Sperm cells swim by rhythmically beating their tail. This tail is known as cilium and can also be found in cells of the lungs and brain, where it helps to pump fluid through tissue. However, the details of how cilia generate their rhythmic beat are still unknown. Using innovative high-speed microscopy, researchers from the B CUBE – Center for Molecular Bioengineering and Cluster of Excellence Physics of Life (PoL) at TU Dresden have found another piece of the puzzle. They have captured, for the first time, that cilia twist during their beat. Their findings, now published in Nature Physics, suggest that the twisting motion may play a key role in coordinating the movement of tiny molecular motors inside cilia.
Every second, tiny hair-like structures called cilia are at work inside our bodies. They clean mucus from our airways and help brain fluid circulate. Without them, we would not even be born as cilia also propel sperm cells.
Cilia are powered by thousands of molecular motors working in unison. These tiny machines generate the movement that rhythmically bends the cilium. The motors work in supreme synchronization, generating a smooth, rhythmic pattern.
But despite their importance, scientists still don’t fully understand how cilia generate their rhythmic motion. Now, researchers at B CUBE and PoL have discovered a hidden twist in this process.
Measuring at High Speed With Nanometer Precision
The team led by Dr. Veikko Geyer and Prof. Stefan Diez from B CUBE turned to Chlamydomonas reinhardtii, a single-celled green alga with cilia nearly identical to those found in humans.
“It is very tricky to measure the twisting motion of the beating cilium. We had to find a workaround that would allow us to resolve the tiny displacements with high precision,“ explains Dr. Martin Striegler, who performed the experimental work in the project during his PhD thesis at the B CUBE.
To track the motion of cilia at such a small scale, the researchers attached tiny gold beads to the outside of the cilia. They used the beads as nanoscopic tracers and followed their movement with high-speed imaging at 5,000 frames per second. This allowed them to map cilia movement in three dimensions with nanometer precision – similar to filming a tiny hummingbird wing in slow motion.
The Hidden Twist
This cutting-edge approach opened the door to new, unexpected observations. The researchers found that cilia twist during the beat.
“During each beat cycle, there is a twisting motion that propagates along the beating cilium, from the base to the tip. We could convince ourselves that this was a feature of the ciliary beat which is likely key to how the ciliary beat works,” says Dr. Veikko Geyer.
However, to push the limits of the measurements, mathematical modeling was essential. “Without it, we could not interpret the data and confirm that cilia twist”, says Prof. Benjamin Friedrich who joined the team from PoL as an expert in data analysis and mathematical modeling.
Interdisciplinarity is the Key
This study is yet another interdisciplinary collaboration between the TU Dresden researchers at the B CUBE and PoL. Their work combined advanced cell biology, microscopy, image analysis, and mathematical modeling.
“Our team has uncovered a potentially pivotal new element in the complex dynamics of ciliary motion. We propose that the observed twist dynamics may play a key role in regulating motor activity within the beating cilium,” concludes Prof. Stefan Diez.
Original Publication:
Martin Striegler, Stefan Diez, Benjamin M. Friedrich and Veikko F. Geyer: Twist - torsion coupling in beating axonemes. Nature Physics (February 2025)
Link: https://doi.org/10.1038/s41567-025-02783-2
Scientific Contact:
Dr. Veikko F. Geyer
E-Mail: veikko.geyer@tu-dresden.de
Prof. Benjamin M. Friedrich
E-Mail: benjamin.m.friedrich@tu-dresden.de