iiinova — where your digital self keeps evolving

Sophie G Martin @sophiemartinlab.bsky.social · 06/10/2026

Happy to share our latest work showing that fungal cell fusion not only requires local cell wall digestion but also inhibition of cell wall repair! PAK-family kinases promote cell fusion irreversibility by preventing cell-wall repair doi.org/10.1016/j.cu... Led by @juliacoronasserna.bsky.social

Post-fusion pak2 mutant cells with narrow fusion pore blocked by a vacuole

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Sophie G Martin @sophiemartinlab.bsky.social · 12/05/2026

This protein is essential for cells to communicate with a mating partner. Its discovery also reveals that diverse organisms use convergent pathways (with likely distinct evolutionary origins) to solve the same signalling problem.

Yeast cells communicating during mating. Green shows localization of the Sms1 scaffold.

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Sophie G Martin @sophiemartinlab.bsky.social · 17/03/2026

Despite yeast lacking known Arp2/3 complex regulators on endosomes, we show that Arp2/3 complex activity is required to shape these organelles The imagea shows electron micrographs of yeast endosomes in wildtype and after Arp2/3 inhibition.

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Sophie G Martin @sophiemartinlab.bsky.social · 06/05/2025

The surprise is that, over the same fold-change, cellular dimensions vary linearly with Cdc42 protein levels. So polarized growth has a linear relationship with Cdc42 levels. ➡️ Open question: How does this match with all the positive and negative feedback regulation that control Cdc42 activity?

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Sophie G Martin @sophiemartinlab.bsky.social · 06/05/2025

To test the importance of protein levels, we created an allelic series, exploring a 5-fold range in Cdc42 expression levels. We found that Cdc42 levels exhibit a switch-like transition for function during sexual reproduction, going from sterile to fully fertile cells within a 2-fold change.

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Sophie G Martin @sophiemartinlab.bsky.social · 06/05/2025

With several variants of cdc42 exhibiting cell fusion defects, including a widely used tagged allele (cdc42-mCherrySW) and mutants in cdc42 introns, we realized what they had in common: low levels of Cdc42 protein expression.

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Sophie G Martin @sophiemartinlab.bsky.social · 06/05/2025

We found that Cdc42 GTPase localizes to the site of cell-cell fusion in S. pombe cells (arrow in image) and plays important roles in the late stages of polarized secretion to promote local cell wall digestion.

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Sophie G Martin @sophiemartinlab.bsky.social · 02/05/2025

Thus, by transporting Fus1 along actin filaments nucleated by other Fus1 dimers, the formin-myoxin V association underlies positive feedback convergence of actin filaments in the focus.

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Sophie G Martin @sophiemartinlab.bsky.social · 02/05/2025

… and we find that the formin Fus1 is a myosin V cargo! The movie shows coincident formin Fus1 (green) and myosin V Myo52 (magenta) signals converging together.

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Sophie G Martin @sophiemartinlab.bsky.social · 02/05/2025

The cool finding is that the myosin V Myo52 (red), which transports secretory vesicles (purple) onto the fusion focus, dissociates from the pool of vesicles and joins the formin Fus1 (green) that assembles the focus. The two proteins physically associate…

Spatiotemporal map of the actin fusion focus

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Sophie G Martin @sophiemartinlab.bsky.social · 02/05/2025

We developed a three-color live fluorescence-imaging method that allows mapping the position of protein pools with a precision of 8 nm. Applying it to the actin fusion focus, an #actin aster that underlies yeast #cell_fusion, we show stereotypical order and compaction of the structure.

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Sophie G Martin @sophiemartinlab.bsky.social · 02/05/2025

New lab preprint! High resolution mapping of the actin fusion focus reveals myosin V-dependent transport of formin for actin aster compaction. A very cool work led by @valthomas.bsky.social and nice collaboration with Andrea Picco and @kaksonen.bsky.social! www.biorxiv.org/content/10.1...

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Sophie G Martin @sophiemartinlab.bsky.social · 23/12/2024

We present robust proteomics and phosphoproteomics datasets over sexual differentiation and cell-cell fusion. We used them to discover that TORC1 signaling is re-activated by pheromone signaling during nitrogen starvation, but there is lots more in. Browse here: pombephosphoproteomics.unige.ch

Heatmap of the phosphosites changing specifically during mating

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Sophie G Martin @sophiemartinlab.bsky.social · 23/12/2024

The work first presents a strategy to synchronize cells during sexual reproduction, using optogenetics, which allows population-based approaches.

Time course of cells synchronized during cell-cell fusion by optogenetics

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Sophie G Martin @sophiemartinlab.bsky.social · 23/10/2024

The Martin lab has an open postdoc position at the interface of #cytoskeleton and #condensate biology, in a fantastic research community! If interested, do not hesitate to contact us: mocel.unige.ch/research-gro... Please RT!

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Sophie G Martin @sophiemartinlab.bsky.social · 02/06/2024

Two weeks to the deadline for short talk selection. Submit your abstracts !!

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Sophie G Martin @sophiemartinlab.bsky.social · 29/03/2024

To all lovers of the #cytoskeleton: Do not miss the Plant and Microbial Cytoskeleton GRC and GRS 2024: Functional Diversity of the Cytoskeleton Great line-up of speakers! Check the website to register: www.grc.org/plant-and-mi...

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Sophie G Martin @sophiemartinlab.bsky.social · 07/02/2024

To all lovers of the #cytoskeleton: periodic reminder to register for the Plant and Microbial Cytoskeleton GRC and GRS 2024! Great line-up of speakers! Check the website to register: grc.org/plant-and-mi... Please spread the word!

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Sophie G Martin @sophiemartinlab.bsky.social · 18/12/2023

Very excited to advertise the Plant and Microbial Cytoskeleton GRC 2024: Functional diversity of the cytoskeleton. Co-organized with Alex Paredez, Sabine Müller and Alex Bisson. Great line-up of speakers! Check the website and register: www.grc.org/plant-and-mi...

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Sophie G Martin @sophiemartinlab.bsky.social · 02/12/2023

Are you an ASCB member? Submit you work to MBoC. From today, all members’ papers thoroughly reviewed. No desk rejection!

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Sophie G Martin @sophiemartinlab.bsky.social · 01/12/2023

En route for #cellbio2023 🚌🚃🛫 Looking forward to great science and seeing many 😀 We present one talk (by PhD student Melvin Bérard Sunday 4:15pm, room 254A) and two posters (Monday and Tuesday 12:15)

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