Understanding the evolution of regeneration-permissive gene expression and positional memory in Axolotl limb regeneration

Project Information

RegGeneMems

Grant agreement ID: 742046

DOI

10.3030/742046

Project closed

EC signature date 10 May 2017

Start date 1 January 2018

End date 31 October 2023

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 325 659,00

EU contribution

€ 2 325 659,00

Coordinated by

FORSCHUNGSINSTITUT FUR MOLEKULARE PATHOLOGIE GESELLSCHAFT MBH
Austria

Periodic Reporting for period 4 - RegGeneMems (Understanding the evolution of regeneration-permissive gene expression and positional memory in Axolotl limb regeneration)

Reporting period: 2022-07-01 to 2023-10-31

Summary of the context and overall objectives of the project

We are working on understanding how, over evolution, the axolotl, which has a body plan similar to humans, evolved the ability to regenerate the limb. We are working on a specific growth factor that has changed its expression characteristics in axolotl compared to all other four-legged animals. We testing how this changed expression affects regeneration, and whether converting the pattern in axolotl to the mammalian one prevents regeneration.
This knowledge will help us to engineer adult sized tissues to replace damaged tissues.
Our goal is to understand how a successful example of regeneration works in order to understand how to promote regeneration in non-regenerative contexts.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

We have identified how the expression of the growth factor fgf8 changes over regeneration and in different sized animals. We have identified the genetic sequences that control its expression, and compared this to the human equivalent sequences. We showed that a signalling pathway called Wnt and its downstream components have shifted from epidermis to mesenchyme in axolotl to control this change in fgf8 expression. Fgf8 and Shh are turned on in opposite sides of the regeneration blastema to control thumb versus pinky formation. We found the factor, Hand2, in posterior adult fibroblasts tell them whether they should turn on Fgf8 or Shh during regeneration. Regenerating cells can be influenced by Shh itself to determine the exact proportions of anterior and posterior cells. The identification of these factors can be exploited in mammalian stem cells to engineer limb tissue.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

We have deveoped methods to image molecules in very large tissues that allow us to look at how these signalling factors are expressed in large, regenerating tissues. We have also developed spheroid cultures that allow us to study the molecular control of how Fgf8 and Shh hedgehog become upregulated in anterior and posterior cells. We now have exquisite control of cell identity along the anterior-posterior axis of the limb, which informs us how to engineer tissues.

Lineage analysis during regeneration of cells that had expressed sonic hedgehog during development