Project description:A causal role of mutations in genes encoding for multiple general transcription factors in neurodevelopmental disorders including autism suggested that alterations at the global level of gene expression regulation might also relate to disease risk in sporadic cases of autism. This premise can be tested by evaluating for global changes in the overall distribution of gene expression levels. For instance, in mice, we recently showed that variability in hippocampal-dependent behaviors was associated with variability in the pattern of the overall distribution of gene expression levels, as assessed by variance in the distribution of gene expression levels in the hippocampus. We hypothesized that a similar change in the variance in gene expression levels might be found in children with autism. Gene expression microarrays covering greater than 47,000 unique RNA transcripts were done on purified RNA from peripheral blood lymphocytes of children with autism (n=82) and controls (n=64). The variance in the distribution of gene expression levels from each microarray was compared between groups of children. Also tested was whether a risk factor for autism, increased paternal age, was associated with variance in the overall distribution of gene expression levels. A decrease in the variance in the distribution of gene expression levels in peripheral blood lymphocytes (PBL) was associated with the diagnosis of autism and a risk factor for autism, increased paternal age. Traditional approaches to microarray analysis of gene expression suggested a possible mechanism for decreased variance in gene expression. Gene expression pathways involved in transcriptional regulation were down-regulated in the blood of children with autism and children of older fathers. Thus, results from global and gene specific approaches to studying microarray data were complimentary and supported the hypothesis that alterations at the global level of gene expression regulation are related to autism and increased paternal age. Regulation of transcription, thus, represents a possible point of convergence for multiple etiologies of autism and other neurodevelopmental disorders.

Project description:All subjects were recruited at Centennial Women?s Hospital and the Perinatal Research Center in Nashville, TN beginning in 2003. Pregnant women were enrolled during their first clinical visit after obtaining informed consent as described previously. Demographic and clinical data specific to the fetus was collected from clinical records. Gestational age of the neonate was determined by maternal reporting of the last menstrual period and corroboration by ultrasound dating. Accurate knowledge of gestational age (GA) is essential for proper monitoring and care of neonates. However, accurate GA measures are often not available. DNA methylation has previously been shown to associate with GA, and has been used to accurately predict chronological age in adults. In the current study, we examine whether DNA methylation in cord blood can be used to predict gestational age at birth. Results: We found that GA can be accurately predicted from DNA methylation of neonatal cord blood and blood spot samples (DNAm GA), using 148 CpG sites selected through elastic net regression in six training datasets (N=207). We evaluated predictive accuracy in six testing datasets (N=1,202), and found that the accuracy of DNAm GA meets or exceeds accuracy of gestational age estimates based on established methods. We also found an increased DNAm GA, relative to clinical GA, was associated with increased birthweight percentile (p=.00057), adjusting for GA, sex, and ancestry, suggesting that DNAm GA could represent developmental age more accurately than clinical estimates of GA. Conclusions: Further development of this predictor could provide a method of accurate neonatal estimation of GA for use in resource-limited populations, or in cases where GA cannot be estimated clinically. When clinical estimates are available, the predictor can be used to test hypotheses related to developmental age and other early life circumstances, and may provide increased accuracy beyond clinical estimates. 36 Umbilical cord blood samples were collected in EDTA tubes soon after placental delivery. Blood samples were centrifuged at 3,000 RPM to separate plasma, and buffy coats were aliquoted and stored at -80oC. DNA was extracted using the DNeasy Kit (Qiagen). DNA methylation was interrogated for each sample using the HumanMethylation450 BeadChip (Illumina).

Project description:The offspring of older fathers have an increased risk of neurodevelopmental disorders such as schizophrenia and autism. It has been proposed that de novo point mutations and copy number variants (CNVs) in the continually dividing spermatogonia underlie this association. In light of the evidence implicating CNVs with schizophrenia and autism, here we use a mouse model to test the hypothesis that the offspring of older males have an increased risk of de novo CNVs. Three-month-old and fourteen- to sixteen-month-old C57BL/6J sires were mated with three-month-old dams to create control offspring and offspring of old sires, respectively. Applying genome-wide microarray screening technology, seven distinct CNVs were identified in a discovery set of twelve offspring and their parents. Competitive quantitative PCR was employed to confirm the variants and establish their frequency in a replication set of 77 offspring and their parents. Six de novo CNVs were detected in the offspring of older sires, while none were detected in the control group. One of the de novo CNVs involved Auts2 (autism susceptibility candidate 2), and other CNVs included genes linked to schizophrenia, autism and brain development. Two of the CNVs were associated with behavioural and/or neuroanatomical phenotypic features. This is the first experimental demonstration that the offspring of older males have more de novo CNVs. The results suggest that offspring of older fathers may be at increased risk of neurodevelopmental disorders such as schizophrenia and autism via the generation of de novo CNV in the male germline. In light of the trends for delayed parenthood in many societies, and in light of the potential for these CNVs to accumulate over subsequent generations, the impact of these mechanisms on the health of future generations warrants closer scrutiny. 2 sires of advanced paternal age (12-16 months of age) and 2 control (3 months of age) sires were mated to dams (3 months of age) to create 6 offspring of advanced paternal age (APA) and 6 control offspring (C), respectively, with an even number of sexes within each group of offspring. A commerical aCGH and a custom CNV array (both supplied by Agilent) were used in combination to detect copy number variations in the genomes of the offspring and their parents. DNA from all male animals was hybridized against a male reference animal and that from all female animals against a female reference animal.

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Placental transcriptomic pattern of murine advanced paternal age model of autism

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