Have you ever wanted to *see* receptor activity in embryos? If so, our new preprint is for you! In it, we showcase a new live-cell biosensor for visualizing receptor tyrosine kinase activity in living embryos – pYtags!.

I’ll be starting my undergrad-powered lab this summer at Claremont McKenna College and I’m super excited to continuing exploring new signaling biology with pYtags. If you are interested in tagging your favorite RTK (in flies or in other model systems), please reach out!

Huge thanks to: @toettch for being the best advisor. @PayamFarahani for developing pYtags and starting this project with me. @rpkimyip and @EPosfai for amazing egg chamber imaging. Alison and Stas for gorgeous trachea imaging. And @OatmanHarrison who can segment anything!.

Our data is consistent with a new conceptual model for terminal patterning where a local domain of Torso activity, tuned by negative feedback, produces a long-range gradient of ERK. Check out the paper to learn more!

Second, Torso activity was much more restricted to the poles than the broad gradient of ERK activity, consistent with a model where the ERK gradient forms via diffusion. We previously showed the same thing with an optogenetic stimulus.

First, Torso activity decreased over developmental time while ERK activity was sustained at a high level. This led us to the discovery of negative feedback from the ERK pathway regulating Torso’s phosphorylation state.

We then asked what we could learn about Torso by comparing Torso activity with downstream ERK activity. Two things surprised us, highlighting that we can’t always accurately infer receptor activity from downstream signaling.

And pYtags didn’t just work for Torso! We also made pYtags for EGFR and FGFR/Btl, and those worked just as well. The pYtag strategy is so powerful because it is generalizable to any RTK of interest.

We were particularly interested in Torso, the RTK controlling terminal ERK signaling at the poles of the fly embryos. I tagged Torso with the pYtag and saw gorgeous signal at the poles just where we expected it! pYtags work in embryos!

pYtags use an exceptionally specific and orthogonal pTyr / SH2 binding pair (ITAM + ZtSH2) to recruit a fluorescently tagged protein to phosphorylated RTKs.

The Toettcher lab recently developed a new class of biosensors for receptor tyrosine kinases (RTKs) called pYtags. They work beautifully in mammalian cell culture. But could pYtags be used to measure endogenous RTK activity in embryos?.

There are lots of reasons to want to visualize receptor activity in vivo – measuring morphogen gradients, detecting subcellular receptor activation during chemotaxis, understanding signaling dynamics (i.e. ERK waves), etc etc. But we need new tools!.

RT @laurentodorov: What can a simple sea squirt tell us about neural crest evolution?🔬 Explore the latest research from my PhD journey at @….

Can’t wait for all the awesome science to come from the @h4rrymcnamara lab!.

RT @h4rrymcnamara: Our study decoding gastruloid symmetry breaking is now live @NatureCellBio!. Thank you to the N….

RT @toettch: It's new-preprint-from-the-lab day! (In my opinion the most fun + authentic day to celebrate a new publication.) Check it out:….

RT @h4rrymcnamara: new results! We describe an optogenetic method to 'paint' patterns of morphogen signals in zebrafish embryos to guide th….

RT @toettch: Happy to share a new opto-technique preprint from the lab spearheaded by the indomitable @EH_Reed!. In it we report a techniqu….

RT @Dev_journal: Optogenetics reveals how the embryo got its stripe. Read this Research Highlight showcasing work from Emily Ho @emkolen, J….

More details in the tweetorial here Thanks to @Dev_journal for a very positive review process and to all my coauthors for making this such a fun project!.