Unknown,Transcriptomics,Genomics,Proteomics

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Ectopic activation of the immune response in the larval salivary glands

ABSTRACT: Studying the salivary glands potential role during intestinal infections,using advantage from the ingenious GAL4/UAS-system available in the fly Epithelial immunity is a very simple but nevertheless indispensable type of immune response. Amongst all epithelial tissues, the intestine and the airways are outstanding, because they provide huge surface areas, where colonization or invasion of potential pathogens has to be obviated. The intestine is of special interest, because it has to hold the balance between tolerance and immunity, to protect the own microbial flora. An essential part of the intestinal tract has been completely overlooked, the salivary glands. They are the gatekeepers of the intestinal system, being essential for various aspects of the intestineâs immunity. Using the bipartite Gal4/UAS expression system, it is possible to activate the immune system ectopically in different organs of the fly. Activation of the IMD-pathway in the salivary glands is possible; because a very specific driver line is available that directs expression of any gene of interest into the salivary glands only. Flies, where the IMD-pathway in the salivary glands has been activated have a very distinct phenotype. They show a smaller body length as well as a smaller salivary gland length than the parental animals Microarray data analysis showed that 457 genes were upregulated and 578 genes downregulated. Interestingly, the sets of regulated genes show only a very small overlap with the canonical set of Drosophila immune genes. Other physiological scenarios such as autophagic cell death are apparently also not activated upon IMD-pathway activation. Among the regulated genes, those that code for signaling associated protease activity are significantly modulated. This holds especially true for presenilin and the signal peptide peptidase. The comparison of the transcriptional events induced following IMD-activation in the trachea and the salivary glands shows also only a small overlap, indicating that the general IMD-activated core transcriptome is rather small. In conclusion, the salivary glands may a very good tool to study the physiological role of selected genes that are of importance for human health such as the Alzheimerâs disease related presenilin gene in a functional environment. Ectopic activiation of the Immune deficiency pathway in the larval salivary glands using the Gal4/UAS-system of Brand and Perrimon. The activation was induced by the overexpression of the pattern recognition receptor PGRP-LCx using a driver line which was specific for the salivary glands.In general four replicates were performed including dye-swaps in two-colour arrays.

ORGANISM(S): Drosophila melanogaster

SUBMITTER: Thomas Roeder

PROVIDER: E-GEOD-20938 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:When misexpressed in late Drosophila prepupae, the transcription factor Senseless (Sens) blocks death of the larval salivary glands that normally occurs in the early pupa. The aim of the experiment was to identify genes responding to Sens that might mediate the effect of the protein on cell death and other biological processes. The yeast transcription factor GAL4, expressed from a heat-inducible transgene (P{GAL4-Hsp70.PB}89-2-1), was used to drive expression of Sens from a UAS-sens transgene. After crossing the GAL4 and UAS lines, expression of GAL4 was induced by a 30-min heat shock treatment (37 Â°C) of the progeny at 9 hours after puparium formation. Salivary glands were dissected at 14 hours after puparium formation and RNA isolated for microarray analysis with Affymetrix GeneChips. Control samples were obtained from animals treated the same way carrying one copy of the GAL4 transgene (progeny of a cross between flies of the P{GAL4-Hsp70.PB}89-2-1 and w1118 strains) and w1118 animals. The microarray data identified several genes associated with programmed cell death, including caspase genes, which respond to Sens. In addition, the data show that many Drosophila genes respond to the yeast transcription factor GAL4 in a UAS-independent manner. To identify target genes of Sens that are of biological relevance, gene expression patterns in the presence of Sens were compared to gene expression patterns in both the presence and the absence of GAL4. This comparison revealed that Sens seems to preferentially downregulate targets that are upregulated by GAL4, suggesting that these genes may not necessarily constitute true transcriptional targets of Sens. Experiment Overall Design: Experimental RNA samples were obtained in 3 biological replicates from sens-expressing salivary glands (SG_sens_14APF_rep1, SG_sens_14APF_rep2, SG_sens_14APF_rep3) and compared to control samples obtained from GAL4-expressing salivary glands (SG_1P{hsGAL4}89(S)_14APF_rep1) and non-GAL4-expressing salivary glands (SG_w1118_14APF_rep1, SG_w1118_14APF_rep2). All samples were compared using dChip and normalized to the same baseline array (median intensity 150).

Project description:The yeast transcription factor GAL4 has been reported to cause cell death and to have other biological effects when expressed in Drosophila (Kramer and Staveley, 2003: Genet. Mol. Res. 2, 43; Rezaval et al., 2007: Eur. J. Neurosci. 25, 683). Using heat-shock-induced expression of GAL4 to drive expression of a UAS-senseless responder gene in transcriptional profiling experiments, we found that the underlying cause of these effects might be a genomic response to GAL4. To further characterize this response and to account for GAL4-independent changes caused by the transgene integration, GAL4 was expressed from two copies of the transgene in two independent lines, P{GAL4-Hsp70.PB}89-2-1 (short P{hs-GAL4}89) and P{hs-GAL4}X1. In addition, GAL4 was expressed from only one copy of the transgene in P{hs-GAL4}89 prepupae to account for the dosage dependence of observed effects. Prepupae carrying the hs-GAL4 transgenes were subjected to a 30-min heat shock treatment (37 Â°C) at 9 hours after puparium formation. RNA was isolated from salivary glands dissected from these and similarly treated w1118 control animals at 14 hours after puparium formation and subjected to microarray analysis with Affymetrix GeneChips. The microarray data identified an overlapping set of 1,009 genes that showed an at least 1.5-fold change in expression in both of the GAL4-expressing lines, defining a core set of GAL4-responsive genes in the salivary glands. This set includes genes involved in the control and execution of programmed cell death and in other important regulatory pathways. Experiment Overall Design: Experimental RNA samples were obtained from GAL4-expressing salivary glands of the line P{hs-GAL4}X1 in 3 biological replicates (SG_P{hsGAL4}X1_14APF_rep1, SG_P{hsGAL4}X1_14APF_rep2, SG_P{hsGAL4}X1_14APF_rep3); of the line P{hs-GAL4}89 in one replicate (SG_P{hsGAL4}89_14APF_rep1); of animals carrying only one copy of P{hs-GAL4}89 in one replicate (SG_1P{hsGAL4}89_14APF_rep1). The samples were compared to control samples obtained in two biological replicates from the salivary glands of w1118 control animals (SG_w1118(2)_14APF_rep1, SG_w1118(2)_14APF_rep2). All samples were compared using dChip and normalized to the same baseline array (median intensity 145). Statistical analysis of differences between the P{hs-GAL4}X1 and w1118 samples was carried out using GeneSpring (Agilent Technologies) and a false discovery rate (FDR) cutoff of 0.05.

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Ectopic activation of the immune response in the larval salivary glands

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