Digging up the developmental origins of adaptive physiological plasticity in hypoxia-tolerant mammals

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Vertebrates rely on continuous oxygen (O2) delivery for aerobic energy production; however, there are terrestrial environments in which O2 availability is limited (e.g., high altitude, underground burrows). Limited O2 availability (i.e., hypoxia) impairs  cellular energy production, and ultimately, survival. Despite these challenges, animals have successfully populated terrestrial hypoxic niches. The key to tolerating hypoxia is matching metabolic demand to reduced energy supply, and vertebrates have evolved a range of adaptive strategies that contribute to this balance. In the most hypoxia-tolerant species, metabolic rate supression is the primary adaptive response to hypoxia. However, despite the importance of energetic homeostasis to survival and the severe limitations that hypoxia imposes on energy production, we do not have a good understanding of the cellular mechanisms that mediate metabolic rate suppression in any hypoxia-tolerant species, or the evolutionary origins of these traits. My goal is to understand how hypoxia-tolerant mammals maintain energetic homeostasis during fluctuations in environmental O2 levels. The research proposed in the present application will build upon recent progress by my laboratory towards this objective by providing new information about 1) physiological adaptations to hypoxia, 2) molecular mechanisms that underlie these adaptations, and 3) the evolution of hypoxia-tolerance at the physiological and molecular levels. We will use the Krogh Principle to address our questions in an evolutionary and developmental context and build upon our recent progress by contrasting physiological and molecular responses to hypoxia between hypoxia-tolerant and -intolerant mammals. Our primary study species include the naked mole-rat, which is arguably the mammalian champion of hypoxia-tolerance and thus an ideal model in which to investigate our research questions, and also moderately hypoxia-tolerant cousin species (Damaraland and Giant Zambian mole-rats), and hypoxia-intolerant mice and rats. We will investigate the following SHORT-TERM OBJECTIVES/QUESTIONS: 1.Which central nervous system signalling mechanisms control physiological adaptations to hypoxia throughout development in African mole-rats? 2.How does mitochondrial plasticity impact systemic energetics in hypoxia-tolerant mammals? 3.What underlies beneficial reactive oxygen species (ROS) management in hypoxia-tolerant mammals? This research will fundamentally advance the field by revealing the evolution of mechanisms that beneficially modulate physiological and cellular energetics to achieve metabolic homeostasis and organismal survival in hypoxia. We will answer important basic research questions regarding the evolution of hypoxia-tolerance in a developmental context. We may also inform translation studies in biomedical fields focused on achieving cytoprotection in hypoxia (e.g., heart attack/stroke).