Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
MRC Centre for Neurodevelopmental Disorders, King's College London, London, UK.
Hippocampus. 2023 Apr;33(4):322-346. doi: 10.1002/hipo.23502. Epub 2023 Jan 28.
Hippocampal neurogenesis (HN) is considered an important mechanism underlying lifelong brain plasticity, and alterations in this process have been implicated in early Alzheimer's disease progression. APOE polymorphism is the most common genetic risk factor for late-onset Alzheimer's disease where the ε4 genotype is associated with a significantly earlier disease onset compared to the neutral ε3 allele. Recently, APOE has been shown to play an important role in the regulation of HN. However, the time-dependent impact of its polymorphism in humans remains elusive, partially due to the difficulties of studying human HN in vivo. To bridge this gap of knowledge, we used an in vitro cellular model of human HN and performed a time course characterization on isogenic induced pluripotent stem cells with different genotypes of APOE. We found that APOE itself was more highly expressed in ε4 at the stem cell stage, while the divergence of differential gene expression phenotype between ε4 and ε3 became prominent at the neuronal stage of differentiation. This divergence was not associated with the differential capacity to generate dentate gyrus granule cell-like neurons, as its level was comparable between ε4 and ε3. Transcriptomic profiling across different stages of neurogenesis indicated a clear "maturation of functional neurons" phenotype in ε3 neural progenitors and neurons, while genes differentially expressed only in ε4 neurons suggested potential alterations in "metabolism and mitochondrial function." Taken together, our in vitro investigation suggests that APOE ε4 allele can exert a transcriptome-wide effect at the later stages of HN, without altering the overall level of neurogenesis per se.
海马神经发生(HN)被认为是大脑终生可塑性的重要机制,该过程的改变与早期阿尔茨海默病的进展有关。APOE 多态性是晚发性阿尔茨海默病最常见的遗传风险因素,其中 ε4 基因型与中性 ε3 等位基因相比,疾病发作明显更早。最近,APOE 被证明在 HN 的调节中发挥重要作用。然而,其多态性在人类中的时间依赖性影响仍不清楚,部分原因是难以在体内研究人类 HN。为了弥补这一知识空白,我们使用了人类 HN 的体外细胞模型,并对具有不同 APOE 基因型的同基因诱导多能干细胞进行了时间过程特征分析。我们发现,APOE 自身在干细胞阶段在 ε4 中表达更高,而在分化的神经元阶段,ε4 和 ε3 之间的差异表达表型的差异变得明显。这种差异与产生齿状回颗粒细胞样神经元的差异能力无关,因为其在 ε4 和 ε3 之间相当。整个神经发生过程中的转录组谱分析表明,ε3 神经祖细胞和神经元中存在明显的“功能性神经元成熟”表型,而仅在 ε4 神经元中差异表达的基因则表明“代谢和线粒体功能”可能存在潜在改变。总的来说,我们的体外研究表明,APOE ε4 等位基因可以在 HN 的后期阶段发挥全转录组效应,而不会改变神经发生的总体水平。
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