Some proteins that are linked to neurodegenerative diseases can form both liquid droplets and amyloid fibers. But how are these two states connected, and where do the fibers grow? Leiden physicists Liru Feng and Louise Jawerth have discovered a counter-intuitive mechanism.

“We wanted to answer an open question: What happens to protein droplets as they age?” assistant professor Jawerth explains. “They look just like drops of oil in water, but they are droplets of proteins inside cells, also called condensates. Scientists have only relatively recently come to understand how they develop. Our findings on how they age— published in Nature Physics today—add an important piece to the puzzle.”

The droplets are very complex materials; they are liquid-like and can turn into solids that are glassy or fibrous. Jawerth states, “For 10 years or so, we have known that there is a link between fiber growth from these proteins and neurodegenerative disorders like Alzheimer’s disease or ALS. Our goal was to visualize, quantify and model this aging process, and we succeeded in doing so.”