The Molecular Architecture of Adherens Junctions During the Dorsal Closure by Cryo-Electron Tomography and Volume Electron Microscopy

• Applicant: Professor Dr. Achilleas Frangakis
• Subject Area: Cell Biology ; Biophysics
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 571751810

In this proposal, we aim to study the overall organization and the molecular architecture of adherence junctions (AJs) during the dorsal closure using volume electron microscopy and cryo-electron microscopy. We have chosen the dorsal closure (DC) in Drosophila melanogaster, because it is a supreme system in which the spatial dimension along the dorsal closure can be equated to the time dimension, thus providing a unique four-dimensional (4D) system that can be analyzed by the otherwise static techniques scanning and transmission electron microscopy. It thus allows to study the built-up and turnover of AJs in 4D. Additional reasons for selecting this system include the following: (i) Cellular interfaces, such as AJs, form robustly to withstand strong mechanical forces. In contrast, they do not develop properly in cell cultures, where they have been studied to date, resulting in insufficient quality to investigate these essential tissue connections. During the DC long and stable AJs form, which can be nicely studied by cryo-electron tomography, leading to a sub-tomogram average with a resolution better than 10 Å. (ii) DC is a key process in embryonic development, during which two lateral epithelial sheets seal the embryo. Technically, this process enables 4D electron microscopy to observe the interaction between the cytoskeleton and the AJs —critical for understanding developmental events. (iii) The cryo-focused ion beam milling technology allows for the first time the study of such an event. A significant amount of preliminary data (from our group and others) is available in the fields of imaging (light and electron microscopy), biophysics, force measurements, and genetics, which will guide and support the success of the project by advancing our insights in both developmental and structural biology.

• DFG Programme: Research Grants