@article{10290,
  abstract     = {A precise quantitative description of the ultrastructural characteristics underlying biological mechanisms is often key to their understanding. This is particularly true for dynamic extra- and intracellular filamentous assemblies, playing a role in cell motility, cell integrity, cytokinesis, tissue formation and maintenance. For example, genetic manipulation or modulation of actin regulatory proteins frequently manifests in changes of the morphology, dynamics, and ultrastructural architecture of actin filament-rich cell peripheral structures, such as lamellipodia or filopodia. However, the observed ultrastructural effects often remain subtle and require sufficiently large datasets for appropriate quantitative analysis. The acquisition of such large datasets has been enabled by recent advances in high-throughput cryo-electron tomography (cryo-ET) methods. This also necessitates the development of complementary approaches to maximize the extraction of relevant biological information. We have developed a computational toolbox for the semi-automatic quantification of segmented and vectorized filamentous networks from pre-processed cryo-electron tomograms, facilitating the analysis and cross-comparison of multiple experimental conditions. GUI-based components simplify the processing of data and allow users to obtain a large number of ultrastructural parameters describing filamentous assemblies. We demonstrate the feasibility of this workflow by analyzing cryo-ET data of untreated and chemically perturbed branched actin filament networks and that of parallel actin filament arrays. In principle, the computational toolbox presented here is applicable for data analysis comprising any type of filaments in regular (i.e. parallel) or random arrangement. We show that it can ease the identification of key differences between experimental groups and facilitate the in-depth analysis of ultrastructural data in a time-efficient manner.},
  author       = {Dimchev, Georgi A and Amiri, Behnam and Fäßler, Florian and Falcke, Martin and Schur, Florian KM},
  issn         = {1047-8477},
  journal      = {Journal of Structural Biology},
  keywords     = {Structural Biology},
  number       = {4},
  publisher    = {Elsevier },
  title        = {{Computational toolbox for ultrastructural quantitative analysis of filament networks in cryo-ET data}},
  doi          = {10.1016/j.jsb.2021.107808},
  volume       = {213},
  year         = {2021},
}

@article{8434,
  abstract     = {Efficient migration on adhesive surfaces involves the protrusion of lamellipodial actin networks and their subsequent stabilization by nascent adhesions. The actin-binding protein lamellipodin (Lpd) is thought to play a critical role in lamellipodium protrusion, by delivering Ena/VASP proteins onto the growing plus ends of actin filaments and by interacting with the WAVE regulatory complex, an activator of the Arp2/3 complex, at the leading edge. Using B16-F1 melanoma cell lines, we demonstrate that genetic ablation of Lpd compromises protrusion efficiency and coincident cell migration without altering essential parameters of lamellipodia, including their maximal rate of forward advancement and actin polymerization. We also confirmed lamellipodia and migration phenotypes with CRISPR/Cas9-mediated Lpd knockout Rat2 fibroblasts, excluding cell type-specific effects. Moreover, computer-aided analysis of cell-edge morphodynamics on B16-F1 cell lamellipodia revealed that loss of Lpd correlates with reduced temporal protrusion maintenance as a prerequisite of nascent adhesion formation. We conclude that Lpd optimizes protrusion and nascent adhesion formation by counteracting frequent, chaotic retraction and membrane ruffling.This article has an associated First Person interview with the first author of the paper. },
  author       = {Dimchev, Georgi A and Amiri, Behnam and Humphries, Ashley C. and Schaks, Matthias and Dimchev, Vanessa and Stradal, Theresia E. B. and Faix, Jan and Krause, Matthias and Way, Michael and Falcke, Martin and Rottner, Klemens},
  issn         = {1477-9137},
  journal      = {Journal of Cell Science},
  keywords     = {Cell Biology},
  number       = {7},
  publisher    = {The Company of Biologists},
  title        = {{Lamellipodin tunes cell migration by stabilizing protrusions and promoting adhesion formation}},
  doi          = {10.1242/jcs.239020},
  volume       = {133},
  year         = {2020},
}

@article{8971,
  abstract     = {The actin-related protein (Arp)2/3 complex nucleates branched actin filament networks pivotal for cell migration, endocytosis and pathogen infection. Its activation is tightly regulated and involves complex structural rearrangements and actin filament binding, which are yet to be understood. Here, we report a 9.0 Å resolution structure of the actin filament Arp2/3 complex branch junction in cells using cryo-electron tomography and subtomogram averaging. This allows us to generate an accurate model of the active Arp2/3 complex in the branch junction and its interaction with actin filaments. Notably, our model reveals a previously undescribed set of interactions of the Arp2/3 complex with the mother filament, significantly different to the previous branch junction model. Our structure also indicates a central role for the ArpC3 subunit in stabilizing the active conformation.},
  author       = {Fäßler, Florian and Dimchev, Georgi A and Hodirnau, Victor-Valentin and Wan, William and Schur, Florian KM},
  issn         = {2041-1723},
  journal      = {Nature Communications},
  keywords     = {General Biochemistry, Genetics and Molecular Biology, General Physics and Astronomy, General Chemistry},
  publisher    = {Springer Nature},
  title        = {{Cryo-electron tomography structure of Arp2/3 complex in cells reveals new insights into the branch junction}},
  doi          = {10.1038/s41467-020-20286-x},
  volume       = {11},
  year         = {2020},
}