In newt limb regeneration, retinoic acid typically:
In newt forelimb regeneration retinoic acid typically proximalizes positional identity reprogramming distal blastema toward proximal fate. Applied topically or via implanted beads, RA activates RAR-dependent transcription of Meis1/2 and proximal Hox9 genes, increases Prod1 expression level characteristic of proximal cells, suppresses distal HoxA13. Resulting regenerate duplicates proximal structures, converting wrist blastema into complete limb. Endogenous gradient with high RA proximally shapes normal pattern. Dose-dependent transformations demonstrated by Maden confirm proximalizing action;
Ref: NCBI Bookshelf, Limb Regeneration: RA proximalization, Meis, Prod1 regulation in newt limb regeneration.
