Biology subjects

Jackson, R. J.

Publications and source records attributed to Jackson, R. J..

6 recordsLinked to original sources

bioRxiv2026

Utilizing a cell culture based novel cellular thermal shift assay to understand the isoform-dependent thermal stability of ApoE variants

Apolipoprotein E (ApoE) is the primary genetic risk modifier of late-onset Alzheimers disease, with the {varepsilon}4 allele increasing risk up to 15-fold relative to {varepsilon}3. The structural differences between isoforms are thought to underlie their distinct effects on lipid transport, receptor binding, and disease risk. ApoE4 exhibits reduced thermodynamic stability compared to ApoE3, but prior characterisation has relied on purified recombinant protein, leaving open whether these differences are preserved in native cellular environments and how they relate to rare disease-associated variants. Here, we employed the cellular thermal shift assay (CETSA) and a bioluminescence-based thermal stability assay (BiTSA) to systematically characterise ApoE thermal stability across isoforms and variants. Using CETSA on brain tissue from humanised APOE knock-in mice and post-mortem human brain, we confirm that ApoE4 exhibits significantly reduced thermal stability compared to ApoE3 in native tissue, with this difference conserved across species despite variation in absolute melting temperatures. We developed BiTSA, which leverages a split-luciferase HiBiT tag to quantify soluble ApoE across a thermal gradient in living cells, providing a higher-throughput platform that faithfully recapitulates isoform stability differences. Applying BiTSA to rare AD-associated variants, we found that L28P exerts divergent, isoform-dependent effects, destabilising ApoE3 while paradoxically stabilising ApoE4--a finding supported by AlphaFold modelling revealing isoform-specific differences in helix 1 architecture. These results establish BiTSA as a robust cellular tool for ApoE variant characterisation and demonstrate that isoform background critically modulates the structural consequences of rare mutations.

neuroscience↗

bioRxiv2026

Lipidated ApoE is found in nanoscale proximity to Aβ aggregates in human Alzheimer brains.

Apolipoprotein E (APOE) associates with amyloid plaques (A{beta}) in Alzheimer disease (AD). The {varepsilon}4 allele of apolipoprotein E (APOE{varepsilon}4) is the strongest genetic risk factor for sporadic AD and exacerbates A{beta} plaque burden relative to APOE{varepsilon}3 and APOE{varepsilon}2. The majority of ApoE associates with multiple lipid classes to form lipoproteins both in the brain and the periphery. However, the lipidation status of A{beta} plaque-associated ApoE is not yet fully defined. Here, we use fluorescence lifetime imaging microscopy coupled with Forster resonance energy transfer (FLIM-FRET) to determine the lipidation status of ApoE in plaques, as well as the nanoscale spatial proximity of ApoE and A{beta} to anionic lipids and cholesterol within human AD brain tissue. We demonstrate that lipids are in close nanoscale proximity to ApoE and A{beta} within A{beta} plaques. Our results reveal that lipidated ApoE complexes enriched in anionic lipids and cholesterol are core constituents of AD plaques in-situ. We propose a pathological mechanism in which the surface presentation of anionic lipids on ApoE lipoproteins facilitates initial interaction with and subsequent aggregation of A{beta}.

neuroscience↗

bioRxiv2023

APOE2 gene therapy reduces amyloid deposition, and improves markers of neuroinflammation and neurodegeneration in a mouse model of Alzheimer disease

Epidemiological studies show that individuals who carry the relatively uncommon APOE {varepsilon}2 allele rarely develop Alzheimer disease, and if they do they have a later age of onset, milder clinical course, and less severe neuropathological findings than others with Alzheimer disease. The contrast is especially stark in comparison to the phenotype associated with the major genetic risk factor for Alzheimer disease, APOE {varepsilon}4, which has an age of onset several decades earlier, as well as a more aggressive clinical course and notably more severe neuropathological findings, especially in terms of the amount of amyloid deposition. Even one APOE {varepsilon}2 allele improves phenotype, but it is uncertain if that is due to the replacement of a more toxic allele by APOE {varepsilon}2, or if APOE {varepsilon}2 has a protective, neuro-modulatory effect. Here, we demonstrate that brain exposure to APOE2 via a gene therapy approach which bathes the entire cortical mantle in the gene product after transduction of the ependyma, rapidly ameliorates established A{beta} plaque deposition, neurodegenerative synaptic loss, and, remarkably, reduces microglial activation in an APP/PS1 mouse model despite continued expression of human APOE4. This result suggests a promising protective effect of exogenous APOE2, revealing a cell non-autonomous effect of the protein on microglial activation. We also show that plaque associated microglia in the brain of patients who inherit APOE2 similarly have less microglial reactivity to plaques. These data raise the potential that an APOE2 therapeutic could be effective in Alzheimer disease even in individuals born with the risk {varepsilon}4 allele. One Sentence SummaryIntroduction of ApoE2 using an AAV that transduces the ependymal cells of the ventricle causes a reduction in amyloid load and plaque associated synapse loss, and reduces neuroinflammation by modulating microglial responsiveness to plaques.

neuroscience↗

bioRxiv2021

TMEM97 increases in synapses and is a potential synaptic Aβ binding partner in human Alzheimer's disease

Synapse loss correlates with cognitive decline in Alzheimers disease, and soluble oligomeric amyloid beta is implicated in synaptic dysfunction and loss. An important knowledge gap is the lack of understanding of how amyloid beta leads to synapse degeneration. In particular, there has been difficulty in determining whether there is a synaptic receptor that binds amyloid beta and mediates toxicity. While many candidates have been observed in model systems, their relevance to human AD brain remains unknown. This is in part due to methodological limitations preventing visualization of amyloid beta binding at individual synapses. To overcome this limitation, we combined two high resolution microscopy techniques: array tomography and Forster resonance energy transfer (FRET) to image over 1 million individual synaptic terminals in temporal cortex from AD (n=9) and age matched control cases (n=6). Within postsynaptic densities, amyloid beta generates a FRET signal with transmembrane protein 97, cellular prion protein, and postsynaptic density 95. Transmembrane protein 97 is also present in a higher proportion of postsynapses in Alzheimers brain compared to controls. Further, we inhibited amyloid beta / transmembrane protein 97 interaction in a mouse model of amyloidopathy by treating with the an allosteric modulator CT1812 or vehicle. CT1812 drug concentration correlated negatively with synaptic FRET signal between transmembrane protein 97 and amyloid beta. In human induced pluripotent stem cell derived neurons challenged with human Alzheimers brain homogenate, transmembrane protein 97 and amyloid beta are present in synapses. Transcriptional changes are induced by A{beta} including changes in genes involved in neurodegeneration and neuroinflammation. CT1812 treatment of these neurons caused changes in gene sets involved in synaptic function. These data support a role for transmembrane protein 97 in the synaptic binding of amyloid beta in human Alzheimers disease brain where it may mediate synaptotoxicity.

neuroscience↗

bioRxiv2018

Reducing tau ameliorates behavioural and transcriptional deficits in a novel model of Alzheimer’s disease

SummaryOne of the key knowledge gaps blocking development of effective therapeutics for Alzheimers disease (AD) is the lack of understanding of how amyloid beta (A{beta}) and tau cooperate in causing disease phenotypes. Within a mouse tau deficient background, we probed the molecular, cellular and behavioural disruption triggered by wild-type human taus influence on human A{beta}-induced pathology. We find that A{beta} and tau work cooperatively to cause a hyperactivity phenotype and to cause downregulation of gene transcription including many involved in synaptic function. In both our mouse model and in human post-mortem tissue, we observe accumulation of pathological tau in synapses, supporting the potential importance of synaptic tau. Importantly, tau depletion in the mice, initiated after behavioural deficits emerge, was found to correct behavioural deficits, reduce synaptic tau levels, and substantially reverse transcriptional perturbations, suggesting that lowering tau levels, particularly at the synapse, may be beneficial in AD.\n\nHighlights- Expression of human familial Alzheimers associated mutant amyloid precursor protein and presenillin 1 with wild-type human tau in the absence of endogenous tau in a novel MAPT-AD mouse model results in behavioural deficits and downregulation of genes involved in synaptic function.\n- Tau is present in pre and postsynaptic terminals in MAPT-AD mice and human AD brain. In mice, lowering synaptic tau levels was associated with improved cognition and recovered gene expression.\n- These data suggest that A{beta} and tau act cooperatively in impairing synaptic function and that lowering tau at synapses could be a beneficial therapeutic approach in AD.

neuroscience↗

bioRxiv2017

Human brain-derived Aβ oligomers bind to synapses and disrupt synaptic activity in a manner that requires APP

Compelling genetic evidence links the amyloid precursor protein (APP) to Alzheimers disease (AD), and several theories have been advanced to explain the involvement of APP in AD. A leading hypothesis proposes that a small amphipathic fragment of APP, the amyloid {beta}-protein (A{beta}), self-associates to form soluble aggregates which impair synaptic and network activity. Here, we report on the plasticity-disrupting effects of A{beta} isolated from AD brain and the requirement of APP for these effects. We show that A{beta}-containing AD brain extracts block hippocampal long-term potentiation (LTP), augment glutamate release probability and disrupt the excitation/inhibition balance. Notably, these effects are associated with A{beta} localizing to synapses, and genetic ablation of APP prevents both A{beta} binding and A{beta}-mediated synaptic dysfunctions. These findings indicate a role for APP in AD pathogenesis beyond the generation of A{beta} and suggest modulation of APP expression as a therapy for AD.\n\nAcknowledgmentsWe thank Dr. Tiernan T. OMalley for useful discussions and technical advice. This work was supported by grants to DMW from the National Institutes of Health (AG046275), Bright Focus, and the United States-Israel Binational Science Foundation (2013244, DMW and IS); grants to TSJ from Alzheimers Research UK and the Scottish Government (ARUK-SPG2013-1), Wellcome Trust-University of Edinburgh Institutional Strategic Support funds, and the H2020 European Research Council (ALZSYN); and to the Massachusetts Alzheimers Disease Research Center (AG05134).

neuroscience↗