Prenatal stress-induced programming of genome-wide promoter DNA methylation in 5-Htt deficient mice
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ABSTRACT: The serotonin transporter (5-HTT) gene-linked polymorphic region has been suggested to play a modulatory role in mediating the effects of early-life stress on psychopathology rendering carriers of the low-expression short (s)-allele more vulnerable to environmental adversity in later life. Here we analyzed the effects of prenatal stress (PS), 5-Htt genotype, and an interactin of both on DNA methylation in the hippocampi of female C57BL/6 mice. Here, we applied Methylated DNA ImmunoPrecipitation (MeDIP) in a maternal restraint stress paradigm to perform a global promoter DNA methylation screen: Hippocampal DNA of wild type and 5-Htt +/- mice in stressed and control environments were analyzed to define genotype- (G) and environment-dependent (E) as well as GxE-interactive effects on promoter DNA methylation in the brain region, where marked effects were expected.
Project description:The serotonin transporter (5-HTT) gene-linked polymorphic region has been suggested to play a modulatory role in mediating the effects of early-life stress on psychopathology rendering carriers of the low-expression short (s)-allele more vulnerable to environmental adversity in later life. Here we analyzed the effects of prenatal stress (PS), 5-Htt genotype, and an interactin of both on DNA methylation in the hippocampi of female C57BL/6 mice. Here, we applied Methylated DNA ImmunoPrecipitation (MeDIP) in a maternal restraint stress paradigm to perform a global promoter DNA methylation screen: Hippocampal DNA of wild type and 5-Htt +/- mice in stressed and control environments were analyzed to define genotype- (G) and environment-dependent (E) as well as GxE-interactive effects on promoter DNA methylation in the brain region, where marked effects were expected. MeDIP-based promoter DNA methylation screen
Project description:prenatal stress response, genetic modification Background: Prenatal stress (PS) exposure has been shown to increase the risk for emotional disorders in later life. Furthermore, the serotonin transporter (5-HTT) genotype is suggested to exert a modulating effect on the association between early life stress and the risk for depression. In the present study, we use a 5-HTT x PS paradigm to investigate whether the effects of PS are dependent upon the 5-HTT genotype. Methods: The effects of PS on cognition, anxiety- and depression-related behaviour were examined using a maternal restraint stress paradigm of PS in C57BL6 wild-type (WT) and heterozygous (+/-) 5-HTT knockout mice. Additionally, in the female offspring, a genome-wide hippocampal gene expression screening was performed. Results: 5-HTT +/- offspring showed enhanced memory performance and signs of reduced anxiety as compared to WT offspring. Conversely, exposure of 5-HTT +/- mice to PS was associated with altered stress-responsivity and increased depressive-like behaviour, particularly in female offspring. Further, 5-HTT genotype, PS and their interaction differentially affected the expression of numerous genes and related pathways within the female hippocampus. Specifically, MAPK and neurotrophin signalling were regulated by both the 5-HTT +/- genotype and PS exposure, whereas cytokine and Wnt signalling were affected in a 5-HTT genotype x PS manner, indicating a gene x environment interaction at the molecular level. Conclusions: The long-term behavioural effects of PS in C57BL6 mice are partly dependent on the 5-HTT genotype. Further, hippocampal gene expression profiles suggest that distinct molecular mechanisms mediate the behavioural effects of the 5-HTT genotype, PS exposure, and their interaction.
Project description:prenatal stress response, genetic modification Background: Prenatal stress (PS) exposure has been shown to increase the risk for emotional disorders in later life. Furthermore, the serotonin transporter (5-HTT) genotype is suggested to exert a modulating effect on the association between early life stress and the risk for depression. In the present study, we use a 5-HTT x PS paradigm to investigate whether the effects of PS are dependent upon the 5-HTT genotype. Methods: The effects of PS on cognition, anxiety- and depression-related behaviour were examined using a maternal restraint stress paradigm of PS in C57BL6 wild-type (WT) and heterozygous (+/-) 5-HTT knockout mice. Additionally, in the female offspring, a genome-wide hippocampal gene expression screening was performed. Results: 5-HTT +/- offspring showed enhanced memory performance and signs of reduced anxiety as compared to WT offspring. Conversely, exposure of 5-HTT +/- mice to PS was associated with altered stress-responsivity and increased depressive-like behaviour, particularly in female offspring. Further, 5-HTT genotype, PS and their interaction differentially affected the expression of numerous genes and related pathways within the female hippocampus. Specifically, MAPK and neurotrophin signalling were regulated by both the 5-HTT +/- genotype and PS exposure, whereas cytokine and Wnt signalling were affected in a 5-HTT genotype x PS manner, indicating a gene x environment interaction at the molecular level. Conclusions: The long-term behavioural effects of PS in C57BL6 mice are partly dependent on the 5-HTT genotype. Further, hippocampal gene expression profiles suggest that distinct molecular mechanisms mediate the behavioural effects of the 5-HTT genotype, PS exposure, and their interaction. total samples analysed are 12
Project description:Progressive striatal gene expression changes and epigenetic alterations are a prominent feature of Huntington’s disease (HD), but direct relationships between the huntingtin (HTT) protein and chromatin remain poorly described. Here, using chromatin immunoprecipitation and sequencing (ChIP-seq), we show that HTT reproducibly occupies specific locations in the mouse genome, including thousands of genomic loci that are differentially occupied in striatal tissue from a knock-in mouse model of the HD mutation (B6.HttQ111/+) versus wildtype controls. ChIP-seq of histone modifications, generated in parallel, revealed genotype-specific colocalization of HTT with trimethylation of histone 3 lysine 27 (H3K27me3), a repressive chromatin mark. Near genes that are differentially regulated in HD, greater HTT occupancy in HttQ111/+ vs. wildtype mice predicted increased H3K27me3, reduced histone 3 lysine 4 (H3K4me3), a marker of poised and active promoters, and down-regulated gene expression. Altered huntingtin-chromatin interactions may therefore play a direct role in driving transcriptional dysregulation in HD.
Project description:Huntington’s Disease (HD) is an autosomal dominant neurodegenerative disorder caused by a trinucleotide repeat in exon 1 of the Huntingtin (HTT) gene. We used dCas9 epigenetic editing to downregulate HTT as a therapeutic approach for HD. A screen of multiple dCas9 variants fused to KRAB and DNMT3A/L with increasingly expanded PAM targeting was conducted to assess the ability to downregulate total HTT. Surprisingly, only spdCas9 could significantly downregulate HTT, while expanded PAM site variants dxCas9 and dCas9-VQR were less efficient in reducing HTT expression due to decreased binding efficiency of dCas9 variants. We further investigated DNA methylation changes through reduced representation bisulfite sequencing, showing high on-target increases in DNA methylation and few off-targets. In addition, we demonstrate mitotically stable HTT silencing of up to 6 weeks in vitro in a rapidly dividing cell line. Finally, we showed significant downregulation of HTT in patient-derived neuronal stem cells, showing the applicability in a disease-relevant system. This approach holds great promise for those suffering from disorders caused by gain of function mutations like HD.
Project description:We generated two types of DNA methylation datasets (Reduced Representation Bisulfite Sequencing [RRBS] and custom methylation array) from a heterozygous HD knock-in mouse model. The heterozygous Htt knock-in line expressed one wildtype endogenous Htt allele and a second Htt allele with knock-in of human mHTT exon 1 with either approximately 190 CAG repeats (Q175) or 20 CAG repeats (Q20). For each genotype (Q175 and Q20) we analyzed two brain regions (striatum and cerebellum) from 8 mice each on the RRBS platform (N=32 RRBS samples). Our EWAS of mutant Htt gene status (i.e. Q175 status) across the two brain regions identified two genome-wide significant CpGs in Htt region. contributor: CHDI foundation
Project description:In Huntington’s disease (HD), expanded HTT CAG repeat length correlates strongly with age at motor onset, indicating that it determines the rate of the disease process leading to diagnostic clinical manifestations. Similarly, in normal individuals, HTT CAG repeat length is correlated with biochemical differences that reveal it as a functional polymorphism. Here, we tested the hypothesis that gene expression signatures can capture continuous, length-dependent effects of the HTT CAG repeat. Using gene expression datasets for 107 HD and control lymphoblastoid cell lines, we constructed mathematical models in an iterative manner, based upon CAG correlated gene expression patterns in randomly chosen training samples, and tested their predictive power in test samples. Predicted CAG repeat lengths were significantly correlated with experimentally determined CAG repeat lengths, whereas models based upon randomly permuted CAGs were not at all predictive. Predictions from different batches of mRNA for the same cell lines were significantly correlated, implying that CAG length-correlated gene expression is reproducible. Notably, HTT expression was not itself correlated with HTT CAG repeat length. Taken together, these findings confirm the concept of a gene expression signature representing the continuous effect of HTT CAG length and not primarily dependent on the level of huntingtin expression. Such global and unbiased approaches, applied to additional cell types and tissues, may facilitate the discovery of therapies for HD by providing a comprehensive view of molecular changes triggered by HTT CAG repeat length for use in screening for and testing compounds that reverse effects of the HTT CAG expansion. To evaluate the continuous analytical approach as a strategy to discover the molecular consequences of the HTT CAG repeat, genome-wide gene expression datasets were generated from a panel of 107 human lymphoblastoid cell lines with HTT CAGs spanning the entire spectrum of allele sizes.
Project description:The earliest stages of Huntington’s disease are marked by changes in gene expression that are caused in an indirect and poorly understood manner by polyglutamine expansions in the huntingtin protein (HTT). To explore the hypothesis DNA methylation may be altered in cells expressing mutated HTT, we use reduced-representation bisulfite sequencing (RRBS) to map sites of DNA methylation in cells carrying either wild-type or mutant HTT. We find that a large fraction of the genes that change in expression in the presence of mutant huntingtin demonstrate significant changes in DNA methylation. Regions with low CpG content, which have previously been shown to undergo methylation changes in response to neuronal activity, are disproportionately affected. Based on the sequence of regions that change in methylation, we identify AP-1 and SOX2 as transcriptional regulators associated with DNA methylation changes, and we confirm these hypotheses using genome-wide chromatin immunoprecipitation (ChIP-Seq). Our findings suggest new mechanisms for the effects of polyglutamine-expanded HTT. These results also raise important questions about the potential effects of changes in DNA methylation on neurogenesis and at later stages, cognitive decline in Huntington’s patients. mRNA-seq in STHdhQ7/Q7 and STHdhQ111/Q111 cells