Dress like your data like @timonnk.bsky.social does!

I am very happy to share that my work on active deformations of lipid vesicles is finally out in Nature Physics. A nicer thread+movies coming soon, in the meantime:
www.nature.com/articles/s41...

Thx to Andreas, Hammad, Dmitry, Gerhard @laynefrechette.bsky.social and everybody else who contributed!

81% of Elon Musk thinks Elon Musk is a genius.

So yes: filaments transport in 3D allows to separate a contractile flux at the bottom of the well with an extensile flux pushing filaments back to the periphery through the network's 3D architecture.

If the DSS is through filament transport in 3D then severing those bundles in the middle of the well should stop it. So we performed laser ablation and *zap* the bundles are gone and the DSS contracts and dies out.

Well apparently yes! The network uses its 3D architecture to "suck" filaments at the center and "inject" them back at the periphery - again, we show this with tracking filaments in 3D. But it's barely visible in the data, so we developed a killer experiment ;-) go to the next block to see it..

Well, if it is not nucleation and it is not transport in 2D, we might as well take a look at the network architecture in 3D! Using confocal we observe this weird tent-like structure - is it possible that filaments are transported through it?

What we find is that transport on the wells surface is coherent with actomyosin sliding combined with some "gliding" due to motors sticking to the membrane. But the net flux is still contractile, so what is pushing filaments back to the periphery...???

It's not actin turnover, the classical answer: this DSS works in the absence of actin nucleators or in the presence of phalloidin, i.e. with stabilized filaments. No depolymerization is present. So it has to be transport of the filaments. We combine a bunch of techniques to observe it, like speckle.

... and we got this: continuous actin contraction for hours and hours without collapse to the center. We also show how the flow and the actin architecture are organized in space in a regular way.
The question is... what is sustaining this dynamic state? What "compensates" for this contractile flow?

So we took some precautions: we isolated the system inside lipid coated microwells to provide a solid geometrical boundary [some more details on why exactly in the paper of course], we lowered the actin:myosin ratio in the hope that lowering network entanglement might help, we crossed our fingers...

Problem is, traditionally reconstituted actomyosin networks just to a big whooooosh and quickly contract to a single point.

Of course understanding DSSs in cells is hard: different architectures (lamellipodia, stress fibers, cortex) interact and share monomers and dissecting all the "fluxes" present is different. You can use cell extracts, which are cool but still complex. Or... use the power of in vitro reconstitution!

This is the actin cytoskeleton in a cell (by A. Schaeffer). Actin structures arecontinuously renewed, contracted and dissassembled in cells, to create architectures that have always the same "shape" but are microscopically fueled by fluxes of new material. We call it a dynamic steady state (DSS).

New preprint out 🔥🔥 on my postdoc work with @manuelthery.bsky.social and @lblanchoin.bsky.social about how we can create sustained dynamic steady states of actin network inside microscopic wells that contract "forever" without collapsing! A thread 🧵
www.biorxiv.org/content/10.1...

It's the time of the year when I make a Christmas themed experiment to celebrate another year gone by: this year, a micropatterned branched actin network with myosin, aka a Christmarp(2/3) tree, doing weird stuff. Happy holidays Bluesky! 🥳🥳🥳

And we are on Le Monde for the frenchies in the audience!

Inaugurating my Bsky experience by sharing my favorite project so far, on which I had the big chance to collaborate, out now on @pnas.org .
I am sure @manuelthery.bsky.social has a lot to say about it, so let me just congratulate Clo, @bhagyanaths.bsky.social et al. for it! bit.ly/49aE6Cz More soon!