Abstract: FR-PO0755
Slit Diaphragms in Drosophila Exhibit Bilayered, Fishnet Architecture
Session Information
- Glomerular Diseases: Cell Homeostasis and Novel Injury Mechanisms
November 07, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology
Authors
- Moser, Deborah, Goethe-Universitat Frankfurt am Main Buchmann Institute for Molecular Life Sciences, Frankfurt, HE, Germany
- Lang, Konrad, Albert-Ludwigs-Universitat Freiburg Medizinische Fakultat, Freiburg, BW, Germany
- Birtasu, Alexandra N., Goethe-Universitat Frankfurt am Main Buchmann Institute for Molecular Life Sciences, Frankfurt, HE, Germany
- Scheffer, Margot P, Goethe-Universitat Frankfurt am Main Buchmann Institute for Molecular Life Sciences, Frankfurt, HE, Germany
- Helmstädter, Martin, Albert-Ludwigs-Universitat Freiburg Medizinische Fakultat, Freiburg, BW, Germany
- Hermle, Tobias F., Albert-Ludwigs-Universitat Freiburg Medizinische Fakultat, Freiburg, BW, Germany
- Frangakis, Achilleas, Goethe-Universitat Frankfurt am Main Buchmann Institute for Molecular Life Sciences, Frankfurt, HE, Germany
Background
The kidney relies on the glomerulus to filter large volumes of blood plasma. The slit diaphragm, a critical component of the glomerulus, is formed between podocytes by the immunoglobulin superfamily proteins nephrin and Neph1. The native molecular architecture of the slit diaphragm has remained elusive for decades. Drosophila nephrocytes are an invertebrate podocyte model which also presents a slit diaphragm, formed by Sns, the Drosophila ortholog of nephrin, and Kirre, the Drosophila ortholog of Neph1. Drosophila provides a genetically amenable system for conducting structural studies, which we explored to unveil the molecular architecture of the slit diaphragm.
Methods
We performed STED microscopy on wild-type Drosophila nephrocytes, reaching an unprecedented resolution at the slit diaphragm. Then we used cryo-electron tomography on focused ion beam-milled nephrocytes together with subtomogram averaging of slit diaphragm segments to assess its three-dimensional structure. To validate our findings on the slit diaphragm architecture, we performed the same set of experiments after silencing of sns and Rab5, an endosomal regulator, and studied the effects on the silt diaphragm.
Results
Cryo-electron tomography revealed that the slit diaphragm has a fishnet like architecture which is highly periodic and bi-layered. Mapping of Sns and Kirre into this configuration led to only one biologically plausible model.
Silencing of sns disrupts the fishnet pattern, linking the architecture directly to Drosophila nephrin. After Rab5 silencing, which causes Sns mistrafficking and ectopic formation of the slit diaphragm, the fishnet pattern appears ectopically as well.
Conclusion
The fishnet architecture of the slit diaphragm seems plausibly linked to the functional requirements of the SD, providing high mechanical stability while enabling size-selective permeability. Our findings align with observations in other organisms, which indicates that the architecture of the slit diaphragm is evolutionarily conserved. This highlights the value of the nephrocyte as a podocyte model and underscores the functional significance of the fishnet architecture.
Funding
- Government Support – Non-U.S.