Spatiotemporal regulation of keratin 5 and 17 in the axolotl limb

Background: Amphibians have greater regeneration capability than higher vertebrates. They can regenerate their limbs after an amputation. As a limb is regenerated, a regeneration-specific epithelium called the apical epithelial cap (AEC) is induced. The AEC is an essential structure for limb regeneration. Despite the importance of the AEC, molecular marker genes have not been well studied at the molecular level. Results: In the present study, keratin5 (KRT5) and KRT17 were investigated in an axolotl-regenerating limb. KRT5 and KRT17 were expressed in a regenerating limb but down-regulated in a differentiating limb. KRT5 showed characteristic regulation in a regenerating blastema. KRT5 was suppressed in the basal layer of the AEC. This KRT5 suppression was correlated to the blastema differentiation and nerve presence. Simple skin wounding could also upregulate both KRT5 and KRT17 gene expression. But these genes were suppressed within a shorter time than in limb regeneration. Conclusions: The KRT5 and KRT17 gene profile can be a useful marker gene to investigate AEC in limb regeneration. Developmental Dynamics 241:1616-1624, 2012.