Grateful and excited to launch the Otsuki Regeneration Group at the Hubrecht Institute!
🔗 www.hubrecht.eu/research-gro...

We study how tissues regenerate - and use those principles to build 3D tissues in vitro.

Full announcement: www.linkedin.com/in/leo-otsuk...

@hubrechtinstitute.bsky.social

If you are interested in reading more about positional memory, we can suggest this review that we wrote previously. It covers historically significant and inspiring experiments building up to our current understanding in the field: cshperspectives.cshlp.org/content/earl...
🧵13/14

Our work introduces positive feedback as a molecular basis for the stability and reprogrammability of positional memory. I would be excited if expanding this knowledge space helps in programming complex patterning information into cells to build synthetic tissues.
🧵12/14

We propose that a positive loop between Hand2 and Shh encodes posterior positional memory in the axolotl limb. Hand2 induces Shh, and Shh induces Hand2, resulting in a stable memory. Activating this loop in anterior cells readily reprogrammes their spatial identity.
🧵11/14

Excitingly, anterior cells transplanted to the posterior side were reprogrammed into posterior cells. By contrast, posterior cells transplanted anteriorly retained posterior identity. We found that Shh signalling was sufficient to posteriorise anterior blastema cells.
🧵10/14

We cross-transplanted anterior and posterior cells to the opposite side of the limb and asked if they maintain their original positional memory or if they switch to match their new location. We could track positional identity by live imaging mCherry and EGFP fluorescence.
🧵9/14

We wondered if Hand2/posterior memory is permanent once encoded, or if it can be changed later. To address this, we established a two-colour axolotl in which posterior and anterior limb cells are labelled with different fluorophores depending on their spatial identity.
🧵8/14

Modulating Hand2 expression in limb cells during development altered their positional memory and patterning outputs post-embryonically. We think that Hand2 'tells' cells that they are posterior for regeneration, and that this has implications for limb building.
🧵7/14

Using mutation/misexpression and genetic reporter axolotls, we found that Hand2 is both necessary and sufficient to express Shh. This genetic interaction is conserved in other vertebrates. In axolotls, Shh is the posterior signalling molecule driving limb regeneration.
🧵6/14

By comparing gene expression in anterior and posterior axolotl limb cells, we found the standout expression of the transcription factor Hand2 specifically on the posterior side of the limb. Hand2 is continuously expressed and could prime posterior positional memory.
🧵5/14

Positional memory has implications for bioengineering. Transplanting salamander cells in a way that alters their spatial organisation changes signalling topology and results in predictable (but amazing) phenotypes such as too many fingers - or even extra limbs!
🧵3/14

Salamander limb cells acquire spatial information during development and retain it stably throughout life as 'positional memory'. Positional memory directs signalling molecules (e.g. Shh and Fgf8) to switch on after injury in the correct places to drive regeneration.
🧵 2/14

Delighted that our work on positional memory is now published. We asked how axolotl cells 'know' which part of the limb to regenerate after injury.
www.nature.com/articles/s41...
A joy to work with super team Sarah Plattner, Yuka Sugiura, Francisco Falcon and Elly Tanaka.
🧵1/14

Very happy to (re)connect with Developmental Biology and Regeneration Biology folks on here. I study principles of limb and spinal cord regeneration in the axolotl and am interested in #devbio #regenbio and #synbio.