Allow me to present some work I have been *very* excited about for some time: how to detect signaling dynamics WITHOUT live-cell imaging!

https://www.biorxiv.org/content/10.1101/2021.01.06.425615v1

Since I started my biology career I have been absolutely smitten with signaling dynamics. But studying signaling dynamics is HARD! For Erk, you need to image single cells rapidly (like once every 3 min), for many hours, to get a clear picture.

As a result it is difficult (or impossible) to do things like genome-wide CRISPR screens for dynamics, to track dynamics in vivo in hard-to-image places, or to lineage-trace to learn the fates of pulsing cells.

We decided to approach this problem from a new angle. Can we build a simple synthetic gene circuit that acts as a "pulse detector", only turning on GFP expression in cells with Erk pulses, but not constant high or low Erk activity?

Long story short: yes! We performed a computational screen for pulse-detecting network motifs, finding a simple incoherent feed-forward loop can perform pulse detection. We then built it in cells using just a single engineered transcription factor and a classic GFP reporter.

It turns out this design worked great! The circuit responded to growth factor pulses 1 h or less, turning on GFP strongly enough to be easily detected by flow cytometry, and rejecting constant-on or constant-off signals.

It also works not just for our externally-applied pulses of growth factor (or optogenetic stimulation), but also for naturally-occurring endogenous pulses.

The design is quite general and we expect to be able to apply it to many other dynamically varying signaling pathways (p53, old buddy, I'm looking at you!). So stay tuned...

But maybe the coolest thing about this project is that it was carried out by an UNDERGRAD - @PavithranRavind - who designed the pulse detector system and carried out every experiment I just described. Pav: I am beyond proud of your capstone achievement - congratulations!