Biology subjects

Standaert, D. G.

Publications and source records attributed to Standaert, D. G..

14 recordsLinked to original sources

bioRxiv2026

Altered Striatal Acetylcholine Dynamics across Dopamine Loss and L-DOPA Treatment

LDOPA remains the most effective therapy for Parkinson's disease (PD), yet its chronic use often induces involuntary movements known as L-DOPA-induced dyskinesia (LID). While abnormal cholinergic interneuron (ChI) activity is a hallmark of both PD and LID, emerging evidence suggests that the temporal organization of acetylcholine (ACh) signaling, rather than its overall magnitude, may determine its functional impact. Under physiological conditions, ChIs exhibit intrinsic delta-frequency activity reflected in coordinated, slow oscillations of extracellular ACh, which are thought to organize striatal network function and movement pattering. To determine how dopamine (DA) depletion and L-DOPA treatment reshape these ACh dynamics, we used in vivo GRAB-ACh fiber photometry in the unilateral 6-OHDA mouse model. DA depletion disrupted slow ACh rhythmicity, reducing delta-band regularity while increasing higher-frequency phasic activity. Acute L-DOPA broadly suppressed ACh activity across frequencies, partially normalizing this imbalance, but without restoring slow temporal structure. In addition, chronic L-DOPA treatment, associated with established dyskinesia, further impaired delta-band coordination in the DA-depleted striatum during the ON state, while OFF-state activity retained lesion-associated features. The anti-dyskinetic agent amantadine restored low-frequency temporal structure both before and after L-DOPA exposure. Together, these findings reveal a state-dependent reorganization of striatal ACh dynamics, characterized by a shift from coordinated slow oscillations to irregular phasic activity following DA loss, and a further breakdown of slow temporal organization during dyskinetic states. These results highlight the temporal structure of cholinergic signaling as a critical and underappreciated dimension of striatal function in PD and LID.

neuroscience↗

bioRxiv2026

Elucidating the dysbiotic features of gut microbiome, interaction with the human genome, and utility as a biomarker for treatment of Parkinson disease.

Parkinsons disease (PD) is the fastest-growing neurologic disease and a leading cause of disability worldwide. PD affects the body and mind, is progressive, and there is no prevention or cure. Gut microbiome, a recently recognized contributing factor in PD, offers new leads for understanding the underlying pathobiology and devising new treatments. Here, we present the most comprehensive study of the PD gut microbiome to date, comprising three large datasets with a sample size of 1,006 PD and 544 neurologically healthy controls, generated with uniform methodology from subject recruitment to data analysis, and characterized using deep shotgun metagenome sequencing, genome-wide genotypes, and metadata. We begin by describing the gut dysbiosis at the species, gene, pathway, and functional level. Next, we find that PD-associated genetic variants at the SNCA gene region are associated with increased abundance of opportunistic pathogens and depletion of fiber degraders in the PD gut. We show that the presence of opportunistic pathogens at high levels in the gut increases the penetrance of SNCA variants for PD risk, raising the GWAS-derived odds ratio from less than 1.5 to over 8. The genetic variants identified here control splicing of the SNCA transcripts into alpha-synuclein isoforms with varying affinity for pathological aggregation. These data suggest pathogens are triggers for disease in the setting of genetic susceptibility, and the link to the genome implicates the microbes in the causation of PD. Finally, shifting focus to translation, we show that not all PD patients have the same dysbiotic features, and propose a conceptual framework to identify microbiome-based biomarkers to select appropriate patients for targeted microbiome-based clinical trials and personalized treatment.

molecular biology↗

bioRxiv2025

T cell responses towards PINK1 and α-synuclein are elevated in prodromal Parkinson's disease

A role of the immune system in Parkinsons disease (PD) progression has long been suspected due to the increased frequency of activated glial cells and infiltrating T cells into the substantia nigra. It was previously reported that PD donors have increased T cell responses towards PINK1 and -synuclein (-syn), two Lewy body-associated proteins. Further, T cell reactivity towards -syn was highest closer to disease onset, highlighting that autoreactive T cells might play a role in PD pathogenesis. However, whether T cell autoreactivity is present during prodromal PD is unknown. Here, we investigated T cell responses towards PINK1 and -syn in donors at high risk of developing PD (i.e. prodromal PD: genetic risk, hyposmia, and or REM sleep behavior disorder), in comparison to PD and healthy control donors. T cell reactivity to these two autoantigens was detected in prodromal PD at levels comparable to those detected in individuals with clinically diagnosed PD. Aligned with the increased incidence of PD in males, we found that males with PD, but not females, had elevated T cell reactivity compared to healthy controls. However, among prodromal PD donors, males and females had elevated T cell responses. These differing trends in reactivity highlights the need for further studies of the impact of biological sex on neuroinflammation and PD progression.

neuroscience↗

bioRxiv2024

Single molecule array measures of LRRK2 kinase activity in serum link Parkinson's disease severity to peripheral inflammation

BackgroundLRRK2-targeting therapeutics that inhibit LRRK2 kinase activity have advanced to clinical trials in idiopathic Parkinsons disease (iPD). LRRK2 phosphorylates Rab10 on endolysosomes in phagocytic cells to promote some types of immunological responses. The identification of factors that regulate LRRK2-mediated Rab10 phosphorylation in iPD, and whether phosphorylated-Rab10 levels change in different disease states, or with disease progression, may provide insights into the role of Rab10 phosphorylation in iPD and help guide therapeutic strategies targeting this pathway. MethodsCapitalizing on past work demonstrating LRRK2 and phosphorylated-Rab10 interact on vesicles that can shed into biofluids, we developed and validated a high-throughput single-molecule array assay to measure extracellular pT73-Rab10. Ratios of pT73-Rab10 to total Rab10 measured in biobanked serum samples were compared between informative groups of transgenic mice, rats, and a deeply phenotyped cohort of iPD cases and controls. Multivariable and weighted correlation network analyses were used to identify genetic, transcriptomic, clinical, and demographic variables that predict the extracellular pT73-Rab10 to total Rab10 ratio. ResultspT73-Rab10 is absent in serum from Lrrk2 knockout mice but elevated by LRRK2 and VPS35 mutations, as well as SNCA expression. Bone-marrow transplantation experiments in mice show that serum pT73-Rab10 levels derive primarily from circulating immune cells. The extracellular ratio of pT73-Rab10 to total Rab10 is dynamic, increasing with inflammation and rapidly decreasing with LRRK2 kinase inhibition. The ratio of pT73-Rab10 to total Rab10 is elevated in iPD patients with greater motor dysfunction, irrespective of disease duration, age, sex, or the usage of PD-related or anti-inflammatory medications. pT73-Rab10 to total Rab10 ratios are associated with neutrophil activation, antigenic responses, and the suppression of platelet activation. ConclusionsThe extracellular ratio of pT73-Rab10 to total Rab10 in serum is a novel pharmacodynamic biomarker for LRRK2-linked innate immune activation associated with disease severity in iPD. We propose that those iPD patients with higher serum pT73-Rab10 levels may benefit from LRRK2-targeting therapeutics to mitigate associated deleterious immunological responses.

neuroscience↗

bioRxiv2024

Cholinergic Transmission in an Inducible Transgenic Mouse Model of Paroxysmal Dystonia

Altered interaction between striatonigral dopaminergic (DA) inputs and local acetylcholine (ACh) in striatum has long been hypothesized to play a central role in dystonia pathophysiology. Indeed, previous research across various genetic mouse models of human isolated dystonia has identified as a shared endophenotype with paradoxical excitation of striatal cholinergic interneurons (ChIs) activity in response to activation of dopamine D2 receptor (D2R). These mouse models lack a dystonic motor phenotype, which leaves a critical gap in comprehending the role of ACh transmission in the manifestation of dystonia. To tackle this question, we used a combination of ex vivo slice physiology and in vivo monitoring of striatal ACh dynamics in the inducible, phenotypically penetrant, transgenic mouse model of paroxysmal non-kinesigenic dyskinesia (PNKD). We found that, similarly to other genetic models, the PNKD mouse displays D2R-induced paradoxical excitation of ChI firing in ex vivo striatal brain slices. In vivo, caffeine triggers dystonic symptoms while reversing the D2R-mediated excitation of ChIs and desynchronizing the striatal cholinergic network. In WT littermate controls, caffeine stimulates spontaneous locomotion through a similar but reversed mechanism involving an excitatory switch of the D2R control of ChI activity, associated with enhanced cholinergic network synchronization. Together these observations suggest that D2Rs may play an important role in synchronizing the ChI network during heightened movement states. The "paradoxical excitation" described in dystonia models could represent a compensatory or protective mechanism that prevents manifestation of movement abnormalities and allows for phenotypic dystonia when lost.

neuroscience↗

bioRxiv2024

Alpha-synuclein overexpression can drive microbiome dysbiosis in mice

Growing evidence indicates that persons living with Parkinson disease (PD), have a unique composition of indigenous gut microbes. Given the long prodromal or pre-diagnosed period, longitudinal studies of the human and rodent gut microbiome prior to symptomatic onset and for the duration of the disease period are currently lacking. PD is characterized in part by accumulation of the protein -synuclein (-syn) into insoluble aggregates, in both the central and enteric nervous systems. As such, a number of experimental rodent and non-human primate models of -syn overexpression recapitulate some of hallmark pathophysiologies of PD. These animal models provide an opportunity to assess how the gut microbiome changes with age under disease relevant conditions. Here, we used a transgenic mouse strain, the Thy1-hSYN "line 61" mice which over express wild-type human -syn to test how the gut microbiome composition responds in this model of PD pathology during aging. Using shotgun metagenomics, we find significant, age and genotype dependent bacterial taxa that become altered over age. We reveal that -syn overexpression can drive alterations to the gut microbiome composition and suggest that it limits the expansion of diversity through age. Given emerging data on potential contributions of the gut microbiome to PD pathologies, our data provide an experimental foundation to understand how the PD-associated microbiome may arise as a trigger or co-pathology to disease.

microbiology↗

bioRxiv2023

Differential activation states of direct pathway striatal output neurons associated with thedevelopment of L-DOPA-induced dyskinesia.

L-DOPA-induced dyskinesia (LID) is a debilitating motor side effect arising from chronic dopamine replacement therapy with L-DOPA for the treatment of Parkinson disease (PD). The emergence of LID is linked to heightened sensitivity of striatal dopaminergic signaling and driven by abnormal fluctuations in synaptic dopamine levels following each administration of L- DOPA. This maladaptive plasticity narrows the therapeutic window for L-DOPA treatment, even as the progressive worsening of PD symptoms demands escalating doses. The heterogeneous composition of the striatum, including diverse subpopulations of medium spiny output neurons (MSNs), interneurons, and supporting cells, has complicated the precise identification of the cell(s) underlying LID development and persistence. To elucidate the cellular and molecular mechanisms of LID, we used single nucleus RNA-sequencing (snRNA-seq) to establish a comprehensive striatal transcriptional profile during the development and maintenance of LID in an animal model. Hemiparkinsonian mice were treated with vehicle or L-DOPA for progressive durations (1, 5, or 10 d) and nuclei from the striata were processed for snRNA-seq. Our analysis found that a limited population of dopamine D1 receptor-expressing MSNs (D1-MSNs), arising from both the patch and matrix compartments, formed three subclusters in response to L-DOPA treatment that expressed cellular markers of activation. These activated D1-MSN subpopulations display many of the transcriptional changes previously associated with LID; however, the prevalence and transcriptional behavior of activated D1-MSNs was differentially influenced by the extent of L-DOPA experience. The differentially expressed genes found in these D1-MSNs indicated that acute L-DOPA induced upregulation of multiple plasticity-related transcription factors and regulators of MAPK signaling, while repeated L-DOPA exposure induced numerous genes associated with synaptic remodeling, learning and memory, and transforming growth factor-{beta} (TGF{beta}) signaling. Notably, repeated L-DOPA led to a sensitization in the expression of Inhba, a member of the activin/TGF{beta} superfamily, in activated D1-MSNs. We tested pharmacological inhibition of its receptor, ALK4, and found that it impaired LID development. Collectively, these data suggest that distinct subsets of D1-MSNs become differentially responsive to L-DOPA due to the aberrant induction of the molecular mechanisms necessary for neuronal entrainment, similar to those processes underlying hippocampal learning and memory formation. Our data further suggests that activin/TGF{beta} signaling may play an essential role in LID development in this subpopulation of D1-MSNs.

neuroscience↗

bioRxiv2022

Border-associated macrophages mediate the neuroinflammatory response in an alpha-synuclein model of Parkinson disease

Dopaminergic cell loss due to the accumulation of -syn is a core feature of PD pathogenesis. Neuroinflammation specifically induced by -syn has been shown to exacerbate neurodegeneration, yet the role of CNS resident macrophages in this process remains unclear. We found that a specific subset of CNS resident macrophages, border-associated macrophages (BAMs), play an essential role in mediating -syn related neuroinflammation due to their unique role as the antigen presenting cells necessary to initiate a CD4 T cell response. Surprisingly, the loss of MHCII antigen presentation on microglia had no effect on neuroinflammation. Furthermore, -syn expression led to an expansion in BAM numbers and a unique damage-associated activation state. Through a combinatorial approach of single-cell RNA sequencing and depletion experiments, we found that BAMs played an essential role in immune cell recruitment, infiltration, and antigen presentation. Furthermore, BAMs were identified in post-mortem PD brain in close proximity to T cells. These results point to a critical role for BAMs in mediating PD pathogenesis through their essential role in the orchestration of the -syn-mediated neuroinflammatory response.

neuroscience↗

bioRxiv2022

Metagenomics of Parkinson's disease implicates the gut microbiome in multiple disease mechanisms

Parkinsons disease (PD) may start in the gut and spread to the brain. To investigate the role of gut microbiome, we enrolled 490 PD and 234 control individuals, conducted deep shotgun sequencing of fecal DNA, followed by metagenome-wide association studies requiring significance by two methods (ANCOM-BC and MaAsLin2) to declare disease association. Thirty-percent of species and pathways tested had altered abundances in PD, depicting a widespread dysbiosis. Network analysis showed PD-associated species form polymicrobial clusters that grow or shrink together, and some compete. Metagenomic profile of PD indicates a disease permissive microbiome, evidenced by overabundance of pathogens and immunogenic components, dysregulated neuroactive signaling, preponderance of molecules that induce alpha-synuclein pathology, and over-production of toxicants; with the reduction in anti-inflammatory and neuroprotective factors limiting the capacity to recover. These data provide a broad foundation with a wealth of concrete testable hypotheses to discern the role of the gut microbiome in PD.

genomics↗

bioRxiv2022

Unaltered T cell responses to common antigens in individuals with Parkinson's disease

Background and ObjectivesParkinsons disease (PD) is associated with a heightened inflammatory state, including activated T cells. However, it is unclear whether these PD T cell responses are antigen specific or more indicative of generalized hyperresponsiveness. Our objective was to measure and compare antigen-specific T cell responses directed towards antigens derived from commonly encountered human pathogens/vaccines in patients with PD and age-matched healthy controls (HC). MethodsPeripheral blood mononuclear cells (PBMCs) from 20 PD patients and 19 age-matched HCs were screened. Antigen specific T cell responses were measured by flow cytometry using a combination of the activation induced marker (AIM) assay and intracellular cytokine staining. ResultsHere we show that both PD patients and HCs show similar T cell activation levels to several antigens derived from commonly encountered human pathogens/vaccines in the general population. Similarly, we also observed no difference between HC and PD in the levels of CD4 and CD8 T cell derived cytokines produced in response to any of the common antigens tested. These antigens encompassed both viral (coronavirus, rhinovirus, respiratory syncytial virus, influenza, cytomegalovirus) and bacterial (pertussis, tetanus) targets. ConclusionsThese results suggest the T cell dysfunction observed in PD may not extend itself to abnormal responses to commonly encountered or vaccine-target antigens. Our study supports the notion that the targets of inflammatory T cell responses in PD may be more directed towards autoantigens like -synuclein (-syn) rather than common foreign antigens.

immunology↗

bioRxiv2021

RORγt-Expressing Pathogenic CD4+T Cells Cause Brain Inflammation During Chronic Colitis

Neurobehavioral disorders and brain abnormalities have been extensively reported in both Crohns Disease (CD) and Ulcerative Colitis (UC) patients. However, the mechanism causing neuropathological disorders in inflammatory bowel disease (IBD) patients remains unknown. Studies have linked the Th17 subset of CD4+T cells to brain diseases associated with neuroinflammation and cognitive impairment, including multiple sclerosis (MS), ischemic brain injury and Alzheimers disease. To better understand how CD4+T lymphocytes, contribute to brain pathology in chronic intestinal inflammation, we investigated the development of brain inflammation in the T cell transfer model of chronic colitis. Our findings demonstrate that CD4+T cells infiltrate the brain of colitic Rag1-/- mice in proportional levels to colitis severity. Colitic mice developed hypothalamic astrogliosis that correlated with neurobehavioral disorders. Moreover, the brain-infiltrating CD4+T cells expressed Th17 cell transcription factor ROR{gamma}t and displayed a pathogenic Th17 cellular phenotype similar to colonic Th17 cells. Adoptive transfer of ROR{gamma}t-deficient naive CD4+T cells failed to cause brain inflammation and neurobehavioral disorders in Rag1-/- recipients, with significantly less brain infiltration of CD4+T cells. These findings suggest that pathogenic ROR{gamma}t+CD4+T cells that aggravate colitis migrate preferentially into the brain, contributing to brain inflammation and neurobehavioral disorders, thereby linking colitis severity to neuroinflammation.

immunology↗

bioRxiv2021

Transcriptional analysis of peripheral memory T cells reveals Parkinson's disease-specific gene signatures

Parkinsons disease (PD) is a multi-stage neurodegenerative disorder with largely unknown etiology. Recent findings have identified PD-associated autoimmune features including roles for T cells. To further characterize the role of T cells in PD, we performed RNA sequencing on PBMC and peripheral CD4 and CD8 memory T cell subsets derived from PD patients and age-matched healthy controls. When the groups were stratified by their T cell responsiveness to alpha-synuclein (-syn) as a proxy for ongoing inflammatory autoimmune response, the study revealed a broad differential gene expression profile in memory T cell subsets and a specific PD associated gene signature. We identified a significant enrichment of transcriptomic signatures previously associated with PD, including for oxidative stress, phosphorylation, autophagy of mitochondria, cholesterol metabolism and inflammation, and the chemokine signaling proteins CX3CR1, CCR5 and CCR1. In addition, we identified genes in these peripheral cells that have previously been shown to be involved in PD pathogenesis and expressed in neurons, such as LRRK2, LAMP3, and aquaporin. Together, these findings suggest that features of circulating T cells with -syn-specific responses in PD patients provide insights into the interactive processes that occur during PD pathogenesis and suggest potential intervention targets.

immunology↗

bioRxiv2021

Human-genome gut-microbiome interaction in Parkinson's disease

The causes of complex diseases remain an enigma despite decades of epidemiologic research on environmental risks and genome-wide studies that have uncovered tens or hundreds of susceptibility loci for each disease. We hypothesize that the microbiome is the missing link. Genetic studies have shown that overexpression of alpha-synuclein, a key pathological protein in Parkinsons disease (PD), can cause familial PD and variants at alpha-synuclein locus confer risk of idiopathic PD. Recently, dysbiosis of gut microbiome in PD was identified: altered abundances of three microbial clusters were found, one of which was composed of opportunistic pathogens. Using two large datasets, we show that the overabundance of opportunistic pathogens in PD gut is influenced by the host genotype at the alpha-synuclein locus, and that the variants responsible modulate alpha-synuclein expression. This is the first demonstration of interaction between genetic factors in the human genome and the dysbiosis of gut microbiome in PD.

genetics↗

bioRxiv2020

Characterizing dysbiosis of gut microbiome in PD: Evidence for overabundance of opportunistic pathogens

In Parkinsons disease (PD), gastrointestinal features are common and often precede the motor signs. Braak and colleagues proposed that PD may start in the gut, triggered by a pathogen, and spread to the brain. Numerous studies have examined the gut microbiome in PD, all found it to be altered, but found inconsistent results on associated microorganisms. Studies to date have been small (N=20 to 306) and are difficult to compare or combine due to varied methodology. We conducted a microbiome-wide association study (MWAS) with two large datasets for internal replication (N=333 and 507). We used uniform methodology when possible, interrogated confounders, and applied two statistical tests for concordance, followed by correlation network analysis to infer interactions. Fifteen genera were associated with PD at a microbiome-wide significance level, in both datasets, with both methods, with or without covariate adjustment. The associations were not independent, rather represented 3 clusters of co-occurring microorganisms. Cluster 1 was composed of opportunistic pathogens; all were elevated in PD. Cluster 2 were short-chain-fatty-acid producing bacteria; all were reduced in PD. Cluster 3 were carbohydrate-metabolizing probiotics; elevated in PD. Depletion of anti-inflammatory short-chain-fatty-acid producing bacteria and elevated levels of probiotics are confirmatory. Overabundance of opportunistic pathogens is a novel finding and their identity provides a lead to experimentally test their role in PD.

genomics↗