Pathogenic characteristics of genetically modified cells with TREM2 T44A mutation

Abstract

AbstractBackgroundTriggering Receptor Expressed on Myeloid Cells‐2 (TREM2) is known as a risk gene for Alzheimer’s disease (AD). and affect AD pathogenesis through beta‐amyloid (Aβ)‐related neuroinflammations and phagocytosis. TREM2 R47H mutation was the first reported from an AD patient in 2013. Although the TREM2 R47H variant was revealed to increase the risk of AD by three times, further mutations still need to study. Here, we found TREM2 T44A mutation from a patient of a 65‐year‐old AD patient. In order to confirm the pathogenicity of TREM2 T44A, the genetically modified cells were produced and investigated the association of the TREM2 gene with Aβ‐related pathology.MethodTREM2 Wild type (WT) and T44A were transfected onto the HEK 293, SHSY5Y, U87 cells by using a plasmid transfection system and selected using geneticin (G418). Gene expression and TREM2 protein was measured. For measuring Aβ uptakes, Aβ was measured after incubation with cells. Cell phagocytosis was conducted with treating pHrodo labeled with Aβ and obtained cell images and video.ResultTREM2 gene was overexpressed in transfected cells and TREM2 protein was elevated, but TREM2 T44A lowered compared to WT. TREM2 T44A showed higher Aβ42/40 ratio, with increasing extracellular Aβ42. The Aβ42 uptake were relatively lowered than TREM2 WT. Through images and video, TREM2 T44A showed lower red fluorescence than WT, but similar to MOCK.ConclusionIn this study, we transfected TREM2 WT and T44A in a variety of cell lines (HEK 293, SHSY5Y, U87) to investigate the pathogenicity of TREM2 T44A. TREM2 T44A was shown to increase extracellular Aβ42 and decrease Aβ42 uptake. This suggests that the Aβ uptake and elimination function of TREM2 was loosed by the mutation, and therefore Aβ was not completely removed, resulting in a slight increase in extracellular Aβ in the mutant cell. The loss of the Aβ uptake correlated with confocal and video results, the red fluorescence signals were decreased in TREM2 T44A, suggesting relatively lower Aβ phagocytosis. Thus, Aβ phagocytosis was inhibited by TREM2 mutation, and the lowered Aβ uptake could not clear it, suggesting that Aβ growth and accumulation may influence the pathogenicity of AD.