Project description:Autism Spectrum Disorder (ASD) is a neurodevelopmental condition which is defined by decreased social communication and the presence of repetitive or stereotypic behaviors. Recent evidence has suggested that the gut-brain axis may be important in neurodevelopment in general and may play a role in ASD in particular. Here, we present a study of the gut microbiome in 96 individuals diagnosed with ASD in Israel, compared to 42 neurotypical individuals. We determined differences in alpha and beta diversity in the microbiome of individuals with ASD and demonstrated that the phylum Bacteroidetes and genus Bacteroides were the most significantly over-represented in individuals with ASD. To understand the possible functional significance of these changes, we treated newborn mice with Bacteroides fragilis at birth. B. fragilis-treated male mice displayed social behavior dysfunction, increased repetitive behaviors and gene expression dysregulation in the prefrontal cortex, while female mice did not display behavioral deficits. These findings suggest that overabundance of Bacteroides, particularly in early life, may have functional consequences for individuals with ASD.
Project description:Autism Spectrum Disorder (ASD) is a neurodevelopmental condition which is defined by decreased social communication and the presence of repetitive or stereotypic behaviors. Recent evidence has suggested that the gut-brain axis may be important in neurodevelopment in general and may play a role in ASD in particular. Here, we present a study of the gut microbiome in 96 individuals diagnosed with ASD in Israel, compared to 42 neurotypical individuals. We determined differences in alpha and beta diversity in the microbiome of individuals with ASD and demonstrated that the phylum Bacteroidetes and genus Bacteroides were the most significantly over-represented in individuals with ASD. To understand the possible functional significance of these changes, we treated newborn mice with Bacteroides fragilis at birth. B. fragilis-treated male mice displayed social behavior dysfunction, increased repetitive behaviors, and gene expression dysregulation in the prefrontal cortex, while female mice did not display behavioral deficits. These findings suggest that overabundance of Bacteroides, particularly in early life, may have functional consequences for individuals with ASD.
Project description:Autism spectrum disorder (ASD) manifests as alterations in complex human behaviors including social communication and stereotypies. In addition to genetic risks, the gut microbiome differs between typically-developing (TD) and ASD individuals, though it remains unclear whether the microbiome contributes to symptoms. We transplanted gut microbiota from human donors with ASD and TD controls into germ-free mice, and reveal that colonization with ASD microbiota was sufficient to induce hallmark autistic behaviors. The brains of mice colonized with ASD microbiota display alternative splicing of ASD-relevant genes. Microbiome and metabolome profiles of mice harboring human microbiota predict that specific bacterial taxa and their metabolites modulate ASD behaviors. Indeed, treatment of an ASD mouse model with candidate microbial metabolites improves behavioral abnormalities and affects neuronal excitability in the brain. We propose that the gut microbiome modulates behaviors in mice via production of neuroactive metabolites, suggesting that gut-brain connections contribute to the pathophysiology of ASD.
Project description:Multiple human autism risk genes are predicted to converge on the β‐catenin (β‐cat)/Wnt pathway. However, direct tests to link β‐cat up‐ or down‐regulation with autism are largely lacking, and the associated pathophysiological changes are poorly defined. Here we identify excessive β‐cat as a risk factor that causes expression changes in several genes relevant to human autism. Our studies utilize mouse lines with β‐cat dysregulation in forebrain excitatory neurons, identified as cell types with convergent expression of autism‐linked genes in both human and mouse brains. We show that mice expressing excessive β‐cat display behavioral and molecular changes, including decreased social interest, increased repetitive behaviors, reduced parvalbumin and altered expression levels of additional genes identified as potential risk factors for human autism. These behavioral and molecular phenotypes are averted by reducing β‐cat in neurons predisposed by gene mutations to express elevated β‐cat. Using next-generation sequencing of the prefrontal cortex, we identify dysregulated genes that are shared between mouse lines with excessive β‐cat and autism‐like behaviors, but not mouse lines with reduced β‐cat and normal social behavior. Our findings provide critical new insights into β‐cat, Wnt pathway dysregulation in the brain causing behavioral phenotypes relevant to the disease and the molecular etiology which includes several human autism risk genes.
Project description:Mutations in the gene encoding the chromodomain helicase DNA-binding protein 8 (CHD8) are strongly associated with autism spectrum disorder (ASD). Although duplications of the locus spanning CHD8 are also found in individuals with neurodevelopmental disorders, the role of CHD8 duplication in clinical phenotypes and the underlying mechanisms have remained unknown. Here we show that mice with Chd8 overexpression modeling human CHD8 duplication manifest growth retardation, microcephaly, and behavioral abnormalities including hyperactivity and reduced anxiety-like behavior. Chd8 overexpression results in alterations of transcription and chromatin accessibility of genes involved in neurogenesis that are associated with aberrant binding of CHD8 to enhancer regions and impairs differentiation of deep-layer neurons. Furthermore, genetic and pharmacological interventions rescue hyperactive behavior of Chd8 overexpression mice. Our results thus indicate that Chd8 overexpression mice recapitulate key features of CHD8 duplication syndrome, and they provide insight into cellular and molecular pathogenesis underlying neurodevelopmental disorders.
Project description:Analysis of the Bacteroides thetaiotaomicron(BT) transcriptome during co-culture with Caco-2 intestinal epithelial cells To identify potential bacterial protein(s) involved in the anti-inflammatory effect of BT in colitis, BT was incubated with Caco-2 human intestinal epithelial cells for 2 hours, and bacterial gene expression was assessed on a Bacteroides thetaiotaomicron VPI-5482 specific microarray. Forty-three BT genes were up-regulated by five-fold or more and of these, twenty genes encoded hypothetical proteins.
Project description:Purpose: Examining the transcriptome of Bacteroides thetaiotaomicron VPI-5482 challenged with Bacteroides phage to assess surface molecule expression changes Methods: Bacteroides thetaiotaomicron was grown in BPRM in vitro or Germ-Free mice were monocolonized with Bacteroides thetaiotaomicron and gavaged with ARB25 phage. Fold change was calculated as live phage versus heat-killed phage treated samples with n=3 biological replicates. Once cells reached an optical density corresponding to mid-log phase growth (absorbance between 0.4-0.5), RNA was isolated and rRNA depleted. Samples were multiplexed for sequencing on the Illumina HiSeq platform at the University of Michigan Sequencing Core. Data was analyzed using Arraystar software (DNASTAR, Inc.) using DEseq2 normalization with default parameters. Genes with significant up- or down-regulation were determined by the following criteria: genes with an average fold-change >5-fold and with at least 2/3 biological replicates with a normalized expression level >1% of the overall average, and a p-value < 0.05 (t test with Benjamini-Hochberg correction) Results: Specific capsule expression was increased in wild-type B. thetaiotaomicron during phage infection in vitro and in vivo. Many corresponding in vivo genes were upregulated as well as other surface layer proteins.
Project description:Mutations in the gene encoding the chromodomain helicase DNA-binding protein 8 (CHD8) are strongly associated with autism spectrum disorder (ASD). Although duplications of the locus spanning CHD8 are also found in individuals with neurodevelopmental disorders, the role of CHD8 duplication in clinical phenotypes and the underlying mechanisms have remained unknown. Here we show that mice with Chd8 overexpression modeling human CHD8 duplication manifest growth retardation, microcephaly, and behavioral abnormalities including hyperactivity and reduced anxiety-like behavior. Chd8 overexpression results in alterations of transcription and chromatin accessibility of genes involved in neurogenesis that are associated with aberrant binding of CHD8 to enhancer regions and impairs differentiation of deep-layer neurons. Furthermore, genetic and pharmacological interventions rescue hyperactive behavior of Chd8 overexpression mice. Our results thus indicate that Chd8 overexpression mice recapitulate key features of CHD8 duplication syndrome, and they provide insight into cellular and molecular pathogenesis underlying neurodevelopmental disorders.