Javier Espadas

An Asgard Archaeon (Lokiarchaeum ossiferum) growing and retracting its arms

YouTube video by Schmidt Ocean Collaboration for Understanding | Searching for the Asgards

And ‘Searching for the Asgards’ the movie: www.youtube.com/watch?v=mgmE...

An 8-nm precise map in live cells, which revealed #actin aster formation by #myosin V-driven transport of #formin.

Happy to see this work now out! 😃

In collaboration with @kaksonen.bsky.social lab

#yeast #pombe #cell_fusion

@biology-unige.bsky.social

📢Internships on cellular nematics!

🔬Come for the pretty images, stay for the cool physics: each project combines in vitro experiments with advanced microscopy and image analysis.

📧Feel free to DM or email me with any questions.

Absolutely! And Asgard archaea don’t just have ESCRT-III, they also encode ESCRT-I, ESCRT-II, and ubiquitin, maybe an ancient endomembrane trafficking system? And with the internal vesicles described by the Baum and Bharat groups… it really feels like exciting discoveries are coming!!🤩

Charge segregation in the C-terminal linker of FtsZ enables Z-ring scaling with prokaryotic cell width Bacterial cytokinesis is orchestrated by the Z-ring, a cytoskeletal structure formed by treadmilling filaments of the tubulin-like GTPase FtsZ. During assembly, filament curvature must match the cell ...

Happy to share a new preprint from the lab: Marko became interested in whether the disordered linker of FtsZ might influence how the protein organizes into the Z-ring. And this led to some surprising findings!
Preprint: www.biorxiv.org/content/10.1...

@colomlab.bsky.social @labvanni.bsky.social @kaksonen.bsky.social @buzzbaum.bsky.social @Christopher Toret @rouxlab.bsky.social

Thank you all for the amazing work!!

All credits to the dreamteam that made this possible! what a pleasure and honor working with these people! 🥰
@diorgeps.bsky.social @mhakala.bsky.social @juanmagararc.bsky.social @joshuatran.bsky.social @mudgal17.bsky.social @Carlos Marcuello @Andrea Merino

The crucial test: We fused Heimdall Hofund to a fission-defective yeast ESCRT-III protein (Did2). This chimera restored Mup1 trafficking to vacuoles back to wt! A short amphipathic helix, present in Asgard and retained as fragments in eukaryotes, acts as a minimal membrane fission trigger!

Eukaryotic ESCRT-IIIA paralogs, known to form heteropolymers, retain Hofund elements at their N-termini.
In yeast, mutating these elements blocks ESCRT-III-dependent Mup1 transport to vacuoles.
So these elements matter in eukaryotes too.

Is this Asgard-specific, or conserved with their eukaryotic paralogs?
Hard to tell, since the exact molecular mechanism of fission by eukaryotic ESCRT-III remains blurry, probably due to its complexity.
Let’s figure it out!

Meet Hofund, the N-terminal amphipathic helix of 15 aa in Heimdall ESCRT-IIIA (named after Heimdall’s sword).
How do we know Hofund is the molecular trigger for fission?
Remove Hofund → ESCRT-IIIA loses fission activity.
Add Hofund alone → uncontrolled fission.

Through membrane fission! We show in vitro that the Asgard Heimdallarchaeota (Heimdall) ESCRT-IIIA subunit is inherently capable of triggering fission upon subunit turnover driven by ATP hydrolysis by Vps4.
And the key question: what actually destabilizes the membrane when ESCRT-IIIA turns over?

An Asgard archaeon with internal membrane compartments The emergence of eukaryotes from a merger between an archaeon and a bacterial cell ∼two billion years ago involved a profound change in cellular organisation. While the order in which different featur...

In a recent work, @buzzbaum.bsky.social and colleagues showed an Asgard archaeon with internal vesicles.
www.biorxiv.org/content/10.1...
How might Asgard ESCRT-III have contributed to compartmentalization?

Molecular basis for cellular compartmentalization by an ancient membrane fission mechanism The emergence of cell compartmentalization depends on membrane fission to create the endomembrane compartments. In eukaryotes, membrane fission is commonly executed by ESCRT-III, a protein complex con...

New preprint from the lab!!🎉
We show that Asgard archaea ESCRT-III proteins can trigger membrane fission and reveal its molecular mechanism, offering clues to how these cells may have built internal compartments. But do these organisms even have these compartments?
www.biorxiv.org/content/10.1...

Molecular basis for cellular compartmentalization by an ancient membrane fission mechanism https://www.biorxiv.org/content/10.1101/2025.11.28.690958v1

Incredible work, Juanma! It was an honor to be part of it. We already miss you in the lab, but we’ll be following your next discoveries very closely! 🤩🤩

New paper from the @rouxlab.bsky.social on Nature Communications! We study how membrane tension is spatially organized in cells. Using the mechanosensitive probe Flipper-TR to visualize tension across the plasma membrane of adherent cells and to dissect the conditions needed for a gradient to happen

🚨 Preprint alert 🚨

Don’t miss our latest story on how mycobacterial surface shedding shapes the host response !

What an amazing work!!
Excited to see it out after seeing how much hard work has been done here, and the result of it is equally impressive!!
Congrats to all authors!!!

Launching celldynamicslab.com, the homepage of our new group at EPFL working on cell fragmentation, membrane and cortex mechanics, FLIM imaging, and microfluidics tools. MSc/PhD or postdocs interested in quantitative cell biology are welcome to reach out. We're also hiring a lab manager in 2026!

Maria Tettamanti shows that inhibition of TORC2 by the small amphipath PalmC induces the TORC2-dependent internalization of sterols. Congrats to Maria and all coworkers involved, and to EMBOj for the efficient review process: use review commons! @biology-unige.bsky.social @sciencesunige.bsky.social

An Asgard archaeon with internal membrane compartments The emergence of eukaryotes from a merger between an archaeon and a bacterial cell ~two billion years ago involved a profound change in cellular organisation. While the order in which different featur...

An Asgard archaeon containing internal membrane compartments!! 😯
This will reshape our understanding of how the eukaryotic endomembrane system originated.
Congrats to @buzzbaum.bsky.social, @tbharat-lab.bsky.social and all ppl involved!
www.biorxiv.org/content/10.1...

An Asgard archaeon with internal membrane compartments

Brilliant study led by @fmacleod.bsky.social and Andriko von Kügelgen. Tight collaboration with @buzzbaum.bsky.social and lab. Congrats to all authors!

www.biorxiv.org/content/10.1...

This is a glimpse of the cytoskeletal structures we found doing U-ExM in more than 200 species, now in Cell🤩: shorturl.at/6oHvi
Amazing collaboration between @centriolelab.bsky.social , @dudinlab.bsky.social and @gautamdey.bsky.social labs.
I believe last one is a 🕷️
#FluorescenceFriday
#Microscopy

Interested in intracellular organization and membrane trafficking? 🥞 Join us at @melisupf.bsky.social in Barcelona! We’re looking for postdocs to apply for a Juan de la Cierva fellowship (PhD between Jan’24–Dec ’25). If you’d like to work with us, get in touch! www.aei.gob.es/en/announcem...

🚨Our collaboration with @centriolelab.bsky.social & @gautamdey.bsky.social is out today in @cp-cell.bsky.social
We show that #Expansion #Microscopy is a broad-spectrum modality for Euks, enabling 3D phenotypic maps rooted to phylogeny.
#ProtistsOnSky #SciComm #SciSky

www.cell.com/cell/fulltex...

It’s a tradition that I ask my “Physics III” class to create some memes about our class material. It’s *also* a tradition that they’re super good at this. Please enjoy, like and share! 🧪

(I promised my students extra game points if this goes nano-viral!)

(Front pic is my own entry.)

1/17

Please RT. Post-doc opportunity alert! 💥 closing 10th December.. Come join our team (www.thelowlab.org) at Imperial, London, working on the structure and mechanism of bacterial secretion systems.

For more details and to apply please see

www.imperial.ac.uk/jobs/search-...

Lab’s first paper is out!! We show the first structures of #Asgard #chromatin by #cryo-EM 🧬❄️
Asgard histones form closed and open hypernucleosomes. Closed are conserved across #Archaea, while open resemble eukaryotic H3–H4 octasomes and are Asgard-specific. More here: www.cell.com/molecular-ce...