Current Progress and Challenges in the Search for Autism Biomarkers

Autism spectrum disorders (ASD) encompass a range of neurodevelopmental conditions that are clinically and etiologically very heterogeneous. ASD is currently diagnosed entirely on behavioral criteria, but intensive research efforts are focused on identifying biological markers for disease risk and early diagnosis. Here, we discuss recent progress toward identifying biological markers for ASD and highlight specific challenges as well as ethical aspects of translating ASD biomarker research into the clinic.     

Copy number variants in people with autism spectrum disorders and co-morbid psychosis

The genetic association between autism spectrum disorder (ASD) and psychotic disorders such as schizophrenia is complicated and mirrors the clinical overlap between these conditions to some degree. However, no studies to date have examined the genetics of individuals dually diagnosed with both ASD and psychosis. In this study, we present findings of copy number variants (CNVs) from a study of 116 well-characterised individuals with this dual diagnosis. DNA was extracted and arrayed using the Affymetrix CytoScan HD 2.8M array or the Affymetrix Cytogenetics arrays and compared with existing samples from the Database of Genomic Variants and the Simons Simplex Collection of CNVs from individuals with ASD and their families. Twenty-seven novel CNVs ≥20k base pairs were identified in the sample, most occurring in only a single individual, although two were found in two female participants. Forty-nine rare CNVs (<1.5% rate in general population) were also found at significantly higher frequencies than expected. The findings may provide evidence for areas of further study in the understanding of the development of both ASD and psychosis due to the number of affected genetic regions that have not previously been linked to these conditions.     

Public health monitoring of developmental disabilities with a focus on the autism spectrum disorders

Developmental disabilities (DDs) are conditions characterized by physical, cognitive, psychological, sensory, adaptive, and/or communication impairments manifested during development. Approximately 17% of individuals in the United States 18 years and younger have a DD, and for most children the cause of their condition is unknown. Of particular interest are the autism spectrum disorders (ASDs), characterized by unusual social, communication, and behavioral development. Previously autism was thought to be a rare condition, but the number of children receiving services for an ASD has increased dramatically in the last decade. Concerns about increases in DDs, particularly ASDs, their causes, and the high costs of intervention have highlighted the need for systematic public health monitoring. Service provider data, such as annual reporting of special education services or of state DD programs, do not provide a complete estimate of the rates for DDs, including ASDs. Unlike genetic metabolic disorders or congenital hearing loss (HL) for which newborn screening programs can provide accurate prevalence rates, there are currently no genetic or biologic markers for the ASDs to enable consistent and early identification of affected children. Centers for Disease Control and Prevention's (CDC) Metropolitan Atlanta Developmental Disabilities Surveillance Program (MADDSP) is a model for population monitoring of ASDs/DDs that has been implemented in other states. This article discusses the role of ASD/DD tracking in public health, as well as the challenges of ASD/DD tracking, including case definition and identification, associated conditions, linkages, and data access.     

Genetic landmarks through philately - autism spectrum disorders: a genetic update

Autism spectrum disorders (ASD) represent a heterogeneous group of developmental disorders that present a challenge to geneticists because of their complex etiology and inheritance. This article reviews some of the advances in our understanding of causation in ASD and the role in which molecular genetic investigations have helped in unraveling the mystery of ASD. There have been few postage stamps issued relevant to ASD. Because of the need for early diagnosis and improved recognition, some countries may consider issuing stamps to highlight the importance of ASD to the population and to raise awareness and money for research funding.     

Communication, interventions, and scientific advances in autism: A commentary

Autism spectrum disorders (ASD) affect approximately 1 in 150 children across the U.S., and are characterized by abnormal social actions, language difficulties, repetitive or restrictive behaviors, and special interests. ASD include autism (autistic disorder), Asperger Syndrome, and Pervasive Developmental Disorder not otherwise specified (PDD-NOS or atypical autism). High-functioning individuals may communicate with moderate-to-high language skills, although difficulties in social skills may result in communication deficits. Low-functioning individuals may have severe deficiencies in language, resulting in poor communication between the individual and others. Behavioral intervention programs have been developed for ASD, and are frequently adjusted to accommodate specific individual needs. Many of these programs are school-based and aim to support the child in the development of their skills, for use outside the classroom with family and friends. Strides are being made in understanding the factors contributing to the development of ASD, particularly the genetic contributions that may underlie these disorders. Mutant mouse models provide powerful research tools to investigate the genetic factors associated with ASD and its co-morbid disorders. In support, the BTBR T+tf/J mouse strain incorporates ASD-like social and communication deficits and high levels of repetitive behaviors. This commentary briefly reviews the reciprocal relationship between observations made during evidence-based behavioral interventions of high- versus low-functioning children with ASD and the accumulating body of research in autism, including animal studies and basic research models. This reciprocity is one of the hallmarks of the scientific method, such that research may inform behavioral treatments, and observations made during treatment may inform subsequent research.     

The course of psychological disorders in the 1st year after cancer diagnosis

This study investigated the relationship between acute stress disorder (ASD) and posttraumatic stress disorder (PTSD) and comorbid anxiety, depressive, and substance use disorders over the first 12-month period following a cancer diagnosis. Individuals recently diagnosed with 1st onset head and neck or lung malignancy were assessed for ASD within the initial month following their diagnosis and reassessed for PTSD and other psychological disorders at both 6 months and 12 months following their cancer diagnosis. The incidence for PTSD at 12 months (14%) was lower than the incidence for other anxiety (20%) and depressive (20%) disorders. This study points to the need for the development of valid therapeutic interventions to assist this population in the 1st year following their diagnosis.     

Characterization of intellectual disability and autism comorbidity through gene panel sequencing

Intellectual disability (ID) and autism spectrum disorder (ASD) are clinically and genetically heterogeneous diseases. Recent whole exome sequencing studies indicated that genes associated with different neurological diseases are shared across disorders and converge on common functional pathways. Using the Ion Torrent platform, we developed a low‐cost next‐generation sequencing gene panel that has been transferred into clinical practice, replacing single disease‐gene analyses for the early diagnosis of individuals with ID/ASD. The gene panel was designed using an innovative in silico approach based on disease networks and mining data from public resources to score disease‐gene associations. We analyzed 150 unrelated individuals with ID and/or ASD and a confident diagnosis has been reached in 26 cases (17%). Likely pathogenic mutations have been identified in another 15 patients, reaching a total diagnostic yield of 27%. Our data also support the pathogenic role of genes recently proposed to be involved in ASD. Although many of the identified variants need further investigation to be considered disease‐causing, our results indicate the efficiency of the targeted gene panel on the identification of novel and rare variants in patients with ID and ASD.     

Tuberous sclerosis in a patient from Nigeria

Tuberous sclerosis complex (TSC) is an autosomal dominant syndrome characterized by mostly benign tumors of the brain, skin, heart, kidney, and eye. Aberrations in the genes TSC1 and TSC2 which encode hamartin and tuberin, respectively, cause TSC. Because disease manifestations develop over time, early diagnosis and intervention are imperative for patients. TSC is not well described in patients from sub‐Saharan Africa or of black African ancestry. Here, we report on a 4‐year‐old Nigerian boy with skin lesions and cardiac anomalies associated with TSC. Furthermore, we note that in areas with limited resources for genetic diagnoses, the common skin manifestations found in TSC may be especially useful clinical markers.     

The relationship between acute stress disorder and posttraumatic stress disorder: a 2-year prospective evaluation

Previous research established that 78% of a sample of motor vehicle accident survivors initially diagnosed with acute stress disorder (ASD) were subsequently diagnosed with posttraumatic stress disorder (PTSD) at 6 months posttrauma. Although the previous study provided initial evidence for the utility of the ASD diagnosis, the relationship between ASD and PTSD was assessed over a relatively short period. The present study reassessed that original sample 2 years following the trauma to establish the longer term relationship between ASD and PTSD. ASD was diagnosed in 13% of participants, and 21% were diagnosed with subsyndromal ASD. In terms of participants who participated in all 3 assessments, 63% who met the criteria for ASD, 70% who met the criteria for subsyndromal ASD, and 13% who did not meet the criteria for ASD were diagnosed with PTSD at 2 years posttrauma. These findings indicate the importance of considering multiple pathways to the development of PTSD.     

A family study implicates GBE1 in the etiology of autism spectrum disorder

Autism spectrum disorders (ASD) are neurodevelopmental disorders with an estimated heritability of >60%. Family-based genetic studies of ASD have generally focused on multiple small kindreds, searching for de novo variants of major effect. We hypothesized that molecular genetic analysis of large multiplex families would enable the identification of variants of milder effects. We studied a large multigenerational family of European ancestry with multiple family members affected with ASD or the broader autism phenotype (BAP). We identified a rare heterozygous variant in the gene encoding 1,4-ɑ-glucan branching enzyme 1 (GBE1) that was present in seven of seven individuals with ASD, nine of ten individuals with the BAP, and none of four tested unaffected individuals. We genotyped a community-acquired cohort of 389 individuals with ASD and identified three additional probands. Cascade analysis demonstrated that the variant was present in 11 of 13 individuals with familial ASD/BAP and neither of the two tested unaffected individuals in these three families, also of European ancestry. The variant was not enriched in the combined UK10K ASD cohorts of European ancestry but heterozygous GBE1 deletion was overrepresented in large ASD cohorts, collectively suggesting an association between GBE1 and ASD.     

Superior discrimination of speech pitch and its relationship to verbal ability in autism spectrum disorders

Whilst hypersensitivity to pitch information appears to be characteristic of many individuals with autism spectrum disorders little is known about the implications of such a tendency for language acquisition and development. Discrimination of systematically varied pitch differences between pairs of words, nonwords, and nonspeech pitch contour analogues was assessed in children with autism spectrum disorders (ASD) and matched controls. The findings revealed superior performance in ASD, although, like controls, discrimination of pitch in speech stimuli was poorer in this group than for nonspeech stimuli. Whilst it was hypothesized that enhanced processing of speech pitch would correlate negatively with receptive language skills in ASD, the findings did not fully support this, and enhanced discrimination skills were observed in individuals without significant language impairment. The implications of these findings for understanding heterogeneity of language ability in ASD are discussed.     

Superior discrimination of speech pitch and its relationship to verbal ability in autism spectrum disorders

Whilst hypersensitivity to pitch information appears to be characteristic of many individuals with autism spectrum disorders little is known about the implications of such a tendency for language acquisition and development. Discrimination of systematically varied pitch differences between pairs of words, nonwords, and nonspeech pitch contour analogues was assessed in children with autism spectrum disorders (ASD) and matched controls. The findings revealed superior performance in ASD, although, like controls, discrimination of pitch in speech stimuli was poorer in this group than for nonspeech stimuli. Whilst it was hypothesized that enhanced processing of speech pitch would correlate negatively with receptive language skills in ASD, the findings did not fully support this, and enhanced discrimination skills were observed in individuals without significant language impairment. The implications of these findings for understanding heterogeneity of language ability in ASD are discussed.     

The relationship between acute stress disorder and posttraumatic stress disorder following cancer

In this study, the authors investigated the relationship between acute stress disorder (ASD) and posttraumatic stress disorder (PTSD) following cancer diagnosis. Patients who were recently diagnosed with 1st onset head and neck or lung malignancy (N=82) were assessed for ASD within the initial month following their diagnosis and reassessed (n=63) for PTSD 6 months following their cancer diagnosis. At the initial assessment, 28% of patients had ASD, and 32% displayed subsyndromal ASD. At follow-up, PTSD was diagnosed in 53% of patients who had been diagnosed with ASD and in 11% of those who had not met criteria for ASD; 36% of patients with PTSD did not initially display ASD. In this study, the authors question the use of the ASD diagnosis to identify recently diagnosed patients at risk of PTSD.     

Mutation pattern and genotype-phenotype correlations of SETD2 in neurodevelopmental disorders

SETD2 encodes an important protein for epigenetic modification of histones which plays an essential role in early development. Variants in SETD2 have been reported in neurodevelopmental disorders including autism spectrum disorder (ASD). However, most de novo SETD2 variants were reported in different large-cohort sequencing studies, mutation pattern and comprehensive genotype-phenotype correlations for SETD2 are still lacking. We have applied target sequencing to identify rare, clinical-relevant SETD2 variants and detected two novel de novo SETD2 variants, including a de novo splicing variant (NM_014159: c.4715+1G>A) and a de novo missense variant (c.3185C>T: p.P1062L) in two individuals with a diagnosis of ASD. To analyze the correlations between SETD2 mutations and corresponding phenotypes, we systematically review the reported individuals with de novo SETD2 variants, classify the pathogenicity, and analyze the detailed phenotypes. We subsequently manually curate 17 SETD2 de novo variants in 17 individuals from published literature. Individuals with de novo SETD2 variants present common phenotypes including speech and motor delay, intellectual disability, macrocephaly, ASD, overgrowth and recurrent otitis media. Our study reveals new SETD2 mutations and provided a relatively homozygous phenotype spectrum of SETD2-related neurodevelopmental disorders which will be beneficial for disease classification and diagnosis in clinical practice.     

Attention-deficit / hyperactivity disorder in autism spectrum disorders

According to the DSM-IV-TR, symptoms of inattention and hyperactivity are frequent in children with Autism Spectrum Disorders (ASD). This statement is supported by clinical observation and formal assessment. However, ASD diagnosis is still among the exclusion criteria for the Attention-Deficit/Hyperactivity Disorder (ADHD). Such exclusion generates controversy and questions regarding the need and benefits of maintaining or not these separations; so much so, that the proposed criteria for the DSM-V eliminate that exclusion condition. It is necessary a better understanding of the comorbidity between both entities in order to be able to have an appropriate sequence of the intervention goals. For that reason, if inattention and hyperactivity in individuals with ASD are considered as a representation of a comorbid diagnosis of ADHD, treatment plans for this group would be better adjusted and more likely to offer a real benefit in the outcome of their adaptive functioning.     

Abnormalities of cholesterol metabolism in autism spectrum disorders.

Although Smith-Lemli-Opitz Syndrome (SLOS), a genetic condition of impaired cholesterol biosynthesis, is associated with autism [Tierney et al., 2001; Am J Med Genet 98:191-200.], the incidence of SLOS and other sterol disorders among individuals with autism spectrum disorders (ASD) is unknown. This study investigated (1) the incidence of biochemically diagnosed SLOS in blood samples from a cohort of subjects with ASD from families in which more than one individual had ASD and (2) the type and incidence of other sterol disorders in the same group. Using gas chromatography/mass spectrometry, cholesterol, and its precursor sterols were quantified in 100 samples from subjects with ASD obtained from the Autism Genetic Resource Exchange (AGRE) specimen repository. Although no sample had sterol levels consistent with SLOS, 19 samples had total cholesterol levels lower than 100 mg/dl, which is below the 5th centile for children over age 2 years. These findings suggest that, in addition to SLOS, there may be other disorders of sterol metabolism or homeostasis associated with ASD.     

The Under- and Over-Identification of Autism: Factors Associated With Diagnostic Referral

As reported prevalence and public awareness of Autism Spectrum Disorder (ASD) have grown in recent years, clinicians will likely see increased referrals for suspected ASD. The current study sought to elucidate factors associated with referral for possible ASD, as well as diagnostic outcome among youth referred for suspected ASD. Youth referred for psychological evaluations at an outpatient clinic (N = 69, 6–18 years, 48 male) were categorized into four groups: referred for suspected ASD and diagnosed as such, referred for ASD and not diagnosed as such, not referred for ASD but diagnosed as such, and neither referred for nor diagnosed with ASD. Approximately half of cases referred for suspected ASD did not meet diagnostic criteria. A significant effect of group was found for cognitive ability and anxiety. Youth receiving ASD diagnoses, regardless of whether they were referred for suspected ASD, demonstrated lower cognitive ability than children not receiving ASD diagnoses. Youth neither referred for nor diagnosed with ASD demonstrated lower anxiety than those who were referred and diagnosed. Maternal education significantly differed among the four groups. Although group differences are seen for youth cognitive ability, anxiety, and maternal education, we found no clear indicators differentiating referrals that were “accurate” (i.e., those diagnosed with ASD) and those that were not (i.e., those who did not receive ASD diagnosis). Comorbidity was high in all groups, including those referred primarily for ASD assessment, underscoring the importance of comprehensive assessment regardless of specificity of the referral.     

Behavioral profiles and symptoms of autism in CHARGE syndrome: preliminary Canadian epidemiological data

Individuals with CHARGE syndrome were identified through the Canadian Pediatric Surveillance Program (CPSP). From this population-based cohort (n=78), we present data on developmental and behavioral characteristics for the first 13 individuals (eight males, five females) for whom assessments are complete. Standardized parent questionnaires on development and behavior were followed by a structured telephone interview, with a specific emphasis on symptoms of autistic spectrum disorder (ASD). Preliminary results confirm that individuals with CHARGE syndrome have relatively low adaptive behavior skills, motor impairments being particularly significant. Most individuals did not present with significant behavior problems; however, evidence of ASD symptoms was judged to be moderate to strong in six of the ten children who were above the age of 4-5 years. Results are discussed with reference to the challenges inherent in the diagnosis of autism in individuals with sensory impairments, and to the implications for understanding the etiology of CHARGE syndrome and of ASD.     

A pathogenetic model of autism involving Purkinje cell loss through anti-GAD antibodies

Autism is a medical enigma, lacking truly effective treatments. Both genetics and environmental factors are recognized as players in the development of autism spectrum disorders (ASDs). Nevertheless, the exact mechanism(s) for the development of ASDs is (are) not known primarily because current understanding about the etiology of the disease is limited. Selective loss of Purkinje cells and the cerebellar atrophies are the neurological abnormalities most consistently found in persons diagnosed with autism. Because Purkinje cells are involved in motor coordination, working memory and learning, loss of these cells are likely to cause symptoms defining behavioral parameters of ASD. Currently the mechanism(s) for the loss of Purkinje cells in the cerebella of autistic individual is (are) not understood. Here we postulate a hypothesis for the development of autistic symptoms, severity of which is based on the extent of Purkinje cell loss triggered by Glutamate acid decarboxylase antibody (GAD-Ab). This model accommodates any genetic basis of autism and immunogenic triggers resulting GAD-Ab in the blood of the mother while pregnant with the child diagnosed autistic after birth or of an individual diagnosed with autism some time in the life time. Identification and characterization of GAD-Abs from pregnant mothers with a family history of autism, from children with autistic siblings, and individuals diagnosed with autism may allow find preventive and new therapeutic avenues.     

Memory for past events: movement and action chains in high-functioning autism spectrum disorders

In the present study, we assessed whether individuals with autism spectrum disorders (ASD) show memory impairments for previously performed actions, as previously suggested for people suffering from obsessive–compulsive disorder (OCD) (Ecker and Engelkamp in Behav Cogn Psychother 23:349–371, 1995; Merckelbach and Wessel in J Nerv Ment Dis 188(12):846–848, 2000). To test this possibility, we explored verbal memory for actions in individuals with a diagnosis of ASD, with and without co-morbidity for OCD, and in controls matched for age and gender. Participants observed or observed and enacted a number of actions while listening to the corresponding phrases being spoken. After a suitable delay, they were submitted to an old/new recognition task. Results showed that ASD individuals with OCD were less accurate and slower in responding compared to ASD individuals without OCD and controls, particularly when dealing with phrases describing simple movements. In contrast, ASD participants without OCD were more impaired when phrases described complex actions that involved pantomiming object use or coordinating movements of multiple body parts. These findings are discussed in terms of differential organization of the motor trace for simple versus complex actions in ASD individuals according to the concurrent presence of OCD.