Abstract：
BACKGROUND: Molecular characterization of late-onset Alzheimer\'s disease (LOAD), the leading cause of age-related dementia, has revealed transcripts, proteins, and pathway alterations associated with disease. Assessing these postmortem signatures of LOAD in experimental model systems can further elucidate their relevance to disease origins and progression. Model organisms engineered with human genetic factors further link these signatures to disease-associated variants, especially when studies are designed to leverage homology across species. Here we assess differential gene splicing patterns in aging mouse models carrying humanized APOE4 and/or the Trem2*R47H variant on a C57BL/6J background. We performed a differential expression of gene (DEG) and differential splicing analyses on whole brain transcriptomes at multiple ages. To better understand the difference between differentially expressed and differentially spliced genes, we evaluated enrichment of KEGG pathways and cell-type specific gene signatures of the adult brain from each alteration type. To determine LOAD relevance, we compared differential splicing results from mouse models with multiple human AD splicing studies.
RESULTS: We found that differentially expressed genes in Trem2*R47H mice were significantly enriched in multiple AD-related pathways, including immune response, osteoclast differentiation, and metabolism, whereas differentially spliced genes were enriched for neuronal related functions, including GABAergic synapse and glutamatergic synapse. These results were reinforced by the enrichment of microglial genes in DEGs and neuronal genes in differentially spliced genes in Trem2*R47H mice. We observed significant overlap between differentially spliced genes in Trem2*R47H mice and brains from human AD subjects. These effects were absent in APOE4 mice and suppressed in APOE4.Trem2*R47H double mutant mice relative to Trem2*R47H mice.
CONCLUSIONS: The cross-species observation that alternative splicing observed in LOAD are present in Trem2*R47H mouse models suggests a novel link between this candidate risk gene and molecular signatures of LOAD in neurons and demonstrates how deep molecular analysis of new genetic models links molecular disease outcomes to a human candidate gene.
RESULTS: We found that differentially expressed genes in Trem2*R47H mice were significantly enriched in multiple AD-related pathways, including immune response, osteoclast differentiation, and metabolism, whereas differentially spliced genes were enriched for neuronal related functions, including GABAergic synapse and glutamatergic synapse. These results were reinforced by the enrichment of microglial genes in DEGs and neuronal genes in differentially spliced genes in Trem2*R47H mice. We observed significant overlap between differentially spliced genes in Trem2*R47H mice and brains from human AD subjects. These effects were absent in APOE4 mice and suppressed in APOE4.Trem2*R47H double mutant mice relative to Trem2*R47H mice.
CONCLUSIONS: The cross-species observation that alternative splicing observed in LOAD are present in Trem2*R47H mouse models suggests a novel link between this candidate risk gene and molecular signatures of LOAD in neurons and demonstrates how deep molecular analysis of new genetic models links molecular disease outcomes to a human candidate gene.
摘要：
背景：迟发性阿尔茨海默病（LOAD）的分子特征，老年痴呆症的主要病因,已经披露了成绩单，蛋白质，以及与疾病相关的通路改变。在实验模型系统中评估LOAD的这些事后签名可以进一步阐明它们与疾病起源和进展的相关性。用人类遗传因素设计的模型生物进一步将这些特征与疾病相关的变异联系起来，特别是当研究旨在利用物种间的同源性时。在这里，我们评估了在C57BL/6J背景下携带人源化APOE4和/或Trem2*R47H变体的衰老小鼠模型中的差异基因剪接模式。我们对多个年龄的全脑转录组进行了基因差异表达（DEG）和差异剪接分析。为了更好地理解差异表达和差异剪接基因之间的差异，我们评估了KEGG通路的富集情况和每种改变类型的成年大脑的细胞类型特异性基因特征.要确定LOAD相关性，我们比较了小鼠模型和多种人类AD剪接研究的差异剪接结果.
结果：我们发现Trem2*R47H小鼠的差异表达基因在多个AD相关通路中显著富集，包括免疫反应，破骨细胞分化，和新陈代谢，而差异剪接基因富集神经元相关功能，包括GABA能突触和谷氨酸能突触。在Trem2*R47H小鼠中，DEGs中的小胶质细胞基因和差异剪接基因中的神经元基因的富集加强了这些结果。我们观察到Trem2*R47H小鼠和人类AD受试者的大脑中的差异剪接基因之间的显著重叠。这些作用在APOE4小鼠中不存在并且在APOE4中被抑制。相对于Trem2*R47H小鼠,Trem2*R47H双突变小鼠。
结论：在Trem2*R47H小鼠模型中存在LOAD中观察到的可变剪接的跨物种观察表明，该候选风险基因与神经元中LOAD的分子特征之间存在新的联系，并证明了新遗传模型的深层分子分析如何将分子疾病结果与人类候选基因联系起来。
结果：我们发现Trem2*R47H小鼠的差异表达基因在多个AD相关通路中显著富集，包括免疫反应，破骨细胞分化，和新陈代谢，而差异剪接基因富集神经元相关功能，包括GABA能突触和谷氨酸能突触。在Trem2*R47H小鼠中，DEGs中的小胶质细胞基因和差异剪接基因中的神经元基因的富集加强了这些结果。我们观察到Trem2*R47H小鼠和人类AD受试者的大脑中的差异剪接基因之间的显著重叠。这些作用在APOE4小鼠中不存在并且在APOE4中被抑制。相对于Trem2*R47H小鼠,Trem2*R47H双突变小鼠。
结论：在Trem2*R47H小鼠模型中存在LOAD中观察到的可变剪接的跨物种观察表明，该候选风险基因与神经元中LOAD的分子特征之间存在新的联系，并证明了新遗传模型的深层分子分析如何将分子疾病结果与人类候选基因联系起来。
