Sonic hedgehog (shh) expression in developing and regenerating axolotl limbs.

Area of Science:

• Developmental Biology
• Regenerative Medicine
• Molecular Biology

Background:

• Sonic hedgehog (shh) is crucial for vertebrate limb development.
• Axolotl limb development exhibits reversed differentiation polarity (anterior to posterior).

Purpose of the Study:

• To isolate and characterize axolotl shh (Ambystoma mexicanum).
• To investigate shh expression during axolotl limb development, regeneration, and in response to experimental manipulations.

Main Methods:

• RT-PCR to isolate axolotl shh.
• Localization studies of shh transcripts.
• Analysis of shh expression following anterior cell grafts and retinoic acid (RA) exposure.

Main Results:

• Axolotl shh shares high identity with other vertebrate shh genes.
• shh is expressed on the posterior margin of developing and regenerating axolotl limb buds, despite reversed polarity.
• Grafting anterior cells to posterior cells induces ectopic shh expression.
• RA exposure initially downregulates endogenous shh, then induces ectopic shh in anterior blastema cells.

Conclusions:

• Axolotl shh plays a role in limb patterning and regeneration.
• shh expression is regulated by tissue interactions and RA signaling in axolotls.
• Understanding shh regulation provides insights into limb development and regeneration mechanisms.