PROJECT SUMMARY Pregnancies at high altitude (>2500m) are 3-4 times more likely to involve complications (fetal growth restriction, pre-eclampsia, etc.), which have long-term repercussions on maternal and infant health. However, indigenous Andeans and Tibetans, who are native to high altitude, do not experience an elevated risk for these complications at altitude. Understanding the underlying physiological mechanisms that protect fetal development and maternal health in altitude-adapted populations could lead to clinical interventions or preventative treatments to protect women at altitude during pregnancy. However, limited progress has been made on this front because pregnancy is both ethically and logistically challenging to study in humans. We propose to use an emerging model system for altitude adaptation, the deer mouse (Peromyscus maniculatus), to answer these fundamental questions about pregnancy progression and health. As in humans, highland deer mice display reproductive adaptations to altitude whereas lowland counterparts experience elevated offspring mortality under simulated altitude. We will combine functional genomic analysis of placenta tissue at three critical gestational time-points with histology and morphological measures of placental and fetal development to generate the most comprehensive analysis of placentation and placental function under simulated hypoxia to-date. We will use a comparative physiology approach by comparing normoxia- and hypoxia-exposed deer mice from lowland and highland sites at these timepoints to outbred laboratory mouse strains under the same conditions to identify both adaptive response to hypoxia that protect highland placentation and conserved, placental responses to hypoxia that underly pathology. First, we will quantify HH-dependent plasticity in placental development and structure in altitude-adapted and non-adapted deer mouse populations using histological approaches. These data will allow us to evaluate whether plasticity in a given placenta trait is likely to be adaptive or maladaptive. Second, we will generate transcriptomes (via RNAseq) and methylomes (via reduced representation bisulfite sequencing [RRBS]) from each of the two major functional layers of the placenta and use analytical approaches from functional genomics to understand how regulation of gene expression underlies placental phenotypes. Together, these analyses will help us to understand how genes undergoing selection in altitude-adapted populations contribute to regulation and structure of gene networks underlying placentation. The proposed aims will produce major advances in understanding how the placenta develops and affects fetal health, and they will provide new directions for medical intervention by identifying pathways that evolution has adaptively altered. The proposed project will support student exposure to cutting-edge biomedical research while strengthening the research environment through new technique establishment...