Alzheimer’s-associated PLCγ2 is a signaling node required for both TREM2 function and the inflammatory response in human microglia

Andreone, Benjamin J.; Przybyla, Laralynne; Llapashtica, Ceyda; Rana, Anil; Davis, Sonnet S.; Lengerich, Bettina van; Lin, Karin; Ju, Shaoqing; Yuan, Mei; Astarita, Giuseppe; Paolo, Gilbert Di; Sandmann, Thomas; Monroe, Kathryn M.; Lewcock, Joseph W.

doi:10.1038/s41593-020-0650-6

Cited by 181 publications

(275 citation statements)

References 62 publications

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“…Based on recent studies in human induced pluripotent stem cell (iPSC)-derived PLCγ2 knockout microglia (iMG), PLCγ2 is required for the signaling pathway initiated by the Triggering receptor expressed on myeloid cells 2 (Trem2) ( Fig. 1a) [6]. Loss of PLCγ2 function consequently reduces TREM2dependent support of cell survival, phagocytosis and lipid metabolism.…”

Section: Resultsmentioning

confidence: 99%

“…The P522R variant increases Plcγ2 enzyme activity and enhances survival, phagocytosis, and inflammatory response Bone marrow-derived macrophage (BMDM) cultures were established from femur and tibia bones of sixmonth-old Plcγ2-P522R KI mice and their wild type (WT) littermates [9][10][11]. The P522R variant has previously been shown to increase the production of inositol phosphate (Ip1, a surrogate of Ip3) in transiently transfected HEK293 and COS cells [12], while the loss of PLCγ2 or TREM2 in iMGs reduces Ip1 production [6]. Accordingly, significantly higher basal levels of Ip1 were detected in cultured KI BMDM cells as compared to WT cells ( Fig.…”

Section: Resultsmentioning

confidence: 99%

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The Alzheimer’s disease-associated protective Plcγ2-P522R variant promotes immune functions

Takalo

Wittrahm

Wefers

et al. 2020

Mol Neurodegeneration

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Background Microglia-specific genetic variants are enriched in several neurodegenerative diseases, including Alzheimer’s disease (AD), implicating a central role for alterations of the innate immune system in the disease etiology. A rare coding variant in the PLCG2 gene (rs72824905, p.P522R) expressed in myeloid lineage cells was recently identified and shown to reduce the risk for AD. Methods To assess the role of the protective variant in the context of immune cell functions, we generated a Plcγ2-P522R knock-in (KI) mouse model using CRISPR/Cas9 gene editing. Results Functional analyses of macrophages derived from homozygous KI mice and wild type (WT) littermates revealed that the P522R variant potentiates the primary function of Plcγ2 as a Pip2-metabolizing enzyme. This was associated with improved survival and increased acute inflammatory response of the KI macrophages. Enhanced phagocytosis was observed in mouse BV2 microglia-like cells overexpressing human PLCγ2-P522R, but not in PLCγ2-WT expressing cells. Immunohistochemical analyses did not reveal changes in the number or morphology of microglia in the cortex of Plcγ2-P522R KI mice. However, the brain mRNA signature together with microglia-related PET imaging suggested enhanced microglial functions in Plcγ2-P522R KI mice. Conclusion The AD-associated protective Plcγ2-P522R variant promotes protective functions associated with TREM2 signaling. Our findings provide further support for the idea that pharmacological modulation of microglia via TREM2-PLCγ2 pathway-dependent stimulation may be a novel therapeutic option for the treatment of AD.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

The Alzheimer’s disease-associated protective Plcγ2-P522R variant promotes immune functions

Takalo

Wittrahm

Wefers

et al. 2020

Mol Neurodegeneration

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“…The iPSC technology may be particularly important in modeling neurodegenerative disease, given difficulty in accessing patient tissue and given key differences between human microglia and those in animal models [60]. Several protocols exist to differentiate iPSCs into microglia, with ramifications for cellular remyelinating therapy [61] and microglia-associated disease modeling [58].…”

Section: Hematopoietic Contributions To Neurodegenerative Diseasementioning

confidence: 99%

“…Several protocols exist to differentiate iPSCs into microglia, with ramifications for cellular remyelinating therapy [61] and microglia-associated disease modeling [58]. For example, gene-edited iPSCs recently demonstrated that Triggering receptor expression on myeloid cells 2 (TREM2) and Phospholipase C g2 (PLCG2) participate in a common pathway to mediate microglial cell survival, phagocytosis, and lipid metabolism [60]. Loss of either of these genes caused dysfunctional microglial properties that likely underlie an associated increase in propensity for individuals harboring mutations in these genes to develop neurodegenerative disorders, such as Alzheimer's disease.…”

Section: Hematopoietic Contributions To Neurodegenerative Diseasementioning

confidence: 99%

Mechanistic and Translational Advances Using iPSC-Derived Blood Cells

Thom

Chou

French

2020

Preprint

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Human induced pluripotent stem cell (iPSC)-based model systems can be used to produce blood cells for the study of both hematologic and non-hematologic disorders. This commentary discusses recent advances that have utilized iPSC-derived red blood cells, megakaryocytes, myeloid cells, and lymphoid cells to model hematopoietic disorders. In addition, we review recent studies that have defined how microglial cells differentiated from iPSC-derived monocytes impact neurodegenerative disease. Related translational insights highlight the utility of iPSC models for studying pathologic anemia, bleeding, thrombosis, autoimmunity, immunodeficiency, blood cancers, and neurodegenerative disease such as Alzheimer’s.

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“…In an effort to understand the contribution of non-neuronal cells to C9orf72 ALS/FTD, we generated a human in vitro cell culture model by differentiating C9orf72 ALS/FTD patient derived induced pluripotent stem cell (iPSCs) into microglia. While the use of a human iPSC-microglia (iPSC-MG) culture technique has only recently been developed, several studies have implemented this technology to study the role of microglia in neurodegenerative diseases, in particular Alzheimer's disease (42)(43)(44)(45)(46)(47)(48). To our knowledge, the intrinsic properties of microglia carrying a C9orf72 HRE, and their role in C9orf72 ALD/FTD neurodegeneration, have yet to be examined.…”

Section: Introductionmentioning

confidence: 99%

Cellular and molecular phenotypes ofC9orf72ALS/FTD patient derived iPSC-microglia mono-cultures

Lorenzini

Alsop

Levy

et al. 2020

Preprint

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Background: A mutation in the C9orf72 gene is the most common genetic mutation of familial and sporadic ALS, as well as familial FTD. While prior studies have focused on elucidating the mechanisms of neuronal dysfunction and neurodegeneration associated with this genetic mutation, the contribution of microglia to disease pathogenesis in the ALS/FTD disease spectrum remains poorly understood. Methods: Here, we generated a new disease model consisting of cultured C9orf72 ALS/FTD patient-derived induced pluripotent stem cells differentiated into microglia (iPSC-MG). We used this model to study the intrinsic cellular and molecular phenotypes of microglia triggered by the C9orf72 gene mutation. Results: We show that C9orf72 ALS/FTD iPSC-MG have a similar transcriptional profile compared to control iPSC-MG, despite the presence of C9orf72-associated phenotypes including reduced C9orf72 protein levels and dipeptide-repeat protein translation. Interestingly, C9orf72 ALS/FTD iPSC-MG exhibit intrinsic dysfunction of phagocytic activity upon exposure to Aβ or brain synaptoneurosomes and display a heightened inflammatory response. Detailed analysis of the endosomal and lysosomal pathways revealed altered expression of endosomal marker early endosome antigen 1 and lysosomal associated membrane protein 1 in C9orf72 ALS/FTD iPSC-MG, which was confirmed in patient postmortem tissues. Conclusions: These findings demonstrate that unstimulated C9orf72 iPSC-MG mono-cultures share a largely similar transcriptome profile with control microglia, despite the presence of C9orf72 disease phenotypes. The dysfunction of the endosomal-lysosomal pathway as demonstrated by aberrant microglia phagocytosis and engulfment of cellular debris and brain pathogens suggests that disease-related microglia phenotypes are not intrinsic but instead require microglia to be activated. In summary, the C9orf72 iPSC-MG culture system provides a novel human disease model to study the role of microglia in C9orf72 ALS/FTD disease pathogenesis.

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Alzheimer’s-associated PLCγ2 is a signaling node required for both TREM2 function and the inflammatory response in human microglia

Cited by 181 publications

References 62 publications

The Alzheimer’s disease-associated protective Plcγ2-P522R variant promotes immune functions

The Alzheimer’s disease-associated protective Plcγ2-P522R variant promotes immune functions

Mechanistic and Translational Advances Using iPSC-Derived Blood Cells

Cellular and molecular phenotypes ofC9orf72ALS/FTD patient derived iPSC-microglia mono-cultures

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