Academic literature on the topic 'Génétique d'association (GWAS)'
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Dissertations / Theses on the topic "Génétique d'association (GWAS)":
Hereil, Alexandre. "Génétique d'association et prédiction génomique de la tolérance au stress abiotique chez la tomate." Electronic Thesis or Diss., Avignon, 2024. http://www.theses.fr/2024AVIG0374.
Abiotic stresses, such as excessive salinity or nutrient deficiency, which often result in substantial yield losses, constitute significant challenges to global agriculture. These stresses are particularly detrimental in regions facing poverty, food insecurity and water scarcity. Improving the resilience of crops of high economic and nutritional value such as tomato (Solanum lycopersicum L.) to abiotic stresses could offer significant benefits, both economically and in terms of public health. The aim of this thesis is to identify the genetic components of abiotic stress tolerance in tomato and to explore the potential of genomic prediction to improve these traits. In the first chapter, we looked at the genetic architecture of nitrogen deficiency tolerance. We used a comprehensive methodology that integrates QTL mapping with multiparental population, genome-wide association study (GWAS) using a diversity panel, and RNA-seq to identify candidate genes related to nitrogen metabolism. The next two chapters are devoted to the study of salt stress tolerance. We first studied several traits associated with sodium accumulation in various plant organs and developmental stages in a GWAS panel, which enabled us to identify QTLs and a key candidate gene involved in sodium transport within the plant. In addition, we have also studied the impact of salt stress on the root metabolome, characterising metabolites differentially regulated by salt stress and identifying biomarkers of salinity tolerance. QTLs and candidate genes linked to these target metabolites have been identified. In the following two chapters, we engaged GWAS and genomic prediction in multi-environmental analyses using a diversity panel grown under a range of environmental conditions. We have identified interaction QTLs - whose allelic effects vary according to environmental conditions - and compared different GWAS methodologies. Then we have evaluated the effectiveness of various genomic prediction models for improving tolerance to abiotic stress. Our results revealed several candidate genes that require further experimental validation to elucidate their functional roles and potential applicability in breeding programmes. Preliminary results from genomic prediction models highlight the interest of using these approaches to predict tolerance to abiotic stresses, although further validation in breeding populations is required
Coulon, Audrey. "Identification et caractérisation de déterminants génétiques de la perte synaptique associée à la maladie d'Alzheimer." Electronic Thesis or Diss., Université de Lille (2022-....), 2023. https://pepite-depot.univ-lille.fr/ToutIDP/EDBSL/2023/2023ULILS058.pdf.
Alzheimer's disease (AD) is the prime cause of dementia, and synaptic loss is central to its pathophysiology. Although the most important risk factor is age, AD also has a significant genetic component, and genome-wide association studies (GWAS) have identified 76 loci encompassing hundreds of genes associated with the risk of developing the disease. Post-GWAS functional analyses are now needed to clarify the function of these genes and to identify underlying molecular mechanisms.In this context, I have developed different in vitro approaches to identify and characterize genes and variants involved in the AD-associated synaptic loss.First, I have developed a high content screening to assess the impact of each GWAS-identified AD genetic risk factor on synapse number in rat primary hippocampal neurons. I have identified several genes whose under-expression led to a significant modulation of synaptic density. Surprisingly, one of the best hits was PLCG2, whose neuronal function was unknown so far. Second, I have characterized the impact of PLCG2 gene silencing on neuronal electrical activity and AD-associated phenotypes in a model of induced pluripotent stem cells-derived neurons. Last, my work has focused on another AD genetic risk factor involved in synaptic function, the FERMT2 gene. In order to assess the functional role of the rs7143400 variant, located within FERMT2 gene 3'UTR, I have generated a cell line carrying this variant through CRISPR-Cas9 editing. This model has been used to evaluate the impact of the FERMT2 rs7143400 variant on gene expression and amyloid peptide precursor metabolism.Overall, this work helped to better understand how the PLCG2 and FERMT2 genetic risk factors influence the development of AD, giving further insights into the mechanisms involved the disease onset
Alfeghaly, Charbel. "Molecular Characterization of LncRNAs : ANRIL as a Model System." Thesis, Université de Lorraine, 2020. http://www.theses.fr/2020LORR0054.
The increased knowledge on long non-coding RNA (lncRNA ≥ 200-nts lacking obvious coding regions) and their involvement in global genome regulation push the lncRNA-disease interconnection to a promising and timely field of research. Due to flexible 2D structures and multiple protein binding sites, lncRNAs carry intrinsic features conferring a wide regulatory potential. Although lncRNAs are being extensively studied, the field is still suffering from a lack of knowledge on their structure/function relationships at the molecular and cellular levels. The team focuses on the characterization of the lncRNA named ANRIL (Antisense Non-coding RNA in the INK4 Locus). ANRIL is an ideal study model since it is associated to human diseases and is likely implicated in regulating the fine-tuning of gene expression via the recruitment of nucleoprotein complexes. Until now, ANRIL functions have only been superficially explored at the molecular level. ANRIL belongs to the 9p21 locus that is silenced by ANRIL via the recruitment of the polycomb repressor complex PRC1 and PRC2. Even though the trans-regulatory activity of ANRIL was demonstrated by previous studies, its molecular aspect needed to be refined. For instance, the coding and the non-coding genes contacted and regulated by ANRIL in a direct manner remained unknown. Also not documented were the mechanisms engaged by ANRIL to associate specifically with the genome. Our work tends to refine the so-called trans-activity by identifying the genes directly contacted and regulated by ANRIL. We identified genome-wide the chromatin occupancy of ANRIL in HEK293 by applying the ChIRP-seq approach and found that ANRIL associates with 3227 binding sites mostly composed by G/A residues. By crossing the ChIRP-seq with transcriptomic data from ANRIL knocked-down cells, we established a list of 189 genes corresponding to the primary trans-targets of ANRIL since they were both contacted and affected by the presence of ANRIL. Among them, 123 genes were found to be negatively regulated by ANRIL. In silico approaches highlighted the presence of multiple classes of transposable elements throughout ANRIL exons. In particular, 70% of the longest Exon8 was made up of ERVL element. We investigated its putative role in ANRIL's trans-activity. We showed that it is at least partially responsible for the association of ANRIL to the chromatin since deletion of Exon8 resulted in a severe reduction of ANRIL's genomic occupancy. By applying highly stringent criteria, we accurately identified 9 out of the 123 trans-target genes of ANRIL which expression specifically depends on Exon8. By further in silico, in cellulo and in vitro characterization, we showed that Exon8 contains a 42-nts sequence contributing in the recognition and subsequently in the silencing of the FIRRE and TPD52L1 genes. We brought evidences in favor of a recognition mode involving DNA/DNA:RNA triplex formation. Furthermore, we initiated the identification of ANRIL’s protein partners. By in vitro and in cellulo approaches, we identified hnRNP K as a novel partner of ANRIL. We evidenced a potential coregulatory role of ANRIL and hnRNP K on the 9p21 locus and other distal inflammatory loci. Finally, using the Stanislas Cohort, the identification of RNA and DNA biomarkers for the early diagnosis of cardiovascular and metabolic diseases has been initiated. GWAS data revealed novel associations of 9p21 locus SNPs with cardiovascular and metabolic diseases. We think that the conjugation of cellular, molecular and biochemical approaches we deployed in the study allowed to generate a clearer vision of ANRIL activity and its molecular links to diseases
Zhao, Jiantao. "Combining Association and Haplotype Studies Towards the Improvement of Fruit Quality in Tomato Multiple haplotype-based analyses provide genetic and evolutionary insights into tomato fruit weight and composition Meta-analysis of genome-wide association studies provides insights into genetic control of tomato flavor Genomic designing for climate smart tomato." Thesis, Avignon, 2019. http://www.theses.fr/2019AVIG0712.
Consumers have been complaining about tomato flavor for decades. Tomato taste is mainly influenced by sugars, acids and a diverse set of volatiles. Improving tomato flavor remains one of the main challenges for improving tomato sensory quality and consumer acceptability in modern tomato breeding. The main purpose of this thesis was to decipher the genetic and evolutionary control of tomato flavor by using high density SNPs and a diverse set of flavor-related metabolites, including sugars, acids, amino acids and volatiles. In the first part, I performed multiple haplotype-based analyses on a tomato core collection. Several approaches were used and compared to identify the genomic regions under selection. Haplotype and SNP-based Bayesian models identified 108 significant associations for 26 traits. Among these associations, some promising candidate genes were identified. I also compared marker local haplotype sharing (mLHS) with LD in determining the candidate regions. In addition, some general benefits of using haplotypes were also provided as general discussions. In the second part, I pioneered in introducing meta-analysis of genome-wide association studies using three tomato association panels. I demonstrated the efficiency of genotype imputation in increasing the genome-wide SNP coverage. Both fixed-effect and random-effect models (for those SNPs with heterogeneity I2 > 25) of meta-analysis were performed in order to control cross-study heterogeneity. A total of 305 significant loci were identified and 211 of which were new. Among them, 24 loci exhibited cis-eQTLs in a previous transcriptome-wide association study in fruit tissue. Enrichment analysis for all associations showed that up to 10 biological processes were significantly enriched and all of which were closely involved in flavor-related metabolites. A list of promising candidate genes was provided, which could be of great interest for functional validation. I also demonstrated the possibility to significantly increase the content of volatiles that positively contribute to consumer preferences while reducing unpleasant volatiles, by selection of the relevant allele combinations. Taken together, this thesis provides a comprehensive knowledge of the genetic control of tomato flavor, which will promote its improvement
Maupetit, Agathe. "Potentiel évolutif et déterminisme génétique de caractères d’agressivité et morphologiques de l’agent de la rouille du peuplier, Melampsora larici-populina." Electronic Thesis or Diss., Université de Lorraine, 2018. http://www.theses.fr/2018LORR0202.
To control plant pathogens, breeding resistant plants is the most cost-effective and ecological strategy. Quantitative resistances, which are based on complex plant mechanisms, are known to be exposed to erosion through an increase of pathogens aggressiveness. Through the study the poplar – poplar rust (Melampsora larici-populina) pathosystem, this work aims to estimate the evolutionary potential of aggressiveness and morphological traits using quantitative genetic approaches and to identify molecular bases through genome-wide association study. To estimate plasticity, heritability, and trade-offs for a set of quantitative traits, we precisely measured their variation in four contrasted pathogen populations. It appeared that spore volume is highly heritable and evolved rapidly. In planta mycelium quantity is also heritable but constant because of stabilizing selection occurring in the studied populations. Latent period, lesion size and sporulation rate exhibit low heritability, which explains the absence of evolution during the studied time period. Traits involved in the sporulating function seem to be the most plastic ones along a leaf maturity gradient. However, the lack of evidence of trade-offs did not allow us to identify aggressiveness traits that would be the best targets for the construction of durable resistance in poplar. No genetic underpinning has been found for quantitative traits, but we have identified a potential avirulence locus (Avr7), opening the way for its functional characterization
Nguyen, Le Khanh. "Caractérisation fonctionnelle d'un QTL de développement racinaire détecté par GWAS dans une collection de variétés vietnamiennes de riz." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG044.
Rice is one of the most important cereals worldwide. In Vietnam, rice is also known as a key agronomic product for exportation. However, drought stresses threaten rice production with an increasing frequency and for longer periods. Crown roots are a major component of rice root system and play a crucial role in maintaining yield under drought. The number of crown roots (NCR) impacts on root biomass and determines the ability of a plant to acquire soil resources. qNCR11, a QTL for NCR located on chromosome 11, was detected in a previous genome-wide association study using a Vietnamese rice panel. qNCR11 was validated to have a slight effect on NCR by QTL mapping using a biparental population in this study. To determine the genes underlying qNCR11 and governing crown root initiation and development, whole genome sequencing and expression study were performed. Two candidate genes, NCR2 (NBS-LRR) and NCR3 (OsbHLH014) were identified. NCR2 carried a non-synonymous SNP inside its ORF, causing a premature stop-codon that correlates with the high NCR trait; NCR3 was less expressed in stem bases of the high NCR haplotype plants relative to the low NCR haplotype plants. Mutations in these genes were obtained using the CRISPR/Cas9 system and the phenotyping of the obtained lines is on-going. The minor-effect qNCR11 could be useful for breeders to generate rice varieties with increased or decreased NCR for different target agro-systems, in order to enhance water extraction under drought stress
Milet, Jacqueline. "Étude de la composante génétique de la variabilité des infections palustres simples : Approche génome entier dans deux cohortes de jeunes enfants au Bénin First Genome-Wide Association Study of Non-Severe Malaria in Two Birth Cohorts in Benin Mixed logistic regression in Genome-Wide Association Studies." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASR013.
In spite of numerous prevention and control efforts in recent years, malaria remains a major global public health problem with nearly half a million deaths per year (405,000 in 2018). The key role played by genetic factors of the host in the susceptibility and severity of the disease is is admitted nowadays. However, the molecular basis of susceptibility / resistance to malaria has not been elucidated to date. Over the past decade, research efforts to identify genes involved in malaria susceptibility have focused on severe malaria, with several genome-wide association studies (GWAS) published. This manuscript concerns the extension of this approach to uncomplicated forms of malaria, through the genome wide association study of two birth cohorts in South Benin (800 children), followed for 18-24 months by UMR261 (MERIT IRD / University of Paris).In the first part, we present the results of the first GWAS performed on simple forms of malaria in these two cohorts. The association was tested with the recurrence of malaria attacks and the recurrence of all infections (including malaria attacks and asymptomatic infections) taking into account an environmental risk estimated at the individual level. It highlights several strong association signals, linked to genes whose biological function is relevant for malaria (in particular PTPRT, MYLK4, UROC1 and ACER3). The high genetic diversity within African populations has made it necessary to take into account the potential confounding effect of population structure. In this study we proceeded with a two-step strategy as the Cox mixed model, used for the analysis of longitudinal data, is not applicable to the whole genome due to computational burden. In a first step, an analysis was performed with a Cox mixed model to build an "individual effect" fitted on the covariates, then a linear mixed model were used to test the association with genome polymorphisms. This led us to focus more generally on non-linear mixed models. Two methods allowing the estimation of the effect of polymorphisms with the mixed logistic model are proposed, which may in the future be generalized to other models, including the Cox model.In a final part, malaria having been one of the strongest selection pressures that man has known in recent history, we explore the possibility of exploiting natural selection information to increase the power of analysis, and improve the detection of association signals. The analysis of recent positive selection signals were performed using several genome-scan methods focusing on patterns of long-range haplotype homozygosity (iHS, nsL and XP-EHH). This analysis revealed several chromosomic region of potential interest, where the signals of association and selection co-localized but confirms also the difficulty of highlighting the selection signals linked to malaria with tools currently available
Leforestier, Diane. "Localisation de régions du génome du pommier contrôlant la variation de caractères de qualité du fruit et de résistance aux maladies : signatures de sélection et génétique d'association." Thesis, Angers, 2015. http://www.theses.fr/2015ANGE0051/document.
Since apple domestication, humans have progressively selected improved varieties, especially for traits linked with fruit quality, productivity or resistance to pathogens. The genetic bases underlying these traits have been explored thanks to genetic mapping in F1 segregating populations that only allows the study of a small part of the available genetic diversity. The aim of this work was to analyze the genetic bases of fruit quality and disease resistance against apple scab and fire blight, in collections of old apple varieties representing a much larger diversity. Genotyping of core collections was performed either with arrays of 8k and 480k SNPs or by resequencing of chosen genes. Signs of genetic differentiation were identified between cider and dessert apples and were partially linked to the polyphenols pathway. After studying linkage disequilibrium, both on a large and a small scale, an association genetics approach allowed the identification of genomic regions associated with the variation of several fruit quality traits. Especially, the top of linkage group 16 was found to be linked with acidity (locus Ma), firmness, juiciness and bitterness (LAR gene). Concerning the resistance of apple to fire blight, a region containing a homolog of the NPR1 gene (defense activator) was identified. This thesis allowed the refining of the putative localization of previously identified QTLs and the identification of new genetic resources that could be useful in future selection programs using marker assisted selection
Maupetit, Agathe. "Potentiel évolutif et déterminisme génétique de caractères d’agressivité et morphologiques de l’agent de la rouille du peuplier, Melampsora larici-populina." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0202/document.
To control plant pathogens, breeding resistant plants is the most cost-effective and ecological strategy. Quantitative resistances, which are based on complex plant mechanisms, are known to be exposed to erosion through an increase of pathogens aggressiveness. Through the study the poplar – poplar rust (Melampsora larici-populina) pathosystem, this work aims to estimate the evolutionary potential of aggressiveness and morphological traits using quantitative genetic approaches and to identify molecular bases through genome-wide association study. To estimate plasticity, heritability, and trade-offs for a set of quantitative traits, we precisely measured their variation in four contrasted pathogen populations. It appeared that spore volume is highly heritable and evolved rapidly. In planta mycelium quantity is also heritable but constant because of stabilizing selection occurring in the studied populations. Latent period, lesion size and sporulation rate exhibit low heritability, which explains the absence of evolution during the studied time period. Traits involved in the sporulating function seem to be the most plastic ones along a leaf maturity gradient. However, the lack of evidence of trade-offs did not allow us to identify aggressiveness traits that would be the best targets for the construction of durable resistance in poplar. No genetic underpinning has been found for quantitative traits, but we have identified a potential avirulence locus (Avr7), opening the way for its functional characterization
Rio, Simon. "Contributions to genomic selection and association mapping in structured and admixed populations : application to maize." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS097.
The advent of molecular markers (SNPs) has revolutionized quantitative genetics methods by enabling the identification of regions involved in the genetic determinism of traits (QTLs) thanks to association studies (GWAS), or the prediction of the performance of individuals using genomic information (GS). The stratification of populations into genetic groups is common in animal and plant breeding. This structure can impact GWAS and GS methods through group differences in QTL allele frequencies and effects, as well as in linkage disequilibrium (LD) between SNP and QTL.During this thesis, two maize diversity panels were used, presenting different levels of structuration: the "Amaizing Dent" panel representing the diversity of dent lines used in Europe and the "Flint-Dent" panel including dent, flint and admixed lines between these two groups.In GS, the impact of genetic structure on genomic prediction accuracy was evaluated in the first panel for productivity and phenology traits. This study highlighted the interest of a training population (TS) whose constitution in terms of genetic groups is similar to that of the population to be predicted. Assembling the different groups within a multi-group TS appears as an effective solution to predict a broad spectrum of genetic diversity. A priori indicators of genomic prediction accuracy, based on the coefficient of determination, were also evaluated and highlighted a variable efficiency depending on the group and the trait.A new GWAS methodology was then developed to study the heterogeneity of the allele effects captured by SNPs depending on the group. The integration of admixed individuals to such analyses allows to disentangle the factors causing the heterogeneity of allele effects across groups: local genomic difference (related to LD or group-specific mutation) or epistatic interactions between the QTL and the genetic background. This methodology was applied to the "Flint-Dent" panel for flowering time. QTLs have been detected as presenting group-specific effects interacting or not with the genetic background. QTLs with an original profile have been highlighted, including known loci such as Vgt1, Vgt2 or Vgt3. Significant directional epistasis has also been demonstrated using admixed individuals and supported the existence of epistatic interactions with the genetic background for this trait.Based on the existence of such heterogeneity of allele effects, we have developed two genomic prediction models named Multi-group Admixed GBLUP (MAGBLUP). Both model group-specific QTL effects and are suited to the prediction of admixed individuals. The first allows the identification the additional genetic variance created by the admixture (segregation variance), while the second allows the evaluations of the degree of conservation of SNP allele effects across groups. These two models showed a certain interest compared to standard models to predict simulated traits, but it was more limited on real traits.Finally, the interest of admixed individuals in multi-group TS was evaluated using the second panel. Although their interest has been clearly demonstrated for simulated traits, more variable results have been observed with the real traits, which can be explained by the presence of interactions with the genetic background.The new methods and the use of admixed individuals open interesting lines of research for quantitative genetics studies in structured population