Decoding the metabolic requirements for vertebrate appendage regeneration

SUMMARY In contrast to humans, some animals are able to scarlessly heal and regrow lost appendages after major injury. Appendage regeneration requires rapid and carefully regulated cell proliferation to replace lost tissue, an inherently anabolic process. Despite the fundamental need for biosynthesis as part of regenerative healing, we lack a mechanistic understanding of how injury is coupled to metabolic changes that enable cell proliferation and growth. Re-creating the metabolic conditions that enable growth is critical to being able to foster regenerative success in organisms where it is normally limited, such as ourselves. In this proposal, we leverage two advantages to articulate the metabolic requirements for vertebrate appendage regeneration. The first is a suite of mechanistic insights from other highly proliferative cell types, which rely on aerobic glycolysis to convert glucose to glucose-6-phosphate, a versatile biosynthetic precursor for nucleotide and phospholipid production. Our preliminary data suggest that this is a shared strategy in appendage regeneration. The second is the unique context-specificity of appendage regeneration in Xenopus tadpoles, which is lost or gained on the basis of nutrient source, developmental stage, and appendage type. This context specificity gives us the opportunity to directly compare regenerative structures to their non-regenerative counterparts and to other non- regenerative structures, thereby defining the specific features of the metabolic landscape that enhance or limit regenerative outcome. In this proposal we will test the central hypothesis that regenerative success is dictated by the ability of tissues to rapidly remodel their metabolic landscape and funnel nutrients toward biosynthesis. We will test this hypothesis by first defining the metabolic paradigm that dominates in regenerative conditions: glycolysis, pentose phosphate pathway, or oxidative phosphorylation. We will then identify shared and context- specific features of metabolic reprogramming, contrasting the metabolic profile of regenerative structures and non-regenerative structures at different developmental stages of the Xenopus tadpole. We conclude by building a regulatory landscape of metabolism in regeneration, functionally testing candidate regulatory transcription factors, and defining how metabolic gene expression is partitioned or integrated between cell types.