Department Biological Physics
Frank Jülicher

for the Physics of Complex Systems
Nöthnitzer Straße 38
01187 Dresden

Tel. +49 351 871-1202
Fax. +49 351 871-1299
Curriculum Vitae
List of Publications
Research Interests

Theory of Biological Systems and Processes

The main focus of our research are theoretical approaches to understand dynamic processes in cells and tissues. Work on active cellular processes includes the study of cellular oscillations, cellular signaling and the cytoskeletal dynamics during cell division and cell motility. We furthermore study the biophysical basis of hearing. Finally, we investigate the biophysical properties and dynamics of tissues and epithelia. Based on the properties of individual cells and of cellular signaling systems, we are interested in the dynamics of developmental processes, for example wing development in the fruit fly.

Research topics include:

Active cellular processes
Cellular oscillations
Swimming of microorganisms
Cell locomotion

Physics of the cytoskeleton and of motor proteins
Active gels and fluids
Collective behaviors of motor proteins
Self-organization phenomena in the cytoskeleton

Physics of Cell Division

Tissues and developmental processes
Cellular packings in epithelia
Cellular rearrangements during growth and development
Morphogen signaling and morphogen gradient formation

Biophysics of hearing
Active mechanics of hair cells
Cochlear waves
Signal amplification by nonlinear oscillators

Research Highlights
TissueMiner: a Multiscale Analysis Toolkit to Quantify how Cellular Processes Create Tissue dynamics
R. Etournay, M. Merkel, M. Popovic, H. Brandl, N. Dye, B. Aigouy, G. Salbreux, S. Eaton and F. Jülicher
eLife 2016;10.7554/eLife.14334 (2016)
PDF (12,5 MB)]
Dynamic Curvature Regulation Accounts for the Symmetric and Asymmetric Beats of Chlamydomonas Flagella

The periodic bending motion of cilia and flagella is thought to arise from mechanical feedback: dynein motors generate sliding forces that bend the flagellum, and bending leads to deformations and stresses, which feed back and regulate the motors. Alternative feedback mechanisms have been proposed: regulation by the sliding forces, regulation by the curvature of the flagellum, and regulation by the normal forces that deform the cross-section of the flagellum. Here, we combined theoretical and experimental approaches to show that the curvature control mechanism accords best with the bending waveforms of Chlamydomonas flagella. Our work suggests that the motors respond to the time derivative of curvature, rather than curvature itself, hinting at an adaptation mechanism controlling the flagellar beat.
We study the spatiotemporal dynamics of beating flagella of the algea Chlamydomonas. We use a general theory of flagellar beating that permits for different types of motor regulation feedbacks. By comparing different scenarios to the Analyzing observed the movements using

P. Sartori, V. F. Geyer, A. Scholich, F. Jülicher and J. Howard
eLife 2016;10.7554/eLife.13258 (2016)
PDF (5,9 MB)]
Determining Physical Properties of the Cell Cortex

Using a continuum description of active visco-elastic gels, we study the response of a contractile layer of an actomyosin gel to mechanical perturbations. This work is motivated by laser ablation experiments in cell biophysics. Our work shows that from the observation of the flow response to a linear later cut, key biophysical parameters of the contractile layer can be inferred.

A. Saha, M. Nishikawa, M. Behrndt, C.-P. Heisenberg, F. Jülicher and S. W. Grill
Biophys J. 110, 1421 (2016)
[PDF (2 MB)]
Activity Induces Traveling Waves, Vortices and Spatiotemporal Chaos in a Model Actomyosin Layer

Using a numerical approach, we investigate the spatiotemporal dynamics of an active polar gel in two dimensions. We find that when increasing the magnitude of active stresses, the system first undergoes a flow instability to stationary flow patterns. Subsequently, traveling wave solutions appear. Finally, for further increased active stress the system undergoes a transition to spatiotemporal chaos.

R. Ramaswamy and F. Jülicher
Scientific Reports 6, 20838 (2016)
[PDF (1,5 MB)]
Persistence, Period and Precision of Autonomous Cellular Oscillators from
the Zebrafish Segmentation Clock

We study the dynamics of gene expression of cells from the zebrafish segmentation clock in vitro. We show that single cells can behave as autonomous noisy cellular oscillations. The observed variability of cell behaviors can be captured by a generic oscillator model with correlated noise. We find that single cells have longer periods and lower precision than the tissue, highlighting the role of collective processes in the segmentation clock.

A. B. Webb, I. M. Lengyel, D. J. Jörg, G. Valentin, F. Jülicher, L. G Morelli and A. C. Oates
eLife 2016;10.7554/eLife.08438 (2016)
[PDF (2,6 MB)]
Interface Contractility between Differently Fated Cells Drives Cell Elimination
and Cyst Formation

We use a novel generalized vertex model to analyze epithelial morphogenesis in three dimensions. We show that increased actomyosin contractility at the interface between normal and aberrantly specified cells drives the formation of cysts while single cells are eliminated from the tissue.

C. Bielmeier, S. Alt, V. Weichselberger, M. La Fortezza, H. Harz, F. Jülicher,
G. Salbreux, A. Classen
Current Biology 26, 1 (2016)
[PDF (31,5 MB)]
Decision Making in the Arrow of Time

Irreversibility is a hallmark of nonequilibrium processes. It implies that time reversal invariance of microscopic equations of motion is broken at meso and macro scales. Here we show that the degree of irreversibility of a physical process can be quantified by the time it takes an observer to decide whether a movie of the process runs forward or in reverse. We derive an exact relation between the average entropy production rate and the optimal decision time and we introduce a fluctuation theorem for the decision time distribution.

E. Roldán, I. Neri, M. Dörpinghaus, H. Meyr and F. Jülicher
Phys. Rev. Lett. 115, 250602 (2015)
[PDF (426 kB)]
Polarized Endosome Dynamics by Spindle Asymmetry During Asymmetric Cell Division

During asymmetric cell division, the molecular components of the dividing cell are distributed unequally to the two daughter cells. Here, we study the asymmetric distribution of signaling endosomes to the two daughter cells which plays an important role for cell fate determination. We show that the unequal distribution of endosomes results from an asymmetry of the microtubule distribution at the central spindle. Using a simple stochastic model, we reveal a physical mechanism by which a weak asymmetry of the density of antiparallel microtubules is amplified by kinesin mediated endosome motility to generate a strong asymmetry of endosome targeting to the daughter cells. Out model can quantitatively account for the stochastic endosome trajectories observed during division.

E. Derivery, C. Seum, A. Daeden, S. Loubéry, L. Holtzer, F. Jülicher and M. Gonzalez-Gaitan
Nature 528, 280 (2015)
[PDF (17,9 MB)]
A Local Difference in Hedgehog Signal Transduction Increases Mechanical Cell Bond Tension
and Biases Cell Intercalations along the Drosophila Anteroposterior Compartment Boundary

We study the properties of tissue boundaries in the context of cellular signaling. Using a quantification of boundary roughness in different signaling conditions, we show that differences in Hedgehog signal transduction between neighboring cells are key to control cell bond tension. An increased cell bond tension subsequently provides smooth and stable tissue interfaces.

K. Rudolf, D. Umetsu, M. Aliee, L. Sui, F. Jülicher and C. Dahmann
Development 142, 3845 (2015)
[PDF (5 MB)]
Continuum Theory of Gene Expression Waves during Vertebrate Segmentation

The segmentation of the vertebrate body plan during embryonic development is a rhythmic and sequential process governed by genetic oscillations of cells that give rise to collective wave patterns. We present a continuum theory of genetic waves and discuss wave phenomena that can be observed in these nonlinear wave patterns: a Doppler effekt and a dynamic wavelength effect.

D. J. Jörg, L. G. Morelli, D. Soroldoni, A. C. Oates and F. Jülicher
New J. Phys. 17, 093042 (2015)
[PDF (2 MB)]
Suppression of Ostwald Ripening in Active Emulsions

We study the dynamics of fluid droplets that turn over by chemical processes. Such active droplets exhibit unusual properties both in the simple case of first-order reactions and for autocatalytic droplets. Active droplets can have stable sizes and several droplets of equal size can stably coexist. This suppression of Ostwald ripening can be understood as a consequence of chemical reactions.

D. Zwicker, A. A. Hyman and F. Jülicher
Phys. Rev. E 92, 012317 (2015)
[PDF (918 kB)]
Interplay of Cell Dynamics and Epithelial Tension during Morphogenesis of the Drosophila Pupal Wing

We combine experiment and theory to study tissue dynamics and remodeling in the developing fly wing. We quantify the contributions of different celular processes to tissue deformations. Using this information we develop a theory of tissue mechanics which reveals key principles underlying tissue deformation. We find that during pupal development, the fly wing is shaped in an active process that is guided by mechanical boundary conditions. We can explain the role of the extracellular matrix protein dumpy in this process and reveal the mechanism by which dumpy mutants exhibit misformed wing shapes.

R. Etournay, M. Popovic, M. Merkel, A. Nandi, C. Blasse, B. Aigouy, H. Brandl, G. Myers, G. Salbreux, F. Jülicher and S. Eaton
eLife 2015;10.7554/eLife.07090 (2015)
PDF (14 MB)]
Scaling and Regeneration of Self-Organized Patterns

Biological pattern formation such as for example the development and regeneration of an organism is often scalable with organism size. Here, we introduce a generalization of Turing patterns that is self-organized and self-scaling. A feedback loop regulates the reaction rates of a Turing system, thereby adjusting pattern length scales proportional to system size. Our model captures key features of body plan regeneration in flatworms as observed in experiments.

S. Werner, T. Stückemann, M. Beirán Amigo, J. C. Rink, F. Jülicher and B. M. Friedrich
Phys. Rev. Lett. 114, 138101 (2015)
PDF (295 kB)]
Highlights 2014
Highlights 2013
Highlights 2012
Highlights 2011
Highlights 2010
Highlights 2009
Highlights 2008
Highlights 2007
Last updated: May 30, 2016