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Spiralling ripples in starfish oocytes. (MIT)

Life Begins With Mesmerising Waves Swirling Over Microscopic Bodies, Study Reveals

27 MARCH 2020

As life starts, the crazy whirl begins. That's not poetry or philosophy. It's science.

Once an egg is fertilised, billions of proteins ripple out across its surface, unleashing a dizzying cascade of swirling patterns. These spiralling arcs aren't for show, though; the phenomenon may be pretty, but it's also a fundamental part of nascent cell division.

 

"The egg is a huge cell, and these proteins have to work together to find its centre, so that the cell knows where to divide and fold, many times over, to form an organism," says physicist Nikta Fakhri from MIT.

"Without these proteins making waves, there would be no cell division."

In a new study, Fakhri and fellow researchers examined what these whirling waves look like up close, examining their propagation patterns on the cell membranes of starfish eggs (Patiria miniata).

Beyond grasping the biology of starfish oocytes, the researchers wanted to see how these patterns might compare to similar wave phenomena in other kinds of systems – examples of what physicists call topological defects.

As the researchers explain in a new paper, these kinds of turbulence-like behaviours can be seen in both physical and biological matter, in scales that range between the cosmological and the infinitesimal: from swirling vortices in planetary atmospheres to bio-electrical signalling in the heart and brain.

Yet while the similarities may be abundant, the nature of their sameness remains mysterious, theoretically speaking.

 

"Despite such substantial progress in the understanding of topological defects and their functional implications, it is not yet clear whether statistical laws that govern such topological structures in classical and quantum systems extend to living matter," the authors explain.

In their starfish experiments, the team introduced a hormone to mimic the onset of fertilisation in the oocytes, in which triggered waves of a signalling protein called Rho-GTP ripple through the membrane for several minutes at a time, with the results being imaged via microscope thanks to the help of fluorescent dyes that attach to Rho-GTP.

By varying the concentration of the hormone trigger, the researchers were able to observe a variety of swirling spirals emanating throughout the egg's surface medium.

"In this way, we created a kaleidoscope of different patterns and looked at their resulting dynamics," Fakhri says.

"Not much was known about the dynamics of these surface waves in eggs, and after we started analysing and modelling these waves, we found these same patterns show up in all these other systems. It's a manifestation of this very universal wave pattern."

After filming and analysing the phase velocity in the wave patterns, the researchers say the very beginnings of life, as seen in these starfish eggs, resemble the dynamics observed in bacterial turbulence, active nematics, and the quantum systems of Bose–Einstein condensates.

If that's a bit jargon-heavy for you, in more poetic and philosophical terms, it's also like – as The Killers sing – a hurricane that started turning when you were young.

The findings are reported in Nature Physics.