What Makes Neurons Contract to Generate Tension?

BPJ_111_7.c1.inddWhen preparing for the cover image for the October 4 issue of Biophysical Journal, we started with an image that resembled an art painting, probably something between Monet and Pollock (not claiming that it’s up to their standards). It was pretty, at least to us, but we thought that it didn’t tell a story. So we thought to ourselves, “What is the message that we want to tell if we have the chance?”

This is how the current version of our cover image came about. On the left, it has a bunch of curved green and red lines, while on the right there is the same set of lines but straightened. These are actually real experimental images achieved by genetically encoding the neuronal membrane to fluoresce in green—thanks to the technology enabled by the late Roger Tsien, while staining the cytoskeleton, in this case microtubules, in red. The implication is that buckled (curved) neurons would always contract and become straight again in less than 5 minutes with the contraction vs. time profile following an exponential decay. We used genetic and pharmaceutical tools to study this phenomenon and found that the acto-myosin machinery was the active driver, while microtubules contributed in a resistive/dissipative role.

The neurons contracted because the machineries were trying to build up a mechanical tension, which was shown to be critical for vesicle clustering, a process central to signal propagation across neurons. Yet, we do not know how tension leads to clustering. It’s like we know that we can drive from New York to Los Angeles, but we do not know the path. Unfortunately, there isn’t an app for that in our case. Knowing the players (tension generators) involved is the first step to answer this question.

There are quite a few implications, mostly to our understanding of mechanics in neuroscience. A better understanding always leads to new ideas and approaches to solve problems, which, in the context of nervous system health, are usually costly and sometimes a matter of life and death.

– Alireza Tofangchi, Anthony Fan, Taher Saif

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