Cellular and molecular determinants of amniote regenerative potentials. - A branch of the regenerative sciences looks to non-mammalian species with hyper-regenerative abilities for clues to improve human wound healing. However, this approach has struggled to (1) select appropriate model species for meaningful translation to humans and (2) identify specific, actionable molecular targets for manipulating regenerative capabilities. Lizards are the only adult amniotes and closest relatives of humans able to suppress fibrosis and regrow multiple tissue types following appendage amputation. This extraordinary process involves formation of specialized regenerative structures known as blastemas, collections of reprogrammed fibroblasts that differentiate into replacement tissues. Interestingly, not all lizard species are capable of appendage regrowth, distinguishing lizards as the only group of tetrapods to contain both regenerative and non-regenerative species. My lab has committed to studying singular lizard species that have evolved to lack tail regeneration capabilities as natural losses-of-function models toward understanding the fundamental requirements for blastema development. We hypothesized that losses of regenerative capabilities during lizard speciation are due to mutation accumulations within genetic regions responsible for regulating critical aspects of fibrosis suppression and/or blastema establishment. Consequently, we conducted inter-species hybridizations, phylogenomic sequencing, and CRISPR screens to successfully identify mutation signatures significantly associated with loss of blastema formation capabilities. These studies identified three candidate wound healing processes dysregulated in non-regenerative lizard species, and each of the independent yet synergistic projects proposed here investigates the roles of these processes in blastema formation. Project 1 focuses on immunomodulations of pro-inflammatory signals that result in fibrosis suppression. Project 2 investigates pro- regenerative programs that support stem cell survival, proliferation, and activation within wound environments. Project 3 focuses on the epigenetic changes that establish wound site proximodistal patterning essential for proper blastema formation. Successful completion of the proposed projects will meet our short-term goals of characterizing and correcting mutations affecting key wound healing processes in non-regenerative lizard species. The invaluable experience gained during the course of these projects will directly propel my lab toward fulfilling our longer-term goals of inducing nature’s first blastemas in naturally non-regenerative lizard species. My envisioned research program views these endeavors as “steppingstones” for bridging specific gaps in wound healing capabilities between lizards and mammals. A blueprint for supporting lizard-like healing capabilities will be applied to established models of non-regenerating mammalian injuries, such as proximal mouse digit amputations. Ultimately, these lines of research will be applied to forming blastemas in human patients, holding promise to limit painful scarring, support organized tissue growth, facilitate prosthesis attachment, and bring much-needed improvements to patient quality of life following amputation injuries.
