Molecular basis of positional memory in limb regeneration

Area of Science:

• Developmental Biology
• Regenerative Medicine
• Molecular Biology

Background:

• Limb regeneration in salamanders involves distinct anterior and posterior cell identities.
• Positional memory, established during development, is thought to persist throughout life.
• The molecular basis and modifiability of positional memory remain largely unknown.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying positional memory in axolotl limb regeneration.
• To investigate whether positional memory can be experimentally altered.
• To explore the implications of modifying positional memory for tissue engineering.

Main Methods:

• Identification of a positive-feedback loop involving Hand2 and Shh signalling in axolotl limb regeneration.
• Experimental manipulation of anterior cells using Shh exposure during regeneration.
• Analysis of gene expression and cell signalling post-manipulation.

Main Results:

• A positive-feedback loop between Hand2 transcription factor and Shh signalling maintains posterior cell identity.
• Residual Hand2 expression in posterior cells primes Shh centre formation post-amputation.
• Transient Shh exposure reprogrammed anterior cells to a posterior memory state, establishing a stable Hand2-Shh loop.

Conclusions:

• Positive-feedback mechanisms are crucial for the stability of positional memory during regeneration.
• Positional memory in regenerative cells can be reprogrammed, particularly from anterior to posterior identity.
• Modifying positional memory offers potential for advancing tissue engineering strategies.