Human Apoe3 and Apoe4 alleles have differential effects on mouse olfactory epithelium
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ABSTRACT: Alzheimer’s Disease (AD) is a progressive age-dependent disorder whose risk is determined in large part by genetic factors. We investigated the effects of human APOE3 and APOE4 alleles on the mouse olfactory epithelium.
Project description:The aim of the study was to investigate hepatic gene expression profiles differentially regulated by the APOE genotype in gene targeted replacement mice. The APOE4 genotype is associated with increased mortality in the elderly and is an independent risk factor for age-dependent chronic diseases. However, little is known about the underlying mechanisms and molecular targets involved in the APOE4-risk association. As APOE is centrally involved in lipid and cholesterol metabolism and in large part is produced in the liver, we analyzed hepatic RNA profiles of APOE4- and APOE3-expressing mice. 2 groups of 5 animals with 1 liver extract per animal. Mice were homozygous for a human APOE3 or APOE4 gene targeted replacement of the endogenous mouse Apoe gene (B6.129P2-Apoetm2(APOE*3)Mae N8 or B6.129P2-Apoetm3(APOE*4)Mae N8, Taconic Transgenic ModelsM-bM-^DM-", http://www.taconic.com/wmspage.cfm?parm1=2542), purchased at the age of 6-8 weeks, strain C57BL/6, 3 months old at the performance of the microarray, 6 weeks on a high-fat diet containing 41% energy from milk fat and 2 g/kg cholesterol.
Project description:The overall goal of our study is to understand the effect of HNE modification on the structure and function of apolipoprotein E3 (apoE3) and apoE4, which play a critical role in brain cholesterol homeostasis. Immunoblots indicated HNE modification of recombinant apoE3 and apoE4 with a major band at ~36 kDa, while LC-MS/MS analysis revealed modification of H140 and H299 in both, and additionally at C112 in apoE3.
Project description:The aim of the study was to investigate hepatic gene expression profiles differentially regulated by the APOE genotype in gene targeted replacement mice. The APOE4 genotype is associated with increased mortality in the elderly and is an independent risk factor for age-dependent chronic diseases. However, little is known about the underlying mechanisms and molecular targets involved in the APOE4-risk association. As APOE is centrally involved in lipid and cholesterol metabolism and in large part is produced in the liver, we analyzed hepatic RNA profiles of APOE4- and APOE3-expressing mice.
Project description:APOE4 genotype is the strongest risk factor for the pathogenesis of sporadic Alzheimer’s disease (AD), but the detailed molecular mechanism of APOE4-mediated synaptic impairment remains to be determined in human cellular context. In this study, we generated human astrocyte model carrying APOE3 or APOE4 genotype using human induced pluripotent stem cells (iPSCs), in which isogenic APOE4 iPSCs were genome-edited from healthy control APOE3 iPSCs. By transcriptome analysis of human astrocytes between APOE genotypes, we showed the upregulation of an extracellular matrix glycoprotein in human APOE4 astrocytes, which may cause synaptic degeneration in concert with the equivocal reactive character and lipid change. Together, these results demonstrate novel negative impact of human APOE4 astrocyte on synaptic integrity and lead to a promising therapeutic intervention into APOE4-carriers.
Project description:Despite strong evidence supporting the involvement of both apolipoprotein E4 (APOE4) and microglia in Alzheimer’s Disease (AD) pathogenesis, the effects of microglia on neuronal APOE4-driven AD pathogenesis remain elusive. Here, we examined such effects utilizing microglial depletion in a chimeric model with human neurons in mouse hippocampus. Specifically, we transplanted homozygous APOE4, isogenic APOE3, and APOE-knockout (APOE-KO) induced pluripotent stem cell (iPSC)-derived human neurons into the hippocampus of human APOE3 or APOE4 knock-in mice, and depleted microglia in half the chimeric mice. We found that both neuronal APOE and microglial presence were important for the formation of Aβ and tau pathologies in an APOE isoform-dependent manner (APOE4 > APOE3). Single-cell RNA-sequencing analysis identified two pro-inflammatory microglial subtypes with high MHC-II gene expression that are enriched in chimeric mice with human APOE4 neuron transplants. These findings highlight the concerted roles of neuronal APOE, especially APOE4, and microglia in AD pathogenesis.
Project description:Laser capture microdissected choroid plexuses were obtained and expression arrays were generated to investigate gene expression in ApoE-Knockin choroid plexuses; the choroid plexus forms the cerebrospinal fluid, the cerebrospinal fliod barrier, functions as the major gateway for blood-born leukocytes to enter the brain in degenerative and inflammatory brain diseases, and the principal neuroimmune interface in the brain. We found lipid deposits in the aged choroid plexus of hyperlipidemic ApoE4-Knockin mice but none in normolipidemic ApoE4-Knockin or normolipidemic or hyperlipidemic ApoE3-Knockin control choroid plexuses. Here, we studied the functional impact and gene epressions these choroid plexuses.
Project description:Recent findings suggest that the human APOE epsilon 4 allele protects against non-alcoholic fatty liver disease, while APOE epsilon 3 promotes hepatic steatosis and steatohepatitis. We performed an untargeted proteome analysis of the liver and identified a great number of proteins differently expressed in obese APOE3 and APOE4 mice. The majority of the proteins up-regulated in APOE3 can be grouped to inflammation and damage-associated response, cytoskeleton and lipid storage. In contrast, those proteins that are up-regulated in APOE4 can be related to intermediate filament modifications, biotransformation and amino acid metabolism. Results of the targeted quantitative RT-PCR and Western blot experiments contribute to the overall finding that APOE3 promotes hepatic steatosis, inflammatory- and damage-associated response signaling and fibrosis in the liver of obese mice. One of the proteins that were up-regulated in obese as well as lean APOE4 compared to APOE3 mice is parvulin 14 (Pin4). Up-regulation of parvulin 14 may be involved in the protection against fatty liver disease evident in the presence of APOE4.
Project description:The development of treatment for Alzheimer’s Disease (AD) is hindered by a limited understanding of its structural basis. Apolipoprotein E (APOE) ε4 genotype is the most important risk factor for late-onset AD. APOE4 differs from the APOE3 isoform by a single mutation, C112R. Here, we employ crystallography, biophysical methods and computer simulations to dissect the “domino-like” effect of C112R substitution on APOE4 behaviour. We found that the mutation induces long-distance (>15 Å) conformational changes leading to geometrically distinct T-shaped dimeric unit of APOE4 compared to APOE3. By mutagenesis, we demonstrate that the APOE4 unit is more prone to aggregation than that of the APOE3. AD drug candidate tramiprosate and metabolite 3-sulfopropanoic acid induce APOE3-like conformational behaviour in APOE4 and suppress its aggregation propensity. Omics analysis of APOE ε4/ε4 cerebral organoids treated with tramiprosate revealed its effect on cholesteryl esters, the storage product of excess cholesterol. Our results connect the APOE4 structure with its aggregation propensity, which can be further exploited in drug development for neurodegeneration and ageing.