Project description:Transcriptional dysregulation has emerged as a core pathologic feature of Huntington's disease (HD), one of several triplet-repeat disorders characterized by movement deficits and cognitive dysfunction. Although the mechanisms contributing to the gene expression deficits remain unknown, therapeutic strategies have aimed to improve transcriptional output via modulation of chromatin structure. Recent studies have demonstrated therapeutic effects of commercially available histone deacetylase (HDAC) inhibitors in several HD models; however, the therapeutic value of these compounds is limited by their toxic effects. Here, beneficial effects of a novel pimelic diphenylamide HDAC inhibitor, HDACi 4b, in an HD mouse model are reported. Chronic oral administration of HDACi 4b, beginning after the onset of motor deficits, significantly improved motor performance, overall appearance, and body weight of symptomatic R6/2(300Q) transgenic mice. These effects were associated with significant attenuation of gross brain-size decline and striatal atrophy. Microarray studies revealed that HDACi 4b treatment ameliorated, in part, alterations in gene expression caused by the presence of mutant huntingtin protein in the striatum, cortex, and cerebellum of R6/2(300Q) transgenic mice. For selected genes, HDACi 4b treatment reversed histone H3 hypoacetylation observed in the presence of mutant huntingtin, in association with correction of mRNA expression levels. These findings suggest that HDACi 4b, and possibly related HDAC inhibitors, may offer clinical benefit for HD patients and provide a novel set of potential biomarkers for clinical assessment. Analysis of striatum, cortex, and cerebellum from R6/2(300Q) transgenic mice before and after treatment with the HDAC inhibitor 4b
Project description:Transcriptional dysregulation has emerged as a core pathologic feature of Huntington's disease (HD), one of several triplet-repeat disorders characterized by movement deficits and cognitive dysfunction. Although the mechanisms contributing to the gene expression deficits remain unknown, therapeutic strategies have aimed to improve transcriptional output via modulation of chromatin structure. Recent studies have demonstrated therapeutic effects of commercially available histone deacetylase (HDAC) inhibitors in several HD models; however, the therapeutic value of these compounds is limited by their toxic effects. Here, beneficial effects of a novel pimelic diphenylamide HDAC inhibitor, HDACi 4b, in an HD mouse model are reported. Chronic oral administration of HDACi 4b, beginning after the onset of motor deficits, significantly improved motor performance, overall appearance, and body weight of symptomatic R6/2(300Q) transgenic mice. These effects were associated with significant attenuation of gross brain-size decline and striatal atrophy. Microarray studies revealed that HDACi 4b treatment ameliorated, in part, alterations in gene expression caused by the presence of mutant huntingtin protein in the striatum, cortex, and cerebellum of R6/2(300Q) transgenic mice. For selected genes, HDACi 4b treatment reversed histone H3 hypoacetylation observed in the presence of mutant huntingtin, in association with correction of mRNA expression levels. These findings suggest that HDACi 4b, and possibly related HDAC inhibitors, may offer clinical benefit for HD patients and provide a novel set of potential biomarkers for clinical assessment.
Project description:Increasing evidence has demonstrated that epigenetic factors can profoundly influence gene expression and, in turn, influence resistance or susceptibility to disease. Epigenetic drugs, such as histone deacetylase (HDAC) inhibitors, are finding their way into clinical practice, although their exact mechanisms of action are unclear. To identify mechanisms associated with HDAC inhibition, we performed microarray analysis on brain and muscle samples treated with the HDAC1/3-targeting inhibitor, HDACi 4b. Pathways analyses of microarray datasets implicate DNA methylation as significantly associated with HDAC inhibition. Further assessment of DNA methylation changes elicited by HDACi 4b in human fibroblasts from normal controls and patients with Huntington's disease (HD) using the Infinium HumanMethylation450 BeadChip revealed a limited, but overlapping, subset of methylated CpG sites that were altered by HDAC inhibition in both normal and HD cells. Among the altered loci of Y chromosome-linked genes, KDM5D, which encodes Lys (K)-specific demethylase 5D, showed increased methylation at several CpG sites in both normal and HD cells, as well as in DNA isolated from sperm from drug-treated male mice. Further, we demonstrate that first filial generation (F1) offspring from drug-treated male HD transgenic mice show significantly improved HD disease phenotypes compared with F1 offspring from vehicle-treated male HD transgenic mice, in association with increased Kdm5d expression, and decreased histone H3 Lys4 (K4) (H3K4) methylation in the CNS of male offspring. Additionally, we show that overexpression of Kdm5d in mutant HD striatal cells significantly improves metabolic deficits. These findings indicate that HDAC inhibitors can elicit transgenerational effects, via cross-talk between different epigenetic mechanisms, to have an impact on disease phenotypes in a beneficial manner. Bisulphite converted DNA from the 12 samples were hybridised to the Illumina Infinium 27k Human Methylation Beadchip v1.2. We demonstrate that histone deacetylase (HDAC) inhibition can elicit changes in DNA methylation in Huntington’s disease (HD) human fibroblasts, as well as in sperm from HD transgenic mice, in association with DNA methylation-related gene expression changes. We suggest that alterations in sperm DNA methylation lead to transgenerational effects, and, accordingly, we show that first filial generation (F1) offspring of HDAC inhibitor-treated male HD transgenic mice show improved HD disease phenotypes compared with F1 offspring from vehicle-treated male HD transgenic mice. These findings have significant implications for human health because they enforce the concept that ancestral drug exposure may be a major molecular factor that can affect disease phenotypes, yet in a positive manner. Further, we implicate Lys (K)-specific demethylase 5d expression in this phenomenon.
Project description:Increasing evidence has demonstrated that epigenetic factors can profoundly influence gene expression and, in turn, influence resistance or susceptibility to disease. Epigenetic drugs, such as histone deacetylase (HDAC) inhibitors, are finding their way into clinical practice, although their exact mechanisms of action are unclear. To identify mechanisms associated with HDAC inhibition, we performed microarray analysis on brain and muscle samples treated with the HDAC1/3-targeting inhibitor, HDACi 4b. Pathways analyses of microarray datasets implicate DNA methylation as significantly associated with HDAC inhibition. Further assessment of DNA methylation changes elicited by HDACi 4b in human fibroblasts from normal controls and patients with Huntington's disease (HD) using the Infinium HumanMethylation450 BeadChip revealed a limited, but overlapping, subset of methylated CpG sites that were altered by HDAC inhibition in both normal and HD cells. Among the altered loci of Y chromosome-linked genes, KDM5D, which encodes Lys (K)-specific demethylase 5D, showed increased methylation at several CpG sites in both normal and HD cells, as well as in DNA isolated from sperm from drug-treated male mice. Further, we demonstrate that first filial generation (F1) offspring from drug-treated male HD transgenic mice show significantly improved HD disease phenotypes compared with F1 offspring from vehicle-treated male HD transgenic mice, in association with increased Kdm5d expression, and decreased histone H3 Lys4 (K4) (H3K4) methylation in the CNS of male offspring. Additionally, we show that overexpression of Kdm5d in mutant HD striatal cells significantly improves metabolic deficits. These findings indicate that HDAC inhibitors can elicit transgenerational effects, via cross-talk between different epigenetic mechanisms, to have an impact on disease phenotypes in a beneficial manner.
Project description:To assess the effects of histone deacetylase (HDAC) inhibitor, HDACi 4b, treatment on muscle function on a molecular level, we performed microarray analysis on skeletal muscle (gastrocnemius) samples from wt and N17182Q mice treated with the HDAC inhibitor 4b for 3 months (50 mg/kg; s.c. injection 3x weekly; n=4 per group). The transcriptome pattern in N17182Q mice compared to wt controls consisted of deficits in the expression of genes related to mitochondrial function and oxidative metabolism. In addition, we noted that numerous genes associated with basal contractile function were altered in HD N17182Q mice. These include genes related to the muscle contractile complex, Tnnt3 and Myh8, as well as several additional myosin genes: myosin heavy chain genes, Myh10 and Myh4, and myosin light chain genes, Myl1, Mylc2 and Mylk. These findings implicate deficits in the underlying contractile function in skeletal muscle from HD mice. Further, we found robust effects of 4b treatment on the expression of genes in skeletal muscle, with 556 genes showing significantly altered expression, at p<0.005, in 4b-treated N17182Q muscle compared to vehicle-treated control mice. n=4 vehicle-treated WT mice, n=5 HDACi 4b-treated WT mice, n=4 vehicle-treated N17182Q transgenic mice, and n=3 HDACi 4b-treated N17182Q transgenic mice.
Project description:Transcriptional dysregulation plays a major role in the pathology of Huntington's disease (HD). However, the mechanisms causing selective downregulation of genes remain unknown. Histones regulate chromatin structure and thereby control gene expression; recent studies have demonstrated a therapeutic role for histone deacetylase (HDAC) inhibitors in polyglutamine diseases. This study demonstrates that despite no change in overall acetylated histone levels, histone H3 is hypo-acetylated at promoters of downregulated genes in R6/2 mice, ST14a and STHdh cells, as demonstrated by in vivo chromatin immunoprecipitation. In addition, HDAC inhibitor treatment increases association of acetylated histones with downregulated genes and corrects mRNA abnormalities. In contrast, there is a decrease in mRNA levels in wild-type cells following treatment with a histone acetyltransferase inhibitor. Although changes in histone acetylation correlate with decreased gene expression, histone hypo-acetylation may be a late event, as no hypo-acetylation is observed in 4-week-old R6/2 mice. Nevertheless, treatment with HDAC inhibitors corrects mRNA abnormalities through modification of histone proteins and may prove to be of therapeutic value in HD. Keywords: cell type comparison and disease state analysis
Project description:To assess the effects of histone deacetylase (HDAC) inhibitor, HDACi 4b, treatment on muscle function on a molecular level, we performed microarray analysis on skeletal muscle (gastrocnemius) samples from wt and N17182Q mice treated with the HDAC inhibitor 4b for 3 months (50 mg/kg; s.c. injection 3x weekly; n=4 per group). The transcriptome pattern in N17182Q mice compared to wt controls consisted of deficits in the expression of genes related to mitochondrial function and oxidative metabolism. In addition, we noted that numerous genes associated with basal contractile function were altered in HD N17182Q mice. These include genes related to the muscle contractile complex, Tnnt3 and Myh8, as well as several additional myosin genes: myosin heavy chain genes, Myh10 and Myh4, and myosin light chain genes, Myl1, Mylc2 and Mylk. These findings implicate deficits in the underlying contractile function in skeletal muscle from HD mice. Further, we found robust effects of 4b treatment on the expression of genes in skeletal muscle, with 556 genes showing significantly altered expression, at p<0.005, in 4b-treated N17182Q muscle compared to vehicle-treated control mice.
Project description:Dysregulation of the kynurenine (Kyn) pathway has been associated with the progression of Huntington's disease (HD). In particular, elevated levels of the kynurenine metabolites 3-hydroxy kynurenine (3-OH-Kyn) and quinolinic acid (Quin), have been reported in the brains of HD patients as well as in rodent models of HD. The production of these metabolites is controlled by the activity of kynurenine mono-oxygenase (KMO), a mitochondrial outer membrane enzyme which catalyzes the synthesis of 3-OH-Kyn from Kyn. Thus inhibiting KMO is expected to produce a beneficial effect in Huntington's Disease (HD) patients, hopefully reversing their phenotype to match healthy subjects. To test this effect, we acutely treated a mouse model of HD (R6/2, a transgenic mouse model of HD which contains a human HTT gene containing 90 CAG repeats) and wild type mice with a KMO inhibitor, and separately used a mock treatment on both the transgenic mice and wild type mice. The goal of this project is to analyze the RNA-seq data and find gene expression changes associated with the KMO inhibitor
Project description:Dysregulation of the kynurenine (Kyn) pathway has been associated with the progression of Huntington's disease (HD). In particular, elevated levels of the kynurenine metabolites 3-hydroxy kynurenine (3-OH-Kyn) and quinolinic acid (Quin), have been reported in the brains of HD patients as well as in rodent models of HD. The production of these metabolites is controlled by the activity of kynurenine mono-oxygenase (KMO), a mitochondrial outer membrane enzyme which catalyzes the synthesis of 3-OH-Kyn from Kyn. Thus inhibiting KMO is expected to produce a beneficial effect in Huntington's Disease (HD) patients, hopefully reversing their phenotype to match healthy subjects. To test this effect, we chronically treated a mouse model of HD (R6/2, a transgenic mouse model of HD which contains a human HTT gene containing 90 CAG repeats) and wild type mice with a KMO inhibitor for 8 weeks, and separately used a mock treatment on both the transgenic mice and wild type mice. The goal of this project is to analyze the RNA-seq data and find gene expression changes associated with the KMO inhibitor.