Pubmed du 2/05/09

mardi 5 mai 2009

1. Cho SC, Yim SH, Yoo HK, Kim MY, Jung GY, Shin GW, Kim BN, Hwang JW, Kang JJ, Kim TM, Chung YJ. Copy number variations associated with idiopathic autism identified by whole-genome microarray-based comparative genomic hybridization. Psychiatr Genet ;2009 (Apr 29)

OBJECTIVES : Autism spectrum disorder (ASD) has been thought to have strong genetic background, but major contributing genes or associated molecular-genetic pathways are yet to be identified. To explore the idiopathic ASD-associated copy number variations (CNVs), we conducted case-control study using whole-genome copy number analysis. METHODS : Whole-genome microarray-based comparative genomic hybridization was carried out on 28 children (24 boys and four girls) diagnosed as ASD and 62 Korean adults (45 males and 17 females) without any signs of abnormalities and family history of genetic disorders as normal controls. Fluorescence in-situ hybridization and capillary electrophoresis-single-strand conformational polymorphism were used for quantitative verification of the ASD-associated CNVs. RESULTS : Thirty-eight CNVs were identified. Among them, the distributions of copy number loss CNVs on 8p23.1 (odds ratio : 5.1, 95% confidence interval : 1.7-14.5, P=0.003) and on 17p11.2 (odds ratio : uncalculable because of zero cell, P=0.008) were found to be significantly different between ASD and control groups. DEFENSIN family occurs in a cluster at 8p23.1 region. Fluorescence in-situ hybridization and capillary electrophoresis-single-strand conformational polymorphism coherently showed reduced copy number of DEFENSIN in cases with 8p23.1 copy number loss CNV, which validated microarray-based comparative genomic hybridization results ; but there are no known coding genes in the CNV on 17p11.2. CONCLUSION : Our approach as well as results can help to elucidate the genetic mechanism of idiopathic ASD.

2. Herrera CG, Hung J, Zhang Y, Kertesz AC, Espina FJ, Colicos MA. Altered synchrony and connectivity in neuronal networks expressing an autism-related mutation of neuroligin 3. Neuroscience ;2009 (Apr 27)

The neuroligin (NL) gene family codes for brain specific cell adhesion molecules that play an important role in synaptic connectivity. Recent studies have identified NL mutations linked to patients with Autism Spectrum Disorders (ASD). Cognitive deficits seen in autistic patients are hypothesized to arise from altered synchronicity both within and between brain regions. Here we show how the expression of autism-associated neuroligin mutation R471C-NL3 affects synchrony in dissociated cultures of rat hippocampal neurons. Spontaneous network activity patterns of cultures expressing wildtype and mutant NL3 were measured by optical techniques. Firing events were quantified and compared by cross-correlation analysis. Our results suggest that NL3 overexpression enhances synchrony of spontaneous activity patterns, however this ability is reduced with the R471C-NL3 mutation. We investigated the structural basis of this phenomenon using fractal dimension analysis to characterize the arrangement of axon trajectories. R471C-NL3 cultures were associated with lower fractal dimensions and higher lacunarity values, indicating a decrease in the complexity of axonal architecture. Transfection of R471C-NL3 into a subpopulation of cells in a network resulted in neuronal degeneration. This degeneration likely affected the inhibitory population of neurons, as there were half as many (p<0.01, n=12) glutamate decarboxylase (GAD) 65 expressing cells in R471C-NL3 cultures compared to wildtype NL3 and control cultures. Electrophysiological recordings showed a reduction of inhibitory activity in networks carrying the mutation in comparison to networks overexpressing wild-type NL3. Together, these data support the hypothesis that the autism-associated NL3 mutation affects information processing in neuronal networks by altering network architecture and synchronicity.

3. Toal F, Bloemen OJ, Deeley Q, Tunstall N, Daly EM, Page L, Brammer MJ, Murphy KC, Murphy DG. Psychosis and autism : magnetic resonance imaging study of brain anatomy. Br J Psychiatry ;2009 (May) ;194(5):418-425.

BACKGROUND : Autism-spectrum disorder is increasingly recognised, with recent studies estimating that 1% of children in South London are affected. However, the biology of comorbid mental health problems in people with autism-spectrum disorder is poorly understood. AIMS : To investigate the brain anatomy of people with autism-spectrum disorder with and without psychosis. METHOD : We used in vivo magnetic resonance imaging and compared 30 adults with autism-spectrum disorder (14 with a history psychosis) and 16 healthy controls. RESULTS : Compared with controls both autism-spectrum disorder groups had significantly less grey matter bilaterally in the temporal lobes and the cerebellum. In contrast, they had increased grey matter in striatal regions. However, those with psychosis also had a significant reduction in grey matter content of frontal and occipital regions. Contrary to our expectation, within autism-spectrum disorder, comparisons revealed that psychosis was associated with a reduction in grey matter of the right insular cortex and bilaterally in the cerebellum extending into the fusiform gyrus and the lingual gyrus. CONCLUSIONS : The presence of neurodevelopmental abnormalities normally associated with autism-spectrum disorder might represent an alternative ’entry-point’ into a final common pathway of psychosis.


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