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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Diversité génétique individuelle, différenciation morphologique et comportementale entres les sexes, patterns d'appariement et paramètres démographiques chez une espèce d'oiseau tropicale et monogame, la tourterelle à queue carrée, Zenaida Aurita / Individual genetic diversity, morphological and behavioral differentiation between sexes, patterns and demographic parameters in a tropical and monogamous bird species, the Zenaida dove, Zenaida aurita

Quinard, Aurélie 12 December 2013 (has links)
La recherche en écologie comportementale est affectée par un biais notoire en faveur des oiseaux des zones tempérées, en dépit de la plus grande diversité des espèces tropicales et des conditions naturelles radicalement éloignées qui rendent les connaissances sur les espèces tempérées peu pertinentes pour les espèces tropicales.Nous proposons de combler le manque d’informations concernant les oiseaux tropicaux via l’étude d’une espèce socialement monogame, se reproduisant et défendant un territoire toute l’année, la Tourterelle à queue carrée, Zenaida aurita. Pour commencer, nous avons cherché à déterminer le caractère sexuellement mono- ou dichromatique de la coloration du plumage et si celui-ci reflétait la qualité individuelle. Nous avons ensuite exploré les patterns d’appariements au sein des couples selon le degré d’hétérozygotie et la taille du corps. Afin d’établir la force des liens du couple, nous avons évalué le taux de divorce, les hypothèses pouvant expliquer les cas répertoriés, et les conséquences du changement de partenaire. Ceci a été suivi par la caractérisation des rôles des sexes au sein des couples selon diverses activités. Des analyses de capture-marquage-recapture ont permis d’estimer le taux de survie ainsi que l’influence du degré d’hétérozygotie et de la taille de l’aile sur la survie. La Tourterelle à queue carrée paraît suivre les spécificités comportementales, écologiques et démographiques caractérisant les espèces tropicales à monogamie pérenne / Research in avian behavioral ecology is affected by a known bias in favour of temperate species despite the greatest diversity of tropical species and the radically remote natural conditions which make knowledge of temperate species hardly relevant to tropical species.We propose to reduce the lack of information about tropical birds through the study of a socially monogamous species, reproducing and defending an all-purpose territory all year round, the Zenaida dove, Zenaida aurita. We used monitoring data from a population of ringed birds in Barbados for six years. First, we focused on plumage coloration both to ascertain their sexually mono- or dichromatic nature and whether plumage colour reflects individual quality. We then explored pairing patterns in relation to genome-wide heterozygosity and body size (tarsus length, wing chord). To determine the strength of pair bonding, we assessed divorce rate, evaluated which hypotheses could explain divorce cases and listed the consequences of mate loss and mate switching. It was followed by the characterization of sex roles within pairs during various activities (singing, nest building, juvenile care, territorial defence). Capture-mark-recapture analysis allowed us to estimate survival rate as well as influence of heterozygosity degree and wing chord on individual survival. Zenaida dove appears to conform to the behavioral, ecological and demographic features characterizing tropical species with perennial monogamy
72

Biologie de la conservation de la gorgone rouge de Méditerranée, Paramuricea clavata, dans le contexte actuel du changement climatique

Mokhtar-Jamai, Kenza 23 September 2011 (has links)
La gorgone rouge, Paramuricea clavata (Cnidaire, Octocoralliaire), est une espèce sessile, longévive à faible croissance dont les populations présentent une lente dynamique. Cette espèce est caractérisée par une phase larvaire pélagique qui représente l’unique phase de dispersion potentielle au cours du cycle de vie de cette espèce. P. clavata est une espèce clé des assemblages à coralligène de Méditerranée, qui subit les effets combinés des activités de plongée sous-marine et du changement climatique. Dans ce contexte, il était donc fondamental d’approfondir les connaissances sur les traits d’histoire de vie, la biologie et l’écologie de cette espèce. L’objectif de ce travail était d’étudier, à l’aide d’une approche génétique, les facteurs biologiques et écologiques clés qui devraient être importants pour la réponse de l’espèce aux changements environnementaux. Parmi ces facteurs, la dispersion larvaire joue un rôle fondamental dans la dynamique et la connectivité des populations marines. Dans le contexte actuel des fortes pressions anthropiques, la compréhension des degrés de connectivité entre les populations est primordiale pour évaluer le devenir des populations, face au changement climatique, et pour mettre en place des plans de conservation et des réseaux d’aires marines protégées. / The red gorgonian, Paramuricea clavata (Cnidaria, Octocorallia), is a sessile, long-lived and slow growing species which displays slow population dynamics. This species is characterized by a pelagic larval phase that represents the sole potential phase of dispersal during the life cycle of this species. P. clavata is a key species of coralligenous assemblages of the Mediterranean Sea which undergoes the combined effects of diving activities and climate change. In this context, extending the knowledge about life history traits, biology and ecology of the red gorgonian was of fundamental importance. Using a genetic approach, the goal of this work was to study some key biological and ecological factors which should be important for the response of this species to environmental changes. Among these factors, larval dispersal plays a major role in driving marine population dynamics and connectivity. In the current context of strong anthropic pressures, understanding the level of population connectivity is primordial to evaluate population outcome, facing climate change, and to develop conservation plans as well as to design marine reservenetworks.
73

Genome-wide screening of loss of heterozygosity in human midgut carcinoid tumors with fluorescent technique

Löllgen, Ruth Mari Caroline 14 July 2004 (has links)
Hintergrund: Karzinoid-Tumoren des embryonalen Mitteldarms sind seltene intestinale neuroendokrine Tumoren, bei denen zum Zeitpunkt der Diagnose häufig Metastasen vorliegen. Im Gegensatz zu Karzinoiden des Vorderdarms und Respirationstraktes sind sie nicht mit der Multiplen Endokrinen Neoplasie Typ 1 (MEN1) vergesellschaftet. Die Mechanismen ihrer Tumorigenesis sind weitgehend unbekannt. Methoden: Tumorgewebe acht sporadischer, maligner Dünndarm-Karzinoide war Objekt dieser Studie über Verlust der Heterozygotie ("Loss Of Heterozygosity" (LOH)) mit 131 fluoreszierenden Mikrosatelliten. DNA Sequenz-Analyse mit Oligonucleotid Primern, die Exon 8-11 des SMAD4/DPC4 Gens flankieren sowie immunhistochemische Färbung mit Smad4/DPC4 antikörpern wurde durchgeführt. Ergebnis: Chromosom 18 wies Deletionen in 88% der Tumoren auf. Alle außer einem Tumor hatten sowohl 18p als auch 18q verloren, in einem der Tumoren war eine kleine Region telomer zu den SMAD4/DPC4/DCC Genen auf 18q21 verloren. Andere Chromosomen waren nur in drei Tumoren betroffen. LOH auf Chromosom 11q13, dem MEN1 Lokus, wurde nicht gefunden.Sequenzierung der DNA und immunhistochemische Färbung für das SMAD4/DPC4 Gen zeigten keine Aberrationen. Diskussion: Die Funde der Chromosom 18 Deletionen weisen eindeutig auf ein entscheidendes Ereignis in der Tumorigenese von Karzinoiden des Mitteldarms hin. An der Entstehung dieser Tumoren könnte ein mutmaßliches Tumor Suppressor Gen beteiligt sein, welches auf Chromosom 18 lokalisiert ist. Dahingegen ist SMAD4/DPC4 wahrscheinlich nicht in die Tumorneogenese von Carcinois Tumoren involviert. / Background: Midgut carcinoid tumors are rare malignant tumors with origin in the neuroendocrine cells of the small intestine. Due to secretion of a variety of peptide hormones and biogenic amines they cause the carcinoid syndrome. Metastases are often present at first diagnosis. Despite this, patients have a realistic chance to survive for a prolonged period (30% (unresectable/metastatic disease) -79% (non-metastatic disease) 5-year survival rate) if treated by a combination of surgery and medication. Unlike their foregut counterparts, midgut carcinoid tumors are not or rarely associated with the multiple endocrine neoplasia type 1 (MEN1) syndrome. The genetic back-ground to tumorigenesis of these neoplasms is unknown. In contrast, the events involved in tumorigenesis of gastroenteropancreatic adenocarcinomas are better characterized with frequent mutations e.g. of the Smad4/DPC4, Smad2/MADR2/JV18-1 and DCC genes on chromosome 18. Methods: Eight metastatic midgut carcinoids were analysed by a genome-wide screening for loss of heterozygosity using 131 PCR-amplified fluorescent-labelled microsatellite markers. DNA sequence analysis using oligonucleotide primers flanking exons 8-11 of the Smad4/DPC4 gene and immunohistochemical staining with Smad4/DPC4 antibodies was performed. Results: Chromosome 18 was deleted in seven out of eight tumors (88%). All but one of these tumors had lost both 18p and 18q, the remaining tumor had lost the long arm but retained the short arm. Several other chromosomal alleles were lost in a subset of the tumors. Loss of heterozygosity (LOH) on chromosome 11q13, the MEN 1 locus, was not found. Smad4/DPC4 wild-type sequence and normal immunohistochemical staining for Smad4/DPC4 protein was found for all analysed tumors. Conclusions: Our finding of a high frequency of chromosome 18 deletions in 88% of the tumors strongly suggests that midgut carcinoid tumorigenesis might involve inactivation of a candidate tumor suppressor gene located in that region while Smad4/DPC4 is unlikely to be involved in that process. A more detailed analysis of the genetic events in midgut carcinoid tumors is warranted to clarify their neogenetic origin.
74

Souvislost mezi reaktivitou imunitního systému a atraktivitou obličeje / Relationship between reactivity of immune system and facial attractiveness

Slámová, Žaneta January 2018 (has links)
Previous studies have shown that physical attractiveness is one of important aspects in mate choice. Facial traits perceived as attractive may be linked to potential mate quality, or more precisely to their reproductive potential, health and ability to invest in his mate and offspring. Mating with individuals with more reactive immune system could lead to higher reproductive success and thus it is possible that visual cues facilitating detection of such traits may have evolved. The main aim of the present thesis was to test a possible association between the reactivity of the immune system response to foreign antigens (stimulated by vaccination) and facial attractiveness perceived by opposite sex individuals. Further, we investigated visual changes occurring during immune system activation. We did not find any association between measures of reactivity of immune system and perceived facial attractiveness. However, participants with activated immune system were rated as significantly less attractive and were significantly paler. Overall, our results suggest that people are sensitive to visual cues to current health status but not to overall quality of the individual. Key Words Facial attractiveness, mate choice, sexual selection; heterozygosity; symmetry; immune system, antigen; disease-avoidance,...
75

Management of Genetic Diversity in Conservation Programs Using Genomic Coancestry

Morales González, Elisabet 20 July 2023 (has links)
Tesis por compendio / [ES] Un objetivo fundamental en los programas de conservación es mantener la diversidad genética y la estrategia de gestión más eficiente para lograrlo es aplicar el método de Contribuciones Óptimas. Este método optimiza las contribuciones de los candidatos a reproductores minimizando el parentesco global ponderada, lo que conduce a niveles más altos de diversidad genética, medida como heterocigosis esperada, y a un control efectivo del aumento de consanguinidad. El parámetro fundamental de este método es la matriz de parentesco. Esta matriz se ha obtenido tradicionalmente a partir del pedigrí, pero la disponibilidad actual de genotipos para un gran número de polimorfismos de un solo nucleótido (SNP) nos permite estimarla con una mayor precisión. Sin embargo, se han propuesto muchas medidas de parentesco genómico y se desconoce qué medida es la más apropiada para minimizar la pérdida de diversidad genética. Por lo tanto, el objetivo general de esta tesis fue investigar la eficiencia de diferentes matrices genómicas de parentesco en la gestión de poblaciones en programas de conservación, cuando se aplica el método de Contribuciones Óptimas. Las matrices comparadas fueron aquellas basadas en: i) la proporción de alelos compartidos por dos individuos (CSIM); ii) las desviaciones del número observado de alelos compartidos por dos individuos respecto del número esperado (CL&H); iii) la matriz de relaciones genómicas obtenida a través el método 1 de VanRaden (CVR1); iv) la matriz de relaciones genómicas obtenida a través el método 2 de VanRaden (CVR2); v) la matriz de relaciones genómicas obtenida a través el método de Yang (CYAN); y vi) segmentos idénticos por descendencia (CSEG). Los resultados para una sola generación, usando miles de SNP genotipados en individuos de una población cultivada de rodaballo, mostraron grandes diferencias en la magnitud de los seis coeficientes de parentesco. Las correlaciones entre los diferentes coeficientes variaron mucho, siendo las más bajas aquellas entre CSIM, CL&H o CSEG y CVR2 o CYAN. La gestión que utiliza matrices basadas en la proporción de alelos o segmentos compartidos (CSIM, CL&H y CSEG) retuvieron una mayor diversidad que aquella que utiliza matrices de relaciones genómicas (CVR1, CVR2 y CYAN). Como era de esperar, maximizar la heterocigosis llevó los alelos hacia frecuencias intermedias. Sin embargo, alejar las frecuencias alélicas de las frecuencias iniciales puede ser indeseable, ya que se pueden perder adaptaciones particulares al medio. Se utilizaron simulaciones estocásticas para investigar la eficiencia de CL&H y CVR2 en el manejo de poblaciones no divididas a lo largo de 50 generaciones y ambas matrices se compararon tanto en términos de la diversidad genética como en términos de los cambios asociados en las frecuencias alélicas. EL uso de CL&H en el método de Contribuciones Óptimas llevó a una mayor diversidad genética pero también en un mayor cambio de frecuencias alélicas que el uso de CVR2. Las diferencias entre estrategias fueron menores cuando sólo se usaron SNP con una frecuencia del alelo menos común (MAF) por encima de un umbral particular (MAF > 0.05 y MAF > 0.25) para calcular CL&H y CVR2 así como cuando se aplicó el método de Contribuciones Óptimas en poblaciones con censo más pequeños (se pasó de N = 100 a N = 20). La evaluación de CL&H y CVR2 se extendió a poblaciones subdivididas, también a través de simulaciones por ordenador. En poblaciones subdivididas, la diversidad genética se distribuye en dos componentes: dentro y entre subpoblaciones. Cuando se otorga un mayor peso al componente dentro de subpoblaciones, es posible restringir los niveles de consanguinidad. Bajo este escenario, la utilización de CL&H resultó ser la mejor opción para gestionar este tipo de poblaciones, ya que mantuvo una mayor diversidad global, condujo a una menor consanguinidad y a cambios en las frecuencias similares a los observados cuando se utilizó CVR2. / [CA] Un objectiu fonamental en els programes de conservació és mantindré la diversitat genètica i l'estratègia de gestió més eficient per aconseguir-ho és aplicar el mètode de contribucions òptimes. Aquest mètode optimitza les contribucions dels candidats a reproductors minimitzant el parentiu global ponderat, cosa que condueix a nivells més alts de diversitat genètica, mesurada com a heterozigosi esperada, i a un control efectiu de l'augment de consanguinitat. El paràmetre fonamental d'aquest mètode és la matriu de parentiu. Aquesta matriu s'ha obtingut tradicionalment a partir del pedigrí, però la disponibilitat actual de genotips per a un gran nombre de polimorfismes d'un sol nucleòtid (SNP) ens permet estimar-la amb més precisió. Tot i això, s'han proposat moltes mesures de parentiu genòmic i es desconeix quina mesura és la més apropiada per minimitzar la pèrdua de diversitat genètica. Per tant, l'objectiu general d'aquesta tesi va ser investigar l'eficiència de diferents matrius genòmiques de parentiu en la gestió de poblacions en programes de conservació, quan s'aplica el mètode de Contribucions Òptimes. Les matrius comparades van ser aquelles basades en: i) la proporció d'al·lels compartits per dos individus (CSIM); ii) les desviacions del nombre observat d'al·lels compartits per dos individus respecte del nombre esperat (CL&H); iii) la matriu de relacions genòmiques obtinguda a través del mètode 1 de VanRaden (CVR1); iv) la matriu de relacions genòmiques obtinguda a través del mètode 2 de VanRaden (CVR2); v) la matriu de relacions genòmiques obtinguda a través del mètode de Yang (CYAN); i vi) segments idèntics per descendència (CSEG). Els resultats per a una sola generació, usant milers d'SNP genotipats en individus d'una població cultivada de turbot, van mostrar grans diferències en la magnitud dels sis coeficients de parentiu. Les correlacions entre els coeficients van variar molt, sent les més baixes aquelles entre CSIM, CL&H o CSEG i CVR2 o CYAN. La gestió que utilitza matrius basades en la proporció d'al·lels o segments compartits (CSIM, CL&H i CSEG) van retindré una diversitat més gran que aquella que utilitza matrius de relacions genòmiques (CVR1, CVR2 i CYAN). Com calia esperar, la màxima heterozigosi va portar els al·lels cap a freqüències intermèdies. No obstant això, allunyar les freqüències al·lèliques de les freqüències inicials pot ser indesitjable, ja que es poden perdre adaptacions particulars al medi. Es van fer servir simulacions estocàstiques per investigar l'eficiència de CL&H i CVR2 en el maneig de poblacions no dividides al llarg de 50 generacions i les dues matrius es van comparar tant en termes de la diversitat genètica com en termes dels canvis associats a les freqüències al·lèliques. L'ús de CL&H en el mètode de Contribucions Òptimes va resultar en una major diversitat genètica però també en un canvi més gran de freqüències al·lèliques que l'ús de CVR2. Les diferències entre estratègies van ser menors quan només es van fer servir SNP amb una freqüència de l'al·lel menys comú (MAF) per sobre d'un llindar particular (MAF > 0.05 i MAF > 0.25) per calcular CL&H i CVR2 així com quan es va aplicar el mètode de Contribucions Òptimes en poblacions amb cens més petit (es va passar de N = 100 a N = 20). L'avaluació de CL&H i CVR2 es va estendre a poblacions subdividides, també a través de simulacions per ordinador. En poblacions subdividides, la diversitat genètica es distribueix en dos components: dins i entre subpoblacions. Quan s'atorga un pes més gran al component dins de subpoblacions, és possible restringir els nivells de consanguinitat. Sota aquest escenari, la utilització de CL&H va resultar ser la millor opció per gestionar aquest tipus de poblacions, ja que va mantindré una diversitat global més gran, va conduir a una menor consanguinitat i a canvis en les freqüències similars als observats quan es va utilitzar CVR2. / [EN] A main objective in conservation programs is to maintain genetic diversity, and the most efficient management strategy to achieve it is to apply the Optimal Contributions method. This method optimizes the contributions of breeding candidates by minimizing the global weighted coancestry. This leads to the highest levels of genetic diversity, when measured as expected heterozygosity, and to an effective control of the increase of inbreeding. The fundamental parameter of the method is the coancestry matrix which, traditionally, has been obtained from pedigree data. The current availability of genome-wide information allows us to estimate coancestries with higher precision. However, many different genomic coancestry measures have been proposed and it is unknown which measure is more efficient to minimize the loss of genetic diversity. Thus, the general aim of this thesis was to investigate the efficiency of different genomic coancestry matrices in the management of conserved populations when the Optimal Contributions method is applied to maximize genetic diversity. The matrices compared were those based on: i) the proportion of shared alleles (CSIM); ii) deviations of the observed number of alleles shared by two individuals from the expected number (CL&H); iii) the realized relationship matrix obtained by VanRaden's method 1 (CVR1); iv) the realized relationship matrix obtained by VanRaden's method 2 (CVR2); v) the realized relationship matrix obtained by Yang¿s method (CYAN); and vi) identical by descent segments (CSEG). Results for a single generation using thousands of SNP genotyped in individuals from a farm turbot population, showed large differences in the magnitude of the six coancestry coefficients. Moreover, pairwise correlations were those between coefficients greatly varied (especially for self-coancestry). The lowest correlations between CSIM, CL&H or CSEG and CVR2 or CYAN. Management with matrices based on the proportion of shared alleles or on segments (CSIM, CL&H and CSEG) retained higher variability than those based on realized genomic relationship matrices (CVR1, CVR2 and CYAN). As expected, maximizing heterozygosity pushed alleles toward intermediate frequencies. However, moving allele frequencies away from initial frequencies may be undesirable as particular adaptations to the environment can be lost. Stochastic simulations were used to investigate the efficiency of CL&H and CVR2 in the management of an undivided population across 50 generations and both matrices were compared not only in terms of the genetic diversity maintained but also in terms of the associated changes in allele frequencies across generations. The use of CL&H in the Optimal Contribution method resulted in a higher genetic diversity but also in a higher change of allele frequencies than the use of CVR2. The differences between strategies were reduced when only SNPs with a minimum allele frequency (MAF) above a particular threshold (MAF > 0.05 and MAF > 0.25) were used to compute CL&H and CVR2 as well as when the Optimal Contributions method was applied in populations of smaller sizes (N = 20 vs N = 100). The evaluation of CL&H and CVR2 was extended to subdivided populations, also via computer simulations. When populations are subdivided into different breeding groups, it is possible to give different weights to the within- and between-subpopulation components of genetic diversity. When a higher weight is given to the within-subpopulation component, the levels of inbreeding can be restricted. In this scenario, the use of CL&H was the best option for managing subdivided populations as it maintained more global diversity, led to less inbreeding and to changes in frequencies similar to those observed when using CVR2 when a large weight was given to the within-subpopulation term. / Esta tesis doctoral se realizó en el Instituto de Investigación y Tecnología Agraria y Alimentaria (INIA-CSIC) de Madrid. El trabajo expuesto en el capítulo 2 se realizó en parte en el Instituto Roslin, de la Universidad de Edimburgo durante una estancia predoctoral. Los trabajos expuestos en la tesis han sido financiados con una beca predoctoral FPI (BES-2017-081070) y a través de proyectos del Plan Estatal de I+D+i del Ministerio de Ciencia e Innovación (proyectos CGL2016-75904-C2-2-P y PID2020- 114426GB-C22) y de la Unión Europea (‘European Union‘s Seventh Framework Program, KBBE.2013.1.2-10, under Grant Agreement No. 613611, FISHBOOST project’ y ‘European Commission Horizon 2020, Framework Programme through Grant Agreement No. 727315, MedAID project’). / Morales González, E. (2023). Management of Genetic Diversity in Conservation Programs Using Genomic Coancestry [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/195231 / Compendio
76

Mécanismes moléculaires sous-jacents au développement du médulloblastome

Racicot, Frédéric 11 1900 (has links)
Le médulloblastome est une des tumeurs les plus fréquentes du système nerveux central chez l’enfant. Son impact clinique, ainsi que les effets secondaires engendrés par les traitements actuels, sont significatifs en matière de morbidité et de mortalité. La caractérisation moléculaire des tumeurs du système nerveux central a grandement évolué, et ce, particulièrement en ce qui concerne le médulloblastome. Des travaux antérieurs ont permis d’établir qu’un des sous-groupes de médulloblastome est caractérisé par l’activation de la voie sonic hedgehog. La mutation la plus fréquente menant à ce sous-type de médulloblastome est la mutation du gène suppresseur de tumeur PTCH1. Grâce au modèle de souris Ptch1+/-, des données issues de notre laboratoire ont permis de caractériser le développement de cette tumeur comme étant en deux étapes. Ce travail porte sur la caractérisation du mécanisme par lequel cette première étape, soit la perte d’hétérozygotie de Ptch1, survient. Tout d’abord, nous revisitons le rôle in vivo du corécepteur Boc dans la tumorigenèse. Selon nos résultats, la modulation de Boc ne semble pas avoir un impact significatif sur le développement tumoral dans des expériences de transplantation orthotopiques. Ensuite, nous démontrons que le ligand Shh augmente le dommage à l’ADN, ce qui mène à une hausse des évènements de recombinaisons qui peuvent causer une perte d’hétérozygotie. Nous tentons de moduler l’activité de Rad51 en observant une tendance non statistiquement significative des évènements de recombinaison avec des inhibiteurs de Rad51. Nous démontrons ensuite qu’un inhibiteur de Cdc7 permet la diminution des évènements de recombinaisons ainsi qu’une diminution du stress réplicatif de l’ADN. En intervenant sur le gène Mcm2 grâce à un modèle de souris transgénique, nous parvenons à prouver qu’une diminution de l’action de Mcm2 permet une diminution du stress réplicatif de l’ADN. En somme, la première étape du développement du médulloblastome sonic hedgehog-activé est la perte d’hétérozygotie de Ptch1. Celle-ci est caractérisée par une augmentation du dommage à l’ADN engendrant une hausse des évènements de recombinaison. Plusieurs cibles potentielles de modulation s’avèrent prometteuses pour un éventuel traitement ciblé. / Medulloblastoma is one of the most common central nervous system tumors of the child. Its clinical impact, as well as the adverse effects caused by current treatments, are significant in terms of morbidity and mortality. The molecular characterization of tumors of the central nervous system has greatly evolved, particularly in the case of medulloblastoma. Previous work has established that one of the medulloblastoma sub-groups is characterized by the activation of the sonic hedgehog (Shh) pathway. The most common mutation leading to this medulloblastoma subtype is the PTCH1 tumor suppressor gene mutation. Working with the Ptch1+/- mouse model, data from our la-boratory characterized the medulloblastoma tumorigenesis as a two-step process. This work focuses on the characterization of the mechanism by which this first step, the loss of heterozygosity of Ptch1, occurs. First, we revisit the in vivo role of the Boc coreceptor in the medulloblastoma tumor-igenesis. According to our results, Boc modulation does not seem to have a significant impact on tumor development. Next, we show that the Shh ligand increases DNA dam-age. This leads to an increase in recombination events which predispose to loss of het-erozygosity. We attempt to modulate Rad51 activity and observe a non-statistically sig-nificant trend to decrease recombination events with Rad51 inhibitors. We then demonstrate that Cdc7 inhibition reduces recombination events as well as DNA replica-tive stress. Using an Mcm2 transgenic mouse model, we demonstrate that a reduction in the action of Mcm2 reduces DNA replicative stress. To conclude, the first step in the development of Shh-activated medulloblastoma is the loss of heterozygosity of Ptch1. This is characterized by an increase in DNA damage leading to an increase in recombination events. Several potential modulation targets hold promise for possible targeted therapy.
77

Évaluation du caryotype moléculaire en tant qu’outil diagnostique chez les enfants avec déficience intellectuelle et/ou malformations congénitales

D'Amours, Guylaine 05 1900 (has links)
Le caryotype moléculaire permet d’identifier un CNV chez 10-14% des individus atteints de déficience intellectuelle et/ou de malformations congénitales. C’est pourquoi il s’agit maintenant de l’analyse de première intention chez ces patients. Toutefois, le rendement diagnostique n’est pas aussi bien défini en contexte prénatal et l’identification de CNVs de signification clinique incertaine y est particulièrement problématique à cause du risque d’interruption de grossesse. Nous avons donc testé 49 fœtus avec malformations majeures et un caryotype conventionnel normal avec une micropuce CGH pangénomique, et obtenu un diagnostic dans 8,2% des cas. Par ailleurs, des micropuces à très haute résolution combinant le caryotype moléculaire et le génotypage de SNPs ont récemment été introduites sur le marché. En plus d’identifier les CNVs, ces plateformes détectent les LOHs, qui peuvent indiquer la présence d’une mutation homozygote ou de disomie uniparentale. Ces anomalies pouvant être associées à la déficience intellectuelle ou à des malformations, leur détection est particulièrement intéressante pour les patients dont le phénotype reste inexpliqué. Cependant, le rendement diagnostique de ces plateformes n’est pas confirmé, et l’utilité clinique réelle des LOHs n’est toujours pas établie. Nous avons donc testé 21 enfants atteints de déficience intellectuelle pour qui les méthodes standards d’analyse génétique n’avaient pas résulté en un diagnostic, et avons pu faire passer le rendement diagnostique de 14,3% à 28,6% grâce à l’information fournie par les LOHs. Cette étude démontre l’utilité clinique d’une micropuce CGH pangénomique chez des fœtus avec malformations, de même que celle d’une micropuce SNP chez des enfants avec déficience intellectuelle. / Molecular karyotyping identifies a CNV in 10-14% of individuals affected with intellectual disability and/or congenital abnormalities. Therefore, it is now the first-tier analysis for these patients. However, the diagnostic yield is not as clear in the prenatal context, and the risk of pregnancy termination makes the detection of variants of uncertain clinical significance particularly problematic. We tested 49 fetuses with major malformations and a normal karyotype, using a pangenomic CGH array, and obtained a diagnosis in 8.2% of cases. Furthermore, high-resolution microarrays combining molecular karyotyping and SNP genotyping were recently introduced on the market. In addition to identifying CNVs, these platforms detect LOHs, which can indicate the presence of a homozygous mutation or of uniparental disomy. Since these abnormalities can be associated with intellectual disability or congenital abnormalities, their detection is of particular interest for patients whose phenotype remains unexplained. However, the diagnostic yield obtained with these platforms is not confirmed, and the real clinical value of LOH detection is not yet established. We tested 21 children affected with intellectual disability for whom standard genetic analyses failed to provide a diagnosis, and were able to increase the diagnostic yield from 14.3% to 28.6% as a result of the information provided by LOHs. This study shows the clinical usefulness of pangenomic CGH arrays in fetuses with malformation(s), as well as that of SNP arrays in children with intellectual disability.
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Estudo da expressão dos receptores do peptídeo insulinotrópico dependente de glicose (GIPR) e do hormônio luteinizante (LHCGR) em tumores e hiperplasias do córtex adrenal / Expression Study of Glucose-dependent insulinotropic peptide receptor (GIPR) and luteinizing hormone receptor (LHCGR) in adrenocortical tumors and hyperplasia

Costa, Marcia Helena Soares 16 July 2007 (has links)
Introdução: Os receptores do peptídeo insulinotrópico dependente de glicose (GIPR) e do hormônio luteinizante (LHCGR) são receptores acoplados à proteína G com amplo padrão de expressão tecidual. A expressão anômala destes receptores tem sido descrita em casos de hiperplasia adrenal macronodular independente de ACTH (AIMAH) e em alguns adenomas, resultando em aumento da secreção hormonal (cortisol, andrógenos e aldosterona) pelo cortex adrenal. O papel destes receptores em outras formas de hiperplasia, como a doença adrenocortical nodular pigmentosa primária (PPNAD), aumento da adrenal associado à neoplasia endócrina múltipla tipo 1 (MEN1), e em carcinoma do córtex adrenal tem sido pouco investigado; sendo assim, considera-se relevante estudar a expressão destes receptores nos pacientes com tumores adrenocorticais esporádicos, nos pacientes com AIMAH, PPNAD e aumento adrenal associado à MEN1. Objetivos: 1) Caracterização molecular dos casos de neoplasia endócrina múltipla tipo 1 e PPNAD: pesquisa de mutações dos genes MEN1 e PRKAR1A e análise da perda de heterozigose (LOH) destes genes no tecido adrenal destes pacientes. 2) Quantificar a expressão do GIPR e do LHCGR em tecido adrenocortical normal, tumoral, hiperplásico e correlacionar a expressão destes com a classificação histológica dos tumores adrenocorticais. Pacientes: 55 pacientes (30 adultos) com tumores adrenocorticais (37 adenomas e 18 carcinomas); 7 pacientes com AIMAH, 4 com MEN1, 1 com PPNAD e tecidos controles (adrenal; testículo e pâncreas). Métodos: extração de DNA genômico, RNA e síntese de DNA complementar (cDNA); amplificação por PCR das regiões codificadoras dos genes MEN1 e PRKAR1A seguida por seqüenciamento automático. Pesquisa de LOH pela amplificação de microssatélites por PCR e análise pelo programa GeneScan. Quantificação da expressão do GIPR e do LHCGR por PCR em tempo real pelo método TaqMan e estudo de imunohistoquímica para GIPR nos tumores adrenocorticais. Resultados: identificação de 3 mutações (893+ 1G>A, W183X e A68fsX118) e dois polimorfirmos (S145S e D418D) no gene MEN1 e uma mutação (Y21X) no PRKAR1A. Ausência de LOH nos tecidos adrenais estudados. A expressão do GIPR e do LHCGR foi identificada em tecidos adrenais normais, tumorais e hiperplásicos. O nível de expressão do GIPR foi mais elevado nos tumores adrenocorticais malignos que nos benignos tanto no grupo pediátrico (mediana= 18,1 e 4,6, respectivamente; p <0,05), quanto no grupo adulto (mediana = 4,8 e 1,3 respectivamente; p <0,001). O nível de expressão do LHCGR, no grupo pediátrico, foi elevado tanto nos tumores benignos quanto nos malignos (mediana= 6,4 e 4,3, respectivamente). No grupo adulto os níveis de expressão deste receptor foram extremamente baixos nos tumores malignos em relação aos benignos (mediana= 0,06 e 2,3, respectivamente; p <0,001). A imunohistoquímica para o GIPR foi variável e não correlacionada à expressão do gene GIPR. Não houve diferença nos níveis de expressão do GIPR e do LHCGR nas hiperplasias do córtex adrenal. Conclusões: a presença de LOH e mutação em heterozigose composta do gene MEN1 e do PRKAR1A foram afastadas como mecanismos responsáveis pelo aumento adrenal tanto nos pacientes com MEN1 como no paciente com PPNAD. A hiperexpressão de GIPR está associada a malignidade nos tumores adrenocorticais nos grupos adulto e pediátrico e a baixa expressão de LHCGR está associada a malignidade nos tumores adrenocorticais somente no grupo adulto. / Introduction: The glucose- dependent insulinotropic peptide receptor (GIPR) and luteinizing hormone receptor (LHCGR) are G-protein coupled receptors with a wide tissue expression pattern. The aberrant expression of these receptors has been described in cases of ACTH-independent macronodular adrenal hyperplasia (AIMAH) and in some adenomas, resulting in the increase of adrenal cortex hormonal secretion (cortisol, androgens and aldosterone). The role of these receptors in other forms of adrenocortical hyperplasia, such as primary pigmented nodular adrenocortical disease (PPNAD), adrenal enlargement associated with multiple endocrine neoplasia type 1 (MEN1), and adrenocortical carcinoma has been scarcely investigated. Thus, the study of the expression of these receptors in patients with sporadical adrenocortical tumors, AIMAH, PPNAD and adrenal enlargement associated to MEN1 was considered important. Objectives: 1) Molecular study in patients with multiple endocrine neoplasia type 1 and PPNAD: mutation screening of MEN1 and PRKAR1A genes and analysis of the loss of heterozygosis (LOH) of these genes in the adrenal lesions of these patients. 2) To quantify the GIPR and LHCGR expression, in normal, tumor and hyperplasic tissue and to correlate the expression of these receptors with the adrenocortical tumor histology. Patients: 55 patients (30 adults) with adrenocortical tumors (37 adenomas and 18 carcinomas); 7 patients with AIMAH, 4 with MEN1, 1 with PPNAD and control tissue (adrenal, testis and pancreas). Methods: Extraction of genomic DNA, RNA and synthesis of complementary DNA (cDNA); PCR-amplification of the coding regions of MEN1 and PRKAR1A, followed by direct sequencing. LOH study using polymorphic marker amplification by PCR and GeneScan software analysis. Quantification of GIPR and LHCGR expression using realtime PCR -TaqMan method and GIPR immunohistochemistry study in adrenocortical tumors. Results: Identification of 3 mutations (893+ 1G>A, W183X and A68fsX118) and two polymorphic alterations (S145S and D418D) in MEN1 and a mutation (Y21X) in the PRKAR1A gene; LOH was not identified in adrenal tissue. The GIPR and LHCGR expression was identified in normal, tumor and hyperplasic adrenal tissues; the GIPR expression level was more elevated in malignant tumors compared to benign tumors in pediatric (median = 18.1 and 4.6, respectively; p <0.05) and adult patients (median = 4.8 and 1.3 respectively; p <0.001). The LHCGR expression in pediatric patients was elevated in benign as well as in malignant tumors (median = 6.4 and 4.3, respectively). In the adult group, the expression level of these receptors was extremely low in malignant tumors in relation to benign ones (median = 0.06 and 2.3, respectively; p <0.001). The GIPR immunohistochemistry was variable and did not correlate with GIPR gene expression. No difference between GIPR and LHCGR expression levels was observed in the different forms of hyperplasia. Conclusions: The presence of LOH and mutations in compound heterozygosis of MEN1 and PRKAR1A genes were ruled out as the mechanisms responsible for the adrenal enlargement in patients with multiple endocrine neoplasia type 1. GIPR overexpression is associated with malignant adrenocortical tumors in the adult and pediatric patients and low LHCGR expression is associated with malignant adrenocortical tumors only in the adult patients.
79

Estudo da expressão dos receptores do peptídeo insulinotrópico dependente de glicose (GIPR) e do hormônio luteinizante (LHCGR) em tumores e hiperplasias do córtex adrenal / Expression Study of Glucose-dependent insulinotropic peptide receptor (GIPR) and luteinizing hormone receptor (LHCGR) in adrenocortical tumors and hyperplasia

Marcia Helena Soares Costa 16 July 2007 (has links)
Introdução: Os receptores do peptídeo insulinotrópico dependente de glicose (GIPR) e do hormônio luteinizante (LHCGR) são receptores acoplados à proteína G com amplo padrão de expressão tecidual. A expressão anômala destes receptores tem sido descrita em casos de hiperplasia adrenal macronodular independente de ACTH (AIMAH) e em alguns adenomas, resultando em aumento da secreção hormonal (cortisol, andrógenos e aldosterona) pelo cortex adrenal. O papel destes receptores em outras formas de hiperplasia, como a doença adrenocortical nodular pigmentosa primária (PPNAD), aumento da adrenal associado à neoplasia endócrina múltipla tipo 1 (MEN1), e em carcinoma do córtex adrenal tem sido pouco investigado; sendo assim, considera-se relevante estudar a expressão destes receptores nos pacientes com tumores adrenocorticais esporádicos, nos pacientes com AIMAH, PPNAD e aumento adrenal associado à MEN1. Objetivos: 1) Caracterização molecular dos casos de neoplasia endócrina múltipla tipo 1 e PPNAD: pesquisa de mutações dos genes MEN1 e PRKAR1A e análise da perda de heterozigose (LOH) destes genes no tecido adrenal destes pacientes. 2) Quantificar a expressão do GIPR e do LHCGR em tecido adrenocortical normal, tumoral, hiperplásico e correlacionar a expressão destes com a classificação histológica dos tumores adrenocorticais. Pacientes: 55 pacientes (30 adultos) com tumores adrenocorticais (37 adenomas e 18 carcinomas); 7 pacientes com AIMAH, 4 com MEN1, 1 com PPNAD e tecidos controles (adrenal; testículo e pâncreas). Métodos: extração de DNA genômico, RNA e síntese de DNA complementar (cDNA); amplificação por PCR das regiões codificadoras dos genes MEN1 e PRKAR1A seguida por seqüenciamento automático. Pesquisa de LOH pela amplificação de microssatélites por PCR e análise pelo programa GeneScan. Quantificação da expressão do GIPR e do LHCGR por PCR em tempo real pelo método TaqMan e estudo de imunohistoquímica para GIPR nos tumores adrenocorticais. Resultados: identificação de 3 mutações (893+ 1G>A, W183X e A68fsX118) e dois polimorfirmos (S145S e D418D) no gene MEN1 e uma mutação (Y21X) no PRKAR1A. Ausência de LOH nos tecidos adrenais estudados. A expressão do GIPR e do LHCGR foi identificada em tecidos adrenais normais, tumorais e hiperplásicos. O nível de expressão do GIPR foi mais elevado nos tumores adrenocorticais malignos que nos benignos tanto no grupo pediátrico (mediana= 18,1 e 4,6, respectivamente; p <0,05), quanto no grupo adulto (mediana = 4,8 e 1,3 respectivamente; p <0,001). O nível de expressão do LHCGR, no grupo pediátrico, foi elevado tanto nos tumores benignos quanto nos malignos (mediana= 6,4 e 4,3, respectivamente). No grupo adulto os níveis de expressão deste receptor foram extremamente baixos nos tumores malignos em relação aos benignos (mediana= 0,06 e 2,3, respectivamente; p <0,001). A imunohistoquímica para o GIPR foi variável e não correlacionada à expressão do gene GIPR. Não houve diferença nos níveis de expressão do GIPR e do LHCGR nas hiperplasias do córtex adrenal. Conclusões: a presença de LOH e mutação em heterozigose composta do gene MEN1 e do PRKAR1A foram afastadas como mecanismos responsáveis pelo aumento adrenal tanto nos pacientes com MEN1 como no paciente com PPNAD. A hiperexpressão de GIPR está associada a malignidade nos tumores adrenocorticais nos grupos adulto e pediátrico e a baixa expressão de LHCGR está associada a malignidade nos tumores adrenocorticais somente no grupo adulto. / Introduction: The glucose- dependent insulinotropic peptide receptor (GIPR) and luteinizing hormone receptor (LHCGR) are G-protein coupled receptors with a wide tissue expression pattern. The aberrant expression of these receptors has been described in cases of ACTH-independent macronodular adrenal hyperplasia (AIMAH) and in some adenomas, resulting in the increase of adrenal cortex hormonal secretion (cortisol, androgens and aldosterone). The role of these receptors in other forms of adrenocortical hyperplasia, such as primary pigmented nodular adrenocortical disease (PPNAD), adrenal enlargement associated with multiple endocrine neoplasia type 1 (MEN1), and adrenocortical carcinoma has been scarcely investigated. Thus, the study of the expression of these receptors in patients with sporadical adrenocortical tumors, AIMAH, PPNAD and adrenal enlargement associated to MEN1 was considered important. Objectives: 1) Molecular study in patients with multiple endocrine neoplasia type 1 and PPNAD: mutation screening of MEN1 and PRKAR1A genes and analysis of the loss of heterozygosis (LOH) of these genes in the adrenal lesions of these patients. 2) To quantify the GIPR and LHCGR expression, in normal, tumor and hyperplasic tissue and to correlate the expression of these receptors with the adrenocortical tumor histology. Patients: 55 patients (30 adults) with adrenocortical tumors (37 adenomas and 18 carcinomas); 7 patients with AIMAH, 4 with MEN1, 1 with PPNAD and control tissue (adrenal, testis and pancreas). Methods: Extraction of genomic DNA, RNA and synthesis of complementary DNA (cDNA); PCR-amplification of the coding regions of MEN1 and PRKAR1A, followed by direct sequencing. LOH study using polymorphic marker amplification by PCR and GeneScan software analysis. Quantification of GIPR and LHCGR expression using realtime PCR -TaqMan method and GIPR immunohistochemistry study in adrenocortical tumors. Results: Identification of 3 mutations (893+ 1G>A, W183X and A68fsX118) and two polymorphic alterations (S145S and D418D) in MEN1 and a mutation (Y21X) in the PRKAR1A gene; LOH was not identified in adrenal tissue. The GIPR and LHCGR expression was identified in normal, tumor and hyperplasic adrenal tissues; the GIPR expression level was more elevated in malignant tumors compared to benign tumors in pediatric (median = 18.1 and 4.6, respectively; p <0.05) and adult patients (median = 4.8 and 1.3 respectively; p <0.001). The LHCGR expression in pediatric patients was elevated in benign as well as in malignant tumors (median = 6.4 and 4.3, respectively). In the adult group, the expression level of these receptors was extremely low in malignant tumors in relation to benign ones (median = 0.06 and 2.3, respectively; p <0.001). The GIPR immunohistochemistry was variable and did not correlate with GIPR gene expression. No difference between GIPR and LHCGR expression levels was observed in the different forms of hyperplasia. Conclusions: The presence of LOH and mutations in compound heterozygosis of MEN1 and PRKAR1A genes were ruled out as the mechanisms responsible for the adrenal enlargement in patients with multiple endocrine neoplasia type 1. GIPR overexpression is associated with malignant adrenocortical tumors in the adult and pediatric patients and low LHCGR expression is associated with malignant adrenocortical tumors only in the adult patients.

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