To investigate how the glycosylation of podocyte proteins changes during diabetic kidney disease
ABSTRACT: Podocytes are cells of the visceral epithelium in the kidneys and form a crucial component of the glomerular filtration barrier, contributing to size selectivity and maintaining a massive filtration surface. We are interested in pursuing a microarray analysis to identify the glycosylation-related genes that are modulated in podocytes during insulin and glucose stimulation. As such, we propose to isolate RNA from cultured AB 8/13 human podocyte cell line in their normal state and treated with different concentrations of insulin and glucose. Initially, we would like to analyze 12 samples (Normal control, 2 Starved controls, Insulin experiments 1-4, and glucose experiments 1-5). These experiments would give us information on the gene regulation changes in different healthy and diabetic conditions. In addition to providing possible identification of the unknown proteins involved with diabetic nephropathy, such analysis would provide novel information about early responses by podocytes in response to insulin and glucose level changes in vitro. The results from this analysis will be utilized to focus our research with regard to glycosylation of the proteins in the podocyte slit diaphragm.
Project description:Podocytes form filtration barrier through foot process around glomerualar basement membrane and selectively permit permeability of molecular smaller than albumin. Diabetes can cause podocyte pathological changes leading to high urine albumin level. Diabetic mouse model OVE26 has extremly high urine albumin and previously studies indicated its podocyte damaged. Here we try to find the key genes change in OVE26 diabetic mouse model podocyte by microarray assay while normal FVB mouse podocyte set as control. Podocyte eGFP transgenic mice were made on FVB background and crossbred to OVE26 diabetic model. Glomeruli isolated from OVE-GFP mice were digested by trypsin into signal cell. Podocytes with GFP were sorting out by FACS.
Project description:Podocytes form filtration barrier through foot process around glomerualar basement membrane and selectively permit permeability of molecular smaller than albumin. Diabetes can cause podocyte pathological changes leading to high urine albumin level. Diabetic mouse model OVE26 has extremly high urine albumin and previously studies indicated its podocyte damaged. Here we try to find the key genes change in OVE26 diabetic mouse model podocyte by microarray assay while normal FVB mouse podocyte set as control. Overall design: Podocyte eGFP transgenic mice were made on FVB background and crossbred to OVE26 diabetic model. Glomeruli isolated from OVE-GFP mice were digested by trypsin into signal cell. Podocytes with GFP were sorting out by FACS.
Project description:Podocyte injury is a major determinant in proteinuric kidney disease and identification of potential therapeutic targets for preventing podocyte injury has clinical importance. Here, we show that histone deacetylase Sirt6 protects against podocyte injury through epigenetic regulation of Notch signaling. Sirt6 is downregulated in renal biopsies from patients with podocytopathies and its expression negatively correlates withglomerular filtration rate. Podocyte-specific deletion of Sirt6 exacerbates podocyte injury and proteinuria in two independent mouse models including diabetic nephropathy and adriamycin-induced nephropathy. Sirt6 has pleiotropic protective actions in podocytes including anti-inflammatory and anti-apoptotic effects, is involved in actin cytoskeleton maintenance, and promotes autophagy. Sirt6 also reduces urokinase plasminogen activator receptor expression, which is a key factor for podocyte foot process effacement and proteinuria. Mechanistically, Sirt6 inhibits Notch1 and Notch4 transcription by deacetylating the histone H3K9. We suggest Sirt6 as a potential therapeutic target in proteinuric kidney disease. Overall design: Overexpression of Sirt6 by a Sirt6-adenovirus transfection was used in this study. Cells were stimulated with high glucose for 24h (a final concentration of 40 mmol/l in culture medium).
Project description:We compared mRNA profiles of isolated glomeruli versus sorted podocytes between diabetic and control mice. IRG mice crossed with eNOS-/- mice were further bred with podocin-rTTA and TetON-Cre mice to permanently label podocytes before the diabetic injury. Diabetes was induced by injection of streptozotocin. mRNA profiles of isolated glomeruli and sorted podocytes from diabetic and control mice at 10 weeks after induction of diabetes were examined. Consistent with the previous reports, expression of podocyte-specific markers in the glomeruli were down-regulated in the diabetic mice compared to controls. However, these differences disappeared when mRNA levels were corrected for podocyte number per glomerulus. Interestingly, the expression of these markers was not altered in sorted podocytes from diabetic mice, suggesting that the reduced expression of podocyte markers in isolated glomeruli is likely a secondary effect of reduced podocyte number, rather than the loss of differentiation markers. Analysis of the differentially expressed genes in diabetic mice also revealed distinct up-regulated pathways in the glomeruli (mitochondrial function and oxidative stress) and podocytes (actin organization). In conclusion, our data suggest that podocyte-specific gene expression in transcriptome obtained from the whole glomeruli may not represent those of podocytes in the diabetic kidney. We compared mRNA profiles of isolated glomeruli versus sorted podocytes between diabetic and control mice.
Project description:Podocytes are the highly specialised cells within the glomeruli of the kidney that maintain the filtration barrier by forming interdigitating foot processes and slit-diaphragms. Disruption to these features result in proteinuria. Studies into podocyte biology and disease has been hampered by a paucity of in vitro models of this non-proliferative cell type. Here we characterise sieved glomeruli from kidney organoids derived from human pluripotent stem cells. Compared to conditionally immortalised podocytes, organoid-derived glomeruli show superior podocyte-specific gene and protein expression, morphology and functional properties. Using CRISPR-derived MAFB reporter iPSC lines, homozygous MAFB mutant organoids recapitulated the anticipated disease related transcriptional changes. Culture of kidney organoids on chicken chorioallantoic membrane resulted in glomerular vascularisation, glomerular filtration barrier assembly, formation of slit diaphragms and fenestrated endothelial cells. This definitively demonstrates that human iPSC kidney organoid-derived glomeruli can serve as an accurate model of human podocytopathies and glomerular disease in vitro. Overall design: Gene expression profiling of three immortalised podocyte line samples at 33 degrees celsius, three immortalised podocyte line samples at 37 degrees celsius and three day 25 kidney organoid derived glomeruli
Project description:Kidney podocytes and their slit diaphragms contribute to prevent urinary protein loss. T cell from patients with systemic lupus erythematosus display increased expression of calcium/calmodulin kinase IV (CaMKIV). Here we evaluated the functional role of CaMKIV in lupus nephritis (LN) using kidney biopsy specimens and human podocyte cell line (AB8/13). We found that exposure of podocytes to IgG from LN patients resulted in entry of IgG into the cytoplasm. CaMKIV expression was found to be increased in podocytes of LN kidney biopsy specimens and exposure to IgG from LN patients. IgG entered podocytes using the FcRn receptor because when podocytes where treated with FcRn siRNA less IgG was found in the cytoplasm. The DNA microarray studies of podocytes exposed to LN IgG revealed that genes that are related to the activation of immune cells or podocyte damage were upregulated. These genes included CD86, CaMKIV, PTPN22, PDE5A, CD47 and MALT1. Interestingly, CD86 expression decreased after silencing CaMKIV in podocytes. Also, in situ hybridization experiments showed that the expression of CD86 was reduced in podocytes from MRL/lpr.camkiv−/− mice. IgG from LN patients may enter podocytes through the FcRn and causes the upregulation of a distinct set of genes which may alter podocyte function. Upregulation of CaMKIV appears to precede that of genes known to be linked to podocyte damage such as CD86. These findings may indicate that inhibition of CaMKIV may prove of clinical use in patients with LN. IgG Purification Kits (Dojindo Molecular Technologies, Inc.) are used for isolation and purification of immunoglobulin G of healthy and normal individual according to the manufacturer’s protocol. Flow through the column was used for non IgG binding samples. Cultured human podocytes with IgG purified from sera of normal individuals and LN patient for 24 hr were collected for RNA.
Project description:Available single-cell RNA-seq analyses have revealed that individual cells of the same type differ substantially in gene expression. We wonder whether glomerular podocytes, the cell type that is part of glomerular filtration, also exhibit big difference in gene expression among individual cells; and what biological information could be obtained from the single-podocyte RNA-seq data. Therefore, we isolated mouse glomeruli by Dynabead/magnetic concentration method, and digested them with enzymes to dissociate the cells. We loaded the single cell suspension to a Fluidigm C1 Single-Cell Auto Prep System for single cell cDNA preparation. The cDNA samples were amplified and underwent sequecing using Illumina Highseq 2000 system. Overall design: In total, 20 single podocytes from a C57BL/6 male mouse were analyzed.
Project description:Nephrotic syndrome (NS) occurs when the glomerular filtration barrier becomes excessively permeable leading to massive proteinuria. In childhood NS, dysregulation of the immune system has been implicated and increasing evidence points to the central role of podocytes in the pathogenesis. Children with NS are typically treated with an empiric course of glucocorticoid (Gc) therapy; a class of steroids that are activating ligands for the glucocorticoid receptor (GR) transcription factor. Although Gc-therapy has been the cornerstone of NS management for decades, the mechanism of action, and target cell, remain poorly understood. We tested the hypothesis that Gc acts directly on the podocyte to produce clinically useful effects without involvement of the immune system. In human podocytes, we demonstrated that the basic GR-signalling mechanism is intact and that Gc induced an increase in podocyte barrier function. To gain mechanistic insight we performed RNA microarray and ChIP-sequencing and identified Gc regulation of motility genes.
Project description:Regulated intracellular proteolysis is essential in maintaining the integrity of podocytes and the glomerular filtration barrier of the kidney. Altered proteolytic substrate turnover has been associated with various glomerular diseases ranging from diabetic nephropathy to focal and segmental glomerulosclerosis. However, thus far it has not been possible to systematically identify proteolytically cleaved proteins although some of the proteases have been characterized. Here we applied TAILS to map N-termini in the mouse glomeruli proteome and to determine and quantify N termini in podocyte cell cultures challenged with PAN.
Project description:Glomerular podocyte cells are critical for the function of the renal ultrafiltration barrier. The highly specialized cell-cell junction of podocytes, the slit diaphragm, has a central role in the filtration barrier. Dendrin is a poorly characterized cytosolic component of the slit diaphragm in where it interacts with nephrin and Cd2ap. In this study, we have generated a dendrin knockout mouse line and explored the molecular interactions of dendrin. Dendrin-deficient mice were viable, fertile and had normal life span. To reveal the glomerular gene expression changes in the dendrin knockout mouse, Affymetrix Mouse Genome 430 2.0 Array were used to profiling the dendrin knockout and control glomeruli. Overall design: Three dendrin knockout and three littermate control mice at age of 13 months were used to profile glomerular transcriptomes. Total glomerular RNA was extracted and hyrbridized on the Mouse Genome 430 2.0 Array according to standard procedures.