The gut microbiome in Alzheimer's disease: exploring the role of astrocytes

Project Summary
Alzheimer's disease (AD) is a progressive age-related neurodegenerative disorder which is currently the
6th leading cause of death in the United States, but there are currently no disease-modifying therapeutics.
Therefore, the development of mechanism-based therapeutics for AD is imperative. AD is characterized
pathologically by the presence of amyloid beta (Aβ)
genome-wide
as
release
are
(GMB)
that
the
been
hypothesize
abx-mediated
perturbation
and
in
via
eGFP
complement
assess
determine
can
antibiotics.
ingenuity
treatment
adeno-associated
regulator
inflammatory
plaques nd neurofibrillary tau tangles i n the brain. Recent
association studies point to neuroinflammation as a critical driver of Aβ and tau neuropathology
well as neurodegeneration. Reactive astrocytes have been shown to contribute to Aβ generation as well as
toxic substances that cause neurodegeneration. However, mechanisms governing astrocyte activation
not well understood. Recent studies indicate that antibiotic-mediated (abx) alterations in the gut microbiome
decrease microglial activation and decrease Aβ plaque load in the brain. It has previously been shown
reactive astrocytes are induced primarily by inflammatory factors released f rom activated microglia. Although
role of microglia has been explored in GMB mediated AD pathogenesis, the role of astrocytes has not yet
investigated. Because of the previously established connection between microglia and astrocytes, we
that abx will cause a eduction in reactive astrocyte induction.
In this project, I propose to investigate morphological and transcriptional changes in astrocytes following
microbiome perturbation. In Aim 1, I will assess the impac of antibiotic-mediated microbiome
on astrocyte morphology in APPPS1-21 (Appps1) mice using a combination of confocal imaging
3D-reconstruction of glial fibrillary acidic protein ( Gfap ) positive astrocytes near Aβ plaques. Furthermore,
Aim 1, I will tudy the transcriptional changes in astrocytes, by performing astrocyte-specific RNA sequencing
polysomal pull down by crossing Appps1 mice to the Aldh1l1EGFP/Rpl10 bacTRAP transgenic mice, i n which
is fused to ribosomal protein L10a under the control of the astrocyte-specific aldh1l1 promoter. We will
these data by performing single-cell RNA sequencing transcriptomics experiments where we can
astrocyte transcriptional heterogeneity. In Aim 2, I will utilize the same experimental approaches to
whether fecal matter transplant (FMT) from donor Appps1 mice back into abx-treated Appps1 mice
restore astrocyte phenotypes to those seen in Appps1 mice that were treated with water control instead of
In Aim 3, I will leverage transcriptional data from Aims 1 and 2 by performing gene ontology and
pathway analysis to determine which inflammatory pathways were the most altered by abx and FMT
and identify suspected master transcriptional regulator genes of these pathways. We will then design
vectors with Gfap promoter to transduce astrocytes in Appps1 mice with the identified master
genes and observe whether they increase Aβ load. Knockdown of these suspected astrocyte-specific
pathways could represent an important therapeutic strategy for AD.
a
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Grant Number: 5F30AG079577-04
NIH Institute/Center: NIH
Principal Investigator: Sidhanth Chandra