Proteomics analysis of regenerating amphibian limbs: changes during the onset of regeneration

During amphibian epimorphic limb regeneration, local injury produces metabolic changes that lead to cellular dedifferentiation and formation of a blastema, but few details of these changes have been elucidated. Here we report the first global proteomic analysis of epimorphic regeneration comparing the profiles of abundant proteins in larval limbs of the anuran Xenopus laevis (stage 53) at the time of amputation (0dPA) and 3 days post-amputation when the regeneration blastema is developing (3dPA). We identified and quantified 1517 peptides, of which 1067 were identified with high peptide ID confidence. Of these 1067 proteins, 489 showed significant changes in quantity between the two groups. Taking into account identical peptides whose fold changes were within 20%, and not including peptides whose fold changes were below the observed fold changes of peptides for the internal standard (chicken lysozyme), we were able to identify 145 peptides elevated in 3dPA relative to 0dPA and 220 peptides in 0dPA relative to 3dPA. In this report, we focus on those proteins that were elevated in the 3dPA tissue relative to 0dPA. In this class were members of the annexin family (e.g. ANXA1, ANXA2, ANXA5) and the ANXA2-binding partner S100A10, which have important immunoregulatory roles in other systems and were also shown to be differentially expressed in stage 53 and 57 3dPA and 5dPA blastemas in our previous microarray studies. Besides elucidating the possible modulation of inflammation during amphibian limb regeneration, our proteomic study also provides insight into dedifferentiation by revealing up-regulation of proteins known to characterize many stem cells.