Written by: Raman van Wee
Speaker: Joachim P. Spatz
Department: Biophysical Chemistry
Location: Applied Sciences
Spatz kicked off by showing us several videos of collective movement, both at the population level and at the cellular level. The latter included wound healing and formation of lateral line in zebrafish. Next a video of the motion of an epithelial monolayer of upper skin came by, it was very chaotic and movingly, which actually surprised me, I was expecting a rather static situation. Quantitively speaking groups of 10 cells up to 200 micrometer showed to behave as a collective, tuning the direction of the force to the group. In contrast there are leader cells, which go into a space on their own, followed up by the rest of the group. By reversing videos, behavior of leader cells could be investigated before it became apparent that the cell would become a leader cells. These cells seem to be predetermined, as they are at least 1000 micrometers apart of each other. The system regulates itself as shown by putting several leader cell too close to each other leading to the system eliminating those that are unwanted and thus leading to a stable, well distanced situation of leader cells. Remarkably if a group of followers, following a leader cell, threatens to exceed 10 followers, a new leader is brought forward from the group. I would say this requires extensive communication and coordination to execute well.
The second part of the seminar was about making a synthetic cell. This begins by making droplets having bilayer of membrane. Using sequential pico-injection microfluids, proteins and lipids could be inserted into the future cells. This sequential addition is very important, blending it all together at once doesn’t do it. Although once in the synthetic cell, the different components can not be separated with the eye, they do actually collaborate into larger structures. Interestingly, including myosine leads to the cell rotating around its axis. The need/strength for this rotating became clear when rotation was blocked by attaching a bead. In that case tension would build up until the cell would lose contact with the glass.
Afterwards we had the opportunity to speak to Spatz directly and ask him a few questions. We came to realization that he thinks in one year from now his synthetic cells will have some sort of mitochondria like energy factories. For the duplication part of life he thinks other research previously done can be very beneficial, drastically lowering the time required to integrate it in his cell. Besides, what actually surprised me was that his seminar was primarly based on 2 papers, whereas I expected more.
Collective migration is mechanically regulated by the length up to which cells collectively integrate forces together. The cells follow this rule to select and follow new leaders. In synthetic cells, components have to be inserted one by one although they eventually entangle. Forces in a cell can lead to the cell rotating around its axis.