Unknown,Transcriptomics,Genomics,Proteomics

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Azoxymethane-induced colorectal tumorigenesis in hypertensive rat models

ABSTRACT: To compare the tumor susceptibility between the hypertensive Dahl salt-sensitive rats (S) rat and S.LEW(10)x12x2x3x5 (S.LEW) congenic strain, one of the S.LEW congenic strains our laboratory previously constructed on rat chromosome 10 [Hypertension. 2007 Nov;50(5):891-8], Azoxymethane (AOM)-induced colon tumorigenesis in rats was assessed. At six weeks of age, both S and S.LEW congenic rats received intraperitoneal (IP) injection of AOM in sterial saline at a dose of 15mg/kg body weight once a week for two consecutive weeks. At 30 weeks of age, all the rats were euthanized through carbon dioxide inhalation. The colon tissue was harvested, dissected longitudinally, and washed with saline. The number and size of the colon tumors were recorded. We found that the total number of colon tumors was significantly higher in the S.LEW congenic strain compared with the S rat. To further study the genetic and molecular mechanisms causing the higher tumor susceptibility in the S.LEW congenic strain, we have employed the whole genome microarray expression profiling to identify genes and signaling pathways that are differential between the S and S.LEW congenic strain. At six weeks of age, both S and S.LEW congenic rats received intraperitoneal (IP) injection of AOM in serial saline at a dose of 15mg/kg body weight once a week for two consecutive weeks. At 30 weeks of age, all the rats were euthanized through carbon dioxide inhalation. The colon tissue was harvested, dissected longitudinally, and washed with saline. RNA from the harvested colons of 3 S and 3 S.LEW congenic rats were prepared for the microarray study.

ORGANISM(S): Rattus norvegicus

SUBMITTER: Bina Joe

PROVIDER: E-GEOD-75280 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Through substitution mapping studies, we previously identified that a <330kb region from a rat strain with no renal pathology (the Lewis rat), which when introgressed onto the genetic background of a rat with renal disease (the Dahl Salt-sensitive (S) rat), caused an increase rather than the expected decrease in proteinuria. The purpose of this study was to prioritize a candidate gene and further delineate the mechanism underlying the observed increased in proteinuria. A higher level of proteinuria independent of dietary salt was observed in the congenic rat at a very young age (50-52 day old). The critical congenic segment was further mapped to <42.5kb containing a single candidate gene, rififylin. Rififylin was expressed 1.59 fold higher in the congenic strain compared with S. Overexpression of rififylin is known to delay recycling of endosomes. Renal transcriptome analysis indicated that Atp1a1 one of the most highly differentially expressed genes. Atp1a1 was 5.33 fold higher in the congenic strain compared with S. The protein product of Atp1a1, the alpha subunit of Na+K+ATPase, was also significantly higher in the endosomes of proximal tubules from the congenic strain compared with S. To determine whether the higher amounts of this protein in the endosomes is due to a delay in recycling of endosomes caused by the overexpression of rififylin in the congenic strain, recycling of exogenously labeled-transferrin by single cell cultures of proximal tubules was monitored by confocal microscopy. Recycling of transferrin was significantly delayed in the congenic strain compared with S. These results suggest that impaired endosomal recycling in the proximal tubules from the congenic strain caused by the overexpression of rififylin is a novel molecular mechanism linked to the observed increase in proteinuria of the congenic strain. Three male S control and 3 male congenic S.LEW(10)x12x2x3x5 rats born on the same day were selected, weaned at 30 days of age, and caged with 1 congenic and 1 S rat per cage. They were raised on a low-salt (0.3%) diet (Harlan Teklad diet TD 7034; Harlan–Sprague-Dawley) and sacrificed at 53 days of age and total RNAs were isolated from the kidney. The isolated RNA from each animal was used for the cRNA preparation. cRNA was prepared and fragmented as suggested by Affymetrix technical manual, and simultaneously hybridized (15 µg adjusted cRNA for each chip) to Rat Expression Array 230 2.0 (3' IVT Expression Analysis). Statistical analyses of the microarray data were performed with BH adjustment using R statistical package (version 2.8.1).

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Azoxymethane-induced colorectal tumorigenesis in hypertensive rat models

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