Biology subjects

Orr, M. E.

Publications and source records attributed to Orr, M. E..

4 recordsLinked to original sources

bioRxiv2025

Single-cell Spatial Transcriptional Profiling Uncovers Heterogeneous Cellular Responses to Pathogenic Tau in a Mouse Model of Neurodegeneration

Intracellular tau accumulation contributes to neurodegeneration and systemic dysfunction. Although tau primarily aggregates in neurons as neurofibrillary tangles (NFTs), it also affects other cell types through poorly understood mechanisms. To define the molecular characteristics of tangle-bearing neurons and their influence on surrounding cells, we used CosMx SMI to evaluate the expression of 950 genes in more than 265,000 cells from rTg(tauP301L)4510 tauopathy and control mouse brains. In the cerebral cortex, tau pathology disrupted the excitatory-inhibitory neuron balance and altered pathways critical for myelination, similar myelin changes were observed in postmortem brain tissue from patients with progressive supranuclear palsy. In the hypothalamus, tau accumulation was associated with transcriptional changes linked to pathways involved in body weight and metabolic regulation. These findings reveal molecular mechanisms underlying both cell-autonomous and non-autonomous effects of tauopathy and identify targets for further investigation into tau pathogenesis and its systemic impact.

neuroscience↗

bioRxiv2025

Spatial Multi-Omics Workflow and Analytical Guidelines for Alzheimer's Neuropathology

Spatial biology technologies enable high-dimensional profiling within intact tissues, revealing how molecular and cellular organization drives function and disease. As these platforms gain broader adoption, standardized analytical frameworks are needed to ensure data quality and reproducibility. Here, we present an end-to-end pipeline for the GeoMx Digital Spatial Profiler that simultaneously generates whole-transcriptome and 637-protein measurements from user-defined regions within the same tissue sections. The workflow integrates morphology-guided region selection, quality control, normalization, and multi-modal data interpretation. Applied to formalin-fixed cortical tissues from Alzheimers disease, dementia with Lewy bodies, amyotrophic lateral sclerosis, and controls, the framework resolves spatially distinct molecular domains. Transcript and protein signals diverge across amyloid plaque cores and surrounding glial-rich regions, with RNA-protein concordance varying by disease condition, while single-neuron profiling with and without pathogenic tau deposition illustrates protein assay sensitivity. This dataset provides a rigorously validated resource for spatial multi-omic analyses and establishes broadly applicable guidelines for reliable, reproducible profiling of complex tissues.

neuroscience↗

bioRxiv2025

HypoAD: volumetric and single-cell analysis reveals changes in the human hypothalamus in aging and Alzheimer's disease

Alterations in metabolism, stress response, sleep, circadian rhythms, and neuroendocrine processes are key features of aging and neurodegeneration. These fundamental processes are regulated by the hypothalamus, yet how its functionally distinct subregions and cell types change during human aging and Alzheimers Disease (AD) remains largely unexplored. Here, we present HypoAD, a comprehensive atlas of the human hypothalamus in aging and AD, integrating high-resolution MRI from 202 individuals with single-nucleus RNA-seq (snRNA-seq) of 614,403 nuclei from young, AD, and age-matched non-dementia controls. Our analysis reveals that hypothalamic subregions governing metabolism, stress, and circadian rhythms are particularly vulnerable, exhibiting significant changes in both volumes and gene expression during aging and AD. At the molecular level, machine learning models identified the inflammatory response and regulators of circadian rhythms as key cellular predictors of AD. These signatures were reflected in specific cell types: microglia transitioned to a pro-inflammatory state, while inhibitory neurons within sleep-and circadian-regulating hypothalamic subregions showed the most profound transcriptional alterations, including disruptions in ligand-receptor interactions and G-protein-coupled receptor signaling. Together, HypoAD provides a high-resolution volumetric map and a comprehensive transcriptomic atlas of the human hypothalamus in aging and AD, linking lifestyle and behavioral changes to their underlying volumetric and molecular pathways. Additionally, HypoAD provides a framework to investigate hypothalamic dysfunction and establishes a roadmap for targeted interventions aimed at mitigating physiological disruptions to potentially slow disease progression.

neuroscience↗

bioRxiv2018

Tau protein aggregation induces cellular senescence in the brain.

Tau protein accumulation is the most common pathology among degenerative brain diseases, including Alzheimers disease (AD), progressive supranuclear palsy (PSP), traumatic brain injury (TBI) and over twenty others1. Tau-containing neurofibrillary tangle (NFT) accumulation is the closest correlate with cognitive decline and cell loss, yet the mechanisms mediating tau toxicity are poorly understood. NFT-containing neurons do not die, which suggests secondary mechanisms are driving toxicity2. We evaluated gene expression patterns of NFT-containing neurons microdissected from AD patient brains3 and found they develop an expression profile consistent with cellular senescence described in dividing cells. This complex stress response induces a near permanent cell cycle arrest, adaptations to maintain survival, cellular remodeling, and metabolic dysfunction4. Moreover, senescent cells induce chronic degeneration of surrounding tissue through the secretion of pro-inflammatory, pro-apoptotic molecules termed the senescence-associated secretory phenotype (SASP)5. Using transgenic mouse models of tau-associated pathogenesis we found that NFTs induced a senescence-like phenotype including DNA damage, karyomegaly, mitochondrial dysfunction and SASP. Cdkn2a transcript level, a hallmark measure of senescence, directly correlated with brain atrophy and NFT load. This relationship extended to postmortem brain tissue from humans with PSP to indicate a phenomenon common to tau toxicity. Tau transgenic mice with late stage pathology were treated with senolytics to remove senescent cells. Despite the advanced age and disease progression, senolytic treatment reduced total NFT burden, neuron loss and ventricular enlargement; and normalized cerebral blood flow to that of non-transgenic control mice. Collectively, these findings indicate that NFTs induce cellular senescence in the brain, which contributes to neurodegeneration and brain dysfunction. Moreover, given the prevalence of tau protein deposition among neurodegenerative diseases, these findings have broad implications for understanding, and potentially treating, dozens of brain diseases.

neuroscience↗