Biology subjects

Linehan, J.

Publications and source records attributed to Linehan, J..

4 recordsLinked to original sources

bioRxiv2023

Knockout of Sporadic Creutzfeldt-Jakob Disease Risk Gene Stx6 in Mice Extends Prion Disease Incubation Time

Sporadic Creutzfeldt-Jakob disease (sCJD), the most common human prion disease, is thought to occur when the cellular prion protein (PrPC) spontaneously misfolds and assembles into prion fibrils, culminating in fatal neurodegeneration. In a genome-wide association study of sCJD, we recently identified risk variants in and around the gene STX6, with evidence to suggest a causal increase of STX6 expression in disease-relevant brain regions. STX6 encodes syntaxin-6, a SNARE protein primarily involved in early endosome to trans-Golgi network retrograde transport. Here we developed and characterised a mouse model with genetic depletion of Stx6 and investigated a causal role of Stx6 expression in mouse prion disease through a classical prion transmission study, assessing the impact of homozygous and heterozygous syntaxin-6 knockout on disease incubation periods and prion-related neuropathology. Following inoculation with RML prions, incubation periods in Stx6-/- and Stx6+/- mice differed by 12 days relative to wildtype. Similarly, in Stx6-/- mice, disease incubation periods following inoculation with ME7 prions also differed by 12 days. Histopathological analysis revealed a modest increase in astrogliosis in ME7-inoculated Stx6-/- animals and a variable effect of Stx6 expression on microglia activation, however no differences in neuronal loss, spongiform change or PrP deposition were observed at endpoint. Importantly, Stx6-/- mice are viable and fertile with no gross impairments on a range of neurological, biochemical, histological and skeletal structure tests. Our results provide some support for a pathological role of Stx6 expression in prion disease, which warrants further investigation in the context of prion disease but also other neurodegenerative diseases considering syntaxin-6 appears to have pleiotropic risk effects in progressive supranuclear palsy and Alzheimers disease. Author SummarySporadic Creutzfeldt-Jakob disease (sCJD), the most common human prion disease, is an invariably fatal disease with no established disease-modifying treatments. The identification of STX6 as a proposed risk gene for sCJD motivated the generation of a new mouse knockout model, in which we found no grossly deleterious phenotypes. A transmission study in Stx6-/-, Stx6+/- and Stx6+/+ mice challenged with two prion strains showed reduced syntaxin-6 expression is associated with a modest prolongation of prion disease incubation periods, supporting a pathological role of Stx6 expression in prion disease pathogenesis. Syntaxin-6 appears to have pleiotropic risk effects across multiple neurodegenerative diseases including progressive supranuclear palsy and Alzheimers disease. Thus, this work supports further exploration of the STX6 susceptibility mechanism, which likely has relevance across multiple neurodegenerative diseases.

neuroscience↗

bioRxiv2022

Single-nuclei transcriptomics of mammalian prion diseases identifies dynamic gene signatures shared between species

Mammalian prion diseases are fatal and transmissible neurological conditions caused by the propagation of prions, self-replicating multimeric assemblies of misfolded forms of host cellular prion protein (PrP). The most common human form of the disease, sporadic Creutzfeldt-Jakob disease (sCJD), typically presents as a rapidly progressive dementia and has no effective treatments. Prion diseases are transmissible to laboratory rodents affording unprecedented opportunities to understand neurodegeneration in its evolving stages. Murine models are especially useful in prion research as they develop bona fide prion disease and recapitulate all biochemical and neuropathological hallmarks of human prion disease. Despite extensive studies investigating the changes in transcriptional profiles in prion diseases the mechanisms by which prion diseases induce cellular toxicity, including changes in gene expression profiles are yet to be fully characterized. This is at least in part because confounding effects related to brain cellular heterogeneity have not been resolved. Here, we took advantage of the recent developments in single-cell technologies and performed an unbiased whole-transcriptome single-nucleus transcriptomic analysis in prion disease.

neuroscience↗

bioRxiv2021

Mapping prion pathology in mice using quantitative imaging: an MRI study

Human prion diseases are fatal neurodegenerative disorders which cause cognitive impairment and neurological deficits. Additional measures of tissue status are necessary for improving the sensitivity and specificity of clinical diagnosis as in many cases clinical forms of prion disease are commonly mistaken for other forms of dementia. To that effect, we developed a set of quantitative magnetic resonance-based tools, including magnetic resonance spectroscopy (MRS), magnetization transfer ratio (MTR) and quantitative T1 and T2 imaging to study the course of the disease in an animal model of prion disease. Using in vivo MTR, significant changes were detected in the cortex and thalamus of late-stage prion -infected mice as compared to littermates. In addition, we found a significant increase of MTR in thalamus and cortex of 80 dpi healthy mice when compared with 160 dpi healthy mice suggestive of changes occurring during the development of the brain. Using quantitative T2 mapping, significantly higher values were measured in thalamus of prion mice at all stages of the disease (T2=40ms) while T1 was found to be significantly higher in cortex (T1=1.89s) and hippocampus, albeit only in late-stage prion mice as compared to aged-matched controls (T1=1.67s). Using quantitative MRS significant changes were detected in glutamate (Glu) and myo-inositol (Ins) at all stages of prion disease when compared with the control group. NAA, Cr, Lactate and Lipids were only found to be significantly different at early and late stages of the disease while Taurine (Tau) was only significantly increased in the asymptomatic stage without any significant change at early and late stages of the disease. These changes in MRI and MRS signals, which precede clinical signs of disease, could provide insights into the pathogenesis of this disease and may enable early detection of pathology.

biophysics↗

bioRxiv2021

Can Chemical Exchange Saturation Transfer (CEST MRI) be used as biomarker of disease progression in Prion Disease?

Human prion diseases are fatal neurodegenerative disorders that may have prolonged asymptomatic incubation periods. However, the underlying mechanism by which prions cause brain damage remains unclear. In turn, characterization of early pathological aspects would be of benefit for the diagnosis and potential treatment of these progressive neurodegenerative disorders. We investigated chemical exchange saturation transfer (CEST) MRI based on its exquisite sensitivity to cytosol protein content as a surrogate for prion disease pathology. Three groups of prion-infected mice at different stages of the disease underwent conventional magnetic resonance imaging and CEST MRI at 9.4T. For each mouse, chemical exchange contrasts were measured by applying five RF powers at various frequency offsets using magnetization transfer asymmetries. Relayed Nuclear Overhauser effects (NOE*) and amide proton transfer (APT*) were also assessed. For comparison, CEST MRI measurements were also made in healthy control mice brains. Here we show that alterations in CEST signal were detected before structural modifications or any clinical signs of prion disease. The detected CEST signal displayed different patterns at different stages of the disease indicating its potential for use as a longitudinal marker of disease progression. Highly significant correlations were found between CEST metrics and histopathological findings. A decline in NOE signal was positively correlated with abnormal prion protein deposition (R2 = 0.91) in the thalami of prion infected mice. Moreover, the NOE signal was negatively correlated with astrogliosis (R2 = 0.71) in the thalamus. No significant correlations were detected between NOE signals and spongiosis. MTR asymmetry at 3.5 ppm was also correlated with astrogliosis (R2 = 0.59), and prion protein deposition (R2 = 0.63) in thalamus. No significant changes were detected in APT* between prion-infected and control mice at all stages of the disease. Finally, MTR asymmetry between 2.8 and 3.2 ppm was correlated with prion protein deposition (R2 = 0.47) in the thalamus of prion -infected mice. To conclude, CEST MRI has potential utility as a biomarker of neurodegenerative processes in prion disease.

biophysics↗