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Caratterizzazione dei meccanismi molecolari associati alla patogenesi della Mucopolisaccaridosi di tipo I in un nuovo modello di Drosophila melanogaster
No full textLa mucopolisaccaridosi di tipo I (MPS I) è una malattia autosomica recessiva, appartenente al gruppo delle malattie metaboliche pediatriche. È causata da mutazioni nel gene codificante per l’enzima lisosomiale a-L-iduronidasi (IDUA) che degrada i glicosaminoglicani (GAG) eparan- e dermatan-solfato. Di conseguenza,questi si accumulano non degradati in diversi tessuti e organi, causandone un progressivo malfunzionamento.
MPS I presenta uno spettro di fenotipi, dalle forme attenuate, sindrome di Scheie e di Hurler-Scheie, a quella severa, la sindrome di Hurler.
Le manifestazioni cliniche della malattia sono principalmente rappresentate da facies caratteristica, organomegalia, valvulopatie, alterazioni osteo-articolari, infezioni respiratorie, e, nelle forme severe, da un progressivo coinvolgimento neurologico.
Sia la terapia enzimatica sostitutiva (ERT) che il trapianto di cellule staminali ematopoietiche (HSCT) sono oggi disponibili. ERT consiste nell’infusione settimanale dell’enzima ricombinante ed è parzialmente efficace nel trattare molti organi periferici, mentre è inefficace per il trattamento del sistema nervoso centrale (SNC) e per quello di alcuni distretti periferici, come ossa e valvole cardiache. Invece, l’HSCT è efficace nel trattamento del SNC, rallentando la progressione della malattia. Tuttavia, deve essere effettuato molto precocemente e non è in grado di revertere eventuali segni clinici instauratisi nelle fasi precedenti il trapianto.
Sebbene clinicamente ben caratterizzata, la malattia rimane ancora poco conosciuta dal punto di vista patogenetico e i meccanismi molecolari coinvolti non sono ancora sufficientemente chiari.
L’identificazione di pathway alterati coinvolti nella patogenesi, potrebbe potenzialmente fornire anche nuovi target terapeutici.
A tale scopo, in questo progetto è stato sviluppato un modello basato su Drosophila melanogaster, il moscerino della frutta.
Drososphila offre diversi vantaggi come animale modello, dato il suo breve ciclo vitale, che permette di effettuare studi rapidi sullo sviluppo, condotti su un numero elevato di animali, così come rapidi screening farmacologici. Drosophila è semplice da maneggiare, con costi di mantenimento contenuti. La disponibilità di linee transgeniche fluorescenti permette di condurre semplici e accurati studi in vivo.
Il modello è stato sviluppato utilizzando l’approccio dell’RNA interference (RNAi).
La riduzione ubiquitaria dell’omologo del gene umano Idua in Drosophila (D-idua) porta ad una diminuita attività enzimatica nel terzo stadio larvale, e a una completa letalità allo stadio di pupa. La selettiva diminuzione di D-idua in neuroni e glia causa una lieve, ma progressiva, disfunzione motoria e, allo stesso tempo, un aumento dell’aspettativa di vita. Il modello di Drosophila mostra alcune caratteristiche simili a quelle osservate in vitro nei fibroblasti umani e nel topo, quali l’aumentato numero e dimensione dei lisosomi in cervello e tessuto muscolare, e una riduzione della percentuale di lisosomi acidificati. Sono state osservate disfunzioni autofagiche e alterazioni di alcuni pathway metabolici, entrambe migliorate in condizioni di deprivazione di nutrienti. Sono state anche osservate alterazioni della rete mitocondriale e un alterato stato ossidativo dei mitocondri. Infine, l’aumento del volume cerebrale e la morfologia alterata delle terminazioni degli assoni motori riflettono alcune alterazioni strutturali del sistema nervoso. Nel complesso il modello sembra mimare alcuni aspetti associati alla patologia umana, mostra forti alterazioni in alcuni pathways ancora poco caratterizzati e un grande potenziale per approfondire i meccanismi coinvolti nella patogenesi della malattia. A partire dalle alterazioni osservate, il modello di Drosophila offre la possibilità di svolgere futuri screening farmacologici indirizzati a questi pathways alterati.Mucopolysaccharidosis type I (MPSI) is an autosomal recessive disease, belonging to the group of the inborn errors of metabolism. It is due to mutations in the gene encoding for the lysosomal enzyme α-L-iduronidase (IDUA), leading to a deficit of the enzymatic activity. IDUA degrades the glycosaminoglycansheparan- and dermatan-sulfate, which accumulate undegraded in different tissues and organs, leading to a progressive multi-organ impairment.
The syndrome presents a spectrum of phenotypes, from the attenuated forms, Scheie and Hurler-Scheie syndromes, to the severe form, Hurler syndrome.
Clinical manifestations of the disease are facial dimorphisms, organomegaly, valvuolpathies, osteo-articular abnormalities, respiratory infections and, in the severe form, a progressive neurological impairment.
Enzyme replacement therapy (ERT) and hematopoietic stem cells transplantation (HSCT) are available for the treatment. ERT, consisting in weekly infusions of the recombinant enzyme, although quite efficient in treating most peripheral tissues, is inefficient in treating both the CNS disease and some difficult districts, as bones and heart valves. Instead, HSCT is efficient in treating the CNS compartment slowing down the progression of the disease. However, it is effective if carried out very early in life and unable to revert clinical signs established before transplantation.
Although clinically well characterized, the disease remains poorly understood from the pathogenic side, and the underlined molecular mechanisms are not enough clarified.
Understanding the pathological mechanisms underlying MPSI could help to identify altered pathways involved in the pathogenesis, possibly addressable as new therapeutic targets.
To this aim, in this project a Drosophila melanogaster model for MPSI was developed and characterized. Drosophila offers several advantages as an animal model, due to a short life cycle, which permits to perform rapid developmental studies conducted in a high number of flies, as well as rapid pharmacological screenings. In addition, it is easy to handle, and has relatively contained costs of maintenance. Furthermore, the availability of transgenic fluorescent lines allows to conduct simplified and accurate in vivo studies.
The model was developed using the RNA interference approach. The ubiquitous downregulation of the Drosophila Idua homologue led to a decreased enzyme activity in the third instar larvae and to a complete lethality at pupal stage. The selective downregulation of D-idua in neurons and glial cells led to a mild, progressive locomotor impairment and, on the other hand, to an increased lifespan.
The D-idua model showed some cellular and molecular features similar to those observed in other MPSI models, as an increased number and size of lysosomes, both in the brain and in the muscle tissue, together with a decreased percentage of acidified lysosomes. In addition, autophagy and metabolic pathways impairment were observed, both ameliorated in starvation conditions. Also, alterations of the mitochondrial network, together with impaired mitochondria oxidation status were recorded. Lastly, increased brain volumes and abnormal morphology of motor axon terminations represent signs of nervous system structural alterations.
Overall, the MPSI Drosophila model appears to mimic some aspects of the human MPSI pathology, and shows strong alterations in some pathways, still poorly characterized in the disease. The model presents great potential for deepening the mechanisms involved in the pathogenesis of the disease. Starting from the involvement of different metabolic pathways, which in this project were shown to be drastically affected, the MPSI fly model offers the possibility to conduct in the future pharmacological screenings specifically targeted to these altered pathways
Naringenin Ameliorates Drosophila ReepA Hereditary Spastic Paraplegia-Linked Phenotypes
Full text linkDefects in the endoplasmic reticulum (ER) membrane shaping and interaction with other organelles seem to be a crucial mechanism underlying Hereditary Spastic Paraplegia (HSP) neurodegeneration. REEP1, a transmembrane protein belonging to TB2/HVA22 family, is implicated in SPG31, an autosomal dominant form of HSP, and its interaction with Atlastin/SPG3A and Spastin/SPG4, the other two major HSP linked proteins, has been demonstrated to play a crucial role in modifying ER architecture. In addition, the Drosophila ortholog of REEP1, named ReepA, has been found to regulate the response to ER neuronal stress. Herein we investigated the role of ReepA in ER morphology and stress response. ReepA is upregulated under stress conditions and aging. Our data show that ReepA triggers a selective activation of Ire1 and Atf6 branches of Unfolded Protein Response (UPR) and modifies ER morphology. Drosophila lacking ReepA showed Atf6 and Ire1 activation, expansion of ER sheet-like structures, locomotor dysfunction and shortened lifespan. Furthermore, we found that naringenin, a flavonoid that possesses strong antioxidant and neuroprotective activity, can rescue the cellular phenotypes, the lifespan and locomotor disability associated with ReepA loss of function. Our data highlight the importance of ER homeostasis in nervous system functionality and HSP neurodegenerative mechanisms, opening new opportunities for HSP treatment
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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