1,721,130 research outputs found
Impact of latest 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension: retrospective single center cohort study
No full textImpact of latest 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension: retrospective single center cohort study
No full textHistone deacetylases als therapeutische targets voor amyotrofe laterale sclerose
No full textstatus: Publishe
Influence of vegetation on flow and morphology in the river Allier, France
No full textCivil Engineering and Geoscience
De functionele betekenis van de Notch signaalcascade voor Amyotrofische Laterale Sclerose: een complexe balans tussen goed en slecht.
No full textAmyotrophic lateral sclerosis (ALS) is a devastating late-onset neurodegenerative disease that mainly affects motor neurons. In this disease, motor neuron degeneration is accompanied and aggravated by oligodendroglial pathology and the presence of reactive astrocytes and microglia.
In this PhD thesis, the role of the Notch signaling pathway in ALS was investigated, as this pathway is implicated in several processes that might contribute to the disease, including axonal retraction, microgliosis, astrocytosis, oligodendrocyte precursor cell proliferation and differentiation, and even cell death.
We observed abnormal activation of the Notch signaling pathway in the affected lumbar spinal cord of both SOD1G93A mice, a well-established mouse model of ALS, and patients with sporadic ALS (sALS). This increased Notch signaling activation was particularly evident in reactive astrocytes. In addition, we found that one of the main Notch ligands, namely Jagged-1, was ectopically expressed in reactive astrocytes in the spinal cord from ALS mice and patients, but it was not detected in resting astrocytes.
From Cre-lox mediated modulation experiments in the SOD1G93A mice using ligand-based inactivation approaches, we learned that astrocytic expression of the ligand Jagged-1 is beneficial, since removal further exacerbates Notch pathway activation and accelerates disease progression without affecting disease onset. Ubiquitous deletion of Jagged-1 is beneficial, at least for female SOD1G93A mice, since it delays disease onset and consequently extends survival in female SOD1G93A mice, but not in male SOD1G93A mice. From receptor-based deletion approaches, we learned that ubiquitous deletion of RBPjk, the co-factor crucial for canonical Notch signaling activation through all four Notch receptors, induces early lethality due to gastrointestinal toxicity, and ubiquitous deletion of only the Notch-1 receptor has no effect on the course of disease in the SOD1G93A mouse model, suggesting the importance of other Notch receptors.
Together, these data suggest that aberrant Notch signaling activation is involved in the pathogenesis of ALS, both in sALS patients and in the SOD1G93A mouse model, but plays a rather complex role that potentially consists of both harmful and protective functions. Given the pleiotropic functions of Notch signaling, interference with this pathway as a therapeutic approach must be considered with caution, to circumvent toxic side-effects and effects of disturbing the complex balance between the harmful trans-activation and the protective cis-inhibition.status: Publishe
Onderzoek naar modificatoren van C9ORF72-geïnduceerde pathologie in amyotrofe lateraal sclerose (ALS) in zebravismodellen
No full textAmyotrophic lateral sclerosis (ALS) is an adult onset neurodegenerative disease characterized by progressive degeneration of upper and lower motor neurons. Clinically, patients present with painless subacute focal muscle weakness. The disease is rapidly progressive, generally leading to death in three to five years after symptom onset, and is unfortunately still incurable.
While in most patients the cause of the disease is unknown, genetic mutations explain ±15% of ALS patients. A non-coding GGGGCC repeat expansion in the C9ORF72 gene is the most frequent genetic cause of ALS. The pathological underpinnings of this mutation are still unclear and might encompass three possible mechanisms. First, decreased transcription of the C9ORF72 gene might lead to loss-of-function of the C9orf72 protein, which has a presumed function in autophagy and membrane trafficking. Second, repeat RNA might bind to several RNA binding proteins (RBPs) hence disturbing their function. This is coined 'RNA toxicity'. Third, the repeat sequence itself might undergo unconventional translation into toxic dipeptide repeats (DPRs), called 'DPR toxicity'. As it is clear that C9orf72 loss-of-function is not the main pathogenic driver, a gain-of-function mechanism seems to be evident. However, at this stage it is still unclear whether this gain-of-function is driven by 'RNA toxicity' or 'DPR toxicity', or even a combination of both. Whereas a definite answer can only be generated in patient material (e.g. post mortem tissue), extensive in vivo disease models have been generated to disentangle this Gordian knot. Whereas several in vivo models have demonstrated the toxic potential of DPRs, in vivo models supporting RNA toxicity are currently lacking.
Therefore, by generating a new zebrafish model we aimed to assess whether repeat RNA can be toxic independent of DPRs, which would be indicative of RNA toxicity as a potential mechanism. Second, we aimed to identify modifiers of this RNA toxicity in order to unravel the mechanism of RNA toxicity.
We generated a transient zebrafish model by injecting repeat RNA into fertilized oocytes. At 30 hours post fertilization, microscopic analysis an axonopathy of spinal motor neurons upon injection of both sense and antisense repeat RNA. Remarkably, no DPRs were detected using both dot blot and immunoassay approaches. As such, this indicates that the presence of repeat RNA in the absence of DPRs is sufficient to cause neuronal toxicity and hence implicates RNA toxicity in the mechanism of C9orf72 ALS. Nevertheless, expression of individual DPRs through codon-optimized constructs revealed GR and PR to induce an axonopathy as well, hence confirming their toxic potential suggested in other in vivo models.
RNA toxicity is believed to be mediated by the repeat RNA compromising the function of several RBPs. Therefore we overexpressed ten RBPs, known to bind repeat RNA, in our zebrafish model. Interestingly five of them (Purα, hnRNPK, hnRNPA3, ALYREF and SRSF1) alleviated the RNA toxicity, indicating that their dysfunction might contribute to RNA toxicity pathogenesis.
Next we focused on Purα to assess how and if this protein is compromised in C9ORF72 ALS. We found the alleviating effect of Purα to be mediated by an induction of p62, mainly via its PUR2 domain, implicating an unexpected involvement of autophagy in RNA toxicity. In line herewith, Purα was found to reverse the increased LC3 levels in C9ORF72 patient derived fibroblasts. Moreover, Purα protein levels were decreased in C9ORF72 fibroblasts as well as in the RNA toxicity zebrafish model, suggesting it to indeed be compromised in C9ORF72 ALS.
Altogether we generated the first in vivo model demonstrating the toxic potential of C9ORF72 repeat RNA independent of DPR generation, thereby supporting RNA toxicity as a potential pathogenic mechanism of C9ORF72 ALS. Additionally, we identified several repeat RNA binding proteins to mitigate the RNA toxicity upon overexpression, suggesting their dysfunction to contribute to RNA toxicity pathogenesis. The dysfunction of one of these proteins, Purα, suggests RNA toxicity to induce disturbed autophagy.
Future research regarding RNA toxicity will need to be twofold. On the one hand, the true involvement of RNA toxicity in C9ORF72 ALS pathogenesis needs to be proven in humans. On the other hand, the mechanism of RNA toxicity needs to be unraveled further by assessing all RNA binding proteins and their downstream targets.status: Publishe
Human Neuromuscular Junction on a Chip: Impact of Amniotic Fluid Stem Cell Extracellular Vesicles on Muscle Atrophy and NMJ Integrity
Full text linkNeuromuscular junctions (NMJs) are specialized synapses, crucial for the communication between spinal motor neurons (MNs) and skeletal muscle. NMJs become vulnerable in degenerative diseases, such as muscle atrophy, where the crosstalk between the different cell populations fails, and the regenerative ability of the entire tissue is hampered. How skeletal muscle sends retrograde signals to MNs through NMJs represents an intriguing field of research, and the role of oxidative stress and its sources remain poorly understood. Recent works demonstrate the myofiber regeneration potential of stem cells, including amniotic fluid stem cells (AFSC), and secreted extracellular vesicles (EVs) as cell-free therapy. To study NMJ perturbations during muscle atrophy, we generated an MN/myotube co-culture system through XonaTM microfluidic devices, and muscle atrophy was induced in vitro by Dexamethasone (Dexa). After atrophy induction, we treated muscle and MN compartments with AFSC-derived EVs (AFSC-EVs) to investigate their regenerative and anti-oxidative potential in counteracting NMJ alterations. We found that the presence of EVs reduced morphological and functional in vitro defects induced by Dexa. Interestingly, oxidative stress, occurring in atrophic myotubes and thus involving neurites as well, was prevented by EV treatment. Here, we provided and validated a fluidically isolated system represented by microfluidic devices for studying human MN and myotube interactions in healthy and Dexa-induced atrophic conditions—allowing the isolation of subcellular compartments for region-specific analyses—and demonstrated the efficacy of AFSC-EVs in counteracting NMJ perturbations
- …
