Regulation of Hippo signaling and planar cell polarity via distinct regions of the Fat intracellular domain

The large Drosophila protocadherin Fat (Ft) is a receptor for signal transduction pathways that control growth (Hippo signaling), planar cell polarity (PCP), metabolism and the proximodistal patterning of appendages. The intracellular domain (ICD) of Ft is crucial in implementing its biological functions. Six regions of high conservation (named A-F) within the ICD have been identified, as well as distinct regions mediating Hippo pathway activity that have been functionally characterized via overexpression assays. Here, we make targeted deletions of these highly conserved residues and the putative Hippo- and PCP-regulating domains of endogenous Ft using CRISPR/Cas9. Through transcriptomic, developmental, and phenotypic analyses, we show that different regions of Ft contribute uniquely to chromatin dynamics, tissue morphogenesis, PCP and metabolic regulation. We also demonstrate that different regions of Ft regulate Yorkie activity in opposite directions, finely tuning growth and tissue development. Strikingly, conserved regions D and F are key regulators of Ft's functions- exhibiting opposing effects on wing morphology and Hippo pathway modulation- and conserved region D is the main regulator of PCP. Overall design: RNA-seq profiling of imaginal wing discs from third-instar Drosophila larvae. This dataset is used to compare wild-type, fat nulls, conserved and functional domain mutants