Unknown,Transcriptomics,Genomics,Proteomics

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An ectopic network of transcription factors regulated by Hippo signaling drives growth and invasion of a malignant tumor model [larval imaginal discs (eye, wing and leg)]

ABSTRACT: Cancer cells have abnormal gene expression patterns, however, the transcription factors and the architecture of the regulatory network that drive cancer specific gene expression profiles is often not known. Here we studied a model of Ras-driven invasive tumorigenesis in Drosophila larval epithelial tissues and combined in vivo genetic analyses with high-throughput sequencing and computational modeling to decipher the regulatory logic of tumor cells. Surprisingly, we discovered that tumor specific gene expression is driven by a highly interconnected network composed of few transcription factors. These are: Stat, Mef2, the AP-4 homolog Cropped, the nuclear receptor Ftz-f1, the bHLH factors Myc and Taiman, and the AP-1 transcription factors Kayak, ATF-3, Pdp1, and dCEBPG. Many of these transcription factors are ectopically expressed and/or hyperactivated in human tumors. The members of this tumor master regulatory network are predicted to directly regulate the majority of the tumor specific gene expression profile. Similar to networks of master regulators that control organ development and cellular differentiation, there is a predicted high degree of co-regulation of target genes, and these network members are required in multiple eptihelia for tumor growth and invasiveness. We further found that Yki/Sd and bZIP/AP-1 factors, the downstream transcription factors of the Hippo and JNK pathways, initiate cellular reprogramming by activating several transcription factors of this network. Thus, modeling regulatory networks identified an ectopic yet highly ordered network of master regulators that control cancer cell specific gene expression. RNA-seq gene expression profiling across Drosophila 3rd instar larval imaginal discs (eye-antenna, wing and leg) in a hh driven tumor model, perturbations and controls.

ORGANISM(S): Drosophila melanogaster

SUBMITTER: Stein Aerts

PROVIDER: E-GEOD-81272 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Genomic enhancers regulate spatio-temporal gene expression by recruiting specific combinations of transcription factors (TFs). When TFs are bound to active regulatory regions, they displace canonical nucleosomes, making these regions biochemically detectable as nucleosome-depleted regions or accessible/open chromatin. Here we ask whether open chromatin profiling can be used to identify the entire repertoire of active promoters and enhancers underlying tissue-specific gene expression during normal development and oncogenesis in vivo. To this end, we first compare two different approaches to detect open chromatin in vivo using the Drosophila eye primordium as a model system: FAIRE-seq, based on physical separation of open versus closed chromatin; and ATAC-seq, based on preferential integration of a transposon into open chromatin. We find that both methods reproducibly capture the tissue-specific chromatin activity of regulatory regions, including promoters, enhancers, and insulators. Using both techniques, we screened for regulatory regions that become ectopically active during Ras-dependent oncogenesis, and identified 3778 regions that become (over-)activated during tumor development. Next, we applied motif discovery to search for candidate transcription factors that could bind these regions and identified AP-1 and Stat92E as key regulators. We validated the importance of Stat92E in the development of the tumors by introducing a loss of function Stat92E mutant, which was sufficient to rescue the tumor phenotype. Additionally we tested if the predicted Stat92E responsive regulatory regions are genuine, using ectopic induction of JAK/STAT signaling in developing eye discs, and observed that similar chromatin changes indeed occurred. Finally, we determine that these are functionally significant regulatory changes, as nearby target genes are up- or down-regulated. In conclusion, we show that FAIRE-seq and ATAC-seq based open chromatin profiling, combined with motif discovery, is a straightforward approach to identify functional genomic regulatory regions, master regulators, and gene regulatory networks controlling complex in vivo processes. FAIRE-Seq in Drosophila wild type eye-antennal imaginal discs (2 wt strains); ATAC-Seq in Drosophila wild type eye-antennal imaginal discs (3 wt strains) ; FAIRE-Seq in Drosophila Ras/Scrib induced eye disc tumors (1 early and 1 late); ATAC-Seq in Drosophila Ras/Scrib induced eye disc tumors (1 early and 1 late); ATAC-Seq in Drosophila eye discs with Unpaired over-expression (2 biological replicates); CTCF ChIP-seq in Drosophila eye discs; ChIP-seq input in Drosophila eye discs

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An ectopic network of transcription factors regulated by Hippo signaling drives growth and invasion of a malignant tumor model [larval imaginal discs (eye, wing and leg)]

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