Applying Epigenetics to Alzheimer's Disease via the Latent Early–life Associated Regulation (LEARn) Model
Alzheimer's disease (AD) is a leading cause of aging related dementia and has been extensively studied by several groups around the world. A general consensus, based on neuropathology, genetics and cellular and animal models, is that the 4 kDa amyloid β protein (A&bgr) triggers a toxic cascade that induces microtubule–associated protein τ (MAPT) hyperphosphorylation and deposition. Together, these lesions lead to neuronal dysfunction and neurodegeneration, modeled in animals, that ultimately causes dementia. Genetic studies show that a simple duplication of the Aβ precursor (APP) gene, as occurs in Down syndrome (trisomy 21), with a 1.5–fold increase in expression, can cause dementia with the complete AD associated neuropathology. The most fully characterized form of AD is early onset familial AD (FAD). Unfortunately, by far the most common form of AD is late onset AD (LOAD). FAD has well–identified autosomally dominant genetic causes, absent in LOAD. It is reasonable to hypothesize that environmental influences play a much stronger role in etiology of LOAD than of FAD. Since AD pathology in LOAD closely resembles FAD with accumulation of both Aβ and MAPT, it is likely that the environmental factors foster accumulation of these proteins in a manner similar to FAD mutations. Therefore, it is important to identify environmentally driven changes that “phenocopy” FAD in order to find ways to prevent LOAD. Epigenetic changes in expression are complex but stable determinants of many complex traits. Some aspects are regulated by prenatal and early post–natal development, others punctuate specific periods of maturation, and still others occur throughout life, mediating predictable changes that take place during various developmental stages. Environmental agents such as mercury, lead, and pesticides can disrupt the natural epigenetic program and lead to developmental deficits, mental retardation, feminization, and other complex syndromes. In this review we discuss latent early– life associated regulation (LEARn), where apparently temporary changes, induced by environmental agents, become latent and present themselves again at maturity or senescence to increase production of Aβ that may cause AD. The model provides us with a novel direction for identifying potentially harmful agents that may induce neurodegeneration and dementia later in life and provides hope that we may be able to prevent age–related neurodegenerative disease by “detoxifying” our environment.
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Document Type: Research Article
Affiliations: Laboratory of Molecular Neurogenetics, Departments of Psychiatry Indiana University School of Medicine, 791 Union Drive, Indianapolis, IN 46202.
Publication date: June 1, 2012
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- Current Alzheimer Research publishes peer-reviewed frontier review and research articles on all areas of Alzheimer's disease. This multidisciplinary journal will help in understanding the neurobiology, genetics, pathogenesis, and treatment strategies of Alzheimer's disease. The journal publishes objective reviews written by experts and leaders actively engaged in research using cellular, molecular, and animal models. The journal also covers original articles on recent research in fast emerging areas of molecular diagnostics, brain imaging, drug development and discovery, and clinical aspects of Alzheimer's disease. Manuscripts are encouraged that relate to the synergistic mechanism of Alzheimer's disease with other dementia and neurodegenerative disorders. Book reviews, meeting reports and letters-to-the-editor are also published. The journal is essential reading for researchers, educators and physicians with interest in age-related dementia and Alzheimer's disease. Current Alzheimer Research provides a comprehensive 'bird's-eye view' of the current state of Alzheimer's research for neuroscientists, clinicians, health science planners, granting, caregivers and families of this devastating disease.
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