Forces in inhomogeneous open active-particle systems

Razin, Nitzan; Voituriez, Raphaël; Elgeti, Jens; Gov, Nir S.

doi:10.1103/physreve.96.052409

Cited by 16 publications

(20 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Active bursts generated by Myosin-V are fundamental for nuclear positioning in mouse oocytes. In fact, active diffusion is here thought to create pressure gradient and directional forces strong enough to induce nuclear displacements [31,160,161]. As in the earlier studies discussed above, the FDT is sharply violated at low frequencies, while it is recovered at large ones [162].…”

Section: Fluctuations Of Probe Particles Inside Living Cellsmentioning

confidence: 87%

Broken detailed balance and non-equilibrium dynamics in living systems: a review

et al. 2018

View full text Add to dashboard Cite

Living systems operate far from thermodynamic equilibrium. Enzymatic activity can induce broken detailed balance at the molecular scale. This molecular scale breaking of detailed balance is crucial to achieve biological functions such as high-fidelity transcription and translation, sensing, adaptation, biochemical patterning, and force generation. While biological systems such as motor enzymes violate detailed balance at the molecular scale, it remains unclear how non-equilibrium dynamics manifests at the mesoscale in systems that are driven through the collective activity of many motors. Indeed, in several cellular systems the presence of non-equilibrium dynamics is not always evident at large scales. For example, in the cytoskeleton or in chromosomes one can observe stationary stochastic processes that appear at first glance thermally driven. This raises the question how non-equilibrium fluctuations can be discerned from thermal noise. We discuss approaches that have recently been developed to address this question, including methods based on measuring the extent to which the system violates the fluctuation-dissipation theorem. We also review applications of this approach to reconstituted cytoskeletal networks, the cytoplasm of living cells, and cell membranes. Furthermore, we discuss a more recent approach to detect actively driven dynamics, which is based on inferring broken detailed balance. This constitutes a non-invasive method that uses time-lapse microscopy data, and can be applied to a broad range of systems in cells and tissue. We discuss the ideas underlying this method and its application to several examples including flagella, primary cilia, and cytoskeletal networks. Finally, we briefly discuss recent developments in stochastic thermodynamics and non-equilibrium statistical mechanics, which offer new perspectives to understand the physics of living systems.

show abstract

Section: Fluctuations Of Probe Particles Inside Living Cellsmentioning

confidence: 87%

Broken detailed balance and non-equilibrium dynamics in living systems: a review

et al. 2018

View full text Add to dashboard Cite

show abstract

“…We showed that the activity of these actin-positive vesicles decreases from the cortex to the oocyte center as quantified by their squared velocity. On the basis of a simple model describing the pool of actin-positive vesicles as an ideal suspension of self-propelled particles, we proposed that this gradient of activity of actin vesicles, which move by active diffusion (Almonacid et al, 2015), generates an effective pressure gradient (Razin et al, 2017b,a; Solon et al, 2015) and thus a propulsion force. It would therefore be the driver of nuclear motion toward the oocyte center (Almonacid et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…In previous work, we used analytical modeling to show that, in principle, a gradient of active particles can center objects (Razin et al, 2017b,a). Here, we used 3D numerical simulations to allow direct comparison between the model and the experimental data.…”

Section: Introductionmentioning

confidence: 99%

Active diffusion in oocytes nonspecifically centers large objects during prophase I and meiosis I

Colin

Letort

Razin

et al. 2020

Journal of Cell Biology

Self Cite

View full text Add to dashboard Cite

Nucleus centering in mouse oocytes results from a gradient of actin-positive vesicle activity and is essential for developmental success. Here, we analyze 3D model simulations to demonstrate how a gradient in the persistence of actin-positive vesicles can center objects of different sizes. We test model predictions by tracking the transport of exogenous passive tracers. The gradient of activity induces a centering force, akin to an effective pressure gradient, leading to the centering of oil droplets with velocities comparable to nuclear ones. Simulations and experimental measurements show that passive particles subjected to the gradient exhibit biased diffusion toward the center. Strikingly, we observe that the centering mechanism is maintained in meiosis I despite chromosome movement in the opposite direction; thus, it can counteract a process that specifically off-centers the spindle. In conclusion, our findings reconcile how common molecular players can participate in the two opposing functions of chromosome centering versus off-centering.

show abstract

“…Future work using better resolved imaging conditions could test this prediction. Alternatively, a system with a radial gradient in could have a roughly uniform density of vesicles (as observed 2 ) only if there are rapid processes of vesicle formation and annihilation throughout the oocyte cytoplasm 12 . The currently available data about the life-time of the vesicles is not precise enough to rule this out, and this scenario would predict that the accumulation of actin on the surface…”

Section: Comparison To Theoretical Analysis In Terms Of Active Brownimentioning

confidence: 99%

“…Accordingly, the spontaneous fluctuations, or activity of actin-positive vesicles decreases from the cortex to the oocyte center as quantified by their squared velocity v 2 . On the basis of a simple model describing the pool of actin-positive vesicles as an ideal suspension of self-propelled particles, we suggested that this gradient of activity from actin vesicles, which move by active diffusion 2 , generates an effective pressure gradient [11][12][13] and thus a propulsion force. It is thereby the trigger of the nuclear motion towards the oocyte center 14 .…”

Section: Introductionmentioning

confidence: 99%

Centering based on active diffusion in mouse oocytes is non-specific

Colin

Razin²,

Almonacid

et al. 2019

Preprint

Self Cite

View full text Add to dashboard Cite

The mechanism for nucleus centering in mouse oocytes results from a gradient of actin-positive vesicles. By microinjecting oil droplets and fluorescent beads, we analyze the consequences of the gradient of activity on transport of exogenous tracer particles of different sizes. We also use optical tweezers to probe rheological properties of the cytoplasm. We find that the gradient activity induces a general centering force, akin to an effective pressure gradient, leading to centering of oil droplets with velocities comparable to nuclear ones. High temporal resolution measurements reveal that passive particles, larger than 1µm, experience the activity gradient by a biased diffusion towards the cell center. Unexpectedly, this general and size dependent mechanism is maintained in Meiosis I but contrasted by a further process that specifically off-centers the spindle. These antagonizing processes depend on myosin activity, thus we reconcile how the same molecular actors can have two opposite functions (centering versus off-centering).

show abstract

Forces in inhomogeneous open active-particle systems

Cited by 16 publications

References 31 publications

Broken detailed balance and non-equilibrium dynamics in living systems: a review

Broken detailed balance and non-equilibrium dynamics in living systems: a review

Active diffusion in oocytes nonspecifically centers large objects during prophase I and meiosis I

Centering based on active diffusion in mouse oocytes is non-specific

Contact Info

Product

Resources

About