Manipulation and Motion of Organelles and Single Molecules in Living Cells

“…In general, the organization of the plasma membrane is based on intricate interactions involving the cytoskeleton, membrane proteins, and lipids. During the last decade, our understanding of membrane dynamics and interactions has rapidly evolved due, in a significant fraction, to advances in single-particle localization and tracking 8, 9 . Single-particle tracking (SPT) allows the direct investigation of temporal maturation and spatial heterogeneities.…”

Section: Introductionmentioning

confidence: 99%

Ergodicity breaking on the neuronal surface emerges from random switching between diffusive states

Weron

Burnecki

Akin

et al. 2017

Sci Rep

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Stochastic motion on the surface of living cells is critical to promote molecular encounters that are necessary for multiple cellular processes. Often the complexity of the cell membranes leads to anomalous diffusion, which under certain conditions it is accompanied by non-ergodic dynamics. Here, we unravel two manifestations of ergodicity breaking in the dynamics of membrane proteins in the somatic surface of hippocampal neurons. Three different tagged molecules are studied on the surface of the soma: the voltage-gated potassium and sodium channels Kv1.4 and Nav1.6 and the glycoprotein CD4. In these three molecules ergodicity breaking is unveiled by the confidence interval of the mean square displacement and by the dynamical functional estimator. Ergodicity breaking is found to take place due to transient confinement effects since the molecules alternate between free diffusion and confined motion.

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“…( ) ~ , where α is the scaling exponent (22). For 0 < α < 1 the movement is sub-diffusive (26) and within this regime, the lower the value of α, the more elastic the environment and the closer to 1, the more viscous the environment. For pure Brownian motion α = 1, and 1 < α is a sign of super-diffusive motion.…”

Section: Micro-rheologymentioning

confidence: 99%

Physical properties and actin organization in embryonic stem cells depend on differentiation stage

Hvid

Barooji

Petitjean

et al. 2020

Preprint

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max 300 words)The cellular cytoskeleton provides the cell with mechanical rigidity and mediates mechanical interaction between cells and with the extracellular environment. The actin structure plays a key role in regulating cellular behaviors like motility, cell sorting, or cell polarity. From the earliest stages of development, in naïve stem cells, the critical mechanical role of the actin structure is becoming recognized as a vital cue for correct segregation and lineage control of cells and as a regulatory structure that controls several transcription factors. The ultrastructure of the earliest embryonic stem cells has not been investigated in living cells despite the fact that it is wellknown that cells undergo morphological shape changes during the earliest stages of development. Here, we provide 3D investigations of the actin cytoskeleton of naïve mouse embryonic stem cells (ESCs) in clusters of sizes relevant for early stage development using super resolution optical reconstruction microscopy (STORM). We quantitatively describe the morphological, cytoskeletal and mechanical changes appearing between cells in small clusters at the earliest stages of inner cell mass differentiation, as recapitulated by cells cultured under two media conditions, 2i and Serum/LIF, thus promoting the naïve and first primed state, respectively. High resolution images of living stem cells showed that the peripheral actin structure undergoes a dramatic change between the two media conditions. The actin organization changed from being predominantly oriented parallel to the cell surface in 2i medium to a more radial orientation in Serum/LIF. Finally, using an optical trapping based technique, we detected micro-rheological differences in the cell periphery between the cells cultured in these two media, with results correlating well with the observed nano-architecture of the ESCs in the two different differentiation stages. These results pave the way for linking physical properties and cytoskeletal architecture to the development from naïve stem cells to specialized cells. Statement of Significance (max 120 words)Cells receive mechanical signals and must provide mechanical feedback, therefore, physical properties are instrumental for cell-cell interactions. Mechanical signals mediated through the cell surface can significantly affect transport of signaling molecules and can influence biological processes like transcriptional regulation. To achieve a deeper insight into how the cytoskeletal structure is responsible for cell shape and material properties at the earliest stages of development, we employ super-resolution microscopy to image actin fibers in clusters of embryonic stem cells mimicking early development. By modification of the culturing conditions, we investigate how the actin cytoskeleton and micro-rheological properties of ESCs change between the naïve ground state and the stage primed towards epiblast, thus revealing a correlation between differentiation stage and cytoskeletal structure.

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Manipulation and Motion of Organelles and Single Molecules in Living Cells

Cited by 231 publications

References 246 publications

Preface: Marian Smoluchowski’s 1916 paper—a century of inspiration

Preface: Marian Smoluchowski’s 1916 paper—a century of inspiration

Ergodicity breaking on the neuronal surface emerges from random switching between diffusive states

Physical properties and actin organization in embryonic stem cells depend on differentiation stage

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