35 research outputs found
Human Population Differentiation Is Strongly Correlated with Local Recombination Rate
Allele frequency differences across populations can provide valuable information both for studying population structure and for identifying loci that have been targets of natural selection. Here, we examine the relationship between recombination rate and population differentiation in humans by analyzing two uniformly-ascertained, whole-genome data sets. We find that population differentiation as assessed by inter-continental FST shows negative correlation with recombination rate, with FST reduced by 10% in the tenth of the genome with the highest recombination rate compared with the tenth of the genome with the lowest recombination rate (P≪10−12). This pattern cannot be explained by the mutagenic properties of recombination and instead must reflect the impact of selection in the last 100,000 years since human continental populations split. The correlation between recombination rate and FST has a qualitatively different relationship for FST between African and non-African populations and for FST between European and East Asian populations, suggesting varying levels or types of selection in different epochs of human history
On the Origin and Spread of the Scab Disease of Apple: Out of Central Asia
Background Venturia inaequalis is an ascomycete fungus responsible for apple scab, a disease that has invaded almost all apple growing regions worldwide, with the corresponding adverse effects on apple production. Monitoring and predicting the effectiveness of intervention strategies require knowledge of the origin, introduction pathways, and population biology of pathogen populations. Analysis of the variation of genetic markers using the inferential framework of population genetics offers the potential to retrieve this information. Methodology/Principal Findings Here, we present a population genetic analysis of microsatellite variation in 1,273 strains of V. inaequalis representing 28 orchard samples from seven regions in five continents. Analysis of molecular variance revealed that most of the variation (88%) was distributed within localities, which is consistent with extensive historical migrations of the fungus among and within regions. Despite this shallow population structure, clustering analyses partitioned the data set into separate groups corresponding roughly to geography, indicating that each region hosts a distinct population of the fungus. Comparison of the levels of variability among populations, along with coalescent analyses of migration models and estimates of genetic distances, was consistent with a scenario in which the fungus emerged in Central Asia, where apple was domesticated, before its introduction into Europe and, more recently, into other continents with the expansion of apple growing. Across the novel range, levels of variability pointed to multiple introductions and all populations displayed signatures of significant post-introduction increases in population size. Most populations exhibited high genotypic diversity and random association of alleles across loci, indicating recombination both in native and introduced areas. Conclusions/Significance Venturia inaequalis is a model of invasive phytopathogenic fungus that has now reached the ultimate stage of the invasion process with a broad geographic distribution and well-established populations displaying high genetic variability, regular sexual reproduction, and demographic expansion.Contexte Venturia inaequalis est un champignon ascomycete responsable de la tavelure du pommier, une maladie qui a envahi presque toutes les régions du monde où le pommier est cultivé posant ainsi de graves problèmes en production. Prévenir et enrayer efficacement la réussite d’un tel succès invasif nécessite des connaissances approfondies sur l’origine, les voies d’introduction, la biologie et la génétique de ces populations invasives. En utilisant le potentiel d’inférence de la génétique des populations, l’analyse de la variation de marqueurs génétiques offre la possibilité d’accéder à ces informations. Méthodologie et Principaux résultats Ici nous présentons l’analyse de données microsatellites obtenues pour 1273 souches de V. inaequalis provenant de 28 vergers prélevées dans 7 régions sur les 5 continents. L’analyse de la variance moléculaire révèle que 88% de la variation se retrouve dans les vergers échantillonnés, ce qui est compatible avec d’importantes migrations historiques du champignon entre et à l’intérieur même des régions. Malgré cette très faible structuration des populations, les différentes analyses de clustering mettent en évidence un partage des populations en groupes séparés correspondant à leur origine géographique, montrant ainsi que chaque région héberge une population distincte du champignon. Ensemble, les résultats obtenus sur la comparaison du niveau de variabilité entre populations, les analyses de coalescence et les modèles de migration testés plaident en faveur d’un scénario dans lequel le champignon aurait émergé d’Asie Centrale, où le pommier a été domestiqué, avant d’être introduit en Europe puis plus récemment dans les autres continents suite à l’expansion de la culture du pommier. Les niveaux de variabilité indiquent que ces territoires ont subi des introductions multiples et que les populations portent toutes des signatures révélant de fortes expansions démographiques après leur introduction. Enfin, la forte diversité génotypique des populations et l’association aléatoire des allèles entre loci suggèrent que le champignon présente une reproduction sexuée régulière à la fois dans les régions où il a été introduit et dans sa région native. Conclusion et Portée. Venturia inaequalis est un modèle de champignons phytopathogène invasif qui a maintenant atteint le stade ultime du processus invasif, c’est à dire une très large distribution géographique par des populations bien établies montrant une grande diversité génétique, une reproduction sexuée régulière et une histoire d’expansion démographique
Depression rather than liver impairment reduces quality of life in patients with hepatitis C
The REP-b (removal of endometrial pathologies-basket) in-office hysteroscopy
The aim of this study was to assess the safety, effectiveness and advantages of a new surgical technique for the extraction of endometrial polyps after in-office hysteroscopic polipectomy. Between November 2009 and September 2013, 140 pre- and post-menopausal women with a sonographic diagnosis of endometrial polyps underwent polypectomy in-office hysteroscopy, followed by lesion removal using classical surgical instruments or the new REP-b technique. A total of 70 women underwent endometrial polyp removal using the new surgical technique REP-b (GROUP A), and 70 women received endometrial polyp removal using classical surgical instruments (GROUP B). The extraction time Tr, calculated as the time from the introduction of the basket into the operative hysteroscopic sheath to the complete removal of the previously sectioned polyp, in GROUP A (REP-b technique) was significantly lower compared with GROUP B (control group). The median Tr for GROUP A was 29.50 s versus the median Tr for GROUP B of 54.00 s (P<0.01). The use of the REP-b technique improves the outcome of the operation and reduces the extraction time for the removal of endocavitary uterine lesions