Defects in lysosomal function and lipid metabolism in human microglia harboring a TREM2 loss of function mutation
Document Type
Article
Abstract
TREM2 is an innate immune receptor expressed by microglia in the adult brain. Genetic variation in the TREM2 gene has been implicated in risk for Alzheimer's disease and frontotemporal dementia, while homozygous TREM2 mutations cause a rare leukodystrophy, Nasu-Hakola disease (NHD). Despite extensive investigation, the role of TREM2 in NHD pathogenesis remains poorly understood. Here, we investigate the mechanisms by which a homozygous stop-gain TREM2 mutation (p.Q33X) contributes to NHD. Induced pluripotent stem cell (iPSC)-derived microglia (iMGLs) were generated from two NHD families: three homozygous TREM2 p.Q33X mutation carriers (termed NHD), two heterozygous mutation carriers, one related non-carrier, and two unrelated non-carriers. Transcriptomic and biochemical analyses revealed that iMGLs from NHD patients exhibited lysosomal dysfunction, downregulation of cholesterol genes, and reduced lipid droplets compared to controls. Also, NHD iMGLs displayed defective activation and HLA antigen presentation. This defective activation and lipid droplet content were restored by enhancing lysosomal biogenesis through mTOR-dependent and independent pathways. Alteration in lysosomal gene expression, such as decreased expression of genes implicated in lysosomal acidification (ATP6AP2) and chaperone mediated autophagy (LAMP2), together with reduction in lipid droplets were also observed in post-mortem brain tissues from NHD patients, thus closely recapitulating in vivo the phenotype observed in iMGLs in vitro. Our study provides the first cellular and molecular evidence that the TREM2 p.Q33X mutation in microglia leads to defects in lysosomal function and that compounds targeting lysosomal biogenesis restore a number of NHD microglial defects. A better understanding of how microglial lipid metabolism and lysosomal machinery are altered in NHD and how these defects impact microglia activation may provide new insights into mechanisms underlying NHD and other neurodegenerative diseases.
Keywords
Induced pluripotent stem cells, Lysosome, Microglia, Nasu-Hakola disease, TREM2, Transcriptomics
Medical Subject Headings
Adult; Humans; Microglia (metabolism); Lipid Metabolism (genetics); Loss of Function Mutation; Mutation (genetics); Alzheimer Disease (genetics, metabolism); Lysosomes (metabolism); Membrane Glycoproteins (genetics, metabolism); Receptors, Immunologic (genetics, metabolism); Prorenin Receptor
Publication Date
6-1-2023
Publication Title
Acta neuropathologica
E-ISSN
1432-0533
Volume
145
Issue
6
First Page
749
Last Page
772
PubMed ID
37115208
Digital Object Identifier (DOI)
10.1007/s00401-023-02568-y
Recommended Citation
Filipello, Fabia; You, Shih-Feng; Mirfakhar, Farzaneh S.; Mahali, Sidhartha; Bollman, Bryan; Acquarone, Mariana; Korvatska, Olena; Marsh, Jacob A.; Sivaraman, Anirudh; Martinez, Rita; Cantoni, Claudia; De Feo, Luca; Ghezzi, Laura; Minaya, Miguel A.; Renganathan, Arun; Cashikar, Anil G.; Satoh, Jun-Ichi; Beatty, Wandy; Iyer, Abhirami K.; Cella, Marina; Raskind, Wendy H.; Piccio, Laura; and Karch, Celeste M., "Defects in lysosomal function and lipid metabolism in human microglia harboring a TREM2 loss of function mutation" (2023). Translational Neuroscience. 2326.
https://scholar.barrowneuro.org/neurobiology/2326