Bichirs employ similar genetic pathways for limb regeneration as are used in lungfish and salamanders.

ABSTRACT

Bichirs are a sister group to sarcopterygian and tetrapods that can fully regenerate their endochondral-skeleton-fins. Histological and transcriptomic comparison approaches have been used to investigate the morphology and genetic basis of bichir lobe-fin regeneration, with strong down-regulation of muscle-related genes and up-regulation of ECM-related genes and developmental genes being observed. Bichir limb regeneration involves similar cellular processes to those employed by lungfish and salamander, with MARCKS-like protein (MLP) that is known to be a putative regeneration-initiating molecule in salamander, also up-regulated in the early stages of bichir lobe-fin regeneration. These gene expression results suggest that limb regeneration pathways in these amphibians have a common ancestral inheritance, consistent with evolution from endochondral-skeleton-fin structures to endochondral-skeleton-limb structures of vertebrates.