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Genome-wide association analyses of child genotype effects and parent-of-origin effects in specific language impairment.

February 28, 2014 - 7:37am

Genome-wide association analyses of child genotype effects and parent-of-origin effects in specific language impairment.

Genes Brain Behav. 2014 Feb 26;

Authors: Nudel R, Simpson NH, Baird G, O'Hare A, Conti-Ramsden G, Bolton PF, Hennessy ER, the SLI Consortium, Ring SM, Smith GD, Francks C, Paracchini S, Monaco AP, Fisher SE, Newbury DF

Abstract
Specific language impairment (SLI) is a neurodevelopmental disorder that affects linguistic abilities when development is otherwise normal. We report the results of a genome-wide association study of SLI which included parent-of-origin effects and child genotype effects and used 278 families of language-impaired children. The child genotype effects analysis did not identify significant associations. We found genome-wide significant paternal parent-of-origin effects on chromosome 14q12 (P = 3.74 × 10(-8) ) and suggestive maternal parent-of-origin-effects on chromosome 5p13 (P = 1.16 × 10(-7) ). A subsequent targeted association of six single-nucleotide-polymorphisms (SNPs) on chromosome 5 in 313 language-impaired individuals from the ALSPAC cohort replicated the maternal effects, albeit in the opposite direction (P = 0.001); as fathers' genotypes were not available in the ALSPAC study, the replication analysis did not include paternal parent-of-origin effects. The paternally-associated SNP on chromosome 14 yields a non-synonymous coding change within the NOP9 gene. This gene encodes an RNA-binding protein that has been reported to be significantly dysregulated in individuals with schizophrenia. The region of maternal association on chromosome 5 falls between the PTGER4 and DAB2 genes, in a region previously implicated in autism and ADHD. The top SNP in this association locus is a potential expression QTL of ARHGEF19 (also called WGEF) on chromosome 1. Members of this protein family have been implicated in intellectual disability. In sum, this study implicates parent-of-origin effects in language impairment, and adds an interesting new dimension to the emerging picture of shared genetic etiology across various neurodevelopmental disorders.

PMID: 24571439 [PubMed - as supplied by publisher]

Variations analysis of NLGN3 and NLGN4X gene in Chinese autism patients.

February 27, 2014 - 7:10am

Variations analysis of NLGN3 and NLGN4X gene in Chinese autism patients.

Mol Biol Rep. 2014 Feb 26;

Authors: Xu X, Xiong Z, Zhang L, Liu Y, Lu L, Peng Y, Guo H, Zhao J, Xia K, Hu Z

Abstract
Autism is a neurodevelopmental disorder clinically characterized by impairment of social interaction, deficits in verbal communication, as well as stereotypic and repetitive behaviors. Several studies have implicated that abnormal synaptogenesis was involved in the incidence of autism. Neuroligins are postsynaptic cell adhesion molecules and interacted with neurexins to regulate the fine balance between excitation and inhibition of synapses. Recently, mutation analysis, cellular and mice models hinted neuroligin mutations probably affected synapse maturation and function. In this study, four missense variations [p.G426S (NLGN3), p.G84R (NLGN4X), p.Q162 K (NLGN4X) and p.A283T (NLGN4X)] in four different unrelated patients have been identified by PCR and direct sequencing. These four missense variations were absent in the 453 controls and have not been reported in 1000 Genomes Project. Bioinformatic analysis of the four missense variations revealed that p.G84R and p.A283T were "Probably Damaging". The variations may cause abnormal synaptic homeostasis and therefore trigger the patients more predisposed to autism. By case-control analysis, we identified the common SNPs (rs3747333 and rs3747334) in the NLGN4X gene significantly associated with risk for autism [p = 5.09E-005; OR 4.685 (95 % CI 2.073-10.592)]. Our data provided a further evidence for the involvement of NLGN3 and NLGN4X gene in the pathogenesis of autism in Chinese population.

PMID: 24570023 [PubMed - as supplied by publisher]

Genetic association and gene-gene interaction analyses suggest likely involvement of ITGB3 and TPH2 with autism spectrum disorder (ASD) in the Indian population.

February 27, 2014 - 7:10am
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Genetic association and gene-gene interaction analyses suggest likely involvement of ITGB3 and TPH2 with autism spectrum disorder (ASD) in the Indian population.

Prog Neuropsychopharmacol Biol Psychiatry. 2013 Aug 1;45:131-43

Authors: Singh AS, Chandra R, Guhathakurta S, Sinha S, Chatterjee A, Ahmed S, Ghosh S, Rajamma U

Abstract
BACKGROUND: Serotoninergic dysfunction leads to neurodevelopmental abnormalities and behavioral impairments. Platelet hyperserotoninemia is reported as the best identified endophenotype for autism spectrum disorders. Therefore, in the present study we investigate the association of TPH2, the rate limiting enzyme in 5-HT biosynthesis and ITGB3, a serotonin quantitative trait locus with ASD in the Indian population.
METHODS: Population and family-based genetic association and gene-gene interaction analyses were performed to evaluate the role of ITGB3 and TPH2 markers in ASD etiology.
RESULTS: Association tests using ITGB3 markers revealed significant paternal overtransmission of T allele of rs5918 to male probands. Interestingly for TPH2, we observed significant overrepresentation of A-A (rs11179000-rs4290270), G-A (rs4570625-rs4290270), G-G-A (rs4570625-rs11179001-rs4290270) and A-G-A (rs11179000-rs11179001-rs4290270) haplotypes in the controls and maternal preferential transmission of A-A (rs11179001-rs7305115), T-A-A (rs4570625-rs11179001-rs7305115) and T-A-A (rs11179000-rs11179001-rs7305115) and nontransmission of G-G-A (rs4570625-rs11179001-rs7305115) haplotypes to the affected offspring. Moreover, interaction of ITGB3 marker, rs15908 with TPH2 markers was found to be significant and influenced by the sex of the probands. Predicted individual risk, which varied from very mild to moderate, supports combined effect of these markers in ASD.
CONCLUSION: Overall results of the present study indicate likely involvement of ITGB3 and TPH2 in the pathophysiology of ASD in the Indian population.

PMID: 23628433 [PubMed - indexed for MEDLINE]

Altered functional connectivity of the language network in ASD: Role of classical language areas and cerebellum.

February 26, 2014 - 6:43am

Altered functional connectivity of the language network in ASD: Role of classical language areas and cerebellum.

Neuroimage Clin. 2014;4:374-82

Authors: Verly M, Verhoeven J, Zink I, Mantini D, Peeters R, Deprez S, Emsell L, Boets B, Noens I, Steyaert J, Lagae L, De Cock P, Rommel N, Sunaert S

Abstract
The development of language, social interaction and communicative skills is remarkably different in the child with autism spectrum disorder (ASD). Atypical brain connectivity has frequently been reported in this patient population. However, the neural correlates underlying their disrupted language development and functioning are still poorly understood. Using resting state fMRI, we investigated the functional connectivity properties of the language network in a group of ASD patients with clear comorbid language impairment (ASD-LI; N = 19) and compared them to the language related connectivity properties of 23 age-matched typically developing children. A verb generation task was used to determine language components commonly active in both groups. Eight joint language components were identified and subsequently used as seeds in a resting state analysis. Interestingly, both the interregional and the seed-based whole brain connectivity analysis showed preserved connectivity between the classical intrahemispheric language centers, Wernicke's and Broca's areas. In contrast however, a marked loss of functional connectivity was found between the right cerebellar region and the supratentorial regulatory language areas. Also, the connectivity between the interhemispheric Broca regions and modulatory control dorsolateral prefrontal region was found to be decreased. This disruption of normal modulatory control and automation function by the cerebellum may underlie the abnormal language function in children with ASD-LI.

PMID: 24567909 [PubMed]

Genetics: Potassium channel function linked to autism and epilepsy.

February 26, 2014 - 6:43am

Genetics: Potassium channel function linked to autism and epilepsy.

Nat Rev Neurol. 2014 Feb 25;

Authors:

PMID: 24567004 [PubMed - as supplied by publisher]

The developmental transcriptome of the human brain: implications for neurodevelopmental disorders.

February 26, 2014 - 6:43am

The developmental transcriptome of the human brain: implications for neurodevelopmental disorders.

Curr Opin Neurol. 2014 Feb 22;

Authors: Tebbenkamp AT, Willsey AJ, State MW, Sestan N

Abstract
PURPOSE OF REVIEW: Recent characterizations of the transcriptome of the developing human brain by several groups have generated comprehensive datasets on coding and noncoding RNAs that will be instrumental for illuminating the underlying biology of complex neurodevelopmental disorders. This review summarizes recent studies successfully utilizing these data to increase our understanding of the molecular mechanisms of pathogenesis.
RECENT FINDINGS: Several approaches have successfully integrated developmental transcriptome data with gene discovery to generate testable hypotheses about when and where in the developing human brain disease-associated genes converge. Specifically, these include the projection neurons in the prefrontal and primary motor--somatosensory cortex during mid-fetal development in autism spectrum disorder and the frontal cortex during fetal development in schizophrenia.
SUMMARY: Developmental transcriptome data is a key to interpreting disease-associated mutations and transcriptional changes. Novel approaches integrating the spatial and temporal dimensions of these data have increased our understanding of when and where disease occurs. Refinement of spatial and temporal properties and expanding these findings to other neurodevelopmental disorders will provide critical insights for understanding disease biology.

PMID: 24565942 [PubMed - as supplied by publisher]

Oxytocin-mediated GABA inhibition during delivery attenuates autism pathogenesis in rodent offspring.

February 26, 2014 - 6:43am
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Oxytocin-mediated GABA inhibition during delivery attenuates autism pathogenesis in rodent offspring.

Science. 2014 Feb 7;343(6171):675-9

Authors: Tyzio R, Nardou R, Ferrari DC, Tsintsadze T, Shahrokhi A, Eftekhari S, Khalilov I, Tsintsadze V, Brouchoud C, Chazal G, Lemonnier E, Lozovaya N, Burnashev N, Ben-Ari Y

Abstract
We report that the oxytocin-mediated neuroprotective γ-aminobutyric acid (GABA) excitatory-inhibitory shift during delivery is abolished in the valproate and fragile X rodent models of autism. During delivery and subsequently, hippocampal neurons in these models have elevated intracellular chloride levels, increased excitatory GABA, enhanced glutamatergic activity, and elevated gamma oscillations. Maternal pretreatment with bumetanide restored in offspring control electrophysiological and behavioral phenotypes. Conversely, blocking oxytocin signaling in naïve mothers produced offspring having electrophysiological and behavioral autistic-like features. Our results suggest a chronic deficient chloride regulation in these rodent models of autism and stress the importance of oxytocin-mediated GABAergic inhibition during the delivery process. Our data validate the amelioration observed with bumetanide and oxytocin and point to common pathways in a drug-induced and a genetic rodent model of autism.

PMID: 24503856 [PubMed - indexed for MEDLINE]

Neuroscience. Could autism be treated prenatally?

February 26, 2014 - 6:43am
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Neuroscience. Could autism be treated prenatally?

Science. 2014 Feb 7;343(6171):620-1

Authors: Zimmerman AW, Connors SL

PMID: 24503843 [PubMed - indexed for MEDLINE]

Chromosomal microarray analysis of consecutive individuals with autism spectrum disorders or learning disability presenting for genetic services.

February 26, 2014 - 6:43am
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Chromosomal microarray analysis of consecutive individuals with autism spectrum disorders or learning disability presenting for genetic services.

Gene. 2014 Feb 1;535(1):70-8

Authors: Roberts JL, Hovanes K, Dasouki M, Manzardo AM, Butler MG

Abstract
Chromosomal microarray analysis is now commonly used in clinical practice to identify copy number variants (CNVs) in the human genome. We report our experience with the use of the 105 K and 180K oligonucleotide microarrays in 215 consecutive patients referred with either autism or autism spectrum disorders (ASD) or developmental delay/learning disability for genetic services at the University of Kansas Medical Center during the past 4 years (2009-2012). Of the 215 patients [140 males and 75 females (male/female ratio=1.87); 65 with ASD and 150 with learning disability], abnormal microarray results were seen in 45 individuals (21%) with a total of 49 CNVs. Of these findings, 32 represented a known diagnostic CNV contributing to the clinical presentation and 17 represented non-diagnostic CNVs (variants of unknown significance). Thirteen patients with ASD had a total of 14 CNVs, 6 CNVs recognized as diagnostic and 8 as non-diagnostic. The most common chromosome involved in the ASD group was chromosome 15. For those with a learning disability, 32 patients had a total of 35 CNVs. Twenty-six of the 35 CNVs were classified as a known diagnostic CNV, usually a deletion (n=20). Nine CNVs were classified as an unknown non-diagnostic CNV, usually a duplication (n=8). For the learning disability subgroup, chromosomes 2 and 22 were most involved. Thirteen out of 65 patients (20%) with ASD had a CNV compared with 32 out of 150 patients (21%) with a learning disability. The frequency of chromosomal microarray abnormalities compared by subject group or gender was not statistically different. A higher percentage of individuals with a learning disability had clinical findings of seizures, dysmorphic features and microcephaly, but not statistically significant. While both groups contained more males than females, a significantly higher percentage of males were present in the ASD group.

PMID: 24188901 [PubMed - indexed for MEDLINE]

Genetic variation in dopamine-related gene expression influences motor skill learning in mice.

February 26, 2014 - 6:43am
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Genetic variation in dopamine-related gene expression influences motor skill learning in mice.

Genes Brain Behav. 2013 Aug;12(6):604-14

Authors: Qian Y, Chen M, Forssberg H, Diaz Heijtz R

Abstract
Several neurodevelopmental disorders with a strong genetic basis, including attention-deficit/hyperactivity disorder, autism spectrum disorders and developmental coordination disorder, involve deficits in fine motor skills. This phenotype may depend on heritable variation in components of the dopamine (DA) system, which is known to play a critical role in motor skill learning. In this study, we took advantage of two inbred strains of mice (BALB/c and C57BL/6) that differ markedly in the number of midbrain DA neurons in order to investigate the influence of such naturally occurring genetic variation on the acquisition and performance of fine motor skills. Gene expression analysis of midbrain, frontal cortex and striatum showed significant differences in the expression of presynaptic and postsynaptic dopaminergic (DAergic) markers (e.g. tyrosine hydroxylase, DA transporter, DA D4 receptor, DA D5 receptor and DARPP-32) between these two strains. BALB/c mice had lower learning rate and performance scores in a complex skilled reaching task when compared with C57BL/6 mice. A negative correlation was found between the motor learning rate and level of DARPP-32 mRNA expression in the frontal cortex contralateral to the trained forelimb. The rate of motor learning was also negatively correlated with the levels of DARPP-32 and DA D1 receptor mRNAs in the striatum. Our results suggest that genetically driven variation in frontostriatal DAergic neurotransmission is a major contributor to individual differences in motor skill learning. Moreover, these findings implicate the D1R/cAMP/DARPP-32 signaling pathway in those neurodevelopmental disorders that are associated with fine motor skill deficits.

PMID: 23819855 [PubMed - indexed for MEDLINE]

Improved spatial learning is associated with increased hippocampal but not prefrontal long-term potentiation in mGluR4 knockout mice.

February 26, 2014 - 6:43am
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Improved spatial learning is associated with increased hippocampal but not prefrontal long-term potentiation in mGluR4 knockout mice.

Genes Brain Behav. 2013 Aug;12(6):615-25

Authors: Iscru E, Goddyn H, Ahmed T, Callaerts-Vegh Z, D'Hooge R, Balschun D

Abstract
Although much information about metabotropic glutamate receptors (mGluRs) and their role in normal and pathologic brain function has been accumulated during the last decades, the role of group III mGluRs is still scarcely documented. Here, we examined mGluR4 knockout mice for types of behavior and synaptic plasticity that depend on either the hippocampus or the prefrontal cortex (PFC). We found improved spatial short- and long-term memory in the radial arm maze, which was accompanied by enhanced long-term potentiation (LTP) in hippocampal CA1 region. In contrast, LTP in the PFC was unchanged when compared with wild-type controls. Changes in paired-pulse facilitation that became overt in the presence of the GABAA antagonist picrotoxin indicated a function of mGluR4 in maintaining the excitation/inhibition balance, which is of crucial importance for information processing in the brain and the deterioration of these processes in neuropsychological disorders such as autism, epilepsy and schizophrenia.

PMID: 23714430 [PubMed - indexed for MEDLINE]

An EJC factor RBM8a regulates anxiety behaviors.

February 26, 2014 - 6:43am
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An EJC factor RBM8a regulates anxiety behaviors.

Curr Mol Med. 2013 Jul;13(6):887-99

Authors: Alachkar A, Jiang D, Harrison M, Zhou Y, Chen G, Mao Y

Abstract
Neuroplasticity depends on the precise timing of gene expression, which requires accurate control of mRNA stability and rapid elimination of abnormal mRNA. Nonsense-mediated mRNA decay (NMD) is an RNA surveillance mechanism that ensures the speedy degradation of mRNAs carrying premature termination codons (PTCs). This mechanism relies on several key Exon Junction Complex (EJC) factors to distinguish PTCs from normal stop codons. NMD degrades not only aberrant transcripts carrying PTCs, but also normal transcripts harboring a normal stop codon [1]. Intriguingly, mutations in an NMD factor, Upf3b, have been found in patients with autism [2, 3]. A binding partner of Upf3b, RBM8a, is located in the 1q21.1 copy-number variation (CNV) associated with mental retardation, autism [4], schizophrenia [5], and microcephaly [6]. However, the functions of EJC factors and their roles in behavioral regulation are still elusive. RBM8a protein is a core component of the EJC that plays an important role in NMD. Recent genetic study indicated that RBM8a gain-of-function significantly associated with intellectual disability [7]. In this study we investigated the effect of RBM8a overexpression on affective behaviors in mice. Lentivirus expressing RBM8a was infused into the hippocampus of adult mice to conduct behavioral studies including social interaction, open field, elevated plus maze, and forced swimming tests. Our results showed that overexpression of RBM8a in the mouse dentate gyrus (DG) leads to increased anxiety-like behavior, abnormal social interaction and decreased immobile time in forced swimming test (FST). To examine the underlying mechanism, we found that overexpressing RBM8a in cultured primary neurons lead to significant higher frequency of miniature excitatory postsynaptic currents (mEPSCs). To explore the underlying mechanism of RBM8a mediated behavioral changes, RNA-immunoprecipitation (RNA-IP) detected that RBM8a binds to CaMK2, GluR1 and Egr1 mRNA, suggesting that RBM8a may target neuronal genes to regulate behaviors. This is the first study that demonstrates the key role of RBM8a on the emotional behaviors in mice. These results reveal new neural mechanisms by which NMD modulates behaviors and potentially provide a better understanding of pathophysiology underlying psychiatric disorders.

PMID: 23638902 [PubMed - indexed for MEDLINE]

Absence of substantial copy number differences in a pair of monozygotic twins discordant for features of autism spectrum disorder.

February 25, 2014 - 6:28am

Absence of substantial copy number differences in a pair of monozygotic twins discordant for features of autism spectrum disorder.

Case Rep Genet. 2014;2014:516529

Authors: Laplana M, Royo JL, Aluja A, López R, Heine-Sunyer D, Fibla J

Abstract
Autism spectrum disorder (ASD) is a highly heritable disease (~0.9) with a complex genetic etiology. It is initially characterized by altered cognitive ability which commonly includes impaired language and communication skills as well as fundamental deficits in social interaction. Despite the large amount of studies described so far, the high clinical diversity affecting the autism phenotype remains poorly explained. Recent studies suggest that rare genomic variations, in particular copy number variation (CNV), may account for a significant proportion of the genetic basis of ASD. The use of disease-discordant monozygotic twins represents a powerful strategy to identify de novo and inherited CNV in the disorder. Here we present the results of a comparative genome hybridization (CGH) analysis with a pair of monozygotic twins affected of ASD with significant differences in their clinical manifestations that specially affect speech language impairment and communication skills. Array CGH was performed in three different tissues: blood, saliva, and hair follicle, in an attempt to identify germinal and somatic CNV regions that may explain these differences. Our results argue against a role of large CNV rearrangements as a molecular etiology of the observed differences. This forwards future research to explore de novo point mutation and epigenomic alterations as potential explanations of the observed clinical differences.

PMID: 24563798 [PubMed]

Post-transcriptional Regulation of the Creatine Transporter Gene: Functional Relevance of Alternative Splicing.

February 25, 2014 - 6:28am

Post-transcriptional Regulation of the Creatine Transporter Gene: Functional Relevance of Alternative Splicing.

Biochim Biophys Acta. 2014 Feb 20;

Authors: Ndika JD, Martinez-Munoz C, Anand N, van Dooren SJ, Kanhai W, Smith DE, Jakobs C, Salomons GS

Abstract
BACKGROUND: Aberrations in about 10-15% of X-chromosome genes account for intellectual disability (ID); with a prevalence of 1-3% (Gécz et al., 2009 [1]). The SLC6A8 gene, mapped to Xq28, encodes the creatine transporter (CTR1). Mutations in SLC6A8, and the ensuing decrease in brain creatine, lead to co-occurrence of; speech/language delay, autism-like behaviours and epilepsy with ID. A splice variant of SLC6A8 - SLC6A8C, containing intron 4 and exons 5-13, was identified. Herein, we report the identification of a novel variant - SLC6A8D, and functional relevance of these isoforms.
METHODS: Via (quantitative)RT-PCR, uptake assays, and confocal microscopy, we investigated their expression and function vis-à-vis creatine transport.
RESULTS: SLC6A8D is homologous to SLC6A8C except for a deletion of exon 9 (without occurrence of a frame shift). Both contain an open reading frame encoding a truncated protein but otherwise identical to CTR1. Like SLC6A8, both variants are predominantly expressed in tissues with high energy requirement. Our experiments reveal that these truncated isoforms do not transport creatine. However, in SLC6A8 (CTR1)-overexpressing cells, a subsequent infection (transduction) with viral constructs encoding either the SLC6A8C (CTR4) or SLC6A8D (CTR5) isoform resulted in a significant increase in creatine accumulation compared to CTR1 cells re-infected with viral constructs containing the empty vector. Moreover, transient transfection of CTR4 or CTR5 into HEK293 cells resulted in significantly higher creatine uptake.
CONCLUSIONS: CTR4 and CTR5 are possible regulators of the creatine transporter since their overexpression results in upregulated CTR1 protein and creatine uptake.
GENERAL SIGNIFICANCE: Provides added insight into the mechanism(s) of creatine transport regulation.

PMID: 24561156 [PubMed - as supplied by publisher]

Long-lasting effects of minocycline on behavior in young but not adult Fragile X mice.

February 25, 2014 - 6:28am
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Long-lasting effects of minocycline on behavior in young but not adult Fragile X mice.

Neuroscience. 2013 Aug 29;246:186-98

Authors: Dansie LE, Phommahaxay K, Okusanya AG, Uwadia J, Huang M, Rotschafer SE, Razak KA, Ethell DW, Ethell IM

Abstract
Fragile X Syndrome (FXS) is the most common single-gene inherited form of intellectual disability with behaviors characteristic of autism. People with FXS display childhood seizures, hyperactivity, anxiety, developmental delay, attention deficits, and visual-spatial memory impairment, as well as a propensity for obsessive-compulsive disorder. Several of these aberrant behaviors and FXS-associated synaptic irregularities also occur in "fragile X mental retardation gene" knock-out (Fmr1 KO) mice. We previously reported that minocycline promotes the maturation of dendritic spines - postsynaptic sites for excitatory synapses - in the developing hippocampus of Fmr1 KO mice, which may underlie the beneficial effects of minocycline on anxiolytic behavior in young Fmr1 KO mice. In this study, we compared the effectiveness of minocycline treatment in young and adult Fmr1 KO mice, and determined the dependence of behavioral improvements on short-term versus long-term minocycline administration. We found that 4- and 8-week-long treatments significantly reduced locomotor activity in both young and adult Fmr1 KO mice. Some behavioral improvements persisted in young mice post-treatment, but in adults the beneficial effects were lost soon after minocycline treatment was stopped. We also show, for the first time, that minocycline treatment partially attenuates the number and severity of audiogenic seizures in Fmr1 KO mice. This report provides further evidence that minocycline treatment has immediate and long-lasting benefits on FXS-associated behaviors in the Fmr1 KO mouse model.

PMID: 23660195 [PubMed - indexed for MEDLINE]

GFAP expression and social deficits in transgenic mice overexpressing human sAPPα.

February 22, 2014 - 8:36am
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GFAP expression and social deficits in transgenic mice overexpressing human sAPPα.

Glia. 2013 Sep;61(9):1556-69

Authors: Bailey AR, Hou H, Song M, Obregon DF, Portis S, Barger S, Shytle D, Stock S, Mori T, Sanberg PG, Murphy T, Tan J

Abstract
Autistic individuals display impaired social interactions and language, and restricted, stereotyped behaviors. Elevated levels of secreted amyloid precursor protein-alpha (sAPPα), the product of α-secretase cleavage of APP, are found in the plasma of some individuals with autism. The sAPPα protein is neurotrophic and neuroprotective and recently showed a correlation to glial differentiation in human neural stem cells (NSCs) via the IL-6 pathway. Considering evidence of gliosis in postmortem autistic brains, we hypothesized that subsets of patients with autism would exhibit elevations in CNS sAPPα and mice generated to mimic this observation would display markers suggestive of gliosis and autism-like behavior. Elevations in sAPPα levels were observed in brains of autistic patients compared to controls. Transgenic mice engineered to overexpress human sAPPα (TgsAPPα mice) displayed hypoactivity, impaired sociability, increased brain glial fibrillary acidic protein (GFAP) expression, and altered Notch1 and IL-6 levels. NSCs isolated from TgsAPPα mice, and those derived from wild-type mice treated with sAPPα, displayed suppressed β-tubulin III and elevated GFAP expression. These results suggest that elevations in brain sAPPα levels are observed in subsets of individuals with autism and TgsAPPα mice display signs suggestive of gliosis and behavioral impairment.

PMID: 23840007 [PubMed - indexed for MEDLINE]

Identification of small exonic CNV from whole-exome sequence data and application to autism spectrum disorder.

February 20, 2014 - 7:37am
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Identification of small exonic CNV from whole-exome sequence data and application to autism spectrum disorder.

Am J Hum Genet. 2013 Oct 3;93(4):607-19

Authors: Poultney CS, Goldberg AP, Drapeau E, Kou Y, Harony-Nicolas H, Kajiwara Y, De Rubeis S, Durand S, Stevens C, Rehnström K, Palotie A, Daly MJ, Ma'ayan A, Fromer M, Buxbaum JD

Abstract
Copy number variation (CNV) is an important determinant of human diversity and plays important roles in susceptibility to disease. Most studies of CNV carried out to date have made use of chromosome microarray and have had a lower size limit for detection of about 30 kilobases (kb). With the emergence of whole-exome sequencing studies, we asked whether such data could be used to reliably call rare exonic CNV in the size range of 1-30 kilobases (kb), making use of the eXome Hidden Markov Model (XHMM) program. By using both transmission information and validation by molecular methods, we confirmed that small CNV encompassing as few as three exons can be reliably called from whole-exome data. We applied this approach to an autism case-control sample (n = 811, mean per-target read depth = 161) and observed a significant increase in the burden of rare (MAF ≤1%) 1-30 kb CNV, 1-30 kb deletions, and 1-10 kb deletions in ASD. CNV in the 1-30 kb range frequently hit just a single gene, and we were therefore able to carry out enrichment and pathway analyses, where we observed enrichment for disruption of genes in cytoskeletal and autophagy pathways in ASD. In summary, our results showed that XHMM provided an effective means to assess small exonic CNV from whole-exome data, indicated that rare 1-30 kb exonic deletions could contribute to risk in up to 7% of individuals with ASD, and implicated a candidate pathway in developmental delay syndromes.

PMID: 24094742 [PubMed - indexed for MEDLINE]

Transmission disequilibrium of small CNVs in simplex autism.

February 20, 2014 - 7:37am
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Transmission disequilibrium of small CNVs in simplex autism.

Am J Hum Genet. 2013 Oct 3;93(4):595-606

Authors: Krumm N, O'Roak BJ, Karakoc E, Mohajeri K, Nelson B, Vives L, Jacquemont S, Munson J, Bernier R, Eichler EE

Abstract
We searched for disruptive, genic rare copy-number variants (CNVs) among 411 families affected by sporadic autism spectrum disorder (ASD) from the Simons Simplex Collection by using available exome sequence data and CoNIFER (Copy Number Inference from Exome Reads). Compared to high-density SNP microarrays, our approach yielded ∼2× more smaller genic rare CNVs. We found that affected probands inherited more CNVs than did their siblings (453 versus 394, p = 0.004; odds ratio [OR] = 1.19) and that the probands' CNVs affected more genes (921 versus 726, p = 0.02; OR = 1.30). These smaller CNVs (median size 18 kb) were transmitted preferentially from the mother (136 maternal versus 100 paternal, p = 0.02), although this bias occurred irrespective of affected status. The excess burden of inherited CNVs among probands was driven primarily by sibling pairs with discordant social-behavior phenotypes (p < 0.0002, measured by Social Responsiveness Scale [SRS] score), which contrasts with families where the phenotypes were more closely matched or less extreme (p > 0.5). Finally, we found enrichment of brain-expressed genes unique to probands, especially in the SRS-discordant group (p = 0.0035). In a combined model, our inherited CNVs, de novo CNVs, and de novo single-nucleotide variants all independently contributed to the risk of autism (p < 0.05). Taken together, these results suggest that small transmitted rare CNVs play a role in the etiology of simplex autism. Importantly, the small size of these variants aids in the identification of specific genes as additional risk factors associated with ASD.

PMID: 24035194 [PubMed - indexed for MEDLINE]

Letting a typical mouse judge whether mouse social interactions are atypical.

February 20, 2014 - 7:37am
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Letting a typical mouse judge whether mouse social interactions are atypical.

Autism Res. 2013 Jun;6(3):212-20

Authors: Shah CR, Forsberg CG, Kang JQ, Veenstra-VanderWeele J

Abstract
Diagnosis of an autism spectrum disorder (ASD) requires a qualitative assessment of social aptitude: one person judging whether another person interacts in a "typical" way. We hypothesized that mice could be used to make a similar judgment if they prefer "typical" over "atypical" social interactions with mouse models relevant to ASD. We used wild-type C57BL/6 (B6) mice as "judges" and evaluated their preference for a chamber containing a "typical" (B6 or 129S6) or an "atypical" mouse. For our atypical mouse stimuli, we chose two inbred strains with well-documented social phenotypes (BTBR and BALB/c), as well a mutant line with abnormal social behavior and seizures (Gabrb3 +/-). Overall, we observed a stimulus by time interaction (P < 0.0001), with B6 mice preferring the typical mouse chamber during the last 10 min of the 30-min test. For two of the individual stimulus pairings, we observed a similar chamber by time interaction (BALB/c vs. 129S6, P = 0.0007; Gabrb3 +/- vs. 129S6, P = 0.033). For the third stimulus pairing, we found a trend for preference of the typical mouse across time (BTBR vs. B6, P = 0.051). We repeated the experiments using 129S6 mice as judges and found a significant overall interaction (P = 0.034), but only one stimulus pairing reached significance on its own (BALB/c vs. 129S6, P = 0.0021). These data suggest that a characteristic pattern of exploration in B6 mice can distinguish some socially atypical animals from controls.

PMID: 23436806 [PubMed - indexed for MEDLINE]

Replication of linkage at chromosome 20p13 and identification of suggestive sex-differential risk loci for autism spectrum disorder.

February 19, 2014 - 7:09am

Replication of linkage at chromosome 20p13 and identification of suggestive sex-differential risk loci for autism spectrum disorder.

Mol Autism. 2014 Feb 17;5(1):13

Authors: Werling DM, Lowe JK, Luo R, Cantor RM, Geschwind DH

Abstract
BACKGROUND: Autism spectrum disorders (ASDs) are male-biased and genetically heterogeneous. While sequencing of sporadic cases has identified de novo risk variants, the heritable genetic contribution and mechanisms driving the male bias are less understood. Here, we aimed to identify familial and sex-differential risk loci in the largest available, uniformly ascertained, densely genotyped sample of multiplex ASD families from the Autism Genetics Resource Exchange (AGRE), and to compare results with earlier findings from AGRE.
METHODS: From a total sample of 1,008 multiplex families, we performed genome-wide, non-parametric linkage analysis in a discovery sample of 847 families, and separately on subsets of families with only male, affected children (male-only, MO) or with at least one female, affected child (female-containing, FC). Loci showing evidence for suggestive linkage (logarithm of odds >=2.2) in this discovery sample, or in previous AGRE samples, were re-evaluated in an extension study utilizing all 1,008 available families. For regions with genome-wide significant linkage signal in the discovery stage, those families not included in the corresponding discovery sample were then evaluated for independent replication of linkage. Association testing of common single nucleotide polymorphisms (SNPs) was also performed within suggestive linkage regions.
RESULTS: We observed an independent replication of previously observed linkage at chromosome 20p13 (P < 0.01), while loci at 6q27 and 8q13.2 showed suggestive linkage in our extended sample. Suggestive sex-differential linkage was observed at 1p31.3 (MO), 8p21.2 (FC), and 8p12 (FC) in our discovery sample, and the MO signal at 1p31.3 was supported in our expanded sample. No sex-differential signals met replication criteria, and no common SNPs were significantly associated with ASD within any identified linkage regions.
CONCLUSIONS: With few exceptions, analyses of subsets of families from the AGRE cohort identify different risk loci, consistent with extreme locus heterogeneity in ASD. Large samples appear to yield more consistent results, and sex-stratified analyses facilitate the identification of sex-differential risk loci, suggesting that linkage analyses in large cohorts are useful for identifying heritable risk loci. Additional work, such as targeted re-sequencing, is needed to identify the specific variants within these loci that are responsible for increasing ASD risk.

PMID: 24533643 [PubMed - as supplied by publisher]

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