The Role of Menopause-Driven DNA Damage and Epigenetic Dysregulation in Alzheimer s Disease

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The Role of Menopause-Driven DNA Damage and Epigenetic Dysregulation in Alzheimer's Disease PROJECT SUMMARY Alzheimer's disease (AD) is the most common form of dementia worldwide, and 2 out of 3 patients are women. A central explanation for this higher prevalence is thought to be the fluctuations in sex hormones as women traverse menopause, prior to depletion of estrogen and progesterone in the post-menopause period. Menopause has been reported to cause changes in epigenetic modifications, including histone acetylation which we and others have shown to be important to prevent memory decline in AD models. We have also observed sex-specific differences in AD-related genes in the brain of aged 3xTg-AD mice. Surprisingly little is known about the effects of the menopausal transition on epigenetic mechanisms in the brain. Important, aging is strongly associated with dysregulation of DNA damage repair, a process that has also been linked to menopause. Our preliminary data analyzing some 300 human brains show that DNA Single Strand Break (SSB) repair enzymes are dysregulated with age. We hypothesize that beyond its effects on reproductive stages in females, the menopause transition modulates DNA damage response (DDR) and epigenetic mechanisms. This results in the biological differences observed between female and male AD patients' mind and body. Existing AD models studying menopause use ovariectomized mice, resulting in an abrupt termination of circulating estrogen. We believe this is not representative of the menopause transition in women, in which peri-menopausal hormonal fluctuations can last years. We have successfully implemented accelerated ovarian failure (AOF) in mice to mimic human menopause. Here, using both the 3xTg-AD and 5xFAD mice under AOF, we will assess the effects of peri- and post-menopause-like stages on DNA SSB, the epigenetic landscape and the subsequent impact on the transcriptome and metabolic homeostasis in brain and blood in the context of AD. We developed a method to map Single-Strand DNA breaks at Nucleotide Genome Level resolution (SSiNGLe) that allows high-resolution analysis of DNA SSBs to determine the “Breakome age” of individuals, a potential novel biomarker of aging. We will build network models (associating SSBs with transcriptome alterations) to better understand how menopause-driven defects in DNA repair impact on known AD and Aging pathways. We will verify pathway observations using our human brain and AD case-control blood transcriptomics data (and public domain data) and identify which significant networks match to drug-signatures and/or any druggable targets. Completion of the work proposed will enhance our understanding of the role that menopause-induced DNA damage plays in both aging and AD. Specifically, we will: (1) elucidate the spatiotemporal relationship between DNA SSBs, DNA methylation, and neurotrophic gene transcription in the brain during the menopause transition, (2) define a timeline for the critical therapeutic window prior to the post-menopause stage where memory deficits are observed, and (3) discover connections between menopause-associated DNA SSB in the brain and in peripheral lymphocytes that can be used as biomarkers in future clinical studies for aging and AD research.