Congratulations @philipschoene.bsky.social on defending his Master’s thesis on the supremacy of mechanics in Hydra regeneration from aggregates of dissociated cells. Expertly guided by @anaisbailles.bsky.social. #experiment and #theory #LoPaTs @mpi-cbg.de @poldresden.bsky.social #stuffthatmatters

Thanks a lot to @elisecutts.bsky.social for nicely highlighting and putting in context our article! It was very interesting to discuss together, notably about the analogies between the emergence of order in Hydra and other physical phenomena.

Thank you Mathieu! 😁

The community of Drosophila researchers is amazing, mutually supportive and collaborative. Right now a key resource for our community, @flybase.bsky.social , is threatened by the cancellation of its NIH grant and is seeking community help in raising short term funds 1/n 🧪 please share

This is a question for #LISH25 :)

Our beautiful Hydra made the cover!!! 😍😍😍
An experiment performed by Pavel Mejstrik with a HCR protocol by @giuliaserafini.bsky.social, @paveltomancak.bsky.social lab @mpi-cbg.de
Actin fibers in blue, nuclei in orange.

And in case you were wondering if Hydras look like their mythological counterparts, the regenerated aggregates can indeed have multiple heads! And their number is scaling with the size of the aggregate.

You can find more movies here, and do not miss the supplementary figures: tinyurl.com/3wz4mavb. Thanks to the people who contributed to this work, Giulia Serafini, Heino Andreas, Chris Zechner, Carl Modes, @paveltomancak.bsky.social and @mpi-cbg.de. A big thank to the Hydra community for the help 💚

Embryos hatch in a configuration similar to our stretch experiments: they break the shell on one side and stretch outside this hole. Actin is indeed aligned with the direction of the stretch. The mechanism we uncovered could also provide robustness to the embryo patterning. (9/9)

We think this is a great example of how mechanics impacts and potentially drives self-organization and the emergence of order in collectives of cells, and how analogies from physics can help understand it. Of course, ‘what about embryos?’ asked Pavel. (8/9)

Altogether, this suggests that the ordering of actin in aggregates happens through cell-cell interaction and is favored by anisotropic stretch but delayed by supracellular (smectic-like) fibers. Wnt head organizers would only play a role later. (7/9)

What about stretch? We constrained the aggregates in agarose except for a hole. The tissue protrudes inside the hole, and the resulting stretch has a fast effect on actin alignment in the whole aggregate. Importantly, Wnt head organizers were not yet present in the protrusion. (6/9)

We mechanically perturbed the aggregate by changing topology ('skewer') and geometry ('sausage'). Topological changes alone do not significantly bias the actin orientation. Geometry has an indirect effect on actin orientation but is not associated with curvature anisotropy. (5/9)

Measurement of the nematic (orientation) order parameter in space and time showed growing ordered domains and line defects. This suggests that local cell-cell interactions drive the transition from disorder to order. (4/9)

First, we quantified the emergence of order over days using analogies with liquid crystals. Rotational symmetry is broken. Surprisingly, translation symmetry is also partially broken. This smectic behavior is associated with the formation of supracellular actin fibers. (3/9)

Hydra is not only immortal but also can self-organize a whole organism from a clump of thousands of cells. In these aggregates, actin polarity is completely lost in cells and is re-established de novo. We studied how the transition from disorder to order happens. (2/9)

Very happy that the first article from my postdoc work in the Tomancak lab is now published @PNAS! www.pnas.org/doi/10.1073/.... We studied the self-organization of actin in aggregates made from Hydra cells. Thread below (1/9)

Publication @pnas.org www.pnas.org/doi/10.1073/...

Stretching the immortal Hydra. Publication by @paveltomancak.bsky.social group with Carl Modes @mpi-cbg.de & @zechnerlab.bsky.social shows how cells can create a new organism from scratch by coordinating their mechanical properties. @anaisbailles.bsky.social @pnas.org www.mpi-cbg.de/news-outreac...

To recognise and celebrate @svobodalab.bsky.social's pivotal contribution to Woodstock Bio2 + Night Science, #TCTeAC, I am starting this "What Petr Svoboda did at Woodstock?" thread. If you were there - #contribute and #retweet.

"Petr Didn’t Submit an Abstract. #TCTeAC Submitted to Him."

Updated a broken link in my substack post about the
#ColossalBio #DeExtinction #DisInformation campaign – dire wolves are still extinct.

open.substack.com/pub/devoevom...

#LoPaT @anaisbailles.bsky.social bringing up the wonders of #Hydra, #physics, disorder to order transition and tissue mechanics to #TCTeAC