IISc scientists control human cell division with flashing blue light

At the Indian Institute of Science in Bengaluru, a team of researchers has accomplished something that seemed impossible just months ago: they can now trigger human cells to divide by flashing blue light at them. The technique, called Light-Induced Spindle Assembly or LISA, works by forcing a critical enzyme to cluster together, which tricks the cell into assembling the machinery it needs to split. The discovery answers a question cell biologists have wrestled with for years—what is the absolute minimum you need to start the division process?—and it does so in a way that opens entirely new paths for understanding cancer, developmental disorders, and how human reproduction works at the molecular level.

When a cell divides, it faces an enormous task. It must copy its DNA perfectly, then physically separate the two identical copies so each daughter cell gets one. To accomplish this feat, the cell builds a temporary structure called the mitotic spindle, made of thread-like filaments called microtubules. In normal circumstances, the cell relies on specialized organelles called centrosomes to organize these filaments. A centrosome is a staggeringly complex machine—more than 200 different proteins working in concert. For decades, scientists have tried to understand which of these proteins are truly essential and which are just helpers.

The key player turned out to be an enzyme called Aurora A kinase. Normally, Aurora A sits dormant at the centrosome until a large scaffold protein called Cep192 activates it. Scientists had long debated whether Cep192 was absolutely necessary or whether it simply served to pack many Aurora A molecules close together. The IISc team decided to test this using optogenetics, a technique that harnesses light to control cellular behavior. They engineered human cells so that Aurora A proteins were fused to a light-sensitive module derived from plants.

When the researchers exposed these modified cells to a brief pulse of blue light, something remarkable happened. The Aurora A proteins clumped together in seconds. That clustering alone was enough to activate them. Once activated, the Aurora A molecules recruited a partner protein called TPX2 and began assembling the microtubule threads needed for cell division. The massive Cep192 scaffold, it turned out, was completely expendable. Even more strikingly, when the team deliberately destroyed the cells' centrosomes—an event that normally cripples cell division and causes severe delays—repeated flashes of blue light restored normal division. The light-induced clusters substituted for the missing centrosomes, rescuing the cells from failure.

This represents a significant departure from how scientists have studied mitosis in the past. The previous standard method involved coating microscopic beads with Aurora A and injecting them into extracted frog egg fluid. That approach was labor-intensive, worked only in cell-free environments, required the presence of Cep192, and was irreversible. The LISA system operates inside living human cells and is fully reversible. When the blue light switches off, the Aurora A clusters dissolve. Scientists can now toggle the enzyme on and off repeatedly, like a light switch. The team achieved this by repurposing an existing optogenetic tool called LARIAT, originally designed to suppress proteins. They inverted the logic: what was built as a trap became an activator.

But the researchers discovered an important limitation. When they shone blue light on cells that were resting, not actively dividing, the proteins clustered but did not activate. This suggests that proximity alone is insufficient. The cell must also be in the right chemical state—likely because crucial partner proteins are sequestered in the nucleus until division officially begins. The team also knows that TPX2 gets recruited to these light-induced clusters, but the complete molecular recipe remains unmapped. That work lies ahead.

The implications ripple outward quickly. Aurora A malfunction and aberrant cell division are hallmarks of cancer. Flaws in cell division also underlie certain developmental disorders. By providing a precise, reversible, and simple way to activate division machinery on demand, this research gives cancer researchers and drug developers a new tool. They can now screen potential cancer-fighting compounds in a highly controlled setting. The technique also opens doors for studying human fertility and reproductive biology—human eggs and sperm naturally divide without traditional centrosomes, making them difficult to study. With blue light, scientists now have a way to understand these processes at a depth previously out of reach.