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Non-invasive perturbations of intracellular flow reveal physical principles of cell organization


Recent advances in cell biology enable precise molecular perturbations. The spatiotemporal organization of cells and organisms, however, also depends on physical processes such as diffusion or cytoplasmic flows, and strategies to perturb physical transport inside cells are not yet available. Here, we demonstrate focused-light-induced cytoplasmic streaming (FLUCS). FLUCS is local, directional, dynamic, probe-free, physiological, and is even applicable through rigid egg shells or cell walls. We explain FLUCS via time-dependent modelling of thermoviscous flows. Using FLUCS, we demonstrate that cytoplasmic flows drive partitioning-defective protein (PAR) polarization in Caenorhabditis elegans zygotes, and that cortical flows are sufficient to transport PAR domains and invert PAR polarity. In addition, we find that asymmetric cell division is a binary decision based on gradually varying PAR polarization states. Furthermore, the use of FLUCS for active microrheology revealed a metabolically induced fluid-to-solid transition of the yeast cytoplasm. Our findings establish how a wide range of transport-dependent models of cellular organization become testable by FLUCS.

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The authors acknowledge support from the Max Planck Society, a DFG-financed DIPP fellowship for M.Mi., infrastructural support by the Hyman lab, and technical support from MPI-CBG light-microscopy and scientific computing facilities. The authors thank F. Decker and J. Brugués for egg extracts, H. Petzold for cell culture support, D.J. Dickinson and B. Goldstein for sharing transgenic C. elegans strains, and M. Zerial, D. Braun, P. Tomancak, F. Jülicher, A. Hyman, C. Hoege, J. Saenz, K. Subramanian, N. Maghelli and E. Knust for discussions and comments.

Author information

M.Mi., A.W.F. and M.Kr. designed the experimental set-up. M.Mi. conducted experiments. M.Mi. and M.Kr. analysed data. M.Mi. wrote the initial draft. P.G. assisted with C. elegans experiments and provided worm lines. M.N. and A.V. performed finite-element simulations. C.I. and M.Mu. helped with yeast measurements. M.Ka. assisted with gel chemistry. M.Mi., P.G., A.W.F., S.W.G. and M.Kr. conceived and interpreted C. elegans experiments, M.Mi., S.A. and M.Kr. conceived and interpreted yeast experiments. All authors contributed to a critical discussion of the data and participated in writing the manuscript, which M.Mi. and M.Kr. finalized. M.Kr. coordinated the research.

Competing interests

The authors declare that parts of the published work led to the application for a European patent.

Correspondence to Moritz Kreysing.

Supplementary information

Supplementary Information

Supplementary Figures 1–6 and Supplementary Video legends.

Life Sciences Reporting Summary


Supplementary Video 1

Light-induced thermoviscous flows in water and honey.

Supplementary Video 2

Directional transport perturbation in Xenopus laevis egg extract.

Supplementary Video 3

Dynamic and localized induction of flows inside C. elegans embryos.

Supplementary Video 4

Quantification of sub-millisecond temperature dynamics.

Supplementary Video 5

Viability of C. elegans embryos in response to dynamic laser-induced heating.

Supplementary Video 6

Flow-driven PAR-2 loading enhancement on the membrane in polarized C. elegans embryos.

Supplementary Video 7

Flow-driven dynamic translocation of the PAR-2 domain in a polarized C. elegans embryo.

Supplementary Video 8

Induced cytoplasmic flows drive flows of the actomyosin cortex.

Supplementary Video 9

PAR polarization of the C. elegans embryo is a bi-stable process.

Supplementary Video 10

Micro-rheological flow stimulus.

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Further reading

Fig. 1: FLUCS inside C. elegans embryos.
Fig. 2: Physical modelling of induced cytoplasmic flows.
Fig. 3: Cytoplasmic flows enhance PAR-2 loading onto the membrane.
Fig. 4: FLUCS demonstrates sufficiency of cortical flows to translocate PAR domains.
Fig. 5: PAR rotational stability and threshold-dependent inversion of asymmetric cell division.
Fig. 6: Intracellular flow perturbations reveal a fluid-to-solid transition in the cytoplasm of energy-depleted yeast cells.