Voltage-gated sodium ion channels play a vital role in neuron function, which becomes evident when variants in these genes disrupt their function. Mutations in SCN8A have only recently been linked to an epilepsy phenotype characterized by early-onset of seizures, delayed development, and intellectual disability. Using patient data from published papers (n = 75) as well as an online support group (n = 61), we were able to identify several patterns in the pathogenic mutations and compare them to a group of healthy individuals from the Exome Aggregation Consortium (ExAC) (n = 960). Most of the variants are missense, with one reported nonsense mutation in an individual with ataxia instead of epilepsy. The average age of onset from 85 individuals combined from the published papers and the online support group was 4.45 months. Notably, the ages of onset have a bimodal distribution instead of normal, with one peak within the first month of life and a second peak at 4 months of age. Pathogenic mutations are more likely to appear in the transmembrane regions of the protein encoded by SCN8A (Nav1.6) (Proportion Test: p-value = 9.1 x 10⁻⁵) while non-pathogenic variants were more likely to appear in the connecting loops of the protein (Proportion Test: p-value<2.2 x 10⁻¹⁶). This is most likely due to the transmembrane regions having a greater functional role than the loops. When we further separate the mutations into functional parts of the protein, we generally see that areas with more pathogenic mutations have fewer non-pathogenic variants, and vice versa. For example, the inactivation gate of the protein has more pathogenic variants (Exact Binomial Test: p-value = 3.52 x 10⁻⁶) while the N-terminus has more non-pathogenic variants (Exact Binomial Test: p-value = 0.0128). This suggests that areas with more pathogenic variants are less tolerable to variation while those with more non-pathogenic variants are more tolerable. Interestingly, there are some areas of the protein with very few pathogenic and non-pathogenic variants, such as the pore regions of the protein. This is likely due to the vital functional nature of the pore, and any variants in that region lead to lethality. Further analyses are needed to determine if there are correlations between categories of pathogenic mutations and the phenotypes of the patients.

This is the first of 2 review papers on genetics and genomics appearing as part of the series on “omics.” Genomics pertains to all components of an organism’s genes, whereas genetics involves analysis of a specific gene(s) in the context of heredity. The paper provides introductory comments, describes the basis of human genetic diversity, and addresses the phenotypic consequences of genetic variants. Rare variants with large effect sizes are responsible for single gene disorders, whereas complex polygenic diseases are typically due to multiple genetic variants, each exerting a modest effect size. To illustrate the clinical implications of genetic variants with large effect sizes, 3 common forms of hereditary cardiomyopathies are discussed as prototypic examples of single-gene disorders, including their genetics, clinical manifestations, pathogenesis, and treatment. The genetic basis of complex traits is discussed in a separate paper.

Les isoformes de Tau font parties d’une famille de protéines associées aux microtubules, principalement exprimées dans les neurones du système nerveux central. Ils favorisent l'assemblage de monomères tubuline en microtubules et leurs stabilités, jouant un rôle structurel clé dans les axones neuronaux. Dans la maladie d’Alzheimer et autres tauopathies, la protéine Tau agrège sous forme d’enchevêtrements fibrillaires impliqués dans les lésions intraneuronales et gliales. A l’heure actuelle, le processus d’agrégation présent au sein des tauopathies n’est pas complètement élucidé malgré un grand nombre d’études effectués in vitro. L’essentiel du travail présenté dans ma thèse est basé sur un modèle d’étude in vitro utilisant une protéine Tau recombinante présentant la mutation P301L. Ce mutant ainsi que d’autres fragments de Tau ont été utilisés pour mieux comprendre le mécanisme d’agrégation, comme par exemple le rôle des cystéines, ou de la région riche en proline. Nous avons montré par des mesures de diffusion de la lumière et fluorescence de la Thioflavine S qu’il existe un système d’agrégation indépendant des ponts disulfures intermoléculaires. Nous avons également étudié la capacité anti agrégative de plusieurs polyphénols naturels et endogènes. Notre attention s’est en particulier portée sur trois dérivés phénoliques obtenus à partir d'huile d'olive : l'hydroxytyrosol, l'oleuropéine, l'oleuropéine aglycone. Ce dernier a été trouvé plus actif que l’inhibiteur de référence de Tau, le bleu de méthylène. Des résultats similaires ont été obtenu avec des molécules issues de la dimérisation du DOPAL. L’activité inhibitrice de la fibrillisation de ces molécules peut même atteindre des valeurs submicromolaires. / Tau isoforms are part of the microtubule-associated proteins family, mainly expressed in neurons of the central nervous system. They promote the assembly of tubulin monomers into microtubules and their stabilities, playing a key structural role in neuronal axons. In Alzheimer's disease and other tauopathies, the tau protein aggregates as fibrillar tangles involved in intraneuronal and glial lesions. At present, the process of aggregation present in the tauopathies is not fully understood despite a large number of studies performed in vitro. Most of the work presented in my thesis is based on an in vitro model study using recombinant tau protein with the P301L mutation. This mutant and other fragments of Tau were used to better understand the mechanism of aggregation, such as the role of the cysteines or the proline-rich region. We have shown by measurements of light scattering and fluorescence of Thioflavin S there is a system of aggregation independent of intermolecular disulfide bonds. We also studied the ability of several anti-aggregative natural polyphenols and endogenous. Our attention was particularly focused on three phenolic derivatives obtained from olive oil: hydroxytyrosol, oleuropein, oleuropein aglycone. The latter was found more active than the reference inhibitor of Tau, methylene blue. Similar results were obtained with molecules from DOPAL dimerization. The inhibitory activity of fibrillization of these molecules can reach submicromolar values.

The aim of my study was to create a Drosophila line lacking the expression of all Sirtuin genes, check its developmental phenotype and characterise its response in stress conditions. The flies had bigger weight than controls, they had decreased fertility and fecundity and they developed more slowly. They showed a trend towards increased resistance to chill coma, but they did not show a significant difference in starvation or oxidative stress assay. Its effect on lifespan is being investigated.

by Yuen-Shan Chan. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1987. / Bibliography: leaves 142-150.

Thesis (M. Ph.)--Chinese University of Hong Kong. / Bibliography: 101-113 l.

��-catenin is a multi functional protein that is involved in cell-cell adhesion and cell signaling. In non-stimulated cells, ��-catenin is tightly down-regulated by GSK-3��-dependent phosphorylation at Ser and Thr residues, followed by rapid ubiquitination and proteasomal degradation. It is well established that mutations within the regulatory GSK-3�� region lead to stabilized ��-catenin and constitutive ��-catenin/TCF-dependent gene activation. Furthermore, it has been shown that amino acids adjacent to codon 33, namely 32 and 34 of ��-catenin, are hotspots for substitution mutations in carcinogen-induced animal tumors. Thus, a major hypothesis of this thesis was that substitution mutations at codon 32 of ��-catenin interfere with phosphorylation and ubiquitination of ��-catenin. Site-directed mutagenesis was used to create defined ��-catenin mutants, namely D32G, D32N, and D32Y. The signaling potential of various ��-catenin was analyzed in a gene reporter assay by co-transfection with a hTcf cDNA with a reporter plasmid containing a Tcf-dependent promoter (TOPFlash). There was a significant enhancement of the reporter gene activity with all ��-catenin mutants compared to WT ��-catenin after 48 hours of transfection. Protein analysis by Western blotting showed massive accumulation of mutant ��-catenin. Antibody specific for phosphorylated ��-catenin showed that the accumulated D32G and D32N ��-catenin proteins were strongly phosphorylated both in vivo and in vitro, whereas D32Y ��-catenin exhibited significantly attenuated phosphorylation in vivo. Further studies showed, however, that none of the mutants was sufficiently ubiquitinated. In addition, inhibition of the proteasome activity by ALLN was associated with accumulation of cytosolic ��-catenin, which was transcriptionally inactive. This suppression of ��-catenin transcriptional capacity was independent of ALLN-associated apoptosis in the transfected cells. Furthermore, exogenous ��-catenin mediated modest cell survival and rendered cells sensitive to apoptotic stimuli. Thus, although codon 32 of ��-catenin is not a direct target for phosphorylation, results from this thesis suggested that it affects the phosphorylation and ubiquitination of the adjacent Ser-33 residue of ��-catenin, which is a direct target of GSK-3��. In addition, these results showed for the first time that the phosphorylation step of ��-catenin is not enough to regulate transcriptional activity, and that ��-catenin still needs to be ubiquitinated for successful down-regulation. / Graduation date: 2003

Texte remanié de: Thèse de doctorat--Université catholique de Louvain, 2005. / Bibliogr. p. 508-543. Index.

Thèse doctorat : Approches Mathématiques et Informatiques du Vivant : Villeurbanne, INSA : 2006. / Titre provenant de l'écran-titre. Bibliogr. p. 147-167.

Proefschrift--Amsterdam.