Recurrence Risk of Autism in Siblings and Cousins: A Multinational, Population-Based Study

Association between prenatal air pollutant exposure and autism spectrum disorders in young children: A matched case-control study in Canada

The direction and magnitude of association between maternal exposure to ambient air pollutants across gestational windows and offspring risk of autism spectrum disorders (ASD) remains unclear. We sought to evaluate the time-varying effects of prenatal air pollutant exposure on ASD. We conducted a matched case-control study of singleton term children born in Ontario, Canada from 1-Apr-2012 to 31-Dec-2016. Provincial birth registry data were linked with applied behavioural analysis services and ambient air pollutant datasets to ascertain prenatal exposure to nitrogen dioxide (NO2), ground-level ozone (O3), fine particulate matter (PM2.5), and ASD diagnoses. Covariate balance between cases and controls was established using coarsened exact matching. Conditional logistic regression was used to assess the association between prenatal air pollutant exposure and ASD. Distributed lag non-linear models (DLNM) were used to examine the effects of single-pollutant exposure by prenatal week. Sensitivity analyses were conducted to assess the impact of exposure period on the observed findings. The final sample included 1589 ASD cases and 7563 controls. Compared to controls, cases were more likely to be born to mothers living in urban areas, delivered by Caesarean section, and assigned male sex at birth. NO2 was a consistent and significant contributor to ASD risk after accounting for co-exposure to O3, PM2.5 and covariates. The odds ratio per interquartile range increase was 2.1 (95%CI 1.8-2.3) pre-conception, 2.2 (2.0-2.5) for the 1st trimester, 2.2 (1.9-2.5) for the 2nd trimester, and 2.1 (1.9-2.4) for the 3rd trimester. In contrast, findings for O3 and PM2.5 with ASD were inconsistent. Findings from DLNM and sensitivity analyses were similar. Exposure to NO2 before and during pregnancy was significantly associated with ASD in offspring. The relationship between prenatal O3 and PM2.5 exposure and ASD remains unclear. Further investigation into the combined effects of multi-pollutant exposure on child neurodevelopment is warranted.

Prenatal environmental risk factors for autism spectrum disorder and their potential mechanisms

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is globally increasing in prevalence. The rise of ASD can be partially attributed to diagnostic expansion and advocacy efforts; however, the interplay between genetic predisposition and modern environmental exposures is likely driving a true increase in incidence. A range of evidence indicates that prenatal exposures are critical. Infection during pregnancy, gestational diabetes, and maternal obesity are established risk factors for ASD. Emerging areas of research include the effects of maternal use of selective serotonin reuptake inhibitors, antibiotics, and exposure to toxicants during pregnancy on brain development and subsequent ASD. The underlying pathways of these risk factors remain uncertain, with varying levels of evidence implicating immune dysregulation, mitochondrial dysfunction, oxidative stress, gut microbiome alterations, and hormonal disruptions. This narrative review assesses the evidence of contributing prenatal environmental factors for ASD and associated mechanisms as potential targets for novel prevention strategies.

Family history of psychiatric conditions and development of siblings of children with autism

Younger siblings (SIBS) of children with autism exhibit a wide range of clinical and subclinical symptoms including social, cognitive, language, and adaptive functioning delays. Identifying factors linked with this phenotypic heterogeneity is essential for improving understanding of the underlying biology of the heterogenous outcomes and for early identification of the most vulnerable SIBS. Prevalence of neurodevelopmental (NDD) and neuropsychiatric disorders (NPD) is significantly elevated in families of children with autism. It remains unknown, however, if the family history associates with the developmental outcomes among the SIBS. We quantified history of the NDDs and NPDs commonly reported in families of children with autism using a parent interview and assessed autism symptoms, verbal, nonverbal, and adaptive skills in a sample of 229 SIBS. Multiple regression analyses were used to examine links between family history and phenotypic outcomes, whereas controlling for birth year, age, sex, demographics, and parental education. Results suggest that family history of schizophrenia, depression, anxiety, bipolar disorder, and intellectual disability associate robustly with dimensional measures of social affect, verbal and nonverbal IQ, and adaptive functioning in the SIBS. Considering family history of these disorders may improve efforts to predict long-term outcomes in younger siblings of children with autism and inform about familial factors contributing to high phenotypic heterogenetity in this cohort.

Familial Recurrence of Autism: Updates From the Baby Siblings Research Consortium

OBJECTIVES

Autism spectrum disorder (ASD) is estimated to be ∼10 times higher in children with versus without an autistic sibling in population-based studies. Prospective studies of infant siblings have revealed even higher familial recurrence rates. In the current prospective longitudinal study, we provide updated estimates of familial ASD recurrence using a multinational database of infants with older autistic siblings.

METHODS

Data were collated across 18 sites of the Baby Siblings Research Consortium, an international network studying the earliest manifestations of ASD. A total of 1605 infants with an older autistic sibling were followed from early in life to 3 years, when they were classified as ASD or non-ASD. Hierarchical generalized linear modeling, with site as a random effect, was used to examine predictors of recurrence in families and calculate likelihood ratios.

RESULTS

A total of 20.2% of siblings developed ASD, which is not significantly higher than the previously reported rate of 18.7%. Male infant sex and >1 older affected sibling were significant predictors of familial recurrence. Proband sex also influenced recurrence rates, with siblings of female probands significantly more likely to develop ASD than siblings of male probands. Race and maternal education were also associated with recurrence in families.

CONCLUSIONS

The familial recurrence rate of ASD, as measured in infant sibling studies, has not changed appreciably since previous estimates were made in 2011. Younger siblings of autistic children, particularly those who are male, have an affected female sibling, multiple affected siblings, or are impacted by social inequities, should be closely monitored and promptly referred for diagnostic evaluation.

Object Exploration and Manipulation in Infants at Typical vs. Elevated Likelihood for ASD: A Review

The present review considers the growing body of literature on fine motor skills in infants at elevated genetic likelihood (EL) for autism spectrum disorder (ASD). This area of study aims to identify crucial motor markers associated with the disorder, facilitating earlier and more accurate identification of ASD, using various experimental methodologies, including standardized assessments, observational measures, and technological tools. The reviewed evidence revealed distinct developmental trajectories in EL infants, marked by differences in fine motor skills and exploratory behaviors compared to typically developing infants. We discuss the developmental trajectory of fine motor skills in infants and their predictive value for later ASD diagnosis, highlighting the significance of fine motor skills as early indicators of ASD risk in infants and emphasizing the need for further research to elucidate their predictive value and underlying mechanisms.

Exposure to heavy metals in utero and autism spectrum disorder at age 3: a meta-analysis of two longitudinal cohorts of siblings of children with autism

BACKGROUND

Autism spectrum disorder (ASD) is a prevalent and heterogeneous neurodevelopmental disorder. Risk is attributed to genetic and prenatal environmental factors, though the environmental agents are incompletely characterized.

METHODS

In Early Autism Risk Longitudinal Investigation (EARLI) and Markers of Autism Risk in Babies Learning Early Signs (MARBLES), two pregnancy cohorts of siblings of children with ASD, urinary metals concentrations during two pregnancy time periods (< 28 weeks and ≥ 28 weeks of gestation) were measured using inductively coupled plasma mass spectrometry. At age three, clinicians assessed ASD with DSM-5 criteria. In an exposure-wide association framework, using multivariable log binomial regression, we examined each metal for association with ASD status, adjusting for gestational age at urine sampling, child sex, age at pregnancy, race/ethnicity and education. We meta-analyzed across the two cohorts.

RESULTS

In EARLI (n = 170) 17% of children were diagnosed with ASD, and 44% were classified as having non-neurotypical development (Non-TD). In MARBLES (n = 231), 21% were diagnosed with ASD, and 14% classified as Non-TD. During the first and second trimester period (< 28 weeks), having cadmium concentration over the level of detection was associated with 1.69 (1.08, 2.64) times higher risk of ASD, and 1.29 (0.95, 1.75)times higher risk of Non-TD. A doubling of first and second trimester cesium concentration was marginally associated with 1.89 (0.94, 3.80) times higher risk of ASD, and a doubling of third trimester cesium with 1.69 (0.97, 2.95) times higher risk of ASD.

CONCLUSION

Exposure in utero to elevated levels of cadmium and cesium, as measured in urine collected during pregnancy, was associated with increased risk of developing ASD.

The association between prenatal oxidative stress levels measured by isoprostanes and offspring neurodevelopmental outcomes at 36 months

Oxidative stress during pregnancy has been a mechanistic pathway implicated in autism development, yet few studies have examined this association directly. Here, we examined the association of prenatal levels of 8-iso-PGF2α, a widely used measure of oxidative stress, and several neurodevelopmental outcomes related to autism in children. Participants included 169 mother-child pairs from the Early Autism Risk Longitudinal Investigation (EARLI), which enrolled mothers who had an autistic child from a previous pregnancy and followed them through a subsequent pregnancy and until that child reached age 3 years. Maternal urine samples were collected during the second trimester of pregnancy and were later measured for levels of isoprostanes. Child neurodevelopmental assessments included the Mullen Scales of Early Learning (MSEL), the Social Responsiveness Scale (SRS), and the Vineland Adaptive Behavior Scale (VABS), and were conducted around 36 months of age. Primary analyses examined associations between interquartile range (IQR) increases in 8-iso-PGF2α levels, and total composite scores from each assessment using quantile regression. In adjusted analyses, we did not observe statistically significant associations, though estimates suggested modestly lower cognitive scores (β for MSEL = -3.68, 95% CI: -10.09, 2.70), and minor increases in autism-related trait scores (β for SRS T score = 1.68, 95% CI: -0.24, 3.60) with increasing 8-iso-PGF2α. These suggestive associations between decreased cognitive scores and increased autism-related traits with increasing prenatal oxidative stress point to the need for continued investigation in larger samples of the role of oxidative stress as a mechanistic pathway in autism and related neurodevelopmental outcomes.

Mid-childhood autism sibling recurrence in infants with a family history of autism

Autism sibling recurrence in prospective infant family history studies is ~20% at 3 years but systematic follow-up to mid-childhood is rare. In population and clinical cohorts autism is not recognized in some children until school-age or later. One hundred and fifty-nine infants with an older sibling with autism underwent research diagnostic assessments at 3 years and mid-childhood (6 to 12 years (mean 9)). We report the autism sibling recurrence rate in mid-childhood and compare developmental and behavioral profiles at mid-childhood and 3 years in those with earlier versus later recognized autism, and those who had, or had not, received a community autism diagnosis. The autism recurrence rate in this sample in mid-childhood was 37.1%, 95% CI [29.9%, 44.9%] and higher in boys than girls. Around half of those diagnosed with autism in mid-childhood had not received a diagnosis at 3 years. Later, diagnosis was more common in girls than boys. While some had sub-threshold symptoms at 3, in others late diagnosis followed a largely typical early presentation. Sibling recurrence based on community clinical diagnosis was 24.5%, 95% CI [18.4%, 31.9%]. Those who also had a community diagnosis tended to be older, have lower adaptive function and higher autism and inattention symptoms. Notwithstanding limitations of a single site study, modest sample size and limits to generalisability, autism sibling recurrence in family history infants may be higher in mid-childhood than in studies reporting diagnostic outcome at 3 years. Findings have implications for families and clinical services, and for prospective family history studies.

3-generation family histories of mental, neurologic, cardiometabolic, birth defect, asthma, allergy, and autoimmune conditions associated with autism: an open-source catalogue of findings

The relatively few conditions and family members investigated in autism family health history limits etiologic understanding. For more comprehensive understanding and hypothesis-generation we produced an open-source catalogue of autism associations with family histories of mental, neurologic, cardiometabolic, birth defect, asthma, allergy, and autoimmune conditions. All live births in Denmark, 1980-2012, of Denmark-born parents (1,697,231 births), and their 3-generation family members were followed through April 10, 2017 for each of 90 diagnoses (including autism), emigration or death. Adjusted hazard ratios (aHR) were estimated via Cox regression for each diagnosis-family member type combination, adjusting for birth year, sex, birth weight, gestational age, parental ages at birth, and number of family member types of index person; aHRs also calculated for sex-specific co-occurrence of each disorder. We obtained 6,462 individual family history aHRS across autism overall (26,840 autistic persons; 1.6% of births), by sex, and considering intellectual disability (ID); and 350 individual co-occurrence aHRS. Results are catalogued in interactive heat maps and down-loadable data files: https://ncrr-au.shinyapps.io/asd-riskatlas/ and interactive graphic summaries: https://public.tableau.com/views/ASDPlots_16918786403110/e-Figure5. While primarily for reference material or use in other studies (e.g., meta-analyses), results revealed considerable breadth and variation in magnitude of familial health history associations with autism by type of condition, family member type, sex of the family member, side of the family, sex of the index person, and ID status, indicative of diverse genetic, familial, and non-genetic autism etiologic pathways. Careful attention to sources of autism likelihood in family health history, aided by our open data resource, may accelerate understanding of factors underlying neurodiversity.

Shared familial risk for type 2 diabetes mellitus and psychiatric disorders: a nationwide multigenerational genetics study

BACKGROUND

Psychiatric disorders and type 2 diabetes mellitus (T2DM) are heritable, polygenic, and often comorbid conditions, yet knowledge about their potential shared familial risk is lacking. We used family designs and T2DM polygenic risk score (T2DM-PRS) to investigate the genetic associations between psychiatric disorders and T2DM.

METHODS

We linked 659 906 individuals born in Denmark 1990-2000 to their parents, grandparents, and aunts/uncles using population-based registers. We compared rates of T2DM in relatives of children with and without a diagnosis of any or one of 11 specific psychiatric disorders, including neuropsychiatric and neurodevelopmental disorders, using Cox regression. In a genotyped sample (iPSYCH2015) of individuals born 1981-2008 (n = 134 403), we used logistic regression to estimate associations between a T2DM-PRS and these psychiatric disorders.

RESULTS

Among 5 235 300 relative pairs, relatives of individuals with a psychiatric disorder had an increased risk for T2DM with stronger associations for closer relatives (parents:hazard ratio = 1.38, 95% confidence interval 1.35-1.42; grandparents: 1.14, 1.13-1.15; and aunts/uncles: 1.19, 1.16-1.22). In the genetic sample, one standard deviation increase in T2DM-PRS was associated with an increased risk for any psychiatric disorder (odds ratio = 1.11, 1.08-1.14). Both familial T2DM and T2DM-PRS were significantly associated with seven of 11 psychiatric disorders, most strongly with attention-deficit/hyperactivity disorder and conduct disorder, and inversely with anorexia nervosa.

CONCLUSIONS

Our findings of familial co-aggregation and higher T2DM polygenic liability associated with psychiatric disorders point toward shared familial risk. This suggests that part of the comorbidity is explained by shared familial risks. The underlying mechanisms still remain largely unknown and the contributions of genetics and environment need further investigation.

Views of Genetic Testing for Autism Among Autism Self-Advocates: A Qualitative Study

BACKGROUND

Autism self-advocates' views regarding genetic tests for autism are important, but critical questions about their perspectives arise.

METHODS

We interviewed 11 autism self-advocates, recruited through autism self-advocacy websites, for 1 h each.

RESULTS

Interviewees viewed genetic testing and its potential pros and cons through the lens of their own indiviudal perceived challenges, needs and struggles, especially concerning stigma and discrimination, lack of accommodations and misunderstandings from society about autism, their particular needs for services, and being blamed by others and by themselves for autistic traits. Their views of genetic testing tended not to be binary, but rather depended on how the genetic test results would be used. Interviewees perceived pros of genetic testing both in general and with regard to themselves (e.g., by providing "scientific proof" of autism as a diagnosis and possibly increasing availability of services). But they also perceived disadvantages and limitations of testing (e.g., possible eugenic applications). Participants distinguished between what they felt would be best for themselves and for the autistic community as a whole. When asked if they would undergo testing for themselves, if offered, interviewees added several considerations (e.g., undergoing testing because they support science in general). Interviewees were divided whether a genetic diagnosis would or should reduce self-blame, and several were wary of testing unless treatment, prevention or societal attitudes changed. Weighing these competing pros and cons could be difficult.

CONCLUSIONS

This study, the first to use in-depth qualitative interviews to assess views of autism self-advocates regarding genetic testing, highlights key complexities. Respondents felt that such testing is neither wholly good or bad in itself, but rather may be acceptable depending on how it is used, and should be employed in beneficial, not harmful ways. These findings have important implications for practice, education of multiple stakeholders, research, and policy.

Detection of autism spectrum disorder-related pathogenic trio variants by a novel structure-based approach

BACKGROUND

Glutamatergic synapse dysfunction is believed to underlie the development of Autism Spectrum Disorder (ASD) and Intellectual Disability (ID) in many individuals. However, identification of genetic markers that contribute to synaptic dysfunction in these individuals is notoriously difficult. Based on genomic analysis, structural modeling, and functional data, we recently established the involvement of the TRIO-RAC1 pathway in ASD and ID. Furthermore, we identified a pathological de novo missense mutation hotspot in TRIO's GEF1 domain. ASD/ID-related missense mutations within this domain compromise glutamatergic synapse function and likely contribute to the development of ASD/ID. The number of ASD/ID cases with mutations identified within TRIO's GEF1 domain is increasing. However, tools for accurately predicting whether such mutations are detrimental to protein function are lacking.

METHODS

Here we deployed advanced protein structural modeling techniques to predict potential de novo pathogenic and benign mutations within TRIO's GEF1 domain. Mutant TRIO-9 constructs were generated and expressed in CA1 pyramidal neurons of organotypic cultured hippocampal slices. AMPA receptor-mediated postsynaptic currents were examined in these neurons using dual whole-cell patch clamp electrophysiology. We also validated these findings using orthogonal co-immunoprecipitation and fluorescence lifetime imaging (FLIM-FRET) experiments to assay TRIO mutant overexpression effects on TRIO-RAC1 binding and on RAC1 activity in HEK293/T cells.

RESULTS

Missense mutations in TRIO's GEF1 domain that were predicted to disrupt TRIO-RAC1 binding or stability were tested experimentally and found to greatly impair TRIO-9's influence on glutamatergic synapse function. In contrast, missense mutations in TRIO's GEF1 domain that were predicted to have minimal effect on TRIO-RAC1 binding or stability did not impair TRIO-9's influence on glutamatergic synapse function in our experimental assays. In orthogonal assays, we find most of the mutations predicted to disrupt binding display loss of function but mutants predicted to disrupt stability do not reflect our results from neuronal electrophysiological data.

LIMITATIONS

We present a method to predict missense mutations in TRIO's GEF1 domain that may compromise TRIO function and test for effects in a limited number of assays. Possible limitations arising from the model systems employed here can be addressed in future studies. Our method does not provide evidence for whether these mutations confer ASD/ID risk or the likelihood that such mutations will result in the development of ASD/ID.

CONCLUSIONS

Here we show that a combination of structure-based computational predictions and experimental validation can be employed to reliably predict whether missense mutations in the human TRIO gene impede TRIO protein function and compromise TRIO's role in glutamatergic synapse regulation. With the growing accessibility of genome sequencing, the use of such tools in the accurate identification of pathological mutations will be instrumental in diagnostics of ASD/ID.

Impact of Receiving Genetic Diagnoses on Parents' Perceptions of Their Children with Autism and Intellectual Disability

To assess whether genetic test results identifying the cause of a child's autism, when accompanied by other neurodevelopmental disorders (NDD), including intellectual disability, alter how parents perceive and treat their child. 28 parents of 22 individuals with autism (mean age: 15 years), usually with other NDDs, were interviewed after receiving genetic diagnoses indicating a de novo mutation through the Simons Foundation Powering Autism Research for Knowledge study. Diagnosis of a de novo genetic variant can alter parental perceptions of offspring with autism and other NDDs. Parents often blamed their child less, saw their child as less in control of symptoms, and developed more patience, framing expectations accordingly. Parents had mixed feelings about receiving genetic diagnoses, with sadness sometimes accompanying reframed expectations. Genetic diagnoses could change views of the child among extended family members, teachers, social service agencies, insurers, and broader communities and society. Genetic testing might also reduce delays in diagnoses of autism among African American, Latino and other children. These data, the first to examine several critical aspects of how parents and others view children with autism and other NDDs after receiving genetic diagnoses, highlight vital needs for education of multiple stakeholders (including geneticists, other physicians, genetic counselors, parents, individuals with autism, social service agencies, insurers, policymakers, and the broader public), research (to include perspectives of extended family members, insurers, social service agencies and teachers) and practice (to increase recognition and awareness of the potential benefits and effects of genetic testing for such children).

Three year outcomes in infants with a family history of autism and/or attention deficit hyperactivity disorder

Background

Most research on early outcomes in infants with a family history (FH) of autism has focussed on categorically defined autism, although some have language and developmental delays. Less is known about outcomes in infants with a FH of attention deficit hyperactivity disorder (ADHD).

Methods

Infants with and without a FH of autism and/or ADHD, due to a first-degree relative with either or both conditions, were recruited at 5 or 10 months. Three year outcomes were characterised using latent profile analysis (LPA) across measures of cognitive ability, adaptive functioning and autism, ADHD and anxiety traits (n = 131). We additionally ran an LPA using only autism and ADHD measures, and the broader LPA in an independent cohort (n = 139) and in both cohorts combined (n = 270).

Results

A Low Developmental Level + High Behavioural Concerns class had elevated autism, ADHD and anxiety scores, low cognitive and adaptive function, and included all but one child with autism. A Low Developmental Level + Typical Behaviour class had average cognitive ability and typical behaviour but low adaptive function. A Typical Developmental Level + Some Behavioural Concerns class had average cognitive and adaptive function but slightly elevated behaviour scores. A High Developmental Level + Typical Behaviour class had above average cognitive ability and typical behaviour. All four LPAs identified classes characterised by combinations of either, or both, Low Development Level and elevated behaviour scores, as well as a typically developing class. No classes had elevated autism or ADHD traits in isolation.

Conclusions

Some infants with a FH of autism or ADHD have atypical developmental and behavioural outcomes, but do not show strong autism or ADHD traits in isolation. The field needs to recalibrate aims and methods to embrace the broader transdiagnostic pattern of outcomes seen in these infants.

Multimodal pathways to joint attention in infants with a familial history of autism

Joint attention (JA) is an early-developing behavior that allows caregivers and infants to share focus on an object. Deficits in JA, as measured through face-following pathways, are a defining feature of autism spectrum disorder (ASD) and are observable as early as 12 months of age in infants later diagnosed with ASD. However, recent evidence suggests that JA may be achieved through hand-following pathways by children with and without ASD. Development of JA through multimodal pathways has yet to be studied in infants with an increased likelihood of developing ASD. The current study investigated how 6-, 9- and 12-month-old infants with (FH+) and without (FH-) a family history of ASD engaged in JA. Parent-infant dyads played at home while we recorded the interaction over Zoom and later offline coded for hand movements and gaze. FH+ and FH- infants spent similar amounts of time in JA with their parents, but the cues available before JA were different. Parents of FH+ infants did more work to establish JA and used more face-following than hand-following pathways compared to parents of FH- infants, likely reflecting differences in infant motor or social behavior. These results suggest that early motor differences between FH+ and FH- infants may cascade into differences in social coordination.

Diversity and Classification of Genetic Variations in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental condition with symptoms that affect the whole personality and all aspects of life. Although there is a high degree of heterogeneity in both its etiology and its characteristic behavioral patterns, the disorder is well-captured along the autistic triad. Currently, ASD status can be confirmed following an assessment of behavioral features, but there is a growing emphasis on conceptualizing autism as a spectrum, which allows for establishing a diagnosis based on the level of support need, free of discrete categories. Since ASD has a high genetic predominance, the number of genetic variations identified in the background of the condition is increasing exponentially as genetic testing methods are rapidly evolving. However, due to the huge amount of data to be analyzed, grouping the different DNA variations is still challenging. Therefore, in the present review, a multidimensional classification scheme was developed to accommodate most of the currently known genetic variants associated with autism. Genetic variations have been grouped according to six criteria (extent, time of onset, information content, frequency, number of genes involved, inheritance pattern), which are themselves not discrete categories, but form a coherent continuum in line with the autism spectrum approach.

ECG Recordings as Predictors of Very Early Autism Likelihood: A Machine Learning Approach

In recent years, there has been a rise in the prevalence of autism spectrum disorder (ASD). The diagnosis of ASD requires behavioral observation and standardized testing completed by highly trained experts. Early intervention for ASD can begin as early as 1-2 years of age, but ASD diagnoses are not typically made until ages 2-5 years, thus delaying the start of intervention. There is an urgent need for non-invasive biomarkers to detect ASD in infancy. While previous research using physiological recordings has focused on brain-based biomarkers of ASD, this study investigated the potential of electrocardiogram (ECG) recordings as an ASD biomarker in 3-6-month-old infants. We recorded the heart activity of infants at typical and elevated familial likelihood for ASD during naturalistic interactions with objects and caregivers. After obtaining the ECG signals, features such as heart rate variability (HRV) and sympathetic and parasympathetic activities were extracted. Then we evaluated the effectiveness of multiple machine learning classifiers for classifying ASD likelihood. Our findings support our hypothesis that infant ECG signals contain important information about ASD familial likelihood. Amongthe various machine learning algorithms tested, KNN performed best according to sensitivity (0.70 ± 0.117), F1-score (0.689 ± 0.124), precision (0.717 ± 0.128), accuracy (0.70 ± 0.117, p-value = 0.02), and ROC (0.686 ± 0.122, p-value = 0.06). These results suggest that ECG signals contain relevant information about the likelihood of an infant developing ASD. Future studies should consider the potential of information contained in ECG, and other indices of autonomic control, for the development of biomarkers of ASD in infancy.

Neuron-specific transcriptomic signatures indicate neuroinflammation and altered neuronal activity in ASD temporal cortex

Autism spectrum disorder (ASD) is a highly heterogeneous disorder, yet transcriptomic profiling of bulk brain tissue has identified substantial convergence among dysregulated genes and pathways in ASD. However, this approach lacks cell-specific resolution. We performed comprehensive transcriptomic analyses on bulk tissue and laser-capture microdissected (LCM) neurons from 59 postmortem human brains (27 ASD and 32 controls) in the superior temporal gyrus (STG) of individuals ranging from 2 to 73 years of age. In bulk tissue, synaptic signaling, heat shock protein-related pathways, and RNA splicing were significantly altered in ASD. There was age-dependent dysregulation of genes involved in gamma aminobutyric acid (GABA) (GAD1 and GAD2) and glutamate (SLC38A1) signaling pathways. In LCM neurons, AP-1-mediated neuroinflammation and insulin/IGF-1 signaling pathways were upregulated in ASD, while mitochondrial function, ribosome, and spliceosome components were downregulated. GABA synthesizing enzymes GAD1 and GAD2 were both downregulated in ASD neurons. Mechanistic modeling suggested a direct link between inflammation and ASD in neurons, and prioritized inflammation-associated genes for future study. Alterations in small nucleolar RNAs (snoRNAs) associated with splicing events suggested interplay between snoRNA dysregulation and splicing disruption in neurons of individuals with ASD. Our findings supported the fundamental hypothesis of altered neuronal communication in ASD, demonstrated that inflammation was elevated at least in part in ASD neurons, and may reveal windows of opportunity for biotherapeutics to target the trajectory of gene expression and clinical manifestation of ASD throughout the human lifespan.

Novel maternal autoantibodies in autism spectrum disorder: Implications for screening and diagnosis

Introduction

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder for which early recognition is a major challenge. Autoantibodies against fetal brain antigens have been found in the blood of mothers of children with ASD (m-ASD) and can be transferred to the fetus where they can impact neurodevelopment by binding to fetal brain proteins. This study aims to identify novel maternal autoantibodies reactive against human fetal brain antigens, and explore their use as biomarkers for ASD screening and diagnosis.

Methods

A custom-made human fetal brain cDNA phage display library was constructed, and screened for antibody reactivity in m-ASD samples from the Simons Simplex Collection (SSC) of the Simons Foundation Autism Research Initiative (SFARI). Antibody reactivity against 6 identified antigens was determined in plasma samples of 238 m-ASD and 90 mothers with typically developing children (m-TD).

Results

We identified antibodies to 6 novel University Hasselt (UH)-ASD antigens, including three novel m-ASD autoantigens, i.e., ribosomal protein L23 (RPL23), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and calmodulin-regulated spectrin-associated protein 3 (CAMSAP3). Antibody reactivity against a panel of four of these targets was found in 16% of m-ASD samples, compared to 4% in m-TD samples (p = 0.0049).

Discussion

Maternal antibodies against 4 UH-ASD antigens could therefore provide a novel tool to support the diagnosis of ASD in a subset of individuals.

Elemental Dynamics in Hair Accurately Predict Future Autism Spectrum Disorder Diagnosis: An International Multi-Center Study

Autism spectrum disorder (ASD) is a neurodevelopmental condition diagnosed in approximately 2% of children. Reliance on the emergence of clinically observable behavioral patterns only delays the mean age of diagnosis to approximately 4 years. However, neural pathways critical to language and social functions develop during infancy, and current diagnostic protocols miss the age when therapy would be most effective. We developed non-invasive ASD biomarkers using mass spectrometry analyses of elemental metabolism in single hair strands, coupled with machine learning. We undertook a national prospective study in Japan, where hair samples were collected at 1 month and clinical diagnosis was undertaken at 4 years. Next, we analyzed a national sample of Swedish twins and, in our third study, participants from a specialist ASD center in the US. In a blinded analysis, a predictive algorithm detected ASD risk as early as 1 month with 96.4% sensitivity, 75.4% specificity, and 81.4% accuracy (n = 486; 175 cases). These findings emphasize that the dynamics in elemental metabolism are systemically dysregulated in autism, and these signatures can be detected and leveraged in hair samples to predict the emergence of ASD as early as 1 month of age.

Babies under 1 year with atypical development: Perspectives for preventive individuation and treatment

A baby's first year of life is a time of immense development and cerebral plasticity. Following today's research and clinical observation, the period of the first year of life provides a new challenge inasmuch it is presently clear that it is possible to identify developmental anomalies in this window of time. Effecting early screening procedures could prove very useful, especially where we find genetic vulnerabilities in brothers and sisters of autistic subjects. Interventions of this kind, already practiced by some Public Health systems, can mean taking early action and primary protective measures with significant impacts not only on the subjects (babies and family members) concerned, but also on the public purse. It is, therefore, essential to provide for specific professionalized procedures for psychologists, pediatricians and neuropsychologists to be introduced through personnel highly specialized in interventions during the first year of life.

High-Risk Siblings without Autism: Insights from a Clinical and Eye-Tracking Study

Joint attention (JA)-the human ability to coordinate our attention with that of other people-is impaired in the early stage of Autism Spectrum Disorder (ASD). However, little is known about the JA skills in the younger siblings of children with ASD who do not develop ASD at 36 months of age [high-risk (HR)-noASD]. In order to advance our understanding of this topic, a prospective multicenter observational study was conducted with three groups of toddlers (age range: 18-33 months): 17 with ASD, 19 with HR-noASD and 16 with typical development (TD). All subjects underwent a comprehensive clinical assessment and an eye-tracking experiment with pre-recorded stimuli in which the visual patterns during two tasks eliciting initiating joint attention (IJA) were measured. Specifically, fixations, transitions and alternating gaze were analyzed. Clinical evaluation revealed that HR-noASD subjects had lower non-verbal cognitive skills than TD children, while similar levels of restricted and repetitive behaviors and better social communication skills were detected in comparison with ASD children. Eye-tracking paradigms indicated that HR-noASD toddlers had visual patterns resembling TD in terms of target-object-to-face gaze alternations, while their looking behaviors were similar to ASD toddlers regarding not-target-object-to-face gaze alternations. This study indicated that high-risk, unaffected siblings displayed a shared profile of IJA-eye-tracking measures with both ASD patients and TD controls, providing new insights into the characterization of social attention in this group of toddlers.

Can the "female protective effect" liability threshold model explain sex differences in autism spectrum disorder?

Male sex is a strong risk factor for autism spectrum disorder (ASD). The leading theory for a "female protective effect" (FPE) envisions males and females have "differing thresholds" under a "liability threshold model" (DT-LTM). Specifically, this model posits that females require either a greater number or larger magnitude of risk factors (i.e., greater liability) to manifest ASD, which is supported by the finding that a greater proportion of females with ASD have highly penetrant genetic mutations. Herein, we derive testable hypotheses from the DT-LTM for ASD, investigating heritability, familial recurrence, correlation between ASD penetrance and sex ratio, population traits, clinical features, the stability of the sex ratio across diagnostic changes, and highlight other key prerequisites. Our findings reveal that several key predictions of the DT-LTM are not supported by current data, requiring us to establish a different conceptual framework for evaluating alternate models that explain sex differences in ASD.

The Clinical Implications of the Academic Performance of the Siblings of Individuals With Autism Spectrum Disorder

We all know that autism spectrum disorder (ASD) can affect academic performance. Many children with autism face different challenges at school. However, less attention is paid to the siblings of autistic children, who are at a high risk of ASD or the broad autism phenotype (BAP). Recent data also shows that many siblings of ASD children suffer from neurodevelopmental disorders, mental health problems as well as poor academic performance. This review will look at the possible etiologies of the poor school performance of autistic children's siblings, with an emphasis on the challenges they face. We will also highlight the clinical implications of these findings, and the possible solutions that can help this vulnerable group.

Sibling Influences on Trajectories of Maladaptive Behaviors in Autism

Siblings play an important role in the behavioral trajectories of individuals with autism spectrum disorder (ASD). While having siblings has been associated with positive outcomes in ASD, including stronger adaptive functioning, social and non-verbal communication, and theory of mind, little is known about the impact of siblings on more negative outcomes, such as maladaptive behaviors. To address this gap, the present longitudinal study tested sibling predictors of trajectories of maladaptive behaviors (e.g., teacher- and parent-reported hyperactivity, irritability, and social withdrawal) from childhood through early adulthood among individuals with ASD and non-spectrum delays. Multilevel models revealed that, while the mere presence of a sibling did not impact maladaptive behavior trajectories apart from teacher-reported hyperactivity, the diagnostic profile of the sibling (e.g., emotional/behavioral disorder, ASD, medical condition) emerged as an important predictor. Specifically, although findings varied across teacher and parent reports, more hyperactivity and irritability across time was identified when the sibling had diagnoses of an emotional/behavioral disorder, ASD, and/or a medical condition. Overall, this study provides novel insight into the broader family-level factors that influence the presentation of maladaptive behaviors across time and across contexts.

Deleterious Variation in BR Serine/Threonine Kinase 2 Classified a Subtype of Autism

Recently, deleterious variants in the BR serine/threonine kinase 2 (BRSK2) gene have been reported in patients with autism spectrum disorder (ASD), suggesting that BRSK2 is a new high-confidence ASD risk gene, which presents an opportunity to understand the underlying neuropathological mechanisms of ASD. In this study, we performed clinical and neurobehavioral evaluations of a proband with a de novo non-sense variant in BRSK2 (p.R222X) with other reported BRSK2 mutant patients. To validate BRSK2 as an ASD risk gene, we generated a novel brsk2b-deficient zebrafish line through CRISPR/Cas9 and characterized its morphological and neurobehavioral features as well as performed molecular analysis of neurogenesis-related markers. The proband displayed typical ASD behaviors and language and motor delay, which were similar to other published BRSK2 mutant patients. Morphologically, brsk2b^–/– larvae exhibited a higher embryonic mortality and rate of pericardium edema, severe developmental delay, and depigmentation as well as growth retardation in the early developmental stage. Behaviorally, brsk2b^–/– zebrafish displayed significantly decreased activity in open field tests and enhanced anxiety levels in light/dark tests and thigmotaxis analysis. Specifically, brsk2b^–/– zebrafish showed a prominent reduction of social interaction with peers and disrupted social cohesion among homogeneous groups. Molecularly, the mRNA expression levels of homer1b (a postsynaptic density scaffolding protein), and mbpa, mpz, and plp1b (molecular markers of oligodendrocytes and myelination) were increased in the brain tissues of adult brsk2b^–/– zebrafish, while the expression level of isl1a, a marker of motor neurons, was decreased. Taken together, for the first time, we established a novel brsk2b-deficient zebrafish model that showed prominent ASD-like behaviors. In addition, the disturbed mRNA expression levels of neurogenesis-related markers implied that the processes of postsynaptic signaling as well as oligodendrocytes and myelination may be involved. This discovery may suggest a path for further research to identify the underlying neuropathological mechanisms between BRSK2 and ASD.

Prediction of Communicative Disorders Linked to Autistic Spectrum Disorder Based on Early Psychomotor Analysis

This systematic review evaluated psychomotor differences between children with and without siblings who have autism spectrum disorder (ASD), as well as the most reliable psychomotor skills that can help predict ASD and its associated language disorders. Literature from 2005 to 2020 was searched using the following databases: PubMed, Trip Medical Database, Cochrane, Web of Science, Science Direct, and Brain. A total 11 papers were included. Fine motor skills and joint attention displayed reliable results in order to predict ASD and its associated language disorders. The period between the first and the second year of life was considered the most appropriate one for the assessment of psychomotor skills. The best period to predict language disorders and ASD diagnosis is around 36 months old.

Evaluating the interrelations between the autism polygenic score and psychiatric family history in risk for autism

Psychiatric family history or a high autism polygenic risk score (PRS) have been separately linked to autism spectrum disorder (ASD) risk. The study aimed to simultaneously consider psychiatric family history and individual autism genetic liability (PRS) in autism risk. We performed a case-control study of all Denmark singleton births, May 1981-December 2005, in Denmark at their first birthday and a known mother. Cases were diagnosed with ASD before 2013 and controls comprised a random sample of 30,000 births without ASD, excluding persons with non-Denmark-born parents, missing ASD PRS, non-European ancestry. Adjusted odds ratios (aOR) were estimated for ASD by PRS decile and by psychiatric history in parents or full siblings (8 mutually-exclusive categories) using logistic regression. Adjusted ASD PRS z-score least-squares means were estimated by psychiatric family history category. ASD risk (11,339 ASD cases; 20,175 controls) from ASD PRS was not substantially altered after accounting for psychiatric family history (e.g., ASD PRS 10th decile aOR: 2.35 (95% CI 2.11-2.63) before vs 2.11 (95% CI 1.91-2.40) after adjustment) nor from psychiatric family history after accounting for ASD PRS (e.g., ASD family history aOR: 6.73 (95% CI 5.89-7.68) before vs 6.32 (95% CI 5.53-7.22) after adjustment). ASD risk from ASD PRS varied slightly by psychiatric family history. While ASD risk from psychiatric family history was not accounted for by ASD PRS and vice versa, risk overlap between the two factors will likely increase as measures of genetic risk improve. The two factors are best viewed as complementary measures of family-based autism risk. LAY SUMMARY: Autism risk from a history of mental disorders in the immediate family was not explained by a measure of individual genetic risk (autism polygenic risk score) and vice versa. That is, genetic risk did not appear to overlap family history risk. As genetic measures for autism improve then the overlap in autism risk from family history versus genetic factors will likely increase, but further study may be needed to fully determine the components of risk and how they are inter-related between these key family factors. Meanwhile, the two factors may be best viewed as complementary measures of autism family-based risk.

Environmental exposures associated with elevated risk for autism spectrum disorder may augment the burden of deleterious de novo mutations among probands

Although the full aetiology of autism spectrum disorder (ASD) is unknown, familial and twin studies demonstrate high heritability of 60-90%, indicating a predominant role of genetics in the development of the disorder. The genetic architecture of ASD consists of a complex array of rare and common variants of all classes of genetic variation usually acting additively to augment individual risk. The relative contribution of heredity in ASD persists despite selective pressures against the classic autistic phenotype; a phenomenon thought to be explained, in part, by the incidence of spontaneous (or de novo) mutations. Notably, environmental exposures attributed as salient risk factors for ASD may play a causal role in the emergence of deleterious de novo variations, with several ASD-associated agents having significant mutagenic potential. To explore this hypothesis, this review article assesses published epidemiological data with evidence derived from assays of mutagenicity, both in vivo and in vitro, to determine the likely role such agents may play in augmenting the genetic liability in ASD. Broadly, these exposures were observed to elicit genomic alterations through one or a combination of: (1) direct interaction with genetic material; (2) impaired DNA repair; or (3) oxidative DNA damage. However, the direct contribution of these factors to the ASD phenotype cannot be determined without further analysis. The development of comprehensive prospective birth cohorts in combination with genome sequencing is essential to forming a causal, mechanistic account of de novo mutations in ASD that links exposure, genotypic alterations, and phenotypic consequences.

Diagnostic Yield and Economic Implications of Whole-Exome Sequencing for ASD Diagnosis in Israel

Whole-exome sequencing (WES) is an effective approach to identify the susceptibility of genetic variants of autism spectrum disorder (ASD). The Israel Ministry of Health supports WES as an adjunct tool for ASD diagnosis, despite its unclear diagnostic yield and cost effectiveness. To address this knowledge gap, we applied WES to a population-based sample of 182 Bedouin and Jewish children with ASD from southern Israel, and assessed its yield in a gene panel of 205 genes robustly associated with ASD. We then compared the incremental cost-effectiveness ratios (ICERs) for an ASD diagnosis by WES, chromosomal microarray analysis (CMA), and CMA + WES. Overall, 32 ASD candidate variants were detected in 28 children, corresponding to an overall WES diagnostic yield of 15.4%. Interestingly, the diagnostic yield was significantly higher for the Bedouin children than for the Jewish children, i.e., 27.6% vs. 11.1% (p = 0.036). The most cost-effective means for genetic testing was the CMA alone, followed closely by the CMA + WES strategy (ICER = USD 117 and USD 124.8 per child). Yet, WES alone could become more cost effective than the other two approaches if there was to be a 25% increase in its yield or a 50% decrease in its cost. These findings suggest that WES should be recommended to facilitate ASD diagnosis in Israel, especially for highly consanguineous populations, such as the Bedouin.

Genetic contributions to autism spectrum disorder

Autism spectrum disorder (autism) is a heterogeneous group of neurodevelopmental conditions characterized by early childhood-onset impairments in communication and social interaction alongside restricted and repetitive behaviors and interests. This review summarizes recent developments in human genetics research in autism, complemented by epigenetic and transcriptomic findings. The clinical heterogeneity of autism is mirrored by a complex genetic architecture involving several types of common and rare variants, ranging from point mutations to large copy number variants, and either inherited or spontaneous (de novo). More than 100 risk genes have been implicated by rare, often de novo, potentially damaging mutations in highly constrained genes. These account for substantial individual risk but a small proportion of the population risk. In contrast, most of the genetic risk is attributable to common inherited variants acting en masse, each individually with small effects. Studies have identified a handful of robustly associated common variants. Different risk genes converge on the same mechanisms, such as gene regulation and synaptic connectivity. These mechanisms are also implicated by genes that are epigenetically and transcriptionally dysregulated in autism. Major challenges to understanding the biological mechanisms include substantial phenotypic heterogeneity, large locus heterogeneity, variable penetrance, and widespread pleiotropy. Considerable increases in sample sizes are needed to better understand the hundreds or thousands of common and rare genetic variants involved. Future research should integrate common and rare variant research, multi-omics data including genomics, epigenomics, and transcriptomics, and refined phenotype assessment with multidimensional and longitudinal measures.

Optimal interpregnancy interval in autism spectrum disorder: A multi-national study of a modifiable risk factor

It is biologically plausible that risk of autism spectrum disorder (ASD) is elevated by both short and long interpregnancy intervals (IPI). We conducted a retrospective cohort study of singleton, non-nulliparous live births, 1998-2007 in Denmark, Finland, and Sweden (N = 925,523 births). Optimal IPI was defined as the IPI at which minimum risk was observed. Generalized additive models were used to estimate relative risks (RR) of ASD and 95% Confidence Intervals (CI). Population impact fractions (PIF) for ASD were estimated under scenarios for shifts in the IPI distribution. We observed that the association between ASD (N = 9302) and IPI was U-shaped for all countries. ASD risk was lowest (optimal IPI) at 35 months for all countries combined, and at 30, 33, and 39 months in Denmark, Finland, and Sweden, respectively. Fully adjusted RRs at IPIs of 6, 12, and 60 months were 1.41 (95% CI: 1.08, 1.85), 1.26 (95% CI: 1.02, 1.56), and 1.24 (95% CI: 0.98, 1.58) compared to an IPI of 35 months. Under the most conservative scenario PIFs ranged from 5% (95% CI: 1%-8%) in Denmark to 9% (95% CI: 6%-12%) in Sweden. The minimum ASD risk followed IPIs of 30-39 months across three countries. These results reflect both direct IPI effects and other, closely related social and biological pathways. If our results reflect biologically causal effects, increasing optimal IPIs and reducing their indications, such as unintended pregnancy and delayed age at first pregnancy has the potential to prevent a salient proportion of ASD cases. LAY SUMMARY: Waiting 35 months to conceive again after giving birth resulted in the least risk of autism. Shorter and longer intervals resulted in risks that were up to 50% and 85% higher, respectively. About 5% to 9% of autism cases might be avoided by optimizing birth spacing.

Prevalence and characteristics of autistic children attending autism centres in 2 major cities in Saudi Arabia: A cross-sectional study

OBJECTIVES

To assess the prevalence and characteristics of Autism Spectrum Disorder (ASD)-affected children attending autistic centers in 2 major cities in Saudi Arabia.

METHODS

A cross-sectional study, including ASD centers and schools (37 centers) in Makkah and Jeddah, Saudi Arabia was conducted between January and March 2020. Data were collected from records and parents of children with ASD using a questionnaire on sociodemographic, family history, consanguinity, severity, and maternal risk factors.

RESULTS

All centers in Makkah and Jeddah participated, with a total of 1,023 ASD children. The prevalence of ASD was 2.618 per 1,000 children for Jeddah, 3.68 per 1,000 children for Makkah and 2.81 per 1,000 children for both Jeddah and Makkah. There was no statistically significant relationship between the severity of ASD and sociodemographic, family and maternal risk factors. However, there was statistically significant relationship between severe ASD and ASD family history (p=0.029, OR: 3.46 and 95% CI 1.14 to 10.5).

CONCLUSIONS

The prevalence of ASD in Makkah and Jeddah was lower than the global prevalence of ASD. Individuals with a family history of ASD were more likely to have more severe ASD.

Prediction of Autism Risk From Family Medical History Data Using Machine Learning: A National Cohort Study From Denmark

Background

A family history of specific disorders (e.g., autism, depression, epilepsy) has been linked to risk for autism spectrum disorder (ASD). This study examines whether family history data could be used for ASD risk prediction.

Methods

We followed all Danish live births, from 1980 to 2012, of Denmark-born parents for an ASD diagnosis through April 10, 2017 (N = 1,697,231 births; 26,840 ASD cases). Linking each birth to three-generation family members, we identified 438 morbidity indicators, comprising 73 disorders reported prospectively for each family member. We tested various models using a machine learning approach. From the best-performing model, we calculated a family history risk score and estimated odds ratios and 95% confidence intervals for the risk of ASD.

Results

The best-performing model comprised 41 indicators: eight mental conditions (e.g., ASD, attention-deficit/hyperactivity disorder, neurotic/stress disorders) and nine nonmental conditions (e.g., obesity, hypertension, asthma) across six family member types; model performance was similar in training and test subsamples. The highest risk score group had 17.0% ASD prevalence and a 15.3-fold (95% confidence interval, 14.0-17.1) increased ASD risk compared with the lowest score group, which had 0.6% ASD prevalence. In contrast, individuals with a full sibling with ASD had 9.5% ASD prevalence and a 6.1-fold (95% confidence interval, 5.9-6.4) higher risk than individuals without an affected sibling.

Conclusions

Family history of multiple mental and nonmental conditions can identify more individuals at highest risk for ASD than only considering the immediate family history of ASD. A comprehensive family history may be critical for a clinically relevant ASD risk prediction framework in the future.

A white paper on a neurodevelopmental framework for drug discovery in autism and other neurodevelopmental disorders

In the last decade there has been a revolution in terms of genetic findings in neurodevelopmental disorders (NDDs), with many discoveries critical for understanding their aetiology and pathophysiology. Clinical trials in single-gene disorders such as fragile X syndrome highlight the challenges of investigating new drug targets in NDDs. Incorporating a developmental perspective into the process of drug development for NDDs could help to overcome some of the current difficulties in identifying and testing new treatments. This paper provides a summary of the proceedings of the 'New Frontiers Meeting' on neurodevelopmental disorders organised by the European College of Neuropsychopharmacology in conjunction with the Innovative Medicines Initiative-sponsored AIMS-2-TRIALS consortium. It brought together experts in developmental genetics, autism, NDDs, and clinical trials from academia and industry, regulators, patient and family associations, and other stakeholders. The meeting sought to provide a platform for focused communication on scientific insights, challenges, and methodologies that might be applicable to the development of CNS treatments from a neurodevelopmental perspective. Multidisciplinary translational consortia to develop basic and clinical research in parallel could be pivotal to advance knowledge in the field. Although implementation of clinical trials for NDDs in paediatric populations is widely acknowledged as essential, safety concerns should guide each aspect of their design. Industry and academia should join forces to improve knowledge of the biology of brain development, identify the optimal timing of interventions, and translate these findings into new drugs, allowing for the needs of users and families, with support from regulatory agencies.

Clinical and Translational Implications of an Emerging Developmental Substructure for Autism

A vast share of the population-attributable risk for autism relates to inherited polygenic risk. A growing number of studies in the past five years have indicated that inherited susceptibility may operate through a finite number of early developmental liabilities that, in various permutations and combinations, jointly predict familial recurrence of the convergent syndrome of social communication disability that defines the condition. Here, we synthesize this body of research to derive evidence for a novel developmental substructure for autism, which has profound implications for ongoing discovery efforts to elucidate its neurobiological causes, and to inform future clinical and biomarker studies, early interventions, and personalized approaches to therapy.

How Family Histories Can Inform Research About Germ Cell Exposures: The Example of Autism

Throughout the scientific literature, heritable traits are routinely presumed to be genetic in origin. However, as emerging evidence from the realms of genetic toxicology and epigenomics demonstrate, heritability may be better understood as encompassing not only DNA sequence passed down through generations, but also disruptions to the parental germ cells causing de novo mutations or epigenetic alterations, with subsequent shifts in gene expression and functions in offspring. The Beyond Genes conference highlighted advances in understanding these aspects at molecular, experimental and epidemiological levels. In this commentary I suggest that future research on this topic could be inspired by collecting parents' germ cell exposure histories, with particular attention to cases of families with multiple children suffering idiopathic disorders. In so doing I focus on the endpoint of autism spectrum disorders (ASD). Rates of this serious neurodevelopment disability have climbed around the world, a growing crisis that cannot be explained by diagnostic shifts. ASD's strong heritability has prompted a research program largely focused on DNA sequencing to locate rare and common variants, but decades of this gene-focused research have revealed surprisingly little about the molecular origins of the disorder. Based on my experience as the mother of two children with idiopathic autism, and as a research philanthropist and autism advocate, I suggest ways researchers might probe parental germ cell exposure histories to develop new hypotheses that may ultimately reveal sources of non-genetic heritability in a subset of idiopathic heritable pathologies.

Paediatric genomic testing: Navigating medicare rebatable genomic testing

Genomic testing for a genetic diagnosis is becoming standard of care for many children, especially those with a syndromal intellectual disability. While previously this type of specialised testing was performed mainly by clinical genetics teams, it is increasingly being 'mainstreamed' into standard paediatric care. With the introduction of a new Medicare rebate for genomic testing in May 2020, this type of testing is now available for paediatricians to order, in consultation with clinical genetics. Children must be aged less than 10 years with facial dysmorphism and multiple congenital abnormalities or have global developmental delay or moderate to severe intellectual disability. This rebate should increase the likelihood of a genetic diagnosis, with accompanying benefits for patient management, reproductive planning and diagnostic certainty. Similar to the introduction of chromosomal microarray into mainstream paediatrics, this genomic testing will increase the number of genetic diagnoses, however, will also yield more variants of uncertain significance, incidental findings, and negative results. This paper aims to guide paediatricians through the process of genomic testing, and represents the combined expertise of educators, clinical geneticists, paediatricians and genomic pathologists around Australia. Its purpose is to help paediatricians navigate choosing the right genomic test, consenting patients and understanding the possible outcomes of testing.

Expression analysis of selected genes involved in tryptophan metabolic pathways in Egyptian children with Autism Spectrum Disorder and learning disabilities

Autism Spectrum Disorder (ASD) and learning disabilities are neurodevelopmental disabilities characterized by dramatically increasing incidence rates, yet the exact etiology for these disabilities is not identified. Impairment in tryptophan metabolism has been suggested to participate in the pathogenesis of ASD, however, further validation of its involvement is required. Additionally, its role in learning disabilities is still uninvestigated. Our objective was to evaluate some aspects of tryptophan metabolism in ASD children (N = 45) compared to children with learning disabilities (N = 44) and healthy controls (N = 40) by measuring the expression levels of the MAOA, HAAO and AADAT genes using real-time RT-qPCR. We also aimed to correlate the expression patterns of these genes with parental ages at the time of childbirth, levels of serum iron, and vitamin D3 and zinc/copper ratio, as possible risk factors for ASD. Results demonstrated a significant decrease in the expression of the selected genes within ASD children (p < 0.001) relative to children with learning disabilities and healthy controls, which significantly associated with the levels of our targeted risk factors (p < 0.05) and negatively correlated to ASD scoring (p < 0.001). In conclusion, this study suggests that the expression of the MAOA, HAAO and AADAT genes may underpin the pathophysiology of ASD.

Früherkennung von Entwicklungsstörungen: Kanonisches Lallen (k)‌ein diagnostischer Marker‍(!)?

Zusammenfassung. Theoretischer Hintergrund: Forschungsergebnisse zum frühen Spracherwerb bei Kindern mit spät erkannten Entwicklungsstörungen sind inkonsistent und angesichts unterschiedlicher Forschungsparadigmen und Definitionen nur bedingt vergleichbar. Fragestellung: Ziel dieser Übersichtsarbeit ist es, das Potenzial früher verbaler Fähigkeiten, vor allem des kanonischen Lallens, als Marker zur Früherkennung von Autismus-Spektrum-Störung, Rett-Syndrom und Fragilem-X-Syndrom zu beschreiben. Methode: Übersichtsarbeit über retrospektive und prospektive Studien zu frühen verbalen Fähigkeiten in der Prodromalphase dieser Störungsbilder. Ergebnisse: Einige Kinder mit spät erkannten Entwicklungsstörungen erwerben das kanonische Lallen nach dem kritischen Zeitfenster von 6 bis 10 Monaten und/oder haben oft qualitative Veränderungen in ihren Lautäußerungen. Diskussion und Schlussfolgerung: Eine abweichende Entwicklung des kanonischen Lallens kann auf spätere atypische Entwicklung hinweisen. Als funktioneller Marker für die spezifische Früherkennung von Entwicklungsstörungen scheint dieser Erwerbsmeilenstein jedoch nicht geeignet. Linguistische und signalbasierte Detailanalysen frühkindlicher Vokalisationen könnten zukünftig einen entscheidenden Beitrag hierzu leisten.

Factors Affecting Family Compliance with Genetic Testing of Children Diagnosed with Autism Spectrum Disorder

There is broad consensus about the importance of post-diagnostic genetic testing for children with ASD. However, the extent of compliance with these tests and the factors affecting compliance have rarely been examined. We surveyed a sample of 114 families with a child with ASD in Israel, where such genetic testing is funded by the government. We found that only one-third of these families completed post-diagnosis genetic testing for their child. The main factor influencing compliance was the doctor's recommendation (OR 11.6; 95% CI 3.2-42.4; p < 0.001). Furthermore, > 50% of the non-compliant families reported that genetic testing was irrelevant to them. Our findings highlight the importance of providing clear recommendations and explanations regarding the benefits and relevance of post-diagnosis genetic testing for children with ASD.

Emerging functional connectivity differences in newborn infants vulnerable to autism spectrum disorders

Studies in animal models of autism spectrum disorders (ASD) suggest atypical early neural activity is a core vulnerability mechanism which alters functional connectivity and predisposes to dysmaturation of neural circuits. However, underlying biological changes associated to ASD in humans remain unclear. Results from functional connectivity studies of individuals diagnosed with ASD are highly heterogeneous, in part because of complex life-long secondary and/or compensatory events. To minimize these confounds and examine primary vulnerability mechanisms, we need to investigate very early brain development. Here, we tested the hypothesis that brain functional connectivity is altered in neonates who are vulnerable to this condition due to a family history of ASD. We acquired high temporal resolution multiband resting state functional magnetic resonance imaging (fMRI) in newborn infants with and without a first-degree relative with ASD. Differences in local functional connectivity were quantified using regional homogeneity (ReHo) analysis and long-range connectivity was assessed using distance correlation analysis. Neonates who have a first-degree relative with ASD had significantly higher ReHo within multiple resting state networks in comparison to age matched controls; there were no differences in long range connectivity. Atypical local functional activity may constitute a biomarker of vulnerability, that might precede disruptions in long range connectivity reported in older individuals diagnosed with ASD.

Genetic mechanisms of neurodevelopmental disorders

Neurodevelopmental disorders encompass a broad range of conditions, which include autism, epilepsy, and intellectual disability. These disorders are relatively common and have associated clinical and genetic heterogeneity. Technology has driven much of our understanding of these diseases and their genetic underlying mechanisms, particularly highlighted by the study of large cohorts with comparative genomic hybridization and the more recent implementation of next-generation sequencing (NGS). The mapping of copy number variants throughout the genome has highlighted the recurrent, highly penetrant, de novo variation in syndromic forms of neurodevelopmental disease. NGS of affected individuals and their parents led to a dramatic shift in our understanding as these studies showed that a significant proportion of affected individuals carry rare, de novo variants within single genes that explain their disease presentation. Deep sequencing studies further implicate mosaicism as another mechanism of disease. However, it has also become clear that while rare variants explain a significant proportion of sporadic neurodevelopmental disease, rare variation still does not fully account for the familial clustering and high heritability observed. Common variants, including those within these known disease genes, are also shown to contribute significantly to overall risk. There is also increasing awareness of the important contribution of epigenetic factors and gene-environment interactions.

General anesthesia, germ cells and the missing heritability of autism: an urgent need for research

Agents of general anesthesia (GA) are commonly employed in surgical, dental and diagnostic procedures to effectuate global suppression of the nervous system, but in addition to somatic targets, the subject's germ cells-from the embryonic primordial stage to the mature gametes-may likewise be exposed. Although GA is generally considered safe for most patients, evidence has accumulated that various compounds, in particular the synthetic volatile anesthetic gases (SVAGs) such as sevoflurane, can exert neurotoxic, genotoxic and epigenotoxic effects, with adverse consequences for cellular and genomic function in both somatic and germline cells. The purpose of this paper is to review the evidence demonstrating that GA, and in particular, SVAGs, may in some circumstances adversely impact the molecular program of germ cells, resulting in brain and behavioral pathology in the progeny born of the exposed cells. Further, we exhort the medical and scientific communities to undertake comprehensive experimental and epidemiological research programs to address this critical gap in risk assessment.