Citation

Objective: Investigate the MHC-I pathway in microglia as it relates to aging and AD and isolate
disease associated microglia to understand the role of this pathway and microglial phenotypes.
Design: To examine microglial MHC-I during the aging process, we used the Cx3cr1-NuTRAP
mouse line to collect microglial-specific RNA from mice of different ages for transcriptomic
analyses. Additionally, flow cytometry analysis and immunohistochemistry were used to confirm
our results at the proteomic level. With the regulation of microglial MHC-I in neurodegenerative
conditions, we wanted to investigate the potential involvement of MHC-I in disease associated
microglia (DAMs). While DAMs have been analyzed in single cell studies, we wanted a deeper,
more comprehensive analysis of their molecular phenotype, so we sorted DAMs by flow cytometry
before performing translatome profiling. To assess MHC-I function in neurodegeneration and
DAMs, we have developed a microglia-specific B2m knockout model with the goal to suppress
microglial MHC-I before and after development of neuroinflammation and reactive microglia.
These studies will need to tamoxifen (Tam) induce the knockout at young and old ages. To
compare the specificity and efficacy of Tam mediated cre recombination at various ages, we
induced Cx3cr1-NuTRAP mice at early or late ages and collected both young and old mice. For
this portion of experiments, RNA sequencing was used as an endpoint in addition to flow
cytometry and immunohistochemistry.
Results: The results of this project demonstrate: 1) there is consistent upregulation of MHC-I in
microglia with age in mice and humans and in clinical AD samples and a variety of mouse AD
models; 2) DAMs can be isolated and have mostly consistent phenotypes across conditions
(aging, AD, experimental autoimmune encephalomyelitis) with some important differences and;
3) different ages of Tam administration effectively induce cre recombination. We expand this data
to hypothesize that MHC-I has a role in microglial phenotypic switching in the brain.
Conclusions: The discovery of the increase of microglial MHC-I with aging and AD and DAMs
provides a novel pathway that may present new therapeutic avenues in future studies.