Periodic Reporting for period 4 - RegGeneMems (Understanding the evolution of regeneration-permissive gene expression and positional memory in Axolotl limb regeneration)
Periodo di rendicontazione: 2022-07-01 al 2023-10-31
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.
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.
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.
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.