Biology subjects

Simms, J.

Publications and source records attributed to Simms, J..

7 recordsLinked to original sources

bioRxiv2026

Resilience to neuronal hyperactivity and restoration of the neuroimmune interactome by blocking fibrin-induced microglia activation in Alzheimers disease

Cerebrovascular pathology and neuronal network dysfunction are early features of Alzheimers disease (AD) associated with neuroinflammation and cognitive decline, but the vascular and immune triggers of neuronal hyperactivity remain largely unknown. Here, we show that the blood coagulation protein fibrin disrupts microglia-neuron interactions, promoting neuronal hyperactivity in an AD mouse model. Genetic elimination of the fibrin inflammatory domain reduced neuronal hyperactivity, restored dynamic microglial interactions with active neurons and protected from high-risk decision making in 5XFAD mice. Leveraging the transcriptional signatures of microglia and inhibitory and excitatory neurons, a ligand-receptor atlas revealed fibrin-dependent disruption of innate immune and glutamatergic signaling between microglia and neurons in AD mice. Patients with AD also showed a correlation of cerebrospinal fluid (CSF) fibrinogen levels with biomarkers of inflammation, vascular and synaptic dysfunction. Thus, resilience to neuronal hyperactivity and restoration of the neuroimmune interactome by targeting fibrin may have therapeutic implications for Alzheimers disease and related conditions. There is a companion manuscript submitted to bioRxiv (Lauderdale et al., 2026) HighlightsO_LIVascular-microglia axis drives neuronal hyperactivity C_LIO_LIFibrin inflammatory activity disrupts the microglia-neuron interactome C_LIO_LIMicroglia activation by fibrin impairs decision-making in AD mice C_LIO_LISynaptic dysfunction and immune biomarkers correlate with CSF fibrinogen in AD patients C_LI

neuroscience↗

bioRxiv2025

TOMM40 suppression promotes neuronal cholesterol imbalance and molecular and behavioral phenotypes of Alzheimer's disease

INTRODUCTIONWhile the APOE4 allele is a major risk factor for Alzheimers disease (AD), the role of TOMM40--an adjacent gene involved in mitochondrial protein import--is not known. METHODSMice, human iPSC-derived neurons (iNeurons), and human brain tissue were used for study of animal cognition, cholesterol metabolism, mitochondrial function, and gene expression. RESULTSTOMM40 knockdown (KD) impaired memory in mice and increased cholesterol and A{beta} 42 in mouse brains and human iNeurons. KD disrupted mitochondria-endoplasmic reticulum contact sites (MERCs), causing mitochondrial dysfunction and promoting reactive oxygen species that led to activation of LXRB (NR1H2), upregulation of APOE and LDLR. and increased cellular cholesterol and A{beta} 42 independent of APOE4. Human brain transcriptomics showed reduced TOMM40 expression that correlated with cholesterol regulatory gene expression, amyloid burden, and clinical AD diagnosis. DISCUSSIONTOMM40 is a novel mediator of AD pathology through dual effects on MERCs that regulate cholesterol homeostasis and mitochondrial function. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=163 SRC="FIGDIR/small/685963v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@e3e3e2org.highwire.dtl.DTLVardef@1861f67org.highwire.dtl.DTLVardef@77a813org.highwire.dtl.DTLVardef@1bb9a83_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2024

Data-driven discovery of cell-type-directed network-correcting combination therapy for Alzheimer's disease

Alzheimers disease (AD) is a multifactorial neurodegenerative disorder characterized by heterogeneous molecular changes across diverse cell types, posing significant challenges for treatment development. To address this, we introduced a cell-type-specific, multi-target drug discovery strategy grounded in human data and real-world evidence. This approach integrates single-cell transcriptomics, drug perturbation databases, and clinical records. Using this framework, letrozole and irinotecan were identified as a potential combination therapy, each targeting AD-related gene expression changes in neurons and glial cells, respectively. In an AD mouse model, this combination therapy significantly improved memory function and reduced AD-related pathologies compared to vehicle and single-drug treatments. Single-nuclei transcriptomic analysis confirmed that the therapy reversed disease-associated gene networks in a cell-type-specific manner. These results highlight the promise of cell-type-directed combination therapies in addressing multifactorial diseases like AD and lay the groundwork for precision medicine tailored to patient-specific transcriptomic and clinical profiles. Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=99 SRC="FIGDIR/small/627436v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@1e67fd5org.highwire.dtl.DTLVardef@1d2b779org.highwire.dtl.DTLVardef@10b6efforg.highwire.dtl.DTLVardef@1a44394_HPS_FORMAT_FIGEXP M_FIG C_FIG

systems biology↗

bioRxiv2024

The GluA1 cytoplasmic tail regulates intracellular AMPA receptor trafficking and synaptic transmission onto dentate gyrus GABAergic interneurons, gating response to novelty

The GluA1 subunit, encoded by the putative schizophrenia-associated gene GRIA1, is required for activity-regulated AMPA receptor (AMPAR) trafficking, and plays a key role in cognitive and affective function. The cytoplasmic, carboxy-terminal domain (CTD) is the most divergent region across AMPAR subunits. The GluA1 CTD has received considerable attention for its role during long-term potentiation (LTP) at CA1 pyramidal neuron synapses. However, its function at other synapses and, more broadly, its contribution to different GluA1-dependent processes, is poorly understood. Here, we used mice with a constitutive truncation of the GluA1 CTD to dissect its role regulating AMPAR localization and function as well as its contribution to cognitive and affective processes. We found that GluA1 CTD truncation affected AMPAR subunit levels and intracellular trafficking. {Delta}CTD GluA1 mice exhibited no memory deficits, but presented exacerbated novelty-induced hyperlocomotion and dentate gyrus granule cell (DG GC) hyperactivity, among other behavioral alterations. Mechanistically, we found that AMPAR EPSCs onto DG GABAergic interneurons were significantly reduced, presumably underlying, at least in part, the observed changes in neuronal activity and behavior. In summary, this study dissociates CTD-dependent from CTD-independent GluA1 functions, unveiling the GluA1 CTD as a crucial hub regulating AMPAR function in a cell type-specific manner.

neuroscience↗

bioRxiv2024

The effect of oxidative stress on the Adenosine A2a Receptor structure, activity and signalling

The adenosine 2a receptor (A2aR) is a G-protein coupled receptor that has important anti-inflammatory effects in response to some agonists and consequently is considered a therapeutic target. Its activity is affected by local membrane lipid environment and presence of certain phospholipid classes, so studies should be conducted using extraction methods such as styrene maleic acid co-polymers (SMA) that retain the local lipids. Currently, little is known about the effect of oxidative stress, which may arise from inflammation, on the A2aR. Therefore it was over-expressed in Pichia pastoris, SMA was used to extract the A2aR from cell membranes and its response to ligands was tested in the presence or absence of the radical initiator AAPH or reactive aldehyde acrolein. SMA-extracted A2aR was able to undergo conformational changes, measured by tryptophan fluorescence, in response to its ligands but oxidative treatments had no effect on the structural changes. Similarly, the treatments did not affect temperature-dependent protein unfolding. In contrast, in HEK293 cells expressing the A2aR, oxidative treatments increased cAMP levels in response to the agonist NECA, independently of adenylate cyclase activity. Thus, oxidative stress may be a homeostatic mechanism that abrogates inflammation via the A2aR signalling pathway. (max. 200 words - 194)

biochemistry↗

bioRxiv2024

CHCHD2 mutant mice display mitochondrial protein accumulation and disrupted energy metabolism

Mutations in the mitochondrial cristae protein CHCHD2 lead to a late-onset autosomal dominant form of Parkinsons disease (PD) which closely resembles idiopathic PD, providing the opportunity to gain new insights into the mechanisms of mitochondrial dysfunction contributing to PD. To begin to address this, we used CRISPR genome-editing to generate CHCHD2 T61I point mutant mice. CHCHD2 T61I mice had normal viability, and had only subtle motor deficits with no signs of premature dopaminergic (DA) neuron degeneration. Nonetheless, CHCHD2 T61I mice exhibited robust molecular changes in the brain including increased CHCHD2 insolubility, accumulation of CHCHD2 protein preferentially in the substantia nigra (SN), and elevated levels of -synuclein. Metabolic analyses revealed an increase in glucose metabolism through glycolysis relative to the TCA cycle with increased respiratory exchange ratio, and immune-electron microscopy revelated disrupted mitochondria in DA neurons. Moreover, spatial genomics revealed decreased expression of mitochondrial complex I and III respiratory chain proteins, while proteomics revealed increased respiratory chain and other mitochondrial protein-protein interactions. As such, the CHCHD2 T61I point-mutation mice exhibit robust mitochondrial disruption and a consequent metabolic shift towards glycolysis. These findings thus establish CHCHD2 T61I mice as a new model for mitochondrial-based PD, and implicate disrupted respiratory chain function as a likely causative driver.

neuroscience↗

bioRxiv2023

Sex-specific role for the long noncoding RNA Pnky in mouse behavior

The human brain expresses thousands of different long noncoding RNAs (lncRNAs), and aberrant expression of specific lncRNAs has been associated with cognitive and psychiatric disorders. While a growing number of lncRNAs are now known to regulate neural cell development and function, relatively few have been shown to underlie animal behavior, particularly with genetic strategies that establish lncRNA function in trans. Pnky is an evolutionarily conserved, neural lncRNA that regulates brain development. Using mouse genetic strategies, we show that Pnky has sex-specific roles in mouse behavior and that this lncRNA underlies specific behavior by functioning in trans. Male Pnky-knockout (KO) mice have deficits in cued fear recall, a type of Pavlovian associative memory. In female Pnky-KO mice, the acoustic startle response (ASR) is increased and accompanied by a decrease in prepulse inhibition (PPI), both of which are behaviors altered in affective disorders. Remarkably, expression of Pnky from a bacterial artificial chromosome (BAC) transgene reverses the ASR phenotype of female Pnky-KO mice, demonstrating that Pnky underlies specific animal behavior by functioning in trans. More broadly, these data provide genetic evidence that a lncRNA gene and its function in trans can play a key role in the behavior of adult mammals, contributing fundamental knowledge to our growing understanding of the association between specific lncRNAs and disorders of cognition and mood.

neuroscience↗