Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling of rat proximal and distal colonic epithelium after azoxymethane treatment

ABSTRACT: Comparison of global gene expression in the proximal and distal colonic epithelium in azoxymethane treated rats. Experiment Overall Design: Ten male Sprague Dawley rats weighing approximately 245 Â± 14.5 g were housed in wire-bottomed caging in a temperature controlled room (22-24Â°C) with a 12 h light/dark cycle. They were randomly allocated into two groups (n=5) with approximately equal body weights. They were given free access to water and modified AIN-93G diet for 10 days when they were injected with 15 mg of AOM/kg subcutaneously (Sigma Chemical Co., St. Louis, MO, USA). They were anaesthetised with isoflurane and killed by exsanguination six hours after injection. The large bowel (excluding the rectum) was removed, opened longitudinally along the mesenteric border and digesta removed. The colon was rinsed clean with PBS and transferred to a chilled ceramic plate. The most distal and the most proximal 0.5 cm were discarded. Mucosal samples for gene expression and protein analyses were collected by scraping the next 4 cm of proximal and distal colon with new microscope slides. Experiment Overall Design: The mucosal scraping was transferred into RNAlater (Sigma Chemical Co., St. Louis, MO, USA) and stored at -80oC for later processing. All instruments were replaced or cleaned thoroughly between animals. All procedures involving animals were approved by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Human Nutrition Animal Ethics Committee and complied with the Australian code of practice (2004). Experiment Overall Design: The distal and proximal colonic mucosal samples were removed from the RNAlater stabilisation reagent (Sigma, Australia) and placed in 1ml of TRIzolÂ® Reagent (Invitrogen, Sydney, N.S.W., Australia). Samples were then homogenised using beads (mix of 2.5mm glass and 0.1 - 1.0mm diameter silicon-zirconian beads) in a MiniBeadbeater-8â¢ (BioSpec Products Inc. Oklahoma, US). Total RNA was then extracted according to the TRIzolÂ® Reagent manufacturerâs instruction after which samples were further purified using RNAeasy mini spin columns (QIAGEN, Doncaster, Victoria, Australia) with a DNase on-column digestion as per the manufactureâs instructions. The integrity of the RNA was checked using a Bioanalyzer 2100 (Agilent Technologies) and quantified using a NanoDropÂ® ND-1000 Spectrophotometer. Experiment Overall Design: RNA (4.5ug) samples were processed for Microarray expression analysis using high-density oligonucleotide arrays (AffymetrixÂ® GeneChip array, AffymetrixÂ®, Santa Clara, CA, USA) commensurate with the manufacturerâs instructions.

ORGANISM(S): Rattus norvegicus

SUBMITTER: Caroline Audrey Kerr

PROVIDER: E-GEOD-13802 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Goal: Since disease susceptibility of the intestine exhibits an anatomical bias, we propose that the chromatin landscape, especially the site-specific epigenetic differences in histone modification patterns throughout the longitudinal axis, contributes to a differential response to chemoprotective agents. Method: We assessed the chromatin structure associated with gene expression profiles in the rat proximal and distal colon by globally correlating chromatin immunoprecipitation next-generation sequencing analysis (ChIP-Seq) with mRNA transcription (RNA-Seq) data. Crypts were isolated from the proximal and distal colonic regions from rats maintained on a semi-purified diet, and mRNA gene expression profiles were generated using RNA-Seq. The remaining isolated crypts were paraformaldehyde-crosslinked and chromatin immunoprecipitated using antibodies against H3K4me3, H3K9me3, and RNA Polymerase II. Results/Conclusion: Globally, RNA-Seq results indicated that 9,866 genes were actively expressed, of which 540 genes were differentially expressed between the proximal and distal colon. With regard to differentially expressed genes, a high correlation was observed between H3K4me3-Seq and RNA-Seq data, with 96% of the canonical pathways being similarly affected in the H3K4me3-Seq and RNA-Seq data sets. Gene ontology analysis indicated that colonic crypt location significantly impacted both chromatin and transcriptional regulation of genes involved in cell transformation, lipid metabolism, lymphatic development and immune cell trafficking. Gene function analysis indicated that the PI3-Kinase signaling pathway was regulated in a site-specific manner, e.g., pathway proto-oncogenes, c-Jun, c-Fos and ATF, were up-regulated in the distal colon. Middle and long non-coding RNAs (lncRNAs) were also detected in the colon, including select lncRNAs formerly only detected in the rat nervous system. In summary, distinct combinatorial patterns of histone modifications exist in the proximal versus distal colon. These site-specific differences may explain the differential effects of chemoprotective agents on cell transformation in the ascending (proximal) and descending (distal) colon. Examination of mRNA profiles and 2 different histone modifications (H3K4me3 and H3K9me3) in 2 tissue types (proximal and distal colon).

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Transcription profiling of rat proximal and distal colonic epithelium after azoxymethane treatment

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