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Biophysics

Spiral patterns in living cells could be used to create biological computers

02 Apr 2020
Egg ripples
Rippling egg: vortex-like waves spread out on the cell membrane of a starfish egg. (Courtesy: Nikta Fakhri and colleagues/MIT)

Ripples that appear on the surfaces of newly fertilized eggs closely resemble those found in other physical systems – according to Nikta Fakhri and colleagues at the Massachusetts Institute of Technology. The team discovered the similarity through statistical analysis of the spiral patterns produced by active proteins in newly fertilized starfish eggs. The researchers say that their discovery could lead to the development of biological computers that use ripples to process information.

When the egg cells of many species are fertilized, complex ripples are often propagate across their surfaces (cell membranes) before cell division begins. These waves are produced by a protein called Rho-GTP. This protein mostly sits inactive in the cell’s cytoplasm, but rapidly springs to action and attaches itself to the cell membrane when a separate hormone indicates cell division should begin. These ripples are known to produce intricate patterns as they propagate, but until now, the physical characteristics of the patterns have remained largely unexplored.

In their study, Fakhri’s team analysed the patterns in detail in fertilized starfish eggs, which are particularly large and easy to observe. To do this, they injected egg cells with a fluorescent marker that attached itself to Rho-GTP. Then they subjected the eggs to the relevant hormone in varying concentrations. In each experiment, they saw that concentrated waves of Rho-GTP oscillated out of moving central points to create spiral patterns. The team describes these centres as “topological defects” – freely-moving points where the molecules in a cell’s membrane do not join up seamlessly.

Universal laws

Fakhri’s group also observed that many spirals move across the membrane at a time. Some of the spirals arise spontaneously in pairs that move in opposite directions, whereas other pairs collide head-on, annihilating each other. After creating animations of the process, the team performed a statistical analysis of the motions of the spirals and topological defects. They discovered that these dynamics can be described by existing mathematical theories describing the dynamics of vortices. This suggested that the system’s behaviour is governed by the same universal laws as a wide variety of other, seemingly unrelated physical systems, albeit on widely differing scales.

The team found that the observed patterns were similar to turbulent vortices in the Earth’s oceans and atmosphere. The patterns also propagated in a way similar to electrical signals in the heart and brain. Perhaps more surprisingly, the velocities of clusters of spiralling waves resembled those found in quantum fluids. With further research, the team hopes that new techniques could emerge for manipulating these dynamics. If achieved, the biological ripples could be made to convey information and perform calculations in ways similar to quantum computers.

“Perhaps now we can borrow ideas from quantum fluids, to build minicomputers from biological cells,” Fakhri says.

The research is described in Nature Physics.

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