The Murphy Roths Large-MRL engineered mouse strain spontaneously regenerates ears and even heart tissue.  Such a regenerative process is known for amphibians; mammals generally forming scar tissue during the process of wound repair. The groups of Ellen Heber-Katz (The Wistar Institute, Philadelphia, PA) and Phillip B. Messersmith (Northwestern University, Evanston, IL) discovered these exceptional capabilities a few years ago. By using this unique model, the scientists have recently shown that Hypoxia-Inducible Factor-1 alpha (HIF-1alpha) is involved in mammalian tissue regeneration (Zhang Y. et al. “Drug-induced regeneration in adult mice”(2015) Sci. Transl. Med. DOI: 10.1126/scitranslmed.3010228).