Gur_Lab

[Dvir Gur @DvirGur]

There is a saying that it takes a village to raise a child, each person playing a specific role.
In our latest study, we found that forming a molecular crystal inside a cell is not so different. It takes an entire organelle: a lysosome-related organelle (LRO) equipped with a specialized molecular machinery, where every molecular component plays its own role. In this work, we show that guanine crystals form within dedicated organelles, iridosomes, that belong to the LRO family. These organelles assemble rapidly and in large numbers within zebrafish iridophores in the eye and skin, enabling vision and camouflage early in development. The study sheds new light on how cells orchestrate the formation of hundreds of crystal-forming organelles with remarkable precision.

The movie below shows time-lapse imaging of crystal formation dynamics in zebrafish eye iridophores.

Read the full manuscript here: https://t.co/Su54JkkiTu

This project was spearheaded by the incredibly talented Anna Gorelick-Ashkenazi, alongside many outstanding collaborators.

Grateful to the whole team for this journey! @yuval_barzi Tali Lerer-Goldshtein, @TsviyaO, @ZoharEyal1, @May_Gleser, Yonatan Broder, @nadavmishol, @RachaelDeis, Merav Kedmi, @WeizmannScience

[Dvir Gur @DvirGur]

How do you tell a molecular crystal how to grow?

In materials science, crystal morphology is usually an outcome. In biology, it’s often a design feature, tuned to deliver specific optical and other functional properties.

In our new paper in Small, we dissect how crystal growth can be steered at the molecular level, and show that simple synthetic polymers can not only reproduce biogenic plate-like morphologies, but also expand the accessible shape space.

By systematically varying polymer chemistry, we uncover three key principles:
• Multivalent interactions are important for sustained growth control
• Carbonyl-bearing functional groups selectively adsorb to the crystal stacking face, suppressing growth along the stacking direction
• Subtle changes in polarity and sterics redirect growth into plates, prisms, or even needle-like morphologies

This work was led by Dolev Brenman-Begin, who submitted her first first-author manuscript just before giving birth, and then handled the revisions with a newborn at home. A remarkable scientific and personal milestone. 💪🏽

The study was a close collaboration with (@barak_hirshberg) Barak Hirshberg‘s lab and his talented postdoc Jonatan Church (Tel Aviv University), and with (@LielS5) Liel Sapir Sapir’s lab (Bar-Ilan University).

Other authors and collaborators - thank you all:
Siddharth Sahoo, (@ZoharEyal1) Zohar Eyal , (@IdanBiran) Idan Biran, PhD , Nir Kampf, (@yuval_barzi) Yuval Barzilay, Anna Kossoy-Simakov, Lothar Houben. @WeizmannScience

https://t.co/KBdwimCLD0

[Gur_Lab @lab_gur]

RT @DvirGur: Super proud of our postdoc @SourabhBera4s and PhD student @RachaelDeis on receiving Travel Awards at ESPCR 2025. Huge congrats…

[Nature Chemical Biology @nchembio]

A new article by @ZoharEyal1 @RachaelDeis @DvirGur from @lab_gur at @WeizmannScience reveals that dynamic pH changes allow the formation of guanine crystals within specialized organelles, so that animals display brilliant colors

https://t.co/crCTIsvwiA

[Dvir Gur @DvirGur]

In materials science, crystallization is usually driven by supersaturation and tuned by factors like temperature and solvent composition. In biology, however, crystals must form under physiological conditions and ambient temperatures, which drastically narrows the “playground” for crystallization.

In our new study, just published in @nchembio, we used zebrafish crystal-forming cells as a model to uncover what drives biogenic crystal formation - and found that pH dynamics play a central role.

By integrating cryo-electron microscopy, spectroscopy, and pharmacological perturbations, we revealed how the iridosome microenvironment orchestrates guanine crystal formation. Early-stage iridosomes are highly acidic, which likely facilitates the buildup of protonated amorphous guanine and the assembly of macromolecular scaffolds. As the organelles mature and crystals expand, the pH gradually neutralizes, enabling further growth. When these pH changes are disrupted, crystal formation is severely impaired, highlighting the importance of tightly regulated organellar environments in biological crystallization.

This work was brilliantly led by @ZoharEyal1 , together with @RachaelDeis and Anna Gorelick Ashkenazi, and made possible through the contributions of many wonderful collaborators and friends: @yuval_barzi, Yonatan Broder, @KellumAshe74214, @NetaVarsano, Michal Hartstein, Andrea Sorrentino, Ron Rotkopf, Ifat Kaplan-Ashiri, Katya Rechav, Rebecca Metzler, Lothar Houben, Leeor Kronik, Peter Rez.

#Crystallization, #Biomineralization, #MaterialsScience, #CellBiology, #StructuralBiology, #CryoEM, #Spectroscopy, #Zebrafish

Check it out:
https://t.co/upRsRXdrx6

[Dvir Gur @DvirGur]

Just as Batman has Robin and Mario has Luigi, melanophores—the black pigment cells—have their counterpart: leucophores (from the Ancient Greek λευκός, meaning white). These often-overlooked cells play a key role in generating the remarkable colors and patterns we see in many animals.

In our new study, published in PNAS (@PNASNews ), we investigated how leucophores generate their white appearance by crystallizing uric acid—a compound commonly known for its involvement in human diseases such as gout and kidney stones

To understand how this process compares to other pigment cell types, we used a combination of hashtag#scRNA-Seq, hashtag#metabolomics, and hashtag#cryoEM to study leucophores alongside iridophores, which create iridescent effects using guanine crystals, and xanthophores, which carry yellow pterin pigments.

Our findings reveal that while these pigment cells share underlying cellular machinery, their distinct pigment chemistries give rise to specialized molecular programs. Most strikingly, we uncovered star-like fibrous scaffolds within leucosomes. These structures likely serve as templates for the growth of one-dimensional uric acid crystals, which radiate outward and scatter light with high efficiency, shedding new light on the molecular strategies organisms use to construct whiteness from molecular building blocks.

This project was led by our outstanding PhD student @yuval_barzi , with valuable contributions from a wonderful team of collaborators and friends.

Read the full paper here:
https://t.co/l7xMQuNQnb

The movie below provides a high-resolution view of the ultrastructure of distinct pigment organelles, captured using cryo-electron tomography. From left to right: leucosomes (uric acid), pterinosomes (pterin), and iridosomes (guanine).

@WeizmannScience
@ZoharEyal1, YaelNoy, @NetaVarsano ,@TsviyaO ,@SOURABHBERA12, Tali Lerer, Merav Kedmi, @PoratZiv,@IddoPinkas, Smadar Zaidman, @dezorellaNili

[Gur_Lab @lab_gur]

Thrilled to see our work on the "Genetic Control Over Biogenic Crystal Morphogenesis in Zebrafish" featured on the cover of Nature Chemical Biology! @nchembio. Proud to have our research highlighted in this way :)
https://t.co/3gkxL6EThG

[Gur_Lab @lab_gur]

Our new website is live!
Check it out, and don’t miss the 3D virtual tour 😀

https://t.co/mdJNCgltPI

[Rachael Deis @RachaelDeis]

🚨 Check out this awesome News & Views by Peter G. Vekilov on our latest work! Genes and crystals are not so separate 🤩🧬✨🔬@DvirGur @ZoharEyal1 @nchembio
#nature #guanine #crystals #genes

https://t.co/tQcCyM10SL

[Pete Bankhead @petebankhead]

Let me introduce: InstanSeg 🦠🔬💻👩‍🔬

This *would* have been a short thread about Thibaut Goldsborough’s PhD work… but he solved too many problems.

Now it's a long thread about 2 preprints, a whole new approach to cell segmentation & #opensource software to make it easy to use

[Gur_Lab @lab_gur]

🎉 Huge congratulations to @yuval_barzi on officially receiving his MSc degree this week! 🎓 We’re thrilled that you’ll be continuing your journey with us, diving deeper into crystal formation research using medaka. 🐟 Keep shining, Yuval – exciting discoveries ahead! 🌟 #CrystalFormation #Medaka

[Gur_Lab @lab_gur]

@JuliaMMagdalena Thanks Julia!!

[Dvir Gur @DvirGur]

Like a master craftsman, animals can mold basic materials into a variety of crystalline structures to perform functions ranging from pattern formation to camouflage and vision. The underlying mechanisms of this process have long remained a mystery.
https://t.co/g2KEIxlsDV

[Gur_Lab @lab_gur]

🚨 New Publication Alert! 🚨 We’ve uncovered the bio-chemical control behind crystal formation in zebrafish iridophores 🐟✨. Our study reveals how the genetic regulation of guanine and hypoxanthine ratios shapes diverse crystal morphologies. This discovery could pave the way for innovative biomaterials and therapies! Check it out: https://t.co/0JTvRMEplW

#Biomaterials #Genetics #Zebrafish #Crystallography #NatureChemicalBiology

[Gur_Lab @lab_gur]

Better late than never! Happy belated birthday to Tali - the best lab manager we could ask for!! 🎉❤️🥳🔬🐠🐟

[Weizmann Institute @WeizmannScience]

Congratulations to Dr. @DvirGur of the Molecular Genetics Department upon receiving the European Research Council (@ERC_Research) 2024 Proof of Concept Grant #ERCPoC @lab_gur

[Gur_Lab @lab_gur]

For an ERC-funded project, we are searching for talented postdocs/PhD students to carry out exciting studies involving genetic engineering, functional crystals, and optical and electron microscopy at the @WeizmannScience. Prior experience working with yeast is an advantage.

[Gur_Lab @lab_gur]

🐟 🐠 check out our recent work featured in Nature Materials News and Views 🧬 🔬!

[Gur_Lab @lab_gur]

Thrilled to see our recent work featured in Nature Materials News and Views!

Check it out:
https://t.co/qePB8c4KVh