Comparative proteomic analysis of tail regeneration in the green anole lizard, Anolis carolinensis

Abstract

As amniote vertebrates, lizards are the most closely related organisms to humans capable of appendage regeneration. Lizards can autotomize, or release their tails as a means of predator evasion, and subsequently regenerate a functional replacement. Green anoles (Anolis carolinensis) can regenerate their tails through a process that involves differential expression of hundreds of genes, which has previously been analyzed by transcriptomic and microRNA analysis. To investigate protein expression in regenerating tissue, we performed a whole proteomic analysis of regenerating tail tip and base. This is the first proteomic data set available for any anole lizard. We identified a total of 2646 proteins—976 proteins only in the regenerating tail base, 796 only in the tail tip, and 874 in both tip and base. For over 90% of these proteins in these tissues, we were able to assign a clear orthology to gene models in either the Ensembl or NCBI databases. For 13 proteins in the tail base, 9 proteins in the tail tip, and 10 proteins in both regions, the gene model in Ensembl and NCBI matched an uncharacterized protein, confirming that these predictions are present in the proteome. Ontology and pathways analysis of proteins expressed in the regenerating tail base identified categories, including actin filament‐based process, ncRNA metabolism, regulation of phosphatase activity, small GTPase‐mediated signal transduction, and cellular component organization or biogenesis. Analysis of proteins expressed in the tail tip identified categories, including regulation of organelle organization, regulation of protein localization, ubiquitin‐dependent protein catabolism, small GTPase‐mediated signal transduction, morphogenesis of epithelium, and regulation of biological quality. These proteomic findings confirm pathways and gene families activated in tail regeneration in the green anole as well as identify uncharacterized proteins whose role in regrowth remains to be revealed. This study demonstrates the insights that are possible from the integration of proteomic and transcriptomic data in tail regrowth in the green anole, with potentially broader application to studies in other regenerative models.KEY POINTSThis research is highly interdisciplinary, combining our previous analyses with these most recent findings: Appendage regeneration is a conserved trait among vertebrates and has been characterized in animals ranging from teleost fish (zebrafish), urodele amphibians (axolotl), anuran amphibians (Xenopus frog), squamate reptiles (various species of lizards), and even crocodilians (American alligator). Comparative genomic and proteomic analysis of this process allows us to identify the genetic pathways and cellular processes under evolutionary selection for this regrowth capacity. Activating these conserved genetic pathways and cellular processes will be critical to developing regenerative medical therapies in humans. The identification of proteins expressed in regeneration extends analyses based only on predicted proteins from transcriptomic analysis, and permits integration with protein‐expression studies of regrowing nervous and musculoskeletal structures.