Effets de la consanguinite sur les traits d'histoire de vie, les caracteristiques morphologiques et le choix de partenaire du mouflon d'amerique (Ovis canadensis)

La consanguinité peut générer d'importants effets négatifs en diminuant l'aptitude phénotypique des individus consanguins. Dans de petites populations isolées, les événements de consanguinité devraient être davantage fréquents. Cependant, l'étude de la consanguinité en nature est rare, car peu d'études ont la possibilité de documenter les liens de parenté de façon précise. L'étude à long terme portant sur le mouflon d'Amérique (Ovis canadensis) à Ram Mountain, Alberta, nous a permis d'établir le pedigree et de calculer le coefficient de consanguinité (f ) des agneaux et d'avoir différentes mesures liées à la masse corporelle et à la survie des individus. Également, la population a subi un déclin majeur dans les dernières années dû d'abord à des effets de densité-dépendance et par la suite à une forte prédation par le couguar. Quoique ces facteurs ne soient plus présents dans la population, elle demeure toujours à une faible taille, entre 15 et 23 femelles matures. Il est donc important d'établir si la consanguinité est en cause dans le maintien de ce faible effectif pour mieux gérer et protéger la population. Mon étude avait trois objectifs principaux. Premièrement, je voulais quantifier l'occurrence de la consanguinité dans la population au fil des années (de 1988 à 2008) et en fonction de sa taille. Puis, je voulais quantifier les effets de la consanguinité sur la masse des individus, leur date de naissance et leur survie pour évaluer l'importance de la dépression consanguine dans la population. Finalement, je voulais déterminer si les mouflons ont développé des mécanismes d'évitement de la consanguinité. Mes analyses ont révélé que le coefficient moyen de consanguinité des agneaux a augmenté avec une baisse de la taille de la population. Plus particulièrement, le nombre de mâles âgés de 5 ans et plus dans la population semblait être fortement corrélé avec la consanguinité.La consanguinité n'avait aucun effet sur la masse des agneaux, que ce soit au mois de juin ou septembre, sur le gain en masse et sur la date de naissance. Par contre, elle avait un effet majeur sur la survie hivernale des agneaux femelles, mais pas chez les mâles. Pour avoir la même probabilité de survie que les femelles non-consanguines, les consanguines devaient avoir une masse à la mi-septembre 50% plus élevée. Également, les agneaux femelles consanguins étaient significativement plus lourds au mois de septembre que les non-consanguins. Cette même tendance se répétait pour les femelles âgées d'un an au mois de juin. Une explication possible à ces observations est que les agneaux consanguins très légers sont morts avant d'être échantillonnés. Ces résultats permettent de mieux comprendre pourquoi la dépression consanguine est plus difficilement détectable à des stades de vie plus vieux et pourquoi il est parfois difficile d'établir des corrélations entre des mesures de génétique et la valeur de divers traits. Par exemple, si les pressions de sélection sont plus fortes pour les individus consanguins, des individus homozygotes peuvent avoir une masse plus élevée que des individus hétérozygotes. Puis, j'ai calculé un coefficient moyen de consanguinité à chaque année en simulant des accouplements aléatoires afin de voir si les accouplements entre individus apparentés survenaient moins souvent qu'aléatoirement. Le coefficient simulé n'était pas significativement différent de celui observé dans la population. Également, les mouflons n'évitaient pas les accouplements avec des individus hautement apparentés. Deux explications sont possibles : les mouflons ne semblent pas avoir développé des mécanismes d'évitement de la consanguinité ou, étant donné le faible nombre de partenaires potentiels, ils sont contraints à se reproduire avec des individus apparentés.La première explication semble plus probable étant donné le mode d'appariement polygyne du mouflon qui favorise à la base les événements de consanguinité, le coût de la consanguinité sur la survie seulement chez les femelles et non chez les mâles, la faible fréquence des rencontres avec un individu hautement apparenté et la migration lors du rut qui a été observée dans d'autres populations de mouflon non isolées qui permettrait l'évitement de la consanguinité. Tous ces résultats sont importants pour deux raisons. Premièrement, pour mieux comprendre le phénomène de la consanguinité. Deuxièmement, ils sont importants dans une optique de conservation des populations surtout considérant que, dans les dernières années, les taux de survie ont été très faibles dans la population à l'étude ce qui a entraîné une chute drastique de sa taille. Les résultats sont également potentiellement applicables aux populations qui subissent un déclin drastique suite à la destruction ou à la fragmentation des habitats, un scénario souvent observé de nos jours par exemple par la déforestation ou la construction de routes

La génétique au service de la conservation d'une espèce menacée endémique à Madagascar : la tortue radiée Astrochelys radiata

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

Evaluation of experimental genetic management in reintroduced bighorn sheep

Positive demographic responses have been reported in several species where the immigration or supplementation of genetically distinct individuals into wild populations has resulted in a genetic rescue effect. However, rarely have researchers incorporated what could be considerable risk of outbreeding depression into planning for genetic management programs. We assess the genetic effects of an experiment in genetic management involving replicate populations of California bighorn sheep (Ovis canadensis californiana) in Oregon, USA, which previously experienced poor productivity and numerical declines. In the experiment, two declining populations were supplemented with ewes from a more genetically diverse population of California bighorn sheep in Nevada. We incorporated analysis of genetic samples representing both experimental populations prior to supplementation, samples from the supplemented individuals, and samples collected from both experimental populations approximately one generation after supplementation. We used genetic analyses to assess the integration of supplemented and resident populations by identifying interpopulation hybrids. Further, we incorporated demographic simulations to assess the risk of outbreeding depression as a result of the experimental augmentation. Finally, we used data from microsatellites and mitochondrial sequences to determine if genetic management increased genetic diversity in the experimental populations. Our analyses demonstrated the success of genetic management by documenting interpopulation hybrids, identifying no evidence for outbreeding depression as a result of contact between the genetically distinct supplemented and resident populations, and by identifying increased population-level metrics of genetic diversity in postsupplementation populations compared with presupplementation levels

SARS-CoV-2 spike antigen-specific B cell and antibody responses in pre-vaccination period COVID-19 convalescent males and females with or without post-covid condition

Background Following SARS-CoV-2 infection a significant proportion of convalescent individuals develop the post-COVID condition (PCC) that is characterized by wide spectrum of symptoms encompassing various organs. Even though the underlying pathophysiology of PCC is not known, detection of viral transcripts and antigens in tissues other than lungs raise the possibility that PCC may be a consequence of aberrant immune response to the viral antigens. To test this hypothesis, we evaluated B cell and antibody responses to the SARS-CoV-2 antigens in PCC patients who experienced mild COVID-19 disease during the pre-vaccination period of COVID-19 pandemic. Methods The study subjects included unvaccinated male and female subjects who developed PCC or not (No-PCC) after clearing RT-PCR confirmed mild COVID-19 infection. SARS-CoV-2 D614G and omicron RBD specific B cell subsets in peripheral circulation were assessed by flow cytometry. IgG, IgG3 and IgA antibody titers toward RBD, spike and nucleocapsid antigens in the plasma were evaluated by ELISA. Results The frequency of the B cells specific to D614G-RBD were comparable in convalescent groups with and without PCC in both males and females. Notably, in females with PCC, the anti-D614G RBD specific double negative (IgD-CD27-) B cells showed significant correlation with the number of symptoms at acute of infection. Anti-spike antibody responses were also higher at 3 months post-infection in females who developed PCC, but not in the male PCC group. On the other hand, the male PCC group also showed consistently high anti-RBD IgG responses compared to all other groups. Conclusions The antibody responses to the spike protein, but not the anti-RBD B cell responses diverge between convalescent males and females who develop PCC. Our findings also suggest that sex-related factors may also be involved in the development of PCC via modulating antibody responses to the SARS-CoV-2 antigens

SARS-CoV-2 spike antigen-specific B cell and antibody responses in pre-vaccination period COVID-19 convalescent males and females with or without post-covid condition

BackgroundFollowing SARS-CoV-2 infection a significant proportion of convalescent individuals develop the post-COVID condition (PCC) that is characterized by wide spectrum of symptoms encompassing various organs. Even though the underlying pathophysiology of PCC is not known, detection of viral transcripts and antigens in tissues other than lungs raise the possibility that PCC may be a consequence of aberrant immune response to the viral antigens. To test this hypothesis, we evaluated B cell and antibody responses to the SARS-CoV-2 antigens in PCC patients who experienced mild COVID-19 disease during the pre-vaccination period of COVID-19 pandemic.MethodsThe study subjects included unvaccinated male and female subjects who developed PCC or not (No-PCC) after clearing RT-PCR confirmed mild COVID-19 infection. SARS-CoV-2 D614G and omicron RBD specific B cell subsets in peripheral circulation were assessed by flow cytometry. IgG, IgG3 and IgA antibody titers toward RBD, spike and nucleocapsid antigens in the plasma were evaluated by ELISA.ResultsThe frequency of the B cells specific to D614G-RBD were comparable in convalescent groups with and without PCC in both males and females. Notably, in females with PCC, the anti-D614G RBD specific double negative (IgD-CD27-) B cells showed significant correlation with the number of symptoms at acute of infection. Anti-spike antibody responses were also higher at 3 months post-infection in females who developed PCC, but not in the male PCC group. On the other hand, the male PCC group also showed consistently high anti-RBD IgG responses compared to all other groups.ConclusionsThe antibody responses to the spike protein, but not the anti-RBD B cell responses diverge between convalescent males and females who develop PCC. Our findings also suggest that sex-related factors may also be involved in the development of PCC via modulating antibody responses to the SARS-CoV-2 antigens

Ecological immunology in a fluctuating environment: an integrative analysis of tree swallow nestling immune defense

Abstract : Evolutionary ecologists have long been interested by the link between different immune defenses and fitness. Given the importance of a proper immune defense for survival, it is important to understand how its numerous components are affected by environmental heterogeneity. Previous studies targeting this question have rarely considered more than two immune markers. In this study, we measured seven immune markers (response to phytohemagglutinin (PHA), hemolysis capacity, hemagglutination capacity, plasma bactericidal capacity, percentage of lymphocytes, percentage of heterophils, and percentage of eosinophils) in tree swallow (Tachycineta bicolor) nestlings raised in two types of agro-ecosystems of contrasted quality and over 2 years. First, we assessed the effect of environmental heterogeneity (spatial and temporal) on the strength and direction of correlations between immune measures. Second, we investigated the effect of an immune score integrating information from several immune markers on individual performance (including growth, mass at fledging and parasite burden). Both a multivariate and a pair-wise approach showed variation in relationships between immune measures across years and habitats. We also found a weak association between the integrated score of nestling immune function and individual performance, but only under certain environmental conditions. We conclude that the ecological context can strongly affect the interpretation of immune defenses in the wild. Given that spatiotemporal variations are likely to affect individual immune defenses, great caution should be used when generalizing conclusions to other study systems

Large-scale sequencing identifies multiple genes and rare variants associated with Crohn's disease susceptibility

Genome-wide association studies (GWASs) have identified hundreds of loci associated with Crohn's disease (CD). However, as with all complex diseases, robust identification of the genes dysregulated by noncoding variants typically driving GWAS discoveries has been challenging. Here, to complement GWASs and better define actionable biological targets, we analyzed sequence data from more than 30,000 patients with CD and 80,000 population controls. We directly implicate ten genes in general onset CD for the first time to our knowledge via association to coding variation, four of which lie within established CD GWAS loci. In nine instances, a single coding variant is significantly associated, and in the tenth, ATG4C, we see additionally a significantly increased burden of very rare coding variants in CD cases. In addition to reiterating the central role of innate and adaptive immune cells as well as autophagy in CD pathogenesis, these newly associated genes highlight the emerging role of mesenchymal cells in the development and maintenance of intestinal inflammation.Large-scale sequence-based analyses identify novel risk variants and susceptibility genes for Crohn's disease, and implicate mesenchymal cell-mediated intestinal homeostasis in disease etiology.Cellular mechanisms in basic and clinical gastroenterology and hepatolog