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Gain of toxic apolipoprotein E4 effects in human iPSC-derived neurons is ameliorated by a small-molecule structure corrector.

ABSTRACT: Efforts to develop drugs for Alzheimer's disease (AD) have shown promise in animal studies, only to fail in human trials, suggesting a pressing need to study AD in human model systems. Using human neurons derived from induced pluripotent stem cells that expressed apolipoprotein E4 (ApoE4), a variant of the APOE gene product and the major genetic risk factor for AD, we demonstrated that ApoE4-expressing neurons had higher levels of tau phosphorylation, unrelated to their increased production of amyloid-? (A?) peptides, and that they displayed GABAergic neuron degeneration. ApoE4 increased A? production in human, but not in mouse, neurons. Converting ApoE4 to ApoE3 by gene editing rescued these phenotypes, indicating the specific effects of ApoE4. Neurons that lacked APOE behaved similarly to those expressing ApoE3, and the introduction of ApoE4 expression recapitulated the pathological phenotypes, suggesting a gain of toxic effects from ApoE4. Treatment of ApoE4-expressing neurons with a small-molecule structure corrector ameliorated the detrimental effects, thus showing that correcting the pathogenic conformation of ApoE4 is a viable therapeutic approach for ApoE4-related AD.

SUBMITTER: Wang C

PROVIDER: S-EPMC5948154 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Gain of toxic apolipoprotein E4 effects in human iPSC-derived neurons is ameliorated by a small-molecule structure corrector.

Wang Chengzhong C Najm Ramsey R Xu Qin Q Jeong Dah-Eun DE Walker David D Balestra Maureen E ME Yoon Seo Yeon SY Yuan Heidi H Li Gang G Miller Zachary A ZA Miller Bruce L BL Malloy Mary J MJ Huang Yadong Y

Nature medicine 20180409 5

Efforts to develop drugs for Alzheimer's disease (AD) have shown promise in animal studies, only to fail in human trials, suggesting a pressing need to study AD in human model systems. Using human neurons derived from induced pluripotent stem cells that expressed apolipoprotein E4 (ApoE4), a variant of the APOE gene product and the major genetic risk factor for AD, we demonstrated that ApoE4-expressing neurons had higher levels of tau phosphorylation, unrelated to their increased production of a ...[more]

PMID: 29632371

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Project description:In addition to being the greatest genetic risk factor for Alzheimer's disease, expression of the ɛ4 allele of apolipoprotein E can lead to cognitive decline during ageing that is independent of Alzheimer's amyloid-β and tau pathology. In human post-mortem tissue and mouse models humanized for apolipoprotein E, we examined the impact of apolipoprotein E4 expression on brain exosomes, vesicles that are produced within and secreted from late-endocytic multivesicular bodies. Compared to humans or mice homozygous for the risk-neutral ɛ3 allele we show that the ɛ4 allele, whether homozygous or heterozygous with an ɛ3 allele, drives lower exosome levels in the brain extracellular space. In mice, we show that the apolipoprotein E4-driven change in brain exosome levels is age-dependent: while not present at age 6 months, it is detectable at 12 months of age. Expression levels of the exosome pathway regulators tumor susceptibility gene 101 (TSG101) and Ras-related protein Rab35 (RAB35) were found to be reduced in the brain at the protein and mRNA levels, arguing that apolipoprotein E4 genotype leads to a downregulation of exosome biosynthesis and release. Compromised exosome production is likely to have adverse effects, including diminishing a cell's ability to eliminate materials from the endosomal-lysosomal system. This reduction in brain exosome levels in 12-month-old apolipoprotein E4 mice occurs earlier than our previously reported brain endosomal pathway changes, arguing that an apolipoprotein E4-driven failure in exosome production plays a primary role in endosomal and lysosomal deficits that occur in apolipoprotein E4 mouse and human brains. Disruption of these interdependent endosomal-exosomal-lysosomal systems in apolipoprotein E4-expressing individuals may contribute to amyloidogenic amyloid-β precursor protein processing, compromise trophic signalling and synaptic function, and interfere with a neuron's ability to degrade material, all of which are events that lead to neuronal vulnerability and higher risk of Alzheimer's disease development. Together, these data suggest that exosome pathway dysfunction is a previously unappreciated component of the brain pathologies that occur as a result of apolipoprotein E4 expression.

Project description:The APOE gene is diversified by three alleles ε2, ε3, and ε4 encoding corresponding apolipoprotein (apo) E isoforms. Possession of the ε4 allele is signified by increased risks of age-related cognitive decline, Alzheimer's disease (AD), and the rate of AD dementia progression. ApoE is secreted by astrocytes as high-density lipoprotein-like particles and these are internalized by neurons upon binding to neuron-expressed apoE receptors. ApoE isoforms differentially engage neuronal plasticity through poorly understood mechanisms. We examined here the effects of native apoE lipoproteins produced by immortalized astrocytes homozygous for ε2, ε3, and ε4 alleles on the maturation and the transcriptomic profile of primary hippocampal neurons. Control neurons were grown in the presence of conditioned media from Apoe -/- astrocytes. ApoE2 and apoE3 significantly increase the dendritic arbor branching, the combined neurite length, and the total arbor surface of the hippocampal neurons, while apoE4 fails to produce similar effects and even significantly reduces the combined neurite length compared to the control. ApoE lipoproteins show no systemic effect on dendritic spine density, yet apoE2 and apoE3 increase the mature spines fraction, while apoE4 increases the immature spine fraction. This is associated with opposing effects of apoE2 or apoE3 and apoE4 on the expression of NR1 NMDA receptor subunit and PSD95. There are 1,062 genes differentially expressed across neurons cultured in the presence of apoE lipoproteins compared to the control. KEGG enrichment and gene ontology analyses show apoE2 and apoE3 commonly activate expression of genes involved in neurite branching, and synaptic signaling. In contrast, apoE4 cultured neurons show upregulation of genes related to the glycolipid metabolism, which are involved in dendritic spine turnover, and those which are usually silent in neurons and are related to cell cycle and DNA repair. In conclusion, our work reveals that lipoprotein particles comprised of various apoE isoforms differentially regulate various neuronal arbor characteristics through interaction with neuronal transcriptome. ApoE4 produces a functionally distinct transcriptomic profile, which is associated with attenuated neuronal development. Differential regulation of neuronal transcriptome by apoE isoforms is a newly identified biological mechanism, which has both implication in the development and aging of the CNS.

Dataset Information

Gain of toxic apolipoprotein E4 effects in human iPSC-derived neurons is ameliorated by a small-molecule structure corrector.

Publications

Gain of toxic apolipoprotein E4 effects in human iPSC-derived neurons is ameliorated by a small-molecule structure corrector.

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