Mesoderm cell spreading in the Drosophila gastrula: From single cell behaviours to collective movement

• Applicant: Professor Dr. Arno H.J. Müller
• Subject Area: Developmental Biology ; Cell Biology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 543398978

In the early development of most multicellular animals, cell signaling and transcriptional patterning determine the body axes and instruct the shaping of tissues through morphogenetic events. The transmission of transcriptional information into coordinated tissue movements relies upon the feedback between mechanical cues and signaling molecules, which controls the cytoskeletal and adhesive activity of the cells. This grant proposal is designed to investigate how signaling through the fibroblast growth factor (FGF) instructs the collective movements of mesoderm cells after mesoderm invagination in Drosophila gastrulation. Previous studies were only able to examine the process and the genetic requirements for the process in selected areas of the embryo. However, the cells within the Drosophila gastrula are mechanically and chemically coupled to a large extent. For example, previous studies did not address the coordination of the movements of the ectoderm with the collective movement of the mesoderm cells. We will employ a novel imaging platform, MT-SPIM (multi-view tiling single plane illumination microscopy), which supports in toto live imaging of early Drosophila embryos at high resolution and provides data for the quantitative analyses of the collective movements of mesoderm cells. We previously showed that the interaction of the mesoderm cells with the underlying ectoderm tissue is characterized by an accumulation of E-cadherin and dynamic protrusive activity at the interface of the germ layers. We propose to apply the MT-SPIM platform to investigate the interaction of the mesoderm cells with the underlying ectoderm on the cell and tissue level within the entire embryo. We will dissect the function of two closely related FGF ligands secreted by the ectoderm using functional genome editing. We will examine the regulation of E-Cadherin mediated cell adhesion and the protrusive activity at the ectoderm/mesoderm interface. Based on our evidence for the involvement of the small GTPases Cdc42 and Rac1, we plan to examine two effectors -for which preliminary evidence showed that they are involved in the process- of these GTPases, the Rac1 Effector and Actin regulator Twinstar (Drosophila Cofilin) and Activated Cdc42 Kinase (Ack)-like. The effect of genetic manipulations will be examined by applying morphometric methods to quantify the dynamic changes in cell shapes of mesoderm cells in wild type and in conditions in which the interaction of ectoderm and mesoderm is compromised. We expect that the results of this project will provide a quantitative demonstration of the requirements of the individual FGF ligands and their signaling effects within the context of cell movements and cell shape landscapes that are associated with it.

• DFG Programme: Research Grants