背景:阿尔茨海默病的进展导致突触丢失,神经网络功能障碍和认知失败。蛋白质聚集体的积累和脑免疫激活在突触衰竭中具有触发作用,但突触丧失的神经元机制尚不清楚。在神经元表面,已知细胞朊病毒蛋白(PrPC)是淀粉样蛋白-β寡聚体(Aβo)的高亲和力结合位点。然而,PrPC对tau积累的敲入AD模型的依赖性,转录组改变和成像生物标志物是未知的。
方法:在纯合AppNL-G-F/hMapt双敲入小鼠(DKI)中,PrPC的必要性作为年龄的函数进行了研究。将Prnp表达缺失的AppNL-G-F/hMapt小鼠的表型(DKI;Prnp-/-)与完整Prnp的DKI小鼠进行比较,具有Prnp(Prnp-/-)靶向缺失的小鼠,和具有完整Prnp(WT)的小鼠。检查的表型包括行为缺陷,PET成像的突触损失,免疫组织学突触丢失,tau病理学,胶质增生,炎症标志物,和snRNA-seq转录组分析。
结果:到9个月大,DKI小鼠表现出学习和记忆障碍,但DKI;Prnp-/-和Prnp-/-组与WT没有区别。DKI大脑中的突触损失,通过[18F]SynVesT-1SV2APET或抗SV2A免疫组织学测量,已被Prnp删除阻止。Tau在aa217和202/205磷酸化的积累,突触的C1q标记,在DKI小鼠中,营养不良性神经突都增加,但随着Prnp缺失均降低至WT水平。相比之下,星形胶质增生,DKI和DKI之间的小胶质细胞增生和Aβ水平没有变化;Prnp-/-组。单核转录组学显示DKI小鼠相对于WT的神经元和神经胶质中的差异表达。对于DKI;Prnp-/-小鼠,DKI小鼠中差异表达的大多数神经元基因相对于WT不再显著改变,但大多数依赖神经胶质DKI的基因表达变化仍然存在。通过Prnp缺失校正的DKI依赖性神经元基因在生物信息上与突触功能相关。其他基因仅在Prnp-/-或DKI中独特地改变;Prnp-/-组。
结论:因此,PrPC依赖性突触丢失,在不清除Aβ斑块或防止神经胶质反应的情况下,可以逆转AD小鼠的磷酸化tau积累和神经元基因表达。这支持靶向Aβo-PrPC相互作用以防止AD中的Aβo-神经毒性和病理性tau积累。
Progression of Alzheimer\'s disease leads to synapse loss, neural network dysfunction and cognitive failure. Accumulation of protein aggregates and brain immune activation have triggering roles in synaptic failure but the neuronal mechanisms underlying synapse loss are unclear. On the neuronal surface, cellular prion protein (PrPC) is known to be a high-affinity binding site for Amyloid-β oligomers (Aβo). However, PrPC\'s dependence in knock-in AD models for tau accumulation, transcriptomic alterations and imaging biomarkers is unknown.
The necessity of PrPC was examined as a function of age in homozygous AppNL-G-F/hMapt double knock-in mice (DKI). Phenotypes of AppNL-G-F/hMapt mice with a deletion of Prnp expression (DKI; Prnp-/-) were compared with DKI mice with intact Prnp, mice with a targeted deletion of Prnp (Prnp-/-), and mice with intact Prnp (WT). Phenotypes examined included behavioral deficits, synapse loss by PET imaging, synapse loss by immunohistology, tau pathology, gliosis, inflammatory markers, and snRNA-seq transcriptomic profiling.
By 9 months age, DKI mice showed learning and memory impairment, but DKI; Prnp-/- and Prnp-/- groups were indistinguishable from WT. Synapse loss in DKI brain, measured by [18F]SynVesT-1 SV2A PET or anti-SV2A immunohistology, was prevented by Prnp deletion. Accumulation of Tau phosphorylated at aa 217 and 202/205, C1q tagging of synapses, and dystrophic neurites were all increased in DKI mice but each decreased to WT levels with Prnp deletion. In contrast, astrogliosis, microgliosis and Aβ levels were unchanged between DKI and DKI; Prnp-/- groups. Single-nuclei transcriptomics revealed differential expression in neurons and glia of DKI mice relative to WT. For DKI; Prnp-/- mice, the majority of neuronal genes differentially expressed in DKI mice were no longer significantly altered relative to WT, but most glial DKI-dependent gene expression changes persisted. The DKI-dependent neuronal genes corrected by Prnp deletion associated bioinformatically with synaptic function. Additional genes were uniquely altered only in the Prnp-/- or the DKI; Prnp-/- groups.
Thus, PrPC-dependent synapse loss, phospho-tau accumulation and neuronal gene expression in AD mice can be reversed without clearing Aβ plaque or preventing gliotic reaction. This supports targeting the Aβo-PrPC interaction to prevent Aβo-neurotoxicity and pathologic tau accumulation in AD.