The heat shock response (HSR) is a mechanism to cope with proteotoxic stress by inducing the expression of molecular chaperones and other heat shock response genes. The HSR is evolutionarily well conserved and has been widely studied in bacteria, cell lines and lower eukaryotic model organisms. However, mechanistic insights into the HSR in higher eukaryotes, in particular in mammals, are limited. We have developed an in vivo heat shock protocol to analyze the HSR in mice and dissected heat shock factor 1 (HSF1)-dependent and -independent pathways. Whilst the induction of proteostasis-related genes was dependent on HSF1, the regulation of circadian function related genes, indicating that the circadian clock oscillators have been reset, was independent of its presence. Furthermore, we demonstrate that the in vivo HSR is impaired in mouse models of Huntington's disease but we were unable to corroborate the general repression of transcription after a heat shock found in lower eukaryotes. Overall design: RNA-Seq was performed on mRNA isolated from quadriceps femoris muscle of 24 mice. These mice were of wild type, R6/2, and Hsf1-/- genotypes. Two mice of each genotype were tested in four conditions: (1) heat shock, (2) control heat shock, (3) HSP90 inhibition (NVP-HSP990), and (4) HSP90 inhibition vehicle.
HSF1-dependent and -independent regulation of the mammalian in vivo heat shock response and its impairment in Huntington's disease mouse models.
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Cerebellar development requires regulated proliferation of cerebellar granule neuron progenitors (CGNPs). Inadequate CGNP proliferation causes cerebellar hypoplasia while excessive CGNP proliferation can cause medulloblastoma, the most common malignant pediatric brain tumor. Although Sonic Hedgehog (SHH) signaling is known to activate CGNP proliferation, the mechanisms down-regulating proliferation are less defined. We investigated CGNP regulation by GSK-3, which down-regulates proliferation in the forebrain, gut and breast by suppressing mitogenic WNT signaling. In striking contrast, we found that co-deleting Gsk-3α and Gsk-3β blocked CGNP proliferation, causing severe cerebellar hypoplasia. Transcriptomic analysis showed activated WNT signaling and up-regulated Cdkn1a in Gsk-3-deleted CGNPs. These data show that a GSK-3/WNT axis modulates the developmental proliferation of CGNPs and the pathologic growth of SHH-driven medulloblastoma. The requirement for GSK-3 in SHH-driven proliferation suggests that GSK-3 may be targeted for SHH-driven medulloblastoma therapy.
GSK-3 modulates SHH-driven proliferation in postnatal cerebellar neurogenesis and medulloblastoma.
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Investigation of gene expression profiles among patients with COPD frequent exacerbations and to find gene targets as predictors of exacerbations
Altered gene expression in blood and sputum in COPD frequent exacerbators in the ECLIPSE cohort.
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Progression to malignancy requires cells to overcome senescence and switch to an immortal phenotype. Thus, exploring the genetic and epigenetic changes that occur during senescence/immortalization may help elucidate crucial events that lead to cell transformation. In the present study, we have globally profiled DNA methylation in relation to gene expression in primary, senescent and immortalized mouse embryonic fibroblasts.
Mammalian cells acquire epigenetic hallmarks of human cancer during immortalization.
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Microarrays were used to evaluate the effect of sucrose on gene expression in guard cells. Strips of Arabidopsis leaves were incubated with sucrose or mannitol or no sugars, then the leaves were freeze dried and guard cells were dissected from the leaf strips and analyzed.
A comparative study of the Arabidopsis thaliana guard-cell transcriptome and its modulation by sucrose.
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Induced sputum is used to sample inflammatory cells, predominantly neutrophils and macrophages, from the airways of COPD patients. Our aim was to identify candidate genes associated with the degree of airflow obstruction and the extent of emphysema by expression profiling, and then to confirm these findings for selected candidates using specific PCR and protein analysis.
Induced sputum genes associated with spirometric and radiological disease severity in COPD ex-smokers.
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Changes in the transcriptomic profile of the Sciencell human astrocytes, after hypoxia treatment were compared to control cells receiving no treatment, to identify differentially expressed genes and pathways.
Transcriptomic Analysis of Human Astrocytes In Vitro Reveals Hypoxia-Induced Mitochondrial Dysfunction, Modulation of Metabolism, and Dysregulation of the Immune Response.
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Reversible protein acetylation provides a central mechanism for controlling gene expression and cellular signaling events. It is governed by the antagonistic commitment of two enzymes families: the histone acetyltransferases (HATs) and the histone deacetylases (HDACs). HDAC4, like its class IIa counterparts, is a potent transcriptional repressor through interactions with tissue-specific transcription factors via its N-terminal domain. Whilst the lysine deacetylase activity of the class IIa HDACs is much less potent than that of the class I enzymes, HDAC4 has been reported to influence protein deacetylation through its interaction with HDAC3.
HDAC4 does not act as a protein deacetylase in the postnatal murine brain in vivo.
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To dissect the impact of nuclear and extranuclear mutant htt on the initiation and progression of disease, we generated a series of transgenic mouse lines in which nuclear localization (NLS) or nuclear export sequences (NES) have been placed N-terminal to the htt exon 1 protein carrying 144 glutamines. Our data indicate that the exon 1 mutant protein is present in the nucleus as part of an oligomeric or aggregation complex. Increasing the concentration of the mutant transprotein in the nucleus is sufficient for, and dramatically accelerates the onset and progression of behavioral phenotypes. Furthermore, nuclear exon 1 mutant protein is sufficient to induce cytoplasmic neurodegeneration and transcriptional dysregulation. However, our data suggests that cytoplasmic mutant exon 1 htt, if present, contributes to disease progression.
Contribution of nuclear and extranuclear polyQ to neurological phenotypes in mouse models of Huntington's disease.
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Huntingtons disease (HD) is a neurodegenerative disorder that is associated with the deposition of proteinaceous aggregates in the brains of HD patients and mouse models. Previous studies have suggested that wide-scale disruption of protein homeostasis occurs in protein folding diseases. Protein homeostasis can be maintained by activation of the heat shock response (HSR) via the transcription factor heat shock factor 1 (HSF1), the pharmacological activation of which can be achieved by Hsp90 inhibition and has been demonstrated to be beneficial in cell and invertebrate models of HD. Whether the HSR is functional in HD and whether its activation has therapeutic potential in mammalian HD models is currently unknown. To address these issues, we used a novel, brain penetrant Hsp90 inhibitor to activate the HSR in brain after systemic administration. Microarrays, quantitative PCR and western blotting showed that the HSR becomes impaired with disease progression in two mouse models of HD and that this originates at the level of transcription.
Altered chromatin architecture underlies progressive impairment of the heat shock response in mouse models of Huntington disease.
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