Differences in neural stem cell identity and differentiation capacity drive divergent regenerative outcomes in lizards and salamanders

PNAS, 2018 · DOI: 10.1073/pnas.1803780115 · Published: August 13, 2018

Simple Explanation

Lizards and salamanders can both regrow tails after amputation, but the regenerated tails are different. Salamander tails are almost identical to the original, while lizard tails have different structures and lack certain features. The key difference lies in the neural stem cells (NSCs) within the spinal cord of the regrown tails. Salamander NSCs can develop into various types of nerve cells, while lizard NSCs are more limited in their development. Hedgehog signaling, a communication pathway between cells, plays a role in how salamander NSCs develop, but it doesn't have the same effect on lizard NSCs. This difference contributes to the divergent regeneration outcomes.

Study Duration

Not specified

Participants

Adult lizards (Lepidodactylus lugubris, Anolis carolinensis) and salamanders (Ambystoma mexicanum)

Evidence Level

Not specified

Key Findings

1
Salamander NSCs can differentiate into multiple neural lineages, while lizard NSCs are restricted and primarily form astrocytes.
2
Hedgehog signaling regulates dorsoventral patterning in salamander ependymal tubes but not in lizard ependymal tubes.
3
Lizard NSCs exhibit a floor plate identity and maintain this identity even when hedgehog signaling is blocked.

Research Summary

This study investigates the divergent tail regeneration outcomes in lizards and salamanders, focusing on the role of neural stem cells (NSCs) in the spinal cords of regenerated tails. The research reveals that salamander NSCs can differentiate into multiple neural lineages and exhibit roof plate identity, whereas lizard NSCs are restricted in their differentiation capacity and exhibit floor plate identity. The study also shows that hedgehog signaling regulates dorsoventral patterning in salamander ependymal tubes, but not in lizard ependymal tubes, contributing to the differences in tail regeneration.

Practical Implications

Understanding Regeneration

Understanding the differences in NSC behavior between lizards and salamanders can shed light on the factors that govern regenerative ability and the loss of this capability in mammals.

Potential Therapeutic Targets

Identifying the specific genes and signaling pathways that regulate NSC identity and differentiation capacity could lead to the development of new therapies to promote tissue regeneration in humans.

Evolutionary Insights

Comparing the regenerative mechanisms in different species can provide insights into the evolutionary changes that have led to the loss of regenerative potential in mammals.

Study Limitations

1
The study was unable to target only NSC populations in vivo to knock down Shh expression to probe the sole contribution of the NSCs to patterning.
2
Transgenic approaches are not yet available for lizards due to their reproductive cycle.
3
The study acknowledges that lizard NSCs may not be true NSCs and suggests the term 'Sox2+ ependymal progenitor cells' may be more fitting.

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