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Global analysis of alternative splicing regulation by insulin and wingless signalling in Drosophila cells

ABSTRACT: Background: Despite the prevalence and biological relevance of both signalling pathways and alternative pre-mRNA splicing, our knowledge of how intracellular signalling impacts on alternative splicing regulation remains fragmentary. We report a genome-wide analysis of changes in alternative splicing using splicing-sensitive microarrays, induced by activation of two distinct signalling pathways, insulin and wingless, in Drosophila cells in culture. Results: Alternative splicing changes induced by insulin affect more than 150 genes and more than 50 genes are regulated by wingless activation. About 40% of the genes showing changes in alternative splicing also show regulation of mRNA levels, suggesting distinct but also significantly overlapping programs of transcriptional and posttranscriptional regulation. Distinct functional sets of genes are regulated by each pathway and, remarkably, a significant overlap is observed between functional categories of genes regulated transcriptionally and at the level of alternative splicing. Functions related with carbohydrate metabolism and cellular signalling are enriched among genes regulated by insulin and wingless, respectively. Computational searches identify pathway-specific sequence motifs enriched near regulated 5’ splice sites. Conclusion: Taken together, our data indicate that signalling cascades trigger pathway-specific and biologically coherent regulatory programs of alternative splicing regulation. They also reveal that alternative splicing can provide a novel molecular mechanism for cross-talk between different signalling pathways.

ORGANISM(S): Drosophila melanogaster

PROVIDER: GSE14085 | GEO | 2009/01/21

SECONDARY ACCESSION(S): PRJNA112511

REPOSITORIES: GEO

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Project description:Background: Despite the prevalence and biological relevance of both signalling pathways and alternative pre-mRNA splicing, our knowledge of how intracellular signalling impacts on alternative splicing regulation remains fragmentary. We report a genome-wide analysis of changes in alternative splicing using splicing-sensitive microarrays, induced by activation of two distinct signalling pathways, insulin and wingless, in Drosophila cells in culture. Results: Alternative splicing changes induced by insulin affect more than 150 genes and more than 50 genes are regulated by wingless activation. About 40% of the genes showing changes in alternative splicing also show regulation of mRNA levels, suggesting distinct but also significantly overlapping programs of transcriptional and posttranscriptional regulation. Distinct functional sets of genes are regulated by each pathway and, remarkably, a significant overlap is observed between functional categories of genes regulated transcriptionally and at the level of alternative splicing. Functions related with carbohydrate metabolism and cellular signalling are enriched among genes regulated by insulin and wingless, respectively. Computational searches identify pathway-specific sequence motifs enriched near regulated 5â splice sites. Conclusion: Taken together, our data indicate that signalling cascades trigger pathway-specific and biologically coherent regulatory programs of alternative splicing regulation. They also reveal that alternative splicing can provide a novel molecular mechanism for cross-talk between different signalling pathways. To monitor transcriptional and alternative splicing changes induced by activation of the insulin and wingless pathways, a custom-designed microarray platform was employed featuring probes for all Drosophila genes for which different mRNA isoforms generated by alternative splicing have been described (see Blanchette M, Green RE, Brenner SE, Rio DC: Global analysis of positive and negative pre-mRNA splicing regulators in Drosophila. Genes Dev 2005, 19(11):1306-1314.). Three biological replicates of total RNA isolated after pathway activation or controls (untreated cells for insulin, control dsRNA for wingless) were purified, reverse transcribed into cDNA and labelled with Cy5 or Cy3 fluorochromes and the cDNA was hybridized to the microarray,

Project description:To identify genes associated with lung cancer progression, we examined gene expression profiles of tumor cells from 20 patients with primary, untreated non-small cell lung cancer (10 adenocarcinomas (AC) and 10 squamous cell carcinomas (SCC)) in comparison to lung tissue of 23 patients with stage IIIB or stage IV non-small cell lung cancer (15 AC and 8 SCC). Bronchoscopical biopsies from patient with recurrent lung tumor were taken after initial treatment. Cancer cells were isolated using laser capture microdissection in order to obtain pure samples of tumor cells. For expression analysis, microarrays covering 8793 defined genes (Human HG Focus Array, Affymetrix) were used. Array data were normalized and analysed for significant differences using variance stabilizing transformation (VSN) and significance analysis of microarrays (SAM), respectively. Genes were considered to be up- or down-regulated when the ratio between primary and recurrent tumor samples were at least 1.5-fold differentially expressed with an estimated false discovery rate: < 5%. Based on differentially expressed genes, primary cancer samples could be separated from recurrent tumor samples. We identified 115 and 124 significantly regulates genes in AC and SCC, respectively. For example, in recurrent AC we found increased expression of genes related to the wingless (FZD6, RYK, MYC) and calcium (CALM1, ATB2B1, S100A2) signalling pathways which might play a role in metastasis of tumor cells. Other differentially expressed genes were related to cell cycle (CCND1, CDK2), transcription factors (TTF1, TAF2, YY1), nuclear mRNA splicing and mRNA processing (SFRS1, HNRPL), protein-nucleus import (NUTF2, KPNB1, NUP50) and chromatin modification (HIST1H4C, SMARCC1). In SCC, we found an increased expression of CTNNB1, an important mediator in wingless signalling pathway. Among the down-regulated genes in SCC, the utmost fraction belonged to genes coding for ubiquitin mediated proteolysis (UCHL1, PSMA3, COPS6) and ribosomal proteins (RPS26, RPL7A, RPS15). Other down regulated genes were related to transcription factors (TCEA2, TAF10), nuclear mRNA splicing and mRNA processing (SNRPD2, HNRPM). In conclusion, a distinct pattern of gene expression is found during the progression from primary carcinoma to recurrent NSCLC. Our microarray-based expression profiling revealed interesting novel candidate genes and pathways that may contribute to lung cancer progression. Keywords: Lung cancer, NSCLC, gene expression, progression, Wnt signalling pathway

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Global analysis of alternative splicing regulation by insulin and wingless signalling in Drosophila cells

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