Iliya Lefterov - US grants

DESCRIPTION (provided by applicant): This application is a resubmission in response to PAR-03-056 and particularly to Research topic 3. Druq Discovery for Coqnitive Decline and Alzheimer's Disease. Cholesterol (CL) is considered one of the main players in the pathogenesis of Alzheimer's disease (AD). It has been shown that accumulation of excess CL in hippocampal neurons increased Abeta production. Furthermore, prevalence of AD is reduced among people taking statins - CL lowering drugs. In contrast, plasma levels of HDL-cholesterol (HDL-CL) are inversely associated with risk of cardiovascular disease and AD. Understanding the mechanisms through which CL homeostasis affects APP processing and amyloid deposition will provide clues for better understanding the risk factors, prevention and treatment of AD. Liver X receptors (LXRalpha and beta) act as molecular sensors of cholesterol levels and respond by inducing processes that reduce cholesterol levels. The ABCA1 transporter which is under the transcriptional control of LXRs, mediates CL efflux and secretion of excess CL from cells to lipid-flee Apo-lipoproteins. It is considered a major determinant of plasma HDL concentration. We found that LXR/RXR agonists treatment of primary neurons increased ABCA1 expression and CL effiux to apolipoproteins A-I and E3, consequently decreasing CL content in these cells. More importantly, we demonstrated that these ligands alone or in combination with apolipoprotein A-I caused a substantial reduction in the stability of APP Cterminal fragments and decreased Abeta production. We hypothesize that transcriptional upregulation of ABCA1 triggered by pharmacological activation of LXR will affect the amyloidogenic processing of APP, with a decreased Abeta secretion and ultimately decreased amyloid deposition in the brain of AD model animals. To test our hypothesis we propose: Aim 1. To examine the role of LXR ligands and apolipoprotein-mediated cholesterol efllux on APP intracellular transport and Abeta generation. In cells stably expressing APPsw we will determine if LXR ligand treatment with or without apolipoproteins affects APP and BACE 1 vesicular transport from Golgi to plasma membrane and their endocytosis. To determine if the effect of LXR in neurons requires transcriptional upregulation of endogenous ABCA1, we will apply the same LXR ligand treatments in primary neuronal cultures derived from ABCA1wt and ABCA1-/- mice. Aim 2. To determine the effect of LXR synthetic pharmacological ligands on Aa generation and amyloid deposition in APP transgenic mice. By using APP23 mice we will test the critical question whether in-vivo administration of synthetic LXR agonists T0901317 and Hypocholamide, and the transcriptional activation of ABCA1 modulates Aa generation/secretion or the amount of Abeta deposits in the brain of AD transgenic model. The results of our study will advance the understanding how genes and proteins controlling intracellular CL content and its redistribution in the brain influence hAPP processing and Abeta deposition. We believe that the pharmacological manipulation of these regulatory mechanisms will validate LXRs as a valuable molecular target in the drug development and discovery of new therapeutic agents for prevention or treatment of Alzheimer's disease.

[unreadable] DESCRIPTION (provided by applicant): Studies have now revealed that Alzheimer's disease (AD) patients have more severe atherosclerosis than age-matched controls without AD, and established a positive correlation between the degree of atherosclerotic disease of cerebral arteries in AD patients and neuropathological features typical for AD. However, mechanisms by which cholesterol (CL) metabolism influences AD pathogenesis remain uncertain. CL efflux and generation of HDL are mediated by ABCA1 membrane transporter which is transcriptionally controlled by Liver X nuclear Receptors (LXR). ABCA1 mutations cause severe HDL deficiencies, like hypoalphalipoproteinemia and Tangier Disease (TD). A major goal of our research is to reveal the role of ABCA1 in the molecular pathogenesis of AD and thus to explore and to test new therapeutic strategies. The central hypothesis is that ABCA1 affects ABeta formation/deposition and clearance. In support are our studies (currently in press) funded by NIA R21 and R03 awards, showing that ABCA1 deficiency in APP23 mice leads to a dramatic decrease of soluble apoE and an increased deposition of ABeta in the brain. We have also demonstrated that application of the synthetic LXR ligand T0901317 (TO) in vivo increases the expression of ABCA1 in CNS and decreases the amounts of ABeta species in the brain. We found that primary cells from TD patients generate and secrete more ABeta and that their response to LXR synthetic ligands is different and depend on the type of ABCA1 mutation. Importantly, one of the primary ABCA1 mutant cell lines with a point mutation causing N935S amino acid substitution was established from a TD patient with dementia and abundant amyloid deposits in the brain, but without cardiovascular pathology. Thus, specific mutations in ABCA1 differentially disturb its regulatory role on beta-amyloid deposition and atherosclerosis, and therefore we hypothesize that ABCA1 mutations determine the clinical phenotype observed in patients by at least partly different mechanisms. The goal of this NIA pilot grant is to develop and characterize a mouse line that expresses mutated ABCA1N935S. Aim 1. To create genetically engineered mice that express mutated ABCA1N935S. This mouse line will be created by utilizing a "Knock-in" approach to introduce an N935S mutation in the ABCA1 locus in mouse ES cells. These ABCA1S/S mice will ubiquitously express ABCA1N935S, the mutated gene will remain under the endogenous ABCA1 transcriptional control and the mutant protein will replace wild type ABCA1. Aim 2. To characterize ABCA1N935S knock-in mice. We will analyze in vivo the expression of ABCA1N935s and its function as a cholesterol transporter by measuring plasma CL and lipoproteins. The effect of the mutated ABCA1N93ss on brain lipoproteins and endogenous APR processing and ABeta generation in vivo will be determined as a preliminary step to substantiate future detailed biochemical studies. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Despite the enormous efforts in academia and in pharmaceutical industry, Ab vaccination, y- and b-secretase inhibitors are still far from clinical use. Drugs that ameliorate AD phenotypes by interfering cholesterol metabolism have been also suggested, but the rationale for using those is poorly defined and in all of the cases the molecular mechanisms which account for their beneficial effects are poorly understood. Therefore there remains a great need for other strategies of lowering Ab. Nuclear Liver X receptors (LXRa and LXRb) are transcription factors that control the expression of genes involved in cholesterol metabolism. We have found that activated LXR regulate metabolic pathways of brain cholesterol intra- and extracellular transport that influence APP processing, b-amyloid deposition and its clearance from brain. Moreover, we and others have shown, that treatments of neuronal cell lines and primary neurons with natural or synthetic LXR ligands decrease Ab secretion, and that in vivo treatment of young AD model mice with a synthetic LXR ligand, increased the expression of LXR responsive genes in CNS and decreased soluble b-amyloid levels in their brains. We have also found that the application of LXR ligands inhibited secretion of inflammatory cytokines and increased neuronal survival following Ab or LPS treatment. The ultimate beneficial outcome of LXR ligand treatment on AD phenotype in vivo is a combination of effects mediated by genes expressed in neurons and astrocytes influencing Ab generation, b-amyloid formation and clearance, and by genes expressed in microglia which are tightly related to both - Ab clearance and inflammation. The data therefore substantiate the design of a drug discovery study for identification of LXR activators/agonists and their systematic evaluation in well established in vitro and in vivo model systems. In Specific aim 1, the activated status of LXR will be evaluated by their ability to increase dramatically the transcription of ABCA1 - a major LXR response gene. Thus, the increased amount of ABCA1 mRNA following in vitro application of a given compound (altogether >50,000 for screening) will serve as a reporter for LXR activation. Compounds that meet the criteria for LXR activation will be further screened for their ability to reduce Ab production in vitro. "Hits" with dual stimulatory effect on ABCA1 expression and apoE secretion, ability to reduce Ab and to facilitate cholesterol efflux will be further characterized in LXR knockout cell based assays. In addition, potent compounds will be characterized for their inhibitory effects on cytokine expression and regulatory effects on transcriptional activity of genes with undesired effects on fatty acids and triglyceride synthesis. In Specific Aim 2, the two most potent compounds will be chosen for initial in vivo tests in PS1APP transgenic mice. PUBLIC HEALTH RELEVANCE: Despite the enormous efforts in academia and in pharmaceutical industry, drugs based on the recent progress in our understanding for Alzheimer disease are still not available for clinical use. Brain cholesterol metabolism and its relation to different aspects of the disease pathogenesis substantiates the development of new therapeutic approaches based on complex regulatory networks controlled by transcription factors and their responsive genes. We are proposing a drug screening approach for identification of natural or synthetic compounds that activate transcription factors called Nuclear Liver X receptors (LXRa and LXRb) and therefore lead to upregulation and increased expression of genes involved in cholesterol metabolism. This drug discovery study is based on data generated in our and other laboratories which confirm that LXR controlled cholesterol transporters and lipoproteins in brain are involved in b-amyloid aggregation, deposition and clearance. Therefore, LXR activators can be used for lowering Ab inhibition of inflammation and improvement of behavioral deficits.

DESCRIPTION (provided by applicant): The underlying quantitative variation in susceptibility to develop Alzheimer's disease (AD) is controlled by multiple genes, environmental factors, and metabolic signals. Importantly, some metabolic stimuli, like hypercholesterolemia, obesity, hyperinsulinemia and insulin resistance, follow certain dietary patterns and lifestyle, and are associated with increased risk of dementia and AD at advanced age. The detrimental effects of high fat diet (HFD) on cognitive performance and exacerbation of cerebral amyloidosis and amyloid angiopathy has been recently demonstrated in an animal model of AD. Equally important, exposure to some toxic environmental factors, such as drinking water arsenic (As), induces changes that are indistinguishable from, or coincide with pathological and clinical features of AD including: induced tau hyperphosphorylation, upregulation of amyloid precursor protein (APP); increased cardiovascular disease; enhanced brain inflammatory reactions, hyperinsulinemia in mice, and cognitive and memory deficits. It is completely unknown, however, whether HFD and environmental exposures combine to increase AD risk and disease progression. Emerging research and novel findings of epigenetic reprogramming inflicted by dietary agents or As exposure strongly suggest that induced changes in histone marks are retained throughout the life and accumulate to promote AD pathogenesis. Thus age dependent gene-environment interactions are critical for the development and progression of late onset AD (LOAD). It is therefore hypothesized that the combined impact of HFD and As on epigenetic chromatin modifications results in pathogenic tissue and organ-selective transcriptional activity that translates into increased risk of developing, accelerating or aggravating AD phenotypes. The objectives of the proposed research are: 1) In a well-established animal model for AD, to reveal organ specific changes in chromatin modifications in brain and liver, instigated by the collective effect of HFD and As exposure that produce genome wide pathogenic transcriptional activity, and 2) To reveal changes specific for AD phenotype (cognitive performance, amyloid deposition in brain parenchyma, metabolic abnormality and blood vessel wall remodeling) caused by combined exposures that result from identified changes in histone modifications. This goal will be achieved by accomplishing the following Specific Aims: Aim 1: To reveal the consequences of collective exposure to HFD and As on AD phenotype and lipid and glucose metabolism; and Aim 2: To assess changes in chromatin modifications in brain and liver induced by HFD and As in AD mice and to correlate specific changes in the epigenome to behavioral deficits and brain amyloidosis.

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) is the most common form of dementia with more than 5.5 million patients in the USA, a number that will quadruple by 2047. The disease can be characterized as an accelerated loss of cognitive functioning to such an extent that it interferes drastically with a person's daily life and activities. AD is a complex trait in that underlying quantitative variation in susceptibility is controlled by multiple genes and environmental factors. Importantly, some of these environmental and metabolic stimuli, like hypercholesterolemia, obesity, hyperinsulinemia and insulin resistance, which follow certain dietary patterns and lifestyle, are associated with increased risk of dementia and AD at advanced age, only if confronted in midlife. In this respect the epigenetic reprogramming by dietary agents, which change histone modifications and are retained throughout the life, should be considered highly relevant to AD pathogenesis, supporting the idea of age dependent gene-environment interactions as critical for the development and progression of late onset AD (LOAD). The metabolic pathways of cholesterol and phospholipid transport in the periphery and CNS, as well as some rate limiting steps of insulin secretion, are controlled by oxysterol-sensing transcription factors nuclear liver X receptors (LXRs) - LXR? and LXRß, through the expression level of their responsive genes. We hypothesize that in the context of AD the response to high fat diet (HFD) is mediated by epigenetic chromatin modification and LXR binding to DNA and is ultimately realized by tissue and organ-selective transcriptional activity. The goal of this proposal has two major aspects: Aim 1. Using second generation high throughput sequencing to assess changes in chromatin modifications induced by nutritional signals and their role in the development and progression of cognitive performance and AD pathology. Aim 2. To reveal genome-wide changes in LXR binding caused by HFD and thus to identify LXR targets whose transcriptional up- or down-regulation has a role in the development and progression of AD-like phenotype in model mice.

DESCRIPTION (provided by applicant): The only risk factor identified so far for sporadic late onset AD (LOAD) is aging. The inheritance of APOE?4 allele of apolipoprotein E is the major genetic risk factor for LOAD but molecular mechanisms underlying this susceptibility are unknown. It is possible that similar to other multifactorial (systemic) diseases, the underlying quantitative variation in susceptibility to develop LOAD is probably controlled by multiple genes. The role of environmental factors in the risk and pathogenesis of AD has been increasingly appreciated. In this regard, the research on epigenetic reprogramming inflicted by exposure to environmental factors, strongly suggests that changes induced at certain chromatin marks during the development and postnatal life can influence development of dementia and AD progression. We are proposing investigation in animal models to advance the understanding of the role of environmental arsenic (As) exposure in the etiology and progression of AD. We capitalize on the results generated with the support of our ongoing NIEHS R21: 1) exposure of adult mice, with already developed AD phenotype, to human relevant As concentrations (100 ?g/ml) in drinking water further deteriorates their cognitive performance, increases amyloid plaques and reactive astrocytosis in hippocampus; the expression of nuclear liver X receptors (LXR) and important target genes, is decreased. 2) Young mice exposed to as are cognitively impaired and the expression level of and activity dependent transcription factor EGR1 (Early growth response 1), implicated in memory formation and cognitive performance is lower. 3) prenatal exposure to As and high fat diet (HFD) causes global hypoacetylation at Lysine 9 of histone 3 (H3K9) and alterations in acetylation pattern of genes, components of Polycomb Repressive Complexes PRC1 and PRC2, that modulate gene expression genome-wide through changes in histone modifications. We hypothesize that prenatal, perinatal and postnatal as exposure impairs cognitive reserve and inhibits adaptive capacity of the adult organism to environmental insults (e.g. HFD). The outcome is a predisposition to AD or aggravated existing AD phenotype, with the APOE genetic background significantly impacting the pathology. We are proposing that histone modifications, including those catalyzed by PRC2 and loss of essential transcriptional programs (e.g. LXR and EGR1) are molecular mechanisms underlying as effects. To test the hypothesis we will accomplish two Specific Aims: Aim 1. To elucidate the effects of as exposure on the development of AD-like phenotype in AD model mice. Aim 2: To identify epigenetic molecular mechanisms underlying changes in cognitive performance and AD phenotype in response to as exposure.

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) is the most common form of dementia with more than 5.5 million patients in the USA, a number that will quadruple by 2047. The disease can be characterized as an accelerated loss of cognitive functioning to such an extent that it interferes drastically with a person's daily life and activities. AD is a complex trait in that underlying quantitative variation in susceptibility is controlled by multiple genes and environmental factors. Importantly, some of these environmental and metabolic stimuli, like hypercholesterolemia, obesity, hyperinsulinemia and insulin resistance, which follow certain dietary patterns and lifestyle, are associated with increased risk of dementia and AD at advanced age, only if confronted in midlife. In this respect the epigenetic reprogramming by dietary agents, which change histone modifications and are retained throughout the life, should be considered highly relevant to AD pathogenesis, supporting the idea of age dependent gene-environment interactions as critical for the development and progression of late onset AD (LOAD). The metabolic pathways of cholesterol and phospholipid transport in the periphery and CNS, as well as some rate limiting steps of insulin secretion, are controlled by oxysterol-sensing transcription factors nuclear liver X receptors (LXRs) - LXR1 and LXR2, through the expression level of their responsive genes. We hypothesize that in the context of AD the response to high fat diet (HFD) is mediated by epigenetic chromatin modification and LXR binding to DNA and is ultimately realized by tissue and organ-selective transcriptional activity. The goal of this proposal has two major aspects: Aim 1. Using second generation high throughput sequencing to assess changes in chromatin modifications induced by nutritional signals and their role in the development and progression of cognitive performance and AD pathology. Aim 2. To reveal genome-wide changes in LXR binding caused by HFD and thus to identify LXR targets whose transcriptional up- or down-regulation has a role in the development and progression of AD-like phenotype in model mice.

APOE (Apolipoprotein E) is part of APOE/APOC gene cluster on chromosome 19 and codes for 3 protein isoforms ? APOE2, APOE3 and APOE4. APOE transports cholesterol and phospholipids in the periphery and brain1. APOE isoforms differ in their lipid and receptor binding capacity and their role is associated with clearance of LDL, VLDL and chylomicrons. The inheritance of APOE4 allele increases and APOE2 decreases the risk for late onset AD (LOAD), but the mechanism is poorly understood. While APOE is involved in critical cellular functions such as oxidative processes, inflammation, glial cell and neuronal homeostasis, none of those can be dissociated from isoform specific binding, transport and delivery of cholesterol and phospholipids to different cell types. Recent reports suggest there might be a differential APOE-isoform specific effect on microglia mediated phagocytosis and function of immune receptors expressed in brain16. Our preliminary data demonstrate APOE isoforms influence expression of immune receptors Dectin-1/Clec7a, Siglec1, Siglech, Oscar - involved in inflammatory response and phagocytosis. A strong support to an interconnected role for APOE and immune receptor mediated phagocytosis are our results of Multi-Dimensional Mass Spectrometry Shotgun Lipidomics of brain samples from AD patients, where we find significant differences in phospholipid molecular speciation in major phospholipid classes. We hypothesize the APOE isoform-specific effects on phagocytosis are driven by the different phospholipid composition of APOE lipid particles and/or by the differential effect of APOE isoforms on microglial transcriptome. We are proposing 3 Specific Aims to test the hypothesis: Aim 1. Determine age related APOE isoform-specific effect on molecular phospholipid profiling in brain: we will perform lipidomics assays on phospholipid content and molecular speciation of APOE2, APOE3 and APOE4 lipid particles in Astrocyte Conditioned Medium, Interstitial Fluid and brain parenchyma of WT and APP expressing mice with targeted APOE replacement at two ages, and in brain samples from nondemented control individuals and AD patients. Aim 2. Establish the role of APOE isoforms for immune receptor mediated Ab phagocytosis: we will determine if phospholipid molecular species part of native APOE particles secreted by astrocytes, or derived from brain Interstitial Fluid (ISF) differentially affect microglial/immune receptor mediated phagocytosis. Aim 3. In APOE targeted replacement mice to establish APOE isoform? and age?specific response to HFD and its impact on CNS transcriptome: The objectives are to perform behavioral, integrated transcriptomics, and co-expression network analysis on microglia from brain samples of WT and APP mice expressing human APOE isoforms.

Abstract: Alzheimer?s disease (AD) poses an enormous burden on society with no successful treatment or preventative strategy. The inheritance of APOE?4 allele is the most significant genetic risk factor for AD. There is inadequate understanding of the interaction of APOE4 with other risk factors, most importantly aging, inflammatory reactions and those involved in A? toxicity and clearance. We are increasingly beginning to understand age and AD pathology associated changes in the context of epigenome architecture and transcriptome in the brain. Implementing effectively this innovative and transforming knowledge about the interconnected role of aging, epigenome, genetic and environmental risk factors when studying AD will help define new therapeutic targets. The mission of the proposed meeting is to organize leading scientists with common interest in genetic/epigenetic, biochemical, physiological and medical expertise in APOE biology and interactions with other AD risks factors to encourage: exchange of ideas; establishing strong collaborations between early career scientists and graduate students; better education of clinicians involved in AD research and health care from Eastern European Countries of current leading research; and heighten the awareness of AD as a global health problem. The meeting, with participants from 15 countries, will be branded as an Alzheimer?s Association Meeting, which supports the development of the next generation of researchers including those from underrepresented populations and highly values trainee development and diversity. Eastern European countries provide a unique location where there is inadequate diagnostic approaches and low level of awareness of AD, including among professionals, and societal and cultural stigmas. Thus we are looking at the meeting as an opportunity to promote networking between participating AD investigators, trainees and their respective institutions from USA, Western and Eastern European countries. This can be a first step to improve the accuracy of diagnosis, participation in scientific projects aiming at the design and development of rational therapy and finally to improve the health care provided to AD patients by clinicians and researchers in this region. The early planning for the 2017 Meeting in Varna has integrated a junior faculty/trainee podium presentations and interactive forum/social focused on career development for postdocs and trainee attendees. Special efforts have been made to encourage attendance by underrepresented minorities in science, including women from Eastern European Countries and Balkan Peninsula. Thus, the Alzheimer?s disease, Varna-2017 Meeting supports a variety of activities that are directly relevant to the scientific missions of the National Institutes of Health, NIA and the interest of public health.

APOE (Apolipoprotein E) is part of APOE/APOC gene cluster on chromosome 19 and codes for 3 protein isoforms ? APOE2, APOE3 and APOE4. APOE transports cholesterol and phospholipids in the periphery and brain. APOE isoforms differ in their lipid and receptor binding capacity and their role is associated with clearance of LDL, VLDL and chylomicrons. The inheritance of APOE4 allele increases and APOE2 decreases the risk for late onset AD (LOAD), but the mechanism is poorly understood. While APOE is involved in critical cellular functions such as oxidative processes, inflammation, glial cell and neuronal homeostasis, none of those can be dissociated from isoform specific binding, transport and delivery of cholesterol and phospholipids to different cell types. Recent reports suggest there might be a differential APOE-isoform specific effect on microglia mediated phagocytosis and function of immune receptors expressed in brain. Our preliminary data demonstrate APOE isoforms influence expression of immune receptors Dectin-1/Clec7a, Siglec1, Siglech, Oscar - involved in inflammatory response and phagocytosis. A strong support to an interconnected role for APOE and immune receptor mediated phagocytosis are our results of Multi-Dimensional Mass Spectrometry Shotgun Lipidomics of brain samples from AD patients, where we find significant differences in phospholipid molecular speciation in major phospholipid classes. We hypothesize the APOE isoform-specific effects on phagocytosis are driven by the different phospholipid composition of APOE lipid particles and/or by the differential effect of APOE isoforms on microglial transcriptome. We are proposing 3 Specific Aims to test the hypothesis: Aim 1. Establish isoform- dependent effect of APOE?2 allele on brain parenchymal and mitochondrial lipidome and transcriptome in AD patients and non-demented controls. The goal is to integrate lipid and transcriptional profiles and to reveal APOE allele controlled phenotypes and lipid molecular species for additional functional assays in SA3. Aim 2. Determine isoform- and age-dependent effect of APOE genotype on brain lipidome and transcriptome in mice expressing human APOE2, APOE3 or APOE4 isoforms. We will determine phospholipid content of native APOE in Astrocyte Conditioned media, lipid particles in brain interstitial fluid (ISF) and differences in brain parenchyma and mitochondrial lipidomes between mice expressing APOE2, APOE3 or APOE4 isoforms at 2 different ages. Aim 3. To test the effect of APOE-containing nanoparticles on A? phagocytosis in vitro and in vivo. The goals are to apply the knowledge about differences in lipid compositions of AD and mouse brains and to test the effect of phospholipid molecular species on microglia mediated A? phagocytosis and clearance of A? oligomeric species in in vitro and in vivo experimental systems.

The inheritance of APOE?4 allele is the strongest genetic risk factor for late onset Alzheimer?s disease (LOAD). In fact, the inheritance of APOE?4 allele is the strongest known genetic risk factor in human pathology, but the mechanism is poorly understood. In contrast, APOE?2 allele is protective for AD and age-related diseases AD. While APOE has been associated with critical cellular functions such as oxidative processes, in?ammation, glial cell and neuronal homeostasis, none of those can be dissociated from binding, transport and delivery of choles- terol and phospholipids to di?erent cell types by APOE containing lipoprotein particles. It is also uniformly ac- cepted that the above functions are APOE-isoform speci?c. Our preliminary data demonstrates that phospholipid composition of APOE?3/3 and APOE?4/4 AD brain differs significantly. Most prominent were changes in lipid classes that are critical in regulation of normal mitochondrial function and dynamics, but also in execution of metabolic cascades part of regulated intracellular protein degradation known as autophagy and mitophagy. We also found significant APOE isoform-specific differences between the transcriptomic profiles of the AD samples that substantiate molecular explanation of specific AD pathological changes in brain, based on perturbed gene expression. Our preliminary data also demonstrates that there is a significant difference in the phospholipid content of native APOE2, APOE3- and APOE4- lipoproteins suggesting that that they may affect differentially surface immune receptors and initiate different signal transduction cascades. We hypothesize that the APOE isoform-speci?c e?ects on phenotype are driven by the di?erent phospholipid composition of APOE lipid particles and/or by the di?erential e?ect of APOE isoforms on brain transcriptome and lipidome. In the First SA, we will establish the association of APOE alleles with AD brain transcriptome and lipidome and determine the allele specific impact on mitochondrial function and dynamics. We will use postmor- tem brain samples from AD patients and controls of different APOE genotypes to determine differences in tran- scriptomes and lipidomes within and between genotypes. We will generate and analyze correlated/co-expressed gene networks based on APOE allele associated differentially expressed genes and perform correlation analyses to identify associations between genes and lipids in brain. In the Second SA, we will investigate APOE isoform- dependent epigenetic and transcriptomic changes in AD brain and APOE Targeted Replacement mice. We will determine the enrichment of histone marks in specific cell types isolated from human AD and control brains and will examine APOE allele specific correlations to gene expression profiles. Next, we will examine the effect of aging on epigenome and transcriptome in distinct brain cell types of human APOE TR mice. In the Third SA, we will determine how APOE2 lipoproteins counteract the acute deleterious effects of A?. The goals are to examine the effect of APOE2, E3 and E4 lipoproteins on: transcriptome of distinct brain cell populations and cognition in mice following intracranial injection of A??