[show abstract][hide abstract] ABSTRACT: Maternal 15q11-q13 duplication is the most common copy number variant in autism, accounting for ∼1-3% of cases. The 15q11-q13 region is subject to epigenetic regulation, and genomic copy number losses and gains cause genomic disorders in a parent-of-origin-specific manner. One 15q11-q13 locus encodes the GABA(A) receptor β3 subunit gene (GABRB3), which has been implicated by several studies in both autism and absence epilepsy, and the co-morbidity of epilepsy in autism is well established. We report that maternal transmission of a GABRB3 signal peptide variant (P11S), previously implicated in childhood absence epilepsy, is associated with autism. An analysis of wild-type and mutant β3 subunit-containing α1β3γ2 or α3β3γ2 GABA(A) receptors shows reduced whole-cell current and decreased β3 subunit protein on the cell surface due to impaired intracellular β3 subunit processing. We thus provide the first evidence of an association between a specific GABA(A) receptor defect and autism, direct evidence that this defect causes synaptic dysfunction that is autism relevant and the first maternal risk effect in the 15q11-q13 autism duplication region that is linked to a coding variant.
[show abstract][hide abstract] ABSTRACT: Genetic susceptibility to antisocial behavior may increase fetal sensitivity to prenatal exposure to cigarette smoke. Testing putative gene x exposure mechanisms requires precise measurement of exposure and outcomes. We tested whether a functional polymorphism in the gene encoding the enzyme monoamine oxidase A (MAOA) interacts with exposure to predict pathways to adolescent antisocial behavior. We assessed both clinical and information-processing outcomes. One hundred seventy-six adolescents and their mothers participated in a follow-up of a pregnancy cohort with well-characterized exposure. A sex-specific pattern of gene x exposure interaction was detected. Exposed boys with the low-activity MAOA 5' uVNTR (untranslated region variable number of tandem repeats) genotype were at increased risk for conduct disorder (CD) symptoms. In contrast, exposed girls with the high-activity MAOA uVNTR genotype were at increased risk for both CD symptoms and hostile attribution bias on a face-processing task. There was no evidence of a gene-environment correlation (rGE). Findings suggest that the MAOA uVNTR genotype, prenatal exposure to cigarettes and sex interact to predict antisocial behavior and related information-processing patterns. Future research to replicate and extend these findings should focus on elucidating how gene x exposure interactions may shape behavior through associated changes in brain function.
[show abstract][hide abstract] ABSTRACT: We are on the brink of exciting discoveries into the molecular genetic underpinnings of autism spectrum disorder. Overwhelming evidence of genetic involvement coupled with increased societal attention to the disorder has drawn in more researchers and more research funding. Autism is a strongly genetic yet strikingly complex disorder, in which evidence from different cases supports chromosomal disorders, rare single gene mutations, and multiplicative effects of common gene variants. With more and more interesting yet sometimes divergent findings emerging every year, it is tempting to view these initial molecular studies as so much noise, but the data have also started to coalesce in certain areas. In particular, recent studies in families with autism spectrum disorder have identified uncommon occurrences of a novel genetic syndrome caused by disruptions of the NLGN4 gene on chromosome Xp22. Previous work had identified another uncommon syndrome that is caused by maternal duplications of the chromosome 15q11-13 region. We highlight other converging findings, point toward those areas most likely to yield results, and emphasize the contributions of multiple approaches to identifying the genes of interest.
[show abstract][hide abstract] ABSTRACT: The broad variation in phenotypes and severities within autism spectrum disorders suggests the involvement of multiple predisposing factors, interacting in complex ways with normal developmental courses and gradients. Identification of these factors, and the common developmental path into which they feed, is hampered by the large degrees of convergence from causal factors to altered brain development, and divergence from abnormal brain development into altered cognition and behaviour. Genetic, neurochemical, neuroimaging, and behavioural findings on autism, as well as studies of normal development and of genetic syndromes that share symptoms with autism, offer hypotheses as to the nature of causal factors and their possible effects on the structure and dynamics of neural systems. Such alterations in neural properties may in turn perturb activity-dependent development, giving rise to a complex behavioural syndrome many steps removed from the root causes. Animal models based on genetic, neurochemical, neurophysiological, and behavioural manipulations offer the possibility of exploring these developmental processes in detail, as do human studies addressing endophenotypes beyond the diagnosis itself.Keywords: autism, development, neurochemistry, genetics, animal models
[show abstract][hide abstract] ABSTRACT: The serotonin transporter gene (SLC6A4, MIM 182138) is a candidate gene in autistic disorder based on neurochemical, neuroendocrine studies and the efficacy of potent serotonin transporter inhibitors in reducing ritualistic behaviors and related aggression. An insertion/deletion polymorphism (5-HTTLPR) in the promoter region and a variable number of tandem repeat polymorphism (VNTR) in the second intron, were previously identified and suggested to modulate transcription. Six previous family-based association studies of SLC6A4 in autistic disorder have been conducted, with four studies showing nominally significant transmission disequilibrium and two studies with no evidence of nominally significant transmission disequilibrium. In the present study, TDT was conducted in 81 new trios. A previous finding of transmission disequilibrium between a haplotype consisting of the 5-HTTLPR and intron 2 VNTR was replicated in this study, but not preferential transmission of 5-HTTLPR as an independent marker. Because of inconsistent transmission of 5-HTTLPR across studies, SLC6A4 and its flanking regions were sequenced in 10 probands, followed by typing of 20 single nucleotide polymorphisms (SNPs) and seven simple sequence repeat (SSR) polymorphisms in 115 autism trios. When individual markers were analyzed by TDT, seven SNP markers and four SSR markers (six SNPs, 5-HTTLPR and the second intron VNTR from promoter 1A through intron 2 of SLC6A4, one SSR from intron 7 of SLC6A4, one SNP from the bleomycin hydrolase gene (BLMH, MIM 602403) and one SSR telomeric to BLMH) showed nominally significant evidence of transmission disequilibrium. Four markers showed stronger evidence of transmission disequilibrium (TDT(max) P = 0.0005) than 5-HTTLPR.
[show abstract][hide abstract] ABSTRACT: Impairment in social reciprocity is a central component of autism. In preclinical studies, arginine vasopressin (AVP) has been shown to increase a range of social behaviors, including affiliation and attachment, via the V(1a) receptor (AVPR1A) in the brain. Both the behavioral effects of AVP and the neural distribution of the V1a receptor vary greatly across mammalian species. This difference in regional receptor expression as well as differences in social behavior may result from a highly variable repetitive sequence in the 5' flanking region of the V1a gene (AVPR1A). Given this comparative evidence for a role in inter-species variation in social behavior, we explored whether within our own species, variation in the human AVPR1A may contribute to individual variations in social behavior, with autism representing an extreme form of social impairment. We genotyped two microsatellite polymorphisms from the 5' flanking region of AVPR1A for 115 autism trios and found nominally significant transmission disequilibrium between autism and one of the microsatellite markers by Multiallelic Transmission/Disequilibrium test (MTDT) that was not significant after Bonferroni correction. We also screened approximately 2 kb of the 5' flanking region and the coding region and identified 10 single nucleotide polymorphisms.
[show abstract][hide abstract] ABSTRACT: To examine the efficacy of intravenous porcine secretin for the treatment of autistic disorder.
Randomized, double-blind, placebo-controlled, crossover design. Fifty-six subjects with autistic disorder received either a secretin or placebo infusion at baseline and the other substance at week 4. Subjects were given the Autism Diagnostic Observation Schedule (ADOS) and other pertinent developmental measures at baseline and at weeks 4 and 8 to assess drug effects.
For the primary efficacy analysis, change of ADOS social-communication total score from week 0 to week 4, no statistically significant difference was obtained between placebo (-0.8 +/- 2.9) and secretin groups (-0.6 +/- 1.4; t54 = 0.346, p < .73). The other measures showed no treatment effect for secretin compared with placebo.
There was no evidence for efficacy of secretin in this randomized, placebo-controlled, double-blind trial.
Journal of the American Academy of Child & Adolescent Psychiatry 11/2001; 40(11):1293-9. · 6.97 Impact Factor
[show abstract][hide abstract] ABSTRACT: To evaluate the safety and effectiveness of sertraline in the long-term treatment of pediatric obsessive-compulsive disorder (OCD).
Children (6-12 years; n= 72) and adolescents (13-18 years; n = 65) with DSM-III-R-defined OCD who had completed a 12-week, double-blind, placebo-controlled sertraline study were given open-label sertraline 50 to 200 mg/day in this 52-week extension study. Concomitant psychotherapy was allowed during the extension study Outcome was evaluated by the Children's Yale-Brown Obsessive Compulsive Scale (CY-BOCS), National Institute of Mental Health Global Obsessive-Compulsive Scale, and Clinical Global Impression Severity (CGI-S) and Improvement (CGI-I) scores.
Significant improvement (p < .0001) was demonstrated on all four outcome parameters on an intent-to-treat analysis for the overall study population (n = 132), as well as the child and the adolescent samples. At endpoint, 72% of children and 61% of adolescents met response criteria (>25% decrease in CY-BOCS and a CGI-I score of 1 or 2). Significant (p < .05) improvements were also demonstrated from the extension study baseline to endpoint on all outcome parameters in those patients who received sertraline during the 12-week, double-blind acute study. Long-term sertraline treatment was well tolerated, and there were no discontinuations due to changes in vital signs, laboratory values, or electrocardiograms.
Sertraline (50-200 mg/day) was effective and generally well tolerated in the treatment of childhood and adolescent OCD for up to 52 weeks. Improvement was seen with continued treatment.
Journal of the American Academy of Child & Adolescent Psychiatry 10/2001; 40(10):1175-81. · 6.97 Impact Factor
[show abstract][hide abstract] ABSTRACT: Serotonergic (5-HT) dysfunction has been implicated in the etiology of both behavioral disinhibition (BD) and negative affect (NA). This work extends our previous finding of relationships between whole blood 5-HT and both BD and NA in pubescent, but not prepubescent, children of alcoholics and continues examination of a hypothesized role of 5-HT dysfunction in alcoholism risk. The long and short (L and S) variants of the 5-HT transporter gene-linked polymorphic region (5-HTTLPR) are responsible for differing transcriptional efficiencies in 5-HT uptake. Although associations have been found between the SS 5-HTTLPR genotype and severe alcoholism and neuroticism, recent reports describe relationships between the LL genotype and both low level of response to alcohol and alcoholism diagnosis and a predominance of the LL genotype in early-onset alcoholics.
This report is from an ongoing prospective study of the development of risk for alcoholism and other problematic outcomes in a sample of families classified by father's alcoholism subtype. This study examines relationships between 5-HTTLPR genotype and both child BD (Child Behavior Checklist Aggressive Behavior) and NA (Child Behavior Checklist Anxious/Depressed) in offspring from 47 families.
Results showed significantly higher levels of BD and NA in the 16 children with the LL genotype than the 46 SS or SL children.
Behaviors of undercontrol, which occur at increased rates in children of alcoholics, may be genetically influenced through the regulation of the 5-HT transporter. Due to the small sample size and the preliminary nature of our findings, replication is necessary.
Alcoholism Clinical and Experimental Research 08/2001; 25(7):953-9. · 3.42 Impact Factor
[show abstract][hide abstract] ABSTRACT: Maternal duplications of the imprinted 15q11-13 domain result in an estimated 1%-2% of autism-spectrum disorders, and linkage to autism has been identified within 15q12-13. UBE3A, the Angelman syndrome gene, has, to date, been the only maternally expressed, imprinted gene identified within this region, but mutations have not been found in autistic patients. Here we describe the characterization of ATP10C, a new human imprinted gene, which encodes a putative protein homologous to the mouse aminophospholipid-transporting ATPase Atp10c. ATP10C maps within 200 kb distal to UBE3A and, like UBE3A, also demonstrates imprinted, preferential maternal expression in human brain. The location and imprinted expression of ATP10C thus make it a candidate for chromosome 15-associated autism and suggest that it may contribute to the Angelman syndrome phenotype.
The American Journal of Human Genetics 07/2001; 68(6):1501-5. · 11.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: To test the hypothesis that amantadine hydrochloride is a safe and effective treatment for behavioral disturbances--for example, hyperactivity and irritability--in children with autism.
Thirty-nine subjects (intent to treat; 5-19 years old; IQ > 35) had autism diagnosed according to DSM-IV and ICD-10 criteria using the Autism Diagnostic Interview-Revised and the Autism Diagnostic Observation Schedule-Generic. The Aberrant Behavior Checklist-Community Version (ABC-CV) and Clinical Global Impressions (CGI) scale were used as outcome variables. After a 1-week, single-blind placebo run-in, patients received a single daily dose of amantadine (2.5 mg/kg per day) or placebo for the next week, and then bid dosing (5.0 mg/kg per day) for the subsequent 3 weeks.
When assessed on the basis of parent-rated ABC-CV ratings of irritability and hyperactivity, the mean placebo response rate was 37% versus amantadine at 47% (not significant). However, in the amantadine-treated group there were statistically significant improvements in absolute changes in clinician-rated ABC-CVs for hyperactivity (amantadine -6.4 versus placebo -2.1; p = .046) and inappropriate speech (-1.9 versus 0.4; p = .008). CGI scale ratings were higher in the amantadine group: 53% improved versus 25% (p = .076). Amantadine was well tolerated.
Parents did not report statistically significant behavioral change with amantadine. However, clinician-rated improvements in behavioral ratings following treatment with amantadine suggest that further studies with this or other drugs acting on the glutamatergic system are warranted. The design of these and similar drug trials in children with autistic disorder must take into account the possibility of a large placebo response.
Journal of the American Academy of Child & Adolescent Psychiatry 06/2001; 40(6):658-65. · 6.97 Impact Factor
[show abstract][hide abstract] ABSTRACT: In summary, autism genetics has moved from a time of identification of heritability and determination of risk of "lesser variants" or the "broader phenotype" in relatives to a phase where some cases of autism have a definite basis such as maternally inherited duplications of 15q11-q13, identification of mutations causing AS, Rett syndrome, and FRAXA. The first phase of genome-wide screens has not revealed definitive linkage, but as samples are enlarged and meta-analyses performed, the strongest linkage findings are likely to yield susceptibility variants once fine mapping proceeds. Recent statistical and molecular genetic analysis methods make the additional work feasible. However, frustrating it may be to be in this phase of the research, it is an essential part of the process of moving from identification of heritability in autism to understanding of the disorder in a way that may permit improved treatment in the future. If there is an advantage to autism being a complex rather than monogenic disorder, it is that the nature of multiplicative or interacting genetic risk is that prevention or treatment directed to any of the identified genetic risks may be sufficient to break a chain of pathophysiology. More genes increase the chance that one or more will have implications for treatment development sooner.
Child and Adolescent Psychiatric Clinics of North America 05/2001; 10(2):333-50. · 2.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: The first genome scan conducted in early-onset obsessive-compulsive disorder used a non-parametric analysis to identify a peak in a region of chromosome 9 containing the gene SLC1A1, which codes for the neuronal and epithelial glutamate transporter EAAC1. Interaction between the glutamatergic and serotonergic systems within the striatum suggests EAAC1 as a functional candidate in OCD as well. We determined the genomic organization of SLC1A1 primarily by using primers designed from cDNA sequence to amplify from adaptor-ligated genomic DNA restriction fragments. In order to confirm SLC1A1 as a positional candidate in early-onset OCD, common single nucleotide polymorphisms (SNPs) were identified that enabled mapping of SLC1A1 within the region of the lod score peak. Based on the linkage evidence, the coding region was sequenced in the probands of the seven families included in the genome scan. No evidence was found for a functional mutation, but several SNPs were identified. Capillary electrophoresis SSCP typing of a haplotype consisting of two common SNPs within EAAC1 revealed no significant linkage disequilibrium.
[show abstract][hide abstract] ABSTRACT: Twin and family studies suggest that familial transmission in autism extends to a spectrum of social and behavioral deficits that characterize individuals who have significant impairments within the autism spectrum, but do not meet formal criteria for autistic disorder. Standardized diagnostic instruments, including the Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS-WPS Edition), offer the opportunity to quantify deficits across the autism spectrum, controlling effects of language and cognitive delay, in individuals with significant impairments. It is suggested that quantitative measures of social reciprocity and repetitive behaviors and interests, with separate quantification of expressive language level and nonverbal intelligence, most accurately reflect the range of behavioral phenotypes in autism spectrum disorders.
American Journal of Medical Genetics 02/2001; 105(1):36-8.
[show abstract][hide abstract] ABSTRACT: Autism is a common disorder of childhood, affecting 1 in 500 children. Yet, it often remains unrecognized and undiagnosed until or after late preschool age because appropriate tools for routine developmental screening and screening specifically for autism have not been available. Early identification of children with autism and intensive, early intervention during the toddler and preschool years improves outcome for most young children with autism. This practice parameter reviews the available empirical evidence and gives specific recommendations for the identification of children with autism. This approach requires a dual process: 1) routine developmental surveillance and screening specifically for autism to be performed on all children to first identify those at risk for any type of atypical development, and to identify those specifically at risk for autism; and 2) to diagnose and evaluate autism, to differentiate autism from other developmental disorders.
[show abstract][hide abstract] ABSTRACT: Serotonergic (5-HT) dysfunction has been implicated in both behavioral disinhibition and negative affect in adults. Although our group's previous work found decreased whole blood 5-HT in high versus low behavior problem children of alcoholics, some child/adolescent studies report conflicting results, and 5-HT's role in negative affect has been largely unexamined. Age-related developmental factors may play a role in these relationships.
This report is from an ongoing prospective study of the development of risk for alcohol abuse/dependence and other problematic outcomes in a sample of families subtyped by father's alcoholism classification. The present study extends previous work and examines relationships between whole blood 5-HT and both child behavioral disinhibition (an aggression index from the Child Behavior Checklist) and negative affect (Child Behavior Checklist Anxious/Depressed scale) in offspring from 47 families (N = 45 boys and 17 girls; mean age = 10.88+/-2.03 yr).
The most important finding was that puberty moderated relationships between 5-HT and both behavioral disinhibition and negative affect with a relationship for pubescent children (n = 14, r = -0.54, p = 0.05: r = -0.57,p = 0.04, respectively) but no relationship for prepubescent children (n = 48, r = 0.05, p = 0.75; r = -0.15, p = 0.31, respectively).
The moderating effects of puberty may help clarify inconsistencies in child/adolescent literature. Furthermore, there appears to be a relationship between 5-HT and negative affect which parallels that between 5-HT and behavioral disinhibition. Pubertal status may be an important variable to evaluate as a moderator in relation to the developmental context of the role 5-HT dysfunction may play in various models of behavior related to alcoholism over the early life course.
Alcoholism Clinical and Experimental Research 08/2000; 24(7):972-9. · 3.42 Impact Factor