An embryonic system to assess Wnt transcriptional targets: Comparing opposing Wnt pathways and transcriptional activation and repression.. Drosophila melanogaster

During animal development, signals determine and organize a vast number of complex tissues using a very small number of signal transduction pathways. These developmental signaling pathways determine cell fates through a coordinated transcriptional response that remains poorly understood. The Wnt pathway is involved in a variety of these cellular functions, and its signals are transmitted in part through a β-catenin/TCF transcriptional complex. Here we report an in vivo Drosophila assay that we used to distinguish between activation, de-repression and repression of transcriptional responses, separating upstream and downstream pathway activation and canonical/non-canonical Wnt signals in embryos. We find a specific set of genes downstream of both β-catenin and TCF with an additional group of genes regulated by Wnt. The non-canonical Wnt4 regulates a separate cohort of genes. We correlate transcriptional changes with phenotypic outcomes of cell differentiation and embryo size, showing our model can be used to characterize developmental signaling compartmentalization in vivo. Overall design: 2 replicates per condition