Lisa M. Ellerby

Pericytes are critical for maintaining blood-brain barrier (BBB) integrity and have emerged as key contributors to Alzheimer’s disease (AD) pathogenesis. Although the apolipoprotein E2 (APOE2) allele is associated with reduced AD risk and increased longevity, its impact on pericyte function is unclear. We measured pericyte density in the brains of humanized APOE2, APOE3, and APOE4 knock-in mice and found that APOE2 mice revealed increased pericyte markers and enhanced BBB integrity. To uncover the underlying mechanisms, we used CRISPR/Cas9 editing to generate isogenic human iPSC-derived pericytes carrying APOE2, APOE3, or APOE4 alleles. All lines expressed pericyte markers in an APOE allele-dependent levels. Using a human in vitro BBB model incorporating endothelial cells, astrocytes, and genotype-specific pericytes, we found that APOE2 pericytes provided greater overall cerebral barrier integrity. Further, APOE2 pericytes exhibited increased resistance to senescence and reduced amyloid-β accumulation. Using unbiased proteomic profiling to understand these cellular phenotypes, we found significant alterations in lipid metabolism-related proteins. Untargeted lipidomic analysis confirmed a genotype-specific lipid signature, observing reduced phospholipids and increased triglycerides in APOE2 pericytes. Interestingly, APOE2 pericytes showed lower lipid droplet (LD) accumulation. Proteomics analysis revealed increased expression of proteins involved in lipid degradation, β-oxidation, and lipid transport, suggesting more efficient lipid processing. Notably, recombinant APOE2 treatment effectively rescued pericyte function and mitigated LD accumulation in APOE3 and APOE4 pericytes. Collectively, these findings demonstrate that APOE2 expression supports pericyte functionality through increased lipid processing, providing mechanistic insight into the cerebrovascular protective effects of APOE2 in pericytes. These findings could be translated into novel therapies aimed at enhancing pericyte function and lipid metabolism, particularly in individuals at risk for neurodegenerative diseases.

Acoustic droplet ejection (ADE) enables nanoliter-scale liquid handling for complex microplate assays, yet translating experimental designs into validated, instrument-ready instructions remains a bottleneck. We present PickliPy, an open-source framework that converts spreadsheet-based assay designs into validated ADE picklists. PickliPy.Assay supports combinatorial, dose-response, and multi-addition time-course dispensing, while PickliPy.Screen extends to high-throughput workflows, including library reformatting and shortlisting. Across biological contexts, the framework generated reproducible, assay-ready plates and standardized execution in human cohort studies. Acoustic pre-dispensing deepened bioenergetic phenotyping of human skeletal muscle mitochondria, capturing substrate switching and sharpened dose-response precision in human pancreatic β-cells, revealing an age-associated change in succinate dehydrogenase kinetics. We benchmarked a wash-free, live-cell screen of mitochondrial function and morphology, in which deep-learning image analysis widened the assay window, and ADE enabled integrative dose-response co-response analysis. These tools, including their agentic use, make complex ADE experiments easier to design and scale from single benches to screening campaigns.

Progressive cognitive decline and loss of white matter integrity are observed during aging, but whether these two processes are connected remains unclear. We propose the Decoherence via Demyelination Hypothesis (DDH) as a mechanism linking non-uniform, tract-specific myelin loss during aging, which results in the degradation of conduction timing that is required to coordinate long-range neuronal assemblies. This impairs the dynamic assembly of task-dependent functional networks and promotes age-associated cognitive change. Axonal myelination determines conduction velocity as well as signal transmission fidelity, properties essential for phase-locked integration of long-distance inputs with local oscillations and for the assembly of mesoscale functional brain networks. If myelin loss is heterogeneous across tracts, the resulting timing perturbations should be heterogeneous as well, with disproportionate impact on networks supporting higher-order cognition. To test this, we analyzed structural and microstructural MRI in 638 individuals aged 40–99, quantifying fasciculation in different white matter pathways as well as neurite orientation dispersion and density imaging (NODDI) to the gray–white matter interface beneath cortical regions. We observed tract-specific, non-uniform myelin decline, with significant nonlinear losses in tracts serving high order cognition and memory (uncinate fasciculus, fornix, corpus callosum), consistent with accelerated late-life vulnerability in pathways implicated in cognitive aging and increased risk for neurodegenerative diseases. Tract-level degeneration tracked with age-related shifts in network organization and cognition. These findings may support DDH as a framework for age-associated cognitive change. Particularly, tract-specific timing perturbations drive the breakdown of coordinated network activity in aging.

Genome‐wide association studies (GWAS) have identified APOE2 allele as linked to exceptional longevity, with carriers exhibiting a reduced risk of Alzheimer's disease (AD). Apolipoprotein E (APOE), a glycoprotein involved in lipid transport, has three major alleles. However, alterations in lipid metabolism alone do not fully explain APOE2's protective effects. In contrast, APOE4 is the strongest genetic risk factor for AD. To investigate how APOE2 promotes neuronal longevity and confers neuroprotection, we generated human isogenic APOE iPSC‐derived models of both inhibitory GABAergic and excitatory neurons. In GABAergic neurons, APOE alleles differentially influenced endogenous DNA damage, DNA repair, and neuronal motility. Single‐cell RNA sequencing revealed APOE4 ‐specific gene expression signatures associated with AD, whereas APOE2 GABAergic neurons were enriched for DNA repair and signaling pathways. Consistent with this, APOE2 neurons exhibited significantly lower levels of DNA damage. APOE4 GABAergic neurons exhibit increased expression of repetitive ribosomal RNA, which is associated with DNA damage and cellular senescence. To determine whether the effects extended to excitatory neurons, we used a separate human model of Ngn2‐induced glutamatergic neurons, and found that APOE2 excitatory neurons were more resistant to cellular senescence and DNA damage than isogenic APOE3 and APOE4 neurons. Similarly, we found human APOE2‐targeted replacement mice exhibited less nucleolar enlargement and increased nuclear Lamin A/C, Hmgb1, and H3K9me3 compared to APOE4 counterparts. Together, our findings identify DNA repair and suppression of senescence‐associated processes as key mechanisms by which APOE2 is associated with neuronal resilience, providing mechanistic insight into its association with exceptional longevity and protection against AD.

Individuals with Alzheimer's disease (AD) are at an increased risk of bone fracture, while osteoporosis in women is one of the earliest predictors of AD. Yet the mechanisms linking cognitive decline and skeletal deterioration remain poorly defined. Proteomic analysis of cortical bone from aged 21‐month‐old mice revealed strong enrichment of neurodegeneration‐associated proteins, including apolipoprotein E (Apoe) and amyloid precursor protein. Apoe localized specifically to osteocytes, with expression in aged female bone nearly twice that of young 4‐month‐old male bone. Because human APOE alleles confer different age‐related AD risks, we examined their roles in bone using humanized APOE2, APOE3, and APOE4 knock‐in mice and analyzed bone and hippocampus from the same animals. APOE4 produced marked sex‐specific effects on the bone transcriptome and proteome compared with APOE2 or APOE3. Strikingly, APOE4‐associated proteomic disruptions were stronger in female bone than in the hippocampus. Functionally, APOE4 caused bone fragility in females without altering cortical structure. These deficits stemmed from impaired osteocyte perilacunocanalicular remodeling. Our findings identify APOE4 as a molecular driver of early osteocyte dysfunction and reduced bone quality, disproportionately affecting females. These findings highlight osteocytes as potential targets for early diagnosis of age‐related cognitive impairment and treatment for bone fragility, in females.

Background: Chronic low back pain, commonly associated with intervertebral disc (IVD) degeneration, is highly prevalent in patients with Alzheimer's disease (AD), and the severity of the pain is correlated with the severity of the dementia. While incidences of both afflictions increase dramatically in the elderly population, it is unknown whether AD exacerbates the health of the IVD. Aims: The aim of this study is to examine how AD‐related mutations affect the structure and mechanics of the IVD. Materials and Methods: Utilizing one‐year‐old male and female 5xFAD mice that constitutively express human APP and PSEN1 transgenes with five AD‐linked mutations, we measured the lumbar IVD's extracellular matrix composition, the three‐dimensional structure, histopathological degeneration, and mechanical behaviour. Results: The amount of collagen, glycosaminoglycans, and advanced glycation end‐products in the IVD did not differ in the 5xFAD animals. Likewise, the 5xFAD IVDs were not histopathologically degenerated. However, the IVD volume, measured by contrast‐enhanced microCT, was larger in the 5xFAD animals ( p = 0.046; 1–β = 0.53; Cohen's d = 1.19). Morphologically, the 5xFAD IVD heights were homogeneous and flatter than the WT IVDs ( p = 0.043; 1–β = 0.60; Cohen's d = 1.41). Finally, dynamic micro compression revealed that 5xFAD IVDs have higher loss tangent ( p = 0.0062; 1–β = 0.85; Cohen's d = 1.60) and greater energy dissipation ( p = 0.0379; 1–β = 0.55; Cohen's d = 1.21). Discussion: Shifts in viscoelastic behaviour and disc morphology are associated with early tissue degradation and affect the IVD's ability to efficiently recover from mechanical loading, predisposing the IVD to eventual degeneration. Conclusion: This work suggests that IVD's structure, morphology, and mechanics are affected by AD. Future work will focus on defining the molecular mechanisms of these changes in the IVD and their consequences in individuals with AD.

Huntington’s disease is an autosomal dominant neurodegenerative disease with a well-characterized genetic aetiology of a CAG expansion mutation in the huntingtin (HTT) gene, yet it remains without a cure. The hallmark of Huntington’s disease is the accumulation of intraneuronal aggregates of mutant HTT protein and polyglutamine (polyQ)-containing fragments, which causes impaired proteostasis and is an important Huntington’s disease therapeutic target. Aggregate-prone protein clearance primarily occurs through the autophagy-lysosome pathway and the ubiquitin-proteasome system, both of which can be modulated by deubiquitinating enzymes (DUBs). This study investigates the role of the DUB ubiquitin C-terminal hydrolase L3 (UCHL3) in modulating polyQ-mediated aggregation and toxicity. UCHL3 has previously been identified as a potential therapeutic target in cancer. We used Huntington’s disease models, including primary mouse neurons, patient fibroblasts and patient-derived medium spiny neurons, which are the most vulnerable to HTT polyQ toxicity. Genetic lowering of UCHL3 decreased polyQ aggregates and increased autophagosome-lysosome fusion events. This was accompanied by STAT3 induction, which protects against neuronal proteotoxic stress. Furthermore, treatment with a small-molecule inhibitor of UCHL3 recapitulated the effects of UCHL3 lowering and attenuated pathological markers in Huntington’s disease medium spiny neurons. These results provide a foundation for further exploration of UCHL3 inhibitors in the context of Huntington’s disease and underscore the biological connection between cancer and neurodegeneration for drug repurposing strategies.

Age-related cognitive decline represents a major and unresolved challenge of human aging. Here, we identify the NAD⁺-consuming enzyme CD38 as a central regulator of cognitive aging acting through a choroid plexus–cerebrospinal fluid (CSF)–hippocampus axis. CD38 expression increases with age and localizes primarily to pericytes in the choroid plexus, where it depletes NAD⁺, impairs mitochondrial function, and promotes cellular senescence. Genetic ablation or pharmacological inhibition of CD38 restores NAD⁺ levels, suppresses senescence markers, and improves choroid plexus function, resulting in a rejuvenated CSF proteomic and metabolomic profile characterized by reduced inflammatory signaling and enhanced neurotrophic support. These changes propagate to the hippocampus, reversing age-related transcriptional signatures and enhancing synaptic plasticity. A novel, brain-penetrant CD38 inhibitor, NTX-748, reproduced the benefits of CD38 deficiency—elevating systemic and brain NAD⁺ levels, improving long-term potentiation, and enhancing multiple domains of cognition in aged mice. Collectively, these findings identify the choroid plexus as a metabolic gatekeeper of brain aging and establish CD38 inhibition as a promising therapeutic strategy to promote cognitive resilience and healthy brain aging.