Project Summary / Abstract Alzheimer's disease (AD) is the most common cause of human dementia that progressively worsens with age. Sporadic late-onset AD accounts for more than 90 percent of Alzheimer’s cases without clear documented familial history of the disease. However, the vast majority of existing transgenic and knock-in models incorporate disease-causing familial mutations in one or more genes associated with dementias, representing a major limitation. The RFA-AG-21-003 [New/Unconventional Animal Models of Alzheimer’s Disease] highlights the need to develop and characterize naturally occurring “non-murine models of AD that may represent improved translational potential by better replicating pathological features of the human disease”. We respond to the RFA to apply single cell epigenomic and transcriptomic technologies developed by our team to create cell-type- specific epigenome and transcriptome maps in frontal cortex and hippocampus that are associated with AD-like pathogenesis in two naturally occurring AD animal models: Octodon degus and Canis familiaris. These animals show age-dependent neuropathology and cognitive impairment similar to those observed in human AD, thus they are natural AD models. As both degus and mice are rodents, the studies of long-lived degus will be particularly valuable for a within-mammalian order comparison of which AD gene regulatory pathways are common to spontaneous AD-like features in degus versus different transgenic mouse models. While we generate the resources in alignment with the RFA goals, the proposed research will allow us to develop a comparative analysis to determine conserved epigenetic alterations in the unconventional animal models and bridge our existing databases of mouse models and humans. Maladaptive changes in accessible chromatin accessibility, chromatin organization and gene expression in disease relevant cell types will reveal species- specific and cross-species conserved mechanisms of AD pathogenesis, as well as new targets for AD prevention and treatment. This will provide new insights into the mechanisms of AD pathogenesis in humans. In addition to genome data sharing at the designated NIH depository, resources will be shared and curated at our UCI Center for Neural Circuit Mapping.