Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling of two rat cell lines using different blocking reagents and doses to optimize cDNA microarray procedures without using an external standard

ABSTRACT: We performed a dye-swap microarray experiment using a total of 24 Rat 15k cDNA duplicates microarrays. The study included RNA from samples with high expected differential gene expression termed high contrasts compared to self-self hybridization (rat cell lines AR42J and NRK52E). We than optimized a pipeline to maximize the number of genes found differentially expressed between the two different RNA samples while at the same time making sure that the methodology finds no differentially expressed genes in selfself experiments with the same cell lines. In this high-contrast vs. self-self method (HCSSM) significantly expressed genes is determined by estimating the false discovery rate (FDR) using a null distribution obtained from self-self experiment. The optimization criterion requires only 4 microarrays per evaluation, and the effects of blocking reagent dose, filtering, and background corrections methodologies were investigated. In our experiments a dose of 250 ng LNA dT blocker gave the highest number of differentially expressed genes. When the criterion was used to evaluate steps in the computational analysis of microarray data we found that no background correction and weight based filtering gave the largest number of differentially expressed genes. Background correction method, however, has a greater influence on the number of differentially expressed genes found than filtering.

ORGANISM(S): Rattus norvegicus

SUBMITTER: Hallgeir Bergum

PROVIDER: E-TABM-202 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Inferring the heritability of gene expression is one of the main areas of the field of genetical genomics. With the possibility to treat the abundances of gene transcripts as a suite of quantitative traits, genetical genomics can make an extensive use of the microarray technology. Here we extended a major method for estimating the heritability of a quantitative trait, single parent-offspring regression, to assess the heritability of the expression of genes with two-channel microarrays. In a series of maternal parent-offspring pairs of Interior spruce (Picea glauca x engelmannii, our focus in the outer stem tissues is the expression of defense-related genes, the heritability of which can affect fitness and necessary for evolution by natural selection. Parent-offspring pairs of Interior spruce planted as a part of Tree Breeding and Improvement Program of the Forest Genetics Section, British Columbia Ministry of Forests and Range, Prince George, BC, Canada (http://www.for.gov.bc.ca/hre/forgen/interior/spruce.htm#1) were used. A total of 30 trees, comprising 15 parent-offpsring pairs were sampled. These include15 offsprings and 15 maternal parents (grafts), which were planted within ~ 1Km range west (122º 42’ 43’’W, 53º 45’41’’N) of the offsprings, hence grown in a relatively similar environment. The bark and the attached phloem were separated from inner layers in the mid-morning hours of June 25, 2008, flash-frozen in liquid nitrogen, and transferred into separate containers. A chain design was decided for gene expression profiling (a total of 45 slides) using the Treenomix third generation cDNA microarray platform (GEO accession #: GPL5423). Array350 kit (Genisphere, Hatfield, USA) was chosen for the microarray hybridizations. The slides were scanned with a ProScanArray scanner (PerkinElmer, Downers Grove, IL, USA), and the scanned TIF images were processed by ImaGene software (BioDiscovery, Inc., El Segundo, CA, USA) to quantify spot signals. Normalization was done between arrays using variance stabilizing (VSN) method for ratio based analysis of the expression data.

Project description:The proliferative darkening syndrome (PDS) is an annually recurring disease that causes species-specific die-off of brown trout (Salmo trutta fario) in PDS-impacted pre-alpine rivers of central Europe. The mortality rate for PDS is near 100% and consequently the survival of brown trout populations in the impacted regions is threatened. The progression of PDS occurs in two stages, a subclinical stage and a symptomatic stage, over a time period of more than 3 months starting in spring and culminating with the die-off of brown trout in late summer. Based on experimental evidence it is hypothesized that PDS is caused by an infectious agent. To substantiate this working hypothesis as well as to discern the type of pathogen likely to be responsible for PDS, microarray analysis were conducted using a salmonid-specific cDNA microarray to assess the hepatic immune response of brown trout during the progression of PDS in 7-day intervals over a time period of 98 days.The microarray analysis revealed that brown trout suffering from PDS exhibit increased hepatic expression of important anti-viral genes both during the subclinical stage of PDS, namely the Barrier-to-autointegration factor, and during the symptomatic stage of PDS, namely the interferon regulatory factor 1 as well as the Guanylate-binding protein 1. Additionally, during the symptomatic stage of PDS there is strong hepatic up-regulation of the chemokine CCL19, complement components C1QC and C6, Proteasome activator complex subunits 1 and 2 as well as a variety of both MHC class I and MHC class II transcripts. In conclusion, the increased expression of hepatic immune response genes involved in a variety of immune system processes that mediate defense against infection identified by the microarray analysis during the progression of PDS support the working hypothesis that PDS is caused by an infectious agent. Furthermore, the up-regulation of antiviral immune response genes during both the subclinical stage and the symptomatic stage of PDS suggests that this disease is caused by a pathogenic virus. On May 29, 2008, brown trout (Salmo trutta fario) of the same age class (1+) with an individual weight ranging between 25-85 grams were obtained from a single hatchery (Schwäbischer Fischereihof Salgen, Fachberatung für Fischerei Schwaben, Germany) and randomly allocated to one of two different experimental stations that are both located along the Iller river, named here simply the control station (location by Oberstdorf, Germany) and the treatment station (location by Kempten, Germany). At both experimental stations brown trout were held in tanks (n=750 at the treatment station and n=70 at the control station) that were supplied with water from the Iller river in a flow-through system. Sampling at both experimental stations started on May 29, 2008, which was also the day on which the fish were first transferred to their exposure tanks (referred to as 0 day post exposure; d.p.e), and ended on the 5th of September 2008. At the treatment station 3 fish were sampled each day (always at 2pm), whereas at the control station 3 fish were sampled in 7-day intervals (always at 12 noon). Fish were anaesthetized by a blow to the head and organ tissue of interest (liver, kidney, spleen, gill, muscle, stomach and foregut tissue) were immediately harvested from sacrificed fish, snap-frozen in liquid nitrogen and subsequently stored at -80°C. Livers from the three brown trout (n=3) that were sampled concurrently from both treatment and control group (n=2) in 7-day intervals starting 7 d.p.e (7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91 and 98 d.p.e; n=14) were recruited for the use in the microarray analysis. Microarray analyses were performed using a direct comparison two-channel design in which equimolar amounts of liver sample of one brown trout from both treatment and control group were co-hybridized on the same microarray. For each time point (n=14) microarray co-hybridizations were repeated in triplicate (n=3) and included one dye-swap in order to reduce dye-bias. Thus a total of 42 microarray slides were used in this study (3 biological replicate microarrays x 14 time points = 42 microarrays).

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Transcription profiling of two rat cell lines using different blocking reagents and doses to optimize cDNA microarray procedures without using an external standard

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