Biology subjects

Wright, A. L.

Publications and source records attributed to Wright, A. L..

6 recordsLinked to original sources

bioRxiv2023

A transient protein folding response targets aggregation in the early phase of TDP-43-mediated disease

Understanding the mechanisms that drive TDP-43 pathology is integral to combating neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). To address this, we sought to determine the timeline of proteomic alterations across disease course in TDP-43 proteinopathy. Using longitudinal quantitative proteomics analysis of cortex samples from the cytoplasmic TDP-43 rNLS8 mouse model of ALS and FTLD, we identified several distinct protein subsets characterized by temporal alterations in protein abundance across diverse biological pathways, including protein folding, intracellular transport, myelination, and neuronal synaptic function. Remarkably, neurons in the rNLS8 cortex elicited a transitory response primarily comprising protein-folding factors prior to and in the earliest stages of disease progression. This response included increased levels of DnaJ homolog subfamily B member 5, DNAJB5, and proof-of-concept studies showed that DNAJB5 over-expression decreased TDP-43 aggregation in cell and cortical neuron cultures. Conversely, knockout of Dnajb5 exacerbated motor impairments caused by AAV-mediated cytoplasmic TDP-43 expression in the brains and spinal cords of mice. Lastly, the late disease proteomic signatures of rNLS8 mouse cortex strongly correlated with changes in human autopsy-derived TDP-43 proteinopathy tissues, indicating commonality of disease processes. Together, these findings reveal molecular mechanisms that regulate protein levels through distinct stages of ALS and FTLD progression, and suggest that protein folding factors that combat cytoplasmic TDP-43 protein aggregation could be protective in disease. HighlightsO_LIThe first longitudinal map of the cortex proteome throughout TDP-43-driven disease in a mouse model of cytoplasmic TDP-43 proteinopathy (rNLS8 mice). C_LIO_LICytoplasmic TDP-43 accumulation drives many dynamic changes to the cortex proteome, including increases in protein folding factors prior to disease onset. C_LIO_LIThe protein folding factor DNAJB5 decreases TDP-43 aggregation in HEK293 cells and primary cortical neurons and Dnajb5 knockout exacerbates cytoplasmic TDP-43-associated motor impairments in vivo. C_LIO_LIThe proteomic signature of the rNLS8 mouse cortex correlates strongly with postmortem brain tissue from human TDP-43 proteinopathies. C_LIO_LIA new webtool, TDP-map (https://shiny.rcc.uq.edu.au/TDP-map/), allows comparison of transcriptomic and proteomic datasets from mouse and human TDP-43 proteinopathy. C_LI

neuroscience↗

bioRxiv2022

Early activation of cellular stress and death pathways caused by cytoplasmic TDP-43 in the rNLS8 mouse model of ALS/FTD

TAR DNA binding protein 43 (TDP-43) pathology is a key feature of over 95% of amyotrophic lateral sclerosis (ALS) and nearly half of frontotemporal dementia (FTD) cases. The pathogenic mechanisms of TDP-43 dysfunction are poorly understood, however activation of cell stress pathways may contribute to pathogenesis. We therefore sought to identify which cell stress components are critical for driving disease onset and neurodegeneration in ALS/FTD. We studied the rNLS8 transgenic mouse model, which expresses human TDP-43 with a genetically-ablated nuclear localisation sequence within neurons of the brain and spinal cord resulting in cytoplasmic TDP-43 pathology and progressive motor dysfunction. Amongst numerous cell stress-related biological pathways profiled using qPCR arrays, several critical ISR effectors, including CCAAT/enhancer-binding homologous protein (Chop/Ddit3) and activating transcription factor 4 (Atf4), were upregulated in the cortex of rNLS8 mice prior to disease onset. This was accompanied by early up-regulation of anti-apoptotic gene Bcl2 and diverse pro-apoptotic genes including BH3-interacting domain death agonist (Bid). However, pro-apoptotic signalling predominated after onset of motor phenotypes. Notably, pro-apoptotic caspase-3 protein was elevated in the cortex of rNLS8 mice at later disease stages, suggesting that downstream activation of apoptosis drives neurodegeneration following failure of early protective responses. Unexpectedly, suppression of Chop in the brain and spinal cord using antisense oligonucleotide-mediated silencing had no effect on overall TDP-43 pathology or disease phenotypes in rNLS8 mice. Cytoplasmic TDP-43 accumulation therefore causes very early activation of ISR and both anti-and pro-apoptotic signalling that switches to predominant pro-apoptotic activation later in disease. These findings suggest that precise temporal modulation of cell stress and death pathways may be beneficial to protect against neurodegeneration in ALS and FTD. Key pointsO_LIISR genes Atf4 and Chop, anti-apoptotic Bcl2 and pro-apoptotic gene Bid, Bim, Noxa were upregulated in the cortex of rNLS8 mice prior to disease onset C_LIO_LIKnockdown of Chop had limited effects on TDP-43 pathology and did not alter motor deficits in rNLS8 mice C_LIO_LIBoth anti-and pro-apoptotic genes are upregulated prior to disease onset, and switches to activation of pro-apoptotic signalling at later disease stages C_LIO_LICaspase-3 activation likely drives neurodegeneration in the cortex of rNLS8 mice C_LI

neuroscience↗

bioRxiv2019

Riluzole does not ameliorate disease caused by cytoplasmic TDP-43 in a mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease commonly treated with riluzole, a small molecule that may act via modulation of glutamatergic neurotransmission. However, riluzole only modestly extends lifespan for people living with ALS and its precise mechanisms of action remain unclear. Most ALS cases are characterised by accumulation of cytoplasmic TAR DNA binding protein of 43 kDa (TDP-43), and understanding the effects of riluzole in models that closely recapitulate TDP-43 pathology may provide insights for development of improved therapeutics. We therefore investigated the effects of riluzole in transgenic mice that inducibly express nuclear localisation sequence (NLS)-deficient human TDP-43 in neurons (NEFH-tTA/tetO-hTDP-43{Delta}NLS, rNLS, mice). Riluzole treatment from the first day of hTDP-43{Delta}NLS expression did not alter disease onset, weight loss or performance on multiple motor behavioural tasks. Riluzole treatment also did not alter TDP-43 protein levels, solubility or phosphorylation. Although we identified a significant decrease in GluA2 and GluA3 proteins in the cortex of rNLS mice, riluzole did not ameliorate this disease-associated molecular phenotype. Likewise, riluzole did not alter the disease-associated atrophy of hindlimb muscle in rNLS mice. Finally, riluzole treatment beginning after disease onset in rNLS mice similarly had no effect on progression of late-stage disease or animal survival. Together, we demonstrate specific glutamatergic receptor alterations and muscle fibre-type changes reminiscent of ALS in rNLS mice, but riluzole had no effect on these or any other disease phenotypes. Future targeting of pathways directly related to accumulation of TDP-43 pathology may be needed to develop better treatments for ALS. Significance StatementAccumulation of cytoplasmic TDP-43 protein is the hallmark pathology of ALS. Riluzole is the most widely used drug for ALS treatment, but provides only a short extension of lifespan. We demonstrate here in the rNLS mouse model, which mimics TDP-43 pathology, that riluzole does not ameliorate progressive alterations in motor strength and coordination, muscle atrophy, glutamate receptor levels, or TDP-43 protein levels and solubility, and does not prolong animal survival. Riluzole similarly did not affect decreased levels of glutamate receptor subunits GluA2/GluA3 in rNLS mice. The inability of riluzole to rescue pathological or phenotypic changes in this TDP-43 model provides further impetus for the discovery of improved therapies targeting the key drivers of ALS pathogenesis.

neuroscience↗

bioRxiv2017

Nutrient homeostasis and mechanisms related to nutrient retention by wetland macrophytes in a subtropical wetland.

Nutrient homeostasis relates ambient stoichiometric conditions in an environment to the stoichiometry of living entities of the ecosystem. In wetland ecosystems, vegetation can be a large, highly variable and dynamic sink of nutrients. This study investigated stoichiometric homeostasis of dominant emergent and submerged aquatic vegetation (EAV and SAV, respectively) within two treatment flow-ways (FW) of Everglades Stormwater Treatment Area 2 (STA-2). These FW encompass a large gradient in plant nutrient availability. The hypotheses of this study is that wetland vegetation is non-homeostatic relative to ambient nutrients and consequently nutrient resorption will not vary along the nutrient gradient. We developed a framework to investigate how vegetation uptake and resorption of nutrients contribute separately to homeostasis. Overall, the wetland vegetation in this study was non-homeostatic with respect to differential uptake of nitrogen (N) vs. phosphorus (P). Resorption evaluated for EAV was high for P and moderate for N, resorption efficiency did not significantly vary along the gradient and therefore did not affect overall homeostatic status. Nutrient addition experiments may help to compensate for some of the limitation of our study, especially with respect to resolving the primary nutrient source (organic vs. inorganic sources, water vs. soil compartment) and nutrient utilization rates.

ecology↗

bioRxiv2017

Stoichiometric relationships amongst ecosystem compartments of a subtropical treatment wetland

BackgroundEvaluation of carbon (C), nitrogen (N) and phosphorus (P) ratios in aquatic and terrestrial ecosystems can advance our understanding of biological processes, nutrient cycling and the fate of organic matter (OM) in aquatic ecosystems. Eutrophication of aquatic ecosystems can disrupt the accumulation and decomposition of OM which serves as the base of the aquatic food web, and is central to the effectiveness of a treatment wetland. This study investigated nutrient stoichiometry within and between wetland ecosystem compartments (i.e. water column, vegetation, flocculent and soil) of two treatment flow-ways (FWs) in the Everglades Stormwater Treatment Areas located in south Florida (USA). These FWs include an emergent aquatic vegetation cell dominated by Typha spp.(cattail) and a submerged aquatic vegetation cell composed of species such as Chara spp. (muskgrass) and Potamogeton spp. (pondweed). The primary objective of this evaluation was to determine if nutrient stoichiometry is consistent within and between ecosystems and compartments to understand biogeochemical cycling and controls of nutrient removal within a treatment wetland ecosystem.\n\nResultsThis study demonstrates that C, N, and P stoichiometry can be highly variable among ecosystem compartments and between differing wetland ecosystems. Generally, total P declined along the length of each treatment FW in all ecosystem compartments, whereas trends in total N and C trends were more variable. These changes in C and nutrient concentrations result in variable nutrient stoichiometry along treatment FWs signaling potential changes in absolute and relative nutrient availability and biogeochemical processes.\n\nConclusionsAssessment of wetland nutrient stoichiometry between and within ecosystem compartments suggest decoupling of C:N:P relationships likely as a consequence of differential external nutrient supply, differences in primary producer communities and differential decomposition of organic matter. However, stoichiometry varies often monotonous along the flow paths, likely exhibiting a response to nutrient loading. Differences in C:N:P ratios in primary producers, light availability, microbial immobilization in the early stage of decomposition as well as nutrient mining during decomposition of OM are likely feedback mechanisms that lead to deviations from fixed stoichiometry, which in turn may have considerable influence on nutrient removal rates. This information could be used to further understand water treatment performance with respect to stoichiometric processes and OM decomposition.

ecology↗

bioRxiv2017

Carbon pool trends and dynamics within a subtropical peatland during long-term restoration

BackgroundThe Florida Everglades has undergone significant ecological change spanning the continuum of disturbance to restoration. While the restoration effort is not complete and the ecosystem continues to experience short duration perturbations, a better understanding of long-term C dynamics of the Everglades is needed to facilitate new restoration efforts. This study evaluated temporal trends of different aquatic carbon (C) pools of the northern Everglades Protection Area over a 20-year period to gauge historic C cycling patterns. Dissolved inorganic C (DIC), dissolved organic C (DOC), particulate organic C (POC), and surface water carbon dioxide (pCO2(aq)) were investigated between May 1, 1994 and April 30, 2015.\n\nResultsAnnual mean concentrations of DIC, DOC, POC, and pCO2(aq) significantly decreased through time or remained constant across the Water Conservation Areas (WCAs). Overall, the magnitude of the different C pools in the water column significantly differed between regions. Outgassing of CO2 was dynamic across the Everglades ranging from 420 to 2001 kg CO2 yr-1. Overall the historic trend in CO2 flux from the marsh declined across our study area while pCO2(aq) largely remained somewhat constant with the exception of Water Conservation Area 2 which experienced significant declines in pCO2(aq). Particulate OC concentrations were consistent between WCAs, but a significantly decreasing trend in annual POC concentrations were observed.\n\nConclusionsHydrologic condition and nutrient inputs significantly influenced the balance, speciation, and flux of C pools across WCAs suggesting a subsidy-stress response in C dynamics relative to landscape scale responses in nutrient availability. The interplay between nutrient inputs and hydrologic condition exert a driving force on the balance between DIC and DOC production via the metabolism of organic matter which forms the base of the aquatic foodweb. Along the restoration trajectory as water quality and hydrology continues to improve it is expected that C pools will respond accordingly.

ecology↗