Project description:To establish the role of proximal tubular hypoxia in diabetic kidney disease, we use a mouse line with a specific deletion of von-Hippel-Lindau (VHL) in the proximal tubule and treat them with streptozotocin (STZ) to induce a type I diabetes mellitus. 10 weeks after induction of diabetes mellitus samples were collected.
Project description:We and others have previously shown that glomerular endothelial cells and podocytes express hypoxia-inducible transcription factors (HIFs). HIFs bind to hypoxia response elements in target genes, such as vascular endothelial growth factor, which is continually produced by podocytes throughout life. To further assess function of HIFs in podocyte biology, podocin-Cre mice were mated with floxed von Hippel-Lindau (VHL) mice to selectively delete VHL, a component of an E3 ligase complex responsible for degradation of HIFs in normoxia. We reasoned that cells lacking VHL would overexpress stable HIFs and upregulate hypoxia-responsive genes. Progeny from these crosses displayed two phenotypes, non-proteinuric with glomerular basement membrane (GBM) defects and proteinuric with GBM defects and end-stage renal failure at ~6 months of age. Gene changes associated with the mild, non-proteinuric phenotype were studied using isolated glomeruli from wildtype and Pod-Cre fVHL mice.
Project description:We and others have previously shown that glomerular endothelial cells and podocytes express hypoxia-inducible transcription factors (HIFs). HIFs bind to hypoxia response elements in target genes, such as vascular endothelial growth factor, which is continually produced by podocytes throughout life. To further assess function of HIFs in podocyte biology, podocin-Cre mice were mated with floxed von Hippel-Lindau (VHL) mice to selectively delete VHL, a component of an E3 ligase complex responsible for degradation of HIFs in normoxia. We reasoned that cells lacking VHL would overexpress stable HIFs and upregulate hypoxia-responsive genes. Progeny from these crosses displayed two phenotypes, non-proteinuric with glomerular basement membrane (GBM) defects and proteinuric with GBM defects and end-stage renal failure at ~6 months of age. Gene changes associated with the mild, non-proteinuric phenotype were studied using isolated glomeruli from wildtype and Pod-Cre fVHL mice. At 4 weeks of age, urine was collected and urinary albumin was quantified by Albuwell elisa from Pod-Cre fVHL litters. At 6 weeks of age, glomeruli from 3 wildtype littermate controls and 3 non-proteinuric Pod-Cre fVHL mice were collected using the magnetic bead method. RNA was extracted and hybridized to Affymetrix microarrays.
Project description:The von Hippel-Lindau (VHL) tumor suppressor functions as a ubiquitin ligase that mediates proteolytic inactivation of hydroxylated a subunits of hypoxia-inducible factor (HIF). Although studies of VHL defective renal carcinoma cells suggest the existence of other VHL tumor suppressor pathways, dysregulation of the HIF transcriptional cascade has extensive effects that make it difficult to distinguish whether, and to what extent, observed abnormalities in these cells represent effects on pathways that are distinct from HIF. Here, we report on a genetic analysis of HIF dependent and independent effects of VHL inactivation by studying gene expression patterns in C. elegans. We show tight conservation of the HIF-1/VHL-1/EGL-9 hydroxylase pathway. However, persisting differential gene expression in hif-1 versus hif-1; vhl-1 double mutant worms clearly distinguished HIF-1 independent effects of VHL-1 inactivation. Genomic clustering, predicted functional similarities, and a common pattern of dysregulation in both vhl-1 worms and a set of mutants (dpy-18, let-268, gon-1, mig-17 and unc-6), with different defects in extracellular matrix formation, suggest that dysregulation of these genes reflects a discrete HIF-1 independent function of VHL-1 that is connected with extracellular matrix function. Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Bishop T, Lau KW, Epstein AC, Kim SK, Jiang M, O'rourke D, Pugh CW, Gleadle JM, Taylor MS, Hodgkin J, Ratcliffe PJ, Genetic Analysis of Pathways Regulated by the von Hippel-Lindau Tumor Suppressor in Caenorhabditis elegans., Bishop T, et al. (2004) PLoS Biol 2(10):e289, 2004-10-01, http://biology.plosjournals.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020289 Computed
Project description:The cellular response to low oxygen supply is mediated by hypoxia-inducible factors (HIF). Under hypoxic conditions, HIF is stabilized and target genes are induced. Under normoxia, however, HIF is ubiquitinated through the von Hippel-Lindau protein (VHL), which results in proteasomal degradation. HIF activation leads to induction of genes involved in erythropoiesis, angiogenesis, and cell survival. Furthermore, HIF orchestrates a metabolic shift from oxidative phosphorylation to glycolysis to facilitate ATP production under low oxygen conditions. We used microarrays to detail gene expression changes in kidneys with stable HIF activation in renal tubules, which was achieved by tubule-specific VHL ablation.
Project description:The effects of constitutively active Hypoxia Inducible Factor (HIF) and inactivated von Hippel-Lindau tumor suppressor gene product (pVHL) were examined in a mouse model. Conditionally expressed, constitutively active HIF-1a and HIF-2a were compared with inactivated pVHL.
Project description:The von Hippel-Lindau (VHL) tumor suppressor functions as a ubiquitin ligase that mediates proteolytic inactivation of hydroxylated a subunits of hypoxia-inducible factor (HIF). Although studies of VHL defective renal carcinoma cells suggest the existence of other VHL tumor suppressor pathways, dysregulation of the HIF transcriptional cascade has extensive effects that make it difficult to distinguish whether, and to what extent, observed abnormalities in these cells represent effects on pathways that are distinct from HIF. Here, we report on a genetic analysis of HIF dependent and independent effects of VHL inactivation by studying gene expression patterns in C. elegans. We show tight conservation of the HIF-1/VHL-1/EGL-9 hydroxylase pathway. However, persisting differential gene expression in hif-1 versus hif-1; vhl-1 double mutant worms clearly distinguished HIF-1 independent effects of VHL-1 inactivation. Genomic clustering, predicted functional similarities, and a common pattern of dysregulation in both vhl-1 worms and a set of mutants (dpy-18, let-268, gon-1, mig-17 and unc-6), with different defects in extracellular matrix formation, suggest that dysregulation of these genes reflects a discrete HIF-1 independent function of VHL-1 that is connected with extracellular matrix function. Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Bishop T, Lau KW, Epstein AC, Kim SK, Jiang M, O'rourke D, Pugh CW, Gleadle JM, Taylor MS, Hodgkin J, Ratcliffe PJ, Genetic Analysis of Pathways Regulated by the von Hippel-Lindau Tumor Suppressor in Caenorhabditis elegans., Bishop T, et al. (2004) PLoS Biol 2(10):e289, 2004-10-01, http://biology.plosjournals.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020289 Keywords: Logical Set
Project description:Understanding the nature of the various glucose-derived signals for insulin secretion (both triggering and amplifying) is essential for gaining insight into the functional failure of the beta-cells in diabetes and the development of drugs for correcting this problem. The beta-cells uniquely couple changes in cellular metabolism to electrical activity and thus insulin release. In mice, beta-cell specific deletion of the von Hippel-Lindau (VHL) tumor suppressor protein leads to the activation of a HIF transcription program that includes genes involved in glycolysis, suppression of mitochondrial activity and lactate production. This reprogramming of cellular metabolism results in abnormal insulin secretion properties. Experiment Overall Design: Three batches of isolated islets from each genotype where used for RNA isolation and Affymetrix measurements.