# Role of TREM2 gain-of-function mutations in modulating microglial pathology in Alzheimer's disease

> **NIH NIH R01** · MASSACHUSETTS GENERAL HOSPITAL · 2021 · $406,400

## Abstract

Project Summary
Genome-wide association studies have identified many Alzheimer’s disease (AD) risk genes related to immune
response. Among these are the microglial receptors CD33 and TREM2. We previously showed that knock-out
of CD33 attenuated amyloid beta (Aβ) pathology and improved cognition in 5XFAD mice, both of which were
abrogated by additional Trem2 knock-out. Knocking out Trem2 in 5XFAD mice exacerbated Aβ pathology and
neurodegeneration but reduced microglia numbers. RNA-seq profiling of microglia revealed that genes related
to phagocytosis and signaling (IL-6, IL-8, acute phase response) are downregulated in 5XFAD;Trem2-/- mice.
Differential gene expression in 5XFAD;CD33-/- microglia depended on the presence of Trem2, suggesting
TREM2 acts downstream of CD33. Moreover, we reported that the D87N and T96K variants of TREM2
increased AD risk in the NIMH family-based genetic data and ADSP case-control samples and showed that
these variants increased binding to TREM2 ligands. In our preliminary study, we found that the gain-of-function
Trem2T96K variant increased levels of insoluble Aβ42 but reduced both microglia numbers and clustering of
microglia around Aβ plaques in 5XFAD mice. Furthermore, the Trem2T96K variant reduced secretion of sTrem2
in 5XFAD mice. Finally, the T96K variant led to reduced cell surface expression and secretion of TREM2 in
human microglial cell lines. Here, we propose to 1) assess the impact of TREM2 gain-of-function mutations on
AD pathogenesis, 2) investigate the effects of these mutations on microglial activation and gene expression,
and 3) identify and characterize novel AD-associated TREM2 gain-of-function mutations as well as target
TREM2 for therapeutic purposes. In Aim 1, we will examine the effects of the gain-of-function Trem2T96K
mutation on Aβ pathology, neurodegeneration and plaque associated-neuritic dystrophy in 5XFAD mice. We
will also determine whether Trem2T96K impacts cognitive function in 5XFAD mice. In Aim 2, we will investigate
the impact of the gain-of-function Trem2T96K mutation on microglial cell activation and recruitment to Aβ
plaques as well as immune response to lipopolysaccharide stimulation in 5XFAD mice. RNA-seq profiling of
microglia will reveal the effects of Trem2T96K on microglial gene expression signature and how they compare to
disease-associated microglia. In Aim 3, we will analyze whole genome sequencing data from the NIMH family
sample and NIA ADSP to identify novel AD-associated TREM2 mutations that will be characterized for their
effects on ligand-dependent activation of TREM2. We will then introduce novel TREM2 gain-of-function
mutations into iPSC-derived human microglia-like cells using CRISPR/Cas9 system and investigate underlying
molecular mechanisms. Finally, we will predict and validate novel targeted drugs that mimic TREM2 activation
and/or oppose TREM2 loss-of-function using computational approaches. The major goals of this proposal are
to comprehensively assess the...

## Key facts

- **NIH application ID:** 10276732
- **Project number:** 1R01AG073292-01
- **Recipient organization:** MASSACHUSETTS GENERAL HOSPITAL
- **Principal Investigator:** Ana Griciuc
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $406,400
- **Award type:** 1
- **Project period:** 2021-09-01 → 2026-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10276732

## Citation

> US National Institutes of Health, RePORTER application 10276732, Role of TREM2 gain-of-function mutations in modulating microglial pathology in Alzheimer's disease (1R01AG073292-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10276732. Licensed CC0.

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