Spatiotemporal control of endocytosis during morphogenesis

• Applicant: Privatdozent Dr. Veit Riechmann
• Subject Area: Developmental Biology
• Term: from 2010 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 178920548

Changes in the length of membrane domains are central during morphogenesis. How the extent of a membrane domain is controlled during the development of epithelial tissues is unclear. By analysing the function of the Ser/Thr kinase Tao we gained insight into the mechanisms controlling membrane length. Tao mutant cells are unable to shrink their lateral membrane, which prevents the formation of the squamous epithelium in the Drosophila ovary. We have shown that Tao promotes endocytosis of the adhesion protein Fas2 from the lateral membrane, which is a prerequisite for membrane shrinking. Importantly, Tao is not a general endocytosis factor but controls morphogenesis by mediating Fas2 internalisation in a spatiotemporal controlled manner. Thus, Tao appears to be a morphogenesis specific endocytosis regulator. Analysis of Tao function is therefore an excellent starting point to elucidate the molecular mechanisms controlling timing and execution of a morphogenesis program. We combine genetic and biochemical approaches to identify regulators and effectors of Tao during the stretching process. In a genetic approach we make use of a Tao gain of function phenotype that results in epithelial ruptures due to excessive endocytosis of the zonula adherens. We perform a systematic in vivo RNAi candidate screen to identify genes that modify this phenotype. Candidates for this screen include: 1) proteins that we have identified as Tao binding partners, 2) genes that we have previously identified as morphogenesis regulators and 3) genes with a known function in endocytosis. The screen design allows to determine if identified genes act up- or downstream of Tao, and if they regulate endocytosis in an activating or inhibiting manner. Proteins that act downstream of Tao will be tested in in vitro and in vivo phosphorylation assays to identify targets of Tao kinase. In combination these assays will unravel the molecular mechanisms controlling the formation of a squamous epithelium.

• DFG Programme: Research Grants