1,721,023 research outputs found
ELAV proteins along evolution : back to the nucleus?
No full textThe complex interplay of post-transcriptional regulatory mechanisms mediated by RNA-binding proteins (RBP) at different steps of RNA metabolism is pivotal for the development of the nervous system and the maintenance of adult brain activities. In this review, we will focus on the highly conserved ELAV gene family encoding for neuronal-specific RBPs which are necessary for proper neuronal differentiation and important for synaptic plasticity process. In the evolution from Drosophila to man, ELAV proteins seem to have changed their biological functions in relation to their different subcellular localization. While in Drosophila, they are localized in the nuclear compartment of neuronal cells and regulate splicing and polyadenylation, in mammals, the neuronal ELAV proteins are mainly present in the cytoplasm where they participate in regulating mRNA target stability, translation and transport into neurites. However, recent data indicate that the mammalian ELAV RBPs also have nuclear activities, similarly to their fly counterpart, being them able to continuously shuttle between the cytoplasm and the nucleus. Here, we will review and comment on all the biological functions associated with neuronal ELAV proteins along evolution and will show that the post-transcriptional regulatory network mediated by these RBPs in the brain is highly complex and only at an initial stage of being fully understood. This article is part of a Special Issue entitled 'RNA and splicing regulation in neurodegeneration'
Post-transcriptional regulation mediated by ELAV/Hu RNA-binding proteins in motor neuron-like NSC34 cells
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Identification of new ANG gene mutations in a large cohort of Italian patients with Amyotrophic Lateral Sclerosis
No full textAngiogenin (ANG) gene, coding for an angiogenic factor up-regulated by hypoxia and expressed in ventral horn motor neurons, is a novel candidate for the pathogenesis of amyotrophic lateral sclerosis (ALS). ALS is a fatal neurodegenerative disease characterized by the selective loss of cortical and spinal motor neurons. Missense mutations in ANG gene have been identified in two ALS populations from Northern Europe and North America, both in familial (FALS) and sporadic (SALS) patients, but they do not seem to be frequent in the Italian population. We performed a mutational screening in a large cohort of 737 Italian ALS patients, including 605 SALS and 132 FALS cases. We identified seven different mutations, five of which are novel, in nine patients (six SALS and three FALS), but not in 515 healthy controls. Three mutations are located in the signal peptide region, three in the coding sequence, and one in the 3′ untranslated region. In our ALS population, the observed mutational frequency of ANG gene accounts for about 1.2%, with an overrepresentation of FALS (2.3%) compared to SALS (1%) cases. We also found the previously described I46V substitution in six patients and four controls, suggesting that this mutation may represent a benign variant, at least in the Italian population. Our results provide further evidence of a tight link between angiogenesis and ALS pathogenesis and suggest that mutations in ANG gene are associated with an increased risk to develop ALS
Human in vitro models of TDP-43 proteinopathy for drug screening approaches
No full textAggregates of phosphorylated TDP-43 protein in the cytoplasm of neurons are an ALS neuropathological hallmark. Response to stress and formation of stress granules (SGs) have been proposed as initiators of TDP-43 pathological aggregation. We previously showed that chronic oxidative stress by arsenite (ARS) induces the formation of SGs and phospho-TDP-43 aggregates in primary fibroblasts and iPSC-motor neurons from ALS patients.
Aim of our study was to generate a robust and reproducible in vitro model of TDP-43 pathology to be used for drug screening. We induced a chronic oxidative insult in human neuroblastoma SK-N-BE cells by exposure to low doses of ARS for 9-24 hours. Our data showed TDP-43 mislocalization from the nucleus to the cytoplasm in both a dose- and time-dependent manner and increase of P62. We also observed a defective splicing activity of TDP-43 towards its target genes UNC13A and POLDIP3 a readout of TDP-43 nuclear loss-of-function, upon chronic ARS treatment. We tested candidate drugs involved in promoting autophagy, namely rapamycin, lithium carbonate and metformin in our in vitro model of TDP-43 proteinopathy. Only rapamycin was able to rescue ARS-induced loss of TDP-43 splicing activity on its target genes and to reduce P62 accumulation.
We then tested rapamycin in C9ORF72 patient-derived fibroblasts and iPSC-motor neurons, where its efficacy in rescuing ARS-induced loss of TDP-43 splicing activity was confirmed. Rapamycin also significantly reduced ARS-induced phospho-TDP-43 aggregates and SGs formation.
In conclusion, we have set up human cell models of TDP-43 pathology in which rapamycin was proven to be beneficial in rescuing chronic oxidative stress-induced alterations in TDP-43 splicing activity and cytoplasmic mislocalization by modulating autophagy. Human SK-N-BE and ALS patient-derived cells chronically treated with ARS can therefore be exploited as valuable in vitro platforms for future drug screening approaches
Rapamycin reverts TDP-43 splicing defects and mislocalization in human in vitro models of TDP-43 proteinopathy
No full textAmyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the presence of aggregates of phosphorylated TDP-43 protein in the cytoplasm of affected neurons. The hypothesized pathomechanism is the loss of TDP-43 nuclear function and the concomitant toxic gain of function of the aggregates. Response to stress and formation of stress granules (SG) have been proposed as initiators of TDP-43 pathological aggregation. We previously showed that mild and chronic oxidative stress by arsenite (ARS) induces formation of both SG and phospho-TDP-43 aggregates in primary fibroblasts and iPSC-motor neurons from ALS patients in association to the accumulation of the autophagy receptor P62. Phospho-TDP-43 aggregates resemble those seen in ALS autoptic brains and are more abundant in C9ORF72 than in TARDBP patients’ cells.
Aim of our study was to generate a robust and reproducible in vitro model of TDP-43 pathology to be used for drug screening. We induced a chronic oxidative insult in human neuroblastoma SK-N-BE cells by exposure to low doses of ARS for 9-24 hours. Our data showed TDP-43 mislocalization from the nucleus to the cytoplasm in a dose- and time-dependent manner and increase of the autophagy receptor P62. We also observed a defective splicing activity of TDP-43 towards its target genes UNC13A and POLDIP3, a readout of TDP-43 nuclear loss-of-function, upon chronic ARS treatment. Since autophagy impairment favors TDP-43 pathological aggregation, we first tested the autophagy enhancer rapamycin in our in vitro model of TDP-43 proteinopathy. Rapamycin was capable of rescuing ARS-induced loss of TDP-43 splicing activity on its target genes and of reducing TDP-43 cytoplasmic mislocalization and P62 accumulation. We then tested rapamycin in C9ORF72 patient-derived fibroblasts and iPSC-motor neurons, where its efficacy in rescuing ARS-induced loss of TDP-43 splicing activity was confirmed. Rapamycin also significantly reduced ARS-induced phospho-TDP-43 aggregates and SG formation.
In conclusion, we have set up human cell models of TDP-43 pathology in which rapamycin proved to be beneficial in rescuing chronic oxidative stress-induced alterations in TDP-43 splicing activity and cytoplasmic mislocalization by modulating autophagy. Human SK-N-BE and ALS patient-derived cells chronically treated with ARS can therefore be exploited as valuable in vitro platforms for future drug screening approaches
Rapamycin reverts TDP-43 splicing defects and oxidative stress-induced alterations in a human in vitro model of TDP-43 proteinopathy
No full textAggregates of phosphorylated and ubiquitinated TDP-43 protein in the cytoplasm of neurons are an ALS neuropathological hallmark. Response to stress and formation of stress granules (SG) have been proposed as possible initiators of TDP-43 pathological aggregation. We recently showed that chronic oxidative stress by arsenite induces SG formation in fibroblasts and iPSC-motor neurons from TARDBP and C9orf72 patients. This insult also leads to the formation of phospho-TDP-43 aggregates, which are more abundant in C9orf72 cells and resemble those seen in ALS autoptic brains.
Aim of our study was to generate a cell model of TDP-43 pathology for screening drugs able to prevent or reduce TDP-43 pathological inclusions. Given the high variability in the response to stress observed in ALS patients’ cells, we reproduced a chronic oxidative insult in human neuroblastoma SK-N-BE cells by exposure to low doses of arsenite for a time frame ranging from 9 to 24 hours. Our data showed TDP-43 mislocalization from the nucleus to the cytoplasm in a dose- and time-dependent manner and a block in the autophagic flux. Of interest, in this condition we also observed a defective splicing activity of TDP-43 towards selected RNA targets, including UNC13A, STMN2 and POLDIP3. Chronic arsenite treatment is therefore able to reproduce both TDP-43 nuclear loss-of-function and its cytoplasmic mislocalization and aggregation, the two neuropathological hallmarks of TDP-43 proteinopathy. Since autophagy impairment favors TDP-43 pathological aggregation, we tested two autophagy enhancers, Rapamycin and Lithium carbonate. We found that Rapamycin, but not Lithium, was capable of rescuing arsenite-induced loss of TDP-43 splicing activity on RNA targets, of reducing insoluble TDP-43 content and of re-establishing the autophagic flux. We already confirmed the efficacy of Rapamycin on TDP-43 splicing activity in C9orf72 patient-derived fibroblasts exposed to chronic oxidative insult and further studies are now in progress to validate findings also in C9orf72 iPSC-motor neurons.
In conclusion, we have set up an experimental in vitro model of TDP-43 pathology in which Rapamycin proved to be beneficial, thus supporting the rationale for targeting autophagy in clinical trials. Moreover, this in vitro model can be exploited as a valuable platform for future drug screening approaches
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