Biology subjects

Gasser, T.

Publications and source records attributed to Gasser, T..

15 recordsLinked to original sources

bioRxiv2026

Glycosylation of anandamide and other bioactive N-acylethanolamines in mammalian cells and tissues

N-acylethanolamines (NAEs), including the endocannabinoid anandamide, are bioactive fatty acid amides that are normally hydrolyzed by fatty acid amide hydrolase (FAAH) or N-acyl acid amidohydrolase (NAAA). Strikingly, when canonical NAE degradation is blocked, NAE levels do not increase indefinitely but instead reach a plateau. This apparent metabolic ceiling suggests that additional, underexplored pathways contribute to NAE homeostasis. Identifying these pathways is essential to determine whether NAEs are converted into inactive metabolites or products with distinct biological properties. Here, we identify NAE glycosylation as a metabolic pathway that links endocannabinoid-related lipid metabolism to glycosphingolipid turnover. We synthesized glycosylated NAEs and their isotope-encoded standards and developed targeted LC-MS/MS assays to monitor their enzymatic processing and quantify their abundance in mouse and human cells, tissues, and plasma. We show that non-lysosomal glucosylceramidase GBA2 transfers glucose or galactose to anandamide, N-oleoylethanolamine and N-palmitoylethanolamine, and lysosomal glucosylceramidase GCase hydrolyses {beta}-Glycosylated-NAEs ({beta}-Glyco-NAE) back to their parent NAEs. {beta}-Glyco-NAEs occur endogenously in macrophages and neuronal cells, increase when canonical NAE degradation is impaired, and accumulate in human samples with GCase deficiency, including Gaucher disease and GBA1-associated Parkinsons disease. {beta}-Glyco-NAEs do not engage the cannabinoid receptors, TRPV1, or PPAR, and potentiate inflammatory cytokine release, including IL6 and TNF, from microglia. Based on these findings, we pose that GBA2-dependent NAE glycosylation may constitute an overflow lipid-remodeling pathway that connects NAE metabolism to lysosomal dysfunction, inflammation and neurodegeneration.

biochemistry↗

bioRxiv2026

Comprehensive investigation of AAV tropism across human iPSC-derived neuronal subtypes

Recombinant Adeno-associated viruses (AAVs) are widely used for gene delivery in the central nervous system and have become central tools in both gene therapy and basic neuroscience research. However, although AAV serotypes have been extensively characterized in rodent models, their performance in human neurons, particularly those derived from induced pluripotent stem cells (iPSCs), remains poorly characterized. While human iPSC-derived neurons are increasingly used for disease modeling and drug screening, their susceptibility to viral transduction varies and remains difficult to predict. In this study, we systematically evaluated the transduction efficiency and toxicity profiles of 18 wild-type and engineered AAV serotypes across three distinct types of iPSC-derived neurons, relevant to disease modeling and drug discovery: cortical projection neurons, NGN2- induced forebrain-like neurons, and dopaminergic neurons and four doses (1E3, 1E4, 1E5 and 2E5 genome copies per cell). Using automated high-throughput confocal imaging and quantification of reporter gene expression, we identified several serotypes with robust and efficient transduction across all neuronal subtypes. Among these, three serotypes AAV6, AAV6.2 and AAV2.7m8 showed consistently high performance. To assess safety, we quantified cell number and neurite morphology, finding that while high transduction and gene expression correlate with toxicity, sensitivity varied across neuronal subtypes, with NGN2 neurons being most vulnerable and dopaminergic neurons most resilient. Finally, we validated our findings in a more complex 3D model by testing one of the best-performing serotypes, AAV2.7m8, in both whole and dissociated human cerebellar organoids. Together, our results establish a benchmark dataset for AAV performance in human iPSC- derived neurons and provide practical guidance for AAV based gene delivery in human in vitro neural models. This resource will be valuable for both basic research and preclinical applications aiming to manipulate gene expression in human neurons and understanding AAV tropism in disease-relevant cell types.

neuroscience↗

bioRxiv2025

PINK1 regulates cholesterol homeostasis via SCAP phosphorylation in human dopaminergic neurons

Cholesterol is a key lipid enriched in neuronal membranes and essential for signaling and synaptic transmission. An imbalance in cholesterol levels may affect synaptic plasticity and contribute to neurodegeneration. Here, we identify in human dopaminergic neurons a mechanism linking loss of function of the Parkinsons disease (PD) gene PINK1 to altered cholesterol homeostasis. Loss of functional PINK1 impaired SCAP phosphorylation at Ser822 and Ser838, stabilizing SCAP and driving excess cholesterol biosynthesis. Cholesterol accumulated at the plasma membrane and in flotillin-rich lipid rafts, causing reduced neurotransmitter uptake and altering the distribution of dopamine transporter (DAT). Restoring PINK1 expression normalized cholesterol biosynthesis and levels. Moreover, the cholesterol-lowering drugs simvastatin and {beta}-cyclodextrin rescued DAT distribution and neurotransmitter uptake defects. These findings demonstrate that PINK1 influences cholesterol homeostasis through SCAP phosphorylation at Ser822 and Ser838 and that restoring cholesterol levels mitigates phenotypes observed in PINK1 PD neurons. These findings further highlight the cross-talk between mitochondria and lipid homeostasis in PD models, underscoring the relevance of cholesterol levels to dopaminergic functions. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/672574v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@165b4d4org.highwire.dtl.DTLVardef@42e3a2org.highwire.dtl.DTLVardef@16ea6f7org.highwire.dtl.DTLVardef@193e170_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG

neuroscience↗

bioRxiv2025

The Parkinsons disease associated Leucine-rich repeat kinase 2 affects expression of Transferrin receptor 1 and phosphorylation of key signaling proteins in human iPSC-derived dopaminergic neurons

Several variants in the Leucine-rich repeat kinase 2 (LRRK2) gene account for familiar and sporadic late-onset Parkinsons disease (PD). LRRK2 is a large, multifunctional kinase involved in different intracellular pathways crucial for homeostasis and cell survival. One of the poorly understood mechanisms of Parkinsonism is the iron accumulation in Substantia nigra pars compacta (SNc). Transferrin receptor 1 (TfR) plays a significant role for iron uptake into the cell. Here, we investigated the expression of TfR in human induced pluripotent stem cell (iPSC)-derived dopaminergic neurons (hDANs) generated from PD patients carrying the LRRK2 p.G2019S form and found dysregulated TfR levels. In addition, we found gene status depending variations of LRRK2 expression in differentiated hDANs, while neuronal progenitor cells (NPCs) did not display these changes. This suggests an unknown regulatory mechanism of LRRK2 expression during dopaminergic differentiation. Further investigations showed dysregulated phosphorylation of the PD-associated GSK-3{beta} und the key signaling factor Akt.

neuroscience↗

bioRxiv2025

Cellular and Extracellular microRNA Dysregulation in LRRK2-Linked Parkinson's Disease

Background and objectiveThe discovery of cell-free micro-RNAs in body fluids has made them a promising biomarker target in the field of neurodegenerative diseases. Although they have been reported to be differentially expressed in biofluids and tissues from sporadic Parkinsons disease patients, it remains unclear whether similar observations can be made in patients with genetic forms of the disease and if miRNA profiles reflect mutation-specific pathogenic pathways. Since induced pluripotent stem cell-derived neurons represent a widely used research model for both sporadic and familial Parkinsons disease, we sought to assess the usability of this model for the identification of differentially expressed cell-free micro-RNAs in the context of the Parkinsons disease-related LRRK2 G2019S mutation in a proof-of-concept study. Materials and methodsWe isolated extracellular vesicles carrying cell-free RNA from patient-derived induced pluripotent stem cells carrying the LRRK2 G2019S mutation and their gene-corrected isogenic controls. After the generation of small-RNA libraries and differential expression analysis, we quantified expression levels of fourteen micro-RNAs in an independent batch of cell-free and cellular RNA via RT-qPCR. Finally, we quantified pRab10 levels as a proxy of LRRK2 activity and correlated observable changes to the miRNA expression levels. ResultsWe successfully isolated extracellular vesicles from induced pluripotent stem cell-derived human dopaminergic neurons. We detected over 2000 different micro-RNAs of which 56 were differentially expressed. Dysregulation of four micro-RNAs was confirmed in an independent batch of cell-free RNA. We discovered a high correlation between changes in the cell-free and cellular micro-RNAomes. Finally, we showed poor correlation between LRRK2 expression or activity and miRNA expression levels. ConclusionsOur results suggest that patients carrying the LRRK2 G2019S mutation display alterations in cellular and cell-free micro-RNA expression levels. Notably, the miRNA changes observed in this study did not follow a linear relationship with LRRK2 expression levels or kinase activity. Validation in larger cohorts will be necessary.

neuroscience↗

bioRxiv2024

The Cellular and Extra-Cellular Proteomic Signature of Human Dopaminergic Neurons Carrying the LRRK2 G2019S Mutation

Extracellular vesicles are easily accessible in various biofluids and allow the assessment of disease-related changes of the proteome. This has made them a promising target for biomarker studies, especially in the field of neurodegeneration where access to diseased tissue is very limited. Genetic variants in the LRRK2 gene have been linked to both familial and sporadic forms of Parkinsons disease. With LRRK2 inhibitors entering clinical trials, there is an unmet need for biomarkers that reflect LRRK2-specific pathology and target engagement. In this study, we used induced pluripotent stem cells derived from a patient with Parkinsons disease carrying the LRRK2 G2019S mutation and an isogenic gene corrected control to generate human dopaminergic neurons. We isolated extracellular vesicles and neuronal cell lysates and characterized their proteomic signature using data-independent acquisition proteomics. We performed differential expression analysis and identified 595 significantly differentially regulated proteins in extracellular vesicles and 3205 in cell lysates. Next, we performed gene ontology enrichment analyses on the dysregulated proteins and found close association to biological processes relevant in neurodegeneration and Parkinsons disease. Finally, we focused on proteins that were dysregulated in both the extracellular and cellular proteomes and provide a list of ten promising biomarker candidates that are functionally relevant in neurodegeneration and linked to LRRK2 associated pathology. Among those was the sonic hedgehog signaling molecule, a protein that has tightly been linked to LRRK2-related disruption of cilia function. In conclusion, we characterized the cellular and extracellular proteome of dopaminergic neurons carrying the LRRK2 G2019S mutation and propose an experimentally based list of promising biomarker candidates for future studies.

neuroscience↗

bioRxiv2024

Single-cell transcriptomic changes in oligodendrocytes and precursors derived from Parkinson's disease patient-iPSCs with LRRK2-G2019S mutation

Despite extensive research, the contribution of the LRRK2 p.G2019S mutation to Parkinsons disease (PD) remains unclear. Recent findings indicate oligodendrocytes (ODCs) and their progenitors are vulnerable in PD pathogenesis. Notably, oligodendrocyte precursor cells (OPCs) exhibit high endogenous expression of LRRK2. We induced PD patient-iPSCs with the LRRK2 p.G2019S mutation into oligodendroglial lineages and performed single-cell RNA sequencing. Cell type composition analysis revealed an increase in OPCs, proliferating OPCs and ciliated ependymal cells in LRRK2 lines, all of which are characterized by LRRK2 expression. Differential expression analysis revealed transcriptomic changes in several pathways, including down-regulation of genes related to myelin assembly in ODCs, semaphorin-plexin pathway in OPCs, and cilium movement in proliferating OPCs. Cell-cell communication analysis identified significant alterations in several signaling pathways including a deactivation of PSAP signaling and an activation of MIF signaling in LRRK2 lines. Additionally, we observed an overall increase in SEMA6 signaling communication in LRRK2 cell lines; however, OPCs derived from these LRRK2 lines specifically lost SEMA6 signaling due to a down-regulation of SEMA6A and PLXNA2. Pseudotemporal trajectory analysis revealed that SHH had significantly altered expression along the pseudotime, accompanied by higher expression levels in LRRK2 lines. We propose that dysfunctional semaphorin-plexin signaling, along with cilia movement and SHH signaling, might represent early events in PD pathology.

neuroscience↗

bioRxiv2023

Using Extracellular miRNA Signatures to Identify Patients with LRRK2-Related Parkinson's Disease

BackgroundMutations in the Leucine Rich Repeat Kinase 2 gene are highly relevant in both sporadic and familial cases of Parkinsons disease. Specific therapies are entering clinical trials but patient stratification remains challenging. Dysregulated microRNA expression levels have been proposed as biomarker candidates in sporadic Parkinsons disease. ObjectiveIn this proof-of concept study we evaluate the potential of extracellular miRNA signatures to identify LRRK2-driven molecular patterns in Parkinsons disease. MethodsWe measured expression levels of 91 miRNAs via RT-qPCR in ten individuals with sporadic Parkinsons disease, ten LRRK2 mutation carriers and eleven healthy controls using both plasma and cerebrospinal fluid. We compared miRNA signatures using heatmaps and t-tests. Next, we applied group sorting algorithms and tested sensitivity and specificity of their group predictions. ResultsmiR-29c-3p was differentially expressed between LRRK2 mutation carriers and sporadic cases, with miR-425-5p trending towards significance. Individuals clustered in principal component analysis along mutation status. Group affiliation was predicted with high accuracy in the prediction models (sensitivity up to 89%, specificity up to 70%). miRs-128-3p, 29c-3p, 223-3p and 424-5p were identified as promising discriminators among all analyses. ConclusionsLRRK2 mutation status impacts the extracellular miRNA signature measured in plasma and separates mutation carriers from sporadic Parkinsons disease patients. Monitoring LRRK2 miRNA signatures could be an interesting approach to test drug efficacy of LRRK2-targeting therapies. In light of small sample size, the suggested approach needs to be validated in larger cohorts.

neuroscience↗

bioRxiv2023

Single-nucleus RNA-sequencing reveals oligodendrocytes and their progenitors as vulnerable cell types in prefrontal cortex and anterior cingulate of brains with Parkinson's disease

Several prior studies have proposed the involvement of various brain regions and cell types in Parkinsons disease (PD) pathology. Here, we performed snRNA-seq on the prefrontal cortex and anterior cingulate regions from post-mortem control and PD brain tissue. We found a significant association of oligodendrocytes (ODCs) and oligodendrocyte precursor cells (OPCs) with PD-linked risk loci and report several dysregulated genes and pathways, including regulation of tau-protein kinase activity, regulation of inclusion body assembly and protein processing involved in protein targeting to mitochondria. In an independent PD cohort with clinical measures (681 cases and 549 controls), polygenic risk scores derived from the dysregulated genes significantly predicted Montreal Cognitive Assessment (MoCA)-, and Beck Depression Inventory-II (BDI-II)-scores but not motor impairment (UPDRS-III). We extended our analysis of clinical outcome prediction by incorporating three separate datasets that were previously published by different laboratories. In the first dataset from the anterior cingulate cortex, we identified a correlation between ODCs and BDI-II. In the second dataset obtained from the substantia nigra (SN), OPCs displayed notable predictive ability for UPDRS-III. In the third dataset from the SN region, a distinct subtype of OPCs, labeled OPC_ADM, exhibited predictive ability for UPDRS-III. Intriguingly, the OPC_ADM cluster also demonstrated a significant increase in PD samples. These results suggest that by expanding our focus to glial cells, we can uncover region-specific molecular pathways associated with PD symptoms.

neuroscience↗

bioRxiv2020

Bi-allelic variants in TSPOAP1, encoding the active zone protein RIMBP1, cause autosomal recessive dystonia

Dystonia is a debilitating hyperkinetic movement disorder, frequently transmitted as a monogenic trait. Here, we describe homozygous frameshift, nonsense and missense variants in TSPOAP1, encoding the active zone RIM-binding protein 1 (RIMBP1), as a novel genetic cause of autosomal recessive dystonia in seven subjects from three unrelated families. Subjects carrying loss-of-function variants presented with juvenile- onset progressive generalized dystonia, associated with intellectual disability and cerebellar atrophy. Conversely, subjects carrying a pathogenic missense variant (p.Gly1808Ser) presented with isolated adult-onset focal dystonia. In mice, complete loss of RIMBP1, known to reduce neurotransmission, led to motor abnormalities reminiscent of dystonia, decreased Purkinje cell dendritic arborization, and reduced numbers of cerebellar synapses. In vitro analysis of the p.Gly1808Ser variant showed larger spike-evoked calcium transients and enhanced neurotransmission, suggesting that RIMBP1-linked dystonia can be caused by either reduced or enhanced rates of spike-evoked release in relevant neural networks. Our findings establish a direct link between presynaptic RIMBP1 dysfunction and dystonia and highlight the critical role played by well-balanced neurotransmission in motor control and disease pathogenesis.

genetics↗

bioRxiv2020

Interferon-γ signaling synergizes with LRRK2 in human neurons and microglia

Increasing evidence suggests a role for interferons (IFNs) in neurodegeneration. Parkinsons disease (PD) associated kinase LRRK2 has been implicated in IFN type II (IFN) response in infections and nigral neuronal loss. However, whether and how LRRK2 synergizes with IFN-{gamma} still remains unclear. Here, we employed dopaminergic (DA) neurons and microglia differentiated from patient induced pluripotent stem cells to unravel the role of IFN-{gamma} in LRRK2-PD. We show that IFN-{gamma} induces LRRK2 expression in both DA neurons and microglial cells. LRRK2-G2019S, the most common PD-associated mutation, sensitizes DA neurons to IFN-{gamma} by decreasing AKT phosphorylation. IFN-{gamma} suppresses NFAT activity in both neurons and microglia and synergistically enhances LRRK2-induced defects of NFAT activation. Furthermore, LRRK2-G2019S negatively regulates NFAT via calcium and microtubule dynamics. Importantly, we uncover functional consequences of the reduction of NFAT activity in both cell types, namely defects of neurite elongation and alteration of microglial activation profile and motility. We propose that synergistic IFN-{gamma}/LRRK2 activation serves as a direct link between inflammation and neurodegeneration in PD.

neuroscience↗

bioRxiv2019

PINK1 Regulates Dopamine and Lipids at Mitochondria to Maintain Synapses and Neuronal Function

Mitochondrial dysfunction contributes to the pathogenesis of Parkinsons disease but it is not clear why inherent mitochondrial defects lead specifically to the death of dopaminergic neurons of the mid brain. PINK1 is mitochondrial kinase and PINK1 mutations cause early onset Parkinsons disease.\n\nWe found that in neuronal progenitors, PINK1 regulates mitochondrial morphology, mitochondrial contact to the endoplasmic reticulum (ER) and the phosphorylation of Miro1. A compensatory metabolic shift towards lipid synthesis provides mitochondria with the components needed for membrane renewal and oxidative phosphorylation, maintaining the mitochondrial network once mature.\n\nCholesterol is increased by loss of PINK1, promoting overall membrane rigidity. This alters the distribution of phosphorylated DAT at synapses and impairs dopamine uptake. PINK1 is required for the phosphorylation of tyrosine hydroxylase at Ser19, dopamine and calcium homeostasis and dopaminergic pacemaking.\n\nWe suggest a novel mechanism for PINK1 pathogenicity in Parkinsons disease in addition to but not exclusive of mitophagy. We also provide a basis for potential therapeutics by showing that low doses of the cholesterol depleting drug {beta}-cyclodextrin reverse PINK1-specific phenotypes.

neuroscience↗

bioRxiv2019

A genome-wide genetic pleiotropy approach identified shared loci between multiple system atrophy and inflammatory bowel disease

We aimed to identify shared genetic background between multiple system atrophy (MSA) and autoimmune diseases by using the conjFDR approach. Our study showed significant genetic overlap between MSA and inflammatory bowel disease and identified DENND1B, C7, and RSP04 loci, which are linked to significant changes in methylation or expression levels of adjacent genes. We obtained evidence of enriched heritability involving immune/digestive categories. Finally, an MSA mouse model showed dysregulation of the C7 gene in the degenerating midbrain compared to wildtype mice. The results identify novel molecular mechanisms and implicate immune and gut dysfunction in MSA pathophysiology.

genetics↗

bioRxiv2019

Analysis of DNM3 and VAMP4 as genetic modifiers of LRRK2 Parkinsons disease

ObjectiveTo assess genetic modifiers of Parkinsons disease (PD) age at onset (AAO) penetrance in individuals carrying common and rare LRRK2 risk alleles\n\nMethodsWe analysed reported genetic modifier DNM3 rs2421947 in 724 LRRK2 p.G2019S heterozygotes using linear regression of AAO. We meta-analysed our data with previously published data (n=754). VAMP4 is in close proximity to DNM3 and is associated with PD. We analysed the effect of the rs11578699 VAMP4 variant on pG2019S penetrance in 786 LRRK2 p.G2019S heterozygotes. We also evaluated the impact of VAMP4 variants using AAO regression in 4882 patients with PD carrying a common LRRK2 risk variant (rs10878226).\n\nResultsThere was no evidence for linkage disequilibrium between DNM3 rs2421947 and VAMP4 rs11578699. Our linear regression AAO of 724 p.G2019S carriers showed no relationship between DNM3 rs2421947 and AAO (beta = -1.19, p = 0.55, n =708). Meta-analysis with previously published data did not indicate a significant effect on AAO (beta = -2.21, p = 0.083, n = 1304), but there was significant heterogeneity in the analyses of new and previously published data. VAMP4 rs11578699 was nominally associated with AAO in patients dichotomized by the common LRRK2 risk variant rs10878226 (beta=1.68, se=0.81 p=0.037).\n\nInterpretationAnalysis of DNM3 in previously unpublished data does not show an interaction between DNM3 and LRRK2 G2019S for AAO, however the inter-study heterogeneity may indicate ethnic-specific effects of DNM3 rs2421947. Analysis of sporadic PD patients stratified by the PD risk variant rs10878226 indicates a possible interaction between LRRK2 and VAMP4.

genetics↗

bioRxiv2018

Parkinson disease age of onset GWAS: defining heritability, genetic loci and a-synuclein mechanisms

Increasing evidence supports an extensive and complex genetic contribution to Parkinsons disease (PD). Previous genome-wide association studies (GWAS) have shed light on the genetic basis of risk for this disease. However, the genetic determinants of PD age of onset are largely unknown. Here we performed an age of onset GWAS based on 28,568 PD cases. We estimated that the heritability of PD age of onset due to common genetic variation was ~0.11, lower than the overall heritability of risk for PD (~0.27) likely in part because of the subjective nature of this measure. We found two genome-wide significant association signals, one at SNCA and the other a protein-coding variant in TMEM175, both of which are known PD risk loci and a Bonferroni corrected significant effect at other known PD risk loci, INPP5F/BAG3, FAM47E/SCARB2, and MCCC1. In addition, we identified that GBA coding variant carriers had an earlier age of onset compared to non-carriers. Notably, SNCA, TMEM175, SCARB2, BAG3 and GBA have all been shown to either directly influence alpha-synuclein aggregation or are implicated in alpha-synuclein aggregation pathways. Remarkably, other well-established PD risk loci such as GCH1, MAPT and RAB7L1/NUCKS1 (PARK16) did not show a significant effect on age of onset of PD. While for some loci, this may be a measure of power, this is clearly not the case for the MAPT locus; thus genetic variability at this locus influences whether but not when an individual develops disease. We believe this is an important mechanistic and therapeutic distinction. Furthermore, these data support a model in which alpha-synuclein and lysosomal mechanisms impact not only PD risk but also age of disease onset and highlights that therapies that target alpha-synuclein aggregation are more likely to be disease-modifying than therapies targeting other pathways.

genetics↗