Ivan Kairatov stands at the absolute forefront of biopharmaceutical innovation, bringing a wealth of experience from the rigorous world of research and development to the complex study of cellular mechanics. His career has been defined by a deep-seated interest in how the microscopic infrastructure of life—the proteins and filaments we often take for granted—coordinates the grand, visible movements of cells in both healthy and diseased states. With an expert eye for the intersection of technology and biology, Kairatov is uniquely positioned to interpret the groundbreaking findings coming out of modern laboratories, where the laws of physics and the mysteries of life are increasingly seen as two sides of the same coin. Today, he joins us to discuss a landmark study that redefines our understanding of actin, the protein skeleton that serves as the engine for some of the most dramatic physical transformations in the biological world.
The following discussion explores the intricate mechanics of cellular morphogenesis, moving beyond traditional views of reactive cell behavior to examine a newly discovered form of internal self-organization. We cover the specific role of the protein actin in facilitating shape changes in neurons and white blood cells, the limitations of previous “actin wave” theories, and the identification of self-propelled treadmilling actin filaments, known as SpTAs. The conversation also highlights the collaborative efforts at the Nara Institute of Science and Technology, the sophisticated microscopy that allowed these filaments to be seen as individual active particles, and the broader interdisciplinary implications of merging biology with modern physics to solve long-standing puzzles of life.
How does the protein actin facilitate the dramatic shape changes we see in cells like white blood cells or neurons?
Actin is far more than a static structural component; it functions as a dynamic internal skeleton that is constantly shifting and pushing to redefine the cell’s physical boundaries. This process, known as morphogenesis, is what allows a white blood cell to heroically engulf a bacterium or a neuron to extend a long, delicate projection to link up with a neighboring cell. Within the cell, these actin filaments form a dense network that can exert significant mechanical force, literally pushing against the flexible cell membrane from the inside out to create movement. Even in the context of disease, we see this protein’s power when a cancer cell forcefully squeezes through dense tissue to spread throughout the body, a feat of biological engineering that requires immense coordination. By understanding how actin drives these transformations, we gain a fundamental insight into the very nature of how cells navigate and interact with their complex environments.
The ability of cells to self-organize without external signals has long been a mystery; why has it been so difficult to pin down the mechanics of this spontaneous movement?
For decades, the prevailing narrative was that cells were primarily reactive, waiting for a chemical signal or an external cue to tell them where to go and how to change. This made the concept of self-organization a deep mystery of cell biology, as it was difficult to explain how the seemingly random, chaotic movements of molecules inside a cell could ever result in a structured, purposeful change in shape. Without a clear external signal to act as a guide, the spontaneous formation of protrusions appeared to defy the logical chain of cause and effect we usually look for in research. Part of the challenge was our own visual limitation, as we lacked the tools to see the granular, molecular-scale motion that orchestrates such complex higher-order organization. We were essentially seeing the end result of a cell’s movement without being able to see the individual “engines” that were driving it from within.
Can you tell us more about the specific research team and the context of the study that has finally shed light on this mystery?
This breakthrough comes from a highly collaborative effort at the Nara Institute of Science and Technology in Japan, led by Professor Naoyuki Inagaki. The team, which included Dr. Kio Yagami, Assistant Professor Takunori Minegishi, and several other dedicated researchers like Assistant Professor Kentarou Baba and Dr. Hiroko Katsuno-Kambe, spent years examining how actin behaves inside living cells. Their findings are so significant that they were prepared for publication in the prestigious journal EMBO Reports, with a scheduled release date of June 25, 2026. By focusing on human glioma cells—which are known for their ability to migrate spontaneously—the team was able to observe biological behaviors that occur even in the total absence of external guidance. This study represents a major milestone, providing the first clear evidence of a previously unrecognized form of actin self-organization that explains how cells generate movement on their own.
The researchers identified something called “self-propelled treadmilling actin filaments” or SpTAs. How do these differ from the “actin waves” that scientists were already familiar with?
The discovery of SpTAs, or self-propelled treadmilling actin filaments, is a complete paradigm shift from the older “actin wave” model that many of us grew up with. Scientists used to believe that shape changes were driven by waves that spread through the cell like a propagating chemical reaction, much like a ripple moving across the surface of a pond. However, using high-resolution live-cell microscopy, Inagaki’s team saw that these structures actually behaved more like individual, self-propelled particles, similar to the active particles studied in the field of physics. These SpTAs are independent, moving objects that navigate the interior of the cell with a sense of purpose and direction. This distinction is crucial because it moves the conversation away from fluid dynamics and toward a particle-based understanding of cellular mechanics, where each assembly of filaments acts as a discrete engine of motion.
Could you explain the process of “treadmilling” and how it actually powers the movement of these SpTA structures?
Treadmilling is a fascinating molecular process where the actin monomers, which are the building blocks of the filament, are constantly being recycled to create forward motion. During this cycle, new monomers are added to the front of the filament through polymerization, while older segments are simultaneously shed from the rear through a disassembly process. This continuous addition and subtraction requires the consumption of cellular energy, which is used to propel the entire filament assembly forward through the cell’s cytoplasm. It is essentially a microscopic version of a machine that builds its own track in front of it while tearing up the track behind it to provide the materials for the next section. This constant flux allows the SpTA to travel long distances within the cell, eventually reaching the boundary where it can begin to influence the cell’s overall shape.
What happens when these SpTAs reach the cell membrane, and how does that lead to the formation of a larger protrusion?
When a self-propelled treadmilling actin filament reaches the cell membrane, it doesn’t just stop; it uses its forward momentum to push the membrane outward, creating a tiny, initial protrusion. This initial “bump” in the cell’s surface then acts as a focal point, attracting other SpTAs that are moving through the cell to that specific site. As more and more of these biological active particles accumulate at the same location, their collective force drives the protrusion to grow larger and more stable, eventually leading to a significant change in the cell’s morphology. Dr. Yagami noted that this discovery effectively solves the mystery of biological self-organization by showing how molecular-scale motion can lead to a complex, organized structure. It is a beautiful example of how small, individual movements can aggregate into a powerful, coordinated physical transformation.
Professor Inagaki mentioned that these findings serve as a bridge between modern biology and modern physics. Why is this interdisciplinary connection so important?
The importance of this bridge cannot be overstated because it allows us to apply the rigorous, mathematical laws of physics to the often unpredictable world of living organisms. By classifying actin filament assemblies as a novel class of “biological active particles,” we can use existing physical models of self-propelled matter to predict how cells will behave under different conditions. This interdisciplinary approach provides us with a new set of tools to tackle the “enduring puzzle” of self-organization, which has been one of the most stubborn challenges in science. It moves us toward a future where we can describe cellular life not just in terms of genes and proteins, but in terms of force, energy, and physical particles. This holistic view is essential if we want to truly understand the mechanics of life and develop new ways to intervene when those mechanics go wrong, such as in the case of invasive cancer.
What is your forecast for the future of research into cellular self-organization?
I believe we are on the cusp of a revolution where we will see the development of “predictive morphogenesis” models that can accurately forecast how a cell will move or change shape based on its internal molecular energy. Over the next decade, especially following the insights provided by the Nara Institute team in 2026, I expect we will identify even more types of biological active particles that govern everything from tissue repair to the development of the human embryo. We will likely move beyond just observing these SpTAs and begin to develop biopharmaceutical interventions that can “throttle” or redirect these filaments to stop cancer cells from migrating or to encourage neurons to heal after an injury. This marriage of physics and biology will eventually allow us to engineer cellular behavior with the same precision we currently use in mechanical engineering, turning the “mystery” of the cell into a well-understood map of physical forces. It is a thrilling prospect that will fundamentally change how we treat some of the most difficult diseases known to humanity.
