21 research outputs found

    Nucleosome Repositioning: A Novel Mechanism for Nicotine- and Cocaine-Induced Epigenetic Changes

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    <div><p>Drugs of abuse modify behavior by altering gene expression in the brain. Gene expression can be regulated by changes in DNA methylation as well as by histone modifications, which alter chromatin structure, DNA compaction and DNA accessibility. In order to better understand the molecular mechanisms directing drug-induced changes in chromatin structure, we examined DNA-nucleosome interactions within promoter regions of 858 genes in human neuroblastoma cells (SH-SY5Y) exposed to nicotine or cocaine. Widespread, drug- and time-resolved repositioning of nucleosomes was identified at the transcription start site and promoter region of multiple genes. Nicotine and cocaine produced unique and shared changes in terms of the numbers and types of genes affected, as well as repositioning of nucleosomes at sites which could increase or decrease the probability of gene expression based on DNA accessibility. Half of the drug-induced nucleosome positions approximated a theoretical model of nucleosome occupancy based on physical and chemical characteristics of the DNA sequence, whereas the basal or drug naïve positions were generally DNA sequence independent. Thus we suggest that nucleosome repositioning represents an initial dynamic genome-wide alteration of the transcriptional landscape preceding more selective downstream transcriptional reprogramming, which ultimately characterizes the cell- and tissue-specific responses to drugs of abuse.</p></div

    A comparison of the magnitude of reductions in D1R and D2R protein expression.

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    <p>A comparison of the magnitude of reductions in D1R and D2R protein expression in the frontal cortex (FC) and caudate putamen (CP) of postnatal day 60 (P60) and postnatal day 14 (P14) Dyt1 KO (KO) and Dyt1 KI (KI) mice.</p><p>A comparison of the magnitude of reductions in D1R and D2R protein expression.</p

    Gα(s) and Gα(olf) expression at P60.

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    <p>Gα(s) and Gα(olf) expression in the frontal cortex, caudate-putamen and ventral midbrain of Dyt1 KO and Gnal KO mice at postnatal day 60 (P60; A-D). In each panel, the upper band shows Gα(s) (Fig 4A and 4B), and Gα(olf) (Fig 4C and 4D), and the lower band shows β-actin, which was used as a loading control. The bar graphs in each panel represent Gα(s), and Gα(olf) band intensity (mean ± SEM) normalized to intensity of loading control (integrated density value; IDV). The names of the mouse lines (<i>Dyt1</i> KO, and <i>Gnal</i> KO) are indicated to the right.</p

    Cocaine- and nicotine-induced nucleosome repositioning comparisons.

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    <p>(A) Changes in nucleosome repositioning that were unique to nicotine or cocaine, and common to both the drugs. (B-E) Nucleosome repositioning in response to nicotine or cocaine exposure is shown. (B) Nucleosome repositioning upstream of TSS, at the TSS and at the beginning of the coding sequence in the <i>CDNK1C</i> gene around the TSS was induced by nicotine and not by cocaine (nicotine-specific). Nicotine exposure positioned nucleosomes upstream of the TSS, depleted the nucleosomes at the TSS, and positioned nucleosomes at the start of the coding sequence. On the other hand, cocaine exposure for 20 min, did not produce changes in nucleosome position compared to the drug naïve state. (C) Nicotine and cocaine both induced nucleosome repositioning upstream of TSS, at the TSS and at the beginning of the coding sequence in the <i>ANGPT2</i> gene. However, 60 min cocaine-specific changes were detected at the +1 nucleosome (asterisk), just downstream of the <i>ANGPT2</i> TSS. The 60 min nicotine-induced nucleosome repositioning at <i>ANGPT2</i> is similar to the 20 min time point and therefore is not shown. (D) Changes common to nicotine (10 min) and cocaine (20 min) just upstream and downstream of the TSS of <i>FNB2</i> gene. (E) Neither nicotine (10 min) nor cocaine (20 min) produced nucleosome repositioning across the promoter and 5’ region of <i>BMP3</i>. Nucleosome positions relative to the TSS and coding sequence of each gene in the drug naïve (black) and drug exposed (red) states are further illustrated pictorially at the bottom of the figure. Each sphere (black or red) represents a nucleosome.</p

    D1R expression at P60.

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    <p>D1R expression in the frontal cortex, caudate-putamen and ventral midbrain of postnatal day 60 (P60; A-I) mice. In each panel, the upper band shows D1R and the lower band shows β-actin, which was used as a loading control. The bar graphs in each panel represent D1R band intensity (mean ± SEM) normalized to intensity of the loading control (integrated density value; IDV). The names of the mouse lines (<i>Dyt1</i> KO, <i>Dyt1</i> KI, hMT) are indicated to the right. (*<i>p</i><0.05, **<i>p</i><0.01; n = 3 or 4).</p

    Role of DNA sequence in nicotine- and cocaine-induced nucleosome repositioning.

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    <p>(A) DNA-directed nucleosome repositioning events following nicotine or cocaine treatment are shown for the <i>HDAC1</i> and <i>BAI1</i> genes. For both examples, nucleosomes were repositioned upstream and downstream of the TSS, according to the DNA-directed model. (B) DNA-independent nucleosome repositioning events following nicotine or cocaine treatment are shown for the <i>CXCL6</i> and <i>APC</i> genes, with significant remodeling events in the upstream regions and TSS of both genes. Nucleosome positions predicted by the DNA-directed model are shown as a blue line. Nucleosome illustrations (black—basal; red—nicotine treated) depict the changes in individual nucleosome positions, relative to the TSS and coding sequence of the gene model above.</p

    Summary of the literature on the effects of developmental nicotine exposure on locomotor activity in mice.

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    <p>Summary of the literature on the effects of developmental nicotine exposure on locomotor activity in mice.</p

    Perinatal nicotine exposure and anxiety-like phenotype in elevated plus maze (EPM).

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    <p>The percentage of time spent in the open versus closed arms (A) and the number of entries into open arms (B) of the EPM were analyzed. Neither measure showed significant difference in male or female mice from the nicotine+saccharin (N + S), saccharin alone (S) and plain drinking water (W) groups. [Mean ± SEM % time spent in open arms: Male: W = 26.44 ± 4.34; S = 23.89 ± 2.88; N + S = 23.56 ± 2.56; Female: W = 17.65 ± 3.88; S = 19.05 ± 23.84; N + S = 21.53 ± 3.64. Mean ± SEM number of entries into open arms: Male: W = 9.67 ± 1.21; S = 9.33 ± 1.17; N + S = 9.5 ± 1.16; Female: W = 8.40 ± 1.32; S = 8.20 ± 1.33; N + S = 8.00 ± 1.20].</p

    Perinatal nicotine exposure produces a significant decrease in spontaneous alternation in the Y-maze in male but not female offspring.

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    <p>Spontaneous alternation in the Y-maze was analyzed in male and female mice from the nicotine+saccharin (N + S), saccharin alone (S) and plain drinking water (W) groups. There was a significant decreases in this measurement in male mice from the N+S group. ***<i>p</i><0.001. [Mean ± SEM: Male: W: 71.31 ± 1.20; S: 71.11 ± 4.33; N + S: 52.37 ± 4.63; Female: W: 65.57 ± 4.43; S: 66.63 ± 4.42; N + S: 67.19 ± 3.56].</p

    A summary of the changes in D1R, D2R and Gα(olf) expression at P14.

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    <p>A summary of the changes in D1R, D2R and Gα(olf) expression at postnatal day 14 (P14) in the frontal cortex (FC) and caudate-putamen (CP) in the Dyt1 KO (KO) and Dyt1 KI (KI) lines of mouse.</p><p><b>↓</b> indicates statistically significant reductions in expression compared to wild-type control mice.</p><p>—indicates no statistically significant difference.</p><p>A summary of the changes in D1R, D2R and Gα(olf) expression at P14.</p
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