Mitochondrial and ion channel gene alterations in autism.

To evaluate the potential importance in autistic subjects of copy number variants (CNVs) that alter genes of relevance to bioenergetics, ionic metabolism, and synaptic function, we conducted a detailed microarray analysis of 69 autism probands and 35 parents, compared to 89 CEU HapMap controls. This revealed that the frequency CNVs of≥100kb and CNVs of≥10 Kb were markedly increased in probands over parents and in probands and parents over controls. Evaluation of CNVs≥1Mb by chromosomal FISH confirmed the molecular identity of a subset of the CNVs, some of which were associated with chromosomal rearrangements. In a number of the cases, CNVs were found to alter the copy number of genes that are important in mitochondrial oxidative phosphorylation (OXPHOS), ion and especially calcium transport, and synaptic structure. Hence, autism might result from alterations in multiple bioenergetic and metabolic genes required for mental function. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).

Genotypic and phenotypic analysis of 396 individuals with mutations in Sonic Hedgehog.

BACKGROUND: Holoprosencephaly (HPE), the most common malformation of the human forebrain, may result from mutations in over 12 genes. Sonic Hedgehog (SHH) was the first such gene discovered; mutations in SHH remain the most common cause of non-chromosomal HPE. The severity spectrum is wide, ranging from incompatibility with extrauterine life to isolated midline facial differences. OBJECTIVE: To characterise genetic and clinical findings in individuals with SHH mutations. METHODS: Through the National Institutes of Health and collaborating centres, DNA from approximately 2000 individuals with HPE spectrum disorders were analysed for SHH variations. Clinical details were examined and combined with published cases. RESULTS: This study describes 396 individuals, representing 157 unrelated kindreds, with SHH mutations; 141 (36%) have not been previously reported. SHH mutations more commonly resulted in non-HPE (64%) than frank HPE (36%), and non-HPE was significantly more common in patients with SHH than in those with mutations in the other common HPE related genes (p<0.0001 compared to ZIC2 or SIX3). Individuals with truncating mutations were significantly more likely to have frank HPE than those with non-truncating mutations (49% vs 35%, respectively; p=0.012). While mutations were significantly more common in the N-terminus than in the C-terminus (including accounting for the relative size of the coding regions, p=0.00010), no specific genotype-phenotype correlations could be established regarding mutation location. CONCLUSIONS: SHH mutations overall result in milder disease than mutations in other common HPE related genes. HPE is more frequent in individuals with truncating mutations, but clinical predictions at the individual level remain elusive.

Does theory of mind performance differ in children with early-onset and regressive autism?

A deficit in theory of mind (ToM), or the ability to infer the mental states of others, has been implicated as one of the major characteristics of Autism Spectrum Disorder (ASD); however, little attention has been devoted to possible differences in ToM ability within ASD. The current study examined ToM performance in children with early-onset autism and regressive autism in comparison to typically developing children. Results indicated that children in the regressive autism group performed significantly better than the early-onset autism group on the non-verbal appearance-reality task. Additionally, Fisher's exact tests indicated a pattern of lowest scores in the early-onset group and highest scores in the typically developing group, whereas the regressive autism group tended to score in between the early-onset and typically developing groups. The apparent heterogeneity in ToM performance within ASD could account for the lack of universality in ToM ability found in previous studies.

The effect of rate stress on the auditory brainstem response in autism: a preliminary report.

Efforts to correlate peripheral neurophysiologic function with perceptional deficits seen in autistic disorder (AD) have resulted in mixed findings, reflecting the high degree of heterogeneity observed in these individuals. We used the auditory brainstem response to study the effect of stress (high click presentation rate) on the auditory system in 20 children with AD (7-13 years) and 20 age-matched typically developing (TD) children. We report latency prolongations in children with AD vs. TD at waves I, III, and V that differed by ear of presentation: overall, left ear showed significant prolongations by group while right ear did not. The 'stressed' condition produced prolongations for both groups at each wave. At wave V, children with AD showed significant prolongations vs. TD, particularly for the right ear. For children with AD, wave V latency prolongations corresponded to language outcome as measured by VIQ, with longer prolongations associating with lower VIQ. Preliminary results provide evidence for reduced synaptic efficiency in auditory pathways in children with AD, which may form the neural bases for sensory reactivity and language impairment.

Development and validation of a measure of dysmorphology: useful for autism subgroup classification.

Autism spectrum disorders (ASD) comprise a class of neurodevelopmental disorders that can originate from a variety of genetic and environmental causes. To delineate autism's heterogeneity we have looked for biologically-based phenotypes found in consistent proportions of ASD individuals. One informative phenotype is that of generalized dysmorphology, based on whole body examinations by medical geneticists trained in the nuances of anomalous embryologic development. We identified a need for a dysmorphology measure that could be completed by medical clinicians not extensively trained in dysmorphology that would still retain the level of sensitivity and specificity of the comprehensive dysmorphology examination. Based on expert-derived consensus dysmorphology designation of 222 autism patients and a classification validation study of 30 subjects by four dysmorphologists, we determined that dysmorphology designations based on body areas provided superior inter-rater reliability. Using 34 body area designations, we performed a classification and regression tree (CART) analysis to construct a scoring algorithm. Compared to the consensus classification, the model performed with 81% sensitivity and 99% specificity, and classification of a replication dataset of 31 ASD individuals performed well, with 82% sensitivity and 95% specificity. The autism dysmorphology measure (ADM) directs the clinician to score 12 body areas sequentially to arrive at a determination of "dysmorphic" or "nondysmorphic." We anticipate the ADM will permit clinicians to differentiate accurately between dysmorphic and nondysmorphic individuals-allowing better diagnostic classification, prognostication, recurrence risk assessment, and laboratory analysis decisions-and research scientists to better define more homogeneous autism subtypes.

Clinical variability of autosomal dominant cataract, microcornea and corneal opacity and novel mutation in the alpha A crystallin gene (CRYAA).

We studied 28 individuals from a four-generation Chilean family (ADC54) including 13 affected individuals with cataracts, microcornea and/or corneal opacity. All individuals underwent a complete ophthalmologic exam. We screened with a panel of polymorphic DNA markers for known loci that cause autosomal dominant cataracts, if mutated, and refined the locus using the ABI Prism Linkage Mapping Set Version 2.5, and calculated two-point lod scores. Novel PCR primers were designed for the three coding exons, including intron-exon borders, of the candidate gene alpha A crystallin (CRYAA). Clinically, affected individuals had diverse and novel cataracts with variable morphology (anterior polar, cortical, embryonal, fan-shaped, anterior subcapsular). Microcornea and corneal opacity was evident in some. Marker D21S171 gave a lod score of 4.89 (theta(m) = theta(f) = 0). CRYAA had a G414A transition that segregated with the disease and resulted in an amino acid alteration (R116H). The phenotypic variability within this family was significant with novel features of the cataracts and a corneal opacity. With the exception of iris coloboma, the clinical features in all six previously reported families with mutations in the CRYAA gene were found in this family. We identified a novel G414A transition in exon 3 of CRYAA that co-segregated with an autosomal dominant phenotype. The resulting amino acid change R116H is in a highly conserved region and represents a change in charge. The genotype-phenotype correlation of this previously unreported mutation provides evidence that other factors, genetic and/or environmental, may influence the development of cataract as a result of this alteration.

Use of home videotapes to confirm parental reports of regression in autism.

The current study examined consistency between parental reports on early language development and behaviors in non-language domains and observer-coded videotapes of young children with and without autism spectrum disorder (ASD) and autistic regression. Data are reported on 56 children (84% male) with ASD (early onset or autistic regression) and 14 typically developing children (57% male) who had home videotapes. Unique to the current study is the independent identification of loss/no loss for each child by both parental report and observer-coded home videotapes and the examination of agreement between these two methods. Results indicate substantial concordance between parental report and observer codes for onset and loss of expressive language, but minimal concordance for loss in non-language domains, suggesting a need for supplementation of parental reports in these areas.

Birthday and non-birthday videotapes: the importance of context for the behavior of young children with autism.

The present study examines whether children display different frequencies of behaviors at birthday party as compared to non-birthday party settings, and elucidates in which setting behavior is more predictive of later child functioning. Behavior in birthday and non-birthday contexts was examined at 12 and 24 months of age for 56 children with autism spectrum disorder (ASD). The results of this study indicate that context does matter for young children's behavior and leads to a different picture of behavioral functioning. For children with ASD, behaviors from non-birthday videotapes are more predictive of functioning later in childhood. The findings suggest that close attention must be paid to contextual factors that may influence young children's behavior.

Endothelial function and urine albumin levels among asymptomatic Mexican-Americans and non-Hispanic whites.

BACKGROUND: Mexican-Americans (MA) exhibit increases in various cardiovascular disease (CVD) risk factors compared to non-Hispanic Whites (NHW), yet are reported to have lower CVD mortality rates. Our aim was to help explain this apparent paradox by evaluating endothelial function and urine albumin levels in MA and NHW. METHODS: One hundred-five MA and 100 NHW adults were studied by brachial artery flow-mediated dilatation (FMD), blood and urine tests. Participants were studied by ultrasound-determined brachial artery flow-mediated dilatation (FMD), blood and urine tests, at a single visit. RESULTS: Despite higher BMI and triglycerides in MA, MA demonstrated higher FMD than did NHW (9.1 +/- 7.3% vs. 7.1 +/- 6.3%, p < 0.04). Among MA, urinary albumin was consistently lower in participants with FMD >or= 7% FMD versus < 7% FMD (p < 0.006). In multivariate analyses in MA men, urinary albumin was inversely related to FMD (r = -0.26, p < 0.05), as were BMI and systolic blood pressure. In MA women, urinary albumin:creatinine ratio was an independent inverse predictor of FMD (p < 0.05 ). CONCLUSION: To our knowledge, this is the first study to analyze, in asymptomatic adults, the relation of MA and NHW ethnicity to FMD and urine albumin levels. The findings confirm ethnic differences in these important subclinical CVD measures.

Gene conversion mutation in crystallin, beta-B2 (CRYBB2) in a Chilean family with autosomal dominant cataract.

PURPOSE: To map and identify the mutated gene for autosomal dominant cataract (ADC) in a large Chilean family (ADC53). DESIGN: Experimental study. PARTICIPANTS: Large Chilean family with ADCs. METHODS: Linkage analyses using genome-wide polymorphic DNA markers were performed on a family with variable expression of cataracts to map the mutated gene to a chromosome; 2-point lod scores were calculated. Candidate genes in the region of the maximum lod score were sequenced. We compared haplotypes (alleles at closely linked markers) in families with previously reported mutations of the crystallin, beta-B2 gene (CRYBB2). MAIN OUTCOME MEASURES: Identification of the causative mutation in the ADC53 family. RESULTS: The ADC locus mapped to chromosome 22 in the region of a cluster of lens beta crystallin genes (CRYBB3, CRYBB2, CRYBB1, and CRYBA4 and the pseudogene CRYBB2P1). We sequenced CRYBB1 and CRYBB2 and found a previously reported mutation and a variant in exon 6 of CRYBB2 that cosegregate with the disease; these changes in CRYBB2 are in the reference (normal) sequence of an adjacent gene CRYBB2P1, a pseudogene. The haplotypes in the ADC53 Chilean family were different from the 2 previously reported families with the mutation. CONCLUSIONS: The cataracts in the ADC53 Chilean family are caused by a mutation in the CRYBB2 gene; as the 2 variations in CRYBB2 are identical to the reference sequence of pseudogene CRYBB2P1, which has over 97% homology to CRYBB2, a gene conversion probably has occurred. Based on haplotype analyses, the mutation and variant are likely to be caused by independent gene conversions in our family and the previously reported families.

A new locus for autosomal dominant cataract on chromosome 19: linkage analyses and screening of candidate genes.

PURPOSE: To map and identify the mutated gene for autosomal dominant cataract (ADC) in family ADC4. METHODS: Ophthalmic evaluations were performed on an American family with ADC and a panel of polymorphic DNA sequence-tagged site (STS) markers for known ADC loci and other genome-wide polymorphic markers were used to map the gene; two-point lod scores were calculated. Fine mapping was undertaken in the chromosomal regions of maximum lod scores, and candidate genes were sequenced. RESULTS: A four-generation American family with ADC was studied. The only phakic individual exhibited white and vacuolated opacities in the cortical region. This ADC locus mapped to several suggestive chromosomal regions. Assuming full penetrance, the highest calculated maximum lod score was 3.91 with D19S903 [corrected] On chromosome 12, we sequenced all exons and the exon-intron borders of the membrane intrinsic protein (MIP) gene. On chromosome 19, all exons and the exon-intron borders of genes for lens intrinsic membrane2 (LIM2), ferritin light chain (FTL), and the human homologue of the Drosophila sine oculis homeobox 5 (SIX5) were sequenced, and the 3' untranslated repeat region (UTR) of the dystrophy (DMPK) gene and both the 5' and 3' UTRs of the SIX5 genes were amplified; the promoter for LIM2 was sequenced. For these genes, the sequence matched that in the reference libraries, and the DMPK gene had a normal number of CTG repeats. CONCLUSIONS: The mutated gene in ADC4 probably represents a new, not yet identified locus on chromosome 19. In one phakic member, the cortical cataracts were punctate and vacuolated.

Novel single-base deletional mutation in major intrinsic protein (MIP) in autosomal dominant cataract.

PURPOSE: To further elucidate the cataract phenotype, and identify the gene and mutation for autosomal dominant cataract (ADC) in an American family of European descent (ADC2) by sequencing the major intrinsic protein gene (MIP), a candidate based on linkage to chromosome 12q13. DESIGN: Observational case series and laboratory experimental study. METHODS: We examined two at-risk individuals in ADC2. We PCR-amplified and sequenced all four exons and all intron-exon boundaries of the MIP gene from genomic and cloned DNA in affected members to confirm one variant as the putative mutation. RESULTS: We found a novel single deletion of nucleotide (nt) 3223 (within codon 235) in exon four, causing a frameshift that alters 41 of 45 subsequent amino acids and creates a premature stop codon. CONCLUSIONS: We identified a novel single base pair deletion in the MIP gene and conclude that it is a pathogenic sequence alteration.

Is there a 'regressive phenotype' of Autism Spectrum Disorder associated with the measles-mumps-rubella vaccine? A CPEA Study.

A multi-site study of 351 children with Autism Spectrum Disorders (ASD) and 31 typically developing children used caregiver interviews to describe the children's early acquisition and loss of social-communication milestones. For the majority of children with ASD who had experienced a regression, pre-loss development was clearly atypical. Children who had lost skills also showed slightly poorer outcomes in verbal IQ and social reciprocity, a later mean age of onset of autistic symptoms, and more gastrointestinal symptoms than children with ASD and no regression. There was no evidence that onset of autistic symptoms or of regression was related to measles-mumps-rubella vaccination. The implications of these findings for the existence of a 'regressive phenotype' of ASD are discussed.

Familial autoimmune thyroid disease as a risk factor for regression in children with Autism Spectrum Disorder: a CPEA Study.

A multicenter study of 308 children with Autism Spectrum Disorder (ASD) was conducted through the Collaborative Programs of Excellence in Autism (CPEA), sponsored by the National Institute of Child Health and Human Development, to compare the family history of autoimmune disorders in children with ASD with and without a history of regression. A history of regression was determined from the results of the Autism Diagnostic Interview-Revised (ADI-R). Family history of autoimmune disorders was obtained by telephone interview. Regression was significantly associated with a family history of autoimmune disorders (adjusted OR=1.89; 95% CI: 1.17, 3.10). The only specific autoimmune disorder found to be associated with regression was autoimmune thyroid disease (adjusted OR=2.09; 95% CI: 1.28, 3.41).

Association between amygdala volume and anxiety level: magnetic resonance imaging (MRI) study in autistic children.

Our objective was to evaluate brain-behavior relationships between amygdala volume and anxious/depressed scores on the Child Behavior Checklist in a well-characterized population of autistic children. Volumes for the amygdala, hippocampus, and whole brain were obtained from three-dimensional magnetic resonance images (MRIs) captured from 42 children who met the criteria for autistic disorder. Anxious/depressed symptoms were assessed in these children by the Anxious/Depressed subscale of the Child Behavior Checklist. To investigate the association between anxious/depressed scores on the Child Behavior Checklist and amygdala volume, data were analyzed using linear regression methods with Pearson correlation coefficients. A multivariate model was used to adjust for potential covariates associated with amygdala volume, including age at MRI and total brain size. We found that anxious/depressed symptoms were significantly correlated with increased total amygdala volume (r = .386, P = .012) and right amygdala volume (r = .469, P = .002). The correlation between anxious/depressed symptoms and left amygdala volume did not reach statistical significance (r = .249, P = .112). Child Behavior Checklist anxious/depressed scores were found to be a significant predictor of amygdala total (P = .014) and right amygdala (P = .002) volumes. In conclusion, we have identified a significant brain-behavior relationship between amygdala volume and anxious/depressed scores on the Child Behavior Checklist in our autistic cohort. This specific relationship has not been reported in autism. However, the existing literature on human psychiatry and behavior supports our reported evidence for a neurobiologic relationship between symptoms of anxiety and depression with amygdala structure and function. Our results highlight the importance of characterizing comorbid psychiatric symptomatology in autism. The abundance of inconsistent findings in the published literature on autism might reflect differences between study populations regarding age at MRI, level of impairment within autistic subjects, and underlying anxiety level in the selected study groups.

Performance comparison of two-point linkage methods using microsatellite markers flanking known disease locations.

The Genetic Analysis Workshop 14 simulated data presents an interesting, challenging, and plausible example of a complex disease interaction in a dataset. This paper summarizes the ease of detection for each of the simulated Kofendrerd Personality Disorder (KPD) genes across all of the replicates for five standard linkage statistics. Using the KPD affection status, we have analyzed the microsatellite markers flanking each of the disease genes, plus an additional 2 markers that were not linked to any of the disease loci. All markers were analyzed using the following two-point linkage methods: 1) a MMLS, which is a standard admixture LOD score maximized over theta, alpha, and mode of inheritance, 2) a MLS calculated by GENEHUNTER, 3) the Kong and Cox LOD score as computed by MERLIN, 4) a MOD score (standard heterogeneity LOD maximized over theta, alpha, and a grid of genetic model parameters), and 5) the PPL, a Bayesian statistic that directly measures the strength of evidence for linkage to a marker. All of the major loci (D1-D4) were detectable with varying probabilities in the different populations. However, the modifier genes (D5 and D6) were difficult to detect, with similar distributions under the null and alternative across populations and statistics. The pooling of the four datasets in each replicate (n = 350 pedigrees) greatly improved the chance of detecting the major genes using all five methods, but failed to increase the chance to detect D5 and D6.

Early regression in social communication in autism spectrum disorders: a CPEA Study.

In a multisite study of 351 children with autism spectrum disorders, 21 children with developmental delays, and 31 children with typical development, this study used caregiver interviews (i.e., the Autism Diagnostic Interview-Revised) at the time of entry into other research projects and follow-up telephone interviews designed for this project to describe the children's early acquisition and loss of social-communication milestones. Children who had used words spontaneously and meaningfully and then stopped talking were described by their caregivers as showing more gestures, greater participation in social games, and better receptive language before the loss and fewer of these skills after the loss than other children with autism spectrum disorders. A significant minority of children with autism without word loss showed a very similar pattern of loss of social-communication skills, a pattern not observed in the children with developmental delays or typical development.

Brief report: early social communication behaviors in the younger siblings of children with autism.

The early social and communicative development of very young siblings of children with autism spectrum disorder (ASD) is the focus of the current study. Three groups of children were included: (1) young children diagnosed with ASD, (2) younger siblings in families with a somewhat older child with ASD, and (3) young typically developing children. All children participated in a videotaped, structured interactional procedure called the Early Social Communication Scales (ESCS; [Mundy & Hogan, 1996, A Preliminary Manual for the Abridged Early Social Communication Scales (ESCS) Unpublished manual, University of Miami]). Very young siblings were compared to young children with a diagnosed autism spectrum disorder and to a group of young typically developing children. Results indicated that, on three of four of the ESCS subscales, the social communicative behaviors of the younger siblings differed from those of the typically developing children but not from the behaviors displayed by the ASD group. Genetic vulnerability for ASD among siblings and characteristics of family interaction may explain the level of impairment observed in the very young siblings of children with autism spectrum disorders.

A case of autism with an interstitial deletion on 4q leading to hemizygosity for genes encoding for glutamine and glycine neurotransmitter receptor sub-units (AMPA 2, GLRA3, GLRB) and neuropeptide receptors NPY1R, NPY5R.

BACKGROUND: Autism is a pervasive developmental disorder characterized by a triad of deficits: qualitative impairments in social interactions, communication deficits, and repetitive and stereotyped patterns of behavior. Although autism is etiologically heterogeneous, family and twin studies have established a definite genetic basis. The inheritance of idiopathic autism is presumed to be complex, with many genes involved; environmental factors are also possibly contributory. The analysis of chromosome abnormalities associated with autism contributes greatly to the identification of autism candidate genes. CASE PRESENTATION: We describe a child with autistic disorder and an interstitial deletion on chromosome 4q. This child first presented at 12 months of age with developmental delay and minor dysmorphic features. At 4 years of age a diagnosis of Pervasive Developmental Disorder was made. At 11 years of age he met diagnostic criteria for autism. Cytogenetic studies revealed a chromosome 4q deletion. The karyotype was 46, XY del 4 (q31.3-q33). Here we report the clinical phenotype of the child and the molecular characterization of the deletion using molecular cytogenetic techniques and analysis of polymorphic markers. These studies revealed a 19 megabase deletion spanning 4q32 to 4q34. Analysis of existing polymorphic markers and new markers developed in this study revealed that the deletion arose on a paternally derived chromosome. To date 33 genes of known or inferred function are deleted as a consequence of the deletion. Among these are the AMPA 2 gene that encodes the glutamate receptor GluR2 sub-unit, GLRA3 and GLRB genes that encode glycine receptor subunits and neuropeptide Y receptor genes NPY1R and NPY5R. CONCLUSIONS: The deletion in this autistic subject serves to highlight specific autism candidate genes. He is hemizygous for AMPA 2, GLRA3, GLRB, NPY1R and NPY5R. GluR2 is the major determinant of AMPA receptor structure. Glutamate receptors maintain structural and functional plasticity of synapses. Neuropeptide Y and its receptors NPY1R and NPY5R play a role in hippocampal learning and memory. Glycine receptors are expressed in very early cortical development. Molecular cytogenetic studies and DNA sequence analysis in other patients with autism will be necessary to confirm that these genes are involved in autism.