1,721,020 research outputs found
Inherited Retinal Dystrophies: The role of gene expression regulators
No full textInherited Retinal Dystrophies (IRDs) are a clinically and genetically heterogeneous group of rare disorders characterized by a significant impairment in retinal function and vision. More than 150 genes have been associated with retinal dystrophies and the genetic overlap among different IRDs renders diagnosis and prognosis challenging. In this In Focus article, we give a summary on the pathogenic role of gene expression regulators in IRDs. Emphasis is given on key transcription factors that participate to regulatory gene networks controlling photoreceptor specification and maintenance, and their possible relevance as therapeutic targets. The increasing knowledge on the composition and function of these transcriptional regulatory networks indicates that intervening on transcription factors may be instrumental for a more effective treatment of some forms of IRDs, although the development of appropriate molecular tools to target them remains a formidable challenge
Mir-204 Modulates Optic Cup Patterning During Medaka Fish Embryonic Eye Development
No full textPurpose: : Progressive specification of the eye structures, during vertebrate embryonic development, requires precise regulation of morphogenetic events, which are coordinated by networks of transcription factors and cell signalling pathways. Regulation of gene activity by microRNAs (miRNAs) is critical in multiple aspects of vertebrate embryonic development. Here, we focus on the in vivo role of miR-204, which is highly expressed in the developing retinal pigment epithelium, lens and retina.
Methods: : miR-204 function, during Oryzias latipes (medaka fish) eye development, was assessed by injection of antisense "multiblocking" morpholino oligonucleotides, which specifically prevented biogenesis and activity of this microRNA. Heteroduplex miR-204 oligonucleotides injections were performed to increase miR-204 activity. Analysis of eye phenotypes in injected embryos included morphological inspection and molecular analyses by RNA in situ hybridization and immunohistochemistry.
Results: : The knockdown of miR-204 in medaka fish led to a specific eye phenotype, characterised by microphthalmia, coloboma and aberrant lens formation. In addition, disruption of miR-204 activity determined significant defects in ventral retina cell differentiation processes. We demonstrated that the miR-204-morphant eye phenotype is in part due to increased cell death rather than decreased proliferation. We showed that miR-204 acts by directly repressing positive regulators of the PAX6 gene. Finally, miR-204 over-expression led to changes in the expression levels of retinal and lens cell specific markers, which were mostly complementary to those observed following miR-204 inactivation.
Conclusions: : Taken together, these results not only demonstrate that a single miRNA can regulate the folding of the optic vesicle to form the optic cup and the formation of a mature and functional eye, but also establish the existence of a precise network between miR-204 and Pax6 in mediating retina and lens development
Inducible gene expression systems and plant biotechnology
No full textPlant biotechnology relies heavily on the genetic manipulation of crops. Almost invariantly, the gene of interest is expressed in a constitutive fashion, although this may not be strictly necessary for several applications. Currently, there are several regulatable expression systems for the temporal, spatial and quantitative control of transgene activity. These molecular switches are based on components derived from different organisms, which range from viruses to higher eukaryotes. Many inducible systems have been designed for fundamental and applied research and since their initial development, they have become increasingly popular in plant molecular biology. This review covers a broad number of inducible expression systems examining their properties and relevance for plant biotechnology in its various guises, from molecular breeding to pharmaceutical and industrial applications. For each system, we examine some advantages and limitations, also in relation to the strategy on which they rely. Besides being necessary to control useful genes that may negatively affect crop yield and quality, we discuss that inducible systems can be also used to increase public acceptance of GMOs, reducing some of the most common concerns. Finally, we suggest some directions and future developments for their further diffusion in agriculture and biotechnology
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
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