Abstract
Background: Microglial dysfunction plays a causative role in Alzheimer's disease (AD) pathogenesis. Here we focus on a germline insertion/deletion variant mapping SIRPβ1, a surface receptor that triggers amyloid-β(Aβ) phagocytosis via TYROBP. Objective: To analyze the impact of this copy-number variant in SIRPβ1 expression and how it affects AD molecular etiology. Methods: Copy-number variant proxy rs2209313 was evaluated in GERALD and GR@ACE longitudinal series. Hippocampal specimens of genotyped AD patients were also examined. SIRPβ1 isoform-specific phagocytosis assays were performed in HEK393T cells. Results: The insertion alters the SIRPβ1 protein isoform landscape compromising its ability to bind oligomeric Aβ and its affinity for TYROBP. SIRPβ1 Dup/Dup patients with mild cognitive impairment show an increased cerebrospinal fluid t-Tau/Aβ ratio (p=0.018) and a higher risk to develop AD (OR=1.678, p=0.018). MRIs showed that Dup/Dup patients exhibited a worse initial response to AD. At the moment of diagnosis, all patients showed equivalent Mini-Mental State Examination scores. However, AD patients with the duplication had less hippocampal degeneration (p<0.001) and fewer white matter hyperintensities. In contrast, longitudinal studies indicate that patients bearing the duplication allele show a slower cognitive decline (p=0.013). Transcriptional analysis also shows that the SIRPβ1 duplication allele correlates with higher TREM2 expression and an increased microglial activation. Conclusions: The SIRPβ1 internal duplication has opposite effects over MCI-to-Dementia conversion risk and AD progression, affecting microglial response to Aβ. Given the pharmacological approaches focused on the TREM2-TYROBP axis, we believe that SIRPβ1 structural variant might be considered as a potential modulator of this causative pathway.
Original language | English |
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Pages (from-to) | 601-618 |
Number of pages | 18 |
Journal | Journal of Alzheimer's Disease |
Volume | 98 |
Issue number | 2 |
DOIs | |
State | Published - Mar 19 2024 |
Bibliographical note
Publisher Copyright:© 2024-IOS Press. All rights reserved.
Keywords
- Alzheimer's disease
- DAP12
- SIRPβ1
- TREM2
- TYROBP
- copy-number variant
- microglia
ASJC Scopus subject areas
- General Neuroscience
- Clinical Psychology
- Geriatrics and Gerontology
- Psychiatry and Mental health