The genetics of autism

Chemical Modulators for Targeting Autism Spectrum Disorders: From Bench to Clinic

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by diverse behavioral symptoms such as repetitive behaviors, social deficits, anxiety, hyperactivity, and irritability. Despite their increasing incidence, the specific pathological mechanisms of ASD are still unknown, and the degree and types of symptoms that vary from patient to patient make it difficult to develop drugs that target the core symptoms of ASD. Although various atypical antipsychotics and antidepressants have been applied to regulate ASD symptoms, these drugs can only alleviate the symptoms and do not target the major causes. Therefore, development of novel drugs targeting factors directly related to the onset of ASD is required. Among the various factors related to the onset of ASD, several chemical modulators to treat ASD, focused on serotonin (5-hydroxytryptamine, 5-HT) and glutamate receptors, microbial metabolites, and inflammatory cytokines, are explored in this study. In particular, we focus on the chemical drugs that have improved various aspects of ASD symptoms in animal models and in clinical trials for various ages of patients with ASD.

Maternal stress and perinatal features in autism and attention deficit/hyperactivity disorder

BACKGROUND

We investigated the shared and non-shared perinatal risk factors for autism spectrum disorders (ASD) and attention deficit/hyperactivity disorder (ADHD) in a clinical sample. Additionally, we compared these groups regarding pre/postpartum maternal stress and the duration of breastfeeding.

METHODS

Children aged 3-18 years old with ASD (n = 100) were compared with age- and gender-matched children with ADHD (n = 100) and with age- and gender-matched healthy controls (n = 80).

RESULTS

Prematurity of the neonate and maternal stress/depressive mood in pregnancy were common risk factors shared by ASD and ADHD. Postpartum maternal depressive mood may be more specific to ASD, while shorter duration of breastfeeding may be related to ADHD.

CONCLUSIONS

ASD and ADHD may have some perinatal features in common. Identification of perinatal factors for ASD and ADHD carries clinical implications in terms of primary prevention.

A cross-cultural comparison of autistic traits in the UK, India and Malaysia

The disorder of autism is widely recognised throughout the world. However, the diagnostic criteria and theories of autism are based on research predominantly conducted in Western cultures. Here we compare the expression of autistic traits in a sample of neurotypical individuals from one Western culture (UK) and two Eastern cultures (India and Malaysia), using the Autism-spectrum Quotient (AQ) in order to identify possible cultural differences in the expression of autistic traits. Behaviours associated with autistic traits were reported to a greater extent in the Eastern cultures than the Western culture. Males scored higher than females and science students scored higher than non-science students in each culture. Indian students scored higher than both other groups on the Imagination sub-scale, Malaysian students scored higher than both other groups on the Attention Switching sub-scale. The underlying factor structures of the AQ for each population were derived and discussed.

Genetic variants of neurotransmitter-related genes and miRNAs in Egyptian autistic patients

Autism is a neurodevelopmental disorder with indisputable evidence for a genetic component. This work studied the association of autism with genetic variations in neurotransmitter-related genes, including MAOA uVNTR, MAOB rs1799836, and DRD2 TaqI A in 53 autistic patients and 30 healthy individuals. The study also analyzed sequence variations of miR-431 and miR-21. MAOA uVNTR was genotyped by PCR, MAOB and DRD2 polymorphisms were analyzed by PCR-based RFLP, and miR-431 and miR-21 were sequenced. Low expressing allele of MAOA uVNTR was frequently higher in female patients compared to that in controls (OR = 2.25). MAOB G allele frequency was more significantly increased in autistic patients than in controls (P < 0.001 for both males and females). DRD2 A1+ genotype increased autism risk (OR = 5.1). Severity of autism tends to be slightly affected by MAOA/B genotype. Plasma MAOB activity was significantly reduced in G than in A allele carrying males. There was no significant difference in patients and maternal plasma MAOA/B activity compared to controls. Neither mutations nor SNPs in miR-431 and miR-21 were found among studied patients. This study threw light on some neurotransmitter-related genes suggesting their potential role in Autism pathogenesis that warrants further studies and much consideration.

Prenatal, perinatal and neonatal risk factors for autism - study in Poland

The results of conducted research studies suggest that heredity and early fetal and neonatal development play a causal role in autism. The objective was to determine a relationship between pre-, peri-, and neonatal factors and autism. The relationship between genders and individual risk factors for autism was also examined. A case-control study was conducted among 288 children (96 cases with childhood or atypical autism and 192 controls individually matched to cases by the year of birth, sex, and general practitioners). Data on autism diagnosis and other medical conditions were acquired from physicians. All other information on potential autism risk factors were collected from mothers. Autism risk was significantly higher when mothers were taking medications (OR=2.72, 95%CI: 1.47-5.04) and smoked during pregnancy (OR=3.32, 95%CI: 1.12-9.82). It was also significantly associated with neonatal dyspnea (OR=3.20, 95%CI: 1.29-8.01) and congenital anomalies (OR=7.17, 95%CI: 2.23-23.1). In gender analysis only congenital anomalies were significantly associated with autism for girls but all of mentioned factors stayed independent risk factors for boys.

Association between MTHFR gene polymorphisms and the risk of autism spectrum disorders: a meta-analysis

Methylenetetrahydrofolate reductase (MTHFR) is essential for DNA biosynthesis and the epigenetic process of DNA methylation, and its gene polymorphisms have been implicated as risk factors for birth defects, neurological disorders, and cancers. However, reports on the association of MTHFR polymorphisms with autism spectrum disorders (ASD) are inconclusive. Therefore, we investigated the relationship of the MTHFR polymorphisms (C677T and A1298C) and the risk of ASD by meta-analysis. Up to December 2012, eight case-control studies involving 1672 patients with ASD and 6760 controls were included for meta-analysis. The results showed that the C677T polymorphism was associated with significantly increased ASD risk in all the comparison models [T vs. C allele (frequency of allele): odds ratio (OR) = 1.42, 95% confidence interval (CI): 1.09-1.85; CT vs. CC (heterozygote): OR = 1.48, 95% CI: 1.09-2.00; TT vs. CC (homozygote): OR = 1.86, 95% CI: 1.08-3.20; CT+TT vs. CC (dominant model): OR = 1.56, 95% CI: 1.12-2.18; and TT vs. CC+CT (recessive model): OR = 1.51, 95% CI: 1.02-2.22], whereas the A1298C polymorphism was found to be significantly associated with reduced ASD risk but only in a recessive model (CC vs. AA+AC: OR = 0.73, 95% CI: 0.56-0.97). In addition, we stratified the patient population based on whether they were from a country with food fortification of folic acid or not. The meta-analysis showed that the C677T polymorphism was found to be associated with ASD only in children from countries without food fortification. Our study indicated that the MTHFR C677T polymorphism contributes to increased ASD risk, and periconceptional folic acid may reduce ASD risk in those with MTHFR 677C>T polymorphism.

Haplotype structure enables prioritization of common markers and candidate genes in autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental condition that results in behavioral, social and communication impairments. ASD has a substantial genetic component, with 88-95% trait concordance among monozygotic twins. Efforts to elucidate the causes of ASD have uncovered hundreds of susceptibility loci and candidate genes. However, owing to its polygenic nature and clinical heterogeneity, only a few of these markers represent clear targets for further analyses. In the present study, we used the linkage structure associated with published genetic markers of ASD to simultaneously improve candidate gene detection while providing a means of prioritizing markers of common genetic variation in ASD. We first mined the literature for linkage and association studies of single-nucleotide polymorphisms, copy-number variations and multi-allelic markers in Autism Genetic Resource Exchange (AGRE) families. From markers that reached genome-wide significance, we calculated male-specific genetic distances, in light of the observed strong male bias in ASD. Four of 67 autism-implicated regions, 3p26.1, 3p26.3, 3q25-27 and 5p15, were enriched with differentially expressed genes in blood and brain from individuals with ASD. Of 30 genes differentially expressed across multiple expression data sets, 21 were within 10 cM of an autism-implicated locus. Among them, CNTN4, CADPS2, SUMF1, SLC9A9, NTRK3 have been previously implicated in autism, whereas others have been implicated in neurological disorders comorbid with ASD. This work leverages the rich multimodal genomic information collected on AGRE families to present an efficient integrative strategy for prioritizing autism candidates and improving our understanding of the relationships among the vast collection of past genetic studies.

Catechol-O-methyltransferase Val158Met polymorphism and risk of autism spectrum disorders

Objective

Autism spectrum disorders (ASD) are a family of childhood-onset neurodevelopmental disorders with complex genetic mechanisms underlying their aetiology. The aim of this case–control study was to evaluate the effect of the catechol-O-methyltransferase ( COMT) gene Val158Met polymorphism on ASD risk in a Chinese Han population.

Methods

The COMT gene Val158Met polymorphism was detected by polymerase chain reaction–restriction fragment length polymorphism in children (≤18 years old) with ASD and healthy control subjects.

Results

The frequency of the Val158/Val158 genotype in children with ASD (22/186; 11.8%) was significantly lower than in controls (38/186; 20.4%). When stratifying by select-item scores on the Autism Diagnostic Interview-Revised protocol, it was found that children with ‘current overactivity’ and ‘ever overactivity’ had a significantly lower frequency of the Val158/Val158 genotype than those without. There were no significant associations between the COMT gene Val158Met polymorphism and ASD subtypes.

Conclusions

The COMT gene Val158Met polymorphism may be a biomarker for phenotypic variation in ASD, but these preliminary findings remain tentative, pending replication in larger, independent samples.

Methylenetetrahydrofolate reductase polymorphisms C677T and risk of autism in the Chinese Han population

Causes of autism are still unknown. Some studies have shown that autism might be associated with metabolic abnormalities in the folate/homocysteine pathway, which is involved in DNA methylation, thus altering gene expression. The association between the methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphisms and the risk of autism is still controversial and ambiguous. The purpose of this study was to examine the effect of the MTHFR C677T polymorphism on the autism risk in the Chinese Han population. A population-based case-control study was conducted in 186 children with autism and 186 controls. The MTHFR C677T polymorphisms were determined by using a polymerase chain reaction-restriction fragment length polymorphism assay. The frequency of genotype MTHFR 677TT in children with autism (16.1%) was significantly higher (odds ratio [OR]=2.04; 95% confidence interval [CI]=1.07, 3.89; p=0.03] than those in controls (8.6%). When stratifying by select-item scores on the Autism Diagnostic Interview-Revised, it was found that children with current overactivity had a significantly higher frequency of the MTHFR 677TT genotype (OR=2.77, 95% CI=1.17, 6.60; p=0.02) than those without. This study suggested that MTHFR C677T is a risk factor of autism in Chinese Han children.

The role of prenatal, obstetric and neonatal factors in the development of autism

We conducted a linked database cohort study of infants born between 1990 and 2002 in Nova Scotia, Canada. Diagnoses of autism were identified from administrative databases with relevant diagnostic information to 2005. A factor representing genetic susceptibility was defined as having an affected sibling or a mother with a history of a psychiatric or neurologic condition. Among 129,733 children, there were 924 children with an autism diagnosis. The results suggest that among those with low genetic susceptibility, some maternal and obstetric factors may have an independent role in autism etiology whereas among genetically susceptible children, these factors appear to play a lesser role. The role of pre-pregnancy obesity and excessive weight gain during pregnancy on autism risk require further investigation.

The contribution of muscular and auditory pathologies to the symptomatology of autism

Most research concerning the pathology of autism is focused on the search for central abnormalities that account for the production of symptoms. We, however, instead of looking at muscular and auditory features as merely associated manifestations, propose that they are somatic contributors by which some of the main clinical features of autism might be explained. Evidence suggests that muscles affect emotional experience. We think certain muscular dysfunctioning can impair communication and social interaction, and create stereotypic behavior, giving rise to the diagnostic features of autism. Furthermore, because speech is synchronized with facial movements and voice is controlled mainly through auditory feedback, a distortion of auditory feedback could disrupt voice, which in turn might cause parallel abnormal facial muscle functioning.

Autism-associated gene expression in peripheral leucocytes commonly observed between subjects with autism and healthy women having autistic children

Autism spectrum disorder (ASD) is a severe neuropsychiatric disorder which has complex pathobiology with profound influences of genetic factors in its development. Although the numerous autism susceptible genes were identified, the etiology of autism is not fully explained. Using DNA microarray, we examined gene expression profiling in peripheral blood from 21 individuals in each of the four groups; young adults with ASD, age- and gender-matched healthy subjects (ASD control), healthy mothers having children with ASD (asdMO), and asdMO control. There was no blood relationship between ASD and asdMO. Comparing the ASD group with control, 19 genes were found to be significantly changed. These genes were mainly involved in cell morphology, cellular assembly and organization, and nerve system development and function. In addition, the asdMO group possessed a unique gene expression signature shown as significant alterations of protein synthesis despite of their nonautistic diagnostic status. Moreover, an ASD-associated gene expression signature was commonly observed in both individuals with ASD and asdMO. This unique gene expression profiling detected in peripheral leukocytes from affected subjects with ASD and unaffected mothers having ASD children suggest that a genetic predisposition to ASD may be detectable even in peripheral cells. Altered expression of several autism candidate genes such as FMR-1 and MECP2, could be detected in leukocytes. Taken together, these findings suggest that the ASD-associated genes identified in leukocytes are informative to explore the genetic, epigenetic, and environmental background of ASD and might become potential tools to assess the crucial factors related to the clinical onset of the disorder.

Intestinal disaccharidase activity in patients with autism: effect of age, gender, and intestinal inflammation

Intestinal disaccharidase activities were measured in 199 individuals with autism to determine the frequency of enzyme deficiency. All patients had duodenal biopsies that were evaluated morphologically and assayed for lactase, sucrase, and maltase activity. Frequency of lactase deficiency was 58% in autistic children ≤ 5 years old and 65% in older patients. As would be expected, patients with autism at age 5 > years demonstrated significant decline in lactase activity (24%, p = .02) in comparison with ≤ 5 years old autistic patients. Boys ≤ 5 years old with autism had 1.7 fold lower lactase activity than girls with autism (p = .02). Only 6% of autistic patients had intestinal inflammation. Lactase deficiency not associated with intestinal inflammation or injury is common in autistic children and may contribute to abdominal discomfort, pain and observed aberrant behavior. Most autistic children with lactose intolerance are not identified by clinical history.

Parents' criticisms and attributions about their adult children with high functioning autism or schizophrenia

The current study examined the criticism component of expressed emotion (EE) and attributions in parents of adults diagnosed with schizophrenia/schizoaffective disorder (S/SA) or high functioning autism/Asperger's. Consistent with study hypotheses, parents of adults diagnosed with autism/Asperger's disorder exhibited lower levels of high EE-criticism than parents of adults diagnosed with S/SA. Moderate trends suggested that parents of adults diagnosed with autism/Asperger's disorder tended to make less blameworthy attributions towards patients than did parents of adults diagnosed with S/SA. A content analysis of parents' causal attributions was also conducted.The most common cause cited by both groups of parents was biological factors, suggesting that parents may be becoming more aware of scientific findings implicating biological factors, in conjunction with psychosocial factors, as a major cause of mental illness.

Association and gene-gene interaction of SLC6A4 and ITGB3 in autism

Autism is a heritable neurodevelopmental disorder with substantial genetic heterogeneity. Studies point to possible links between autism and two serotonin related genes: SLC6A4 and ITGB3 with a sex-specific genetic effect and interaction between the genes. Despite positive findings, inconsistent results have complicated interpretation. This study seeks to validate and clarify previous findings in an independent dataset taking into account sex, family-history (FH) and gene-gene effects. Family-based association analysis was performed within each gene. Gene-gene interactions were tested using extended multifactor dimensionality reduction (EMDR) and MDR-phenomics (MDR-P) using sex of affecteds and FH as covariates. No significant associations with individual SNPs were found in the datasets stratified by sex, but associations did emerge when we stratified by family history. While not significant in the overall dataset, nominally significant association was identified at RS2066713 (P = 0.006) within SLC6A4 in family-history negative (FH-) families, at RS2066713 (P = 0.038) in family-history positive (FH+) families but with the opposite risk allele as in the FH- families. For ITGB3, nominally significant association was identified at RS3809865 overall (P = 0.040) and within FH+ families (P = 0.031). However, none of the associations survived the multiple testing correction. MDR-P confirmed gene-gene effects using sex of affecteds (P = 0.023) and family history (P = 0.014, survived the multiple testing corrections) as covariates. Our results indicate the extensive heterogeneity within these two genes among families. The potential interaction between SLC6A4 and ITGB3 may be clarified using family history as an indicator of genetic architecture, illustrating the importance of covariates as markers of heterogeneity in genetic analyses.

Family aggregation of mental disorders in the nationwide Danish three generation study

OBJECTIVE

The study of familial aggregation of major mental disorders in a national population.

METHOD

Within a Danish register-based cohort study, aggregation of mental disorders was analysed in all case-probands with first psychiatric contact before the age of 19 years in the time period between 1 April 1969 and 29 June 2004 followed up until the age of 35 years, their first-degree relatives, and a matched group of control-probands including their first-degree relatives.

RESULTS

Hazard rate ratios were significantly elevated for cases as compared to controls for all diagnoses among probands, parents, and siblings. Among children of the probands, these ratios were significantly elevated for neurotic (anxiety) disorders, mental retardation, developmental disorders, behavioural and emotional disorders of childhood and adolescence, and miscellaneous disorders. Family aggregation of any diagnosis was significantly higher in probands with substance use disorder, schizophrenia, affective disorders, neurotic (anxiety) disorders, and miscellaneous disorders. There was specificity of familial transmission for affective and neurotic (anxiety) disorders.

CONCLUSION

This large nationwide study found some differential patterns of familial aggregation of major mental disorders.

Birth defects in children with autism spectrum disorders: a population-based, nested case-control study

The causes of autism spectrum disorders (ASDs) are unknown, although genetic and environmental influences have been implicated. Previous studies have suggested an association with birth defects, but most investigators have not addressed associations with specific diagnostic categories of ASD. In this study, the authors investigated the associations between birth defects and autism, Asperger syndrome, and pervasive developmental disorder not otherwise specified. Using Western Australian population-based linked data, the authors compared all children with ASD born in Western Australia during 1980-1995 (n = 465) with their siblings (n = 481) and population controls (n = 1,313) in a nested case-control study. The prevalence of birth defects was significantly higher in ASD cases than in population controls; this difference remained significant after adjustment for confounding factors. Odds ratios for birth defects were similar for autism (odds ratio (OR) = 2.0, 95% confidence interval (CI): 1.3, 3.0) and pervasive developmental disorder not otherwise specified (OR = 2.2, 95% CI: 1.1, 4.3) but not for Asperger syndrome (OR = 0.5, 95% CI: 0.1, 1.9). Birth defects in case siblings were not significantly different from those in cases and population controls. The association between birth defects and ASD may be due to underlying genetic and/or environmental factors common to both ASD and birth defects, or birth defects may predispose a child to ASD.

Family-based association study between NOS-I and -IIA polymorphisms and autism spectrum disorders in Korean trios

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder with a strong genetic component and environmental risk factors. Nitric oxide (NO), which is produced by nitric oxide synthase (NOS), may play a role in the development of ASD. We genotyped nine single nucleotide polymorphisms (SNPs) in the NOS-I gene and nine SNPs in the NOS-IIA gene and carried out the transmission disequilibrium test (TDT) and haplotype analysis in 151 Korean ASD trios. We found preferential transmission of the A allele of rs8068149 (P = 0.039) and G allele of rs1060826 (P = 0.035) of NOS-IIA in ASD and the haplotype analysis revealed that the two haplotypes had significant associations (P = 0.014 and 0.031, respectively). The behavioral subdomain score of failure to use nonverbal behaviors to regulate social interaction in Autism Diagnostic Interview-Revised (ADI-R) was significantly higher in subjects with the GG or AG allele in rs1060826 of NOS-IIA compared to those who had the AA allele (P = 0.027). These results provide significant but weak evidence for an association between NOS-IIA and ASD in the Korean population.

Mutations in the calcium-related gene IL1RAPL1 are associated with autism

In a systematic sequencing screen of synaptic genes on the X chromosome, we have identified an autistic female without mental retardation (MR) who carries a de novo frameshift Ile367SerfsX6 mutation in Interleukin-1 Receptor Accessory Protein-Like 1 (IL1RAPL1), a gene implicated in calcium-regulated vesicle release and dendrite differentiation. We showed that the function of the resulting truncated IL1RAPL1 protein is severely altered in hippocampal neurons, by measuring its effect on neurite outgrowth activity. We also sequenced the coding region of the close related member IL1RAPL2 and of NCS-1/FREQ, which physically interacts with IL1RAPL1, in a cohort of subjects with autism. The screening failed to identify non-synonymous variant in IL1RAPL2, whereas a rare missense (R102Q) in NCS-1/FREQ was identified in one autistic patient. Furthermore, we identified by comparative genomic hybridization a large intragenic deletion of exons 3-7 of IL1RAPL1 in three brothers with autism and/or MR. This deletion causes a frameshift and the introduction of a premature stop codon, Ala28GlufsX15, at the very beginning of the protein. All together, our results indicate that mutations in IL1RAPL1 cause a spectrum of neurological impairments ranging from MR to high functioning autism.

Genetic influences on the broad spectrum of autism: study of proband-ascertained twins

An investigation of genetic structures underlying autistic traits was performed with samples from twins for which at least one proband had been ascertained as having autism spectrum disorders (ASDs) in our catchment area. In order to adjust for recent concepts of autism, we employed criteria for the broad spectrum of disease and the childhood autism rating scale (CARS) for quantitative assessment. The CARS test was performed on 45 twin pairs (19 monozygotic, 26 dizygotic) detected with a regional routine screening system. The obtained CARS scores were subjected to structural equation modeling (SEM), incorporating sex differences for each causal influence ascertainment correction, using the Mx software. A best fitting model of causal influences on autistic traits measured continuously, incorporating additive genetic (A) and non-shared environmental influences (E), was generated. With this AE model, the estimated heritability was 0.73 for males and 0.87 for females, based on the continuous CARS scores. There was no evidence for the existence of sex-specific genetic influences. Autistic traits were highly heritable in twins with even broad spectrum of autism, corresponding to the results of early studies based on classical autism. Additive genetic factors were more influential in females than males.

Psychiatric genetics: progress amid controversy

Several psychiatric disorders--such as bipolar disorder, schizophrenia and autism--are highly heritable, yet identifying their genetic basis has been challenging, with most discoveries failing to be replicated. However, inroads have been made by the incorporation of intermediate traits (endophenotypes) and of environmental factors into genetic analyses, and through the identification of rare inherited variants and novel structural mutations. Current efforts aim to increase sample sizes by gathering larger samples for case-control studies or through meta-analyses of such studies. More attention on unique families, rare variants, and on incorporating environment and the emerging knowledge of biological function and pathways into genetic analysis is warranted.

Parental psychiatric disorders associated with autism spectrum disorders in the offspring

OBJECTIVE

Autism is a developmental disorder defined by impaired social interaction, communication, and behavior. Causes and correlates of autism are largely unknown, but elevated frequencies of psychiatric disorders and distinct personality traits have been reported among the family members of individuals with autism. Linkage of data from Swedish registries was used to investigate whether hospitalization for psychiatric conditions was higher among parents of children with autism compared with control subjects.

METHODS

Data sources included the Swedish Medical Birth Register (child's birth), the Swedish Multi-Generation Register (linking parents to children), and Swedish Hospital Discharge Register (hospitalization records). Children born between 1977 and 2003 who had a hospitalization record indicating autism before 10 years of age (n = 1227) were matched with 30,693 control subjects from the Swedish Medical Birth Register by gender, year of birth, and hospital. Parent diagnoses were based on an inpatient hospital diagnostic evaluation and included schizophrenia, other nonaffective psychoses, affective disorders, neurotic and personality disorders and other nonpsychotic disorders, alcohol and drug addiction and abuse, and autism. Odds ratios and 95% confidence intervals were estimated by using conditional logistic regression, adjusted for child's age, gender, hospital of birth, parents' age, country of birth and socioeconomic status, and diagnosis of a mental disorder in the other parent.

RESULTS

Parents of children with autism were more likely to have been hospitalized for a mental disorder than parents of control subjects. Schizophrenia was more common among case mothers and fathers compared with respective control parents. Depression and personality disorders were more common among case mothers but not fathers. CONCLUSIONS; This large population study supports the potential for familial aggregation of psychiatric conditions that may provide leads for future investigations of heritable forms of autism.

Technetium-99m HMPAO brain SPECT in autistic children and their families

The purpose of the study was to investigate perfusion patterns in autistic children (AC) and their families. Ten AC (9 boys, 1 girl; mean age: 6.9+/-1.7 years) with autistic disorder defined by DSM-III-R criteria, five age-matched children (3 boys, 2 girls) as a control group, and the immediate family members of eight AC (8 mothers, 8 fathers, 7 siblings; mean ages: 39+/-4 years, 36+/-5 years and 13+/-5 years, respectively) were included in the study. Age- and sex-matched control groups for both the parents and the siblings were also included in the study. Brain perfusion images were obtained 1 h after the intravenous injection of an adjusted dose of Tc-99m HMPAO to children and the adults. Visual and semiquantitative evaluations were performed. Hypoperfusion was seen in the right posterior parietal cortex in three AC, in bilateral parietal cortex in one AC, bilateral frontal cortex in two AC, left parietal and temporal cortex in one AC, and right parietal and temporal cortex in one AC. Asymmetric perfusion was observed in the caudate nucleus in four AC. In semiquantitative analyses, statistically significant hypoperfusion was found in the right inferior and superior frontal, left superior frontal, right parietal, right mesial temporal and right caudate nucleus. In parents of AC, significant hypoperfusion was noted in the right parietal and bilateral inferior frontal cortex. In siblings of AC, perfusion in the right frontal cortex, right nucleus caudate and left parietal cortex was significantly decreased. This preliminary study suggests the existence of regional brain perfusion alterations in frontal, temporal, and parietal cortex and in caudate nucleus in AC and in their first-degree family members.

Identification and evaluation of children with autism spectrum disorders

Autism spectrum disorders are not rare; many primary care pediatricians care for several children with autism spectrum disorders. Pediatricians play an important role in early recognition of autism spectrum disorders, because they usually are the first point of contact for parents. Parents are now much more aware of the early signs of autism spectrum disorders because of frequent coverage in the media; if their child demonstrates any of the published signs, they will most likely raise their concerns to their child's pediatrician. It is important that pediatricians be able to recognize the signs and symptoms of autism spectrum disorders and have a strategy for assessing them systematically. Pediatricians also must be aware of local resources that can assist in making a definitive diagnosis of, and in managing, autism spectrum disorders. The pediatrician must be familiar with developmental, educational, and community resources as well as medical subspecialty clinics. This clinical report is 1 of 2 documents that replace the original American Academy of Pediatrics policy statement and technical report published in 2001. This report addresses background information, including definition, history, epidemiology, diagnostic criteria, early signs, neuropathologic aspects, and etiologic possibilities in autism spectrum disorders. In addition, this report provides an algorithm to help the pediatrician develop a strategy for early identification of children with autism spectrum disorders. The accompanying clinical report addresses the management of children with autism spectrum disorders and follows this report on page 1162 [available at www.pediatrics.org/cgi/content/full/120/5/1162]. Both clinical reports are complemented by the toolkit titled "Autism: Caring for Children With Autism Spectrum Disorders: A Resource Toolkit for Clinicians," which contains screening and surveillance tools, practical forms, tables, and parent handouts to assist the pediatrician in the identification, evaluation, and management of autism spectrum disorders in children.

Impairment of quality of life in parents of children and adolescents with pervasive developmental disorder

BACKGROUND

Little is known about the Quality of Life (QOL) in parents of children with developmental diseases as compared to other severe neurological or psychiatric disorders. Aims of the present study were: to evaluate QOL in parents of children affected by Pervasive Development Disorder (PDDs), Cerebral Palsy (CP) or Mental Retardation (MR) as compared to a control group (CG); to evaluate QOL of parents of patients with different types of PDDs, namely Autistic Disorder (AD), High Function Autism/Asperger Syndromes (HFA/AS) and Pervasive Developmental Disorder Not Otherwise Specified (PPD-NOS); and to compare the level of impairment in QOL of mothers and fathers within PDDs, CP, MR groups and between AD, HFA/AS, PDD-NOS sub-groups.

METHODS

The sample consisted of 212 parents (115 mothers and 97 fathers) of 135 children or adolescents affected by PDDs, MR or CP. An additional sample of 77 parents (42 mothers and 35 fathers) of 48 healthy children was also included and used as a control group. QOL was assessed by the WHOQOL-BREF questionnaire.

RESULTS

Compared with parents of healthy children, parents in the PDDs group reported impairment in physical activity (p = 0.0001) and social relationships (p = 0.0001) and worse overall perception of their QOL (p = 0.0001) and health (p = 0.005). Scores in the physical (p = 0.0001), psychological (p = 0.0001) and social relationships domains (p = 0.0001) and in the physical (p = 0.0001) and social relationships (p = 0.0001) domains were lower compared to the MR group CP group respectively. Little differences were observed between MR, CP and control groups. The level of impairment of physical (p = 0.001) and psychological (p = 0.03) well-being were higher in mothers than in fathers in the PDDs and CP groups respectively; in the other groups, and across all the other domains of QQL impairment was similar. There were no statistically significant differences in the scores between the AD, HFA/AS and PDD-NOS sub-groups, but parents in the HFA/AS sub-group seemed to display a lower QOL compared to the AD sub-group.

CONCLUSION

Parents of children with PDDs seem to display a higher burden, probably for a combination of environmental and genetic factors. Within this group of parents also those of HFA or AS people have higher stress. These finding must be taken into account in policy making to provide better and more specific supports and interventions for this group of diseases.

A case of pervasive developmental disorder with chromosomal translocation 1-4

We describe a 5-year-old girl with pervasive developmental disorder associated to chromosome 1-4 translocation, an association that has not been described in specialized literature until this moment.

Placental trophoblast inclusions in autism spectrum disorder

BACKGROUND

Microscopic examination of placental tissue may provide a route to assessing risk and understanding underlying biology of autism.

METHODS

Occurrence of a distinctive microscopic placental morphological abnormality, the trophoblast inclusion, was assessed using archived placental tissue. The rate of occurrence of trophoblast inclusion-positive slides observed for 13 individuals with autism spectrum disorder (ASD) was compared to the rate in an anonymous consecutive birth cohort.

RESULTS

The occurrence of inclusion positive slides was significantly greater in the ASD group compared to the control group (6/27 slides, 22.2% vs. 12/154, 7.8%; Fisher Exact Test, two-tailed p = .033; relative risk 2.85). The proportion of positive cases was also greater in the ASD group (5/13 cases, 38.5% vs. 8/61, 13.1%; Fisher Exact, two-tailed p = .044; relative risk 2.93). Behavioral severity scores did not differ across groups of inclusion positive (N = 4) and negative (N = 8) ASD individuals.

CONCLUSIONS

Although probably not functionally detrimental or causative, the greater occurrence of placental trophoblast inclusions observed in ASD individuals may reflect altered early developmental processes. Further research is required to replicate the basic finding, to understand the basis for the trophoblastic abnormality, and to determine the utility of the measure in early detection of ASD.

Histological and magnetic resonance imaging assessment of cortical layering and thickness in autism spectrum disorders

BACKGROUND

Qualitative reports of the cerebral cortex in a small number of autism spectrum disorder (ASD) cases have suggested an increase in thickness and disruptions in migration and lamination patterns.

METHODS

We examined postmortem ASD individuals and age-matched controls using magnetic resonance imaging (MRI) to evaluate total cortical thickness, and histological samples to evaluate the pattern of cortical layering.

RESULTS

Overall, thickness measures from ASD subjects were equivalent to control cases. Individual regions showed marginal but nonsignificant thickness differences in the temporal lobes. Cortical thickness values in ASD subjects decreased significantly with age. Quantitative examination of proportional layer thickness in histological sections indicated that the pattern of cortical layering was largely undisturbed, while qualitative examination of these same samples revealed evidence of cell clustering and supernumerary cells in layer I and the subplate. These features were not severe and were never found in a majority of cases.

CONCLUSIONS

These findings support limited disturbances in cortical cell patterning, but do not indicate a major deficit in the orderly migration of cortical neuroblasts during development, or their subsequent aggregation into the laminar pattern found in typically developing individuals.

A review of gene linkage, association and expression studies in autism and an assessment of convergent evidence

Autism is a neurodevelopmental disorder with high heritability and a likely complex genetic architecture. Much genetic evidence has accumulated in the last 20 years but no gene has been unequivocally identified as containing risk variants for autism. In this article we review the past and present literature on neuro-pathological, genetic linkage, genetic association, and gene expression studies in this disorder. We sought convergent evidence to support particular genes or chromosomal regions that might be likely to contain risk DNA variants. The convergent evidence from these studies supports the current hypotheses that there are multiple genetic loci predisposing to autism, and that genes involved in neurodevelopment are especially important for future genetic studies. Convergent evidence suggests the chromosome regions 7q21.2-q36.2, 16p12.1-p13.3, 6q14.3-q23.2, 2q24.1-q33.1, 17q11.1-q21.2, 1q21-q44 and 3q21.3-q29, are likely to contain risk genes for autism. Taken together with results from neuro-pathological studies, genes involved in brain development located at the above regions should be prioritized for future genetic research.

Secretin receptor-deficient mice exhibit impaired synaptic plasticity and social behavior

Secretin is a peptide hormone released from the duodenum to stimulate the secretion of digestive juice by the pancreas. Secretin also functions as a neuropeptide hormone in the brain, and exogenous administration has been reported to alleviate symptoms in some patients with autism. We have generated secretin receptor-deficient mice to explore the relationship between secretin signaling in the brain and behavioral phenotypes. Secretin receptor-deficient mice are overtly normal and fertile; however, synaptic plasticity in the hippocampus is impaired and there are slightly fewer dendritic spines in the CA1 hippocampal pyramidal cells. Furthermore, secretin receptor-deficient mice show abnormal social and cognitive behaviors. These findings suggest that the secretin receptor system has an important role in the central nervous system relating to social behavior.

A Case–Control Study of Personality Style and Psychopathology in Parents of Subjects with Autism

To probe the specificity of traits that might be conceptualised as the broader phenotype of autism, parents of subjects with autism from simplex and multiplex families as well as parents of subjects with obsessive-compulsive disorders (OCD), early onset schizophrenia (EOS) and mental retardation (MR) were assessed using the Personality Style and Disorder Inventory and the Symptom Checklist-90-Revised. Autism parents' scores were increased on several subscales (e.g. reserved/schizoid, depression) compared to parents of subjects with OCD, EOS and normative data, but not in comparison to MR parents. Results provide some support for the specificity of the broader phenotype of autism. The burden of raising severely disabled children could not be ruled out as a factor influencing parts of this phenotype.

The yield of subtelomeric FISH analysis in the evaluation of autistic spectrum disorders

To assess the frequency of cryptic subtelomeric rearrangements in children and adolescents with autism spectrum disorders, blood samples were studied using a complete set of subtelomeric FISH probes in 72 children with autism spectrum disorders. All children had normal high resolution karyotype, DNA fra-X analysis, brain MRI, metabolic work-up, and physical/neurological examination. Subtelomeric analysis did not detect abnormalities in any of the subjects, suggesting the uselessness of such investigations in individuals with primary autism spectrum disorders.

Autism spectrum disorders associated with X chromosome markers in French-Canadian males

It is now well established that genetic factors play an important role in the pathogenesis of autism disorder and converging lines of evidence suggest the implication of the X chromosome. Using a sample of subjects diagnosed with autism spectrum disorders, exclusively composed of males from French-Canadian (FC) origin, we tested markers covering the entire X chromosome using a family-based association study. Our initial analysis revealed the presence of association at two loci: DXS6789 (P=0.026) and DXS8043 (P=0.0101). In a second step, we added support to the association at DXS8043 using additional markers, additional subjects and a haplotype-based analysis (best obtained P-value=0.00001). These results provide support for the existence of a locus on the X chromosome that predisposes the FC to autism spectrum disorders.

A heterogeneity-based genome search meta-analysis for autism-spectrum disorders

Autism and autism-spectrum disorders exhibit high heritability, although specific susceptibility genes still remain largely elusive. We performed a heterogeneity-based genome search meta-analysis (HEGESMA) of nine genome scans on autism or autism-spectrum disorders. Each genome scan was separated in 30 cM bins and the maximum linkage statistic from each bin was ranked. Significance for each bin's average rank and for between-scan heterogeneity (dis-similarity in the average ranks) was obtained through Monte Carlo tests. For autism, data from 771 affected sibpairs were synthesized across six separate genome scans. Region 7q22-q32 reached genome-wide significance both in weighted and unweighted analyses, with evidence for significantly low between-scan heterogeneity. The flanking chromosomal region 7q32-qter reached the less stringent threshold of suggestive significance, with no evidence for low between-scan heterogeneity. For autism-spectrum disorders (634 affected sibpairs from five separate scans), no chromosomal region reached genome-wide significance. However, suggestive significance was reached for the chromosomal regions 17p11.2-q12 and 10p12-q11.1 in weighted analyses. There was evidence for significantly high between-scan heterogeneity for the former region. The meta-analysis suggests that the 7q22-q32 region should be further scrutinized for autism susceptibility genes, while autism-spectrum disorders seem to have quite diverse linkage signals across scans, possibly suggesting genetic heterogeneity across subsyndromes and subpopulations.

A genome-wide search for alleles and haplotypes associated with autism and related pervasive developmental disorders on the Faroe Islands

The involvement of genetic factors in the etiology of autism has been clearly established. We undertook a genome-wide search for regions containing susceptibility genes for autism in 12 subjects with childhood autism and related pervasive developmental disorders (PDDs) and 44 controls from the relatively isolated population of the Faroe Islands. In total, 601 microsatellite markers distributed throughout the human genome with an average distance of 5.80 cM were genotyped, including 502 markers in the initial scan. The Faroese population structure and genetic relatedness of cases and controls were also evaluated. Based on a combined approach, including an assumption-free test as implemented in CLUMP, Fisher's exact test for specific alleles and haplotypes, and IBD(0) probability calculations, we found association between autism and microsatellite markers in regions on 2q, 3p, 6q, 15q, 16p, and 18q. The most significant finding was on 3p25.3 (P(T1)=0.00003 and P(T4)=0.00007), which was also supported by other genetic studies. Furthermore, no evidence of population substructure was found, and a higher degree of relatedness among cases could not be detected, decreasing the risk of inflated P-values. Our data suggest that markers in these regions are in linkage disequilibrium with genes involved in the etiology of autism, and we hypothesize susceptibility genes for autism and related PDDs to be localized within these regions.

Autism: a window onto the development of the social and the analytic brain

Although the neurobiological understanding of autism has been increasing exponentially, the diagnosis of autism spectrum conditions still rests entirely on behavioral criteria. Autism is therefore most productively approached using a combination of biological and psychological theory. The triad of behavioral abnormalities in social function, communication, and restricted and repetitive behaviors and interests can be explained psychologically by an impaired capacity for empathizing, or modeling the mental states governing the behavior of people, along with a superior capacity for systemizing, or inferring the rules governing the behavior of objects. This empathizing-systemizing theory explains other psychological models such as impairments of executive function or central coherence, and may have a neurobiological basis in abnormally low activity of brain regions subserving social cognition, along with abnormally high activity of regions subserving lower-level, perceptual processing--a pattern that may result from a skewed balance of local versus long-range functional connectivity.

Glial fibrillary acidic protein is elevated in superior frontal, parietal and cerebellar cortices of autistic subjects

Autism is a debilitating neurodevelopmental disorder of early childhood with both genetic and environmental origins. Immune system dysregulation has been hypothesized to be involved in this disorder. We quantified levels of glial fibrillary acidic protein (GFAP) and ss-actin in three areas of the brain, namely, area 9, area 40 and cerebellum, in age matched autistic and control postmortem specimen using SDS-PAGE and western blotting techniques. Significant elevations in levels of GFAP were observed in all three brain areas in autism. This report confirms a recent report showing microglial and astroglial activation in autism. Increased GFAP levels in autistic brains signify gliosis, reactive injury, and perturbed neuronal migration processes.

The human secretin gene in children with autistic spectrum disorder: screening for polymorphisms and mutations

We screened 29 children with autism for mutation in the human secretin gene using single-strand conformation polymorphism. No mutation was detected in exon 2, 3, or 4. Polymerase chain reaction and DNA sequence of 5' variable number of tandem repeats showed two polymorphisms with deletion or duplication of a repeat unit that failed to show any gene expression with transient transfection assay. We did not find evidence of a relationship between human secretin gene mutation and autism.

Concurrent Validity of Social Subtype and IQ after Early Intensive Behavioral Intervention in Children with Autism: A Preliminary Investigation

Three subtypes of autism based on social style have been proposed by Wing: active-but-odd, passive, or aloof. Previous research has shown evidence of an association between IQ and Wing subtype in untreated children and adults. Because IQ changes can accompany behavioral treatment, but often only for a subset of children, social subtype may be related to treatment responsiveness. We administered a social subtyping measure, the Wing Subgroups Questionnaire (WSQ), at various points in treatment to younger children than previously studied with autism in early, intensive behavioral intervention (EIBI). Thirty-seven children in EIBI (aged 39-71 months, amount of EIBI 0-44 months) were assessed to determine whether Wing's three proposed subtypes were found in this sample and whether subtypes were associated with current IQ and change in IQ after a period of EIBI. Results confirmed that all three subtypes were present and correlated with IQ after a period of intervention, as well as with change in IQ. Participants classified as aloof had significantly lower IQ scores and changes in IQ after EIBI than other children. Future studies should extend these findings by examining whether social subtype at pretreatment predicts EIBI outcome.

Risk factors for autism: perinatal factors, parental psychiatric history, and socioeconomic status

Research suggests that heredity and early fetal development play a causal role in autism. This case-control study explored the association between perinatal factors, parental psychiatric history, socioeconomic status, and risk of autism. The study was nested within a cohort of all children born in Denmark after 1972 and at risk of being diagnosed with autism until December 1999. Prospectively recorded data were obtained from nationwide registries in Denmark. Cases totaled 698 children with a diagnosis of autism; each case was individually matched by gender, birth year, and age to 25 controls. Analyses by conditional logistic regression produced risk ratios and 95% confidence intervals. Adjusted analyses showed that the risk of autism was associated with breech presentation (risk ratio (RR) = 1.63, 95% confidence interval (CI): 1.18, 2.26), low Apgar score at 5 minutes (RR = 1.89, 95% CI: 1.10, 3.27), gestational age at birth <35 weeks (RR = 2.45, 95% CI: 1.55, 3.86), and parental psychiatric history (schizophrenia-like psychosis: RR = 3.44, 95% CI: 1.48, 7.95; affective disorder: RR = 2.91, 95% CI: 1.65, 5.14). Analyses showed no statistically significant association between risk of autism and weight for gestational age, parity, number of antenatal visits, parental age, or socioeconomic status. Results suggest that prenatal environmental factors and parental psychopathology are associated with the risk of autism. These factors seem to act independently.

Serotonin transporter intron 2 polymorphism associated with rigid-compulsive behaviors in Dutch individuals with pervasive developmental disorder

Two putatively functional polymorphisms of the serotonin transporter gene (HTT, SLC6A4) were examined for associations with risk for pervasive developmental disorders (PDDs) and specific autism phenotypes. Dutch patients diagnosed with PDD (N = 125, age range 5-20 years, DSM-IV-TR based criteria, ADI-R and ADOS behavioral assessments) and their parents (N = 230) were genotyped for promoter ins/del (5-HTTLPR) and intron 2 variable number of tandem repeats (VNTR) alleles. Using the transmission disequilibrium test (TDT), no disorder-specific preferential transmission of promoter (long and short) or intron 2 (10- and 12-repeat) alleles was observed. However, multivariate analysis of continuous autism-related behavioral measures revealed that subjects with intron 2 12/12 genotype were significantly more impaired in the rigid-compulsive domain (P = 0.008). Quantitative TDT (QTDT) analysis also showed significant association of the intron 2 VNTR 12-repeat allele with rigid-compulsive behavior (P = 0.015). These results suggest that intron 2 VNTR alleles or nearby polymorphisms in linkage disequilibrium may play a role in specific aspects of the behavioral phenotype of autism.

A mixed epigenetic/genetic model for oligogenic inheritance of autism with a limited role for UBE3A

The genetic contribution to autism is often attributed to the combined effects of many loci (ten or more). This conclusion is based in part on the much lower concordance for dizygotic (DZ) than for monozygotic (MZ) twins, and is consistent with the failure to find strong evidence for linkage in genome-wide studies. We propose that the twin data are compatible with oligogenic inheritance combined with a major, genetic or epigenetic, de novo component to the etiology. Based on evidence that maternal but not paternal duplications of chromosome 15q cause autism, we attempted to test the hypothesis that autism involves oligogenic inheritance (two or more loci) and that the Angelman gene (UBE3A), which encodes the E6-AP ubiquitin ligase, is one of the contributing genes. A search for epigenetic abnormalities led to the discovery of a tissue-specific differentially methylated region (DMR) downstream of the UBE3A coding exons, but the region was not abnormal in autism lymphoblasts or brain samples. Based on evidence for allele sharing in 15q among sib-pairs, abnormal DNA methylation at the 5'-CpG island of UBE3A in one of 17 autism brains, and decreased E6-AP protein in some autism brains, we propose a mixed epigenetic and genetic model for autism with both de novo and inherited contributions. The role of UBE3A may be quantitatively modest, but interacting proteins such as those ubiquitinated by UBE3A may be candidates for a larger role in an oligogenic model. A mixed epigenetic and genetic and mixed de novo and inherited (MEGDI) model could be relevant to other "complex disease traits".

Epigenetics and human disease

Epigenetics is comprised of the stable and heritable (or potentially heritable) changes in gene expression that do not entail a change in DNA sequence. The role of epigenetics in the etiology of human disease is increasingly recognized with the most obvious evidence found for genes subject to genomic imprinting. Mutations and epimutations in imprinted genes can give rise to genetic and epigenetic phenotypes, respectively; uniparental disomy and imprinting defects represent epigenetic disease phenotypes. There are also genetic disorders that affect chromatin structure and remodeling. These disorders can affect chromatin in trans or in cis, as well as expression of both imprinted and nonimprinted genes. Data from Angelman and Beckwith-Wiedemann syndromes and other disorders indicate that a monogenic or oligogenic phenotype can be caused by a mixed epigenetic and genetic and mixed de novo and inherited (MEGDI) model. The MEGDI model may apply to some complex disease traits and could explain negative results in genome-wide genetic scans.

Chromosomal anomalies in individuals with autism: a strategy towards the identification of genes involved in autism

We review the different strategies currently used to try to identify susceptibility genes for idiopathic autism. Although identification of genes is usually straightforward in Mendelian disorders, it has proved to be much more difficult to establish in polygenic disorders like autism. Neither genome screens of affected siblings nor the large number of association studies using candidate genes have resulted in finding autism susceptibility genes. We focus on the alternative approach of 'positional cloning' through chromosomal aberrations in individuals with autism. In particular, balanced aberrations such as reciprocal translocations or inversions offer a unique opportunity, since only the genes in the breakpoint regions are candidate genes. This approach, in combination with others, is likely to produce results in the coming years.

Autism as a disorder of neural information processing: directions for research and targets for therapy

The broad variation in phenotypes and severities within autism spectrum disorders suggests the involvement of multiple predisposing factors, interacting in complex ways with normal developmental courses and gradients. Identification of these factors, and the common developmental path into which they feed, is hampered by the large degrees of convergence from causal factors to altered brain development, and divergence from abnormal brain development into altered cognition and behaviour. Genetic, neurochemical, neuroimaging, and behavioural findings on autism, as well as studies of normal development and of genetic syndromes that share symptoms with autism, offer hypotheses as to the nature of causal factors and their possible effects on the structure and dynamics of neural systems. Such alterations in neural properties may in turn perturb activity-dependent development, giving rise to a complex behavioural syndrome many steps removed from the root causes. Animal models based on genetic, neurochemical, neurophysiological, and behavioural manipulations offer the possibility of exploring these developmental processes in detail, as do human studies addressing endophenotypes beyond the diagnosis itself.