Anthropologie, Génétique des Populations & Pharmacogénomique

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Many species are threatened with extinction as their population sizes decrease with changing environments or face novel pathogenic threats. A reduction of genetic diversity at major histocompatibility complex (MHC) genes may have dramatic effects on populations' survival, as these genes play a key role in adaptive immunity. This might be the case for chimpanzees, the MHC genes of which reveal signatures of an ancient selective sweep likely due to a viral epidemic that reduced their population size a few million years ago. To better assess how this past event affected MHC variation in chimpanzees compared to humans, we analysed several indexes of genetic diversity and linkage disequilibrium across seven MHC genes on four cohorts of chimpanzees and we compared them to those estimated at orthologous HLA genes in a large set of human populations.

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INTRODUCTION AND OBJECTIVE: Cytochrome P450 enzymes are the major drug-metabolizing enzymes in humans and the importance of drug transport proteins, in particular P-glycoprotein, in the variability of drug response has also been highlighted. Activity of cytochrome P450 enzymes and P-glycoprotein can vary widely between individuals and genotyping and/or phenotyping can help assess their activity. Several phenotyping cocktails have been developed. The Geneva cocktail is composed of a specific probe for six different cytochrome P450 enzymes and one for P-glycoprotein and was used in the context of a research aiming at exploring genotypes and phenotypes in distinct human populations (NCT02789527). The aim of the present study is to solely report the safety results of the Geneva cocktail in the healthy volunteers of these populations.

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Human population history in the Holocene was profoundly impacted by changes in lifestyle following the invention and adoption of food-production practices. These changes triggered significant increases in population sizes and expansions over large distances. Here we investigate the population history of the Fulani, a pastoral population extending throughout the African Sahel/Savannah belt.

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Among the many genes involved in the metabolism of therapeutic drugs, human arylamine N-acetyltransferases (NATs) genes have been extensively studied, due to their medical importance both in pharmacogenetics and disease epidemiology. One member of this small gene family, NAT2, is established as the locus of the classic human acetylation polymorphism in drug metabolism. Current hypotheses hold that selective processes favoring haplotypes conferring lower NAT2 activity have been operating in modern humans' recent history as an adaptation to local chemical and dietary environments. To shed new light on such hypotheses, we investigated the genetic diversity of the three members of the NAT gene family in seven hominid species, including modern humans, Neanderthals and Denisovans. Little polymorphism sharing was found among hominids, yet all species displayed high NAT diversity, but distributed in an opposite fashion in chimpanzees and bonobos (Pan genus) compared to modern humans, with higher diversity in Pan species at NAT1 and lower at NAT2, while the reverse is observed in humans. This pattern was also reflected in the results returned by selective neutrality tests, which suggest, in agreement with the predicted functional impact of mutations detected in non-human primates, stronger directional selection, presumably purifying selection, at NAT1 in modern humans, and at NAT2 in chimpanzees. Overall, the results point to the evolution of divergent functions of these highly homologous genes in the different primate species, possibly related to their specific chemical/dietary environment (exposome) and we hypothesize that this is likely linked to the emergence of controlled fire use in the human lineage.

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From a biogeographic perspective Africa is subdivided into distinct horizontal belts. Human populations living along the Sahel/Savannah belt south of the Sahara Desert have often been overshadowed by extensive studies focusing on other African populations such as hunter-gatherers or Bantu in particular. However, the Sahel together with the savannah bordering it in the south, is a challenging region where people had and still have to cope with harsh climatic conditions and show resilient behaviours. Besides exponentially growing urban populations, several local groups leading various lifestyles and speaking languages belonging to three main linguistic families still live in rural localities across that region today. Thanks to several years of consistent population sampling throughout this area, the genetic history of the African Sahelian populations has been largely reconstructed and a deeper knowledge has been acquired regarding their adaptation to peculiar environments and/or subsistence modes. Distinct exposures to pathogens - in particular malaria - likely contributed to their genetic differentiation for HLA genes. In addition, although food-producing strategies spread within the Sahel/Savannah belt relatively recently, during the last five millennia according to recent archaeological and archaeobotanical studies, remarkable amounts of genetic differences are also observed between sedentary farmers and more mobile pastoralists at multiple neutral and selected loci, reflecting both demographic effects and genetic adaptations to distinct cultural traits, such as dietary habits.

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Thanks to the ability to digest lactose, Arabian nomads had become less dependent upon their sedentary neighbors and some of these populations spread to Africa. When and by which route they migrated to their current locations have previously been addressed only by historical and archaeological data.

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Genetic and archaeological research supports the theory that Arabia was the first region traversed by modern humans as they left Africa and dispersed throughout Eurasia. However, the role of Arabia from the initial migration out of Africa until more recent times is still unclear.

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Dietary changes associated to shifts in subsistence strategies during human evolution may have induced new selective pressures on phenotypes, as currently held for lactase persistence. Similar hypotheses exist for arylamine N-acetyltransferase 2 (NAT2) mediated acetylation capacity, a well-known pharmacogenetic trait with wide inter-individual variation explained by polymorphisms in the NAT2 gene. The environmental causative factor (if any) driving its evolution is as yet unknown, but significant differences in prevalence of acetylation phenotypes are found between hunter-gatherer and food-producing populations, both in sub-Saharan Africa and worldwide, and between agriculturalists and pastoralists in Central Asia. These two subsistence strategies also prevail among sympatric populations of the African Sahel, but knowledge on NAT2 variation among African pastoral nomads was up to now very scarce. Here we addressed the hypothesis of different selective pressures associated to the agriculturalist or pastoralist lifestyles having acted on the evolution of NAT2 by sequencing the gene in 287 individuals from five pastoralist and one agriculturalist Sahelian populations.

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Several demographic events have been postulated to explain the contemporaneous structure of European genetic diversity. First, an initial settlement of the continent by anatomically modern humans; second, the re-settlement of northern latitudes after the Last Glacial Maximum; third, the demic diffusion of Neolithic farmers from the Near East; and, fourth, several historical events such as the Slavic migration.

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Much of the data resolution of the haploid non-recombining Y chromosome (NRY) haplogroup O in East Asia are still rudimentary and could be an explanatory factor for current debates on the settlement history of Island Southeast Asia (ISEA). Here, 81 slowly evolving markers (mostly SNPs) and 17 Y-chromosomal short tandem repeats were used to achieve higher level molecular resolution. Our aim is to investigate if the distribution of NRY DNA variation in Taiwan and ISEA is consistent with a single pre-Neolithic expansion scenario from Southeast China to all ISEA, or if it better fits an expansion model from Taiwan (the OOT model), or whether a more complex history of settlement and dispersals throughout ISEA should be envisioned.

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Persons infected with human immunodeficiency virus (HIV) have increased rates of coronary artery disease (CAD). The relative contribution of genetic background, HIV-related factors, antiretroviral medications, and traditional risk factors to CAD has not been fully evaluated in the setting of HIV infection.

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The arylamine N-acetyltransferases (NATs) are a unique family of enzymes widely distributed in nature that play a crucial role in the detoxification of aromatic amine xenobiotics. Considering the temporal changes in the levels and toxicity of environmentally available chemicals, the metabolic function of NATs is likely to be under adaptive evolution to broaden or change substrate specificity over time, making NATs a promising subject for evolutionary analyses. In this study, we trace the molecular evolutionary history of the NAT gene family during the last ~450 million years of vertebrate evolution and define the likely role of gene duplication, gene conversion and positive selection in the evolutionary dynamics of this family.

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The forensic genetics field is generating extensive population data on polymorphism of short tandem repeats (STR) markers in globally distributed samples. In this study we explored and quantified the informative power of these datasets to address issues related to human evolution and diversity, by using two online resources: an allele frequency dataset representing 141 populations summing up to almost 26 thousand individuals; a genotype dataset consisting of 42 populations and more than 11 thousand individuals. We show that the genetic relationships between populations based on forensic STRs are best explained by geography, as observed when analysing other worldwide datasets generated specifically to study human diversity. However, the global level of genetic differentiation between populations (as measured by a fixation index) is about half the value estimated with those other datasets, which contain a much higher number of markers but much less individuals. We suggest that the main factor explaining this difference is an ascertainment bias in forensics data resulting from the choice of markers for individual identification. We show that this choice results in average low variance of heterozygosity across world regions, and hence in low differentiation among populations. Thus, the forensic genetic markers currently produced for the purpose of individual assignment and identification allow the detection of the patterns of neutral genetic structure that characterize the human population but they do underestimate the levels of this genetic structure compared to the datasets of STRs (or other kinds of markers) generated specifically to study the diversity of human populations.

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Arylamine N-acetyltransferase 2 (NAT2) is involved in human physiological responses to a variety of xenobiotic compounds, including common therapeutic drugs and exogenous chemicals present in the diet and the environment. Many questions remain about the evolutionary mechanisms that have led to the high prevalence of slow acetylators in the human species. Evidence from recent surveys of NAT2 gene variation suggests that NAT2 slow-causing variants might have become targets of positive selection as a consequence of the shift in modes of subsistence and lifestyle in human populations in the last 10,000 years. We aimed to test more extensively the hypothesis that slow acetylation prevalence in humans is related to the subsistence strategy adopted by the past populations. To this end, published frequency data on the most relevant genetic variants of NAT2 were collected from 128 population samples (14,679 individuals) representing different subsistence modes and dietary habits, allowing a thorough analysis at both a worldwide and continent scale. A significantly higher prevalence of the slow acetylation phenotype was observed in populations practicing farming (45.4%) and herding (48.2%) as compared to populations mostly relying on hunting and gathering (22.4%) (P = 0.0007). This was closely mirrored by the frequency of the slow 590A variant that was found to occur at a three-fold higher frequency in food producers (25%) as compared to hunter-gatherers (8%). These findings are consistent with the hypothesis that the Neolithic transition to subsistence economies based on agricultural and pastoral resources modified the selective regime affecting the NAT2 acetylation pathway. Furthermore, the vast amount of data collected enabled us to provide a comprehensive and up-to-date description of NAT2 worldwide genetic diversity, thus building up a useful resource of frequency data for further studies interested in epidemiological or anthropological research questions involving NAT2.

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The potential for mitochondrial (mt) DNA mutation accumulation during antiretroviral therapy (ART), and preferential accumulation in patients with lipoatrophy compared with control participants, remains controversial. We sequenced the entire mitochondrial genome, both before ART and after ART exposure, in 29 human immunodeficiency virus (HIV)-infected Swiss HIV Cohort Study participants initiating a first-line thymidine analogue-containing ART regimen. No accumulation of mtDNA mutations or deletions was detected in 13 participants who developed lipoatrophy or in 16 control participants after significant and comparable ART exposure (median duration, 3.3 and 3.7 years, respectively). In HIV-infected persons, the development of lipoatrophy is unlikely to be associated with accumulation of mtDNA mutations detectable in peripheral blood.

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The Strait of Gibraltar is a crucial area in the settlement history of modern humans because it represents a possible connection between Africa and Europe. So far, genetic data were inconclusive about the fact that this strait constitutes a barrier to gene flow, as previous results were highly variable depending on the genetic locus studied. The present study evaluates the impact of the Gibraltar region in reducing gene flow between populations from North-Western Africa and South-Western Europe, by comparing formally various genetic loci. First, we compute several statistics of population differentiation. Then, we use an original simulation approach in order to infer the most probable evolutionary scenario for the settlement of the area, taking into account the effects of both demography and natural selection at some loci.

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The Afro-Asiatic and Nilo-Saharan language families come into contact in Western Ethiopia. Ethnic diversity is particularly high in the South, where the Nilo-Saharan Nyangatom and the Afro-Asiatic Daasanach dwell. Despite their linguistic differentiation, both populations rely on a similar agripastoralist mode of subsistence. Analysis of mitochondrial DNA extracted from Nyangatom and Daasanach archival sera revealed high levels of diversity, with most sequences belonging to the L haplogroups, the basal branches of the mitochondrial phylogeny. However, in sharp contrast with other Ethiopian populations, only 5% of the Nyangatom and Daasanach sequences belong to haplogroups M and N. The Nyangatom and Daasanach were found to be significantly differentiated, while each of them displays close affinities with some Tanzanian populations. The strong genetic structure found over East Africa was neither associated with geography nor with language, a result confirmed by the analysis of 6711 HVS-I sequences of 136 populations mainly from Africa. Processes of migration, language shift and group absorption are documented by linguists and ethnographers for the Nyangatom and Daasanach, thus pointing to the probably transient and plastic nature of these ethnic groups. These processes, associated with periods of isolation, could explain the high diversity and strong genetic structure found in East Africa.

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Genetic studies have been underway on Arabian Peninsula populations because of their pivotal geographic location for population migration and times of occurrence. To assist in better understanding population dynamics in this region, evidence is presented herein on local population structure in the Arabian Peninsula, based on Y-STR characterisation in four Arabian samples and its comparison in a broad geographical scale. Our results demonstrate that geography played an important role in shaping the genetic structure of the region around the Near-East. Populations are grouped regionally but none of these groups is significantly differentiated from others and all groups merge in the Near-East, in keeping with this important migration corridor for the human species. Focusing on the Arabian Peninsula, we show that Dubai and Oman share genetic affinities with other Near-Eastern populations, while Saudi Arabia and Yemen show a relative distinctive isolated background. Those two populations may have been kept relatively separated from migration routes, maybe due to their location in a desert area.

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The N-acetyltransferase 2 (NAT2) gene plays a crucial role in the metabolism of many drugs and xenobiotics. As it represents a likely target of population-specific selection pressures, we fully sequenced the NAT2 coding region in 97 Mandenka individuals from Senegal, and compared these sequences to extant data on other African populations. The Mandenka data were further included in a worldwide dataset composed of 41 published population samples (6,727 individuals) from four continental regions that were adequately genotyped for all common NAT2 variants so as to provide further insights into the worldwide haplotype diversity and population structure at NAT2.

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We have typed 275 men from five populations in Algeria, Tunisia, and Egypt with a set of 119 binary markers and 15 microsatellites from the Y chromosome, and we have analyzed the results together with published data from Moroccan populations. North African Y-chromosomal diversity is geographically structured and fits the pattern expected under an isolation-by-distance model. Autocorrelation analyses reveal an east-west cline of genetic variation that extends into the Middle East and is compatible with a hypothesis of demic expansion. This expansion must have involved relatively small numbers of Y chromosomes to account for the reduction in gene diversity towards the West that accompanied the frequency increase of Y haplogroup E3b2, but gene flow must have been maintained to explain the observed pattern of isolation-by-distance. Since the estimates of the times to the most recent common ancestor (TMRCAs) of the most common haplogroups are quite recent, we suggest that the North African pattern of Y-chromosomal variation is largely of Neolithic origin. Thus, we propose that the Neolithic transition in this part of the world was accompanied by demic diffusion of Afro-Asiatic-speaking pastoralists from the Middle East.

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The allelic variability at six Y-chromosome-specific polymorphisms (YAP, DYS19, DYS389-I, DYS390, DYS391, and DYS392) was used to generate male-specific haplotypes in 333 males representing 12 population samples from the region around the Mediterranean sea. Extreme interindividual variation was observed, as more than 160 distinct Y-chromosome variants could be defined as six-locus haplotypes. Concomitant with this high variability, low levels of population genetic structure were observed. In particular, a "core" of populations directly facing the north and the east of the Mediterranean basin, from the Middle East to the Italian Peninsula, was found to be genetically undifferentiated. This observation, supported by a reanalysis of Y-specific binary polymorphisms in the same populations, suggests that at least part of the male-specific gene pools of these populations has either a very recent common origin (that could be related with the Neolithic demic diffusion hypothesis), and/or that gene flow has played a significant role in shaping the patterns of genetic variability in this region. In agreement with both hypotheses, we found that the spatial distribution of DYS392 alleles revealed a marked differentiation between the East and the West of the Mediterranean area. Through the analysis of microsatellite variation, the time to the most recent common ancestor (TMRCA) of the YAP(+) sublineage 4 has been estimated. The estimations, based on two different data sets, turn out to be quite recent (7,000-11,000 YBP), suggesting that this lineage may have been first introduced into Southern Europe through Neolithic migrations from the Middle East.

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