1,720,973 research outputs found
DENDRITIC TRAFFICKING OF BRAIN-DERIVED NEUROTROPHIC FACTOR mRNA AND NEURONAL ATROPHY
Full text linkTrafficking and local translation in neuronal dendrites of selected transcripts, like brain-derived neurotrophic factor (BDNF) mRNA, is a mechanism underlying synaptic plasticity, spine remodeling and neuronal development. It was previously demonstrated that BDNF mRNA is targeted to dendrites in an activity dependent manner. BDNF has a complex gene structure that in rodents, giving rise to eleven different variants in the 5’ untranslated region (5’ UTRs) which are alternatively spliced to a common coding region (CDS) having either a short or long 3’UTR region due to the presence of two different polyadenylation sites. BDNF variants have a different spatial distribution in neurons, allowing a fine regulation of BDNF expression. It was previously shown that BDNF CDS encodes a constitutive dendritic targeting signal recognized by the RNA binding protein (RBP) Translin. Moreover different exons could act as signals for soma retention or permissive for dendritic targeting of BDNF mRNA. The two 3'UTRs regulates activity dependent targeting of BDNF transcripts however, their mechanism of action is unknown.
In this study, we investigated the mechanisms underlying the BDNF mRNA trafficking under normal conditions and in a disease characterized by neuronal atrophy: Rett syndrome. In particular we analyzed if the different 5'UTRs sequences alone were able to modify the sorting of reporter Green Fluorescent Protein (GFP) mRNA expressed in transfected hippocampal rat neurons in vitro. We found that only three variants promote a constitutive dendritic targeting, while other variants display a similar distribution to those of GFP reporter mRNA alone, both in basal or stimulated conditions. Then, we focused our attention on the characterization of the interaction between endogenous BDNF mRNA and two different subsets of RBP families required for BDNF 3'UTR activity dependent targeting: the cytoplasmic polyadenylation element binding proteins (CPEBs), the Embryonic Lethal Abnormal Vision-like proteins (ELAVLs) and the Fragile-X Mental Retardation Protein (FMRP). Possible interactions between RBPs protein family and BDNF mRNA were verified by Cross Linking Immunoprecipitation (CL-IP) assays on brain lysates. Moreover, we assessed the grade of colocalization in vitro by fluorescent in situ hybridization for endogenous BDNF mRNA coupled to immunofluorescence for the different RBPs families. This study confirms the association of these proteins to BDNF transcripts, highlighting an heterogeneous colocalization profile.
Since mutations in RBP genes are known to be involved in neurodevelopment disorders, we investigated if a dysregulation in ribonucleoparticles (RNP) was involved in the pathogenic mechanism of Rett syndrome (RTT). RTT is an X-linked neurodevelopmental disorder affecting 1:10.000 females. We used a mouse model for this syndrome to analyze in vitro the distribution of three classes of RNP in neurons: transporting granules, stress granules and processing bodies. We selected Staufen-1, Tia-1 and DCP1a as specific markers to describe RNP distribution, dimension and labeling intensity. Moreover, we characterized the distribution of BDNF mRNA in RTT neurons to assess if a lack of trophic support occurs in this pathology during stressful condition or during neuronal activity.
We found that alterations in the composition of the granules are present in this model, suggesting that an altered RNP homeostasis could be involved in the pathological mechanisms of RTT.
Finally, we tried to rescue neuronal atrophy in vitro by treating cultured neurons with Mirtazapine, an antidepressant that is known to increase BDNF levels in rats and that was recently demonstrated to rescue deficits in the brain of RTT mouse. Using a well characterized in vitro staging for the study of neuronal atrophy we demonstrated that morphological deficits of RTT neurons were rescued after treatment with Mirtazapine
Biologics and cardiac disease: challenges and opportunities
Full text linkBiologics are revolutionizing the treatment of chronic diseases, such as cancer and monogenic disorders, by overcoming the limits of classic therapeutic approaches using small molecules. However, the clinical use of biologics is limited for cardiovascular diseases (CVDs) , which are the primary cause of morbidity and mortality worldwide. Here, we review the state-of-the-art use of biologics for cardiac disorders and provide a framework for understanding why they still struggle to enter the field. Some limitations are common and intrinsic to all biological drugs, whereas others depend on the complexity of cardiac disease. In our opinion, delineating these struggles will be valuable in developing and accelerating the approval of a new generation of biologics for CVDs
Endothelial cell-cardiomyocyte crosstalk in heart development and disease
Full text linkThe crosstalk between endothelial cells and cardiomyocytes has emerged as a requisite for normal cardiac development, but also a key pathogenic player during the onset and progression of cardiac disease. Endothelial cells and cardiomyocytes are in close proximity and communicate through the secretion of paracrine signals, as well as through direct cell-to-cell contact. Here, we provide an overview of the endothelial cell-cardiomyocyte interactions controlling heart development and the main processes affecting the heart in normal and pathological conditions, including ischaemia, remodelling and metabolic dysfunction. We also discuss the possible role of these interactions in cardiac regeneration and encourage the further improvement of in vitro models able to reproduce the complex environment of the cardiac tissue, in order to better define the mechanisms by which endothelial cells and cardiomyocytes interact with a final aim of developing novel therapeutic opportunities
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Combined cisplatin and aurora inhibitor treatment increase neuroblastoma cell death but surviving cells overproduce BDNF
Full text linkDrug-resistance to chemotherapics in aggressive neuroblastoma (NB) is characterized by enhanced cell survival mediated by TrkB and its ligand, brain-derived neurotrophic factor (BDNF); thus reduction in BDNF levels represent a promising strategy to overcome drug-resistance, but how chemotherapics regulate BDNF is unknown. Here, cisplatin treatment in SK-N-BE neuroblastoma upregulated multiple BDNF transcripts, except exons 5 and 8 variants. Cisplatin increased BDNF mRNA and protein, and enhanced translation of a firefly reporter gene flanked by BDNF 5′UTR exons 1, 2c, 4 or 6 and 3′UTR-long. To block BDNF translation we focused on aurora kinases inhibitors which are proposed as new chemotherapeutics. NB cell survival after 24 h treatment was 43% with cisplatin, and 22% by cisplatin+aurora kinase inhibitor PHA-680632, while the aurora kinases inhibitor alone was less effective; however the combined treatment induced a paradoxical increase of BDNF in surviving cells with strong translational activation of exon6-3′UTR-long transcript, while translation of BDNF transcripts 1, 2C and 4 was suppressed. In conclusion, combined cisplatin and aurora kinase inhibitor treatment increases cell death, but induces BDNF overproduction in surviving cells through an aurora kinase-independent mechanism
- …
