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I heard that getting in is one of the biggest challenges of all times in science 🤣

This piece is a reminder of how organismal models can help shape our thinking. I’ve always admired how drosophilists and other model organism researchers put their work in context. No dichotomy drawn here with stem cell research, from my viewpoint!

🔥 🔥 nice one!!

If you’re interested in this topic, please also check out @ebisuyamiki.bsky.social ky.social’s preprint.www.biorxiv.org/content/10.1...v2

Collectively, we report species-specific differences in protein production and degradation rates and provide *in vivo evidence* that degradative machineries are less active in human embryos than in mice. Finally, we establish a causal role for protein degradation on dev. tempo.

👇👇

To test if we could accelerate differentiation tempo as well, we targeted the degradation of IRX3 via Halo tagging + HALO-PROTAC and show it accelerates OLIG2 expression.

So, we demonstrate that modulating protein stability can influence the expression of a downstream TF.

To test causality, we inhibited proteasomal activity.
Three day treatments with proteasomal inhibitors mostly killed the cells, BUT we observe signs of differentiation deceleration

This meant that degradative machineries may be in charge:
✔️ differential abundance & stability of proteasomal particles
✔️ higher proteasomal activity in 🐭 compared to 👤 embryonic spinal cord

Proteins with multiple molecular functions show this trend, and this is true for proteins in different subcellular locations as well.

But which specific proteins show differences in stability? We confirm that most of the proteins indeed are more stable in human than in mouse as measured by SILAC proteomics. And this is also true for 1:1 homologous proteins (3402 proteins!).

Next, we compared protein abundance. We find selective upregulation of proteins related to degradation & mitochondrial metabolism in the 🐭. This was cool, as differential abundance was associated to a subset of functions that may explain the differences in stability!

We also found ~2-fold difference in global rates of production in 🐭 vs 👤. So, rates of protein production + degradation are species-specific.

First, we generated knock-in OLIG2-SNAP tagged mouse and human ESCs and measured OLIG2 turnover.
We find ~1.4-fold difference in decay and little differences in OLIG2 production. We also observed higher OLIG2 production rates in mouse.

Collaborative effort led by @Sotha Nakanoh & Despina Stamataki, with valuable contributions from Rayon & Briscoe lab members, as well as support from the proteomics teams (Crick & BI) and the BI bioinformatic team 🥂