1. Babatz TD, Kumar RA, Sudi J, Dobyns WB, Christian SL. {{Copy number and sequence variants implicate APBA2 as an autism candidate gene}}. {Autism Res}. 2009 Dec;2(6):359-64.
We recently reported an autistic proband and affected sibling with maternally inherited microduplications within the 15q13.1 and 15q13.3 regions that contain a total of 4 genes. The amyloid precursor protein-binding protein A2 (APBA2) gene is located within the 15q13.1 duplication and encodes a neuronal adaptor protein essential to synaptic transmission that interacts directly with NRXN1 at the presynaptic membrane. We interpreted this as evidence for a putative role of APBA2 in autism as larger maternal duplications of 15q11-q13 are the most common known cause of autism. We therefore resequenced 512 subjects with autism spectrum disorder (ASD) and 463 controls, and identified 7 novel nonsynonymous coding variants in ASD subjects compared with 4 in controls. Five of the seven variants in the ASD group were predicted to affect protein function, alter residues conserved across 18 species, or both. All of the variants for which parental DNA was available were inherited. We also found two different nonsynonymous variants in two siblings with autism: (1) a paternally inherited heterozygous 6 bp deletion and (2) a maternally inherited heterozygous missense mutation, the latter also found in a single control. These results indicate compound heterozygous mutations of APBA2 in this autism sibship. The co-occurrence of two nonsynonymous mutations in both affected siblings in a single family, each transmitted from a different unaffected parent, suggest a role for APBA2 mutations in rare individuals with ASD.
2. Dufour-Rainfray D, Vourc’h P, Le Guisquet AM, Garreau L, Ternant D, Bodard S, Jaumain E, Gulhan Z, Belzung C, Andres CR, Chalon S, Guilloteau D. {{Behavior and serotonergic disorders in rats exposed prenatally to valproate: a model for autism}}. {Neurosci Lett}. 2009 Dec 24.
In order to explore whether some aspects of the autistic phenotype could be related to impairment of the serotonergic system, we chose an animal model which mimics a potential cause of autism, i.e. rats exposed to valproate (VPA) on the 9(th) embryonic day (E9). Previous studies have suggested that VPA exposure in rats at E9 caused a dramatic shift in the distribution of serotonergic neurons on postnatal day 50 (PND50). Behavioral studies have also been performed but on rats that were exposed to VPA later (E12.5). Our aim was to test whether VPA exposure at E9 induces comparable behavioral impairments than at E12.5 and causes serotonergic impairments which could be related to behavioral modifications. The results showed significant behavioral impairments such as a lower tendency to initiate social interactions and hyperlocomotor activity in juvenile male rats. The serotonin levels of these animals at PND50 were decreased (-46%) in the hippocampus, a structure involved in social behavior. This study suggests that VPA could have a direct or indirect action on the serotonergic system as early as the progenitor cell stage. Early embryonic exposure to VPA in rats provides a good model for several specific aspects of autism and should help to continue to explore pathophysiological hypotheses.
3. Jacob S, Landeros-Weisenberger A, Leckman JF. {{Autism spectrum and obsessive-compulsive disorders: OC behaviors, phenotypes and genetics}}. {Autism Res}. 2009 Dec;2(6):293-311.
Autism spectrum disorders (ASDs) are a phenotypically and etiologically heterogeneous set of disorders that include obsessive-compulsive behaviors (OCB) that partially overlap with symptoms associated with obsessive-compulsive disorder (OCD). The OCB seen in ASD vary depending on the individual’s mental and chronological age as well as the etiology of their ASD. Although progress has been made in the measurement of the OCB associated with ASD, more work is needed including the potential identification of heritable endophenotypes. Likewise, important progress toward the understanding of genetic influences in ASD has been made by greater refinement of relevant phenotypes using a broad range of study designs, including twin and family-genetic studies, parametric and nonparametric linkage analyses, as well as candidate gene studies and the study of rare genetic variants. These genetic analyses could lead to the refinement of the OCB phenotypes as larger samples are studied and specific associations are replicated. Like ASD, OCB are likely to prove to be multidimensional and polygenic. Some of the vulnerability genes may prove to be generalist genes influencing the phenotypic expression of both ASD and OCD while others will be specific to subcomponents of the ASD phenotype. In order to discover molecular and genetic mechanisms, collaborative approaches need to generate shared samples, resources, novel genomic technologies, as well as more refined phenotypes and innovative statistical approaches. There is a growing need to identify the range of molecular pathways involved in OCB related to ASD in order to develop novel treatment interventions.
4. Kuhlthau K, Orlich F, Hall TA, Sikora D, Kovacs EA, Delahaye J, Clemons TE. {{Health-Related Quality of Life in Children with Autism Spectrum Disorders: Results from the Autism Treatment Network}}. {J Autism Dev Disord}. 2009 Dec 24.
We examined data collected as a part of the Autism Treatment Network, a group of 15 autism centers across the United States and Canada. Mean Health-Related Quality of Life (HRQoL) scores of the 286 children assessed were significantly lower than those of healthy populations (according to published norms). When compared to normative data from children with chronic conditions, children with ASD demonstrated worse HRQoL for total, psychosocial, emotional and social functioning, but did not demonstrate differing scores for physical and school functioning. HRQoL was not consistently related to ASD diagnosis or intellectual ability. However, it was consistently related to internalizing and externalizing problems as well as repetitive behaviors, social responsiveness, and adaptive behaviors. Associations among HRQoL and behavioral characteristics suggest that treatments aimed at improvements in these behaviors may improve HRQoL.
5. Russo AJ, Krigsman A, Jepson B, Wakefield A. {{Decreased Serum Hepatocyte Growth Factor (HGF) in Autistic Children with Severe Gastrointestinal Disease}}. {Biomark Insights}. 2009;4:181-90.
AIM: To assess serum Hepatocyte Growth Factor (HGF) levels in autistic children with severe gastrointestinal (GI) disease and to test the hypothesis that there is a relationship between GI pathology and HGF concentration. SUBJECTS AND METHODS: Serum from 29 autistic children with chronic digestive disease (symptoms for a minimum of 6-12 months), most with ileo-colonic lymphoid nodular hyperplasia (LNH-markedly enlarged lymphoid nodules) and inflammation of the colorectum, small bowel and/or stomach), and 31 controls (11 age matched autistic children with no GI disease, 11 age matched non autistic children without GI disease and 9 age matched non autistic children with GI disease) were tested for HGF using ELISAs. HGF concentration of autistic children with GI disease was compared to GI disease severity. RESULTS: Autistic children with GI disease had significantly lower serum levels of HGF compared to controls (autistic without GI disease; p = 0.0005, non autistic with no GI disease; p = 0.0001, and non autistic with GI disease; p = 0.001). Collectively, all autistic children had significantly lower HGF levels when compared to non autistic children (p < 0.0001). We did not find any relationship between severity of GI disease and HGF concentration in autistic children with GI disease. DISCUSSION: These results suggest an association between HGF serum levels and the presence of GI disease in autistic children and explain a potential functional connection between the Met gene and autism. The concentration of serum HGF may be a useful biomarker for autistic children, especially those with severe GI disease.
6. van der Zwaag B, Staal WG, Hochstenbach R, Poot M, Spierenburg HA, de Jonge MV, Verbeek NE, van ‘t Slot R, van Es MA, Staal FJ, Freitag CM, Buizer-Voskamp JE, Nelen MR, van den Berg LH, van Amstel HK, van Engeland H, Burbach JP. {{A co-segregating microduplication of chromosome 15q11.2 pinpoints two risk genes for autism spectrum disorder}}. {Am J Med Genet B Neuropsychiatr Genet}. 2009 Dec 22.
High resolution genomic copy-number analysis has shown that inherited and de novo copy-number variations contribute significantly to autism pathology, and that identification of small chromosomal aberrations related to autism will expedite the discovery of risk genes involved. Here, we report a microduplication of chromosome 15q11.2, spanning only four genes, co-segregating with autism in a Dutch pedigree, identified by SNP microarray analysis, and independently confirmed by FISH and MLPA analysis. Quantitative RT-PCR analysis revealed over 70% increase in peripheral blood mRNA levels for the four genes present in the duplicated region in patients, and RNA in situ hybridization on mouse embryonic and adult brain sections revealed that two of the four genes, CYFIP1 and NIPA1, were highly expressed in the developing mouse brain. These findings point towards a contribution of microduplications at chromosome 15q11.2 to autism, and highlight CYFIP1 and NIPA1 as autism risk genes functioning in axonogenesis and synaptogenesis. Thereby, these findings further implicate defects in dosage-sensitive molecular control of neuronal connectivity in autism. However, the prevalence of this microduplication in patient samples was statistically not significantly different from control samples (0.94% in patients vs. 0.42% controls, P = 0.247), which suggests that our findings should be interpreted with caution and indicates the need for studies that include large numbers of control subjects to ascertain the impact of these changes on a population scale. (c) 2009 Wiley-Liss, Inc.
7. Verhoeven JS, De Cock P, Lagae L, Sunaert S. {{Neuroimaging of autism}}. {Neuroradiology}. Jan;52(1):3-14.
Neuroimaging studies done by means of magnetic resonance imaging (MRI) have provided important insights into the neurobiological basis for autism. The aim of this article is to review the current state of knowledge regarding brain abnormalities in autism. Results of structural MRI studies dealing with total brain volume, the volume of the cerebellum, caudate nucleus, thalamus, amygdala and the area of the corpus callosum are summarised. In the past 5 years also new MRI applications as functional MRI and diffusion tensor imaging brought considerable new insights in the pathophysiological mechanisms of autism. Dysfunctional activation in key areas of verbal and non-verbal communication, social interaction, and executive functions are revised. Finally, we also discuss white matter alterations in important communication pathways in the brain of autistic patients.
