Bmp-signaling and the finfold size in zebrafish: implications for the fin-to-limb transition.

This article investigates the role of bone morphogenetic protein (BMP) signaling in regulating the size of the finfold (FF) during zebrafish fin development, with implications for the evolutionary transition from fish fins to tetrapod limbs. Using zebrafish lines with genetically distinct FF sizes—including wild-type, hoxd13a-overexpressing short-FF transgenics, and long-FF leot1/lofdt2 mutants—the study demonstrates that enhanced BMP signaling correlates with shorter FFs, while inhibited BMP signaling associates with longer FFs. The findings suggest that modulation of BMP pathway components, influenced by Hox13 gene expression, may have contributed to FF reduction through increased apoptosis, a mechanism potentially co-opted during tetrapod limb evolution for digit formation. This research highlights a heterochronic shift in BMP signaling dynamics as a key factor in morphological changes from aquatic fins to terrestrial limbs.