Gene expression profile at bulk (24h, 48h & 72h) and single nucleus (24h) level of mouse right kidney post sham operation and unilateral nephrectomy.
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ABSTRACT: The mechanism driving the remarkable ability of the remaining kidney to enlarge and increase its function following removal of its contralateral pair remains elusive. To explore the pathways driving compensatory renal hypertrophy, comprehensive RNA-seq transcriptional studies in the kidneys of mice undergoing hypertrophy 24, 48 and 72 hours following nephrectomy have been undertaken and compared with mice undergoing sham operations. The results reveal substantial time dependent enhancement of cholesterol biosynthesis pathways, increases in mitochondrial gene expression and cell cycle perturbations. Single nuclei RNA-Seq 24 hours post nephrectomy was used to further explore cholesterol biosynthesis signature and its driver SREBP2. In a cell specific manner, snRNA-seq demonstrated that SREBP2 activity increases in proximal tubules and medullary thick ascending limb and is responsible for cell size regulation following IGF-1 stimulation. These results suggest a previously undescribed role for SREBP2 in the mechanism underlying compensatory renal hypertrophy. This mechanism might be amenable to therapeutic manipulation to enhance kidney size and function.
Project description:The mechanism driving the remarkable ability of the remaining kidney to enlarge and increase its function following the removal of its contralateral pair remains elusive. To explore the pathways driving compensatory renal hypertrophy, comprehensive RNA-seq transcriptional studies were undertaken in the kidneys of C57BL/6 mice undergoing hypertrophy at 24, 48, and 72 hours following nephrectomy, and these results were compared with mice undergoing sham operations. In addition, mass spectrometry was carried out at 24 hours to examine changes in protein expression. Single-nuclei RNA-Seq was used to delineate bulk RNA-seq data into cell types at 24 hours post-nephrectomy. HK-2 renal tubular cells were examined for their ability to undergo hypertrophy in the presence of IGF-1 via the activation of cholesterol biosynthesis pathways. Bulk RNA-seq revealed substantial time-dependent enhancement of cholesterol biosynthesis pathways, increases in mitochondrial gene expression, and cell cycle perturbations. Single-nuclei RNA-Seq at 24 hours post-nephrectomy showed that Sterol Binding Protein 2 (SREBP2) activity increases in medullary thick ascending limb cells and, to a lesser extent, in proximal tubular cells, consistent with the role of promoting cholesterol synthesis. Furthermore, SREBP2 was found to regulate cell size following IGF-1 stimulation in HK-2 cells. There are early, cell-specific alterations in gene expression of cholesterol biosynthesis pathways, mitochondrial genes, and the cell cycle in kidneys undergoing compensatory hypertrophy. SREBP2 activity in the medullary thick ascending limb and, to a lesser extent, in proximal tubules may play a previously undescribed role in promoting cholesterol metabolism in the mechanism underlying compensatory renal hypertrophy.
Project description:This mouse kidney outer cortex proteomics data set is part of multi-omic approach in a mouse unilateral nephrectomy model to identify signaling processes associated with compensatory hypertrophy of the renal proximal tubule.
Project description:Loss of a kidney results in compensatory growth of the remaining kidney, a phenomenon of considerable clinical importance. However, the mechanisms involved are largely unknown. Here, we used a multi-omic approach in a mouse unilateral nephrectomy model to identify signaling processes associated with compensatory hypertrophy of the renal proximal tubule. Morphometry applied to microdissected proximal tubules showed that growth of the proximal tubule involves a marked, rapid increase in cell volume rather than cell number. Measurements of DNA accessibility (ATAC-seq), transcriptome (RNA-seq) and proteome (quantitative protein mass spectrometry) independently identified patterns of change that are indicative of activation of the lipid-regulated transcription factor, PPARα. Activation of PPARα by fenofibrate administration increased proximal tubule cell size, while genetic deletion of PPARα in mice decreased it. The results indicate that PPARα is an important determinant of proximal tubule cell size and is a likely mediator of compensatory proximal tubule hypertrophy.
Project description:Compensation is a physiological response that occurs during chemical exposure to maintain homeostasis. Because compensatory responses are not usually considered adverse effects, it is important to understand compensatory mechanisms for chemical risk assessment. Although the kidney is a major target organ for toxicity, there is controversy over whether hyperplasia or hypertrophy contributes to the compensatory mechanism, and there is limited information to apply for chemical risk assessment. In the current study, compensatory mechanisms of the kidney were investigated in a unilateral nephrectomy (UNx) model using adult male and female rats. In residual kidneys of male and female rats after UNx, 5-bromo-2'-deoxyuridine-labeling indices and mRNA expression of cell cycle-related genes were increased, although there were no fluctuations in mRNA expression of transforming growth factor-β1, which contributes to hypertrophy in renal tubules. Pathway analysis using mRNA expression data from a cDNA microarray revealed that canonical pathways related to cell proliferation were mainly activated and that forkhead box M1 (FOXM1) was an upstream regulator of compensatory cell proliferation in residual kidneys of male and female rats. cDNA microarray for microRNAs (miRNAs) demonstrated that 9 miRNAs were downregulated in residual kidneys, and mRNA/miRNA integrated analysis indicated that miRNAs were associated with the expression of factors downstream of FOXM1. Overall, these results suggested that FOXM1-mediated hyperplasia rather than hypertrophy contributed to compensatory mechanisms in the kidney and that miRNAs regulated downstream FOXM1 signaling. These results will be beneficial for evaluating nephrotoxicity in chemical risk assessment and for developing new biomarkers to predict nephrotoxicity.
Project description:Compensation is a physiological response that occurs during chemical exposure to maintain homeostasis. Because compensatory responses are not usually considered adverse effects, it is important to understand compensatory mechanisms for chemical risk assessment. Although the kidney is a major target organ for toxicity, there is controversy over whether hyperplasia or hypertrophy contributes to the compensatory mechanism, and there is limited information to apply for chemical risk assessment. In the current study, compensatory mechanisms of the kidney were investigated in a unilateral nephrectomy (UNx) model using adult male and female rats. In residual kidneys of male and female rats after UNx, 5-bromo-2'-deoxyuridine-labeling indices and mRNA expression of cell cycle-related genes were increased, although there were no fluctuations in mRNA expression of transforming growth factor-β1, which contributes to hypertrophy in renal tubules. Pathway analysis using mRNA expression data from a cDNA microarray revealed that canonical pathways related to cell proliferation were mainly activated and that forkhead box M1 (FOXM1) was an upstream regulator of compensatory cell proliferation in residual kidneys of male and female rats. cDNA microarray for microRNAs (miRNAs) demonstrated that 9 miRNAs were downregulated in residual kidneys, and mRNA/miRNA integrated analysis indicated that miRNAs were associated with the expression of factors downstream of FOXM1. Overall, these results suggested that FOXM1-mediated hyperplasia rather than hypertrophy contributed to compensatory mechanisms in the kidney and that miRNAs regulated downstream FOXM1 signaling. These results will be beneficial for evaluating nephrotoxicity in chemical risk assessment and for developing new biomarkers to predict nephrotoxicity.
Project description:Compensation is a physiological response that occurs during chemical exposure to maintain homeostasis. Because compensatory responses are not usually considered adverse effects, it is important to understand compensatory mechanisms for chemical risk assessment. Although the kidney is a major target organ for toxicity, there is controversy over whether hyperplasia or hypertrophy contributes to the compensatory mechanism, and there is limited information to apply for chemical risk assessment. In the current study, compensatory mechanisms of the kidney were investigated in a unilateral nephrectomy (UNx) model using adult male and female rats. In residual kidneys of male and female rats after UNx, 5-bromo-2'-deoxyuridine-labeling indices and mRNA expression of cell cycle-related genes were increased, although there were no fluctuations in mRNA expression of transforming growth factor-β1, which contributes to hypertrophy in renal tubules. Pathway analysis using mRNA expression data from a cDNA microarray revealed that canonical pathways related to cell proliferation were mainly activated and that forkhead box M1 (FOXM1) was an upstream regulator of compensatory cell proliferation in residual kidneys of male and female rats. cDNA microarray for microRNAs (miRNAs) demonstrated that 9 miRNAs were downregulated in residual kidneys, and mRNA/miRNA integrated analysis indicated that miRNAs were associated with the expression of factors downstream of FOXM1. Overall, these results suggested that FOXM1-mediated hyperplasia rather than hypertrophy contributed to compensatory mechanisms in the kidney and that miRNAs regulated downstream FOXM1 signaling. These results will be beneficial for evaluating nephrotoxicity in chemical risk assessment and for developing new biomarkers to predict nephrotoxicity.
Project description:Hypercholesterolemia, the driving force of atherosclerosis, accelerates the expansion and mobilization of hematopoietic stem and progenitor cells (HSPCs). The molecular determinants connecting hypercholesterolemia with hematopoiesis are underexplored. Here we report that a novel somite-derived pro-hematopoietic cue, AIBP, orchestrates HSPC emergence from the hemogenic endothelium, a type of specialized endothelium manifesting hematopoietic potential. Mechanistically, AIBP-mediated cholesterol efflux activates endothelial Srebp2, the master transcription factor for cholesterol biosynthesis, which transactivates Notch and promotes HSPC emergence. Srebp2 inhibition impairs hypercholesterolemia-induced HSPC expansion. Srebp2 activation and Notch upregulation are associated with HSPC expansion in hypercholesterolemic human subjects. Genome-wide ChIP-seq, RNA-seq, and ATAC-seq indicate that Srebp2 trans-regulates Notch pathway genes required for hematopoiesis. Our studies outline a novel AIBP-regulated Srebp2-dependent paradigm for HSPC emergence in development and HPSC expansion in atherosclerotic cardiovascular disease.
Project description:We found the genome-wide co-localization of Qki-5 and Srebp2. Notably, the genomic distribution analysis revealed that Qki-5 and Srebp2 highly co-occupied the regions of the promoter/transcription start site (TSS), where active transcription was taken place in a oligodendrocyte-specific manner, which was indicated by Pol II binding events. GO analysis of the genes whose promoters were co-bound by Qki-5, Srebp2, and Pol II showed a significant enrichment of the Srebp2-mediated cholesterol biosynthesis pathway, and Qki depletion led to reduced recruitment of Srebp2 and Pol II on the promoters of the genes involved in cholesterol biosynthesis. These data suggest Qki-5 as a potential transcription co-activator of Srebp2-mediated cholesterol biosynthesis in oligodendrocytes.
Project description:We found the genome-wide co-binding of QKI-5 and SREBP2. Notably, the genomic distribution analysis revealed that the co-binding events between QKI-5 and SREBP2 highly occurred at the regions of the promoter/transcription start site (TSS), where active transcription was taken place in a lens cell-specific manner, which was indicated by POL II binding events. Cellular pathway analysis of the genes whose promoters were co-bound by QKI-5, SREBP2, and POL II showed a significant enrichment of the SREBP2-medaited cholesterol biosynthesis pathway, and QKI depletion led to reduced co-occupancies of SREBP2 and POL II on the promoters of the genes involved in cholesterol biosynthesis. These data suggest QKI-5 as a potential transcription co-activator mediating SREBP2-dependent cholesterol biosynthesis in eye lens cells.
Project description:Immunometabolism is a growing field that centers on a core paradigm: perturbations in metabolism alter a cell’s biological response in immunity and, likewise, inflammatory signals, such as cytokines and pathogens, can directly influence cellular metabolism. Although the carbons within cholesterol cannot be used for catabolic energy production, there is a growing appreciation that a similar relationship exists between cholesterol homeostasis and immunity. The majority of this literature is focused on cholesterol dynamics in the context of leukocyte immunobiology. However, the endothelium also plays an important role during the acute inflammatory response. Endothelial cells (ECs) rapidly respond to extrinsic signals, such as tissue damage or microbial infection, by upregulating factors to activate and recruit circulating leukocytes to the site of injury. Dysregulation or aberrant activation of ECs leads to disease, such as atherosclerosis. I studied the role of cholesterol and its master regulator, SREBP2, in the EC response to acute inflammatory stress. ECs treated with cytokines upregulated SREBP2 cleavage and classical cholesterol biosynthesis gene expression within the late phase of the acute inflammatory response. Furthermore, SREBP2 activation was dependent on NF-kB DNA binding and classical SCAP-SREBP2 processing. We used bacterial cytolysin probes to show that inflammatory stress significantly decreased accessible cholesterol, leading to dysfunctional sterol sensing and downstream SREBP2 cleavage. We also explored what role SREBP2 plays in the EC inflammatory response. Loss of SREBP2 in ECs treated with inflammatory cytokine altered EC phenotype, which was defined by decreased chemokine expression and increased type I inflammatory signaling. Interestingly, this effect on the EC inflammatory transcriptome could not be accounted by changes in cholesterol, but rather through SREBP2 binding to promoters of pro-inflammatory transcription factors. Preliminary results revealed that BHLHE40 and KLF6 are direct targets of SREBP2 and that loss of one of KLF6 could mimic the effect of SREBP2 knockdown on chemokine expression. This study is the first to provide an in-depth characterization of the relationship between SREBP2 and the endothelial acute inflammatory response.