Interactions between cytoskeletal filaments in cells

by Anna Friederike Blob
Doctoral thesis
Date of Examination:2024-02-12
Date of issue:2024-10-04
Advisor:Prof. Dr. Sarah Köster
Referee:Prof. Dr. Sarah Köster
Referee:Prof. Dr. Andreas Janshoff
Referee:Prof. Dr. Stefan Klumpp
Referee:Prof. Dr. Alexander Egner
Referee:Dr. Peter Lenart
Referee:Prof. Dr. Axel Munk
Persistent Address: http://dx.doi.org/10.53846/goediss-10774

 

 

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Abstract

English

Essential functions of eukaryotic cells such as cell division, force generation and the ability to mechanically adapt to the outer environment depend on the cytoskeleton, which is an intricate network containing three different biopolymers: microtubules, actin filaments and intermediate filaments. Each of these filament types has its own distinct mechanical properties, function and network architecture within a cell. Microtubules, for instance, are important for intracellular transport, as cargo can be carried along them, and despite their intrinsic stiffness they exhibit characteristic bending due to nonthermal forces in the cell. Various interactions between cytoskeletal filaments have been found, such as the guidance of microtubules by vimentin intermediate filaments and actin filaments. Yet, the complexity and the natural variability of cells leaves many aspects of cytoskeletal interactions incompletely understood. In this thesis, we systematically study the influence of vimentin intermediate filaments and actin filaments on microtubules in mouse fibroblasts. To mitigate the effect of natural cell-to-cell variability we employ micropatterning, allowing us to average over many cells of exactly the same shape. With an automated bias-free analysis of microscopy images we investigate the alignment and orientation of microtubules as well as their local curvature. We find a robust average radial orientation of microtubules in circular cells. The local curvature is independent of vimentin intermediate filaments and actin filaments which challenges the notion that a cytoskeletal matrix embedding of microtubules is necessary for the creation and maintenance of high bending. This thesis highlights the importance of a systematic analysis under standardized cell conditions and demonstrates an independence of microtubules on both a global network level and the level of individual filament shapes.
Keywords: cytoskeleton; microtubules; mouse fibroblast; single-cell patterning; fluorescence microscopy; image analysis