DRD2 and PPP1R1B (DARPP-32) polymorphisms independently confer increased risk for autism spectrum disorders and additively predict affected status in male-only affected sib-pair families.

Background: The neurotransmitter dopamine (DA) modulates executive functions, learning, and emotional processing, all of which are impaired in individuals with autism spectrum disorders (ASDs). Our previous findings suggest a role for dopamine-related genes in families with only affected males.

Methods: We examined two additional genes which affect DA function, the DRD2 and PPP1R1B (DARPP-32) genes, in a cohort of 112 male-only affected sib-pair families.

Developmental trajectories in syndromes with intellectual disability, with a focus on Wolf-Hirschhorn and its cognitive-behavioral profile.

Few studies exist of developmental trajectories in children with intellectual disability, and none for those with subtelomeric deletions. We compared developmental trajectories of children with Wolf-Hirschhorn syndrome to other genetic disorders. We recruited 106 children diagnosed with fragile X, Williams-Beuren syndrome, or Wolf-Hirschhorn syndrome, assessing their intellectual and adaptive behavior abilities.

Dopamine receptor D4 gene variation predicts preschoolers' developing theory of mind.

Individual differences in preschoolers' understanding that human action is caused by internal mental states, or representational theory of mind (RTM), are heritable, as are developmental disorders such as autism in which RTM is particularly impaired. We investigated whether polymorphisms of genes affecting dopamine (DA) utilization and metabolism constitute part of the molecular basis of this heritability. Seventy-three 42- to 54-month-olds were given a battery of RTM tasks along with other task batteries that measured executive functioning and representational understanding more generally.

Association of GTF2i in the Williams-Beuren syndrome critical region with autism spectrum disorders.

Duplications of 7q11.23, deleted in Williams-Beuren Syndrome, have been implicated in autism spectrum disorders (ASDs). A 1.

2p15-p16.1 microdeletion syndrome: molecular characterization and association of the OTX1 and XPO1 genes with autism spectrum disorders.

Reports of unrelated individuals with autism spectrum disorder (ASD) and similar clinical features having overlapping de novo interstitial deletions at 2p15-p16.1 suggest that this region harbors a gene(s) important to the development of autism. We molecularly characterized two such deletions, selecting two genes in this region, exportin 1 (XPO1) and orthodenticle homolog 1 (OTX1) for association studies in three North American cohorts (Autism Spectrum Disorder - Canadian American Research Consortium (ASD-CARC), New York, and Autism Genetic Resource Exchange (AGRE)) and one Italian cohort (Società Italiana per la Ricerca e la Formazione sull'Autismo (SIRFA)) of families with ASD.

Development and initial validation of a parent report measure of the behavioral development of infants at risk for autism spectrum disorders.

We developed and evaluated a new parent report instrument--Parent Observation of Early Markers Scale (POEMS)--to monitor the behavioral development of infants at risk for autism spectrum disorder (ASD) because they have older affected siblings. Parents of 108 at-risk infants (74 males, 34 females) completed the POEMS from child age 1-24 months. The POEMS had acceptable psychometric properties and promising predictive validity.

Population- and family-based studies associate the MTHFR gene with idiopathic autism in simplex families.

Two methylenetetrahydrofolate reductase gene (MTHFR) functional polymorphisms were studied in 205 North American simplex (SPX) and 307 multiplex (MPX) families having one or more children with an autism spectrum disorder. Case-control comparisons revealed a significantly higher frequency of the low-activity 677T allele, higher prevalence of the 677TT genotype and higher frequencies of the 677T-1298A haplotype and double homozygous 677TT/1298AA genotype in affected individuals relative to controls. Family-based association testing demonstrated significant preferential transmission of the 677T and 1298A alleles and the 677T-1298A haplotype to affected offspring.

The course of cognitive-behavioral development in children with the FMR1 mutation, Williams-Beuren syndrome, and neurofibromatosis type 1: The effect of gender.

The course of cognitive-behavioral development in children with intellectual disabilities produced by genetic disorders has only recently begun to be examined systematically. Unfortunately, these studies are few in number. Previously, we examined cognitive-behavioral development in children with the fragile X (FMR1) mutation and found longitudinal decreases in both IQ and adaptive behavior (DQ) scores in most males and females with the full mutation.

Association of MAOA, 5-HTT, and NET promoter polymorphisms with gene expression and protein activity in human placentas.

Monoamine oxidase A (MAOA) and the transporters for serotonin (5-HTT) and norepinephrine (NET) may play important roles in regulating maternal monoamine neurotransmitters transferred across the placenta to the fetus. We investigated whether promoter polymorphisms in MAOA (uVNTR), 5-HTT (5-HTTLPR), and NET (NETpPR AAGG(4)) could influence gene expression and protein activity in human placentas. Normal term human placentas (n = 73) were collected, and placental MAOA, 5-HTT, and NET mRNA levels and protein activity were determined.

Brief report: telephone administration of the autism diagnostic interview--revised: reliability and suitability for use in research.

The Autism Diagnostic Interview--revised is one of the "gold standard" diagnostic tools for autism spectrum disorders. It is traditionally administered face-to-face. Cost and geographical concerns constrain the employment of the ADI-R for large-scale research projects.

Age at diagnosis of autism spectrum disorders in four regions of Canada.

Objectives: Early diagnosis of autism spectrum disorders ("autism") may lead to better treatment outcomes, reduces the stress parents experience when they do not understand the reasons for their child's behaviour, and empowers parents to make choices such as seeking genetic counseling. We examined the age at which Canadian children are diagnosed with autism, and analyzed whether there are geographic or temporal variations or differences by sex or diagnostic subtype.

Methods: As part of an autism surveillance program, in 2002/2003 we began collecting information on children with autism in Manitoba, Southeastern Ontario, Prince Edward Island, and Newfoundland and Labrador.

The DLX1and DLX2 genes and susceptibility to autism spectrum disorders.

An imbalance between excitation and inhibition in the cerebral cortex has been suggested as a possible etiology of autism. The DLX genes encode homeodomain-containing transcription factors controlling the generation of GABAergic cortical interneurons. The DLX1 and DLX2 genes lie head-to-head in 2q32, a region associated with autism susceptibility.

Using cluster ensemble and validation to identify subtypes of pervasive developmental disorders.

Pervasive Developmental Disorders (PDD) are neurodevelopmental disorders characterized by impairments in social interaction, communication and behavior. Given the diversity and varying severity of PDD, diagnostic tools attempt to identify homogeneous subtypes within PDD. Identifying subtypes can lead to targeted etiology studies and to effective type-specific intervention.

A DRD1 haplotype is associated with risk for autism spectrum disorders in male-only affected sib-pair families.

Individuals with autism spectrum disorders (ASDs) have impairments in executive function and social cognition, with males generally being more severely affected in these areas than females. Because the dopamine D1 receptor (encoded by DRD1) is integral to the neural circuitry mediating these processes, we examined the DRD1 gene for its role in susceptibility to ASDs by performing single marker and haplotype case-control comparisons, family-based association tests, and genotype-phenotype assessments (quantitative transmission disequilibrium tests: QTDT) using three DRD1 polymorphisms, rs265981C/T, rs4532A/G, and rs686T/C. Our previous findings suggested that the dopaminergic system may be more integrally involved in families with affected males only than in other families.

Trends in autism prevalence: diagnostic substitution revisited.

There has been little evidence to support the hypothesis that diagnostic substitution may contribute to increases in the administrative prevalence of autism. We examined trends in assignment of special education codes to British Columbia (BC) school children who had an autism code in at least 1 year between 1996 and 2004, inclusive. The proportion of children with an autism code increased from 12.

Studies of age-correlated features of cognitive-behavioral development in children and adolescents with genetic disorders.

Studies of age-related features of cognitive-behavioral deficits produced by genetic mutations permit us to draw inferences about how brain development may be related cognitive ability as the child ages. Except for Down syndrome (DS) and the fragile X mutation (FRAXA), little is known about the longitudinal changes in cognitive-behavioral development in individuals with genetic abnormalities producing learning disabilities (LD) or mental retardation (MR). The purpose of this prospective study was to compare and contrast age related to cognitive abilities, adaptive and maladaptive behaviors in children and adolescents in the same age range, diagnosed with one of three genetic disorders: the FRAXA mutation, Neurofibromatosis type 1 (NF1) or Williams-Beuren syndrome (WBS).

Large-scale copy number variants (CNVs): distribution in normal subjects and FISH/real-time qPCR analysis.

Background: Genomic copy number variants (CNVs) involving >1 kb of DNA have recently been found to be widely distributed throughout the human genome. They represent a newly recognized form of DNA variation in normal populations, discovered through screening of the human genome using high-throughput and high resolution methods such as array comparative genomic hybridization (array-CGH). In order to understand their potential significance and to facilitate interpretation of array-CGH findings in constitutional disorders and cancers, we studied 27 normal individuals (9 Caucasian; 9 African American; 9 Hispanic) using commercially available 1 Mb resolution BAC array (Spectral Genomics).

The G22A polymorphism of the ADA gene and susceptibility to autism spectrum disorders.

Inborn errors of purine metabolism have been implicated as a cause for some cases of autism. This hypothesis is supported by the finding of decreased adenosine deaminase (ADA) activity in the sera of some children with autism and reports of an association of the A allele of the ADA G22A (Asp8Asn) polymorphism in individuals with autism of Italian-descent. We tested the ADA G22A polymorphism in 126 North American affected sib-pair families but found no aberrant allele distributions in cases versus controls.

Trends in special education code assignment for autism: implications for prevalence estimates.

There is considerable controversy over reasons for observed increases in the prevalence of autism spectrum disorders. We examined trends in British Columbia education database coding of children with autism from 1996 to 2004. There was a significant linear increase in autism prevalence.

Haplotype study of intermediate-length alleles at the fragile X (FMR1) gene: ATL1, FMRb, and microsatellite haplotypes differ from those found in common-size FMR1 alleles.

The CGG repeat within the X-chromosome-linked FMR1 gene, which in hyperexpansion (> 200 copies) results in fragile X syndrome, is highly polymorphic. The mechanism of expansion is not well understood, but CGG repeats called intermediate-length or gray zone alleles (approximately equal 35-60 repeats) are thought to make up the FMR1 alleles showing initial steps in this expansion process. It has been hypothesized that the background haplotype of these alleles plays a role in their susceptibility to expansion.

Addressing health disparities through promoting equity for individuals with intellectual disability.

Intellectual disabilities (ID) are conditions originating before the age of 18 that result in significant limitations in intellectual functioning and conceptual, social and practical adaptive skills. IDs affect 1 to 3% of the population. Persons with ID are more likely to have physical disabilities, mental health problems, hearing impairments, vision impairments and communication disorders.

XLMR in MRX families 29, 32, 33 and 38 results from the dup24 mutation in the ARX (Aristaless related homeobox) gene.

Background: X-linked mental retardation (XLMR) is the leading cause of mental retardation in males. Mutations in the ARX gene in Xp22.1 have been found in numerous families with both nonsyndromic and syndromic XLMR.

Differential impact of the FMR1 gene on visual processing in fragile X syndrome.

Fragile X syndrome (FXS) is the most common form of heritable mental retardation, affecting approximately 1 in 4000 males. The syndrome arises from expansion of a trinucleotide repeat in the 5'-untranslated region of the fragile X mental retardation 1 (FMR1) gene, leading to methylation of the promoter sequence and lack of the fragile X mental retardation protein (FMRP). Affected individuals display a unique neurobehavioural phenotype that includes striking visual-motor deficits.

Behavioral relationship between autism and fragile x syndrome.

Previous researchers have reported autistic features in children with fragile X syndrome. We compared 21 children with pervasive developmental disorders (autism group) to 15 with fragile X syndrome on the Childhood Autism Rating Scale and the Reiss Scales for Children's Dual Diagnosis. The 7 children (47%) with fragile X who scored above the Childhood Autism Rating Scale cut-off (fragile X-autism group) were more impaired than the remaining children (fragile X-no autism) on Childhood Autism Rating Scale subscales related to emotion, visual and listening responses, and communication.

Autism and the X chromosome: no linkage to microsatellite loci detected using the affected sibling pair method.

The etiology of autism spectrum disorders (ASDs) is poorly understood, although it is clear that genetic factors play a major role. ASDs appear to be a heterogeneous group of disorders, making genetic analysis difficult in the absence of etiologically definable subgroups. The excess of males in the affected population has led to suggestions that an X-linked locus could play a role in the causation of autism or a related pervasive developmental disorder.