Shachar Sherman 1 David Kirchenbuechler 2 Dikla Nachmias 1 Adi Tamir 1 Stephan Werner 3 Michael Elbaum 2 Natalie Elia 1
1Department of Life Sciences and NIBN, Ben-Gurion University of the Negev, Beer-Sheva, Israel
2Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel
3Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Wilhelm-Conrad-Röntgen Campus, Berlin, Germany

Mammalian cytokinetic abscission is mediated by the ESCRT membrane fission machinery. While much has been clarified on the topology and kinetics of abscission through high-resolution microscopy, key questions regarding its mechanism remain open. Here we apply cryogenic Soft-X-ray tomography to elucidate new ultrastructural details in the intercellular membrane bridge connecting cells undergoing abscission. In particular, we resolve defined ring-like structures inside the midbody dark zone that have been inaccessible to EM, and identify membrane extrusions at the abscission sites. In cells at late stages of abscission we resolve a complex array of helical spirals, extending the structural information obtained by EM. Our results highlight the advantages of Soft-X-ray tomography and emphasize the importance of using complementary approaches for characterizing cellular structures. Notably, by providing new structural data from intact cells we present a realistic view on the topology of abscission and suggest new mechanistic models for ESCRT mediated abscission.

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