Deep evolutionary origin of limb and fin regeneration.

Area of Science:

• Evolutionary Biology
• Developmental Biology
• Genomics

Background:

• Salamanders and lungfishes are unique sarcopterygians capable of regenerating appendages at any level.
• Regeneration after fin endoskeleton amputation in actinopterygians was previously limited to polypterid fishes.
• The evolutionary origin of paired appendage regeneration in bony vertebrates remained unclear.

Purpose of the Study:

• To investigate the evolutionary origin of paired appendage regeneration in Osteichthyes.
• To compare gene expression profiles in regenerating blastemas of a ray-finned fish and a salamander.
• To determine if fin regeneration after endoskeleton amputation occurs in a broader range of actinopterygian species.

Main Methods:

• Conducted fin regeneration assays after endoskeleton amputation in various fish species.
• Performed comparative RNA-sequencing (RNA-seq) analysis on regenerating blastemas of Polypterus and axolotl.
• Utilized single-cell RNA-seq data for axolotl limb regeneration stages.

Main Results:

• Fin regeneration after endoskeleton amputation was observed in non-teleost actinopterygians (paddlefish, spotted gar) and several teleost species (cichlids, goldfish).
• Comparative RNA-seq revealed common genetic pathways and expression profiles in axolotl and Polypterus blastemas.
• A shared, regeneration-specific genetic program was identified between Polypterus and axolotl.

Conclusions:

• Paired appendage regeneration in Osteichthyes has a deep evolutionary origin, likely stemming from a common ancestor.
• The findings provide evidence for a shared genetic basis underlying appendage regeneration across diverse bony vertebrates.
• This study establishes an evolutionary framework for future research into the genetics of appendage regeneration.