Current developments in the genetics of autism: from phenome to genome

Narrative Ability in Autism and First-Degree Relatives

Narrative is an important communication skill for sharing personal experiences and connecting with others. Narrative skills are often impacted in autism spectrum disorder (ASD) and have important consequences for social interactions and relationships. Subtle differences in narrative have also been reported among first-degree relatives of autistic individuals, suggesting that narrative may also be an etiologically important language-related skill that is influenced by genes associated with ASD. This study examined narrative ability and related visual attention during narration in ASD and first-degree relatives of individuals with ASD (siblings and parents) to understand how narrative and related attentional styles may be variably impacted across the spectrum of ASD genetic influence. Participants included 56 autistic individuals, 42 siblings of autistic individuals, 49 controls, 161 parents of autistic individuals, and 61 parent controls. Narratives were elicited using a wordless picture book presented on an eye tracker to record concurrent gaze. Findings revealed parallel patterns of narrative differences among ASD and sibling groups in the use of causal language to connect story elements and the use of cognitive and affective language. More subtle differences within the domain of causal language were evident in ASD parents. Parallel patterns in the ASD and sibling groups were also found for gaze during narration. Findings implicate causal language as a critical narrative skill that is impacted in ASD and may be reflective of ASD genetic influence in relatives. Gaze patterns during narration suggest similar attentional mechanisms associated with narrative among ASD families.

Differences in speech articulatory timing and associations with pragmatic language ability in autism

Background

Speech articulation difficulties have not traditionally been considered to be a feature of Autism Spectrum Disorder (ASD). In contrast, speech prosodic differences have been widely reported in ASD, and may even be expressed in subtle form among clinically unaffected first-degree relatives, representing the expression of underlying genetic liability. Some evidence has challenged this traditional dichotomy, suggesting that differences in speech articulatory mechanisms may be evident in ASD, and potentially related to perceived prosodic differences. Clinical measurement of articulatory skills has traditionally been phoneme-based, rather than by acoustic measurement of motor control. Subtle differences in articulatory/motor control, prosodic characteristics (acoustic), and pragmatic language ability (linguistic) may each be contributors to differences perceived by listeners, but the interrelationship is unclear. In this study, we examined the articulatory aspects of this relationship, in speech samples from individuals with ASD and their parents during narration.

Method

Using Speechmark® analysis, we examined articulatory landmarks, fine-grained representations of articulatory timing as series of laryngeal and vocal-tract gestures pertaining to prosodic elements crucial for conveying pragmatic information.

Results

Results revealed articulatory timing differences in individuals with ASD but not their parents, suggesting that although potentially not influenced by broader genetic liability to ASD, subtle articulatory differences may indeed be evident in ASD as the recent literature indicates. A follow-up path analysis detected associations between articulatory timing differences and prosody, and subsequently, pragmatic language ability.

Conclusion

Together, results suggest a complex relationship where subtle differences in articulatory timing may result in atypical acoustic signals, and serve as a distal mechanistic contributor to pragmatic language ability ASD.

Integrative Functional Genomic Analysis in Multiplex Autism Families from Kazakhstan

The study of extended pedigrees containing autism spectrum disorder- (ASD-) related broader autism phenotypes (BAP) offers a promising approach to the search for ASD candidate variants. Here, a total of 650,000 genetic markers were tested in four Kazakhstani multiplex families with ASD and BAP to obtain data on de novo mutations (DNMs), common, and rare inherited variants that may contribute to the genetic risk for developing autistic traits. The variants were analyzed in the context of gene networks and pathways. Several previously well-described enriched pathways were identified, including ion channel activity, regulation of synaptic function, and membrane depolarization. Perhaps these pathways are crucial not only for the development of ASD but also for ВАР. The results also point to several additional biological pathways (circadian entrainment, NCAM and BTN family interactions, and interaction between L1 and Ankyrins) and hub genes (CFTR, NOD2, PPP2R2B, and TTR). The obtained results suggest that further exploration of PPI networks combining ASD and BAP risk genes can be used to identify novel or overlooked ASD molecular mechanisms.

Prenatal exposure to paternal smoking and likelihood for autism spectrum disorder

LAY ABSTRACT

What is Already Known about This Subject: Genetics, (including de novo mutations), environmental factors (including toxic exposures), and their interactions impact autism spectrum disorder etiology. Paternal smoking is a candidate risk for autism spectrum disorder due to biological plausibility, high prevalence, and potential intervention.What This Study Adds: This original study and its replication confirms that paternal factors can substantially contribute to autism spectrum disorder risk for their offspring. It specifically indicates that paternal smoking both before and during pregnancy contributes significantly to autism spectrum disorder risk.Implications for practice, research, or policy: Smoking prevention, especially in pregnancy planning, may decrease autism spectrum disorder risk in offspring.

microRNAs and Gene-Environment Interactions in Autism: Effects of Prenatal Maternal Stress and the SERT Gene on Maternal microRNA Expression

Background: Genetics and environment both are critical in autism spectrum disorder (ASD), but their interaction (G × E) is less understood. Numerous studies have shown higher incidence of stress exposures during pregnancies with children later diagnosed with ASD. However, many stress-exposed mothers have unaffected children. The serotonin transporter (SERT) gene affects stress reactivity. Two independent samples have shown that the association between maternal stress exposure and ASD is greatest with maternal presence of the SERT short (S)-allele (deletion in the promoter region). MicroRNAs play a regulatory role in the serotonergic pathway and in prenatal stress and are therefore potential mechanistic targets in this setting. Design/methods: We profiled microRNA expression in blood from mothers of children with ASD, with known stress exposure during pregnancy. Samples were divided into groups based on SERT genotypes (LL/LS/SS) and prenatal stress level (high/low). Results: Two thousand five hundred mature microRNAs were examined. The ANOVA analysis showed differential expression (DE) of 119 microRNAs; 90 were DE in high- vs. low-stress groups (stress-dependent). Two (miR-1224-5p, miR-331-3p) were recently reported by our group to exhibit stress-dependent expression in rodent brain samples from embryos exposed to prenatal stress. Another, miR-145-5p, is associated with maternal stress. Across SERT genotypes, with high stress exposure, 20 significantly DE microRNAs were detected, five were stress-dependent. These microRNAs may be candidates for stress × SERT genotype interactions. This is remarkable as these changes were from mothers several years after stress-exposed pregnancies. Conclusions: Our study provides evidence for epigenetic alterations in relation to a G × E model (prenatal maternal stress × SERT gene) in ASD.

Lifelong Tone Language Experience does not Eliminate Deficits in Neural Encoding of Pitch in Autism Spectrum Disorder

Atypical pitch processing is a feature of Autism Spectrum Disorder (ASD), which affects non-tone language speakers' communication. Lifelong auditory experience has been demonstrated to modify genetically-predisposed risks for pitch processing. We examined individuals with ASD to test the hypothesis that lifelong auditory experience in tone language may eliminate impaired pitch processing in ASD. We examined children's and adults' Frequency-following Response (FFR), a neurophysiological component indexing early neural sensory encoding of pitch. Univariate and machine-learning-based analytics suggest less robust pitch encoding and diminished pitch distinctions in the FFR from individuals with ASD. Contrary to our hypothesis, results point to a linguistic pitch encoding impairment associated with ASD that may not be eliminated even by lifelong sensory experience.

Prenatal Stress and Maternal Immune Dysregulation in Autism Spectrum Disorders: Potential Points for Intervention

BACKGROUND

Genetics is a major etiological contributor to autism spectrum disorder (ASD). Environmental factors, however, also appear to contribute. ASD pathophysiology due to gene x environment is also beginning to be explored. One reason to focus on environmental factors is that they may allow opportunities for intervention or prevention.

METHODS AND RESULTS

Herein, we review two such factors that have been associated with a significant proportion of ASD risk, prenatal stress exposure and maternal immune dysregulation. Maternal stress susceptibility appears to interact with prenatal stress exposure to affect offspring neurodevelopment. We also explore how maternal stress may interact with the microbiome in the neurodevelopmental setting. Additionally, understanding of the impact of maternal immune dysfunction on ASD has recently been advanced by recognition of specific fetal brain proteins targeted by maternal autoantibodies, and identification of unique mid-gestational maternal immune profiles. This might also be interrelated with maternal stress exposure. Animal models have been developed to explore pathophysiology targeting each of these factors.

CONCLUSION

We are beginning to understand the behavioral, pharmacopathological, and epigenetic effects related to these interactions, and we are beginning to explore potential mitigating factors. Continued growth in understanding of these mechanisms may ultimately allow for the identification of multiple potential targets for prevention or intervention for this subset of environmental-associated ASD cases.

Prenatal Stress, Maternal Immune Dysregulation, and Their Association With Autism Spectrum Disorders

PURPOSE OF REVIEW

While genetic factors are a major etiological contributor to autism spectrum disorder (ASD), evidence also supports a role for environmental factors. Herein, we will discuss two such factors that have been associated with a significant proportion of ASD risk: prenatal stress exposure and maternal immune dysregulation, and how sex and gender relate to these factors.

RECENT FINDINGS

Recent evidence suggests that maternal stress susceptibility interacts with prenatal stress exposure to affect offspring neurodevelopment. Additionally, understanding of the impact of maternal immune dysfunction on ASD has recently been advanced by recognition of specific fetal brain proteins targeted by maternal autoantibodies, and identification of unique mid-gestational maternal immune profiles. Animal models have been developed to explore pathophysiology targeting both of these factors, with limited sex-specific effects observed. While prenatal stress and maternal immune dysregulation are associated with ASD, most cases of these prenatal exposures do not result in ASD, suggesting interaction with multiple other risks. We are beginning to understand the behavioral, pharmacopathological, and epigenetic effects related to these interactions, as well as potential mitigating factors. Sex differences of these risks have been understudied but are crucial for understanding the higher prevalence of ASD in boys. Continued growth in understanding of these mechanisms may ultimately allow for the identification of multiple potential points for prevention or intervention, and for a personalized medicine approach for this subset of environmental-associated ASD cases.

AutismKB 2.0: a knowledgebase for the genetic evidence of autism spectrum disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder with strong genetic contributions. To provide a comprehensive resource for the genetic evidence of ASD, we have updated the Autism KnowledgeBase (AutismKB) to version 2.0. AutismKB 2.0 integrates multiscale genetic data on 1379 genes, 5420 copy number variations and structural variations, 11 669 single-nucleotide variations or small insertions/deletions (SNVs/indels) and 172 linkage regions. In particular, AutismKB 2.0 highlights 5669 de novo SNVs/indels due to their significant contribution to ASD genetics and includes 789 mosaic variants due to their recently discovered contributions to ASD pathogenesis. The genes and variants are annotated extensively with genetic evidence and clinical evidence. To help users fully understand the functional consequences of SNVs and small indels, we provided comprehensive predictions of pathogenicity with iFish, SIFT, Polyphen etc. To improve user experiences, the new version incorporates multiple query methods, including simple query, advanced query and batch query. It also functionally integrates two analytical tools to help users perform downstream analyses, including a gene ranking tool and an enrichment analysis tool, KOBAS. AutismKB 2.0 is freely available and can be a valuable resource for researchers.

Adult Autism Subthreshold Spectrum (AdAS Spectrum): Validation of a questionnaire investigating subthreshold autism spectrum

AIM

Increasing literature has shown the usefulness of a dimensional approach to autism. The present study aimed to determine the psychometric properties of the Adult Autism Subthreshold Spectrum (AdAS Spectrum), a new questionnaire specifically tailored to assess subthreshold forms of autism spectrum disorder (ASD) in adulthood.

METHODS

102 adults endorsing at least one DSM-5 symptom criterion for ASD (ASDc), 143 adults diagnosed with a feeding and eating disorder (FED), and 160 subjects with no mental disorders (CTL), were recruited from 7 Italian University Departments of Psychiatry and administered the following: SCID-5, Autism-Spectrum Quotient (AQ), Ritvo Autism and Asperger Diagnostic Scale 14-item version (RAADS-14), and AdAS Spectrum.

RESULTS

The AdAS Spectrum demonstrated excellent internal consistency for the total score (Kuder-Richardson's coefficient=.964) as well as for five out of seven domains (all coefficients>.80) and sound test-retest reliability (ICC=.976). The total and domain AdAS Spectrum scores showed a moderate to strong (>.50) positive correlation with one another and with the AQ and RAADS-14 total scores. ASDc subjects reported significantly higher AdAS Spectrum total scores than both FED (p<.001) and CTL (p<.001), and significantly higher scores on the Childhood/adolescence, Verbal communication, Empathy, Inflexibility and adherence to routine, and Restricted interests and rumination domains (all p<.001) than FED, while on all domains compared to CTL. CTL displayed significantly lower total and domain scores than FED (all p<.001). A significant effect of gender emerged for the Hyper- and hyporeactivity to sensory input domain, with women showing higher scores than men (p=.003). A Diagnosis* Gender interaction was also found for the Verbal communication (p=.019) and Empathy (p=.023) domains. When splitting the ASDc in subjects with one symptom criterion (ASD₁) and those with a ASD, and the FED in subjects with no ASD symptom criteria (FED₀) and those with one ASD symptom criterion (FED₁)_, a gradient of severity in AdAS Spectrum scores from CTL subjects to ASD patients, across FED₀, ASD₁, FED₁ was shown.

CONCLUSIONS

The AdAS Spectrum showed excellent internal consistency and test-retest reliability and strong convergent validity with alternative dimensional measures of ASD. The questionnaire performed differently among the three diagnostic groups and enlightened some significant effects of gender in the expression of autistic traits.

The Genetic Overlap of Attention-Deficit/Hyperactivity Disorder and Autistic-like Traits: an Investigation of Individual Symptom Scales and Cognitive markers

Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorders (ASDs) frequently co-occur. However, due to previous exclusionary diagnostic criteria, little is known about the underlying causes of this covariation. Twin studies assessing ADHD symptoms and autistic-like traits (ALTs) suggest substantial genetic overlap, but have largely failed to take into account the genetic heterogeneity of symptom subscales. This study aimed to clarify the phenotypic and genetic relations between ADHD and ASD by distinguishing between symptom subscales that characterise the two disorders. Moreover, we aimed to investigate whether ADHD-related cognitive impairments show a relationship with ALT symptom subscales; and whether potential shared cognitive impairments underlie the genetic risk shared between the ADHD and ALT symptoms. Multivariate structural equation modelling was conducted on a population-based sample of 1312 twins aged 7–10. Social-communication ALTs correlated moderately with both ADHD symptom domains (phenotypic correlations around 0.30) and showed substantial genetic overlap with both inattention and hyperactivity-impulsivity (genetic correlation = 0.52 and 0.44, respectively). In addition to previously reported associations with ADHD traits, reaction time variability (RTV) showed significant phenotypic (0.18) and genetic (0.32) association with social-communication ALTs. RTV captured a significant proportion (24 %) of the genetic influences shared between inattention and social-communication ALTs. Our findings suggest that social-communication ALTs underlie the previously observed phenotypic and genetic covariation between ALTs and ADHD symptoms. RTV is not specific to ADHD symptoms, but is also associated with social-communication ALTs and can, in part, contribute to an explanation of the co-occurrence of ASD and ADHD.

Genetics of Autism Spectrum Disorder: Current Status and Possible Clinical Applications

Autism spectrum disorder (ASD) is one of the most complex behavioral disorders with a strong genetic influence. The objectives of this article are to review the current status of genetic research in ASD, and to provide information regarding the potential candidate genes, mutations, and genetic loci possibly related to pathogenesis in ASD. Investigations on monogenic causes of ASD, candidate genes among common variants, rare de novo mutations, and copy number variations are reviewed. The current possible clinical applications of the genetic knowledge and their future possibilities are highlighted.

CNTNAP2 gene in high functioning autism: no association according to family and meta-analysis approaches

The Contactin Associated Protein-like 2 (CNTNAP2) gene has been discussed to be associated with different symptoms of autism spectrum disorders (ASDs) and other neurodevelopmental disorders. We aimed to elucidate the genetic association of CNTNAP2 within high functioning ASD (HFA), focusing on autism specific symptoms and reducing intelligence related factors. Furthermore, we compared our findings conducting a meta-analysis in patients with ASD and HFA only. A case-control association study was performed for HFA (HFA, n = 105; controls, n = 133). Moreover, we performed a family-based association study (DFAM) analysis (HFA, n = 44; siblings, n = 57). Individuals were genotyped for the two most frequently reported single nucleotide polymorphisms (SNPs) in the CNTNAP2 gene (rs2710102, rs7794745). Furthermore, a meta-analysis using the MIX2 software integrated our results with previously published data. A significant association for the carriers of the T-allele of the rs7794745 with HFA was found in the case-control sample [OR = 1.547; (95 % CI 1.056-2.266); p = 0.025]. No association could be found by DFAM with any of the CNTNAP2 SNPs with HFA. The meta-analysis of both SNPs did not show a significant association with either ASD or with HFA. Overall, including case-control, sibs, and meta-analysis, we could not detect any significant association with the CNTNAP2 gene and HFA. Our results point in the direction that CNTNAP2 may not play a major role in HFA, but rather seems to have a significance in neurodevelopmental disorders or in individuals displaying intellectual delays.

Developmental white matter microstructure in autism phenotype and corresponding endophenotype during adolescence

During adolescence, white matter microstructure undergoes an important stage of development. It is hypothesized that the alterations of brain connectivity that have a key role in autism spectrum conditions (ASCs) may interact with the development of white matter microstructure. This interaction may be present beyond the phenotype of autism in siblings of individuals with ASC, who are 10 to 20 times more likely to develop certain forms of ASC. We use diffusion tensor imaging to examine how white matter microstructure measurements correlate with age in typically developing individuals, and how this correlation differs in n=43 adolescents with ASC and their n=38 siblings. Correlations observed in n=40 typically developing individuals match developmental changes noted in previous longitudinal studies. In comparison, individuals with ASC display weaker negative correlation between age and mean diffusivity in a broad area centred in the right superior longitudinal fasciculus. These differences may be caused either by increased heterogeneity in ASC or by temporal alterations in the group's developmental pattern. Siblings of individuals with ASC also show diminished negative correlation between age and one component of mean diffusivity-second diffusion eigenvalue-in the right superior longitudinal fasciculus. As the observed differences match for location and correlation directionality in our comparison of typically developing individuals to those with ASC and their siblings, we propose that these alterations constitute a part of the endophenotype of autism.

Broader autism phenotype in mothers predicts social responsiveness in young children with autism spectrum disorders

AIMS

The aim of this study was to identify phenotypes in mothers and fathers that are specifically associated with disturbances in reciprocal social interactions and communication in their young children with autism spectrum disorder (ASD) in a Japanese sample.

METHODS

Autistic traits in parents were evaluated using the Autism-spectrum Quotient (AQ), the Empathy Quotient (EQ) and the Systemizing Quotient (SQ) in 88 parents (44 mothers and corresponding fathers) of children with ASD and in 60 parents (30 mothers and corresponding fathers) of typically developing (TD) children. For the measurement of autistic traits in children, we employed the Social Responsiveness Scale (SRS).

RESULTS

In two of the five AQ subscales (social skills and communication), the parents of ASD children scored significantly higher than did the parents of TD children, regardless of whether the parent was a mother or a father. In addition, in mothers of ASD children, there were significant positive correlations between two of the five AQ subscales (attention-switching and communication) and the SRS T-score in their children.

CONCLUSIONS

This is the first study to demonstrate that the social skills and communication subscales in the AQ are more sensitive as autism traits in a Japanese sample and to demonstrate that some autistic traits in mothers are specifically associated with disturbances in the social ability of their young children with ASD, as measured by the SRS score. Further study is necessary to determine whether these results were caused by genetic or environmental factors.

Association of Copy Number Variations in Autism Spectrum Disorders: A Systematic Review

Autism spectrum disorders (ASDs) are characterized by language impairments, social deficits, and repetitive behaviors. The onset of symptoms occurs by the age of 3 and shows a lifelong persistence. Genetics plays a major role in the etiology of ASD. Except genetics, several potential risk factors (environmental factors and epigenetics) may contribute to ASD. Copy number variations (CNVs) are the most widespread structural variations in the human genome. These variations can alter the genome structure either by deletion or by duplication. CNVs can be de novo or inherited. Chromosomal rearrangements have been detected in 5–10% of the patients with ASD and recently copy number changes ranging from a few kilobases (kb) to several megabases (Mb) in size have been reported. Recent data have also revealed that submicroscopic CNVs can have a role in ASD, and de novo CNVs seem to be a more common risk factor in sporadic compared with inherited forms of ASD. CNVs are being implicated as a contributor to the pathophysiology of complex neurodevelopmental disorders and they can affect a wide range of human phenotypes including mental retardation (MR), autism, neuropsychiatric disorders, and susceptibility to other complex traits such as HIV, Crohn’s disease, and psoriasis. This review emphasizes the major CNVs reported to date in ASD.

Abnormal Neural Activation to Faces in the Parents of Children with Autism

Parents of children with an autism spectrum disorder (ASD) show subtle deficits in aspects of social behavior and face processing, which resemble those seen in ASD, referred to as the "Broad Autism Phenotype " (BAP). While abnormal activation in ASD has been reported in several brain structures linked to social cognition, little is known regarding patterns in the BAP. We compared autism parents with control parents with no family history of ASD using 2 well-validated face-processing tasks. Results indicated increased activation in the autism parents to faces in the amygdala (AMY) and the fusiform gyrus (FG), 2 core face-processing regions. Exploratory analyses revealed hyper-activation of lateral occipital cortex (LOC) bilaterally in autism parents with aloof personality ("BAP+"). Findings suggest that abnormalities of the AMY and FG are related to underlying genetic liability for ASD, whereas abnormalities in the LOC and right FG are more specific to behavioral features of the BAP. Results extend our knowledge of neural circuitry underlying abnormal face processing beyond those previously reported in ASD to individuals with shared genetic liability for autism and a subset of genetically related individuals with the BAP.

Predicting the diagnosis of autism spectrum disorder using gene pathway analysis

Autism spectrum disorder (ASD) depends on a clinical interview with no biomarkers to aid diagnosis. The current investigation interrogated single-nucleotide polymorphisms (SNPs) of individuals with ASD from the Autism Genetic Resource Exchange (AGRE) database. SNPs were mapped to Kyoto Encyclopedia of Genes and Genomes (KEGG)-derived pathways to identify affected cellular processes and develop a diagnostic test. This test was then applied to two independent samples from the Simons Foundation Autism Research Initiative (SFARI) and Wellcome Trust 1958 normal birth cohort (WTBC) for validation. Using AGRE SNP data from a Central European (CEU) cohort, we created a genetic diagnostic classifier consisting of 237 SNPs in 146 genes that correctly predicted ASD diagnosis in 85.6% of CEU cases. This classifier also predicted 84.3% of cases in an ethnically related Tuscan cohort; however, prediction was less accurate (56.4%) in a genetically dissimilar Han Chinese cohort (HAN). Eight SNPs in three genes (KCNMB4, GNAO1, GRM5) had the largest effect in the classifier with some acting as vulnerability SNPs, whereas others were protective. Prediction accuracy diminished as the number of SNPs analyzed in the model was decreased. Our diagnostic classifier correctly predicted ASD diagnosis with an accuracy of 71.7% in CEU individuals from the SFARI (ASD) and WTBC (controls) validation data sets. In conclusion, we have developed an accurate diagnostic test for a genetically homogeneous group to aid in early detection of ASD. While SNPs differ across ethnic groups, our pathway approach identified cellular processes common to ASD across ethnicities. Our results have wide implications for detection, intervention and prevention of ASD.

Patterns of skill attainment and loss in young children with autism

The purpose of this study was to extend the literature on the ontogeny of autism spectrum disorder (ASD) by examining early attainment and loss of specific sociocommunicative skills in children with autism (AUT; n = 125), pervasive developmental disorder not otherwise specified (PDD-NOS; n = 42), nonspectrum developmental delays (n = 46), and typical development (n = 31). The ages of skill attainment and loss were obtained from a caregiver interview. The findings indicated that children with AUT, PDD-NOS, and developmental delays diverged from typically developing children in attainment of sociocommunicative skills early in the first year of life. Loss of at least one skill was reported in a majority of children with AUT and PDD-NOS. Significant delays in attainment of skills were also reported in children who lost skills. The wide variation in skill attainment and loss reported across children indicates that symptom onset and regression may be best represented continuously, with at least some early delay and loss present for a great majority of children with ASD.

The autism puzzle: challenging a mechanistic model on conceptual and historical grounds

Although clinicians and researchers working in the field of autism are generally not concerned with philosophical categories of kinds, a model for understanding the nature of autism is important for guiding research and clinical practice. Contemporary research in the field of autism is guided by the depiction of autism as a scientific object that can be identified with systematic neuroscientific investigation. This image of autism is compatible with a permissive account of natural kinds: the mechanistic property cluster (MPC) account of natural kinds, recently proposed as the model for understanding psychiatric disorders. Despite the heterogeneity, multicausality and fuzzy boundaries that complicate autism research, a permissive account of natural kinds (MPC kinds) provides prescriptive guidance for the investigation of objective causal mechanisms that should inform nosologists in their attempt to carve autism's boundaries at its natural joints. However, this essay will argue that a mechanistic model of autism is limited since it disregards the way in which autism relates to ideas about what kind of behavior is abnormal. As historical studies and definitions of autism show, normative issues concerning disability, impairment and societal needs have been and still are inextricably linked to how we recognize and understand autism. The current search for autism's unity in neurobiological mechanisms ignores the values, social norms and various perspectives on mental pathology that play a significant role in 'the thing called autism'. Autism research needs to engage with these issues in order to achieve more success in the effort to become clinically valuable.

Pivotal response treatment for infants at-risk for autism spectrum disorders: a pilot study

Presently there is limited research to suggest efficacious interventions for infants at-risk for autism. Pivotal response treatment (PRT) has empirical support for use with preschool children with autism, but there are no reports in the literature utilizing this approach with infants. In the current study, a developmental adaptation of PRT was piloted via a brief parent training model with three infants at-risk for autism. Utilizing a multiple baseline design, the data suggest that the introduction of PRT resulted in increases in the infants' frequency of functional communication and parents' fidelity of implementation of PRT procedures. Results provide preliminary support for the feasibility and utility of PRT for very young children at-risk for autism.

Autism as early neurodevelopmental disorder: evidence for an sAPPα-mediated anabolic pathway

Autism is a neurodevelopmental disorder marked by social skills and communication deficits and interfering repetitive behavior. Intellectual disability often accompanies autism. In addition to behavioral deficits, autism is characterized by neuropathology and brain overgrowth. Increased intracranial volume often accompanies this brain growth. We have found that the Alzheimer's disease (AD) associated amyloid-β precursor protein (APP), especially its neuroprotective processing product, secreted APP α, is elevated in persons with autism. This has led to the "anabolic hypothesis" of autism etiology, in which neuronal overgrowth in the brain results in interneuronal misconnections that may underlie multiple autism symptoms. We review the contribution of research in brain volume and of APP to the anabolic hypothesis, and relate APP to other proteins and pathways that have already been directly associated with autism, such as fragile X mental retardation protein, Ras small GTPase/extracellular signal-regulated kinase, and phosphoinositide 3 kinase/protein kinase B/mammalian target of rapamycin. We also present additional evidence of magnetic resonance imaging intracranial measurements in favor of the anabolic hypothesis. Finally, since it appears that APP's involvement in autism is part of a multi-partner network, we extend this concept into the inherently interactive realm of epigenetics. We speculate that the underlying molecular abnormalities that influence APP's contribution to autism are epigenetic markers overlaid onto potentially vulnerable gene sequences due to environmental influence.

Child development and structural variation in the human genome

Structural variation of the human genome sequence is the insertion, deletion, or rearrangement of stretches of DNA sequence sized from around 1,000 to millions of base pairs. Over the past few years, structural variation has been shown to be far more common in human genomes than previously thought. Very little is currently known about the effects of structural variation on normal child development, but such effects could be of considerable significance. This review provides an overview of the phenomenon of structural variation in the human genome sequence, describing the novel genomics technologies that are revolutionizing the way structural variation is studied and giving examples of genomic structural variations that affect child development.

The Development of Referential Communication and Autism Symptomatology in High-Risk Infants

Non-verbal referential communication is impaired in children with Autism Spectrum Disorders (ASD). However, the development of difficulties with referential communication in the younger siblings of children with ASD (High-Risk Siblings)-and the degree to which early referential communication predicts later autism symptomatology-is not clear. We modeled the early developmental trajectories of three types of referential communication: responding to joint attention (RJA), initiating joint attention (IJA), and initiating behavioral requests (IBR) across 8, 10, 12, 15, and18 months of age in High-Risk Siblings (n = 40) and the infant siblings of children without ASD (Low-Risk Siblings; n = 21). Hierarchical Linear Modeling indicated that High-Risk Siblings exhibited lower levels of baseline RJA and IJA and a lower rate of linear change in IBR than Low-Risk Siblings. When the 10 High-Risk Siblings who received an ASD diagnosis were excluded from analyses, group differences in the development of referential communication remained significant only for RJA. Baseline levels of IJA were associated with later ASD symptomatology among High-Risk Siblings, suggesting that individual differences in referential communication development at 8 months may index early manifestations of ASD.

ADHD and autism: differential diagnosis or overlapping traits? A selective review

According to DSM-IV TR and ICD-10, a diagnosis of autism or Asperger Syndrome precludes a diagnosis of attention-deficit/hyperactivity disorder (ADHD). However, despite the different conceptualization, population-based twin studies reported symptom overlap, and a recent epidemiologically based study reported a high rate of ADHD in autism and autism spectrum disorders (ASD). In the planned revision of the DSM-IV TR, dsm5 (www.dsm5.org), the diagnoses of autistic disorder and ADHD will not be mutually exclusive any longer. This provides the basis of more differentiated studies on overlap and distinction between both disorders. This review presents data on comorbidity rates and symptom overlap and discusses common and disorder-specific risk factors, including recent proteomic studies. Neuropsychological findings in the areas of attention, reward processing, and social cognition are then compared between both disorders, as these cognitive abilities show overlapping as well as specific impairment for one of both disorders. In addition, selective brain imaging findings are reported. Therapeutic options are summarized, and new approaches are discussed. The review concludes with a prospectus on open questions for research and clinical practice.

Optogenetic insights into social behavior function

Cognitive and social deficits lie at the core of many neuropsychiatric diseases and are among the many behavioral symptoms not amenable to pharmacological intervention. Despite significant advances in identifying genes potentially involved in the pathogenesis of complex psychiatric conditions such as autism and schizophrenia, knowledge of the physiological functions that are affected (and are therefore potential targets for clinical intervention) is scarce. In psychiatric disorders with a strong genetic component, animal models have provided important links between disease-related genes and behavioral impairment. Social dysfunction, for instance, is commonly observed in transgenic rodent disease models. However, the causal relationships between the behavioral and physiological abnormalities in these models are not well-understood. Optogenetic techniques have evolved to provide a wide range of experimental paradigms in which neural circuit activity can be perturbed with high spatial and temporal precision, enabling causal investigation of the function of defined physiological events in neuronal subgroups. With optogenetics, researchers have begun to elucidate the basic neural mechanisms of social behaviors and of disease-relevant social and cognitive dysfunction. The synthesis of optogenetic technology with genetic animal models will allow forward- and reverse-engineering approaches to investigating the neural correlates of psychiatric disease. This review outlines the neural systems known to be involved in social behavior, illustrates how optogenetic technology has been applied to analyze this circuitry, and imagines how it might be further developed in future studies to elucidate these complex circuits both from a basic science perspective and in the context of psychiatric disease.

Sex differences in repetitive stereotyped behaviors in autism: implications for genetic liability

The implications of the well known sex differences in the prevalence of autism spectrum disorder (ASD) are not well understood. The aim of this paper was to investigate whether these differences might be associated with differences in genetic liability. Individuals with ASD (970 families, 2,028 individuals) were recruited as part of the Autism Genome Project (AGP). The families were differentiated into families containing a female (either female-female or male-female) and those with only males. If the sex with the lower prevalence is associated with a greater genetic liability necessary to cross sex-specific thresholds, the males from female containing families should be more severely affected than males from male only families. Affected subjects from the different types of families with ASD were sampled and compared on the social reciprocity and repetitive behavior scores from the Autism Diagnostic Interview-Revised (ADI-R). In general, females had lower repetitive behavior scores than males. More importantly, males from female containing families had higher repetitive behavior scores than males from male-male families. No such differences were apparent on the social reciprocity scores. These results support the hypothesis of a multiple threshold model of genetic liability of ASD with females having a higher liability for affectation status, at least on the repetitive behavior dimension of the disorder. These data also support the dissociation of the different phenotypic dimensions of ASD in terms of its genetic architecture. The implications of these results for linkage and association studies are discussed.

AutismKB: an evidence-based knowledgebase of autism genetics

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder with a prevalence of 0.9–2.6%. Twin studies showed a heritability of 38–90%, indicating strong genetic contributions. Yet it is unclear how many genes have been associated with ASD and how strong the evidence is. A comprehensive review and analysis of literature and data may bring a clearer big picture of autism genetics. We show that as many as 2193 genes, 2806 SNPs/VNTRs, 4544 copy number variations (CNVs) and 158 linkage regions have been associated with ASD by GWAS, genome-wide CNV studies, linkage analyses, low-scale genetic association studies, expression profiling and other low-scale experimental studies. To evaluate the evidence, we collected metadata about each study including clinical and demographic features, experimental design and statistical significance, and used a scoring and ranking approach to select a core data set of 434 high-confidence genes. The genes mapped to pathways including neuroactive ligand–receptor interaction, synapse transmission and axon guidance. To better understand the genes we parsed over 30 databases to retrieve extensive data about expression patterns, protein interactions, animal models and pharmacogenetics. We constructed a MySQL-based online database and share it with the broader autism research community at http://autismkb.cbi.pku.edu.cn, supporting sophisticated browsing and searching functionalities.

The potential role of probiotics in the management of childhood autism spectrum disorders

Gastrointestinal (GI) dysfunction has been reported in a substantial number of children with autism spectrum disorders (ASD). Activation of the mucosal immune response and the presence of abnormal gut microbiota are repeatedly observed in these children. In children with ASD, the presence of GI dysfunction is often associated with increased irritability, tantrums, aggressive behaviour, and sleep disturbances. Moreover, modulating gut bacteria with short-term antibiotic treatment can lead to temporary improvement in behavioral symptoms in some individuals with ASD. Probiotics can influence microbiota composition and intestinal barrier function and alter mucosal immune responses. The administration of probiotic bacteria to address changes in the microbiota might, therefore, be a useful novel therapeutic tool with which to restore normal gut microbiota, reduce inflammation, restore epithelial barrier function, and potentially ameliorate behavioural symptoms associated with some children with ASD. In this review of the literature, support emerges for the clinical testing of probiotics in ASD, especially in the context of addressing GI symptoms.

Recurrence risk for autism spectrum disorders: a Baby Siblings Research Consortium study

OBJECTIVE

The recurrence risk of autism spectrum disorders (ASD) is estimated to be between 3% and 10%, but previous research was limited by small sample sizes and biases related to ascertainment, reporting, and stoppage factors. This study used prospective methods to obtain an updated estimate of sibling recurrence risk for ASD.

METHODS

A prospective longitudinal study of infants at risk for ASD was conducted by a multisite international network, the Baby Siblings Research Consortium. Infants (n = 664) with an older biological sibling with ASD were followed from early in life to 36 months, when they were classified as having or not having ASD. An ASD classification required surpassing the cutoff of the Autism Diagnostic Observation Schedule and receiving a clinical diagnosis from an expert clinician.

RESULTS

A total of 18.7% of the infants developed ASD. Infant gender and the presence of >1 older affected sibling were significant predictors of ASD outcome, and there was an almost threefold increase in risk for male subjects and an additional twofold increase in risk if there was >1 older affected sibling. The age of the infant at study enrollment, the gender and functioning level of the infant's older sibling, and other demographic factors did not predict ASD outcome.

CONCLUSIONS

The sibling recurrence rate of ASD is higher than suggested by previous estimates. The size of the current sample and prospective nature of data collection minimized many limitations of previous studies of sibling recurrence. Clinical implications, including genetic counseling, are discussed.

Sowing the seeds of the autism field: Leo Kanner (1943)

More than 65 years after Leo Kanner published his seminal article, research on autism continues to be an area of increasing interest. Although much progress has been made, this field is still in its infancy, and many avenues of research are just beginning to be pursued. Despite the time that has passed, the syndrome Kanner identified and his comments about the children he observed continue to have meaning today, and although some of his suggestions about the etiology and presentation of autism were grounded in the thinking of his day, many of his observations were quite prescient. In this paper we explore Kanner's contributions to the field of autism, discuss how the field has changed, and suggest ways that research on autism spectrum disorders can continue to move forward.

A pilot study of abnormal growth in autism spectrum disorders and other childhood psychiatric disorders

The aims of the current study were to examine whether early growth abnormalities are (a) comparable in autism spectrum disorders (ASD) and other childhood psychiatric disorders, and (b) specific to the brain or generalized to the whole body. Head circumference, height, and weight were measured during the first 19 months of life in 129 children with ASD and 59 children with non-ASD psychiatric disorders. Both groups showed comparable abnormal patterns of growth compared to population norms, especially regarding height and head circumference in relation to height. Thus abnormal growth appears to be related to psychiatric disorders in general and is mainly expressed as an accelerated growth of height not matched by an increase in weight or head circumference.

A proposed mechanism for autism: an aberrant neuroimmune response manifested as a psychiatric disorder

Autism, an incurable neurodevelopmental brain disorder, is a complex psychopathology in which the affected individual cannot effectively self-regulate their sensory inputs toward coherent and focused motor outputs. There have been many hypotheses as to the etiology of autism - genetics, neurotransmitter imbalances, early childhood immunizations, xenobiotic and teratogenic agents, and maternal infection; the disorder can perhaps be studied best under the field of "Psychoneuroimmunology", which analyzes systemic and psychopathologies from an integrated approach through the combined effects of the nervous, immune, and endocrine systems. Using principles of psychoneuroimmunology along with previously established but yet un-linked scientific principles and observations, this paper proposes a neuroimmune-based mechanistic hypothesis for the etiology of autism that connects elevated levels of maternal pro-inflammatory cytokines to autistic symptoms in her offspring through a logical sequence of events. While both researchers and clinicians often note correlations between pro-inflammatory cytokine levels and autistic symptoms in affected individuals, no specific mechanism has been documented that logically and directly connects the two. I propose that pro-inflammatory cytokines arising from maternal inflammation, infection, and, possibly, autoimmunity, pass through the placenta; enter the fetal circulation; cross the fetal blood-brain barrier (BBB); and cause aberrant neuronal growth and plasticity within the fetal brain via a "cytokine-storm". Microglia and astrocyte stimulation lead to a positive-feedback loop that also facilitates the development of a chronic inflammatory environment within the fetus, pre-disposing it to lifelong comorbid psychiatric and systemic pathologies. Such a mechanism could account for many of the observed symptoms and behaviors of autistic individuals such as hyper-sensitivity to environmental stimuli, object fixation, echolalia, repetitive physical behaviors, chronic enterocolitis, autoimmune disease, and, at the extreme, savantism. The thiazolidinedione pioglitazone (and possibly rosiglitazone), a non-steroidal anti-inflammatory drug (NSAID), which is commonly used to lower blood glucose levels and associated inflammatory markers in patients with diabetes, and histamine receptor blockers, as well as monitoring and limiting sucrose-containing foods, might prove to be effective preventative therapies for the development of autism in the fetus for pregnant women displaying either a cytokine-induced depression or other elevated systemic inflammatory state conditions.

Genome-wide association scan of korean autism spectrum disorders with language delay: a preliminary study

OBJECTIVE

Communication problems are a prevalent symptom of autism spectrum disorders (ASDs), which have a genetic background. Although several genome-wide studies on ASD have suggested a number of candidate genes, few studies have reported the association or linkage of specific endophenotypes to ASDs.

METHODS

Forty-two Korean ASD patients who showed a language delay were enrolled in this study with their parents. We performed a genome-wide scan by using the Affymetrix SNP Array 5.0 platform to identify candidate genes responsible for language delay in ASDs.

RESULTS

We detected candidate single-nucleotide polymorphisms (SNPs) in chromosome 11, rs11212733 (p-value=9.76×10(-6)) and rs7125479 (p-value=1.48×10(-4)), as a marker of language delay in ASD using the transmission disequilibrium test and multifactor dimensionality reduction test.

CONCLUSION

Although our results suggest that several SNPs are associated with language delay in ASD, rs11212733 we were not able to observe any significant results after correction of multiple comparisons. This may imply that more samples may be required to identify genes associated with language delay in ASD.

Using perceptual signatures to define and dissociate condition-specific neural etiology: autism and fragile X syndrome as model conditions

The functional link between genetic alteration and behavioral end-state is rarely straightforward and never linear. Cases where neurodevelopmental conditions defined by a distinct genetic etiology share behavioral phenotypes are exemplary, as is the case for autism and Fragile X Syndrome (FXS). In this paper and its companion paper, we propose a method for assessing the functional link between genotype and neural alteration across these target conditions by comparing their perceptual signatures. In the present paper, we discuss how such signatures can be used to (1) define and differentiate various aspects of neural functioning in autism and FXS, and subsequently, (2) to infer candidate causal (genetic) mechanisms based on such signatures (see companion paper, this issue).

Characterization of the deleted in autism 1 protein family: implications for studying cognitive disorders

Autism spectrum disorders (ASDs) are a group of commonly occurring, highly-heritable developmental disabilities. Human genes c3orf58 or Deleted In Autism-1 (DIA1) and cXorf36 or Deleted in Autism-1 Related (DIA1R) are implicated in ASD and mental retardation. Both gene products encode signal peptides for targeting to the secretory pathway. As evolutionary medicine has emerged as a key tool for understanding increasing numbers of human diseases, we have used an evolutionary approach to study DIA1 and DIA1R. We found DIA1 conserved from cnidarians to humans, indicating DIA1 evolution coincided with the development of the first primitive synapses. Nematodes lack a DIA1 homologue, indicating Caenorhabditis elegans is not suitable for studying all aspects of ASD etiology, while zebrafish encode two DIA1 paralogues. By contrast to DIA1, DIA1R was found exclusively in vertebrates, with an origin coinciding with the whole-genome duplication events occurring early in the vertebrate lineage, and the evolution of the more complex vertebrate nervous system. Strikingly, DIA1R was present in schooling fish but absent in fish that have adopted a more solitary lifestyle. An additional DIA1-related gene we named DIA1-Like (DIA1L), lacks a signal peptide and is restricted to the genomes of the echinoderm Strongylocentrotus purpuratus and cephalochordate Branchiostoma floridae. Evidence for remarkable DIA1L gene expansion was found in B. floridae. Amino acid alignments of DIA1 family gene products revealed a potential Golgi-retention motif and a number of conserved motifs with unknown function. Furthermore, a glycine and three cysteine residues were absolutely conserved in all DIA1-family proteins, indicating a critical role in protein structure and/or function. We have therefore identified a new metazoan protein family, the DIA1-family, and understanding the biological roles of DIA1-family members will have implications for our understanding of autism and mental retardation.

DIA1R is an X-linked gene related to Deleted In Autism-1

Background

Autism spectrum disorders (ASDs) are frequently occurring disorders diagnosed by deficits in three core functional areas: social skills, communication, and behaviours and/or interests. Mental retardation frequently accompanies the most severe forms of ASDs, while overall ASDs are more commonly diagnosed in males. Most ASDs have a genetic origin and one gene recently implicated in the etiology of autism is the Deleted-In-Autism-1 (DIA1) gene.

Methodology/Principal Findings

Using a bioinformatics-based approach, we have identified a human gene closely related to DIA1, we term DIA1R (DIA1-Related). While DIA1 is autosomal (chromosome 3, position 3q24), DIA1R localizes to the X chromosome at position Xp11.3 and is known to escape X-inactivation. The gene products are of similar size, with DIA1 encoding 430, and DIA1R 433, residues. At the amino acid level, DIA1 and DIA1R are 62% similar overall (28% identical), and both encode signal peptides for targeting to the secretory pathway. Both genes are ubiquitously expressed, including in fetal and adult brain tissue.

Conclusions/Significance

Examination of published literature revealed point mutations in DIA1R are associated with X-linked mental retardation (XLMR) and DIA1R deletion is associated with syndromes with ASD-like traits and/or XLMR. Together, these results support a model where the DIA1 and DIA1R gene products regulate molecular traffic through the cellular secretory pathway or affect the function of secreted factors, and functional deficits cause disorders with ASD-like symptoms and/or mental retardation.

The neural circuitry of autism

Autism is a complex neurodevelopmental disorder, characterized by deficits in social emotional, and language domains, as well as repetitive restrictive behaviors. The vast heterogeneity of the clinical and behavioral symptoms has made it rather difficult to delineate the neural circuitry affiliated with these domains of dysfunction. The current review aims at broadly outlining the latest research into the neurobiology and neural circuitry underlying the core domains of deficits in autism. We further discuss new avenues of research that can further our understanding of the dimensions of this complex disorder.

The Genetics of Autism

This chapter is written to make the fast-paced, expanding field of the genetics of autism accessible to those practitioners who help children with autism. New genetic knowledge and technology have quickly developed over the past 30 years, particularly within the past decade, and have made many optimistic about our ability to explain autism. Among these advances include the sequencing of the human genome (Lander et al., 2001) and the identification of common genetic variants via the HapMap project (International HapMap Consortium, 2005), and the development of cost-efficient genotyping and analysis technologies (Losh, Sullivan, Trembath, & Piven, 2008). Improvement in technology has led to improved visualization of chromosomal abnormality down to the molecular level. The four most common syndromes associated with autism include fragile X syndrome, tuberous sclerosis, 15q duplications, and untreated phenylketonuria (PKU; Costa e Silva, 2008). FXS and 15q duplications are discussed within the context of cytogenetics. TSC is illustrated within the description of linkage analysis.

Homologs of genes expressed in Caenorhabditis elegans GABAergic neurons are also found in the developing mouse forebrain

BACKGROUND

In an effort to identify genes that specify the mammalian forebrain, we used a comparative approach to identify mouse homologs of transcription factors expressed in developing Caenorhabditis elegans GABAergic neurons. A cell-specific microarray profiling study revealed a set of transcription factors that are highly expressed in embryonic C. elegans GABAergic neurons.

RESULTS

Bioinformatic analyses identified mouse protein homologs of these selected transcripts and their expression pattern was mapped in the mouse embryonic forebrain by in situ hybridization. A review of human homologs indicates several of these genes are potential candidates in neurodevelopmental disorders.

CONCLUSIONS

Our comparative approach has revealed several novel candidates that may serve as future targets for studies of mammalian forebrain development.

Maternal immune activation and autism spectrum disorder: interleukin-6 signaling as a key mechanistic pathway

An emerging area of research in autism spectrum disorder (ASD) is the role of prenatal exposure to inflammatory mediators during critical developmental periods. Epidemiological data has highlighted this relationship showing significant correlations between prenatal exposure to pathogens, including influenza, and the occurrence of ASD. Although there has not been a definitive molecular mechanism established, researchers have begun to investigate this relationship as animal models of maternal infection have support- ed epidemiological findings. Several groups utilizing these animal models have found that activation of the maternal immune system, termed maternal immune activation (MIA), and more specifically the exposure of the developing fetus to maternal cytokines precipitate the neurological, immunological and behavioral abnormalities observed in the offspring of these animals. These abnormalities have correlated with clinical findings of immune dysregulation, neurological and behavioral abnormalities in some autistic individuals. Additionally, researchers have observed genetic variations in these models in genes which regulate neurological and immunological development, similar to what is observed clinically in ASD. Altogether, the role of MIA and cytokine dysregulation, as a key mediator in the neuropathological, behavioral and possibly genetic irregularities observed clinically in autism are important factors that warrant further investigation.

Frontal cortex functioning in the infant broader autism phenotype

Atypical attention has been proposed as a marker of the broader autism phenotype. In the present study we investigated this and the related process of inhibitory control at the youngest possible age through the study of infant siblings of children with an autism spectrum disorder (Sibs-ASD). Both attention and inhibition have been related to the frontal cortex of the brain. Nine- to ten-month-old Sibs-ASD and low-risk control infants completed the Freeze-Frame task, in which infants are encouraged to inhibit looks to peripherally presented distractors whilst looking at a central animation. The attractiveness of the central stimulus is varied in order to investigate the selectivity of infants' responses. In line with previous studies, it was found that a subset of Sibs-ASD infants had difficulty disengaging attention from a central stimulus in order to orient to a peripheral stimulus. The Sibs-ASD group also showed less Selective Inhibition than controls. However, Sibs-ASD infants did demonstrate Selective Inhibitory Learning. These results provide preliminary evidence for atypical frontal cortex functioning in the infant broader autism phenotype.

Further evidence for the role of MET in autism susceptibility

MET receptor tyrosine kinase (MET)-mediated signaling has been implicated in multiple aspects of neocortical and cerebellar neuronal growth and maturation. A promoter functional SNP (rs1858830) that disrupts the transcription of MET has been reported to be strongly associated with autism spectrum disorders (ASD) in the Caucasian population. Here, we performed a trio association study of MET with ASD in Japanese subjects (n=126 trios). Based on the HapMap data on the Japanese population, 15 SNPs were chosen for the association study. One SNP located in intron 1, rs38841, showed a nominal association with autism (p=0.044; OR=1.61) when analyzed using the transmission disequilibrium test. To the best of our knowledge, this is the first replication study of the association of MET with autism, in any non-Caucasian population. Association of rs38841 with autism was further confirmed in 252 Caucasian trios from AGRE (p=0.0006). An interesting observation is that all three SNPs of MET (rs1858830, rs38845 and rs38841) shown to be associated with autism in three independent studies including the present one, are located towards the 5'end of the gene at a span of 9.4 kb. Our results provide further evidence for a possible role of MET in the pathogenesis of ASD.

Defining the broader, medium and narrow autism phenotype among parents using the Autism Spectrum Quotient (AQ)

Background

The Autism Spectrum Quotient (AQ) is a self-report questionnaire for quantifying autistic traits. This study tests whether the AQ can differentiate between parents of children with an autism spectrum condition (ASC) and control parents. In this paper, the use of the AQ to define the broader, medium and narrow autism phenotypes (BAP, MAP, NAP) is reported, and the proportion of parents with each phenotype is compared between the two groups.

Methods

A sample of 571 fathers and 1429 mothers of children with an ASC completed the AQ, along with 349 fathers and 658 mothers of developing typically children.

Results

Both mothers and fathers of the diagnosed children scored higher than the control parents on total AQ score and on four out of five of the subscales. Additionally, there were more parents of diagnosed children with a BAP, MAP or NAP.

Conclusions

The AQ provides an efficient method for quantifying where an individual lies along the dimension of autistic traits, and extends the notion of a broader phenotype among first-degree relatives of those with ASC. The AQ is likely to have many applications, including population and clinical screening, and stratification in genetic studies.

Combined effect of maternal serotonin transporter genotype and prenatal stress in modulating offspring social interaction in mice

Several studies suggest that prenatal stress is a possible risk factor in the development of autism spectrum disorders. However, many children exposed to stress prenatally are born healthy and develop typically, suggesting that other factors must contribute to autism. Genes that contribute to stress reactivity may, therefore, exacerbate prenatal stress-mediated behavioral changes in the adult offspring. One candidate gene linked to increased stress reactivity encodes the serotonin transporter. Specifically, an insertion/deletion (long/short allele) polymorphism upstream of the serotonin transporter gene correlates with differential expression and function of the serotonin transporter and a heightened response to stressors. Heterozygous serotonin transporter knockout mice show reductions in serotonin transporter expression similar to the human short polymorphism. In this study, the role of prenatal stress and maternal serotonin transporter genotype were assessed in mice to determine whether their combined effect produces reductions in social behavior in the adult offspring. Pregnant serotonin transporter heterozygous knockout and wild-type dams were placed in either a control condition or subjected to chronic variable stress. The adult offspring were subsequently assessed for social interaction and anxiety using a three-chamber social approach task, ultrasonic vocalization detection, elevated-plus maze and an open field task. Results indicated that prenatal stress and reduced serotonin transporter expression of the dam may have the combined effect of producing changes in social interaction and social interest in the offspring consistent with those observed in autism spectrum disorder. This data indicates a possible combined effect of maternal serotonin transporter genotype and prenatal stress contributing to the production of autistic-like behaviors in offspring.

Social deficits, stereotypy and early emergence of repetitive behavior in the C58/J inbred mouse strain

Mouse lines with behavioral phenotypes relevant to symptoms in neurodevelopmental disorders may provide models to test hypotheses about disease etiology and to evaluate potential treatments. The present studies were designed to confirm and expand earlier work on the intriguing behavioral profile of the C58/J inbred strain, including low social approach and aberrant repetitive movements. Additional tests were selected to reflect aspects of autism, a severe neurodevelopmental disorder characterized by emergence of symptoms early in life, higher prevalence in males, social deficits and abnormal repetitive behavior. Mice from the C57BL/6J inbred strain, which has a similar genetic lineage and physical appearance to C58/J, served as a comparison group. Our results revealed that C58/J mice display elevated activity levels by postnatal day 6, which persist into adulthood. Despite normal olfactory ability, young adult male C58/J mice showed deficits in social approach in the three-chambered choice assay and failed to demonstrate social transmission of food preference. In contrast, female C58/J mice performed similarly to female C57BL/6J mice in both social tests. C58/J mice of both sexes demonstrated abnormal repetitive behaviors, displaying excessive jumping and back flipping in both social and non-social situations. These stereotypies were clearly evident in C58/J pups by postnatal days 20-21, and were also observed in C58/J dams during a test for maternal behavior. Overall, the strain profile for C58/J, including spontaneously developing motor stereotypies emerging early in the developmental trajectory, and social deficits primarily in males, models multiple components of the autism phenotype.