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Katerina Ragkousi

@ragkousik.bsky.social

160 followers 260 following 8 posts

Biologist and Assistant Professor studying how cells build animals and how animals organize cells. Sea anemone (Nematostella) lab at Amherst College.

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Katerina Ragkousi @ragkousik.bsky.social · Feb 12

"Lateral cell polarization drives organization of epithelia in sea anemone embryos and embryonic cell aggregates"
www.pnas.org/doi/10.1073/...

Lateral cell polarization drives organization of epithelia in sea anemone embryos and embryonic cell aggregates | PNAS

One of the first organizing processes during animal development is the assembly of embryonic cells into epithelia. Common features unite epithelial...

www.pnas.org

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Reposted by Katerina Ragkousi

Development @dev-journal.bsky.social · 23d

Hydra body axis balance: a fight between two transcription factors

This Research Highlight showcases the work from Jaroslav Ferenc, Marylène Bonvin, Panagiotis Papasaikas, Jacqueline Ferralli, Clara Nuninger and Charisios D. Tsiairis:

journals.biologists.com/dev/article/...

Phenotype rescue upon Zic4 and Gata3 double knockdown. (A,B) Maximum projection confocal images of oral (A) and aboral (B) ends of animals after GFP RNAi (control), Zic4 or Gata3 RNAi, and Zic4+Gata3 RNAi. DNA in cyan, peroxidase activity in magenta and Nematocilin in orange. Panels on the right show magnifications of boxed areas on the left. Scale bars: 100μm. Note the ectopic peroxidase staining in tentacle tips upon Zic4 RNAi, and ectopic Nematocilin staining adjacent to the foot upon Gata3 RNAi, as well as rescue of both phenotypes in the double knockdown. (C) Percentage of animals with ectopic peroxidase staining in tentacles upon Zic4 KD and double KD. (D) Percentage of animals with ectopic Nematocilin staining adjacent to the foot in Gata3 KD and double KD. For examples of strong and partial phenotypes refer to Fig. S6. Data in G and H shown for n animals pooled from at least two independent replicates. ***P<0.001 (Fisher's exact test). (E,F) Schematic of proposed model for controlling the choice between basal disk and battery cell fate in Hydra. At the oral pole, Wnt signaling (black dot) activates Zic4 (orange) expression and thus basal disk identity. Without it, Gata3 dominates at the opposite end, leading to basal disk fate establishment (E). Experimentally depleting one of the factors results in ectopic cell fate acquisition at the opposite body end (F).

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Reposted by Katerina Ragkousi

ulrichtechnau.bsky.social @ulrichtechnau.bsky.social · 27d

We knew that cnidarians have stunning regenerative capacities. But the molecular and cellular mechanisms underlying the self-organization of gastruloids of Nematostella surprised us. A story of cell sorting and Notch signaling. Please check out the work of Sanjay's PhD work: doi.org/10.1101/2025...

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Reposted by Katerina Ragkousi

ulrichtechnau.bsky.social @ulrichtechnau.bsky.social · Aug 29

Finally, the excellent postdoc work of Emmanuel Haillot is out, where he dissected the integration of Wnt, MAPK and Notch signaling in defining mesoderm and endoderm identities in the diploblast Nematostella. Strikingly similar to sea urchins. www.nature.com/articles/s41...

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Reposted by Katerina Ragkousi

Michael Sars Centre @msarscentre.bsky.social · Aug 26

Congratulations Dr. Fournon Berodia @inesfournon.bsky.social 🎉🤩 We are very proud of Inés for successfully defending her PhD thesis conducted in the @prhsteinmetz.bsky.social lab. Thank you to opponents @ragkousik.bsky.social & @levayerr.bsky.social for insightful discussions 👏

Inés Fournon Berodia presents in front of an audience. She is wearing a black blazer and a white shirt. The slide on the screen has a black background, and reads "Hallmarks of epithelial cell extrusion". Below the title, a schematic of an epithelium, and the following text in bullet points: "Mitogen Activated Protein Kinase (MAPK)", "Facilitate extrusion" and "Protect surrounding cells"

Ines Fournon Berodia smiles widely, holding in place on her head a customized graduation hat.

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Katerina Ragkousi @ragkousik.bsky.social · Aug 6

Thank you!

Katerina Ragkousi @ragkousik.bsky.social · Aug 6

our unexpected results on the importance of a neural cell adhesion molecule in sea anemone epithelialization and gastrulation are just posted in the following preprint.

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

Depletion of a neural cell adhesion molecule disrupts both epithelial and germ layer identity in sea anemone embryos

Assembly of cells into epithelial layers marks the early steps of tissue organization and embryonic development in most animals. Although several conserved proteins are known to be essential for epith...

www.biorxiv.org

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Katerina Ragkousi @ragkousik.bsky.social · Jun 26

A host organelle integrates stolen chloroplasts for animal photosynthesis: Cell www.cell.com/cell/fulltex...

A host organelle integrates stolen chloroplasts for animal photosynthesis

Sea slugs steal foreign chloroplasts and store them in specialized organelles that facilitate photosynthesis and eventual digestion to mediate starvation resistance.

www.cell.com

Reposted by Katerina Ragkousi

Bardin Lab @bardinlab.bsky.social · Jun 13

Mark your calendars for May 18-22, 2026- in Roscoff, Brittany, for the next iteration of the Developmental Biology Conference Jacques Monod!

Bardin Lab @bardinlab.bsky.social · May 29

Coming back in 2026- a Jacques Monod Conference in Roscoff centered on Developmental Biology! This edition will be:
“Developmental regulation: from molecular to ecological niches” @lionlchristiaen.bsky.social and I hope to see you there! Info and dates coming soon.

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Reposted by Katerina Ragkousi

Aissam Ikmi @aikmi.bsky.social · May 28

We thought we were just studying mesoglea biogenesis…Turns out Nematostella has been hiding a sophisticated backup pressure valve! Work driven by the talented PhD student Soham Basu! @embl.org‬ www.biorxiv.org/content/10.1...

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Reposted by Katerina Ragkousi

genikhovich.bsky.social @genikhovich.bsky.social · Jun 9

The last part of @paulknabl.bsky.social 's PhD is now available at www.biorxiv.org/content/10.1...
Paul showed that BMP signaling is active in the diffuse nervous system of the sea anemone Nematostella and the box jellyfish Tripedalia. Moreover, suppression of BMP signaling in Nematostella leads...

The anti-neural role of BMP signaling is a side effect of its global function in dorsoventral patterning

In Bilateria with centralized nervous systems (e.g. in vertebrates or arthropods), the minimum of the BMP signaling activity gradient defines the position of the central nervous system. BMP-dependent ...

www.biorxiv.org

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Reposted by Katerina Ragkousi

Marine Biological Laboratory @mblscience.bsky.social · May 5

It's #MicroscopyMonday, so let's take a peek into the 🔬
This movie was taken by Shinya Inuoe, who built the polarizing microscope that allowed scientists to see mitotic spindle fibers live for the first time.

Dr. Inuoe premiered his research at MBL.

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Reposted by Katerina Ragkousi

Cnidarian developmental mechanisms group @clytia-vlfr.bsky.social · May 5

Intriguing findings from our Sendai collaborators Ruka Kitsui and Ryusaku Deguchi. While C. hemispherica spawns at dawn, Clytia IZ-D species spawns at dusk. This is not triggered by dark but, unexpectedly, by light-mediated extension of an autonomously-running 20h cycle. doi.org/10.1101/2025...

Cartoon of autonomous and light-modulated spwning cycles in Clytia IZ-D

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Reposted by Katerina Ragkousi

Eszter Posfai @eposfai.bsky.social · Mar 22

How many cells do you need to establish PCP? The magic number is 3! Beautiful work by Lena Basta in Danelle Devenport's lab. Happy to have contributed. www.science.org/doi/10.1126/...

Epithelial polarization by the planar cell polarity complex is exclusively non–cell autonomous

For cells to polarize collectively along a tissue plane, asymmetrically localized planar cell polarity (PCP) complexes must form intercellular contacts between neighboring cells. Yet, it is unknown wh...

www.science.org

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Reposted by Katerina Ragkousi

Scott Nichols @scottnichols.bsky.social · Dec 18

Happy to announce our latest paper! A fresh look at the sponge Aggregation Factor, a glycoprotein complex involved in self-recognition and adhesion. Previously thought to be sponge-specific, we report compelling structural links with proteins found in all animals! www.pnas.org/doi/10.1073/...

PNAS

Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans...

www.pnas.org

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Katerina Ragkousi @ragkousik.bsky.social · Mar 16

Congratulations to you and everyone involved!

Reposted by Katerina Ragkousi

genikhovich.bsky.social @genikhovich.bsky.social · Mar 13

Tanya's @tclebedeva.bsky.social paper on endomesoderm specification in the beta-catenin-negative area of the Nematostella embryo is out! www.nature.com/articles/s41...

β-catenin-driven endomesoderm specification is a Bilateria-specific novelty - Nature Communications

Lebedeva et al. show that unlike Bilateria, the embryo of the cnidarian Nematostella specifies its endomesoderm in the β-catenin-negative domain. In contrast, subsequent β-catenin-dependent axial patt...

www.nature.com

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Reposted by Katerina Ragkousi

eLife @elife.bsky.social · Mar 14

🧬 February's most-read Genetics paper looks at how #RNA travels between cells to control genes across generations #epigenetics: buff.ly/ulMGsBH

Have a paper people should see? See what our Editors look for: buff.ly/HmuOWDp

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Reposted by Katerina Ragkousi

Arnau Sebé-Pedrós @arnausebe.bsky.social · Feb 26

One week left to apply!

Arnau Sebé-Pedrós @arnausebe.bsky.social · Jan 8

Monod Conference "Origin of metazoans": fossils, genomes, cell biology, gene regulation, development, and more.

Join us in Roscoff for an exceptional speaker line-up and stunning venue!

🗓️Abstract deadline: March 4.

Register and share!
www.insb.cnrs.fr/fr/origin-me...

Origin of metazoans

Roscoff (Bretagne), France, June 16-20, 2025Deadline for application: March 4, 2025

www.insb.cnrs.fr

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Reposted by Katerina Ragkousi

Pawel Burkhardt @pawelburkhardt.bsky.social · Jan 8

Thrilled to see #choanoflagellates on the cover of Science Advances🤩. Our latest work "Electrical signaling and coordinated behavior in the closest relative of animals" out now. Link: www.science.org/doi/10.1126/... 👏 @jeffcolgren.bsky.social @msarscentre.bsky.social

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Katerina Ragkousi @ragkousik.bsky.social · Feb 19

by Jeyanathan et al from the Ulrich Tepass lab.
www.biorxiv.org/content/10.1...

Mitotic polarity oscillation promotes epithelial tumor progression

Mitosis of epithelial cells requires a transient loss of epithelial polarity [[1][1]–[5][2]]. However, the nature of this mitotic polarity oscillation and its functional consequences for epithelial de...

www.biorxiv.org

Katerina Ragkousi @ragkousik.bsky.social · Feb 12

it took me some time...🙂

Katerina Ragkousi @ragkousik.bsky.social · Feb 12

Thank you, Eszter! It is a few months old now. I am looking forward to your visit!

Katerina Ragkousi @ragkousik.bsky.social · Feb 12

"Lateral cell polarization drives organization of epithelia in sea anemone embryos and embryonic cell aggregates"
www.pnas.org/doi/10.1073/...

Lateral cell polarization drives organization of epithelia in sea anemone embryos and embryonic cell aggregates | PNAS

One of the first organizing processes during animal development is the assembly of embryonic cells into epithelia. Common features unite epithelial...

www.pnas.org

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