Biology subjects

Drouin-Ouellet, J.

Publications and source records attributed to Drouin-Ouellet, J..

8 recordsLinked to original sources

bioRxiv2026

Age-dependent mitochondrial health decline in human induced neurons

Introduction: In humans, aging is associated with an increased risk of developing neurodegenerative diseases such as Parkinson's disease (PD) and Alzheimer's disease (AD). In neurons, the effect of aging on intrinsic molecular processes, and how they tie to age-related neurodegeneration remains unclear. Animal studies have shown that mitochondrial function decline, autophagy impairment and defective elimination of damaged mitochondria by mitophagy are all central features of neuronal aging. However, very few studies have investigated such events in human neurons, due to a lack of models showing aging features. Therefore, there is a crucial need for a better understanding of the effect of aging on neuronal health. Methods: Here, we use direct neuronal reprogramming, which maintains signatures of cellular aging, to study the effect of aging on mitochondrial health and mitophagy in human neurons derived from healthy donors ranging from 11 to 91 years old. We use confocal imaging to assess colocalization of mitochondria with autophagic structures following mitophagy induction. Results: We show age-related mitochondrial impairment in neurites of induced neurons (iNs) derived from older donors. Additionally, in these neurites, we show an accumulation of mitochondria targeted for degradation in autophagosomes and LAMP1-positive lysosome vesicles following mitophagy induction. These impairments culminate into incomplete elimination of damaged mitochondria, despite preserved activity of the lysosomal enzymes assessed. Conclusions: This study shows for the first time age-related mitophagy impairment in human neurons, and confirms findings of age-related mitochondrial impairments in human neurons. By doing so, this study paves the way for more in-depth mechanistic studies that would allow for the identification of therapeutic targets for anti-aging treatment and in the context of age-associated neurodegenerative diseases.

neuroscience↗

bioRxiv2026

Myeloid PINK1 represses mtDNA release and immune signaling that impacts neuronal pathology in patient-derived idiopathic PD models

Parkinsons disease (PD) is a neurodegenerative disorder marked by the development of cardinal motor deficits preceded by a protracted prodromal period of non-motor symptoms often involving the gastrointestinal (GI) tract. There is an emerging consensus that both the peripheral immune system and local neuroinflammation play key roles in the etiology of PD. We previously demonstrated a critical function for the Parkinsons related proteins PINK1 and Parkin as repressors of the innate to adaptive immune response in cultured cells and mouse models of infection. However, it remained unclear whether these processes were conserved in patient-derived models, and precisely how immune signaling may ultimately drive the death of dopaminergic neurons. Here we show that GI infection of PINK1 knockout (KO) mice triggered acute neurodegeneration which was evident early in the enteric nervous system. Treating wild type enteric or dopaminergic neurons with conditioned medium from immune-stimulated PINK1 KO macrophages was sufficient to promote neuronal disruption in both mouse and human neurons in vitro. Within immune-activated macrophages, we reveal that loss of PINK1 led to an enhanced release of mitochondrial DNA (mtDNA) within mitochondrial derived vesicles, leading to the activation of cGAS/STING pathways. These changes were seen in both mouse/human in vitro models and in PD patient-derived primary macrophages. Notably, pharmacological modulation using a PINK1 activator with high therapeutic potential attenuated pro-inflammatory profiles elicited by the mtDNA-dependent STING/NF-{kappa}B pathway in idiopathic patient-derived macrophages. Ultimately, our study lays the foundation for understanding PINK1-related peripheral macrophage mechanisms in idiopathic PD and provides a target for further development to treat the disease at early stages. Graphical abstractPINK1-related immune mechanisms of Parkinsons disease and associations with early neurodegenerative events. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/694713v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@6f6488org.highwire.dtl.DTLVardef@13139aaorg.highwire.dtl.DTLVardef@c0d4d1org.highwire.dtl.DTLVardef@1d41e25_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2025

Phosphoproteomic profiling reveals post-translational dysregulation in Huntington's disease patient-derived neurons

Huntingtons disease (HD) is a fatal neurodegenerative disorder caused by a CAG repeat expansion in the Huntingtin (HTT) gene. Although transcriptomic and proteomic changes have been characterized in patient-derived neurons, the contribution of post-translational modifications (PTMs), such as phosphorylation, remains poorly understood. Here, we present the first phosphoproteomic analysis by mass spectrometry (P-MS) of human induced neurons (iNs) directly reprogrammed from HD patient fibroblasts. We identified 177 phosphopeptides with significantly altered abundance in HD-iNs, mapping to phosphoproteins associated with key signaling pathways known to be affected in HD, such as splicing and autophagy. By integrating P-MS data with previously published proteomic and transcriptomic data from the same donors, we identified distinct subsets of ON-OFF phosphopeptides that exhibited a complete loss of phosphorylation in either HD- or Ctrl-iNs, without corresponding changes at the RNA or protein level. An exception was MXRA8, previously described in glial cells as a mediator of blood-brain barrier integrity and astrocyte-mediated neuroinflammation. This protein showed increased protein abundance despite the absence of phosphorylation in HD- iNs, suggesting a compensatory mechanism - a pattern also observed in human post mortem cortical HD tissue. Additionally, MXRA8 showed altered protein-protein interactions with lysosomal and metabolic regulators in HD-iNs, highlighting its potential role in autophagy impairment as well as in neurovascular dysfunction. These findings uncover a distinct layer of post-translational dysregulation in HD, suggesting that phospho-switch proteins such as MXRA8 may be candidate effectors of pathology and thus site-specific phosphorylation loss may contribute to impaired signaling and proteostasis in human HD neurons.

neuroscience↗

bioRxiv2024

Chemically induced senescence prompts functional changes in human microglia-like cells

In response to various stressors, cells can enter a state called cellular senescence which is characterized by irreversible cell cycle arrest and a senescence-associated secretory phenotype (SASP). The progressive accumulation of senescent glial cells in the central nervous system (CNS) with aging suggests a potential role for senescence as driver of aging and inflammation in the brain. As the main immune cell population residing in the CNS, microglia are thought to play a pivotal role in the progression of age-associated neuroinflammation. Furthermore, due to their slow turnover, microglia are highly susceptible to undergoing cellular senescence. However, current understanding of age-related changes in microglia and their impact on brain aging is limited. Due to the challenge in accessing human primary microglia and the lack of models to adequately recapitulate aging, this knowledge is predominantly limited to rodent studies. Here, we chemically induced senescence in a human immortalized microglia cell line with a cocktail of senescence-inducing molecules. We demonstrate that chemically induced senescent microglia adopt a pro-inflammatory phenotype, have reduced phagocytic activity and impaired calcium activity. Our results show that chemically induced senescence can mimic features of cellular aging and can provide insight on the impact of aging and cellular senescence on human microglia.

neuroscience↗

bioRxiv2021

Age-related pathological impairments in induced neurons derived from patients with idiopathic Parkinson's disease

Understanding the pathophysiology of Parkinsons disease has been hampered by the lack of models that recapitulate all the critical factors underlying its development. Here, we generated functional induced dopaminergic neurons (iDANs) that were directly reprogrammed from adult human dermal fibroblasts of patients with idiopathic Parkinsons disease to investigate diseaserelevant pathology. We show that iDANs derived from Parkinsons disease patients exhibit lower basal chaperone-mediated autophagy as compared to iDANs of healthy donors. Furthermore, stress-induced autophagy resulted in an accumulation of macroautophagic structures in induced neurons (iNs) derived from Parkinsons disease patients, independently of the specific neuronal subtype but dependent on the age of the donor. Finally, we found that these impairments in patient-derived iNs lead to an accumulation of phosphorylated alpha-synuclein, a hallmark of Parkinsons disease pathology. Taken together, our results demonstrate that direct neural reprogramming provides a patient-specific model to study aged neuronal features relevant to idiopathic Parkinsons disease.

neuroscience↗

bioRxiv2021

Distinct sub-cellular autophagy impairments occur independently of protein aggregation in induced neurons from patients with Huntington's disease

Huntingtons disease (HD) is a neurodegenerative disorder caused by CAG expansions in the huntingtin (HTT) gene. Modelling HD has remained challenging, as rodent and cellular models poorly recapitulate the disease. To address this, we generated induced neurons (iNs) through direct reprogramming of human skin fibroblasts, which retain age-dependent epigenetic characteristics. HD-iNs displayed profound deficits in autophagy, characterised by reduced transport of late autophagic structures from the neurites to the soma. The neurite-specific alterations in autophagy resulted in shorter, thinner and fewer neurites presented by HD-iNs. CRISPRi-mediated silencing of HTT did not rescue this phenotype but rather resulted in additional autophagy alterations in ctrl-iNs, highlighting the importance of wild type HTT in neuronal autophagy. In summary, our work identifies a distinct subcellular autophagy impairment in aged patient derived HD-neurons and provides a new rational for future development of autophagy activation therapies.

neuroscience↗

bioRxiv2020

Neural tube patterning: from a minimal model for rostrocaudal patterning towards an integrated 3D model

The rostrocaudal patterning of the neural tube is a key event in early brain development. This process is mainly driven by a gradient of WNT, which defines the fate of the present neural progenitor cells in a dose dependent matter and leads to a subdivision of the tube into forebrain, midbrain and hindbrain. Although this process is extensively studied experimentally both in vivo and in vitro, an integrated view of the responsible genetic circuitry is currently lacking. In this work, we present a minimal gene regulatory model for rostrocaudal neural tube patterning. The model's nodes and architecture are determined in a data driven way, leading to a tristable configuration of mutually repressing brain regions. Analysis of the parameter sensitivity and simulations of knockdown and overexpression cases show that repression of hindbrain fate is a promising strategy for the improvement of current protocols for the generation of dopaminergic neurons in vitro. Furthermore, we combine the model with an existing model for dorsoventral neural tube patterning, to test its capabilities in an in vivo setting, by predicting the steady state pattern of a realistic three-dimensional neural tube. This reveals that the rostrocaudal pattern stacks dorsoventrally in the caudal half of the neural tube. Finally, we simulate morphogen secretion overexpression, which highlights the sensitivity of neural tube patterning to the morphogen levels.

systems biology↗

bioRxiv2020

A Quantitative Model of Cellular Decision Making in Direct Neuronal Reprogramming

The direct reprogramming of adult skin fibroblasts to neurons is thought to be controlled by a small set of interacting gene regulators. Here, we investigate how the interaction dynamics between these regulating factors coordinate cellular decision making in direct neuronal reprogramming. We put forward a quantitative model of the governing gene regulatory system, supported by measurements of mRNA expression level dynamics. We find that reinterpreting the interaction between two genes (PTB and nPTB) is necessary to capture quantitative gene interaction dynamics and correctly predict the outcome of various overexpression and knockdown experiments. This analysis is strengthened by a novel analytical technique to dissect system behaviour and reveal the influence of individual factors on resulting gene expression. Overall, we demonstrate that computational analysis is a powerful tool for understanding the mechanisms of direct (neuronal) reprogramming, paving the way for future models that can help improve cell conversion strategies.

systems biology↗