Department of Neurology with Institute of Translational Neurology, University Hospital Münster, Münster, Germany.
Institute of Experimental Internal Medicine, Otto-von-Guericke University, Magdeburg, Germany.
Redox Biol. 2023 Feb;59:102597. doi: 10.1016/j.redox.2022.102597. Epub 2022 Dec 30.
Tauopathies are a major type of proteinopathies underlying neurodegenerative diseases. Mutations in the tau-encoding MAPT-gene lead to hereditary cases of frontotemporal lobar degeneration (FTLD)-tau, which span a wide phenotypic and pathological spectrum. Some of these mutations, such as the N279K mutation, result in a shift of the physiological 3R/4R ratio towards the more aggregation prone 4R isoform. Other mutations such as V337M cause a decrease in the in vitro affinity of tau to microtubules and a reduced ability to promote microtubule assembly. Whether both mutations address similar downstream signalling cascades remains unclear but is important for potential rescue strategies. Here, we developed a novel and optimised forward programming protocol for the rapid and highly efficient production of pure cultures of glutamatergic cortical neurons from hiPSCs. We apply this protocol to delineate mechanisms of neurodegeneration in an FTLD-tau hiPSC-model consisting of MAPT- or MAPT-mutants and wild-type or isogenic controls. The resulting cortical neurons express MAPT-genotype-dependent dominant proteome clusters regulating apoptosis, ROS homeostasis and mitochondrial function. Related pathways are significantly upregulated in MAPT neurons but not in MAPT neurons or controls. Live cell imaging demonstrates that both MAPT mutations affect excitability of membranes as reflected in spontaneous and stimulus evoked calcium signals when compared to controls, albeit more pronounced in MAPT neurons. These spontaneous calcium oscillations in MAPT neurons triggered mitochondrial hyperpolarisation and fission leading to mitochondrial ROS production, but also ROS production through NOX2 acting together to induce cell death. Importantly, we found that these mechanisms are MAPT mutation-specific and were observed in MAPT neurons, but not in MAPT neurons, supporting a pathological role of the 4R tau isoform in redox disbalance and highlighting MAPT-mutation specific clinicopathological-genetic correlations, which may inform rescue strategies in different MAPT mutations.
tau 病是神经退行性疾病中主要的蛋白质病变类型之一。tau 编码基因 MAPT 中的突变导致额颞叶痴呆（FTLD）-tau 的遗传性病例，其表现出广泛的表型和病理学谱。这些突变中的一些，如 N279K 突变，导致生理 3R/4R 比率向更易于聚集的 4R 异构体倾斜。其他突变，如 V337M，导致 tau 与微管的体外亲和力降低，促进微管组装的能力降低。这两种突变是否针对相似的下游信号级联仍不清楚，但对于潜在的挽救策略很重要。在这里，我们开发了一种新的、优化的正向编程协议，用于快速高效地从 hiPSC 中产生纯谷氨酸能皮质神经元培养物。我们应用该协议来描绘由 MAPT 或 MAPT 突变体和野生型或同基因对照组成的 FTLD-tau hiPSC 模型中的神经退行性变机制。所得皮质神经元表达 MAPT 基因型依赖性的显性蛋白质组簇，调节细胞凋亡、ROS 稳态和线粒体功能。相关途径在 MAPT 神经元中显著上调，但在 MAPT 神经元或对照中没有上调。活细胞成像表明，与对照相比，两种 MAPT 突变都影响膜的兴奋性，表现为自发和刺激诱发的钙信号，而在 MAPT 神经元中更为明显。MAPT 神经元中的这些自发钙振荡触发线粒体超极化和裂变，导致线粒体 ROS 产生，但也通过共同作用诱导细胞死亡的 NOX2 产生 ROS。重要的是，我们发现这些机制是 MAPT 突变特异性的，仅在 MAPT 神经元中观察到，而在 MAPT 神经元中未观察到，支持 4R tau 异构体在氧化还原失衡中的病理作用，并突出了 MAPT 突变特异性的临床病理遗传学相关性，这可能为不同 MAPT 突变提供挽救策略。
