Cited by 524Alzheimer's disease research and treatmentsNeuroinflammation and Neurodegeneration MechanismsBarrier Structure and Function Studies

Profile and Regulation of Apolipoprotein E (ApoE) Expression in the CNS in Mice with Targeting of Green Fluorescent Protein Gene to the ApoE Locus

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Xu, Qin, Bernardo, Aubrey, Walker, David, Kanegawa, Tiffany, Mahley, Robert W., Huang, Yadong·2006·The Journal of Neuroscience

Abstract

To study the profile and regulation of apolipoprotein E (apoE) expression in the CNS, we generated mice in which apoE expression can be detected in vivo with unprecedented sensitivity and resolution. cDNA encoding enhanced green fluorescent protein (EGFP) with a stop codon was inserted by gene targeting into the apoE gene locus (EGFP apoE ) immediately after the translation initiation site. Insertion of EGFP into one apoE allele provides a real-time location marker of apoE expression in vivo ; the remaining allele is sufficient to maintain normal cellular physiology. In heterozygous EGFP apoE mice, EGFP was highly expressed in hepatocytes and peritoneal macrophages. EGFP was also expressed in brain astrocytes; however some astrocytes (∼25%) expressed no EGFP, suggesting that a subset of these cells does not express apoE. EGFP was expressed in <10% of microglia after kainic acid treatment, suggesting that microglia are not a major source of brain apoE. Although hippocampal neurons did not express EGFP under normal conditions, kainic acid treatment induced intense expression of EGFP in injured neurons, demonstrating apoE expression in neurons in response to excitotoxic injury. The neuronal expression was confirmed by in situ hybridization of mouse apoE mRNA and by anti-apoE immunostaining. Smooth muscle cells of large blood vessels and cells surrounding small vessels in the CNS also strongly expressed EGFP, as did cells in the choroid plexus. EGFP apoE reporter mice will be useful for studying the regulation of apoE expression in the CNS and might provide insights into the diverse mechanisms of apoE4-related neurodegeneration.

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Crossref · 10.1523/jneurosci.5476-05.2006

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109 of 109 references verified0 citation errors · 0 not checkable

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  • APOE is a soluble factor expressed by many cell types.

    “Insight into APOE4-mediated pathogenesis is complicated by the fact that APOE is a soluble factor expressed by many cell types12,13.”
  • Astrocytes synthesize most of CNS ApoE.

    “Because astrocytes synthesize most of CNS ApoE and were the cell type most affected by the global E4 to E2 transition, we generated APOE4s2loxP/loxP/Aldh1l1-CreERT2 APOE switch mice (APOE4s2A) that would express APOE4 in all CNS cell types except for astrocytes, which would selectively transition to APOE2 upon TAM injection29,30 (Fig. 4a).”
  • APOE is mainly secreted by astrocytes but is also expressed in microglia, neurons, and oligodendrocytes, particularly under injury and degenerative conditions.

    “Although mainly secreted by astrocytes, APOE is also expressed in microglia, neurons, and oligodendrocytes, particularly under injury and degenerative conditions. 2 , 13”
  • In the central nervous system, APOE is produced predominantly by astrocytes, although it can also be produced by reactive microglia and, to a lesser extent, stressed neurons and other glial cells.

    “In the CNS, APOE is produced predominantly by astrocytes, although it can also be produced by reactive microglia and, to a lesser extent, stressed neurons and other glial cells96,97.”

    From Multifaceted roles of APOE in Alzheimer disease (2024) · cites this paper as [96]

  • APOE expression is markedly upregulated by reactive microglia in the brains of individuals with AD.

    “its expression is markedly upregulated by reactive microglia in the brains of individuals with AD96,150.”

    From Multifaceted roles of APOE in Alzheimer disease (2024) · cites this paper as [96]

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Authors
Xu, Q., Bernardo, A., Walker, D., Kanegawa, T., Mahley, R. W., & Huang, Y.
Affiliations
Gladstone Institutes (US)
Venue
The Journal of Neuroscience
Published
2006-05-10
Volume
26
Issue
19
Pages
4985-4994
ISSN
  • 0270-6474 (ISSN-L)
  • 1529-2401
OpenAlex
W1974878596
Cited by
524
References
109
Citations by year
2026: 28 · 2025: 43 · 2024: 40 · 2023: 33 · 2022: 40 · 2021: 43 · 2020: 40 · 2019: 33 · 2018: 21 · 2017: 19 · 2016: 27 · 2015: 21 · 2014: 15 · 2013: 20 · 2012: 16
FWCI
11.27
Type
journal article
Language
en
Open access
Locations
  • Journal of Neuroscience (publishedVersion, cc-by-nc-sa)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Institute on Aging (P01AG022074)
  • National Heart, Lung, and Blood Institute (R01 HL37063, R01HL037063)
Topics
  • Health Sciences › Medicine › Physiology › Alzheimer's disease research and treatments
  • Life Sciences › Neuroscience › Neurology › Neuroinflammation and Neurodegeneration Mechanisms
  • Life Sciences › Neuroscience › Neurology › Barrier Structure and Function Studies
Keywords
apolipoprotein E, green fluorescent protein, astrocytes, microglia, hippocampal neurons, excitotoxic injury, kainic acid, choroid plexus, smooth muscle cells, central nervous system
MeSH terms
Animals, Apolipoproteins E, Brain, Gene Expression Regulation, Microscopy, Fluorescence, Neurons, Gene Targeting, Gene Expression Profiling, Green Fluorescent Proteins, Mice

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