Genetic basis of autism: is there a way forward?

Sociocultural and perinatal health factors associated with Autism spectrum disorder (ASD) in children

While previous research has examined perinatal factors in the context of Autism Spectrum Disorder (ASD), studies focusing on sociocultural factors is limited. We conducted a cross-sectional analysis utilizing data from the Australian Autism Biobank (AAB), which encompasses autistic children aged 2-17, their siblings, parents, and unrelated controls. Employing multivariable regression analyses, we aimed to identify factors associated with ASD across various domains, spanning health and lifestyle, perinatal, and postnatal contexts. Importantly, our analyses were adjusted for critical sociodemographic covariates. Advanced maternal age, male sex at birth, and identifying as from culturally and linguistically diverse (CALD) background, were found to be associated with risk of ASD. Pre-existing chronic health conditions in both parents and paternal medication use before conception were also associated with ASD risk in children. Associations with complications during pregnancy, caesarean delivery, and maternal medication use during pregnancy were also found. Postnatal factors of interest included the presence of health conditions (e.g., epilepsy), infections in early-life (e.g., respiratory infections), and atypical development in the first six months of life (e.g., hypotonia). These insights can guide closer monitoring and support for those with pre-existing vulnerabilities especially in terms of certain perinatal and sociocultural characteristics.

Neuregulin 2 Is a Candidate Gene for Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder with heterogeneous and complex genetic underpinnings. Our previous microarray gene expression profiling identified significantly different neuregulin-2 gene (NRG2) expression between ASD patients and controls. Thus, we aimed to clarify whether NRG2 is a candidate gene associated with ASD. The study consisted of two stages. First, we used real-time quantitative PCR in 20 ASDs and 20 controls to confirm the microarray gene expression profiling results. The average NRG2 gene expression level in patients with ASD (3.23 ± 2.80) was significantly lower than that in the controls (9.27 ± 4.78, p < 0.001). Next, we conducted resequencing of all the exons of NRG2 in a sample of 349 individuals with ASD, aiming to identify variants of the NRG2 associated with ASD. We identified three variants, including two single nucleotide variants (SNVs), IVS3 + 13A > G (rs889022) and IVS10 + 32T > A (rs182642591), and one small deletion at exon 11 of NRG2 (delGCCCGG, rs933769137). Using data from the Taiwan Biobank as the controls, we found no significant differences in allele frequencies of rs889022 and rs182642591 between two groups. However, there is a significant difference in the genotype and allele frequency distribution of rs933769137 between ASDs and controls (p < 0.0001). The small deletion is located in the EGF-like domain at the C-terminal of the NRG2 precursor protein. Our findings suggest that NRG2 might be a susceptibility gene for ASD.

The Neurogenetics of Functional Connectivity Alterations in Autism: Insights From Subtyping in 657 Individuals

BACKGROUND

There is little consensus and controversial evidence on anatomical alterations in the brains of people with autism spectrum disorder (ASD), due in part to the large heterogeneity present in ASD, which in turn is a major drawback for developing therapies. One strategy to characterize this heterogeneity in ASD is to cluster large-scale functional brain connectivity profiles.

METHODS

A subtyping approach based on consensus clustering of functional brain connectivity patterns was applied to a population of 657 autistic individuals with quality-assured neuroimaging data. We then used high-resolution gene transcriptomic data to characterize the molecular mechanism behind each subtype by performing enrichment analysis of the set of genes showing a high spatial similarity with the profiles of functional connectivity alterations between each subtype and a group of typically developing control participants.

RESULTS

Two major stable subtypes were found: subtype 1 exhibited hypoconnectivity (less average connectivity than typically developing control participants) and subtype 2, hyperconnectivity. The 2 subtypes did not differ in structural imaging metrics in any of the analyzed regions (68 cortical and 14 subcortical) or in any of the behavioral scores (including IQ, Autism Diagnostic Interview, and Autism Diagnostic Observation Schedule). Finally, only subtype 2, comprising about 43% of ASD participants, led to significant enrichments after multiple testing corrections. Notably, the dominant enrichment corresponded to excitation/inhibition imbalance, a leading well-known primary mechanism in the pathophysiology of ASD.

CONCLUSIONS

Our results support a link between excitation/inhibition imbalance and functional connectivity alterations, but only in one ASD subtype, overall characterized by brain hyperconnectivity and major alterations in somatomotor and default mode networks.

EXPRESSION PROFILES OF PTEN AND POGZ GENES IN TURKISH PATIENTS WITH AUTISM

Amaç: Otizm spektrum bozukluğu (OSB), karmaşık davranışsal fenotiplerle teşhis edilen, etiyolojik ve klinik olarak heterojen bir grup nörogelişimsel bozukluktur. Uzun yıllar boyunca yapılan kapsamlı çalışmalara rağmen, OSB'nin nedenleri hala bilinmemektedir. PTEN ve POGZ genleri, OSB fenotipinden sorumlu olabilecek aday genler olarak gösterilmiştir. Bu çalışmanın amacı, otistik hastalarda PTEN ve POGZ genlerinin ekspresyon düzeylerini araştırmaktır. Yöntem: DSM-IV ve DSM-V tanı kriterlerine göre OSB tanılı 50 hastada ve yaş-cinsiyet uyumlu 50 sağlıklı kontrolde PTEN, POGZ gen ekspresyonları kantitatif real time PCR (QRT-PCR) ile araştırıldı. Bu çalışma Erciyes Üniversitesi Genom ve Kök Hücre Merkezi'nde (GENKOK) yapılmıştır. Bulgular: POGZ geninin hastalarda kontrollere göre daha fazla eksprese olduğu ve otistik erkeklerde bu genin ekspresyonunun anlamlı olduğu bulundu. PTEN gen ekspresyonu istatistiksel olarak anlamlı değildi ancak hastalarda kontrollere göre daha düşük bulundu (p=0.7884). Bu genlerin ekspresyonu ile bilişsel geriliği olan hastalar arasındaki ilişki anlamlı değildi. Sonuç: Daha büyük hasta grupları ile diğer olası aday genlerin araştırılmasını ve sonuçların farklı klinik belirtilerle karşılaştırılmasını öneriyoruz. Anahtar Kelimeler: Otizm, Otizm Spektrum Bozuklukları, PTEN, POGZ, Ekspresyon

Dissemination of Early Intervention Program for Preschool Children on the Autism Spectrum into Community Settings: An Evaluation

We aimed to address a policy-relevant research area with high priority, namely disseminating early intervention for children on the autism spectrum into mainstream community settings. The study cohort comprised 47 children with a diagnosis of Autism Spectrum Disorder (ASD) receiving the Early Start Denver Model (ESDM) intervention: 23 children attending an Autism Specific Early Learning and Care Centre (ASELCC) and 24 children attending a mainstream preschool setting. Group comparisons revealed that the overall response to intervention was in the majority of cases not significantly different between settings. One difference was found in that children in the mainstream preschool setting showed a significant reduction in externalising behaviours compared to the children attending the autism-specific preschool. Intervention duration was found to influence outcomes with a one-month increase in duration found to improve expressive language skills. While the results need to be interpreted with caution due to the small sample size, these findings suggest that early intervention can be successfully delivered in both autism-specific and mainstream settings. However, those families needing additional parent support may be better served by a specialised service.

Identifying Subgroups of Patients With Autism by Gene Expression Profiles Using Machine Learning Algorithms

Objectives: The identification of subgroups of autism spectrum disorder (ASD) may partially remedy the problems of clinical heterogeneity to facilitate the improvement of clinical management. The current study aims to use machine learning algorithms to analyze microarray data to identify clusters with relatively homogeneous clinical features. Methods: The whole-genome gene expression microarray data were used to predict communication quotient (SCQ) scores against all probes to select differential expression regions (DERs). Gene set enrichment analysis was performed for DERs with a fold-change >2 to identify hub pathways that play a role in the severity of social communication deficits inherent to ASD. We then used two machine learning methods, random forest classification (RF) and support vector machine (SVM), to identify two clusters using DERs. Finally, we evaluated how accurately the clusters predicted language impairment. Results: A total of 191 DERs were initially identified, and 54 of them with a fold-change >2 were selected for the pathway analysis. Cholesterol biosynthesis and metabolisms pathways appear to act as hubs that connect other trait-associated pathways to influence the severity of social communication deficits inherent to ASD. Both RF and SVM algorithms can yield a classification accuracy level >90% when all 191 DERs were analyzed. The ASD subtypes defined by the presence of language impairment, a strong indicator for prognosis, can be predicted by transcriptomic profiles associated with social communication deficits and cholesterol biosynthesis and metabolism. Conclusion: The results suggest that both RF and SVM are acceptable options for machine learning algorithms to identify AD subgroups characterized by clinical homogeneity related to prognosis.

Clinical Relevance of Methylenetetrahydrofolate Reductase Genetic Testing in Autism: A Case Report of Successful Clinical Outcome

Autism spectrum disorder is an emerging public health issue. The core features of autism spectrum disorder are persistent impairment in reciprocal social communication and interaction and restricted, repetitive patterns of behavior or interests. We now know that it encompasses disorders previously referred to as early infantile autism, childhood autism, Kanner autism, high-functioning autism, atypical autism, Asperger disorder, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified. While it is agreed that the etiology of autism spectrum disorder is largely unknown, certain environmental and genetic factors may be responsible for the disease. In particular, emerging evidence has suggested the role of C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene as a possible risk factor. We present the case of a two-year-old boy with high risk for autism who was found on advanced investigation to have heterozygous polymorphism for MTHFR. This prompted us to add folic acid to his therapeutic regime. He was treated with high-dose folic acid along with conventional intervention, and went on to make excellent recovery. We conclude that pharmacological intervention has the potential to improve outcome in a subgroup of autistic children.

Association between MTHFR C677T/A1298C and susceptibility to autism spectrum disorders: a meta-analysis

BACKGROUND

Autism spectrum disorder (ASD) is becoming increasingly prevalent of late. Methylenetetrahydrofolate reductase (MTHFR) has a significant role in folate metabolism. Owing to the inconsistencies and inconclusiveness on the association between MTHFR single nucleotide polymorphism (SNP) and ASD susceptibilities, a meta-analysis was conducted to settle the inconsistencies.

METHODS

For this meta-analysis, a total of 15 manuscripts published up to January 26, 2020, were selected from PubMed, Google Scholar, Medline, WangFang, and CNKI databases using search terms "MTHFR" OR "methylenetetrahydrofolate reductase" AND "ASD" OR "Autism Spectrum Disorders" OR "Autism" AND "polymorphism" OR "susceptibility" OR "C677T" OR "A1298C".

RESULTS

The findings of the meta-analysis indicated that MTHFR C677T polymorphism is remarkably associated with ASD in the five genetic models, viz., allelic, dominant, recessive, heterozygote, and homozygote. However, the MTHFR A1298C polymorphism was not found to be significantly related to ASD in the five genetic models. Subgroup analyses revealed significant associations of ASD with the MTHFR (C677T and A1298C) polymorphism. Sensitivity analysis showed that this meta-analysis was stable and reliable. No publication bias was identified in the associations between MTHFRC677T polymorphisms and ASD in the five genetic models, except for the one with regard to the associations between MTHFRA1298C polymorphisms and ASD in the five genetic models.

CONCLUSION

This meta-analysis showed that MTHFR C677T polymorphism is a susceptibility factor for ASD, and MTHFR A1298C polymorphism is not associated with ASD susceptibility.

Reduced Local and Increased Long-Range Functional Connectivity of the Thalamus in Autism Spectrum Disorder

It is hypothesized that brain network abnormalities in autism spectrum disorder (ASD) reflect local overconnectivity and long-range underconnectivity. However, this is not a consistent finding in recent studies, which could reflect the developmental nature and the heterogeneity of ASD. Here, we tested 565 ASD and 602 neurotypical (NT) males, and 91 ASD and 233 NT females using local functional connectivity density (lFCD) mapping and seed-voxel correlation analyses to assess how local and long-range connectivities differ in ASD. Compared with NT males, ASD males had lower and weaker age-related increases in thalamic lFCD, which were associated with symptoms of autism. Post-hoc seed-voxel correlation analyses for the thalamus cluster revealed stronger connectivity with auditory, somatosensory, motoric, and interoceptive cortices for ASD than for NT, both in males and in females, which decreased with age in both ASD and NT. These results document the disruption of local thalamic connectivity and dysregulation of thalamo-cortical networks, which might contribute to perceptual, motoric, and interoceptive impairments, and are also consistent with a developmental delay in functional connectivity in ASD.

Current status of biological treatment options in Autism Spectrum Disorder

Autism Spectrum Disorders (ASDs) are characterised by deficits in social communication and restricted and repetitive behaviours. With an onset in early childhood, ASDs are thought to be heterogeneous, both genetically and clinically. This has led to the notion that "autism" is "autisms", however, there has been limited progress in understanding the different subgroups and the unique pathogenesis that would then allow targeted intervention. Although existing treatments are mainly symptom focussed, research is beginning to unravel the underlying genetic and molecular pathways, structural and functional neuronal circuitry involvement and the associated neurochemicals. This paper will review selected biological models with regard to pharmacological targets while also covering some of the non-pharmacological treatments such as neuro-stimulation.

Genetic Testing for Autism Spectrum Disorder is Lacking Evidence of Cost-effectiveness. A Systematic Review

BACKGROUND

Autism Spectrum Disorder (ASD) is a highly heritable neural development disorder characterized by social impairment. The earlier the diagnosis is made, the higher are the chances of obtaining relief of symptoms. A very early diagnosis uses molecular genetic tests, which are also offered commercially.

OBJECTIVE

Systematic review of the economic impact of genetic tests in ASD.

METHODS

We performed a systematic search of databases Pubmed, Medline, Cochrane, Econlit and the NHS Center for Reviews and Dissemination for articles in English and German from January 1, 2000 to December 31, 2015. Original articles published in peer-reviewed journals were screened in a two-step process. First, we focused our search on economic evaluations of genetic tests for ASD. Second, we searched for any economic evaluation (EE) of genetic tests.

RESULTS

We identified 185 EE of genetic tests for various diseases. However, not a single EE of genetic tests has been found for ASD. The outcomes used in the EE of the genetic tests were heterogeneous, and results were generally not comparable.

CONCLUSION

There is no evidence for cost-effectiveness of any genetic diagnostic test for ASD, although such genetic tests are available commercially. Cost-effectiveness analyses for genetic diagnostic tests for ASD are urgently required. There is a clear lack in research for EE of genetic tests.

Would Adults with Autism be less likely to Bury the Survivors? An Eye Movement Study of Anomalous Text Reading

In a single eye movement experiment we investigated the effects of context on the time course of local and global anomaly processing during reading in adults with Autism Spectrum Disorder (ASD). In one condition short paragraph texts contained anomalous target words. Detection of the anomaly was only possible through evaluation of word meaning in relation to the global context of the whole paragraph (Passage Level Anomalies). In another condition the anomaly could be detected via computation of a local thematic violation within a single sentence embedded in the paragraph (Sentence Level Anomalies). For the sentence level anomalies the ASD group, in contrast with the typically developing (TD) group, showed early detection of the anomaly as indexed by regressive eye movements from the critical target word upon fixation. Conversely, for the passage level anomalies, and in contrast with the ASD group, the TD group showed early detection of the anomaly, with increased regressive eye movements once the critical word had been fixated. The reversal of the pattern of regression path data for the two groups, for the sentence and passage level anomalies, is discussed in relation to cognitive accounts of ASD.

Does the cognitive architecture of simplex and multiplex ASD families differ?

Children with an autism spectrum disorder (ASD) and their unaffected siblings from 54 simplex (SPX, one individual in the family affected) and 59 multiplex (MPX, two or more individuals affected) families, and 124 controls were assessed on intelligence, social cognition and executive functions. SPX and MPX ASD probands displayed similar cognitive profiles, but within-family contrasts were highest in SPX families, suggesting SPX-MPX stratification may help parse etiological heterogeneity of ASD. Unaffected siblings (regardless SPX or MPX) were mostly unimpaired, suggesting that cognitive problems may be part of the defining features of ASD, rather than being an endophenotypic trait. Except for affective prosody, which appeared to be the most sensitive cognitive marker for detecting familial risk for ASD.

The roles of CC2D1A and HTR1A gene expressions in autism spectrum disorders

Classical autism belongs to a group of heterogeneous disorders known as autism spectrum disorders (ASD). Autism is defined as a neurodevelopmental disorder, characterized by repetitive stereotypic behaviors or restricted interests, social withdrawal, and communication deficits. Numerous susceptibility genes and chromosomal abnormalities have been reported in association with autism but the etiology of this disorder is unknown in many cases. CC2D1A gene has been linked to mental retardation (MR) in a family with a large deletion before. Intellectual disability (ID) is a common feature of autistic cases. Therefore we aimed to investigate the expressions of CC2D1A and HTR1A genes with the diagnosis of autism in Turkey. Forty-four autistic patients (35 boys, 9 girls) and 27 controls were enrolled and obtained whole blood samples to isolate RNA samples from each participant. CC2D1A and HTR1A gene expressions were assessed by quantitative Real-Time PCR (qRT-PCR) in Genome and Stem Cell Center, Erciyes University. Both expressions of CC2D1A and HTR1A genes studied on ASD cases and controls were significantly different (p < 0.001). The expression of HTR1A was undetectable in the ASD samples. Comparison of ID and CC2D1A gene expression was also found statistically significant (p = 0.028). CC2D1A gene expression may be used as a candidate gene for ASD cases with ID. Further studies are needed to investigate the potential roles of these CC2D1A and HTR1A genes in their related pathways in ASD.

Autism Spectrum Disorder - A Complex Genetic Disorder

Autism spectrum disorder is an entity that reflects a scientific consensus that several previously separated disorders are actually a single spectrum disorder with different levels of symptom severity in two core domains - deficits in social communication and interaction, and restricted repetitive behaviors. Autism spectrum disorder is diagnosed in all racial, ethnic and socioeconomic groups and because of its increased prevalence, reported worldwide through the last years, made it one of the most discussed child psychiatric disorders. In term of aetiology as several other complex diseases, Autism spectrum disorder is considered to have a strong genetic component.

Prevalence of Autism Spectrum Disorders in Ecuador: A Pilot Study in Quito

This research presents the results of the first phase of the study on the prevalence of pupils with Autism Spectrum Disorder (ASD) in regular education in Quito, Ecuador. One-hundred-and-sixty-one regular schools in Quito were selected with a total of 51,453 pupils. Prevalence of ASD was assessed by an interview with the rector of the school or its delegate. Results show an extremely low prevalence of 0.11 % of pupils with any ASD diagnosis; another 0.21 % were suspected to have ASD, but were without a diagnosis. This low prevalence suggests that children and adolescents with ASD are not included in regular education in Quito. These results are discussed in the light of low diagnostic identification of ASD and low inclusion tolerance.

Promoting Shared Decision Making to strengthen outcome of young children with Autism Spectrum Disorders: the role of staff competence

Little is known on how the conceptual description of Shared Decision Making (SDM) accomplishes clinical practice in the context of lifetime disabilities as in particular Autism Spectrum Disorders (ASD), when intervention is long-lasting and requires constant family involvement. This study aimed mainly to investigate to what extent the staff's competence in SDM contributes to positive child and parent improvement when involving parents in Early Intensive Behavior Interventions (EIBI). It was also geared to verify whether SDM staff competence contributes to a child's treatment responsiveness. A total of 25 young children with ASD (23 male, 3 female, age range 34-92 months, mean age 51.4±13.6) were included in the study. Of these, nine children were allocated to a Parent Involvement condition accompanied by SDM Staff Training (PI-SDM), and eight children to a Parent Inclusion in Treatment Delivery Only condition without SDM Staff Training (PI-DO). Nine months treatment outcomes of severity, developmental and adaptive measures were compared to Treatment As Usual (n=8). PI-SDM was associated with improvement of autistic symptoms (p≤.05), adaptive functioning (p≤.01) and developmental outcome (p≤.01), as well as parent (p≤.05) and staff competence (p≤.001). The magnitude of outcome was inferior in the PI-PO and TAU group. A Reliable Change was identified in more than 40% of children included in PI-SDM, while PI-PO (>20%) and TAU (>12%) let to little Reliable Change and partially skill deterioration. Staff's SDM skill competence predicts reduced parental stress (β=-.500, p≤.05) and contributes significantly to a positive treatment responder trajectory (p≤.01), besides lower severity (p≤.05), higher adaptive (p≤.01) and communication skills (p≤.05). The study indicates that parent inclusion should be conceptualized as a collaborative partnership model rather than as adherence in treatment provision, based on a target SDM staff training that may constitute an external contributor to treatment responsiveness and positive child as well as parent outcome.

Maternal socio-economic status based on occupation and autism spectrum disorders: a national case-control study

BACKGROUND

The association between parental socio-economic status (SES) and autism spectrum disorders (ASD) has been studied in several countries, but the results have been contradictory.

AIMS

The aim of this study was to examine the association between maternal SES and subtypes of ASD in Finland.

METHODS

A national case-control study was conducted. Children born in 1991-2005 and diagnosed with ASD by the year 2007 were identified from the Finnish Hospital Discharge Register (FHDR). Their matched controls were selected from the Finnish Medical Birth Register (FMBR). There were 3468 cases and 13,868 controls. The information on maternal SES was collected from the FMBR and categorized into upper white-collar workers (referent), lower white-collar workers, blue-collar workers and "others", consisting of students, housewives and other groups with unknown SES. The statistical test used was conditional logistic regression.

RESULTS

The likelihood of ASD was increased among offspring of mothers who belong to the group "others" (adjusted OR = 1.2, 95% CI 1.009-1.3). The likelihood of Asperger's syndrome was decreased among offspring of lower white-collar workers (adjusted OR = 0.8, 95% CI 0.6-0.9) and blue-collar workers (adjusted OR = 0.6, 95% CI 0.5-0.7). The likelihood of pervasive developmental disorder not otherwise specified (PDD-NOS) was increased among offspring of blue-collar workers (adjusted OR = 1.5, 1.2-1.9) and "others" (adjusted OR = 1.3, 1.1-1.7). No association was found between maternal SES and childhood autism.

CONCLUSIONS

The association between maternal SES and ASD differs by ASD subtype. Socio-economic groups might differ from each other by risk factors for ASD subtypes or by their service use.

MTHFR Gene C677T Polymorphism in Autism Spectrum Disorders

Aim. Autism is a subgroup of autism spectrum disorders, classified as a heterogeneous neurodevelopmental disorder and symptoms occur in the first three years of life. The etiology of autism is largely unknown, but it has been accepted that genetic and environmental factors may both be responsible for the disease. Recent studies have revealed that the genes involved in the folate/homocysteine pathway may be risk factors for autistic children. In particular, C677T polymorphism in the MTHFR gene as a possible risk factor for autism is still controversial. We aimed to investigate the possible effect of C677T polymorphism in a Turkish cohort. Methods. Autism patients were diagnosed by child psychiatrists according to DSM-IV and DSM-V criteria. A total of 98 children diagnosed as autistic and 70 age and sex-matched children who are nonautistic were tested for C677T polymorphism. This polymorphism was studied by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods. Results. MTHFR 677T-allele frequency was found to be higher in autistic children compared with nonautistic children (29% versus 24%), but it was not found statistically significant. Conclusions. We conclude that other MTHFR polymorphisms such as A1298C or other folate/homocysteine pathway genes may be studied to show their possible role in autism.

The social brain network and autism

Available research data in Autism suggests the role of a network of brain areas, often known as the ‘social brain’. Recent studies highlight the role of genetic mutations as underlying patho-mechanism in Autism. This mini review, discusses the basic concepts behind social brain networks, theory of mind and genetic factors associated with Autism. It critically evaluates and explores the relationship between the behavioral outcomes and genetic factors providing a conceptual framework for understanding of autism.

Towards a molecular characterization of autism spectrum disorders: an exome sequencing and systems approach

The hypothetical 'AXAS' gene network model that profiles functional patterns of heterogeneous DNA variants overrepresented in autism spectrum disorder (ASD), X-linked intellectual disability, attention deficit and hyperactivity disorder and schizophrenia was used in this current study to analyze whole exome sequencing data from an Australian ASD cohort. An optimized DNA variant filtering pipeline was used to identify loss-of-function DNA variations. Inherited variants from parents with a broader autism phenotype and de novo variants were found to be significantly associated with ASD. Gene ontology analysis revealed that putative rare causal variants cluster in key neurobiological processes and are overrepresented in functions involving neuronal development, signal transduction and synapse development including the neurexin trans-synaptic complex. We also show how a complex gene network model can be used to fine map combinations of inherited and de novo variations in families with ASD that converge in the L1CAM pathway. Our results provide an important step forward in the molecular characterization of ASD with potential for developing a tool to analyze the pathogenesis of individual affected families.

Conceptualisation and development of a quality of life measure for parents of children with autism spectrum disorder

Parents of children with autism spectrum disorder (ASD) tend to experience greater psychological distress than parents of typically developing children or children with other disabilities. Quality of Life (QoL) is increasingly recognised as a critical outcome measure for planning and treatment purposes in ASD. There is a need for ASD-specific QoL measures as generic measures may not capture all relevant aspects of living with ASD. This paper describes the conceptualisation and development of an autism-specific measure of QoL, the Quality of Life in Autism Questionnaire (QoLA) for parents and caregivers of children with ASD, that is suitable to clinical and research settings. Preliminary psychometric properties (reliability and validity) of the measure are also presented. The QoLA has 48 items in two subscales: one comprising QoL items and the second a parent report of how problematic their child's ASD symptoms are. A study involving 39 families suggested the QoLA has excellent internal consistency as well as good known-groups validity between parents of children with ASD and those who were typically developing. The QoLA also showed good convergent validity with other measures of QoL and ASD symptom severity, respectively. The QoLA may be a valuable assessment tool and merits further psychometric evaluation.

Neurodevelopmental and neuropsychiatric disorders represent an interconnected molecular system

Many putative genetic factors that confer risk to neurodevelopmental disorders such as autism spectrum disorders (ASDs) and X-linked intellectual disability (XLID), and to neuropsychiatric disorders including attention deficit hyperactivity disorder (ADHD) and schizophrenia (SZ) have been identified in individuals from diverse human populations. Although there is significant aetiological heterogeneity within and between these conditions, recent data show that genetic factors contribute to their comorbidity. Many studies have identified candidate gene associations for these mental health disorders, albeit this is often done in a piecemeal fashion with little regard to the inherent molecular complexity. Here, we sought to abstract relationships from our knowledge of systems level biology to help understand the unique and common genetic drivers of these conditions. We undertook a global and systematic approach to build and integrate available data in gene networks associated with ASDs, XLID, ADHD and SZ. Complex network concepts and computational methods were used to investigate whether candidate genes associated with these conditions were related through mechanisms of gene regulation, functional protein-protein interactions, transcription factor (TF) and microRNA (miRNA) binding sites. Although our analyses show that genetic variations associated with the four disorders can occur in the same molecular pathways and functional domains, including synaptic transmission, there are patterns of variation that define significant differences between disorders. Of particular interest is DNA variations located in intergenic regions that comprise regulatory sites for TFs or miRNA. Our approach provides a hypothetical framework, which will help discovery and analysis of candidate genes associated with neurodevelopmental and neuropsychiatric disorders.

Balance within the Neurexin Trans-Synaptic Connexus Stabilizes Behavioral Control

Autism spectrum disorder (ASD) is characterized by a broad spectrum of behavioral deficits of unknown etiology. ASD associated mutations implicate numerous neurological pathways including a common association with the neurexin trans-synaptic connexus (NTSC) which regulates neuronal cell-adhesion, neuronal circuitry, and neurotransmission. Comparable DNA lesions affecting the NTSC, however, associate with a diversity of behavioral deficits within and without the autism spectrum including a very strong association with Tourette syndrome. The NTSC is comprised of numerous post-synaptic ligands competing for trans-synaptic connection with one of the many different neurexin receptors yet no apparent association exists between specific NTSC molecules/complexes and specific behavioral deficits. Together these findings indicate a fundamental role for NTSC-balance in stabilizing pre-behavioral control. Further molecular and clinical characterization and stratification of ASD and TS on the basis of NTSC status will help elucidate the molecular basis of behavior – and define how the NTSC functions in combination with other molecular determinates to strengthen behavioral control and specify behavioral deficits.

Impact of methodological variables on functional connectivity findings in autism spectrum disorders

Growing evidence suggests that Autism Spectrum Disorder (ASD) involves abnormalities of multiple functional networks. Neuroimaging studies of ASD have therefore increasingly focused on connectivity. Many functional connectivity (fcMRI) studies have reported network underconnectivity in children and adults with ASD. However, there are notable inconsistencies, with some studies reporting overconnectivity. A previous literature survey suggested that a few methodological factors play a crucial role in differential fcMRI outcomes. Using three ASD data sets (two task-related, one resting state) from 54 ASD and 51 typically developing (TD) participants (ages 9-18 years), we examined the impact of four methodological factors: type of pipeline (co-activation vs. intrinsic analysis, related to temporal filtering and removal of task-related effects), seed selection, field of view (whole brain vs. limited ROIs), and dataset. Significant effects were found for type of pipeline, field of view, and dataset. Notably, for each dataset results ranging from robust underconnectivity to robust overconnectivity were detected, depending on the type of pipeline, with intrinsic fcMRI analyses (low bandpass filter and task regressor) predominantly yielding overconnectivity in ASD, but co-activation analyses (no low bandpass filter or task removal) mostly generating underconnectivity findings. These results suggest that methodological variables have dramatic impact on group differences reported in fcMRI studies. Improved awareness of their implications appears indispensible in fcMRI studies when inferences about "underconnectivity" or "overconnectivity" in ASD are made. In the absence of a gold standard for functional connectivity, the combination of different methodological approaches promises a more comprehensive understanding of connectivity in ASD.

The amygdala and the relevance detection theory of autism: an evolutionary perspective

In the last few decades there has been increasing interest in the role of the amygdala in psychiatric disorders and, in particular, in its contribution to the socio-emotional impairments in autism spectrum disorders (ASDs). Given that the amygdala is a component structure of the "social brain," several theoretical explanations compatible with amygdala dysfunction have been proposed to account for socio-emotional impairments in ASDs, including abnormal eye contact, gaze monitoring, face processing, mental state understanding, and empathy. Nevertheless, many theoretical accounts, based on the Amygdala Theory of Autism, fail to elucidate the complex pattern of impairments observed in this population, which extends beyond the social domain. As posited by the Relevance Detector theory (Sander et al., 2003), the human amygdala is a critical component of a brain circuit involved in the appraisal of self-relevant events that include, but are not restricted to, social stimuli. Here, we propose that the behavioral and social-emotional features of ASDs may be better understood in terms of a disruption in a "Relevance Detector Network" affecting the processing of stimuli that are relevant for the organism's self-regulating functions. In the present review, we will first summarize the main literature supporting the involvement of the amygdala in socio-emotional disturbances in ASDs. Next, we will present a revised version of the Amygdala Relevance Detector hypothesis and we will show that this theoretical framework can provide a better understanding of the heterogeneity of the impairments and symptomatology of ASDs. Finally, we will discuss some predictions of our model, and suggest new directions in the investigation of the role of the amygdala within the more generally disrupted cortical connectivity framework as a model of neural organization of the autistic brain.

The contribution of epigenetics to understanding genetic factors in autism

Autism spectrum disorder is a grouping of neurodevelopmental disorders characterized by deficits in social communication and language, as well as by repetitive and stereotyped behaviors. While the environment is believed to play a role in the development of autism spectrum disorder, there is now strong evidence for a genetic link to autism. Despite such evidence, studies investigating a potential single-gene cause for autism, although insightful, have been highly inconclusive. A consideration of an epigenetic approach proves to be very promising in clarifying genetic factors involved in autism. The present article is intended to provide a review of key findings pertaining to epigenetics in autism in such a way that a broader audience of individuals who do not have a strong background in genetics may better understand this highly specific and scientific content. Epigenetics refers to non-permanent heritable changes that alter expression of genes without altering the DNA sequence itself and considers the role of environment in this modulation of gene expression. This review provides a brief description of epigenetic processes, highlights evidence in the literature of epigenetic dysregulation in autism, and makes use of noteworthy findings to illustrate how a consideration of epigenetic factors can deepen our understanding of the development of autism. Furthermore, this discussion will present a promising new way for moving forward in the investigation of genetic factors within autism.

Exploring Links between Genotypes, Phenotypes, and Clinical Predictors of Response to Early Intensive Behavioral Intervention in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is amongst the most familial of psychiatric disorders. Twin and family studies have demonstrated a monozygotic concordance rate of 70-90%, dizygotic concordance of around 10%, and more than a 20-fold increase in risk for first-degree relatives. Despite major advances in the genetics of autism, the relationship between different aspects of the behavioral and cognitive phenotype and their underlying genetic liability is still unclear. This is complicated by the heterogeneity of autism, which exists at both genetic and phenotypic levels. Given this heterogeneity, one method to find homogeneous entities and link these with specific genotypes would be to pursue endophenotypes. Evidence from neuroimaging, eye tracking, and electrophysiology studies supports the hypothesis that, building on genetic vulnerability, ASD emerges from a developmental cascade in which a deficit in attention to social stimuli leads to impaired interactions with primary caregivers. This results in abnormal development of the neurocircuitry responsible for social cognition, which in turn adversely affects later behavioral and functional domains dependent on these early processes, such as language development. Such a model begets a heterogeneous clinical phenotype, and is also supported by studies demonstrating better clinical outcomes with earlier treatment. Treatment response following intensive early behavioral intervention in ASD is also distinctly variable; however, relatively little is known about specific elements of the clinical phenotype that may predict response to current behavioral treatments. This paper overviews the literature regarding genotypes, phenotypes, and predictors of response to behavioral intervention in ASD and presents suggestions for future research to explore linkages between these that would enable better identification of, and increased treatment efficacy for, ASD.

Autism spectrum disorders in children with functional defecation disorders

OBJECTIVE

To prospectively assess the prevalence of autism spectrum disorder (ASD) symptoms in children presenting with functional defecation disorders.

STUDY DESIGN

Children (age 4-12 years) with functional constipation or functional non-retentive fecal incontinence according to the Rome III criteria referred to a specialized outpatient clinic were included. Parents completed 2 validated ASD screening questionnaires about their child; the Social Responsiveness Scale (SRS) and the Social Communication Questionnaire-Lifetime (SCQ-L). A total SRS score of ≥ 51 is a strong indicator for the presence of ASD. On the SCQ-L, a score of ≥ 15 is suggestive for ASD.

RESULTS

In total, 242 patients (130 males, median age 7.9 years) were included. Of these, 91% were diagnosed with functional constipation and 9% with functional non-retentive fecal incontinence. Thirteen children (5.4%) had previously been diagnosed with ASD. Twenty-six children (11%) had both SRS and SCQ-L scores at or above cutoff points, strongly suggestive for the presence of ASD. Solely high SRS were present in 42 children (17%), whereas two children (1%) only had high SCQ-L scores. Altogether, 29% had ASD symptoms, indicated by SRS and/or SCQ-L scores at or above the cutoff values. These children were older than children without ASD symptoms and presented with a longer duration of symptoms.

CONCLUSIONS

A substantial number of children (29%) presenting with a functional defecation disorder at a tertiary hospital has concomitant ASD symptoms. Clinicians should be aware of ASD symptoms in children with functional defecation disorders.

Impaired thalamocortical connectivity in autism spectrum disorder: a study of functional and anatomical connectivity

The thalamus plays crucial roles in the development and mature functioning of numerous sensorimotor, cognitive and attentional circuits. Currently limited evidence suggests that autism spectrum disorder may be associated with thalamic abnormalities, potentially related to sociocommunicative and other impairments in this disorder. We used functional connectivity magnetic resonance imaging and diffusion tensor imaging probabilistic tractography to study the functional and anatomical integrity of thalamo-cortical connectivity in children and adolescents with autism spectrum disorder and matched typically developing children. For connectivity with five cortical seeds (prefontal, parieto-occipital, motor, somatosensory and temporal), we found evidence of both anatomical and functional underconnectivity. The only exception was functional connectivity with the temporal lobe, which was increased in the autism spectrum disorders group, especially in the right hemisphere. However, this effect was robust only in partial correlation analyses (partialling out time series from other cortical seeds), whereas findings from total correlation analyses suggest that temporo-thalamic overconnectivity in the autism group was only relative to the underconnectivity found for other cortical seeds. We also found evidence of microstructural compromise within the thalamic motor parcel, associated with compromise in tracts between thalamus and motor cortex, suggesting that the thalamus may play a role in motor abnormalities reported in previous autism studies. More generally, a number of correlations of diffusion tensor imaging and functional connectivity magnetic resonance imaging measures with diagnostic and neuropsychological scores indicate involvement of abnormal thalamocortical connectivity in sociocommunicative and cognitive impairments in autism spectrum disorder.

An electrophysiological investigation of interhemispheric transfer time in children and adolescents with high-functioning autism spectrum disorders

Little is known about the functional impact of putative deficits in white-matter connectivity across the corpus callosum (CC) in individuals with autism spectrum disorders (ASDs). We utilized the temporal sensitivity of event-related potentials to examine the interhemispheric transfer time (IHTT) of basic visual information across the CC in youth with high-functioning ASD relative to healthy controls. We conducted two experiments: a visual letter matching experiment (n = 46) and a visual picture matching experiment, (n = 48) and utilized both electrophysiological (N1 and P1 amplitudes and latencies) and behavioral [response times (RTs), error rates] indices of IHTT. There were no significant group differences on either experiment for RTs, error rates, or N1 and P1 latencies, suggesting that on basic tasks the timing of information flow across the CC may not be altered in high functioning ASD.

Increased gene expression of FOXP1 in patients with autism spectrum disorders

Background

Comparative gene expression profiling analysis is useful in discovering differentially expressed genes associated with various diseases, including mental disorders. Autism spectrum disorders (ASD) are a group of complex childhood-onset neurodevelopmental and genetic disorders characterized by deficits in language development and verbal communication, impaired reciprocal social interaction, and the presence of repetitive behaviors or restricted interests. The study aimed to identify novel genes associated with the pathogenesis of ASD.

Methods

We conducted comparative total gene expression profiling analysis of lymphoblastoid cell lines (LCL) between 16 male patients with ASD and 16 male control subjects to screen differentially expressed genes associated with ASD. We verified one of the differentially expressed genes, FOXP1, using real-time quantitative PCR (RT-qPCR) in a sample of 83 male patients and 83 male controls that included the initial 16 male patients and male controls, respectively.

Results

A total of 252 differentially expressed probe sets representing 202 genes were detected between the two groups, including 89 up- and 113 downregulated genes in the ASD group. RT-qPCR verified significant elevation of the FOXP1 gene transcript of LCL in a sample of 83 male patients (10.46 ± 11.34) compared with 83 male controls (5.17 ± 8.20, P = 0.001).

Conclusions

Comparative gene expression profiling analysis of LCL is useful in discovering novel genetic markers associated with ASD. Elevated gene expression of FOXP1 might contribute to the pathogenesis of ASD.

Clinical trial registration

Identifier: NCT00494754

Tic Disorders and Learning Disability: Clinical Characteristics, Cognitive Performance and Comorbidity

Tics are involuntary movements or sounds. Tourette syndrome is one of a family of tic disorders that affect around 1% of the population but which remains underrecognised in the community. In paediatric special education learning disability classes, the prevalence of individuals with tic disorders is around 20–45% — higher still in special education emotional/behavioural classes. Given the high rates of individuals with tic disorders in special education settings, as well as the unique challenges of working in an educational setting with a person with a tic disorder, it is incumbent upon professionals working in these settings to be cognisant of the possibility of tic disorders in this population. This review seeks to provide an overview of tic disorders and their association with learning and mental health difficulties. The review focuses on an exploration of factors underpinning the association between tic disorders and learning disabilities, including neurocognitive corollaries of tic disorders and the influence of common comorbidities, such as ADHD, as well as upon strategies to support individuals with tic disorders in the classroom.

Beyond autism: a baby siblings research consortium study of high-risk children at three years of age

OBJECTIVE

First-degree relatives of persons with an autism spectrum disorder (ASD) are at increased risk for ASD-related characteristics. As little is known about the early expression of these characteristics, this study characterizes the non-ASD outcomes of 3-year-old high-risk (HR) siblings of children with ASD.

METHOD

Two groups of children without ASD participated: 507 HR siblings and 324 low-risk (LR) control subjects (no known relatives with ASD). Children were enrolled at a mean age of 8 months, and outcomes were assessed at 3 years. Outcome measures were Autism Diagnostic Observation Schedule (ADOS) calibrated severity scores, and Mullen Verbal and Non-Verbal Developmental Quotients (DQ).

RESULTS

At 3 years, HR siblings without an ASD outcome exhibited higher mean ADOS severity scores and lower verbal and non-verbal DQs than LR controls. HR siblings were over-represented (21% HR versus 7% LR) in latent classes characterized by elevated ADOS severity and/or low to low-average DQs. The remaining HR siblings without ASD outcomes (79%) belonged to classes in which they were not differentially represented with respect to LR siblings.

CONCLUSIONS

Having removed a previously identified 18.7% of HR siblings with ASD outcomes from all analyses, HR siblings nevertheless exhibited higher mean levels of ASD severity and lower levels of developmental functioning than LR children. However, the latent class membership of four-fifths of the HR siblings was not significantly different from that of LR control subjects. One-fifth of HR siblings belonged to classes characterized by higher ASD severity and/or lower levels of developmental functioning. This empirically derived characterization of an early-emerging pattern of difficulties in a minority of 3-year-old HR siblings suggests the importance of developmental surveillance and early intervention for these children.

Clinical outcomes of an early intervention program for preschool children with Autism Spectrum Disorder in a community group setting

Background

Available evidence indicates that early intervention programs, such as the Early Start Denver Model (ESDM), can positively affect key outcomes for children with Autism Spectrum Disorder (ASD). However, programs involving resource intensive one-to-one clinical intervention are not readily available or deliverable in the community, resulting in many children with ASD missing out on evidence-based intervention during their early and most critical preschool years. This study evaluated the effectiveness of the ESDM for preschool-aged children with ASD using a predominantly group-based intervention in a community child care setting.

Methods

Participants were 26 children (21 male) with ASD with a mean age of 49.6 months. The ESDM, a comprehensive early intervention program that integrates applied behaviour analysis with developmental and relationship-based approaches, was delivered by trained therapists during the child’s attendance at a child care centre for preschool-aged children with ASD. Children received 15–20 hours of group-based, and one hour of one-to-one, ESDM intervention per week. The average intervention period was ten months. Outcome measures were administered pre- and post-intervention, and comprised a developmental assessment - the Mullen Scales of Early Learning (MSEL); and two parent-report questionnaires - the Social Communication Questionnaire (SCQ) and Vineland Adaptive Behaviours Scales–Second Edition (VABS-II).

Results

Statistically significant post-intervention improvements were found in children’s performance on the visual reception, receptive language and expressive language domains of the MSEL in addition to their overall intellectual functioning, as assessed by standardised developmental quotients. Parents reported significant increases in their child’s receptive communication and motor skills on the VABS-II, and a significant decrease in autism-specific features on the SCQ. These effects were of around medium size, and appeared to be in excess of what may have been expected due to maturation. Nonetheless, these results need to be confirmed in a controlled study.

Conclusions

This study suggests community dissemination of the ESDM using predominantly group-based intervention may be an effective intervention. Making the ESDM accessible to the wider ASD community in child care settings has the potential for significant clinical and economic benefits. Further studies are indicated in this area, including those with younger children, and which incorporate a control group and standardised ASD assessments.

Trial registration

This trial is registered with the Australian New Zealand Clinical Trials Registry: Registry number ACTRN12612000461897.

Psychometric properties of the Chinese version of the Autism Spectrum Quotient (AQ)

The Autism Spectrum Quotient (AQ) has been widely used for measuring autistic characteristics in parents of children with autism spectrum disorders (ASD). Nonetheless, its psychometric validity is yet to be justified. This study tested the factor structure of the AQ by means of principal component analysis and confirmatory factor analysis using, for the first time, data from 4192 Taiwanese parents (1208 with ASD children and 2984 with typically developing children). Results yielded a 35-item, 5-dimensional factor solution that had favorable psychometric characteristics (RMSEA = .054; NNFI = .962; CFI = .969) than any of the previously-published AQ factor solutions. Subscales of this new AQ-Chinese model were statistically and semantically coherent, namely: Socialness, Mindreading, Patterns, Attention to Details and Attention Switching. The psychometric properties of the AQ-Chinese did not change between clinic-based and community-based data suggesting good fitting for a continuum of autistic expression. Furthermore, the considerable overlap between the AQ-Chinese and the AQ factor structures derived previously using student samples indicated consistency in the manifestation of the autistic profile across different cultures and age groups. Group differences in the AQ-Chinese scores were in line with previous studies, i.e. males generally scored radically higher than females except in Attention to Details. Interestingly, mothers of ASD children reported lower total AQ scores than community mothers yet no significant group difference for the fathers. Important research and clinical implications pertinent to parents with children with ASD and the utility of the AQ were drawn.

Genomic and proteomic advances in autism research

Recent studies suggest that adult neural stem cells (NSCs) may play a role in the pathogenesis of a number of the developmental disorders subsumed under the term autism spectrum disorders (ASD) that have in common impaired social interaction, communication deficits, and stereotypical behavior or interests. Since there is no "unifying hypothesis" about the etiology and pathogenesis of ASD, several factors have been associated with ASD, including genetic factors, physical co-morbidity, disturbances of brain structure and function, biochemical anomalies, cognitive impairment, and disorders of speech and emotional development, mostly the lack of empathy. Most of disturbances of brain interconnectivity are regarded as main problem in autism. Since NSCs have a distinct life cycle in the mammalian brain consisting of proliferation, migration, arborization, integration into existing neuronal circuits, and myelinization, disturbances in NSCs differentiation is thought to be deleterious. In the current review, I will summarize the results of genomic and proteomic studies finding susceptibility genes and proteins for autism with regard to NSCs differentiation and maturation.

Identification of two inherited copy number variants in a male with autism supports two-hit and compound heterozygosity models of autism

Autism is a childhood-onset neurodevelopmental disorder with complex genetic mechanism underlying its etiology. Recent studies revealed that a few single de novo copy number variants of genomic DNA (copy number variants [CNVs]) are pathogenic and causal in some sporadic cases, adding support to the hypothesis that some sporadic autism might be caused by single rare mutation with large clinical effect. In this study, we report the detection of two novel private CNVs simultaneously in a male patient with autism. These two CNVs include a microduplication of ~4.5 Mb at chromosome 4q12-13.1 that was transmitted from his mother and a microdeletion of ~1.8 Mb at 5q32 that was transmitted from his father. Several genes such as LPHN3, POU4F3, SH3RF2, and TCERG1 mapped to these two regions have psychiatric implications. However, the parents had only mild degree of attention deficit symptoms but did not demonstrate any obvious autistic symptoms or psychopathology. Our findings indicate that each of these two CNVs alone may not be pathogenic enough to cause clinical symptoms in their respective carriers, and hence they can be transmitted within each individual family. However, concomitant presence of these two CNVs might result in the clinical phenotypes of the affected patient reported here. Thus, our report of this family may represent an example to show that two hits of CNV and the presence of compound heterozygosity might be important mechanisms underlying the pathogenesis of autism.

Pathogenetic model for Tourette syndrome delineates overlap with related neurodevelopmental disorders including Autism

Tourette syndrome (TS) is a highly heritable neuropsychiatric disorder characterised by motor and vocal tics. Despite decades of research, the aetiology of TS has remained elusive. Recent successes in gene discovery backed by rapidly advancing genomic technologies have given us new insights into the genetic basis of the disorder, but the growing collection of rare and disparate findings have added confusion and complexity to the attempts to translate these findings into neurobiological mechanisms resulting in symptom genesis. In this review, we explore a previously unrecognised genetic link between TS and a competing series of trans-synaptic complexes (neurexins (NRXNs), neuroligins (NLGNs), leucine-rich repeat transmembrane proteins (LRRTMs), leucine rich repeat neuronals (LRRNs) and cerebellin precursor 2 (CBLN2)) that links it with autism spectrum disorder through neurodevelopmental pathways. The emergent neuropathogenetic model integrates all five genes so far found to be uniquely disrupted in TS into a single pathogenetic chain of events described in context with clinical and research implications.

Elevated fecal short chain fatty acid and ammonia concentrations in children with autism spectrum disorder

BACKGROUND AND AIM

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder where a high frequency of gastrointestinal disturbance (e.g., constipation and diarrhea) is reported. As large bowel fermentation products can have beneficial or detrimental effects on health, these were measured in feces of children with and without ASD to examine whether there is an underlying disturbance in fermentation processes in the disorder.

METHODS

Fecal samples (48 h) were collected from children with ASD (n = 23), and without ASD (n = 31) of similar age. Concentrations of short chain fatty acids, phenols and ammonia were measured.

RESULTS

Fecal total short chain fatty acid concentrations were significantly higher in children with ASD compared to controls (136.6 ± 8.7 vs. 111.1 ± 6.6 mmol/kg). Moreover, when concentrations of fecal acetic, butyric, isobutyric, valeric, isovaleric and caproic acids were measured, all were significantly higher in children with ASD compared with controls except for caproic acid. The concentration of fecal ammonia was also significantly greater in ASD participants than controls (42.7 ± 3.3 vs. 32.3 ± 1.9 mmol/kg). Fecal phenol levels and pH did not differ between groups. Macronutrient intake, as determined from dietary records kept by caregivers, also did not differ significantly between study groups.

CONCLUSIONS

Our results suggest fermentation processes or utilization of fermentation products may be altered in children with ASD compared to children without ASD.

A functional connectivity-based classification approach to autism spectrum disorder: only as good (or bad) as available diagnostic criteria

Evaluation of: Anderson JS, Nielsen JA, Froehlich AL et al. Functional connectivity magnetic resonance imaging classification of autism. Brain 134, 3742–3754 (2011).

This study used functional connectivity detected from low-frequency fluctuations in functional MRI time series acquired during a resting state. Participants were adolescents and adults with autism spectrum disorder (ASD) and typically developing controls. Classification scores were used to predict group membership based on functional connectivity for a large number of regions of interest across the whole brain. Diagnostic prediction accuracy was approximately 75% overall. The results contribute to current knowledge of functional connectivity abnormalities in ASD, generally in support of underconnectivity theories. They are also promising with respect to the search for biomarkers of ASD that are needed to replace current behavior-based diagnostic criteria. While data from young children were not available for this study, findings appear to suggest that functional connectivity signatures may be more distinctively abnormal in children compared to adults with ASD.

Infant siblings and the investigation of autism risk factors

Infant sibling studies have been at the vanguard of autism spectrum disorders (ASD) research over the past decade, providing important new knowledge about the earliest emerging signs of ASD and expanding our understanding of the developmental course of this complex disorder. Studies focused on siblings of children with ASD also have unrealized potential for contributing to ASD etiologic research. Moving targeted time of enrollment back from infancy toward conception creates tremendous opportunities for optimally studying risk factors and risk biomarkers during the pre-, peri- and neonatal periods. By doing so, a traditional sibling study, which already incorporates close developmental follow-up of at-risk infants through the third year of life, is essentially reconfigured as an enriched-risk pregnancy cohort study. This review considers the enriched-risk pregnancy cohort approach of studying infant siblings in the context of current thinking on ASD etiologic mechanisms. It then discusses the key features of this approach and provides a description of the design and implementation strategy of one major ASD enriched-risk pregnancy cohort study: the Early Autism Risk Longitudinal Investigation (EARLI).

A review of candidate urinary biomarkers for autism spectrum disorder

CONTEXT

Autism is a complex, heterogeneous neurodevelopmental condition with a strong genetic component potentially impacted by various environmental factors influencing susceptibility. There are no reliable laboratory tests available to confirm an autism diagnosis.

OBJECTIVE

To examine the published literature and identify putative urinary biomarkers of autism.

METHODS

A comprehensive literature search was conducted using electronic bibliographic databases.

RESULTS

Putative autism biomarkers were identified that could be categorized according to the key theories that exist regarding the etiology of autism: gastrointestinal factors, immune dysregulation, heavy metal toxicity, neurotransmitter abnormalities, and oxidative stress.

CONCLUSION

There is scope for specific urinary biomarkers to be useful for identification of autistic metabolic phenotypes.

Epigenetic understanding of gene-environment interactions in psychiatric disorders: a new concept of clinical genetics

Epigenetics is a mechanism that regulates gene expression independently of the underlying DNA sequence, relying instead on the chemical modification of DNA and histone proteins. Although environmental and genetic factors were thought to be independently associated with disorders, several recent lines of evidence suggest that epigenetics bridges these two factors. Epigenetic gene regulation is essential for normal development, thus defects in epigenetics cause various rare congenital diseases. Because epigenetics is a reversible system that can be affected by various environmental factors, such as drugs, nutrition, and mental stress, the epigenetic disorders also include common diseases induced by environmental factors. In this review, we discuss the nature of epigenetic disorders, particularly psychiatric disorders, on the basis of recent findings: 1) susceptibility of the conditions to environmental factors, 2) treatment by taking advantage of their reversible nature, and 3) transgenerational inheritance of epigenetic changes, that is, acquired adaptive epigenetic changes that are passed on to offspring. These recently discovered aspects of epigenetics provide a new concept of clinical genetics.

Caenorhabditis elegans as an experimental tool for the study of complex neurological diseases: Parkinson's disease, Alzheimer's disease and autism spectrum disorder

The nematode Caenorhabditis elegans has a very well-defined and genetically tractable nervous system which offers an effective model to explore basic mechanistic pathways that might be underpin complex human neurological diseases. Here, the role C. elegans is playing in understanding two neurodegenerative conditions, Parkinson's and Alzheimer's disease (AD), and a complex neurological condition, autism, is used as an exemplar of the utility of this model system. C. elegans is an imperfect model of Parkinson's disease because it lacks orthologues of the human disease-related genes PARK1 and LRRK2 which are linked to the autosomal dominant form of this disease. Despite this fact, the nematode is a good model because it allows transgenic expression of these human genes and the study of the impact on dopaminergic neurons in several genetic backgrounds and environmental conditions. For AD, C. elegans has orthologues of the amyloid precursor protein and both human presenilins, PS1 and PS2. In addition, many of the neurotoxic properties linked with Aβ amyloid and tau peptides can be studied in the nematode. Autism spectrum disorder is a complex neurodevelopmental disorder characterised by impairments in human social interaction, difficulties in communication, and restrictive and repetitive behaviours. Establishing C. elegans as a model for this complex behavioural disorder is difficult; however, abnormalities in neuronal synaptic communication are implicated in the aetiology of the disorder. Numerous studies have associated autism with mutations in several genes involved in excitatory and inhibitory synapses in the mammalian brain, including neuroligin, neurexin and shank, for which there are C. elegans orthologues. Thus, several molecular pathways and behavioural phenotypes in C. elegans have been related to autism. In general, the nematode offers a series of advantages that combined with knowledge from other animal models and human research, provides a powerful complementary experimental approach for understanding the molecular mechanisms and underlying aetiology of complex neurological diseases.

The recycling endosome and its role in neurological disorders

The recycling endosome (RE) is an organelle in the endocytic pathway where plasma membranes (proteins and lipids) internalized by endocytosis are processed back to the cell surface for reuse. Endocytic recycling is the primary way for the cell to maintain constituents of the plasma membrane (Griffiths et al., 1989), i.e., to maintain the abundance of receptors and transporters on cell surfaces. Membrane traffic through the RE is crucial for several key cellular processes including cytokinesis and cell migration. In polarized cells, including neurons, the RE is vital for the generation and maintenance of the polarity of the plasma membrane. Many RE dependent cargo molecules are known to be important for neuronal function and there is evidence that improper function of key proteins in RE-associated pathways may contribute to the pathogenesis of neurological disorders, including Huntington's disease. The function of the RE in neurons is poorly understood. Therefore, there is need to understand how membrane dynamics in RE-associated pathways are affected or participate in the development or progression of neurological diseases. This review summarizes advances in understanding endocytic recycling associated with the RE, challenges in elucidating molecular mechanisms underlying RE function, and evidence for RE dysfunction in neurological disorders.