Project description:TGF-beta1 is a pleiotropic cytokine that regulates multiple cellular functions including cell proliferation, differentiation, and apoptosis. It has been identified as one of the mediators of renal hypertrophy and accumulation of extracellular matrix proteins in the diabetic glomerular mesangium. Previous results from our and other laboratories indicate that TGF-beta1 mediates some of the effects of high glucose and glucosamine on extracellular matrix gene expression in mesangial cells. The global regulatory mechanism(s), however, still remains to be understood. In this study, we have utilized an in vitro model of mouse mesangial cells (MES-13) to investigate the genetic effects of TGF-beta1 on global patterns of gene expression, transcriptome and signaling networks. A total number of 179 genes are regulated by TGF-beta1 in MES-13 cells at 2.0-fold, which cover across 44 physiological processes, 31 metabolic functions, and 11 major signaling pathways. We observed that several genes regulated by high glucose and glucosamine are also targeted by TGF-beta1 in MES-13 cells such as thioredoxin interacting protein, glutathione S-transferase theta 1, selenium binding protein 1, inhibitor of DNA binding 2, and plasminogen activator inhibitor-1. The results of this study further support the hypothesis that some effects of high glucose and glucosamine on mesangial gene expression are mediated by TGF-beta1. The identification of these common genes will help us to investigate further their roles in the development and progression of diabetic kidney disease. Cell culture: Stable murine mesangial (MES-13) cells transformed with non-capsid-forming SV-40 virus were obtained from the ATCC, Manassas, VA. These cells display a differentiated mesangial cell phenotype including the typical spindle-like appearance, positive staining for vimentin and desmin, and contraction in response to ANG II and expression of AT1 receptor. The cells were maintained in DMEM and F-12 Nutrient Mixture (Ham's) (4:1 ratio) (GIBCO BRL, Gaithersburg, MD) containing a normal D-glucose concentration of 5.5 mmol/L, 2% FCS, 100 µg/ml streptomycin, 100 U/ml penicillin, and 2 mmol/L glutamine (26). The cells were incubated in a humidified incubator of 5% CO2 at 37 °C and routinely passaged at confluence every 3 days by trypsinization using 10-cm culture dishes. Approximately 50% confluent monolayers were starved in the above medium without FCS for 1 day and then incubated in the starvation medium with 100 ng/ml TGF-beta1 for 24hrs. Total RNA isolation, cDNA and cRNA synthesis and genechip hybridization: Total RNA was isolated using Trizol reagent (Life Technologies, Inc., Massachusetts). cDNA and cRNA synthesis, genechip hybridization, and scanning of the Affymetrix murine expression U430 2.0 chips (the Affymetrix M430 2.0 chip contains 39,000 transcripts targeted at 34,000 well characterized genes) were performed according to the manufacturer's protocol (Affymetrix, Santa Clara, CA). Briefly, 5 mg of RNA was converted into double-stranded cDNA by reverse transcription using a cDNA synthesis kit (SuperScript Choice, Life Technologies, Inc., MA) with an oligo(dT)24 primer containing a T7 RNA polymerase promoter site added 3' of the poly(T) (Genset, La Jolla, CA). After second-strand synthesis, labeled cRNA was generated from the cDNA sample by an in vitro transcription reaction supplemented with biotin-11-CTP and biotin-16-UTP (Enzo, Farmingdale, NY). The labeled cRNA was purified by using RNeasy spin columns (Qiagen, Valencia, CA). 15 mg of each cRNA was fragmented at 94 °C for 35 min in fragmentation buffer (40 mM Tris acetate, pH 8.1, 100 mM potassium acetate, 30 mM magnesium acetate) and then used to prepare 300 ml of hybridization mixture (100 mM MES, 0.1 mg/ml herring sperm DNA (Promega), 1M sodium chloride, 10 mM Tris, pH 7.6, 0.005% Triton X-100) containing a mixture of control cRNAs samples were heated at 94 °C for 5 min, equilibrated at 45 °C for 5 min, and clarified by centrifugation (14,000 x g) at room temperature for 5 min. Aliquots of each sample (10 mg of cRNA in 200 ml of the master mix) were hybridized to GeneChip Mouse Genome 430 2.0 Array at 45 °C for 16 h in a rotisserie oven set at 60 rpm, then washed with non stringent wash buffer (6x saline/sodium phosphate/EDTA) at 25 °C, followed by stringent wash buffer (100 mM MES (pH 6.7), 0.1 M NaCl, 0.01% Tween 20) at 50 °C, stained with streptavidin-phycoerythrin (Molecular Probe), washed again with 6x saline/sodium phosphate/EDTA, stained with biotinylated anti-streptavidin lgG, followed by a second staining with streptavidin-phycoerythrin, and a third washing with 6x saline/sodium phosphate/EDTA using the GeneChip Fluidics Station 450. The arrays were then scanned using a GeneChip Scanner 3000 (Affymetrix). Each experiment was repeated twice. Microarray Data analysis: The chips were read with Affymetrix GCOS v1.2, and the probe intensity files were modeled with DChip 1.3 (Harvard School of Public Health) in both PM-only and PM-MM modes. Consensus differentially regulated genes were initially derived from repeat experiments on the bases of a 90% CI of greater than 2-fold change in expression and with p<0.05 of error in paired t-test across repeats. This was further validated through modeling of variance between sample groups (one-way ANOVA) conducted in GeneSpring 6.0 (Silicon Genetix). The consensus gene-set was clustered in DChip and GeneSpring 6.0, with OntoExpress (Wayne State University) to explore ontological associations. Further ontological and pathway analyses were conducted with the GeneGo software and NIH's DAVID bioinformatics programs (heep://appls.niaid.nih.gov/david).
2008-06-12 | E-GEOD-2558 | biostudies-arrayexpress
