Looking for signatures of sex-specific demography and local adaptation on the X chromosome

A genome-wide study of X chromosome genetic diversity in human populations shows the impact of social organization and local adaptation

Genetic diversity and the emergence of ethnic groups in Central Asia

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Elevated rates of horizontal gene transfer in the industrialized human microbiome

Industrialization has impacted the human gut ecosystem, resulting in altered microbiome composition and diversity. Whether bacterial genomes may also adapt to the industrialization of their host populations remains largely unexplored. Here, we investigate the extent to which the rates and targets of horizontal gene transfer (HGT) vary across thousands of bacterial strains from 15 human populations spanning a range of industrialization. We show that HGTs have accumulated in the microbiome over recent host generations and that HGT occurs at high frequency within individuals. Comparison across human populations reveals that industrialized lifestyles are associated with higher HGT rates and that the functions of HGTs are related to the level of host industrialization. Our results suggest that gut bacteria continuously acquire new functionality based on host lifestyle and that high rates of HGT may be a recent development in human history linked to industrialization.Peer reviewe

Mode de vie et diversité génétique dans les populations humaines d'Asie Centrale

Cette thèse a pour objectif de s interroger sur l influence du mode de vie sur la diversité génétique humaine. Nous avons pour cela étudié plusieurs ethnies d Asie Centrale qui diffèrent de par leur organisation sociale et leur mode de subsistance. Nous avons d abord comparé la diversité génétique de populations patrilinéaires et cognatiques (populations se définissant par leur ascendance paternelle ou indifféremment par les deux sexes, respectivement). Cette étude, basée sur les autosomes et le chromosome X, nous a permis de montrer que les hommes ont un effectif efficace et un taux de migration réduits par rapport aux femmes chez les patrilinéaires, mais non chez les cognatiques. Ensuite, nous avons testé si les éleveurs et les agriculteurs ont subi différentes pressions de sélection liées à l alimentation. Pour le gène de la lactase (digestion du lactose) et de l AGXT (facilitant la digestion de la viande), nous n avons pas trouvé de différence de diversité génétique entre populations. Cependant, nous avons montré que les éleveurs (représentés par les Kirghizes) présentent près de deux fois plus de résistance à l insuline, phénotype proposé comme une adaptation aux faibles quantités de glucides dans l alimentation, que les agriculteurs (représentés par les Tadjiks). Nous avons également mis en évidence des signatures d adaptation locale entre éleveurs et agriculteurs sur certains gènes associés à la résistance à l insuline. Ainsi, ces populations semblent s être adaptées à des régimes alimentaires différents. Cette thèse conforte donc l hypothèse d une influence des facteurs culturels sur l évolution de la diversité génétique des populations humaines.PARIS-BIUP (751062107) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Modelling the spatiotemporal spread of beneficial alleles using ancient genomes

Ancient genome sequencing technologies now provide the opportunity to study natural selection in unprecedented detail. Rather than making inferences from indirect footprints left by selection in present-day genomes, we can directly observe whether a given allele was present or absent in a particular region of the world at almost any period of human history within the last 10,000 years. Methods for studying selection using ancient genomes often rely on partitioning individuals into discrete time periods or regions of the world. However, a complete understanding of natural selection requires more nuanced statistical methods which can explicitly model allele frequency changes in a continuum across space and time. Here we introduce a method for inferring the spread of a beneficial allele across a landscape using two-dimensional partial differential equations. Unlike previous approaches, our framework can handle time-stamped ancient samples, as well as genotype likelihoods and pseudohaploid sequences from low-coverage genomes. We apply the method to a panel of published ancient West Eurasian genomes to produce dynamic maps showcasing the inferred spread of candidate beneficial alleles over time and space. We also provide estimates for the strength of selection and diffusion rate for each of these alleles. Finally, we highlight possible avenues of improvement for accurately tracing the spread of beneficial alleles in more complex scenarios

Changes in the Human Gut Microbiota Associated With Colonization by Blastocystis sp. and Entamoeba spp. in Non-Industrialized Populations

International audienceHuman gut microbial communities are mainly composed of bacteria, but also include fungi, viruses, archaea, and protozoa, whose role in the gut ecosystem has only recently begun to be recognized. For example, humans colonized by Blastocystis (a gut protozoan with controversial pathogenicity) host a more diverse bacterial microbiota than individuals not carrying it, suggesting that its presence may be beneficial for the host. In parallel, the presence of non-pathogenic Entamoeba spp. has been associated with an increased diversity and compositional shifts in the bacterial microbiota of healthy rural individuals in Cameroon. However, Entamoeba and Blastocystis, the two most prevalent human gut protozoa, have never been studied in the same individuals, preventing the study of their interaction. As Blastocystis is one of the few gut protozoa commonly found in industrialized populations, which are otherwise mostly devoid of gut eukaryotes, we need to focus on rural "traditional" populations, who harbor a higher diversity of gut eukaryotes (whether pathogenic or commensal) in order to study protozoa interactions in the gut ecosystem. To this end, we profiled the gut bacterial microbiota of 134 healthy Cameroonian adults using 16S rRNA gene amplicon sequencing data. Entamoeba and Blastocystis presence and co-occurrence pattern in the same individuals were determined using metagenomic shotgun data. We found that, when taking into account both protozoa jointly, Blastocystis was associated with both a higher richness and a higher evenness of the gut bacterial microbiota, while Entamoeba was associated only with a higher richness. We demonstrated a cumulative influence of these protozoa on bacterial microbiome diversity. Furthermore, while the abundance of several common taxa (for example, Ruminococcaceae, Coprococcus and Butyrivibrio) varied according to Blastocystis colonization, only a single Bacteroides amplicon sequence variant was found to be differentially abundant between Entamoeba-negative and Entamoeba-positive samples. Given the specific signature of each protozoan on the gut microbiota and the seemingly stronger association for Blastocystis, our results suggest that Blastocystis and Entamoeba interact with gut bacteria each in its own way, but experimental studies are needed to explore the precise mechanisms of these interactions

Étude paléoparasitologique des latrines du Pavillon royal et du 3e Pavillon du Levant du Château de Marly

Parasitological analyses of the third Pavilion du Levant and the Royal Pavilion are in continuity with those carried out by Françoise Bouchet on the latrines of the second Pavilion du Levant, published in 1998. The initial objective is to confirm the excremental nature of these different deposits and then to reconstitute the health status and microbial population of the intestinal flora of the subjects of Louis XIV’s court. To answer this question, a large multidisciplinary scientific team intervened to carry out the various parasitological and molecular analyses. This first report sets out the means put in place as well as the results relating to optical microscopy, toxicological and metagenomic data

Close inbreeding and low genetic diversity in Inner Asian human populations despite geographical exogamy

When closely related individuals mate, they produce inbred offspring, which often have lower fitness than outbred ones. Geographical exogamy, by favouring matings between distant individuals, is thought to be an inbreeding avoidance mechanism; however, no data has clearly tested this prediction. Here, we took advantage of the diversity of matrimonial systems in humans to explore the impact of geographical exogamy on genetic diversity and inbreeding. We collected ethno-demographic data for 1,344 individuals in 16 populations from two Inner Asian cultural groups with contrasting dispersal behaviours (Turko-Mongols and Indo-Iranians) and genotyped genome-wide single nucleotide polymorphisms in 503 individuals. We estimated the population exogamy rate and confirmed the expected dispersal differences: Turko-Mongols are geographically more exogamous than Indo-Iranians. Unexpectedly, across populations, exogamy patterns correlated neither with the proportion of inbred individuals nor with their genetic diversity. Even more surprisingly, among Turko-Mongols, descendants from exogamous couples were significantly more inbred than descendants from endogamous couples, except for large distances (>40 km). Overall, 37% of the descendants from exogamous couples were closely inbred. This suggests that in Inner Asia, geographical exogamy is neither efficient in increasing genetic diversity nor in avoiding inbreeding, which might be due to kinship endogamy despite the occurrence of dispersal

Lactase Persistence in Central Asia: Phenotype, Genotype, and Evolution

The aim of the present study is to document the evolution of the lactase persistence trait in Central Asia, a geographical area that is thought to have been a region of long-term pastoralism. Several ethnic groups co-exist in this area: Indo-Iranian speakers who are traditionally agriculturist (Tajik) and Turkic speakers who used to be nomadic herders (Kazakh, Karakalpak, Kyrgyz, Turkmen). It was recently demonstrated that horse milking practice existed in the Botai culture of Kazakhstan as early as 5,500 BP (Outram et al. 2009). However, the frequency of the lactase persistence trait and its genetic basis in Central Asian populations remain largely unknown. We propose here the first genotype-phenotype study of lactase persistence in Central Asia based on 183 individuals, as well as the estimation of the time of expansion of the lactasepersistence associated polymorphism. Our results show a remarkable geneticphenotypic correlation, with the causal polymorphism being the same than in Europe (-13.910C T, rs4988235). The lactase persistence trait is at low frequency in these populations: between 25% and 32% in the Kazakh population (traditionally herders), according to phenotype used, and between 11% and 30% in the Tajiko-Uzbek population (agriculturalists). The difference in lactase persistence between populations, even if small, is significant when using individuals concordant for both excretion of breath hydrogen and the lactose tolerance blood glucose test phenotypes (P 0.018, 25% for Kazakh vs. 11% for Tajiko-Uzbeks), and the difference in frequency of the 13.910*T allele is almost significant (P 0.06, 30% for Kazakhs vs. 19% for Tajiko-Uzbeks). Using the surrounding haplotype, we estimate a date of expansion of the T allele around 6,000–12,000 yrs ago, which is consistent with archaeological records for the emergence of agropastoralism and pastoralism in Central Asia