PROJECT SUMMARY
Alzheimer's disease (AD) is the most common form of dementia and the fifth leading cause of death for those
age 65 and older. Costs of care for individuals with AD are substantial: total payments in 2022 are estimated at
$321 billion, and costs will increase by $1 billion each year. AD risk factors include age, sex, and genetics. Of
Americans living with AD, 4 million are women and 2.5 million are men, and the apolipoprotein E (APOE) -e4
allele is the most important genetic risk factor for sporadic AD. In addition, female APOE-e4 carriers are more
likely to progress from mild cognitive impairment (MCI) to AD, have more brain atrophy and memory loss, and
develop AD more frequently than age matched males. Hallmark features of AD include the buildup of amyloid
beta (Aß) and abnormal phosphorylation of Tau, resulting in plaques and neurofibrillary tangles in the brain.
Importantly in AD, disruptions to extracellular vesicle (EV) biogenesis result in altered EV miRNA and protein
cargo, and neuronal EVs in AD contain and propagate both Aß and Tau. Our previous studies identified
miRNAs in human cerebrospinal fluid (CSF) from living donors that discriminate AD patients from healthy
control (CTL) participants, and we found that combining CSF miRNAs plus CSF Aß42:total Tau measurements
improves classification of AD and MCI vs. CTL. In the studies proposed herein, we focus on the utility of CSF
EVs and their cargo as more robust biomarkers for AD, that show distinct differences in females vs. males and
those with the APOE-e4 vs. APOE-e3 genotype. Our pilot data in human CSF EVs and postmortem brain
shows that: i) the size of membranous particles is larger in AD vs. CTL CSF; ii) CSF EVs have surface marker
proteins that are unique to AD and/or Parkinson's disease (PD) vs. CTL; iii) CSF EV miRNAs have improved
predictive power for AD vs. total CSF; iv) CSF EV miRNAs show sex and APOE dependent changes in
expression; v) there is increased miR-16-5p in female AD CSF EVs vs. CTL; and vi) a predicted gene target of
miR-16-5p, SNAP-25, is decreased in female AD hippocampus. Together, these studies support that sex and
APOE-e4 both contribute to changes in AD CSF EVs, which may account in part for the higher prevalence of
AD in females, and the increased risk for AD in people with the APOE-e4 genotype. Thus, we propose to
establish the physical features and molecular cargo of AD CSF EVs vs. CTL, within the context of sex and
APOE genotype. We will use our Information Theory method to identify the strongest dependencies that can
distinguish AD from PD from CTL, and to identify candidate biomarkers for high-risk AD. We include male and
female PD to identify CSF EV surface markers and cargo that are unique from AD. We will then identify and
verify gene targets of CSF EV miRNAs that are relevant to AD. Together, our studies will establish specific
biomarkers for AD by combining the physical features, surface marker profiles, miRNAs, and proteins in CSF
EVs. They will also establish the neurologically relevant gene targets of AD EV miRNAs in human brain, which
may contribute to the processes underlying AD pathogenesis and serve as novel therapeutic targets for AD.
