CNS infiltration by Tet2-mutant peripheral myeloid cells protects from Alzheimer's Disease

Microglia play a key role in Alzheimer's disease (AD) pathogenesis by clearing damaged cells and misfolded proteins such as b-amyloid. In a mouse transplant model of AD, we identified a population of bone marrow-derived immune cells that had infiltrated the brain and taken on microglia characteristics. The percentage of these infiltrating microglia-like cells within the brain was increased in AD mice that were transplanted with Tet2-mutant bone marrow when compared to mice transplanted with either wildtype or Dnmt3a-mutant bone marrow following LPS treatment. We explored the effect of mutation of TET2 and DNMT3A in human induced microglial-like cells (iMGLs) and found that TET2-mutant iMGLs were more phagocytic and hyperinflammatory than DNMT3A-mutant or wildtype iMGLs. Bulk RNA sequencing of iMGLs confirmed the upregulation of phagocytic pathways in TET2-mutant iMGLs compared to DNMT3A-mutant or wildtype iMGLs. Overall design: Bulk RNA sequencing of WT, TET2-mutant, and DNMT3A-mutant human induced microglial-like cells (iMGLs) that were either untreated or treated with 100ng/mL LPS for 24 hours. iMGLs were differentiated from isogenic human induced pluripotent stem cell (iPSC) lines that were CRISPR/Cas9 edited to harbor either DNMT3AR882H/WT or TET2DelE3-E11/WT mutations.

小胶质细胞（Microglia）通过清除受损细胞与β-淀粉样蛋白（β-amyloid）等错误折叠蛋白，在阿尔茨海默病（AD）的发病机制中发挥关键作用。在阿尔茨海默病小鼠移植模型中，本研究鉴定出一群骨髓来源的免疫细胞，它们浸润大脑并获得小胶质细胞特性。经脂多糖（LPS）处理后，相较于移植野生型或DNMT3A突变型骨髓的AD小鼠，移植TET2突变型骨髓的AD小鼠脑内这类浸润性类小胶质细胞的占比显著升高。本研究在人类诱导性类小胶质细胞（iMGLs）中探究了TET2与DNMT3A突变的功能效应，发现TET2突变型iMGLs相较DNMT3A突变型或野生型iMGLs，吞噬活性更强且炎症反应更为亢进。对iMGLs开展批量RNA测序（bulk RNA sequencing）证实，相较于DNMT3A突变型或野生型iMGLs，TET2突变型iMGLs的吞噬相关通路出现显著上调。
实验整体设计：对野生型（WT）、TET2突变型及DNMT3A突变型人类诱导性类小胶质细胞（iMGLs）进行批量RNA测序，这些细胞分别经100ng/mL脂多糖（LPS）处理24小时或未作处理。上述iMGLs均由同基因背景的人类诱导多能干细胞（iPSC）系分化而来，该干细胞系经CRISPR/Cas9编辑，分别携带DNMT3AR882H/WT或TET2DelE3-E11/WT突变。