early cerebellar development will here be reviewed. Aspects are the establishment of the cerebellar anlage, the generation and maturation of at least two principal cell types of the developing cerebellar microcircuit, and the etiology and early progression of autism spectrum disorder. It will be argued here that the autism spectrum is an adept model to explore miRNA impact on the cognitive and affective processes that descend from the developing cerebellum.

Genetic Studies in Autism

Autism is a complex neurodevelopmental disorder, which has captured the attention of not only pediatricians but also the parents. From the symptoms until the final diagnosis, parents undergo a diagnostic odyssey that involves a battery of tests without much yield. This has led to an increase in the referrals to the clinical geneticists to rule out the possible genetic etiology that can have implications for the parents for future pregnancy. This chapter focuses on the various genetic causes and their appropriate application in the evaluation of a child with Autism Spectrum Disorders (ASDs).

Diagnostic yield of array CGH in patients with autism spectrum disorder in Hong Kong

Background

Chromosomal microarray offers superior sensitivity for identification of submicroscopic copy number variants (CNV) and it is advocated to be the first tier genetic testing for patients with autism spectrum disorder (ASD). In this regard, diagnostic yield of array comparative genomic hybridization (CGH) for ASD patients is determined in a cohort of Chinese patients in Hong Kong.

Methods

A combined adult and paediatric cohort of 68 Chinese ASD patients (41 patients in adult group and 27 patients in paediatric group). The genomic DNA extracted from blood samples were analysed by array CGH using NimbleGen CGX-135K oligonucleotide array.

Results

We identified 15 CNV and eight of them were clinically significant. The overall diagnostic yield was 11.8 %. Five clinically significant CNV were detected in the adult group and three were in the paediatric group, providing diagnostic yields of 12.2 and 11.1 % respectively. The most frequently detected CNV was 16p13.11 duplications which were present in 4 patients (5.9 % of the cohort).

Conclusions

In this study, a satisfactory diagnostic yield of array CGH was demonstrated in a Chinese ASD patient cohort which supported the clinical usefulness of array CGH as the first line testing of ASD in Hong Kong.

Electronic supplementary material

The online version of this article (doi:10.1186/s40169-016-0098-1) contains supplementary material, which is available to authorized users.

Nuclear Localization of the Autism Candidate Gene Neurobeachin and Functional Interaction with the NOTCH1 Intracellular Domain Indicate a Role in Regulating Transcription

BACKGROUND

Neurobeachin (NBEA) is an autism spectrum disorders (ASD) candidate gene. NBEA deficiency affects regulated secretion, receptor trafficking, synaptic architecture and protein kinase A (PKA)-mediated phosphorylation. NBEA is a large multidomain scaffolding protein. From N- to C-terminus, NBEA has a concanavalin A-like lectin domain flanked by armadillo repeats (ACA), an A-kinase anchoring protein domain that can bind to PKA, a domain of unknown function (DUF1088) and a BEACH domain, preceded by a pleckstrin homology-like domain and followed by WD40 repeats (PBW). Although most of these domains mediate protein-protein interactions, no interaction screen has yet been performed.

METHODS

Yeast two-hybrid screens with the ACA and PBW domain modules of NBEA gave a list of interaction partners, which were analyzed for Gene Ontology (GO) enrichment. Neuro-2a cells were used for confocal microscopy and nuclear extraction analysis. NOTCH-mediated transcription was studied with luciferase reporter assays and qRT-PCR, combined with NBEA knockdown or overexpression.

RESULTS

Both domain modules showed a GO enrichment for the nucleus. PBW almost exclusively interacted with transcription regulators, while ACA interacted with a number of PKA substrates. NBEA was partially localized in the nucleus of Neuro-2a cells, albeit much less than in the cytoplasm. A nuclear localization signal was found in the DUF1088 domain, which was shown to contribute to the nuclear localization of an EGFP-DPBW fusion protein. Yeast two-hybrid identified the Notch1 intracellular domain as a physical interactor of the PBW domain and a role for NBEA as a negative regulator in Notch-mediated transcription was demonstrated.

CONCLUSION

Defining novel interaction partners of conserved NBEA domain modules identified a role for NBEA as transcriptional regulator in the nucleus. The physical interaction of NBEA with NOTCH1 is most relevant for ASD pathogenesis because NOTCH signaling is essential for neural development.

Clinical Genetic Aspects of ASD Spectrum Disorders

Early presumptions opined that autism spectrum disorder (ASD) was related to the rearing of these children by emotionally-distant mothers. Advances in the 1960s and 1970s clearly demonstrated the biologic basis of autism with a high heritability. Recent advances have demonstrated that specific etiologic factors in autism spectrum disorders can be identified in 30%–40% of cases. Based on early reports newer, emerging genomic technologies are likely to increase this diagnostic yield to over 50%. To date these investigations have focused on etiologic factors that are largely mono-factorial. The currently undiagnosed causes of ASDs will likely be found to have causes that are more complex. Epigenetic, multiple interacting loci, and four dimensional causes (with timing as a variable) are likely to be associated with the currently unidentifiable cases. Today, the “Why” is more important than ever. Understanding the causes of ASDs help inform families of important issues such as recurrence risk, prognosis, natural history, and predicting associated co-morbid medical conditions. In the current era of emerging efforts in “personalized medicine”, identifying an etiology will be critical in identifying endo-phenotypic groups and individual variations that will allow for tailored treatment for persons with ASD.

Fragile X syndrome screening in Chinese children with unknown intellectual developmental disorder

Background

Fragile X syndrome is the most common genetic disorder of intellectual developmental disorder/mental retardation (IDD/MR). The prevalence of FXS in a Chinese IDD children seeking diagnosis/treatment in mainland China is unknown.

Methods

Patients with unknown moderate to severe IDD were recruited from two children’s hospitals. Informed consent was obtained from the children's parents. The size of the CGG repeat was identified using a commercial TP-PCR assay. The influence of AGG interruptions on the CGG expansion during maternal transmission was analyzed in 24 mother-son pairs (10 pairs with 1 AGG and 14 pairs with 2 AGGs).

Results

553 unrelated patients between six months and eighteen years of age were recruited. Specimens from 540 patients (male:female = 5.2:1) produced high-quality TP-PCR data, resulting in the determination of the FMR1 CGG repeat number for each. The most common repeat numbers were 29 and 30, and the most frequent interruption pattern was 2 or 3 AGGs. Five full mutations were identified (1 familial and 4 sporadic IDD patients), and size mosaicism was apparent in 4 of these FXS patients (4/5 = 80 %). The overall yield of FXS in the IDD cohort was 0.93 % (5/540). Neither the mean size of CGG expansion (0.20 vs. 0.79, p > 0.05) nor the frequency of CGG expansion (2/10 vs. 9/14, p > 0.05) was significantly different between the 1 and 2 AGG groups following maternal transmission.

Conclusions

The FMR1 TP-PCR assay generates reliable and sensitive results across a large number of patient specimens, and is suitable for clinical genetic diagnosis. Using this assay, the prevalence of FXS was 0.93 % in Chinese children with unknown IDD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-015-0394-8) contains supplementary material, which is available to authorized users.

Fragile X Syndrome: Scientific Background and Screening Technologies

Fragile X is the most common inherited cause of mental retardation with a prevalence of 1 in 4000 for males and 1 in 5000 to 8000 for females. The American College of Medical Genetics and Genomics has recommended diagnostic testing for fragile X in symptomatic persons, women with ovarian dysfunction, and persons with tremor/ataxia syndrome. Although medical and scientific professionals do not currently recommend screening nonsymptomatic populations, improvements in current treatment approaches and ongoing clinical trials have generated growing interest in screening for fragile X. Here, we briefly review the relevant molecular basis of fragile X and fragile X testing and compare three different molecular technologies available for fragile X screening in both males and females. These technologic approaches include destabilizing the CGG-repeat region with betaine and using chimeric CGG-targeted PCR primers, using heat pulses to destabilize C-G bonds in the PCR extension step, and using melting curve analysis to differentiate expanded CGG repeats from normals. The first two-step method performed with high sensitivity and specificity. The second method provided agarose gel images that allow identification of males with expanded CGG repeats and females with expanded CGG-repeat bands which are sometimes faint. The third melting curve analysis method would require controls in each run to correct for shifting optimal cutoff values.

Genetic testing in children with autism spectrum disorders

OBJECTIVE

The aim of this study was to investigate karyotype abnormalities, MECP2 mutations, and Fragile X in a clinical population of children with Autism Spectrum Disorders (ASD) using The Clinical Report published by the American Academy of Pediatrics.

METHODS

Ninety-six children with ASD were evaluated for genetic testing and factors associated with this testing.

RESULTS

Abnormalities were found on karyotype in 9.7% and in DNA for fragile X in 1.4%. Karyotype abnormalities include inv(9)(p12q13); inv(9)(p11q13); inv(Y)(p11q11); Robertsonian translocation (13;14)(8q10q10) and (13,14)(q10q10); 9qh+; Yqh+; 15ps+; deletion 13(p11.2).

CONCLUSION

Genetic testing should be offered to all families of a child with an ASD, even not all of them would follow this recommendation. Although karyotype and FRAXA assessment will yield almost 10% positive results, a detailed history and physical examination are still the most important aspect of the etiological evaluation for children with ASD. Also, it is important to have geneticists to help in interpreting the information obtained from genetic testing.

Autism spectrum disorders: from genes to neurobiology

Advances in genome-wide technology, coupled with the availability of large cohorts, are finally yielding a steady stream of autism spectrum disorder (ASD) genes carrying mutations of large effect. These findings represent important molecular clues, but at the same time present notable challenges to traditional strategies for moving from genes to neurobiology. A remarkable degree of genetic heterogeneity, the biological pleiotropy of ASD genes, and the tremendous complexity of the human brain are prompting the development of new strategies for translating genetic discoveries into therapeutic targets. Recent developments in systems biology approaches that 'contextualize' these genetic findings along spatial, temporal, and cellular axes of human brain development are beginning to bridge the gap between high-throughput gene discovery and testable pathophysiological hypotheses.

Model-based evaluation of the impact of formulation and food intake on the complex oral absorption of mavoglurant in healthy subjects

PURPOSE

To compare the pharmacokinetics of intravenous (IV), oral immediate-release (IR) and oral modified-release (MR) formulations of mavoglurant in healthy subjects, and to assess the food effect on the MR formulation's input characteristics.

METHODS

Plasma concentration-time data from two clinical studies in healthy volunteers were pooled and analysed using NONMEM®. Drug entry into the systemic circulation was modelled using a sum of inverse Gaussian (IG) functions as an input rate function, which was estimated specifically for each formulation and food state.

RESULTS

Mavoglurant pharmacokinetics was best described by a two-compartment model with a sum of either two or three IG functions as input function. The mean absolute bioavailability from the MR formulation (0.387) was less than from the IR formulation (0.436). The MR formulation pharmacokinetics were significantly impacted by food: bioavailability was higher (0.508) and the input process was shorter (complete in approximately 36 versus 12 h for the fasted and fed states, respectively).

CONCLUSIONS

Modelling and simulation of mavoglurant pharmacokinetics indicate that the MR formulation might provide a slightly lower steady-state concentration range with lower peaks (possibly better drug tolerance) than the IR formulation, and that the MR formulation's input properties strongly depend on the food conditions at drug administration.

The dwarf phenotype in GH240B mice, haploinsufficient for the autism candidate gene Neurobeachin, is caused by ectopic expression of recombinant human growth hormone

Two knockout mouse models for the autism candidate gene Neurobeachin (Nbea) have been generated independently. Although both models have similar phenotypes, one striking difference is the dwarf phenotype observed in the heterozygous configuration of the GH240B model that is generated by the serendipitous insertion of a promoterless human growth hormone (hGH) genomic fragment in the Nbea gene. In order to elucidate this discrepancy, the dwarfism present in this Nbea mouse model was investigated in detail. The growth deficiency in Nbea^+/− mice coincided with an increased percentage of fat mass and a decrease in bone mineral density. Low but detectable levels of hGH were detected in the pituitary and hypothalamus of Nbea^+/− mice but not in liver, hippocampus nor in serum. As a consequence, several members of the mouse growth hormone (mGH) signaling cascade showed altered mRNA levels, including a reduction in growth hormone-releasing hormone mRNA in the hypothalamus. Moreover, somatotrope cells were less numerous in the pituitary of Nbea^+/− mice and both contained and secreted significantly less mGH resulting in reduced levels of circulating insulin-like growth factor 1. These findings demonstrate that the random integration of the hGH transgene in this mouse model has not only inactivated Nbea but has also resulted in the tissue-specific expression of hGH causing a negative feedback loop, mGH hyposecretion and dwarfism.

Quantitative phosphoproteomics of murine Fmr1-KO cell lines provides new insights into FMRP-dependent signal transduction mechanisms

Fragile X mental retardation protein (FMRP) is an RNA-binding protein that has a major effect on neuronal protein synthesis. Transcriptional silencing of the FMR1 gene leads to loss of FMRP and development of Fragile X syndrome (FXS), the most common known hereditary cause of intellectual impairment and autism. Here we utilize SILAC-based quantitative phosphoproteomics to analyze murine FMR1(-) and FMR1(+) fibroblastic cell lines derived from FMR1-KO embryos to identify proteins and phosphorylation sites dysregulated as a consequence of FMRP loss. We quantify FMRP-related changes in the levels of 5,023 proteins and 6,133 phosphorylation events and map them onto major signal transduction pathways. Our study confirms global downregulation of the MAPK/ERK pathway and decrease in phosphorylation level of ERK1/2 in the absence of FMRP, which is connected to attenuation of long-term potentiation. We detect differential expression of several key proteins from the p53 pathway, pointing to the involvement of p53 signaling in dysregulated cell cycle control in FXS. Finally, we detect differential expression and phosphorylation of proteins involved in pre-mRNA processing and nuclear transport, as well as Wnt and calcium signaling, such as PLC, PKC, NFAT, and cPLA2. We postulate that calcium homeostasis is likely affected in molecular pathogenesis of FXS.