Biology subjects

Burton, E. A.

Publications and source records attributed to Burton, E. A..

6 recordsLinked to original sources

bioRxiv2025

Functional interrogation of neuronal connections by chemoptogenetic presynaptic ablation

Most neurons are embedded in multiple circuits, with signaling to distinct postsynaptic partners playing functionally different roles. The function of specific connections can be interrogated using synaptically localized optogenetic effectors, however these tools are often experimentally difficult to validate or produce paradoxical outcomes. We have developed a system for photoablation of synaptic connections originating from genetically defined neurons, based on presynaptic localization of the fluorogen activating protein dL5** that acts as a photosensitizer when bound to a cell-permeable dye. Using the well mapped zebrafish escape circuit as a readout, we first show that cytoplasmically expressed dL5** enables efficient spatially targeted neuronal ablation using near infra-red light. We then demonstrate that spatially patterned illumination of presynaptically localized dL5** can effectively disconnect neurons from selected downstream partners, producing precise behavioral deficits. This technique should be applicable to almost any genetically tractable neuronal circuit, enabling precise manipulation of functional connectivity within the nervous system.

neuroscience↗

bioRxiv2024

Tau load in select brainstem neurons predicts the severity and nature of balance deficits in the absence of cell death

Patients with tauopathies present with profoundly different clinical symptoms1, even within the same disorder2. A central hypothesis in the field, well-supported by biomarker studies3,4 and post-mortem pathology5-7, is that clinical heterogeneity reflects differential degeneration of vulnerable neuronal populations responsible for specific neurological functions. Recent work has revealed mechanisms underlying susceptibility of particular cell types8-10, but relating tau load to disrupted behavior -- es- pecially before cell death -- requires a targeted circuit-level approach. Here we studied two distinct balance behaviors in larval zebrafish11 expressing a human 0N/4R-tau allele12 in select populations of evolutionarily-conserved and well-characterized brainstem vestibular circuits13,14. We observed that human tau load predicted the severity of circuit-specific deficits in posture and navigation in the ab- sence of cell death. Targeting expression to either mid- or hindbrain balance neurons recapitulated these particular deficits in posture and navigation. By parametrically linking tau load in specific neu- rons to early behavioral deficits, our work moves beyond cell type to close the gap between pathological and neurological conceptions of tauopathy.

neuroscience↗

bioRxiv2024

Variant-to-function mapping of late-onset Alzheimer's disease GWAS signals in human microglial cell models implicates RTFDC1 at the CASS4 locus

Late-onset Alzheimers disease (LOAD) research has principally focused on neurons over the years due to their known role in the production of amyloid beta plaques and neurofibrillary tangles. In contrast, recent genomic studies of LOAD have implicated microglia as culprits of the prolonged inflammation exacerbating the neurodegeneration observed in patient brains. Indeed, recent LOAD genome-wide association studies (GWAS) have reported multiple loci near genes related to microglial function, including TREM2, ABI3, and CR1. However, GWAS alone cannot pinpoint underlying causal variants or effector genes at such loci, as most signals reside in non-coding regions of the genome and could presumably confer their influence frequently via long-range regulatory interactions. We elected to carry out a combination of ATAC-seq and high-resolution promoter-focused Capture-C in two human microglial cell models (iPSC-derived microglia and HMC3) in order to physically map interactions between LOAD GWAS-implicated candidate causal variants and their corresponding putative effector genes. Notably, we observed consistent evidence that rs6024870 at the GWAS CASS4 locus contacted the promoter of nearby gene, RTFDC1. We subsequently observed a directionallly consistent decrease in RTFDC1 expression with the the protective minor A allele of rs6024870 via both luciferase assays in HMC3 cells and expression studies in primary human microglia. Through CRISPR-Cas9-mediated deletion of the putative regulatory region harboring rs6024870 in HMC3 cells, we observed increased pro-inflammatory cytokine secretion and decreased DNA double strand break repair related, at least in part, to RTFDC1 expression levels. Our variant-to-function approach therefore reveals that the rs6024870-harboring regulatory element at the LOAD CASS4 GWAS locus influences both microglial inflammatory capacity and DNA damage resolution, along with cumulative evidence implicating RTFDC1 as a novel candidate effector gene.

genetics↗

bioRxiv2024

A larval zebrafish model of TBI: Optimizing the dose of neurotrauma for discovery of treatments and aetiology

Traumatic brain injuries (TBI) are diverse with heterogeneous injury pathologies, which creates challenges for the clinical treatment and prevention of secondary pathologies such as post-traumatic epilepsy and subsequent dementias. To develop pharmacological strategies that treat TBI and prevent complications, animal models must capture the spectrum of TBI severity to better understand pathophysiological events that occur during and after injury. To address such issues, we improved upon our recent larval zebrafish TBI paradigm emphasizing titrating to different injury levels. We observed coordination between an increase in injury level and clinically relevant injury phenotypes including post-traumatic seizures (PTS) and tau aggregation. This preclinical TBI model is simple to implement, allows dosing of injury levels to model diverse pathologies, and can be scaled to medium- or high-throughput screening.

neuroscience↗

bioRxiv2021

Neuronal NADPH oxidase in Parkinson disease pathogenesis

Mitochondrial dysfunction and oxidative stress are strongly implicated in the pathogenesis of Parkinsons disease (PD) and there is evidence that mitochondrially-generated superoxide can activate NADPH oxidase 2 (NOX2), which is a major enzymatic generator of superoxide. Although NOX2 has been examined in the context of PD, previous studies have focused on microglial function; the role of neuronal NOX2 in PD pathogenesis remains to be defined. Here we devised and validated a proximity ligation assay for NOX2 activity and demonstrated that in human PD and 2 models thereof, neuronal NOX2 is highly active in substantia nigra dopamine neurons. Further, NOX2 activity is responsible for accumulation, post-translational modification and oligomerization of -synuclein as well as activation of leucine-rich repeat kinase 2 (LRRK2). Administration of a brain-penetrant, specific NOX2 inhibitor prevented NOX2 activation and its downstream effects in vivo in a rat model of PD. We conclude that neuronal NOX2 is a major contributor to oxidative stress in PD, to -synuclein pathology and to LRRK2 activation in idiopathic PD. In this context, NOX2 inhibitors hold potential as a disease-modifying therapy in PD. SummaryIn dopamine neuron, NADPH oxidase isoform 2 amplifies the oxidative stress-related pathogenic cascade in Parkinsons disease

neuroscience↗

bioRxiv2020

Seizures are a druggable mechanistic link between TBI and subsequent tauopathy

Traumatic brain injury (TBI) is a prominent risk factor for neurodegenerative diseases and dementias including chronic traumatic encephalopathy (CTE). TBI and CTE, like all tauopathies, are characterized by accumulation of Tau into aggregates that progressively spread to other brain regions in a prion-like manner. The mechanisms that promote spreading and cellular uptake of tau seeds after TBI are not fully understood, in part due to lack of tractable animal models. Here, we test the putative roles for excess neuronal activity and dynamin-dependent endocytosis in promoting the in vivo spread of tauopathy. We introduce tauopathy reporter zebrafish expressing a genetically-encoded fluorescent Tau biosensor that reliably reports accumulation of human tau species when seeded via intra-ventricular brain injections. Subjecting zebrafish larvae to a novel TBI paradigm produced various TBI symptoms including cell death, hemorrhage, blood flow abnormalities, post-traumatic seizures, and Tau inclusions. Bath application of anticonvulsant drugs rescued TBI-induced tauopathy and cell death; these benefits were attributable to inhibition of post-traumatic seizures because co-application of convulsants reversed these beneficial effects. However, one convulsant drug, 4-Aminopyridine, unexpectedly abrogated TBI-induced tauopathy - this was due to its inhibitory action on endocytosis as confirmed via additional dynamin inhibitors. These data suggest a role for seizure activity and dynamin-dependent endocytosis in the prion-like seeding and spreading of tauopathy following TBI. Further work is warranted regarding anti-convulsants that dampen post-traumatic seizures as a route to moderating subsequent tauopathy. Moreover, the data highlight the utility of deploying in vivo Tau biosensor and TBI methods in larval zebrafish, especially regarding drug screening and intervention. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/091819v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@34a2caorg.highwire.dtl.DTLVardef@1ab916borg.highwire.dtl.DTLVardef@d83bf2org.highwire.dtl.DTLVardef@47bf90_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIIntroduces first Traumatic Brain Injury (TBI) model in larval zebrafish, and its easy C_LIO_LITBI induces clinically relevant cell death, haemorrhage & post-traumatic seizures C_LIO_LICa2+ imaging during TBI reveals spike in brain activity concomitant with seizures C_LIO_LITau-GFP Biosensor allows repeated in vivo measures of prion-like tau aggregation C_LIO_LIpost-TBI, anticonvulsants stop tauopathies akin to Chronic Traumatic Encephalopathy C_LI

neuroscience↗