Biology subjects

Stern, A. M.

Publications and source records attributed to Stern, A. M..

7 recordsLinked to original sources

bioRxiv2026

Aβ Aggregates Bind the U1 Spliceosomal Ribonucleoprotein in Alzheimer Disease Brain

Missplicing due to U1 small nuclear ribonucleoprotein (U1 snRNP) insolubilization and dysfunction has been identified in Alzheimer disease (AD) brain. Cytoplasmic aggregation and mislocalization of the U1 snRNP partly co-localizes with tau neurofibrillary tangles, and some evidence for tau-U1 binding has been identified. However, tau-U1 co-localization by immunohistochemistry is only partial, and insoluble U1 small nuclear RNA (snRNA) binding proteins correlate better with A{beta} than with tau in unbiased proteomics. While investigating the sedimentation characteristics of A{beta} aggregates capable of diffusing out of AD brain tissue, we unexpectedly found that some were bound to small RNA. A{beta} immunoprecipitation and deep sequencing revealed the U1 snRNA, with specific binding confirmed through reverse immunoprecipitation and oligonucleotide hybridization. Double immunoelectron microscopy revealed decoration of A{beta} fibrils, more than tau fibrils, with the U1-70k protein, a component of the U1 snRNP. Immunofluorescence of unfixed cryostat sections but not formalin fixed paraffin embedded sections of AD brain revealed labeling of a subset of amyloid plaques with anti-U1-70k antibodies, confirmed by RNA in situ hybridization of the U1 snRNA. We conclude that a subset of AD brain A{beta} aggregates are bound to the U1 snRNP at the edges of some amyloid plaques, explaining prior proteomics findings. These data provide a potential link between A{beta} aggregation and spliceosome dysfunction and unite A{beta} with other fibril-forming proteins across the neurodegenerative diseases whose aggregation is affected by RNA binding.

neuroscience↗

bioRxiv2025

Recapitulation of clinical and molecular hallmarks of lipid-induced hepatic insulin resistance in a zonated, vascularized human liver acinus microphysiological system during metabolic dysfunction-associated steatotic liver disease (MASLD) progression

Metabolic dysfunction-associated steatotic liver disease (MASLD) impacts ca. 30% of the global population and is very heterogeneous making it a challenge to produce therapeutics. The heterogeneity arises from genetics, co-morbidities, the microbiome and lifestyle. To help address this challenge, we have refined the human vascularized liver acinus microphysiological system (vLAMPS), which provides an all-human platform for drug development, in line with recently updated federal requirements for the use of New Approach Methodologies (NAMs). By introducing clinically relevant media perturbations and employing several diverse and reproducible in situ and systemic measurements, we show that the vLAMPS can recapitulate key structural and functional aspects of normal physiology, acinus zonation, and all stages of MASLD progression including stellate cell activation and fibrosis. Importantly, in this study we also demonstrate that several hallmarks of lipid-induced hepatic insulin resistance paralleled MASLD progression. These included diminution of insulin receptor substrate 2 (IRS2) protein, compromised insulin receptor mediated insulin clearance, enhanced pericentral lipid accumulation, increased VLDL secretion, and enhanced hepatic glucose output mediated by increased periportal nuclear translocation of FOXO1. These results suggest that the mechanisms underlying MASLD progression in vLAMPS are clinically relevant and support the tenable hypothesis that the hepatic insulin resistant state plays both a causal and consequential role in a vicious cycle driving disease progression.

bioengineering↗

bioRxiv2025

Anti-amyloid antibody equilibrium binding to Aβ aggregates from human Alzheimer disease brain

ImportanceAnti-amyloid immunotherapy is used to treat Alzheimer disease (AD) with moderate benefits and potentially serious side effects due to amyloid related imaging abnormality with effusions/edema (ARIA-E). Different anti-amyloid antibodies have different in vitro binding characteristics to different synthetic A{beta} aggregates, leading to the assumption that they bind different species in the human brain. Lecanemab is hypothesized to bind "protofibrils," but these are not well-characterized in human brain. It is also unknown how binding differences correlate with ARIA-E rates. The APOE {varepsilon}4 allele increases ARIA-E risk, but how it affects antibody binding characteristics is unknown. ObjectivesTo determine whether anti-amyloid antibodies bind different species of human brain A{beta} and whether these binding properties to human brain A{beta} explains ARIA-E rates. DesignCross-sectional study of 18 postmortem human brains. SettingSingle tertiary care hospital. ParticipantsDeceased patients with AD and cerebral amyloid angiopathy (CAA). Main Outcomes and MeasuresEquilibrium binding constants (KD) and total A{beta} binding (Bmax) of recombinant aducanumab, lecanemab, and donanemab equivalents to human brain soluble and insoluble amyloid plaque-enriched and CAA-enriched A{beta} aggregates. ResultsLecanemab did not bind with greater affinity to the soluble fraction of A{beta} compared to aducanumab. All three antibodies were bound essentially identical quantities of A{beta} across the 18 cases and fractions (Pearsons r 0.84 - 0.97). Antibody preference for plaque vs CAA A{beta} did not differ in soluble fractions but differed slightly in insoluble extracts. The APOE {varepsilon}4 allele led to a more soluble antibody-accessible A{beta} pool in a dose-dependent manner for all three antibodies. Conclusions and RelevanceThe lecanemab binding target in human brain is unlikely to be distinctly "protofibrillar" compared to other antibodies. Differences in antibody preference for plaque vs CAA A{beta} are unlikely to fully explain differences in ARIA-E rates. The APOE {varepsilon}4 allele may plausibly increase ARIA-E risk by making antibody-accessible A{beta} more soluble. These results have implications for improving the safety and efficacy of current and future anti-amyloid antibody therapies.

neuroscience↗

bioRxiv2024

A metabolic-dysfunction associated steatotic liver acinus biomimetic induces pancreatic islet dysfunction in a coupled microphysiology system

Preclinical and clinical studies suggest that lipid-induced hepatic insulin resistance is a primary defect that predisposes to dysfunction in pancreatic islets, implicating a perturbed liver-pancreas axis underlying the comorbidity of T2DM and MASLD. To investigate this hypothesis, we developed a human biomimetic microphysiological system (MPS) coupling our vascularized liver acinus MPS (vLAMPS) with primary islets on a chip (PANIS) enabling MASLD progression and islet dysfunction to be quantitatively assessed. The modular design of this system (vLAMPS-PANIS) allows intra-organ and inter-organ dysregulation to be deconvoluted. When compared to normal fasting (NF) conditions, under early metabolic syndrome (EMS) conditions, the standalone vLAMPS exhibited characteristics of early stage MASLD, while no significant differences were observed in the standalone PANIS. In contrast, with EMS, the coupled vLAMPS-PANIS exhibited a perturbed islet-specific secretome and a significantly dysregulated glucose stimulated insulin secretion (GSIS) response implicating direct signaling from the dysregulated liver acinus to the islets. Correlations between several pairs of a vLAMPS-derived and a PANIS-derived secreted factors were significantly altered under EMS, as compared to NF conditions, mechanistically connecting MASLD and T2DM associated hepatic factors with islet-derived GLP-1 synthesis and regulation. Since vLAMPS-PANIS is compatible with patient-specific iPSCs, this platform represents an important step towards addressing patient heterogeneity, identifying complex disease mechanisms, and advancing precision medicine.

bioengineering↗

bioRxiv2024

Comparison of Wild-Type and High-risk PNPLA3 variants in a Human Biomimetic Liver Microphysiology System for Metabolic Dysfunction-associated Steatotic Liver Disease Precision Therapy

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a worldwide health epidemic with a global occurrence of approximately 30%. The pathogenesis of MASLD is a complex, multisystem disorder driven by multiple factors including genetics, lifestyle, and the environment. Patient heterogeneity presents challenges for developing MASLD therapeutics, creation of patient cohorts for clinical trials and optimization of therapeutic strategies for specific patient cohorts. Implementing pre-clinical experimental models for drug development creates a significant challenge as simple in vitro systems and animal models do not fully recapitulate critical steps in the pathogenesis and the complexity of MASLD progression. To address this, we implemented a precision medicine strategy that couples the use of our liver acinus microphysiology system (LAMPS) constructed with patient-derived primary cells. We investigated the MASLD-associated genetic variant PNPLA3 rs738409 (I148M variant) in primary hepatocytes, as it is associated with MASLD progression. We constructed LAMPS with genotyped wild type and variant PNPLA3 hepatocytes together with key non-parenchymal cells and quantified the reproducibility of the model. We altered media components to mimic blood chemistries, including insulin, glucose, free fatty acids, and immune activating molecules to reflect normal fasting (NF), early metabolic syndrome (EMS) and late metabolic syndrome (LMS) conditions. Finally, we investigated the response to treatment with resmetirom, an approved drug for metabolic syndrome-associated steatohepatitis (MASH), the progressive form of MASLD. This study using primary cells serves as a benchmark for studies using "patient biomimetic twins" constructed with patient iPSC-derived liver cells using a panel of reproducible metrics. We observed increased steatosis, immune activation, stellate cell activation and secretion of pro-fibrotic markers in the PNPLA3 GG variant compared to wild type CC LAMPS, consistent with the clinical characterization of this variant. We also observed greater resmetirom efficacy in PNPLA3 wild type CC LAMPS compared to the GG variant in multiple MASLD metrics including steatosis, stellate cell activation and the secretion of pro-fibrotic markers. In conclusion, our study demonstrates the capability of the LAMPS platform for the development of MASLD precision therapeutics, enrichment of patient cohorts for clinical trials, and optimization of therapeutic strategies for patient subgroups with different clinical traits and disease stages.

cell biology↗

bioRxiv2022

Abundant Aβ fibrils in ultracentrifugal supernatants of aqueous extracts from Alzheimer's disease brains

Soluble aggregates of amyloid-{beta} (A{beta}), often called oligomers, are believed to be principal drivers of neurotoxicity, spreading of pathology, and symptoms in Alzheimers disease (AD), but little is known about their structures in human brain. A{beta} oligomers have been defined as aggregates found in supernatants following ultracentrifugation of aqueous extracts. We now report the unexpected presence of abundant A{beta} fibrils in high-speed supernatants from AD brains that were extracted by soaking in aqueous buffer. The fibrils did not appear to form during extract preparation, and their numbers by EM correlated with ELISA quantification of aggregated A{beta}42. Cryo-EM structures of A{beta} fibrils from aqueous extracts were identical to those from sarkosyl-insoluble AD brain homogenates. The fibrils in aqueous extracts were immunolabeled by lecanemab, an A{beta} aggregate-directed antibody reported to improve cognitive outcomes in AD. We conclude that A{beta} fibrils are abundant in aqueous extracts from AD brains and have the same structures as those from amyloid plaques. These findings have implications for understanding the nature of A{beta} oligomers and for designing oligomer-preferring therapeutic antibodies.

neuroscience↗

bioRxiv2019

A spatial analytics computational and systems biology platform predicts risk of colorectal cancer recurrence and identifies emergent spatial domain networks associated with recurrence

An unmet clinical need in solid tumor cancers is the ability to harness the intrinsic spatial information in primary tumors that can be exploited to optimize prognostics, diagnostics and therapeutic strategies for precision medicine. We have developed a transformational spatial analytics (SpAn) computational and systems biology platform that predicts clinical outcomes and captures emergent spatial biology that can potentially inform therapeutic strategies. Here we apply SpAn to primary tumor tissue samples from a cohort of 432 chemo-naive colorectal cancer (CRC) patients iteratively labeled with a highly multiplexed (hyperplexed) panel of fifty-five fluorescently tagged antibodies. SpAn predicted the 5-year risk of CRC recurrence with a mean area under the ROC curve of 88.5% (SE of 0.1%), significantly better than current state-of-the-art methods. SpAn also inferred the emergent network biology of the tumor spatial domains revealing a synergistic role of known features from CRC consensus molecular subtypes that will enhance precision medicine.

cancer biology↗