Another step towards synthetic cells

Building functional synthetic cells from the bottom up is an ongoing effort by scientists around the world. Its use in studying cellular mechanisms in a highly controlled and predefined environment creates great value for understanding nature and developing new therapeutic approaches. Scientists from the 2nd Physics Institute at the University of Stuttgart and colleagues from the Max Planck Institute for Medical Research were now able to take the next step towards synthetic cells.

They introduced functional DNA-based cytoskeletons into cell-sized compartments. Cytoskeletons are essential components of any cell that control their shape, internal organization, and other vital functions such as the transport- of molecules between different parts of the cell. When incorporating the cytoskeletons into the synthetic droplets, the researchers also showed functionality, including the transport of molecules or assembly and disassembly at certain triggers. The results were recently published in natural chemistry†

Challenge to mimic cytoskeletal functions

The cytoskeleton is a crucial part of any cell and is made up of several proteins. In addition to the basic function of giving the cell its shape, it is essential for many cellular processes like cell division, intracellular transport of various molecules and motility in response to external signaling. Because of its importance in natural systems, being able to mimic its functionality in an artificial setup is an important step towards building and designing a synthetic cell. However, it poses many challenges due to its diverse requirements, including stability, as well as rapid adaptability and responsiveness to triggers.

Synthetic biology researchers have previously used DNA nanotechnology to recreate cellular components, such as DNA-based mimics of ion channels or cell-to-cell linkers. To do this, they take advantage of the fact that DNA can be programmed or manipulated to self-assemble into a pre-planned shape through complementary base pairing.

DNA filaments as a synthetic cytoskeleton

“Synthetic DNA structures can enable very specific and programmed tasks as well as versatile design possibilities beyond what is available with the biologically defined tools. In particular, the structural organization of the DNA structures can differ from their natural counterparts, even possibly greater than the functionality of the natural systems,” said Laura Na Liu, professor at the 2nd Physics Institute, University of Stuttgart.

In addition, researchers Paul Rothemund, Elisa Franco and Rebecca Schulman had already succeeded in assembling DNA into micron-scale filaments, which form the basis for building a cytoskeleton. Since then, these filaments have been equipped with various functions, such as mounting and dismounting during external stimulation or in a compartment. Scientists from the University of Stuttgart and the MPI for Medical Research have now taken the next step to build an artificial cell, by using the filaments as a synthetic cytoskeleton and giving them different functionalities.

“It’s exciting that we can also activate the assembly of the DNA cytoskeleton with ATP – the same molecule that cells use to drive different mechanisms,” said Kerstin Göpfrich, Max Planck Research Group Leader at the MPI for Medical Research.

Accelerate vesicle transport

In addition, the team of scientists was able to induce the transport of vesicles along the filaments using the burnt-bridge mechanism introduced by Khalid Salaita. This mimics the transport of vesicles along parts of the natural environment cytoskeleton in cells called microtubules. “Compared to transport in living cells, transport along our DNA filaments is still slow. Accelerating it will be a challenge in the future,” said Kevin Jahnke, co-author of the paper and postdoc in Kerstin’s group. Göpfrich at the MPIMR.

Pengfei Zhan, postdoc in the group led by Prof. Laura Na Liu in Stuttgart, adds: “It was also a challenge to refine the energy landscapes of the assembly and disassembly capabilities of the filaments of the DNA nanostructure.” In the future, even more functionalization of the DNA filaments will be crucial to mimic natural cells even better. This allowed researchers to create synthetic cells to study cellular mechanisms in more detail or developing new therapeutic approaches.