Global transcriptional Analysis of Yap/Yki Orthologs in Drosophila melanogaster by RNA Seq

Throughout Metazoa, developmental processes are controlled by a surprisingly limited number of conserved signaling pathways. Precisely how these signaling cassettes were assembled in early animal evolution remains poorly understood, as do the molecular transitions that potentiated the acquisition of their myriad developmental functions. Here we analyze the molecular evolution of the proto-oncogene YAP/Yorkie, a key effector of the Hippo signaling pathway that controls organ size in both Drosophila and mammals. Based on heterologous functional analysis of evolutionarily distant Yap/Yorkie orthologs, we demonstrate that a structurally distinct interaction interface between Yap/Yorkie and its partner TEAD/Scalloped became fixed in the eumetazoan common ancestor. We then combine transcriptional profiling of tissues expressing phylogenetically diverse forms of Yap/Yorkie with ChIP-seq validation in order to identify a common downstream gene expression program underlying the control of tissue growth in Drosophila. Intriguingly, a subset of the newly-identified Yorkie target genes are also induced by Yap in mammalian tissues, thus revealing a conserved Yap-dependent gene expression signature likely to mediate organ size control throughout bilaterian animals. Combined, these experiments provide new mechanistic insights while revealing the ancient evolutionary history of Hippo signaling. We sought to define the downstream target genes of selected Yap variants by performing RNA sequencing analysis (RNA-seq) on total RNA isolated from GMR-Gal4>Yap eye discs. Overall design: Transcriptional profiles were generated in triplicate from eye imaginal disks with either endogenous Yki, or GMR-Gal4 over-expressed Yki, Trichoplax Yap, Monosiga Yap, or Monisiga Yap+TEAD domain, using deep sequencing via Illumina Hi Seq.

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Ikmi A, Gaertner B, Seidel C, Srivastava M, Zeitlinger J, Gibson MC