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Evidence for the Role of the WW Domain-Containing Oxidoreductase in Lipoprotein Metabolism: Potential Implications for HDL Biogenesis
No full textNovel genetic and molecular regulation of HDL metabolism
No full textCoronary artery disease (CAD) is the leading cause of mortality and morbidity worldwide. Low levels of high-density lipoprotein cholesterol (HDL-C) constitute a major independent risk factor for CAD, influenced by a combination of genetic and environmental factors. In this thesis, we aimed to advance our understanding of the genetic regulation of HDL-C, through the identification and characterization of novel candidate genes, and to delineate the molecular mechanisms underlying HDL biogenesis, in the hopes of better elucidating the complexities of HDL metabolism. First, we examined whether variation at the PCSK5 gene locus influences HDL-C levels. Through familial segregation analyses and two-stage genetic association studies in unrelated subjects of French Canadian descent and low HDL-C Finnish families (ntotal=883), we reported a region-wide significance of PCSK5 SNPs with HDL-C, suggesting that genetic variability at the PCSK5 locus regulates HDL-C levels, possibly through the inactivation of endothelial lipase. Second, to search for rare-low frequency variants responsible for low HDL-C, we used whole exome sequencing in a multigenerational French Canadian family (n=75) with HDL-C<5th age-sex specific percentile. Through this approach, we identified a complex combination of two non-synonymous variants, in the ATP-binding cassette transporter (ABCA1) and the lipoprotein lipase genes, predicted to be damaging and causing low HDL-C. These results emphasize the need for exome sequencing of complex lipid traits in unexplained familial cases. Third, we sought to characterize a novel genetic determinant involved in HDL-C regulation. Recent studies from our group identified the WW domain-containing oxidoreductase (WWOX) gene locus to be associated with low serum HDL-C levels in 9,798 subjects. In this study, we examined the role of WWOX in lipoprotein and HDL metabolism using a combination of in vivo functional studies, by means of total Wwox knock-out and Wwox liver-specific mouse models, gene microarray and next generation resequencing analyses in HDL-deficient French Canadian families. We demonstrated that the effects of WWOX on lipoprotein metabolism involve multiple mechanisms, including cholesterol homeostasis, apoA-I and ABCA1-mediated pathways and fatty acid/triglyceride metabolism. Fourth, with novel insight into genetic regulations of HDL metabolism, we focused on elucidating the mechanistic basis of nascent HDL formation. Specifically, we investigated the lipidation of ApoA-I and its interaction with an ABCA1/phosphatidylcholine(PC)-rich microdomain, the high-capacity binding site (HCBS). Using sucrose gradient fractionation, we also demonstrated that the ABCA1/ HCBS partitions to nonraft domains, thus playing a pivotal role in the selective desorption of PC molecules by apoA-I, creating an optimal environment for nascent HDL formation and cholesterol release.In summary, this work has collectively advanced our understanding of the molecular and genetic basis of HDL metabolism. It has brought to light novel genes governing plasma HDL-C levels in humans, highlighting the need to use multiple integrative genetic approaches to identify causal common and rare variants conferring susceptibility to low HDL-C. These findings have also helped elucidate the mechanistic basis of the nascent HDL genesis pathway. Together, this thesis has combined genetic and biochemical strategies to provide a more comprehensive understanding of the complexities of the HDL metabolism and cellular cholesterol transport, which may lead to the characterization of novel therapeutic targets for CAD.La maladie coronarienne athérosclérotique (MCAS) est la principale cause de mortalité et de morbidité à l'échelle mondiale. Un niveau bas des lipoprotéines de cholestérol de haute densité (HDL-C) représente un facteur de risque majeur pour la MCAS et est influencé par une combinaison des facteurs génétiques et environnementaux. Dans cette thèse, nous avons abordé la régulation génétique des HDL-C grâce à l'identification et la caractérisation de nouveaux gènes candidats, et de mécanismes moléculaires liés à la biogenèse des HDL, dans l'espoir de mieux élucider la complexité du métabolisme des HDL.En premier, nous avons examiné si la variation au niveau du locus du gène proprotéine convertase PCSK5 peut affecter les niveaux de HDL-C. Grâce aux analyses de ségrégation familiale et aux études d'association génétique dans une population canadienne-française et chez des familles finlandaises (nTotal=883) avec un niveau de HDL-C bas, nous avons constaté une large corrélation régionale entre les variations polymorphiques (SNPs) de PCSK5 et HDL-C. Ceci suggère que la variabilité génétique au niveau du locus PCSK5 réglemente le HDL-C, éventuellement par le biais de l'inactivation de la lipase endothéliale, une enzyme clé dans la modulation des niveaux plasmatiques de HDL-C. Deuxièmement, pour rechercher des variants de fréquence rare qui sont responsables d'un bas niveau de HDL-C, nous avons utilisé la technique du séquençage de l'exome dans une famille multi-générationnelle canadienne-française (n=75) avec un HDL-C<5e percentile spécifique (âge-sexe). Grâce à cette approche, nous avons identifié une combinaison complexe de deux variants non-synonymes dans le transporteur ABCA1 et dans le gène de la lipoprotéine lipase provoquant un taux faible de HDL-C. Ces résultats soulignent la nécessité du séquençage de l'exome des traits lipidiques complexes dans les cas familiaux inexpliqués. Troisièmement, nous avons caractérisé un nouveau gène impliqué dans la régulation du HDL-C. Nous avons examiné le rôle de WWOX dans le métabolisme du HDL en utilisant des études fonctionnelles in vivo avec des souris Wwox total knock-out (KO) et des souris Wwox KO spécifiques au foie, une technologie des puces à ADN et du reséquençage dans des familles canadiennes-françaises déficientes en HDL. Nous avons démontré que l'effet de WWOX sur le métabolisme des lipoprotéines implique plusieurs mécanismes, y compris l'homéostasie du cholestérol, les voies de régulation à travers l'ApoA-I et l'ABCA1 et le métabolisme d'acides gras/triglycérides. Quatrièmement, nous voulions élucider le mécanisme de formation du HDL naissant. Plus précisément, nous avons étudié la lipidation de l'ApoA-I et son interaction avec des sites constitués de microdomaines ABCA1/phosphatidylcholine (PtdC) que nous avons appelés « site de liaison de grande capacité (HCBS) ». En utilisant un gradient de densité de sucrose, nous avons observé que l'ABCA1 et le HCBS sont localisés dans des domaines membranaires solubles aux détergents et que l'ApoA-I désorbe sélectivement la PtdC de ces domaines ainsi créant un environnement optimal pour la formation des molécules naissantes de HDL et la libération de cholestérol.Collectivement, ce travail a élargi notre compréhension des sciences moléculaires et génétiques du métabolisme du HDL. Il a mis en lumière de nouveaux gènes impliqués dans la régulation des niveaux de HDL-C, soulignant la nécessité d'utiliser plusieurs approches intégratives génétiques pour identifier les causes des variants communs et rares conférant une susceptibilité à un faible taux de HDL-C. Ces résultats ont également contribué à élucider le mécanisme de biogenèse du HDL naissant. Ainsi, cette thèse a combiné des stratégies génétiques et biochimiques pour fournir une meilleure compréhension de la complexité du métabolisme des HDL et du transport du cholestérol cellulaire, qui pourrait ainsi conduire à l'élaboration des nouvelles cibles thérapeutiques pour la MCAS
Deficiency of the WW Domain-Containing Oxidoreductase (WWOX) Impairs the HDL Biogenesis Pathway
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
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