Project description:We recently found that the endoplasmic reticulum (ER) stress response (ERSR) is activated in surviving cardiac myocytes in a mouse model of in vivo myocardial infarction. ATF6 is an ER stress-activated transcription factor that induces ERSR genes, some of which encode proteins that may protect against ischemic damage. However, few ERSR genes have been identified in the heart, and there have been no gene expression profiling studies of ATF6-inducible genes, in vivo. We previously generated transgenic (TG) mice that express tamoxifen-activated ATF6, ATF6-MER, in the heart; ATF6-MER conferred tamoxifen-dependent ATF6 activation and protection from ischemic damage. To understand of the mechanism of ATF6-mediated cardioprotection, gene expression profiling of ATF6-MER TG mouse hearts was performed. Activated ATF6 changed expression levels of 1,162 genes in the heart; of the 775 ATF6-inducible genes, only 23 are known ERSR genes. One of the genes not expected to be induced by ATF6 is modulatory calcinuerin-interacting protein-1 (MCIP1). MCIP1 is induced in a calcineurin/NFAT-dependent manner during myocardial hypertrophy and it can feedback inhibit cardiomyocyte growth. We found that MCIP1 expression in cultured cardiomyocytes was increased by the prototypical ER stresser, tunicamycin (TM), or by simulated ischemia. Moreover, infecting cardiomyocytes with adenovirus encoding activated ATF6 induced MCIP1 expression and inhibited myocyte growth in response to the ï¡-adrenergic agonist, phenylephrine. These results suggest that MCIP1 can be induced in the heart by ER stresses, such as ischemia. Moreover, b integrating hypertrophy and ER stress, MCIP-modulated myocyte growth may help rejuvenate nascent ER protein folding, which could contribute to protection from ischemic damage. Experiment Overall Design: 12 mice were analyzed in this study. Four treatment groups were included in this study: transgenic ATF6-MER mice treated with tamoxifen, transgenic ATF6-MER mice treated with vehicle, nontransgenic littermates treated with tamoxifen, and nontransgenic littermates treated with vehicle. Each treatment group included 3 separate biological replicate samples. Each mouse sampled was male, C57/BL6, ~30 weeks old. Each mouse was treated, then the mouse was sacrificed, the heart was extracted, and left ventricle was isolated. Total RNA was isolated from the left ventricle, and used for hybridization onto an Affymetrix mus 430 2.0 full-genome chip. Each heart was hybridized onto its own chip.
Project description:We wished to determine the effects of activating the transcription factor, ATF6, on global miRNA expression. We utilized transgenic mice with a conditionally tamoxien-responsive form of ATF6 and assessed cardiac lysates from NTG and TG mice, both treated with tamoxifen and untreated, in order to identify differentially expressed miRNAs. We then focused on miRNAs of interest as well as the genes they are predicted to regulate. Four sample groups were assessed for miRNA expression: non-transgenic (NTG) mice treated with vehicle, NTG mice treated with tamoxifen, ATF6 transgenic (TG) mice treated with vehicle, and TG mice treated with tamoxifen
Project description:We wished to determine the effects of activating the transcription factor, ATF6, on global miRNA expression. We utilized transgenic mice with a conditionally tamoxien-responsive form of ATF6 and assessed cardiac lysates from NTG and TG mice, both treated with tamoxifen and untreated, in order to identify differentially expressed miRNAs. We then focused on miRNAs of interest as well as the genes they are predicted to regulate.
Project description:We recently found that the endoplasmic reticulum (ER) stress response (ERSR) is activated in surviving cardiac myocytes in a mouse model of in vivo myocardial infarction. ATF6 is an ER stress-activated transcription factor that induces ERSR genes, some of which encode proteins that may protect against ischemic damage. However, few ERSR genes have been identified in the heart, and there have been no gene expression profiling studies of ATF6-inducible genes, in vivo. We previously generated transgenic (TG) mice that express tamoxifen-activated ATF6, ATF6-MER, in the heart; ATF6-MER conferred tamoxifen-dependent ATF6 activation and protection from ischemic damage. To understand of the mechanism of ATF6-mediated cardioprotection, gene expression profiling of ATF6-MER TG mouse hearts was performed. Activated ATF6 changed expression levels of 1,162 genes in the heart; of the 775 ATF6-inducible genes, only 23 are known ERSR genes. One of the genes not expected to be induced by ATF6 is modulatory calcinuerin-interacting protein-1 (MCIP1). MCIP1 is induced in a calcineurin/NFAT-dependent manner during myocardial hypertrophy and it can feedback inhibit cardiomyocyte growth. We found that MCIP1 expression in cultured cardiomyocytes was increased by the prototypical ER stresser, tunicamycin (TM), or by simulated ischemia. Moreover, infecting cardiomyocytes with adenovirus encoding activated ATF6 induced MCIP1 expression and inhibited myocyte growth in response to the alpha 1-adrenergic agonist, phenylephrine. These results suggest that MCIP1 can be induced in the heart by ER stresses, such as ischemia. Moreover, b integrating hypertrophy and ER stress, MCIP-modulated myocyte growth may help rejuvenate nascent ER protein folding, which could contribute to protection from ischemic damage. Keywords: Gene expression analysis of the effect of activating ATF6 in the hearts of transgenic mice upon treatment with tamoxifen.
Project description:Eukaryotic cells maintain protein homeostasis through the activity of multiple basal and inducible systems, which function in concert to allow cells to adapt to a wide range of environmental conditions. Although the transcriptional programs regulating individual pathways have been studied in detail, it is not known how the different pathways are transcriptionally integrated such that a deficiency in one pathway can be compensated by a change in an auxiliary response. One such pathway that plays an essential role in many proteostasis responses is the ubiquitin-proteasome system, which functions to degrade damaged, unfolded, or short half-life proteins. Transcriptional regulation of the proteasome is mediated by the transcription factor Nrf1. Using a conditional knockout mouse model, we found that Nrf1 regulates protein homeostasis in the endoplasmic reticulum (ER) through transcriptional regulation of the ER stress sensor ATF6. In Nrf1 conditional-knockout mice, a reduction in proteasome activity is accompanied by an ATF6-dependent downregulation of the endoplasmic reticulum-associated degradation machinery, which reduces the substrate burden on the proteasome. This indicates that Nrf1 regulates a homeostatic shift through which proteostasis in the endoplasmic reticulum and cytoplasm are coregulated based on a cell's ability to degrade proteins.
Project description:A major task in dissecting the genetics of complex traits is to identify causal genes for disease phenotypes. We previously developed a method to infer causal relationships among genes through the integration of DNA variation, gene transcription, and phenotypic information. Here we validated our method through the characterization of transgenic and knockout mouse models of candidate genes that were predicted to be causal for abdominal obesity. Perturbation of eight out of the nine genes, with Gas7, Me1 and Gpx3 being novel, resulted in significant changes in obesity related traits. Liver expression signatures revealed alterations in common metabolic pathways and networks contributing to abdominal obesity and overlapped with a macrophage-enriched metabolic network module that is highly associated with metabolic traits in mice and humans. Integration of gene expression in the design and analysis of traditional F2 intercross studies allows high confidence prediction of causal genes, and identification of involved pathways and networks. This SuperSeries is composed of the following subset Series: GSE11991: Liver gene expression profiling of lipoprotein lipase heterozygous knockout mice GSE11992: Liver gene expression profiling of cytosolic malic enzyme knockout mice GSE11993: Liver gene expression profiling of zinc finger binding protein 90 (Zfp90) transgenic mice GSE11994: Liver gene expression profiling of transforming growth factor beta receptor 2 heterozygous knockout (Tgfbr2+/-) mice GSE11995: Liver gene expression profiling of complement component 3a receptor 1 knockout (C3ar1-/-) mice GSE11996: Gas7 male transgenic liver expression vs FVB male wildtype control GSE11997: Gpx3 male transgenic liver expression vs B6/DBA male wildtype control GSE11998: Gyk female heterozygous liver expression vs C57Bl/6J female wildtype control GSE11999: Lactb male transgenic liver expression vs FVB male wildtype control Refer to individual Series
Project description:ATF6 encodes a transcription factor that is activated during the Unfolded Protein Response to protect cells from ER stress. Loss of ATF6α and its paralog ATF6β, results in embryonic lethality, notochord dysgenesis, and in people, loss of ATF6α specifically, results in malformed neuroretina and congenital vision loss. These phenotypes implicate an essential role for ATF6 during vertebrate development. We investigated the function of ATF6 in development using human stem cells undergoing differentiation into multipotent germ layers, nascent tissues, and organs. We artificially activated ATF6 in stem cells with a recently identified small molecule ATF6 agonist, and we inhibited ATF6 using iPSCs from patients harboring ATF6 mutations. We discovered that ATF6 suppresses pluripotency, enhances differentiation, and surprisingly, guides stem cells toward mesodermal cell fates. Our findings reveal a novel role for ATF6 during differentiation and identify a new strategy to robustly create mesodermal tissues through modulation of the ATF6 arm of the UPR.
Project description:ATF6 is a key regulator of the unfolded protein response. Through use of zebrafish and cultured cells we demonstrate that ATF6 drives fatty liver disease by interaction with fatty acid synthase (FASN).