Head circumference in autism and other pervasive developmental disorders

An Exploration of Physical and Phenotypic Characteristics of Bangladeshi Children with Autism Spectrum Disorder

This study explored the physical and clinical phenotype of Bangladeshi children with autism spectrum disorder (ASD). A totally of 283 children who were referred for screening and administered Module 1 of the Autism Diagnostic Observation Schedule (ADOS) were included. Overall, 209 met the ADOS algorithmic cutoff for ASD. A trend for greater weight and head circumference was observed in children with ASD versus non-ASD. Head circumference was significantly (p < 0.03) larger in ASD males compared with non-ASD males. A trend was also observed for symptom severity, higher in females than males (p = 0.068), with further analyses demonstrating that social reciprocity (p < 0.014) and functional play (p < 0.03) were significantly more impaired in ASD females than males. The findings help understand sex differences in ASD.

Combined Effects of Virtual Reality and Computer Game-Based Cognitive Therapy on the Development of Visual-Motor Integration in Children with Intellectual Disabilities: A Pilot Study

PURPOSE

Visual-motor integration is a good indicator of a child's overall developmental and functional level. This study investigated the combined effects of virtual reality (VR) and computer game-based cognitive therapy on the development of visual-motor integration in children with intellectual disabilities.

METHODS

The study used a single-group pre-post study design and 13 children with intellectual disabilities who were recruited from a community rehabilitation center participated in the study. We used the Wii VR video game and the CoTras computer game to deliver cognitive therapy over 12 sessions. The Bruininks-Oseretsky Test of Motor Proficiency-2 (BOT-2) was used to evaluate motor function related to visual-motor integration to identify changes in function, and the Developmental Test of Visual Perception-2 (DTVP-2) was used to assess changes in visual perception function associated with visual-motor integration.

RESULTS

The VR and computer game-based cognitive therapy has shown significant difference in total standard score of BOT-2 associated with visual-motor integration representing improved motor function (p < 0.01). Comparison of the DTVP-2 scores showed the significant difference in visual-motor integration of spatial relation and visual-motor speed (p < 0.05), motor-reduced visual perception (p < 0.01), and general visual perception (p < 0.01).

CONCLUSIONS

Results of this study provide useful evidence supporting the possibility of combined VR and computer game-based cognitive therapy for children with intellectual disabilities.

A voxel-wise assessment of growth differences in infants developing autism spectrum disorder

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Pediatric neuroimaging study of Autism Spectrum Disorder.

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Longitudinal Tensor Based Morphometry of the presymptomatic period of ASD.

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Differences in voxelwise growth trajectories of children with ASD.

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Regions with differences have been implicated in the core symptoms of ASD.

Autism Spectrum Disorder (ASD) is a phenotypically and etiologically heterogeneous developmental disorder typically diagnosed around 4 years of age. The development of biomarkers to help in earlier, presymptomatic diagnosis could facilitate earlier identification and therefore earlier intervention and may lead to better outcomes, as well as providing information to help better understand the underlying mechanisms of ASD. In this study, magnetic resonance imaging (MRI) scans of infants at high familial risk, from the Infant Brain Imaging Study (IBIS), at 6, 12 and 24 months of age were included in a morphological analysis, fitting a mixed-effects model to Tensor Based Morphometry (TBM) results to obtain voxel-wise growth trajectories. Subjects were grouped by familial risk and clinical diagnosis at 2 years of age. Several regions, including the posterior cingulate gyrus, the cingulum, the fusiform gyrus, and the precentral gyrus, showed a significant effect for the interaction of group and age associated with ASD, either as an increased or a decreased growth rate of the cerebrum. In general, our results showed increased growth rate within white matter with decreased growth rate found mostly in grey matter. Overall, the regions showing increased growth rate were larger and more numerous than those with decreased growth rate. These results detail, at the voxel level, differences in brain growth trajectories in ASD during the first years of life, previously reported in terms of overall brain volume and surface area.

Neurological disorders in autism: A systematic review and meta-analysis

LAY ABSTRACT

Neurological disorders, such as epilepsy and cerebral palsy, have been reported to occur among individuals with autism beyond chance and may have an impact on daily living across the lifespan. Although there has been research investigating neurological disorders in autism, the findings are not always conclusive. Previous summaries of existing studies have not evaluated the full range of neurological disorders. This study aimed to comprehensively explore the neurological problems appearing in autism to provide updated information that is needed for better healthcare and support in this population. We looked at already published studies focusing on risk or frequency of neurological disorders in autism. Our results suggest that individuals with autism are more likely than the general population to have a range of neurological disorders, including epilepsy, macrocephaly, hydrocephalus, cerebral palsy, migraine/headache, and inborn abnormalities of the nervous system. In order to provide individualized healthcare and support of high quality to individuals diagnosed with autism, health care professionals and other support providers need to be attentive to neurological complications. To further improve our understanding about the link between autism and neurological disorders, future research should follow the neurological health of children who are diagnosed with or are at increased likelihood of autism.

Neuropsychiatric "Comorbidity" as Causal Influence in Autism

Behavioral comorbidity is the rule rather than the exception in autism spectrum disorder (ASD), and the co-occurrence of autistic traits with subclinical manifestations of other psychiatric syndromes (eg, anxiety, developmental coordination disorder) extends to the general population, where there is strong evidence for overlap in the respective genetic causes. An ASD "comorbidity" can have several fundamentally distinct causal origins: it can arise due to shared genetic risk between ASD and non-ASD phenotypes (eg, ASD and microcephaly in the context of the MECP2 mutation), as a "secondary symptom" of ASD when engendered by the same causal influence (eg, epilepsy in channelopathies associated with ASD), due to chance co-occurrence of ASD with a causally independent liability (eg, ASD and diabetes), or as the late manifestation of an independent causal influence on ASD (eg, attention-deficit/hyperactivity disorder). Here, we review evidence for the latter, that is, the role of nonspecific causal influences on the development of ASD itself. The notion that nonspecific insults to neural development, either inherited or acquired, might augment the impact of ASD-specific genetic susceptibilities in contributing to its cause has not been appreciated in the literature on comorbidity, and has significant implications for both personalized intervention and future research. Prior biomarker studies of ASD have typically not accounted for variation in such traits. The statistical power of future studies, particularly in autism genetics and neuroimaging, can be enhanced by more comprehensive attention to the measurement of comorbid behavioral traits that index causal influences on the disorder, among not only cases but (importantly) controls.

The journey to autism: Insights from neuroimaging studies of infants and toddlers

By definition, autism spectrum disorder (ASD) is a neurodevelopmental disorder that emerges during early childhood. It is during this time that infants and toddlers transition from appearing typical across multiple domains to exhibiting the behavioral phenotype of ASD. Neuroimaging studies focused on this period of development have provided crucial knowledge pertaining to this process, including possible mechanisms underlying pathogenesis of the disorder and offering the possibility of prodromal or presymptomatic prediction of risk. In this paper, we review findings from structural and functional brain imaging studies of ASD focused on the first years of life and discuss implications for next steps in research and clinical applications.

Facilitating Autism Research

Early autism research focused on behavior and cognition. In recent decades, the pace of research has accelerated, and advances in imaging and genetics have allowed the accumulation of biological data. Nevertheless, a coherent picture of the syndrome at either phenotypic or biological level has not emerged. We see two fundamental obstacles to progress in basic understanding of autism. First, the two defining features (impairment in social interactions and communication, and restricted, repetitive behaviors and interests) are historically seen as integrally related. Others hold that these two major traits are fractionable and must be studied independently, casting doubt on autism as a coherent syndrome. Second, despite much recent research on brain structure and function, environmental factors, and genetics/genomics, findings on the biological level have not generally aligned well with those on the phenotypic level. In the first two sections, we explore these challenges, and in the third section, we review approaches that may facilitate progress, such as (1) including in studies all individuals defined by social impairment without regard to repetitive behaviors, (2) forming narrowly defined subtypes by thorough characterization on specific features, both diagnostic and non-diagnostic, (3) focusing on characteristics that may be relatively robust to environmental influence, (4) studying children as early as possible, minimizing environmental influence, and including longitudinal course as an important part of the phenotype, (5) subtyping by environmental risk factors, (6) distinguishing between what participants can do and what they typically do, and (7) aggregating large data sets across sites. (JINS, 2017, 23, 903-915).

Neuroanatomical variation in autism spectrum disorder: A comprehensive review

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by impairments in socialization, communication, and behavior. Many investigators have described the anatomical abnormalities in autistic brains, in an attempt to correlate them with the manifestations of ASD. Herein, we reviewed all the available literature about the neuroanatomical findings in ASD available via "PubMed" and "Google Scholar." References found in review articles were also searched manually. There was substantial discrepancy throughout the literature regarding the reported presence and significance of neuroanatomical findings in ASD, and this is thoroughly discussed in the present review.

Head circumference and brain size in autism spectrum disorder: A systematic review and meta-analysis

Macrocephaly and brain overgrowth have been associated with autism spectrum disorder. We performed a systematic review and meta-analysis to provide an overall estimate of effect size and statistical significance for both head circumference and total brain volume in autism. Our literature search strategy identified 261 and 391 records, respectively; 27 studies defining percentages of macrocephalic patients and 44 structural brain imaging studies providing total brain volumes for patients and controls were included in our meta-analyses. Head circumference was significantly larger in autistic compared to control individuals, with 822/5225 (15.7%) autistic individuals displaying macrocephaly. Structural brain imaging studies measuring brain volume estimated effect size. The effect size is higher in low functioning autistics compared to high functioning and ASD individuals. Brain overgrowth was recorded in 142/1558 (9.1%) autistic patients. Finally, we found a significant interaction between age and total brain volume, resulting in larger head circumference and brain size during early childhood. Our results provide conclusive effect sizes and prevalence rates for macrocephaly and brain overgrowth in autism, confirm the variation of abnormal brain growth with age, and support the inclusion of this endophenotype in multi-biomarker diagnostic panels for clinical use.

Increased Surface Area, but not Cortical Thickness, in a Subset of Young Boys With Autism Spectrum Disorder

The Autism Phenome Project is the largest, single site, longitudinal magnetic resonance imaging (MRI) study of young children with autism spectrum disorder (ASD). Previous analyses from this cohort have shown that the children with autism have a total brain volume at time 1 (∼3 years of age) that is 6% larger than typically developing (TD) children. This finding is driven primarily by 15% of the boys with ASD that have disproportionate megalencephaly (ASD-DM) or brain size that is 1.5 standard deviations above what would be expected for the child's height. In the current study, cerebral cortical grey matter volume, thickness, and surface area were assayed from MRI scans of 112, 3-year-old boys with ASD and 50 age-matched TD boys. The boys with ASD-DM (n = 17) were analyzed separately from the boys with normal brain size (ASD-N, n = 95). Previous studies of cortical thickness and surface area for ASD children in this age range have come to diametrically different conclusions concerning the significance of cortical thickness vs. surface area. Current analyses indicate that cortical thickness was comparable across the ASD and TD groups. However, surface area was significantly greater in the ASD group compared to the TD group. This result was driven largely by the children with ASD-DM. Even in the ASD-DM group, not all cortical regions demonstrated increased surface area. These results provide strong evidence that the early cortical overgrowth associated with ASD is due primarily to increased surface area and not to increased cortical thickness.

Early head growth in infants at risk of autism: a baby siblings research consortium study

OBJECTIVE

Although early brain overgrowth is frequently reported in autism spectrum disorder (ASD), the relationship between ASD and head circumference (HC) is less clear, with inconsistent findings from longitudinal studies that include community controls. Our aim was to examine whether head growth in the first 3 years differed between children with ASD from a high-risk (HR) sample of infant siblings of children with ASD (by definition, multiplex), HR siblings not diagnosed with ASD, and low-risk (LR) controls.

METHOD

Participants included 442 HR and 253 LR infants from 12 sites of the international Baby Siblings Research Consortium. Longitudinal HC data were obtained prospectively, supplemented by growth records. Random effects nonlinear growth models were used to compare HC in HR infants and LR infants. Additional comparisons were conducted with the HR group stratified by diagnostic status at age 3: ASD (n = 77), developmental delay (DD; n = 32), and typical development (TD; n = 333). Nonlinear growth models were also developed for height to assess general overgrowth associated with ASD.

RESULTS

There was no overall difference in head circumference growth over the first 3 years between HR and LR infants, although secondary analyses suggested possible increased total growth in HR infants, reflected by the model asymptote. Analyses stratifying the HR group by 3-year outcomes did not detect differences in head growth or height between HR infants who developed ASD and those who did not, nor between infants with ASD and LR controls.

CONCLUSION

Head growth was uninformative as an ASD risk marker within this HR cohort.

Compared to what? Early brain overgrowth in autism and the perils of population norms

BACKGROUND

Early brain overgrowth (EBO) in autism spectrum disorder (ASD) is among the best replicated biological associations in psychiatry. Most positive reports have compared head circumference (HC) in ASD (an excellent proxy for early brain size) with well-known reference norms. We sought to reappraise evidence for the EBO hypothesis given 1) the recent proliferation of longitudinal HC studies in ASD, and 2) emerging reports that several of the reference norms used to define EBO in ASD may be biased toward detecting HC overgrowth in contemporary samples of healthy children.

METHODS

Systematic review of all published HC studies in children with ASD. Comparison of 330 longitudinally gathered HC measures between birth and 18 months from male children with autism (n = 35) and typically developing control subjects (n = 22).

RESULTS

In systematic review, comparisons with locally recruited control subjects were significantly less likely to identify EBO in ASD than norm-based studies (p < .001). Through systematic review and analysis of new data, we replicate seminal reports of EBO in ASD relative to classical HC norms but show that this overgrowth relative to norms is mimicked by patterns of HC growth age in a large contemporary community-based sample of US children (n ~ 75,000). Controlling for known HC norm biases leaves inconsistent support for a subtle, later emerging and subgroup specific pattern of EBO in clinically ascertained ASD versus community control subjects.

CONCLUSIONS

The best-replicated aspects of EBO reflect generalizable HC norm biases rather than disease-specific biomarkers. The potential HC norm biases we detail are not specific to ASD research but apply throughout clinical and academic medicine.

Head circumferences in twins with and without Autism Spectrum Disorders

To determine the genetic relationship between head circumference (HC) and Autism Spectrum Disorders (ASDs). Twin pairs with at least one twin with an ASD were assessed. HCs in affected and unaffected individuals were compared, as were HC correlations in monozygotic and dizygotic pairs. 404 subjects, ages 4-18, were included. 20 % of males and 27 % of females with an ASD had macrocephaly. Unaffected co-twins showed similar rates (16 % of males and 22 % of females). Statistical analysis revealed no significant difference in HCs between affected and unaffected twins. Twins with ASDs and unaffected co-twins have similar HCs and increased rates of macrocephaly. Correlations demonstrated partial inheritance of HCs. Thus, macrocephaly may represent an endophenotype in ASDs.

Neurobiology meets genomic science: the promise of human-induced pluripotent stem cells

The recent introduction of the induced pluripotent stem cell technology has made possible the derivation of neuronal cells from somatic cells obtained from human individuals. This in turn has opened new areas of investigation that can potentially bridge the gap between neuroscience and psychopathology. For the first time we can study the cell biology and genetics of neurons derived from any individual. Furthermore, by recapitulating in vitro the developmental steps whereby stem cells give rise to neuronal cells, we can now hope to understand factors that control typical and atypical development. We can begin to explore how human genes and their variants are transcribed into messenger RNAs within developing neurons and how these gene transcripts control the biology of developing cells. Thus, human-induced pluripotent stem cells have the potential to uncover not only what aspects of development are uniquely human but also variations in the series of events necessary for normal human brain development that predispose to psychopathology.

Could head circumference be used to screen for autism in young males with developmental delay?

AIM

Research has suggested an abnormal acceleration in head circumference growth in children with autism within the first 12 months of life. This study aimed to examine head circumference at birth and head circumference growth rates in young children with autism and developmental delay, and young children with developmental delay without autism.

METHODS

This study assessed head circumference at birth and rate of change in head circumference in young children with autism (n=86) and children with developmental delay without autism (n=40).

RESULTS

For both groups of children, head circumference at birth and head circumference growth were compared with Centers for Disease Control normative data. No differences were found between the group of children with autism and developmental delay compared with the group with developmental delay only. However, when the sample was compared with a range of selected Centers for Disease Control normative medians, the children with autism were found to have significantly smaller head circumferences at birth and significantly larger head circumference at 18.5 months of age.

CONCLUSIONS

These results are discussed in relation to the potential of accelerated head circumference growth as an early marker for autism. This study failed to find a difference in the head circumferences of children with autism and developmental delay and children with developmental delay only, thus suggesting that head circumference measurement has limited value as an early marker for autism.

A 380-kb Duplication in 7p22.3 Encompassing the LFNG Gene in a Boy with Asperger Syndrome

De novo genomic aberrations are considered an important cause of autism spectrum disorders. We describe a de novo 380-kb gain in band p22.3 of chromosome 7 in a patient with Asperger syndrome. This duplicated region contains 9 genes including the LNFG gene that is an important regulator of NOTCH signaling. We suggest that this copy number variation has been a contributive factor to the occurrence of Asperger syndrome in this patient.

Callosal fiber length and interhemispheric connectivity in adults with autism: brain overgrowth and underconnectivity

Typical adults show an inverse relation between callosal fiber length and degree of interhemispheric connectivity. This has been hypothesized to be a consequence of the influence of conduction delays and cellular costs during development on axonal pruning, both of which increase with fiber length. Autism spectrum disorder (ASD) provides a test of this hypothesis: Children with ASD are known to have enlarged brains; thus, adults with ASD should show reductions in interhemispheric connectivity proportional to their degree of brain overgrowth during development. This prediction was tested by assessing the relation between both the size and structure of the corpus callosum and callosal fiber length, adjusting for intracranial volume, which is thought to reflect maximum brain size achieved during development. Using tractography to estimate the length of callosal fibers emanating from all areas of cortex, and through which region of the corpus callosum they pass, we show that adults with ASD show an inverse relation between callosal fiber length, adjusted for intracranial volume, and callosum size, and a positive relation between adjusted callosal fiber length and radial diffusivity. The results provide support for the hypothesized impact of fiber length during development.

Early generalized overgrowth in boys with autism

CONTEXT

Multiple studies have reported an overgrowth in head circumference (HC) in the first year of life in autism. However, it is unclear whether this phenomenon is independent of overall body growth and whether it is associated with specific social or cognitive features.

OBJECTIVES

To examine the trajectory of early HC growth in autism compared with control groups; to assess whether HC growth in autism is independent of height and weight growth during infancy; and to examine HC growth from birth to 24 months in relationship to social, verbal, cognitive, and adaptive functioning levels.

DESIGN

Retrospective study.

SETTING

A specialized university-based clinic.

PARTICIPANTS

Boys diagnosed as having autistic disorder (n = 64), pervasive developmental disorder-not otherwise specified (n = 34), global developmental delay (n = 13), and other developmental problems (n = 18) and typically developing boys (n = 55).

MAIN OUTCOME MEASURES

Age-related changes in HC, height, and weight between birth and age 24 months; measures of social, verbal, and cognitive functioning at age 2 years.

RESULTS

Compared with typically developing controls, boys with autism were significantly longer by age 4.8 months, had a larger HC by age 9.5 months, and weighed more by age 11.4 months (P = .05 for all). None of the other clinical groups showed a similar overgrowth pattern. Boys with autism who were in the top 10% of overall physical size in infancy exhibited greater severity of social deficits (P = .009) and lower adaptive functioning (P = .03).

CONCLUSIONS

Boys with autism experienced accelerated HC growth in the first year of life. However, this phenomenon reflected a generalized process affecting other morphologic features, including height and weight. The study highlights the importance of studying factors that influence not only neuronal development but also skeletal growth in autism.

Progress in understanding autism: 2007-2010

Scientific progress is discussed in relation to clinical issues; genetic issues; environmental issues; and the state of play on psychological treatments. It is concluded that substantial gains in knowledge have been achieved during the last 3 years, and there have been some unexpected findings, but major puzzles remain. We should be hopeful of ever greater gains in the years ahead, but both prevention and cure remain elusive.

Israeli children with autism spectrum disorder are not macrocephalic

The prevalence of macrocephaly in autism spectrum disorder is reported to be much higher than in the general population, 12% to 37%. Progressive macrocephaly is even considered a warning sign for the development of autism. We evaluated the prevalence of an abnormal head circumference in children with autism in Israel and compared it with the head circumferences of children with developmental language disorder and children with normal development. We did not find a higher prevalence of macrocephaly among Israeli children with autism spectrum disorder (4.4%). Although children with autism spectrum disorder had a significantly higher rate of a head circumference above the 75th percentile compared with children with developmental language disorder, it was not significantly different compared with normal controls. We conclude that there is no increased prevalence of macrocephaly in Israeli children with autism; this can be attributed to a different genetic background.

Neural stem cell regulation, fibroblast growth factors, and the developmental origins of neuropsychiatric disorders

There is increasing appreciation for the neurodevelopmental underpinnings of many psychiatric disorders. Disorders that begin in childhood such as autism, language disorders or mental retardation as well as adult-onset mental disorders may have origins early in neurodevelopment. Neural stem cells (NSCs) can be defined as self-renewing, multipotent cells that are present in both the embryonic and adult brain. Several recent research findings demonstrate that psychiatric illness may begin with abnormal specification, growth, expansion and differentiation of embryonic NSCs. For example, candidate susceptibility genes for schizophrenia, autism and major depression include the signaling molecule Disrupted In Schizophrenia-1 (DISC-1), the homeodomain gene engrailed-2 (EN-2), and several receptor tyrosine kinases, including brain-derived growth factor and fibroblast growth factors, all of which have been shown to play important roles in NSCs or neuronal precursors. We will discuss here stem cell biology, signaling factors that affect these cells, and the potential contribution of these processes to the etiology of neuropsychiatric disorders. Hypotheses about how some of these factors relate to psychiatric disorders will be reviewed.

Volumetric and voxel-based morphometry findings in autism subjects with and without macrocephaly

This study sought to replicate Herbert et al. (2003a), which found increased overall white matter (WM) volume in subjects with autism, even after controlling for head size differences. To avoid the possibility that greater WM volume in autism is merely an epiphenomena of macrocephaly overrepresentation associated with the disorder, the current study included control subjects with benign macrocephaly. The control group also included subjects with a reading disability to insure cognitive heterogeneity. WM volume in autism was significantly larger, even when controlling for brain volume, rate of macrocephaly, and other demographic variables. Autism and controls differed little on whole-brain WM voxel-based morphometry (VBM) analyses suggesting that the overall increase in WM volume was non-localized. Autism subjects exhibited a differential pattern of IQ relationships with brain volumetry findings from controls. Current theories of brain overgrowth and their importance in the development of autism are discussed in the context of these findings.

Candidate gene study of HOXB1 in autism spectrum disorder

BACKGROUND

HOXB1 plays a major role in brainstem morphogenesis and could partly determine the cranial circumference in conjunction with HOXA1. In our sample, HOXA1 alleles significantly influence head growth rates both in autistic patients and in population controls. An initial report, suggesting that HOXB1 could confer autism vulnerability in interaction with HOXA1, was not confirmed by five small association studies.

METHODS

Our sample includes 269 autistic individuals, belonging to 219 simplex and 28 multiplex families. A mutational analysis of the two exons and flanking intronic sequences of the HOXB1 gene was carried out in 84 autistic patients by denaturing high performance liquid chromatography, followed by DNA sequencing. Identified rare variants were then searched by a restriction analysis in 236 autistic patients and 325-345 controls. Case-control and family-based association studies were performed on two common variants in 169 Italian patients versus 184 Italian controls and in 247 trios.

RESULTS

We identified three common polymorphisms, rs72338773 [c.82insACAGCGCCC (INS/nINS)], rs12939811 [c.309A>T (Q103H)], and rs7207109 [c.450G>A (A150A)] and three rare variants, namely IVS1+63G>A, rs35115415 [c.702G>A (V234V)] and c.872_873delinsAA (S291N). SNPs rs72338773 and rs12939811 were not associated with autism, using either a case-control (alleles, exact P = 0.13) or a family-based design [transmission/disequilibrium test (TDT)chi2 = 1.774, P = 0.183]. The rare variants, all inherited from one of the parents, were present in two Italian and in two Caucasian-American families. Autistic probands in two families surprisingly inherited a distinct rare variant from each parent. The IVS1+63A allele was present in 3/690 control chromosomes, whereas rare alleles at rs35115415 and c.872_873delinsAA (S291N) were not found in 662 and 650 control chromosomes, respectively. The INS-T309 allele influenced head size, but its effect appears more modest and shows no interaction with HOXA1 alleles. The INS-T309 allele is also associated with more severe stereotypic behaviours, according to ADI-R scores (N = 60 patients, P < 0.01).

CONCLUSIONS

HOXB1 mutations do not represent a common cause of autism, nor do HOXB1 common variants play important roles in autism vulnerability. HOXB1 provides minor, albeit detectable contributions to head circumference in autistic patients, with HOXA1 displaying more prominent effects. HOXB1 variants may modulate the clinical phenotype, especially in the area of stereotypic behaviours.

Investigation of post-transcriptional gene regulatory networks associated with autism spectrum disorders by microRNA expression profiling of lymphoblastoid cell lines

Background

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by abnormalities in reciprocal social interactions and language development and/or usage, and by restricted interests and repetitive behaviors. Differential gene expression of neurologically relevant genes in lymphoblastoid cell lines from monozygotic twins discordant in diagnosis or severity of autism suggested that epigenetic factors such as DNA methylation or microRNAs (miRNAs) may be involved in ASD.

Methods

Global miRNA expression profiling using lymphoblasts derived from these autistic twins and unaffected sibling controls was therefore performed using high-throughput miRNA microarray analysis. Selected differentially expressed miRNAs were confirmed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis, and the putative target genes of two of the confirmed miRNA were validated by knockdown and overexpression of the respective miRNAs.

Results

Differentially expressed miRNAs were found to target genes highly involved in neurological functions and disorders in addition to genes involved in gastrointestinal diseases, circadian rhythm signaling, as well as steroid hormone metabolism and receptor signaling. Novel network analyses of the putative target genes that were inversely expressed relative to the relevant miRNA in these same samples further revealed an association with ASD and other co-morbid disorders, including muscle and gastrointestinal diseases, as well as with biological functions implicated in ASD, such as memory and synaptic plasticity. Putative gene targets (ID3 and PLK2) of two RT-PCR-confirmed brain-specific miRNAs (hsa-miR-29b and hsa-miR-219-5p) were validated by miRNA overexpression or knockdown assays, respectively. Comparisons of these mRNA and miRNA expression levels between discordant twins and between case-control sib pairs show an inverse relationship, further suggesting that ID3 and PLK2 are in vivo targets of the respective miRNA. Interestingly, the up-regulation of miR-23a and down-regulation of miR-106b in this study reflected miRNA changes previously reported in post-mortem autistic cerebellum by Abu-Elneel et al. in 2008. This finding validates these differentially expressed miRNAs in neurological tissue from a different cohort as well as supports the use of the lymphoblasts as a surrogate to study miRNA expression in ASD.

Conclusions

Findings from this study strongly suggest that dysregulation of miRNA expression contributes to the observed alterations in gene expression and, in turn, may lead to the pathophysiological conditions underlying autism.

The prodrome of autism: early behavioral and biological signs, regression, peri- and post-natal development and genetics

Autism is one of the most heritable neurodevelopmental conditions and has an early onset, with symptoms being required to be present in the first 3 years of life in order to meet criteria for the 'core' disorder in the classification systems. As such, the focus on identifying a prodrome over the past 20 years has been on pre-clinical signs or indicators that will be present very early in life, certainly in infancy. A number of novel lines of investigation have been used to this end, including retrospective coding of home videos, prospective population screening and 'high risk' sibling studies; as well as the investigation of pre- and peri-natal, brain developmental and other biological factors. While no single prodromal sign is expected to be present in all cases, a picture is emerging of indicative prodromal signs in infancy and initial studies are being undertaken to attempt to ameliorate early presentation and even 'prevent' emergence of the full syndrome.

Microduplications of 16p11.2 are associated with schizophrenia

Recurrent microdeletions and microduplications of a 600-kb genomic region of chromosome 16p11.2 have been implicated in childhood-onset developmental disorders. We report the association of 16p11.2 microduplications with schizophrenia in two large cohorts. The microduplication was detected in 12/1,906 (0.63%) cases and 1/3,971 (0.03%) controls (P = 1.2 x 10(-5), OR = 25.8) from the initial cohort, and in 9/2,645 (0.34%) cases and 1/2,420 (0.04%) controls (P = 0.022, OR = 8.3) of the replication cohort. The 16p11.2 microduplication was associated with a 14.5-fold increased risk of schizophrenia (95% CI (3.3, 62)) in the combined sample. A meta-analysis of datasets for multiple psychiatric disorders showed a significant association of the microduplication with schizophrenia (P = 4.8 x 10(-7)), bipolar disorder (P = 0.017) and autism (P = 1.9 x 10(-7)). In contrast, the reciprocal microdeletion was associated only with autism and developmental disorders (P = 2.3 x 10(-13)). Head circumference was larger in patients with the microdeletion than in patients with the microduplication (P = 0.0007).

Language and reading abilities of children with autism spectrum disorders and specific language impairment and their first-degree relatives

Autism spectrum disorder (ASD) and specific language impairment (SLI) are developmental disorders exhibiting language deficits, but it is unclear whether they arise from similar etiologies. Language impairments have been described in family members of children with ASD and SLI, but few studies have quantified them. In this study, we examined IQ, language, and reading abilities of ASD and SLI children and their first-degree relatives to address whether the language difficulties observed in some children with ASD are familial and to better understand the degree of overlap between these disorders and their broader phenotypes. Participants were 52 autistic children, 36 children with SLI, their siblings, and their parents. The ASD group was divided into those with (ALI, n=32) and without (ALN, n=20) language impairment. Relationships between ASD severity and language performance were also examined in the ASD probands. ALI and SLI probands performed similarly on most measures while ALN probands scored higher. ALN and ALI probands' language scores were not related to Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule algorithm scores. SLI relatives scored lowest on all measures, and while scores were not in the impaired range, relatives of ALI children scored lower than relatives of ALN children on some measures, though not those showing highest heritability in SLI. Given that ALI relatives performed better than SLI relatives across the language measures, the hypothesis that ALI and SLI families share similar genetic loading for language is not strongly supported.

Medical conditions in autism spectrum disorders

Autism spectrum disorder (ASD) is a behaviourally defined syndrome where the etiology and pathophysiology is only partially understood. In a small proportion of children with the condition, a specific medical disorder is identified, but the causal significance in many instances is unclear. Currently, the medical conditions that are best established as probable causes of ASD include Fragile X syndrome, Tuberous Sclerosis and abnormalities of chromosome 15 involving the 15q11-13 region. Various other single gene mutations, genetic syndromes, chromosomal abnormalities and rare de novo copy number variants have been reported as being possibly implicated in etiology, as have several ante and post natal exposures and complications. However, in most instances the evidence base for an association with ASD is very limited and largely derives from case reports or findings from small, highly selected and uncontrolled case series. Not only therefore, is there uncertainty over whether the condition is associated, but the potential basis for the association is very poorly understood. In some cases the medical condition may be a consequence of autism or simply represent an associated feature deriving from an underlying shared etiology. Nevertheless, it is clear that in a growing proportion of individuals potentially causal medical conditions are being identified and clarification of their role in etio-pathogenesis is necessary. Indeed, investigations into the causal mechanisms underlying the association between conditions such as tuberous sclerosis, Fragile X and chromosome 15 abnormalities are beginning to cast light on the molecular and neurobiological pathways involved in the pathophysiology of ASD. It is evident therefore, that much can be learnt from the study of probably causal medical disorders as they represent simpler and more tractable model systems in which to investigate causal mechanisms. Recent advances in genetics, molecular and systems biology and neuroscience now mean that there are unparalleled opportunities to test causal hypotheses and gain fundamental insights into the nature of autism and its development.

Accelerated head and body growth in infants later diagnosed with autism spectrum disorders: a comparative study of optimal outcome children

Previous research has demonstrated accelerated head and body growth during infancy in children with autism spectrum disorders. No study has yet examined head growth in children who lose their autism spectrum disorder diagnoses. Head circumference, length, and weight growth during infancy for 24 children who maintained their diagnoses were compared with 15 children who lost their diagnoses, and to 37 typically developing controls. Results showed that head circumference and weight growth were significantly greater in both autism spectrum disorder groups compared with controls, with no significant differences between autism spectrum disorder groups. However, when length and weight were controlled for, accelerated head growth remained significant in the children who lost their diagnoses. Findings suggest that children who lose their autism spectrum disorder diagnoses and children who maintain their diagnoses show similar head circumference, length, and weight growth trajectories during infancy, although subtle differences in body growth between groups may exist.

Regulation of cerebral cortical size and neuron number by fibroblast growth factors: implications for autism

Increased brain size is common in children with autism spectrum disorders. Here we propose that an increased number of cortical excitatory neurons may underlie the increased brain volume, minicolumn pathology and excessive network excitability, leading to sensory hyper-reactivity and seizures, which are often found in autism. We suggest that Fibroblast Growth Factors (FGF), a family of genes that regulate cortical size and connectivity, may be responsible for these developmental alterations. Studies in animal models suggest that mutations in FGF genes lead to altered cortical volume, excitatory cortical neuron number, minicolumn pathology, hyperactivity and social deficits. Thus, many risk factors may converge upon FGF-regulated pathogenetic pathways, which alter excitatory/inhibitory balance and cortical modular architecture, and predispose to autism spectrum disorders.

Autistic phenotypes and genetic testing: state-of-the-art for the clinical geneticist

Autism spectrum disorders represent a group of developmental disorders with strong genetic underpinnings. Several cytogenetic abnormalities or de novo mutations able to cause autism have recently been uncovered. In this study, the literature was reviewed to highlight genotype-phenotype correlations between causal gene mutations or cytogenetic abnormalities and behavioural or morphological phenotypes. Based on this information, a set of practical guidelines is proposed to help clinical geneticists pursue targeted genetic testing for patients with autism whose clinical phenotype is suggestive of a specific genetic or genomic aetiology.

Genetic disorders associated with macrocephaly

Macrocephaly is associated with many genetic disorders and is a frequent cause of referral to the clinical geneticist. In this review we classify the commonly encountered macrocephaly disorders into useful categories and summarize recent genetic advances. Conditions where macrocephaly is a predominant aspect of the clinical presentation are discussed and a diagnostic approach to the common macrocephaly disorders is provided. Some emphasis is placed on familial macrocephaly (sometimes referred to as benign external hydrocephalus) and on the macrocephaly associated with autism spectrum disorders. The more recent conditions associated with the leukodystrophies and the organic acidurias are reviewed, but the well known conditions involving storage disorders and bone dysplasias are mentioned but not discussed. The genetic macrocephaly conditions cover a broad spectrum of gene disorders and their related proteins have diverse biological functions. As of yet it is not clear what precise biological pathways lead to generalized brain overgrowth.

Quantitative magnetic resonance image analysis of the cerebellum in macrocephalic and normocephalic children and adults with autism

A detailed morphometric analysis of the cerebellum in autism with and without macrocephaly. Four subject groups (N = 65; male; IQs > or = 65; age 7 to 26 years) were studied with quantitative MRI; normocephalic and macrocephalic individuals with autism without mental retardation were compared to normocephalic and benign macrocephalic typically developing individuals. Total cerebellum volumes and surface areas of four lobular midsagittal groups were measured. Independent t-tests between autism and control subjects matched for head size revealed no significant differences. Multivariate analyses of variance were also performed, using the diagnostic group as the fixed factor, cerebellar measures as the dependent variables and total intracranial volume, total brain volume, age, verbal IQ, and performance IQ as covariates. No significant differences were found; however, a trend was noted in which macrocephalic individuals with autism consistently exhibited slightly smaller cerebellar volume or surface area when compared to individuals with benign macrocephaly. In autism, with and without macrocephaly, cerebellar structures were found to be proportional to head size and did not differ from typically developing subjects.

Growth-related neural reorganization and the autism phenotype: a test of the hypothesis that altered brain growth leads to altered connectivity

Theoretical considerations, and findings from computational modeling, comparative neuroanatomy and developmental neuroscience, motivate the hypothesis that a deviant brain growth trajectory will lead to deviant patterns of change in cortico-cortical connectivity. Differences in brain size during development will alter the relative cost and effectiveness of short- and long-distance connections, and should thus impact the growth and retention of connections. Reduced brain size should favor long-distance connectivity; brain overgrowth should favor short-distance connectivity; and inconsistent deviations from the normal growth trajectory - as occurs in autism - should result in potentially disruptive changes to established patterns of functional and physical connectivity during development. To explore this hypothesis, neural networks which modeled inter-hemispheric interaction were grown at the rate of either typically developing children or children with autism. The influence of the length of the inter-hemispheric connections was analyzed at multiple developmental time-points. The networks that modeled autistic growth were less affected by removal of the inter-hemispheric connections than those that modeled normal growth - indicating a reduced reliance on long-distance connections - for short response times, and this difference increased substantially at approximately 24 simulated months of age. The performance of the networks showed a corresponding decline during development. And direct analysis of the connection weights showed a parallel reduction in connectivity. These modeling results support the hypothesis that the deviant growth trajectory in autism spectrum disorders may lead to a disruption of established patterns of functional connectivity during development, with potentially negative behavioral consequences, and a subsequent reduction in physical connectivity. The results are discussed in relation to the growing body of evidence of reduced functional and structural connectivity in autism, and in relation to the behavioral phenotype, particularly the developmental aspects.

Early adolescent outcomes of institutionally deprived and non-deprived adoptees. III. Quasi-autism

BACKGROUND

Some young children reared in profoundly depriving institutions have been found to show autistic-like patterns, but the developmental significance of these features is unknown.

METHODS

A randomly selected, age-stratified, sample of 144 children who had experienced an institutional upbringing in Romania and who were adopted by UK families was studied at 4, 6, and 11 years, and compared with a non-institutionalised sample of 52 domestic adoptees. Twenty-eight children, all from Romanian institutions, for whom the possibility of quasi-autism had been raised, were assessed using the Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS) at the age of 12 years.

RESULTS

Sixteen children were found to have a quasi-autistic pattern; a rate of 9.2% in the Romanian institution-reared adoptees with an IQ of at least 50 as compared with 0% in the domestic adoptees. There were a further 12 children with some autistic-like features, but for whom the quasi-autism designation was not confirmed. The follow-up of the children showed that a quarter of the children lost their autistic-like features by 11. Disinhibited attachment and poor peer relationships were also present in over half of the children with quasi-autism.

CONCLUSIONS

The findings at age 11/12 years confirmed the reality and clinical significance of the quasi-autistic patterns seen in over 1 in 10 of the children who experienced profound institutional deprivation. Although there were important similarities with 'ordinary' autism, the dissimilarities suggest a different meaning.

Clinical, morphological, and biochemical correlates of head circumference in autism

BACKGROUND

Head growth rates are often accelerated in autism. This study is aimed at defining the clinical, morphological, and biochemical correlates of head circumference in autistic patients.

METHODS

Fronto-occipital head circumference was measured in 241 nonsyndromic autistic patients, 3 to 16 years old, diagnosed according to DSM-IV criteria. We assessed 1) clinical parameters using the Autism Diagnostic Observation Schedule, Autism Diagnostic Interview-Revised, Vineland Adaptive Behavioral Scales, intelligence quotient measures, and an ad hoc clinical history questionnaire; 2) height and weight; 3) serotonin (5-HT) blood levels and peptiduria.

RESULTS

The distribution of cranial circumference is significantly skewed toward larger head sizes (p < .00001). Macrocephaly (i.e., head circumference >97th percentile) is generally part of a broader macrosomic endophenotype, characterized by highly significant correlations between head circumference, weight, and height (p < .001). A head circumference >75th percentile is associated with more impaired adaptive behaviors and with less impairment in IQ measures and motor and verbal language development. Surprisingly, larger head sizes are significantly associated with a positive history of allergic/immune disorders both in the patient and in his/her first-degree relatives.

CONCLUSIONS

Our study demonstrates the existence of a macrosomic endophenotype in autism and points toward pathogenetic links with immune dysfunctions that we speculate either lead to or are associated with increased cell cycle progression and/or decreased apoptosis.

The neuropathology of autism

Autism is a brain disorder characterized by abnormalities in how a person relates and communicates to others. Both post-mortem and neuroimaging studies indicate the presence of increased brain volume and, in some cases, an altered gray/white matter ratio. Contrary to established gross findings there is no recognized microscopic pathology to autism. Early studies provided multiple leads none of which have been validated. Clinicopathological associations have been difficult to sustain when considering possible variables such as use of medications, seizures, mental retardation and agonal/pre-agonal conditions. Research findings suggest widespread cortical abnormalities, lack of a vascular component and an intact blood-brain barrier. Many of the previously mentioned findings can be explained in terms of a mini-columnopathy. The significance of future controlled studies should be judged based on their explanatory powers; that is, how well do they relate to brain growth abnormalities and/or provide useful clinicopathological correlates.

Rate of head circumference growth as a function of autism diagnosis and history of autistic regression

Several reports indicate that autism spectrum disorder is associated with increased rate of head growth in early childhood. Increased rate of growth may index aberrant processes during early development, may precede the onset of symptoms, and may predict severity of the disease course. We examined rate of change in occipitofrontal circumference measurements (abstracted from medical records) in 28 boys with autism spectrum disorder and in 8 boys with developmental delay without autism from birth to age 36 months. Only children who had more than 3 occipitofrontal circumference measurements available during this age period were included. All data were converted to z scores based on the Centers for Disease Control and Prevention norms. Rate of growth from birth to age 36 months was statistically significantly higher for the autism spectrum disorder group than the developmental delay group, with children with autism spectrum disorder showing a statistically significant increase in occipitofrontal circumference relative to norms between 7 and 10 months; this group difference in rate of growth was more robust when height was used as a covariate. Rate of growth was not found to be different for children with autism spectrum disorder whose parents reported a history of loss of skills (regression) vs those whose parents reported early onset of autism symptoms. Findings from this study suggest that the aberrant growth is present in the first year of life and precedes the onset and diagnosis in children with autism spectrum disorder with and without a history of autistic regression.

A neurobehavioral examination of individuals with high-functioning autism and Asperger's disorder using a fronto-striatal model of dysfunction

The repetitive, stereotyped, and obsessive behaviors that characterize autism may in part be attributable to disruption of the region of the fronto-striatal system, which mediates executive abilities. Neuropsychological testing has shown that children with autism exhibit set-shifting deficiencies on tests such as the Wisconsin Card Sorting task but show normal inhibitory ability on variants of the Stroop color-word test. According to Minshew and Goldstein's multiple primary deficit theory, the complexity of the executive functioning task is important in determining the performance of individuals with autism. This study employed a visual-spatial task (with a Stroop-type component) to examine the integrity of executive functioning, in particular inhibition, in autism (n = 12) and Asperger's disorder (n = 12) under increasing levels of cognitive complexity. Whereas the Asperger's disorder group performed similarly to age- and IQ-matched control participants, even at the higher levels of cognitive complexity, the high-functioning autism group displayed inhibitory deficits specifically associated with increasing cognitive load.

Growth of Head Circumference in Autistic Infants During the First Year of Life

This study analyzed the increase in head circumference (HC) of 85 autistic infants (64 boys and 21 girls) during their first year of life. The data were collected from their "mother-and-baby" notebooks. This notebook is a medical record of the baby's growth and development delivered to the parents of all babies born in Japan. This is a retrospective study which gathered the data from the notebooks after the diagnosis of autism. However, none of the babies were known to have autism at the time the records were made. The head circumference at birth of these autistic children was similar to that of the average found in a Japanese Government Study of 14,115 children. However, it showed a marked increase at 1 month after birth. The discrepancy reached a peak at 6 months, while the difference became smaller at 12 months. Body length (BL) and body weight (BW) began to increase at 3 months, although at a rate smaller than the head circumference increase.

Brain abnormalities in language disorders and in autism

It has been speculated that autism and specific language impairment share common underlying neural substrates because of the overlap in language impairment issues and evidence suggesting parallels in other domains and implying a possible shared genetic risk. Anatomically the two sets of disorders have generally been studied using different methodologies, but when identical methodologies have been used substantial similarities have been noted. Functionally there is a growing body of literature suggesting sensory perception abnormalities that have parallels in both conditions and that may be upstream of language abnormalities. Finding upstream mechanisms that impact language and non-language abnormalities in autism and specific language impairment would impact the orientation taken by translational attempts to use science to design treatments.

Correlates of head circumference growth in infants later diagnosed with autism spectrum disorders

Previous research has demonstrated that children diagnosed with autism spectrum disorder show an abnormal acceleration of head growth during the first year of life. This study attempts to replicate these findings and to determine whether overgrowth is associated with clinical outcome. Measurements of head circumference, body length, and body weight taken during the first 2 years of life were obtained from a sample of 35 children diagnosed with autism spectrum disorder and compared to both national normative data (Centers for Disease Control and Prevention) and a control group of 37 healthy infants. Results demonstrated that compared to national averages, infants who were later diagnosed with autism spectrum disorder had a significantly smaller head circumference at birth to 2 weeks and a significantly larger head circumference by 10 to 14 months. Children with autism spectrum disorder were also significantly longer and heavier beginning at 1 to 2 months. However, when overall length and weight were controlled, head circumference was not bigger in the autistic spectrum disorder group compared to local controls. Correlations between head circumference and clinical outcome were significant for 5 of the 30 clinical variables that were run, suggesting that there appears to be no simple or straightforward relationship between head circumference and clinical outcome. Smaller head circumference at birth to 2 weeks was associated with a greater number of symptoms related to social impairment and a greater total number of autism spectrum disorder symptoms based on the Diagnostic and Statistical Manual of Mental Disorders , Fourth Edition criteria. Larger head circumference at 15 to 25 months was also associated with a greater number of symptoms of social impairment. In addition, greater head circumference change during the first 2 years was associated with poorer performance on the visual reception subtest of the Mullen Scales of Early Learning and a smaller number of stereotyped and repetitive behaviors and interests based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria. These findings support previous findings of accelerated brain growth during the first year of life in autism spectrum disorder and question whether growth factors might contribute to both accelerated brain growth and overall body growth.

HOXA1 gene variants influence head growth rates in humans

We previously described a significant association between the HOXA1 G218 allele and increased head circumference in autism [Conciatori et al. (2004); Biol Psychiatry 55:413-419]. The present study reveals identical effects also in normal children. HOXA1 A218G alleles and sex explain as much as 10.9 and 6.8% of the variance in head circumference in 142 pediatric controls and in 191 autistic children, aged 3-16 years (F = 6.777, 3 and 141 df, P < 0.001 and F = 5.588, 3 and 190 df, P < 0.01, respectively). Instead, no association is found in 183 adult controls and in 35 pediatric fragile-X patients. Therefore HOXA1 A218G alleles significantly influence head growth rates, but not final head size, in normal human development. This influence does not differ between normal and autistic children, whereas the lack of FMRP seemingly overwhelms HOXA1 effects in fragile-X patients.

Head circumference and height in autism: a study by the Collaborative Program of Excellence in Autism

Data from 10 sites of the NICHD/NIDCD Collaborative Programs of Excellence in Autism were combined to study the distribution of head circumference and relationship to demographic and clinical variables. Three hundred thirty-eight probands with autism-spectrum disorder (ASD) including 208 probands with autism were studied along with 147 parents, 149 siblings, and typically developing controls. ASDs were diagnosed, and head circumference and clinical variables measured in a standardized manner across all sites. All subjects with autism met ADI-R, ADOS-G, DSM-IV, and ICD-10 criteria. The results show the distribution of standardized head circumference in autism is normal in shape, and the mean, variance, and rate of macrocephaly but not microcephaly are increased. Head circumference tends to be large relative to height in autism. No site, gender, age, SES, verbal, or non-verbal IQ effects were present in the autism sample. In addition to autism itself, standardized height and average parental head circumference were the most important factors predicting head circumference in individuals with autism. Mean standardized head circumference and rates of macrocephaly were similar in probands with autism and their parents. Increased head circumference was associated with a higher (more severe) ADI-R social algorithm score. Macrocephaly is associated with delayed onset of language. Although mean head circumference and rates of macrocephaly are increased in autism, a high degree of variability is present, underscoring the complex clinical heterogeneity of the disorder. The wide distribution of head circumference in autism has major implications for genetic, neuroimaging, and other neurobiological research.

Growth in stature and head circumference in high-functioning autism and Asperger disorder during the first 3 years of life

Little effort has been made to characterize the developmental anatomic phenotype of autism; although there is evidence of an increased head circumference and brain size, few other physical characteristics have been studied. The head circumference, body length/height, and weight measurements of infants, who were later diagnosed with high-functioning autism (HFA, n = 16) and Asperger disorder (AsD, n = 12), were extracted from health records over the first 3 years of life and compared to the measurements of a matched normal control group (n = 19). Using linear mixed-effects models, no differences were found in the average growth rate for head circumference, stature, or weight between the children with HFA and AsD. However, a significantly higher growth rate in body length/height and weight was found for the combined group of children with HFA and AsD compared to the normal control group. A trend toward higher growth rate in head circumference was also found among the former group. The results indicate that growth dysregulation in autism is not specific to the brain but also involves growth in stature.

Neuropathological and genetic findings in autism: the significance of a putative minicolumnopathy

Autism is a condition manifested as abnormalities of relatedness, communication, range of interests, and repetitive behaviors. Despite alarming prevalence estimates and exhortations to research, little is known regarding its pathophysiology. Recent reports of a putative minicolumnopathy explain changes in brain size, gray/white matter ratios, and interareal connectivity. This article summarizes possible links between minicolumns and other topics-cortical modularity, age of onset, gliosis, and genetics-relevant to the pathophysiology of autism.

Altered Neocortical Cell Density and Layer Thickness in Serotonin Transporter Knockout Mice: A Quantitation Study

The neurotransmitter serotonin (5-HT) plays morphogenetic roles during development, and their alteration could contribute to autism pathogenesis in humans. To further characterize 5-HT's contributions to neocortical development, we assessed the thickness and neuronal cell density of various cerebral cortical areas in serotonin transporter (5-HTT) knockout (ko) mice, characterized by elevated extracellular 5-HT levels. The thickness of layer IV is decreased in 5-HTT ko mice compared with wild-type (wt) mice. The overall effect on cortical thickness, however, depends on the genetic background of the mice. Overall cortical thickness is decreased in many cortical areas of 5-HTT ko mice with a mixed c129-CD1-C57BL/6J background. Instead, 5-HTT ko mice backcrossed into the C57BL/6J background display increases in supragranular and infragranular layers, which compensate entirely for decreased layer IV thickness, resulting in unchanged or even enhanced cortical thickness. Moreover, significant increases in neuronal cell density are found in 5-HTT ko mice with a C57BL/6J background (wt:hz:ko ratio = 1.00:1.04:1.17) but not in the mixed c129-CD1-C57BL/6J 5-HTT ko animals. These results provide evidence of 5-HTT gene effects on neocortical morphology in epistatic interaction with genetic variants at other loci and may model the effect of functional 5-HTT gene variants on neocortical development in autism.

Adjustment for whole brain and cranial size in volumetric brain studies: a review of common adjustment factors and statistical methods

In this article we address analytic challenges inherent in brain volumetrics (i.e., the study of volumes of brains and brain regions). It has sometimes been assumed in the literature that deviations in regional brain size in clinical samples are directly related to maldevelopment or pathogenesis. However, this assumption may be incorrect; such volume differences may, instead, be wholly or partly attributable to individual differences in overall dimension (e.g., for head, brain, or body size). What quantitative approaches can be used to take these factors into account? Here, we provide a review of volumetric and nonvolumetric adjustment factors. We consider three examples of common statistical methods by which one can adjust for the effects of body, head, or brain size on regional volumetric measures: the analysis of covariance, the proportion, and the residual approaches. While the nature of the adjustment will help dictate which method is most appropriate, the choice is context sensitive, guided by numerous considerations-chiefly the experimental hypotheses, but other factors as well (including characteristic features of the disorder and sample size). These issues come into play in logically framing the assessment of putative abnormalities in regional brain volumes.