iPSC-Derived Microglia for Modeling Human-Specific DAMP and PAMP Responses in the Context of Alzheimer's Disease
Ivanna Ihnatovych1, Barbara Birkaya1, Emily Notari1
1Department of Neurology, State University of New York at Buffalo, 875 Ellicott St., Buffalo, NY 14203, USA.
Abstract:
Neuroinflammation in Alzheimer's disease (AD) has been the focus for identifying targetable pathways for drug development. The role of amyloid beta (Aβ), a prototype of damage-associated molecular patterns (DAMPs), has been implicated in triggering an inflammatory response. As alpha7 nicotinic acetylcholine receptor (α7 nAChR) binds Aβ with high affinity, α7 nAChR may play a role in Aβ-induced neuroinflammation. The conundrum of how α7 nAChR as the mediator of the cholinergic anti-inflammatory response may trigger an inflammatory response has not been resolved. CHRFAM7A, the uniquely human fusion gene between ULK4 and CHRNA7, is a negative regulator of α7 nAChR ionotropic function. To provide the human context, isogenic induced pluripotent stem cell (iPSC) lines were developed from CHRFAM7A null and carrier individuals by genome-editing the null line using TALENs to knock-in CHRFAM7A. In iPSC-derived microglia-like cells, CHRFAM7A mitigated Aβ uptake through the α7 nAChR. Despite the lower Aβ uptake, the presence of CHRFAM7A was associated with an innate immune response that was characterized by NF-κB activation and NF-κB target transcription (TNFA, IL6, and IL1B). LPS, a prototype PAMP, induced a heightened immune response in CHRFAM7A carriers. CHRFAM7A modified the dynamics of NF-κB translocation by prolonging its nuclear presence. CHRFAM7A modified the α7 nAChR metabotropic function, resulting in a human-specific innate immune response. This iPSC model provided an opportunity to elucidate the mechanism and establish high throughput screens.
Insights
The human gene CHRFAM7A regulates alpha7 nicotinic acetylcholine receptor function, impacting amyloid-beta uptake and neuroinflammation in Alzheimer's disease models. This study reveals a human-specific immune response mechanism.
Area of Science:
- Neuroscience
- Immunology
- Genetics
Background:
- Neuroinflammation is a key factor in Alzheimer's disease (AD) pathogenesis, with amyloid-beta (Aβ) triggering inflammatory responses.
- The alpha7 nicotinic acetylcholine receptor (α7 nAChR) binds Aβ and is implicated in both anti-inflammatory and inflammatory pathways, creating a research conundrum.
- The human-specific fusion gene CHRFAM7A negatively regulates α7 nAChR ionotropic function.
Purpose of the Study:
- To investigate the role of CHRFAM7A in Aβ-induced neuroinflammation using human isogenic induced pluripotent stem cell (iPSC) lines.
- To elucidate the mechanism by which CHRFAM7A modulates α7 nAChR function and its impact on the innate immune response.
- To establish a human iPSC-derived microglia model for studying neuroinflammation and developing high-throughput screens.
Main Methods:
- Genome-editing using TALENs to create isogenic iPSC lines from CHRFAM7A null and carrier individuals.
- Differentiation of iPSCs into microglia-like cells to study Aβ uptake and immune responses.
- Analysis of NF-κB activation, target gene transcription (TNFA, IL6, IL1B), and lipopolysaccharide (LPS)-induced responses.
Main Results:
- CHRFAM7A mitigated Aβ uptake via α7 nAChR in iPSC-derived microglia.
- Despite reduced Aβ uptake, CHRFAM7A presence correlated with an enhanced innate immune response, including NF-κB activation and prolonged nuclear translocation.
- CHRFAM7A carriers exhibited a heightened immune response to LPS and modified α7 nAChR metabotropic function, indicating a human-specific inflammatory mechanism.
Conclusions:
- CHRFAM7A plays a critical role in modulating the human-specific innate immune response in the context of Aβ exposure and neuroinflammation.
- The study highlights CHRFAM7A's influence on α7 nAChR function, contributing to a complex inflammatory profile in Alzheimer's disease.
- The developed iPSC model offers a valuable platform for mechanistic studies and high-throughput screening for AD therapeutics.
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