Alpha‐synuclein fibrils amplified from multiple system atrophy and Parkinson's disease patient brain spread after intracerebral injection into mouse brain

Parkinson's disease (PD), multiple system atrophy (MSA), and dementia with Lewy bodies (DLB) are neurodegenerative disorders with alpha-synuclein (α-syn) aggregation pathology. Different strains of α-syn with unique properties are suggested to cause distinct clinical and pathological manifestations resulting in PD, MSA, or DLB. To study individual α-syn spreading patterns, we injected α-syn fibrils amplified from brain homogenates of two MSA patients and two PD patients into the brains of C57BI6/J mice. Antibody staining against pS129-α-syn showed that α-syn fibrils amplified from the brain homogenates of the four different patients caused different levels of α-syn spreading. The strongest α-syn pathology was triggered by α-syn fibrils of one of the two MSA patients, followed by comparable pS129-α-syn induction by the second MSA and one PD patient material. Histological analysis using an antibody against Iba1 further showed that the formation of pS129-α-syn is associated with increased microglia activation. In contrast, no differences in dopaminergic neuron numbers or co-localization of α-syn in oligodendrocytes were observed between the different groups. Our data support the spreading of α-syn pathology in MSA, while at the same time pointing to spreading heterogeneity between different patients potentially driven by individual patient immanent factors

miR-182-5p and miR-183-5p Act as GDNF Mimics in Dopaminergic Midbrain Neurons.

Parkinson’s disease (PD) is the second-most-frequent neurodegenerative disorder worldwide. One major hallmark of PD is the degeneration of dopaminergic (DA) neurons in the substantia nigra. Glial cell line-derived neurotrophic factor (GDNF) potently increases DA neuron survival in models of PD; however, the underlying mechanisms are incompletely understood. MicroRNAs (miRNAs) are small, non-coding RNAs that are important for post-transcriptional regulation of gene expression. Using small RNA sequencing, we show that GDNF specifically increases the expression of miR-182-5p and miR-183-5p in primary midbrain neurons (PMNs). Transfection of synthetic miR-182-5p and miR-183-5p mimics leads to increased neurite outgrowth and mediates neuroprotection of DA neurons in vitro and in vivo, mimicking GDNF effects. This is accompanied by decreased expression of FOXO3 and FOXO1 transcription factors and increased PI3K-Akt signaling. Inhibition of endogenous miR-182-5p or miR-183-5p in GDNF-treated PMNs attenuated the pro-DA effects of GDNF. These findings unveil an unknown miR-mediated mechanism of GDNF action and suggest that targeting miRNAs is a new therapeutic avenue to PD phenotypes

msqrob2PTM: differential abundance and differential usage analysis of MS-based proteomics data at the post-translational modification and peptidoform level

Abstract In the era of open-modification search engines, more post-translational modifications than ever can be detected by LC-MS/MS-based proteomics. This development can switch proteomics research into a higher gear, as PTMs are key in many cellular pathways important in cell proliferation, migration, metastasis and ageing. However, despite these advances in modification identification, statistical methods for PTM-level quantification and differential analysis have yet to catch up. This absence can partly be explained by the inherently low abundance of many PTMs and the confounding of PTM intensities with its parent protein abundance. Therefore, we have developed msqrob2PTM, a new workflow in the msqrob2 universe capable of differential abundance analysis at the PTM, and at the peptidoform level. The latter is important for validating PTMs found as significantly differential. Indeed, as our method can deal with multiple PTMs per peptidoform, there is a possibility that significant PTMs stem from one significant peptidoform carrying another PTM, hinting that it might be the other PTM driving the perceived differential abundance. Our workflows can flag both Differential Peptidoform (PTM) Abundance (DPA) and Differential Peptidoform (PTM) Usage (DPU). This enables a distinction between direct assessment of differential abundance of peptidoforms (DPA) and differences in the relative usage of peptidoforms corrected for corresponding protein abundances (DPU). For DPA, we directly model the log2-transformed peptidoform (PTM) intensities, while for DPU, we correct for parent protein abundance by an intermediate normalisation step which calculates the log2-ratio of the peptidoform (PTM) intensities to their summarized parent protein intensities. We demonstrated the utility and performance of msqrob2PTM by applying it to datasets with known ground truth, as well as to biological PTM-rich datasets. Our results show that msqrob2PTM is on par with, or surpassing the performance of, the current state-of-the-art methods. Moreover, msqrob2PTM is currently unique in providing output at the peptidoform level

Metal dyshomeostasis in the substantia nigra of patients with Parkinson's disease or multiple sclerosis

International audienceAbstractAbnormal metal distribution in vulnerable brain regions is involved in the pathogenesis of most neurodegenerative diseases, suggesting common molecular mechanisms of metal dyshomeostasis. This study aimed to compare the intra‐ and extra‐neuronal metal content and the expression of proteins related to metal homeostasis in the substantia nigra (SN) from patients with Parkinson's disease (PD), multiple sclerosis (MS), and control subjects. Metal quantification was performed via ion‐beam micro‐analysis in neuromelanin‐positive neurons and the surrounding tissue. For proteomic analysis, SN tissue lysates were analyzed on a nanoflow chromatography system hyphenated to a hybrid triple‐quadrupole time‐of‐flight mass spectrometer. We found increased amounts of iron in neuromelanin‐positive neurons and surrounding tissue in patients with PD and MS compared to controls (4‐ to 5‐fold higher) that, however, also showed large inter‐individual variations. Copper content was systematically lower (−2.4‐fold) in neuromelanin‐positive neurons of PD patients compared with controls, whereas it remained unchanged in MS. Protein–protein interaction (PPI) network analyses revealed clusters related to Fe and Cu homeostasis among PD‐deregulated proteins. An enrichment for the term “metal homeostasis” was observed for MS‐deregulated proteins. Important deregulated hub proteins included hemopexin and transferrin in PD, and calreticulin and ferredoxin reductase in MS. Our findings show that PD and MS share commonalities in terms of iron accumulation in the SN. Concomitant proteomics experiments revealed PPI networks related to metal homeostasis, substantiating the results of metal quantification.</jats:p

miR-182-5p and miR-183-5p Act as GDNF Mimics in Dopaminergic Midbrain Neurons

Parkinson’s disease (PD) is the second-most-frequent neurodegenerative disorder worldwide. One major hallmark of PD is the degeneration of dopaminergic (DA) neurons in the substantia nigra. Glial cell line-derived neurotrophic factor (GDNF) potently increases DA neuron survival in models of PD; however, the underlying mechanisms are incompletely understood. MicroRNAs (miRNAs) are small, non-coding RNAs that are important for post-transcriptional regulation of gene expression. Using small RNA sequencing, we show that GDNF specifically increases the expression of miR-182-5p and miR-183-5p in primary midbrain neurons (PMNs). Transfection of synthetic miR-182-5p and miR-183-5p mimics leads to increased neurite outgrowth and mediates neuroprotection of DA neurons in vitro and in vivo, mimicking GDNF effects. This is accompanied by decreased expression of FOXO3 and FOXO1 transcription factors and increased PI3K-Akt signaling. Inhibition of endogenous miR-182-5p or miR-183-5p in GDNF-treated PMNs attenuated the pro-DA effects of GDNF. These findings unveil an unknown miR-mediated mechanism of GDNF action and suggest that targeting miRNAs is a new therapeutic avenue to PD phenotypes

Alpha-synuclein fibrils amplified from multiple system atrophy and Parkinsons disease patient brain spread after intracerebral injection into mouse brain.

Parkinsons disease (PD), multiple system atrophy (MSA), and dementia with Lewy bodies (DLB) are neurodegenerative disorders with alpha-synuclein (α-syn) aggregation pathology. Different strains of α-syn with unique properties are suggested to cause distinct clinical and pathological manifestations resulting in PD, MSA, or DLB. To study individual α-syn spreading patterns, we injected α-syn fibrils amplified from brain homogenates of two MSA patients and two PD patients into the brains of C57BI6/J mice. Antibody staining against pS129-α-syn showed that α-syn fibrils amplified from the brain homogenates of the four different patients caused different levels of α-syn spreading. The strongest α-syn pathology was triggered by α-syn fibrils of one of the two MSA patients, followed by comparable pS129-α-syn induction by the second MSA and one PD patient material. Histological analysis using an antibody against Iba1 further showed that the formation of pS129-α-syn is associated with increased microglia activation. In contrast, no differences in dopaminergic neuron numbers or co-localization of α-syn in oligodendrocytes were observed between the different groups. Our data support the spreading of α-syn pathology in MSA, while at the same time pointing to spreading heterogeneity between different patients potentially driven by individual patient immanent factors

Brain iron enrichment attenuates α‐synuclein spreading after injection of preformed fibrils

Regional iron accumulation and α‐synuclein (α‐syn) spreading pathology within the central nervous system are common pathological findings in Parkinson's disease (PD). Whereas iron is known to bind to α‐syn, facilitating its aggregation and regulating α‐syn expression, it remains unclear if and how iron also modulates α‐syn spreading. To elucidate the influence of iron on the propagation of α‐syn pathology, we investigated α‐syn spreading after stereotactic injection of α‐syn preformed fibrils (PFFs) into the striatum of mouse brains after neonatal brain iron enrichment. C57Bl/6J mouse pups received oral gavage with 60, 120, or 240 mg/kg carbonyl iron or vehicle between postnatal days 10 and 17. At 12 weeks of age, intrastriatal injections of 5‐µg PFFs were performed to induce seeding of α‐syn aggregates. At 90 days post‐injection, PFFs‐injected mice displayed long‐term memory deficits, without affection of motor behavior. Interestingly, quantification of α‐syn phosphorylated at S129 showed reduced α‐syn pathology and attenuated spreading to connectome‐specific brain regions after brain iron enrichment. Furthermore, PFFs injection caused intrastriatal microglia accumulation, which was alleviated by iron in a dose‐dependent way. In primary cortical neurons in a microfluidic chamber model in vitro, iron application did not alter trans‐synaptic α‐syn propagation, possibly indicating an involvement of non‐neuronal cells in this process. Our study suggests that α‐syn PFFs may induce cognitive deficits in mice independent of iron. However, a redistribution of α‐syn aggregate pathology and reduction of striatal microglia accumulation in the mouse brain may be mediated via iron‐induced alterations of the brain connectome

Multiomic ALS signatures highlight sex differences and molecular subclusters and identify the MAPK pathway as therapeutic target

Abstract Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disease and lacks effective disease-modifying treatments. Here, we performed a multiomic analysis of the prefrontal cortex of 51 patients with sporadic ALS and 50 control subjects, as well as four transgenic mouse models of C9orf72-, SOD1-, TDP-43-, and FUS-ALS to characterize early and sex-specific disease mechanisms in ALS. Integrated analyses of transcriptomes, (phospho)proteomes, and miRNAomes revealed more pronounced changes in male patients. We identified transcriptome-based human ALS subclusters driven by the immune response, extracellular matrix, mitochondrial respiration, and RNA metabolism. The molecular signatures of human subclusters were reflected in specific mouse models. Individual and integrative multiomics analyses highlighted the mitogen-activated protein kinase pathway as an early disease-relevant mechanism. Its modulation by trametinib in vitro and in vivo validated that mitogen-activated protein kinase kinase 2 is a promising therapeutic target with beneficial effects in female patients