Genome-wide analysis of Yki and Sd localization in imaginal disks of Drosophila eye by ChIP Seq. Drosophila melanogaster

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 determine Yki and Sd target genes in Drosophila by immunoprecipitation of Yki, sd and RNA polymerase II. Overall design: Chromatin immunoprecipitation of Yki, sd, and RNA polymerase II from eye disks was performed.