Cells as we know them today—no matter the species—are feats of evolution; molecular machines with thousands of interlocking parts. But they didn’t start out that way.
Using the latest tools from the new field of synthetic biology, a team of biophysicists from Tecnische Universitaet Muenchen (TUM) in Munich, Germany, has constructed a synthetic version of an early cell, complete with some biomechanical function.
To build a primordial cell, the recipe is simple: all you need is a membrane shell, a couple of biomolecules that perform the most basic of functions, and some fuel to keep it going.
Here, TUM researchers used lipids (fat molecules) to create a double-layer cellular membrane that mimics a cell’s natural membrane. They then filled the membrane with microtubules, which acted as cellular ‘scaffolding’ to hold everything in place, and another molecule called ‘kinesin.’ These kinesin molecules serve as molecular ‘motors,’ transporting components throughout the cell by traveling along the microtubule scaffolding. Finally, they added the fuel: a compound called adenosine triphosphate, or ATP. The scientists likened this set-up to a liquid crystal layer within the membrane that is in a permanent state of motion. As lead author Felix Keber explained in a news release:
“One can picture the liquid crystal layer as tree logs drifting on the surface of a lake. When it becomes too congested, they line up in parallel but can still drift alongside each other.”
Once constructed, the research team then wanted to understand how these synthetic cells behaved, and if it would mimic natural cellular movements. And much to the team’s surprise—they did.
During a process called osmosis—where water droplets selectively pass through the membrane—the researchers noticed a change in the cells’ shape as water left the interior of the cell. The resulting membrane slack was causing the microtubules to stick out like spikes. These ‘spiked extensions’ were eerily similar to what the extensions that scientists have seen cells normally use to get around.
This observation cleared up a long-standing mystery: the way cells change shape and move around wasn’t random. The cells were simply following the basic laws of physics. This discovery then led the team to uncover the underlying mechanisms of other cellular behaviors—and even make predictions on other systems.
As the study’s lead author, Professor Andreas Bausch, stated in the same release:
“With our synthetic biomolecular model we have created a novel option for developing minimal cell models. It is ideally suited to increasing the complexity in a modular fashion in order to reconstruct cellular processes like cell migration or cell division in a controlled manner.”
In the future, the team hopes to build this knowledge to a point where they can understand the physical basis for deformed cells—with potential applications to disease modeling. Bausch added:
“That the artificially created system can be comprehensively described from a physical perspective gives us hope that in the next steps we will also be able to uncover the basic principles behind the manifold cell deformations.”