Biophysics: Shaping cells with light

Researchers use light stimuli to shape cells and develop a model that explains the mechanisms – with implications for synthetic biology.

A main characteristic of all living organisms is that cells can dynamically alter their shape – otherwise, fundamental processes like cell division would not work. An international team led by LMU physicist Erwin Frey, Chair Professor of Statistical and Biological Physics and member of the ORIGINS Excellence Cluster, and Professor Nikta Fakhri from Massachusetts Institute of Technology (MIT), employing a combination of experimental and theoretical methods, has elucidated for the first time the mechanisms by which cells dynamically change their shape in response to environmental influences – and managed to control this process from the outside.

Earlier studies had shown that the formation of biological patterns through self-organizing proteins plays a crucial role in determining cell shape. The researchers investigated this complex network using the oocytes (egg cells) of the starfish Patiria miniata, which undergo a characteristic change in shape during division.

This shape change is driven by two enzymes: the small GTPase Rho and its activation enzyme GEF. By incorporating light-controllable molecular switches into GEF enzymes, the researchers managed to optogenetically influence the shape dynamics of the oocytes in a targeted manner. “With these switches, we were able to arbitrarily modulate the protein distribution in the cell through light stimuli, which led to deformations,” says Tom Burkart, lead author of the study. “So we generated a wide range of variants – from local pinching to an impressive deformation into a square cell.”

Subsequently, the scientists developed a theoretical model that describes how the optical stimulus triggers a change in the shape of the cell via chemical and mechanical interactions. They identified two key mechanisms: guided deformations, where the shape changes are locally limited, and unguided deformations, which spread throughout the cell by means of self-organization. “Our results show that living cells are much more versatile than previously assumed,” says Frey. “These findings could have wide-ranging implications for the development of synthetic cells and biomimetic materials and open up new opportunities for synthetic biology and cell-based technologies.”