Biology subjects

Laval, G.

Publications and source records attributed to Laval, G..

8 recordsLinked to original sources

bioRxiv2026

A 4,000-year genomic history of Bantu speakers from the Congo rainforest

The Congo rainforest was the heartland of the Bantu Expansion, yet its demographic history remains partially understood. We inferred past population dynamics using genomes from 960 sub-Saharan Africans, including four newly sequenced ancient individuals from Iroungou cave and 176 present-day individuals from Gabon. Bantu-speaking populations began differentiating ~4,000 years ago, preceding explosive population growth by a millennium. Distinct southward dispersals contributed to the ancestry of Bantu speakers in Gabon and elsewhere in sub-Saharan Africa, with the ~700-year-old Iroungou individuals providing the closest genetic proxies for the latter. Both Bantu speakers and hunter-gatherers from the Congo rainforest experienced a major demographic crisis ~1,500 years ago, coinciding with an archaeological hiatus. These findings illuminate early Bantu dispersals and the subsequent, unexplained collapse of rainforest populations.

genomics↗

bioRxiv2026

Evolution of the genetic architecture of uterine disorders

Uterine disorders and menstrual abnormalities are prevalent reproductive conditions with significant clinical consequences. Recent genome-wide association studies have identified hundreds of variants contributing to different uterine disorders, while epidemiological evidence suggests that these disorders co-occur more frequently than expected, implying shared genetic mechanisms. However, the specific genetic variants and biological pathways underlying this shared architecture remain poorly characterized. Here, we conducted a uterus-centric, multi-trait genome-wide association analysis across ten uterine disorders in a European cohort to elucidate this shared genetic architecture. Further, we embedded this architecture in a functional and population genomics framework to investigate its plausible biological mechanisms and its evolutionary history in humans. We confirm strong positive genetic correlations between major uterine disorders and identify 31 independent susceptibility loci jointly affecting the genetic risk of multiple uterine pathologies, substantiating an intertwined biological basis. Populational analyses demonstrated that several of these susceptibility variants exhibit pronounced allele frequency differentiation across global populations suggestive of recent polygenic selection, including variants with well-supported regulatory functions at the ESR1-CCDC170, WNT4, SFR1, FOXO1, ITPR1, DMRT1 and CDKN2B loci. Notably, we show that most derived alleles acquired during recent human evolution increase risk across multiple uterine disorders and may evolve under antagonistic selection. These findings provide functional annotation and population-level prioritization of genetic variants influencing multiple uterine disorders. They also highlight how past evolutionary histories may contribute to population differences in uterine disease prevalence and pathogenesis.

genetics↗

bioRxiv2025

Deep learning analyses of DNA sequences resolve the retention of the Duffy-null resistance to Plasmodium vivax malaria in Africa

P. vivax, the most geographically widespread human malaria parasite with millions of clinical cases per year, is however quasi absent in sub-Saharan Africa. Positive selection targeting the rs2814778 protective mutation, also known as the Duffy-null allele, may explain the absence (or quasi absence) of vivax in sub-Saharan Africa by a progressive purge of the pathogen due to a quasi-fixation of the Duffy-null allele and the resulting high rates of protected carriers in western, central and eastern populations. Yet, while positive selection has been clearly evidenced in admixed populations coexisting with vivax, the selection model currently admitted poorly explains the lack of the Duffy-null allele in Europe, or in Asia where the pathogen is mainly observed. In this article, several validated Deep Learning methods applied to high coverage sequence data obtained in 589 African individuals resolved this retention of the Duffy-null resistance to vivax in Africa. The CNN and GAN algorithms implemented in this study also predict a rise in frequency of the Duffy-null mutation due to selection 25-35 kya years ago in the western part of Africa, a geographical region and a time frame overlapping with the rise of another protective mutation, {beta}S, the sickle-cell mutation protective at heterozygous state against the malaria caused by P. falciparum. In addition, the pattern of Duffy-null haplotypes highlights a quick spread of the Duffy-null allele in sub-Saharan Africa due to post-admixture selection events following the road of the recent Bantu expansion. Independent lines of evidence describing malaria as a life-threatening disease in West Africa from [~]30 kya, together with a rise in frequency followed by recent disseminations of the Duffy-null resistance, open new perspectives about both the history of malaria as a major human disease and the history of the main protective mutations in Africa.

evolutionary biology↗

bioRxiv2023

Deep estimation of the intensity and timing of selection from ancient genomes

Leveraging past allele frequencies has proven to be key to identify the impact of natural selection across time. However, this approach often suffers from imprecise estimations of the intensity (s) and timing (T) of selection particularly when ancient samples are scarce in specific epochs. Here, we aimed at bypassing the computation of past allele frequencies by implementing new convolutional neural networks (CNNs) algorithms that directly use ancient genotypes sampled across time to refine the estimations of selection parameters. Using computer simulations, we first show that genotype-based CNNs consistently outperform an approximate Bayesian computation (ABC) approach based on past allele frequency trajectories, regardless of the selection model assumed and of the amount of ancient genotypes available. When applying this method to empirical data from modern and ancient Europeans, we confirmed the reported excess of selection events in post-Neolithic Europe, independently of the continental subregion studied. Furthermore, we substantially refined the ABC-based estimations of s and T for a set of positively-and negatively-selected variants recently identified, including iconic cases of positive selection and experimentally validated disease-risk variants. Thanks to our CNN predictions we provide support to the history of recent and strong selection in northern Europe associated to the Black Death pandemic and confirm the heavy burden recently imposed by tuberculosis in Europe. These findings collectively support that detecting the imprints of natural selection on ancient genomes are crucial for unraveling the past history of severe human diseases.

evolutionary biology↗

bioRxiv2022

Genetic adaptation to pathogens and increased risk of inflammatory disorders in post-Neolithic Europe

Ancient genomics can directly detect human genetic adaptation to environmental cues. However, it remains unclear how pathogens have exerted selective pressures on human genome diversity across different epochs and affected present-day inflammatory disease risk. Here, we use an ancestry-aware approximate Bayesian computation framework to estimate the nature, strength, and time of onset of selection acting on 2,879 ancient and modern European genomes from the last 10,000 years. We found that the bulk of genetic adaptation occurred after the start of the Bronze Age, <4,500 years ago, and was enriched in genes relating to host-pathogen interactions. Furthermore, we detected directional selection acting on specific leukocytic lineages and experimentally demonstrated that the strongest negatively selected immunity gene variant -- the lipopolysaccharide-binding protein gene (LBP) D283G -- is hypomorphic. Finally, our analyses suggest that the risk of inflammatory disorders has progressively increased in post-Neolithic Europeans, partly due to antagonistic pleiotropy following genetic adaptation to pathogens.

genetics↗

bioRxiv2021

The genomic signatures of natural selection in admixed human populations

Admixture has been a pervasive phenomenon in human history, shaping extensively the patterns of population genetic diversity. There is increasing evidence to suggest that admixture can also facilitate genetic adaptation to local environments, i.e., admixed populations acquire beneficial mutations from source populations, a process that we refer to as adaptive admixture. However, the role of adaptive admixture in human evolution and the power to detect it are poorly characterized. Here, we use extensive computer simulations to evaluate the power of several neutrality statistics to detect natural selection in the admixed population, accounting for background selection and assuming different admixture scenarios. We show that two statistics based on admixture proportions, Fadm and LAD, show high power to detect mutations that are beneficial in the admixed population, whereas iHS and FST falsely detect neutral mutations that have been selected in the source populations only. By combining Fadm and LAD into a single statistic, we scanned the genomes of 15 worldwide, admixed populations for signatures of adaptive admixture. We confirm that lactase persistence and resistance to malaria have been under adaptive admixture in West Africa and in Madagascar, North Africa and South Asia, respectively. Our approach also uncovers new cases of adaptive admixture, including the APOL1/MYH9 locus in the Fulani nomads and PKN2 in East Indonesians, involved in resistance to infection and metabolism, respectively. Collectively, our study provides new evidence that adaptive admixture has occurred in multiple human populations, whose genetic history is characterized by periods of isolation and spatial expansions resulting in increased gene flow. Author summaryAdaptive introgression, i.e., the acquisition of adaptive traits through hybridization with another species, is a well-documented phenomenon in evolution. Conversely, adaptive admixture, i.e., the acquisition of adaptive traits through admixture between populations of the same species, is poorly described. In this study, we evaluate the importance of adaptive admixture in human recent evolutionary history. We first determine the expected signatures of adaptive admixture on patterns of genomic diversity, using realistic simulations. We then identify the methods that are the most powerful to detect such molecular signatures. Finally, by using the methods identified as the most powerful, we search for cases of adaptive admixture in the genomes of 15 admixed populations from around the globe. We find evidence that adaptive admixture has occurred in several populations from Northeast Africa, Southeast Asia and Oceania. This study suggests that admixture has indeed facilitated human genetic adaptation, particularly at genes involved in metabolism and resistance against pathogens.

genetics↗

bioRxiv2019

A genome-wide Approximate Bayesian Computation approach suggests only limited numbers of soft sweeps in humans over the last 100,000 years

Over the last 100,000 years, humans have spread across the globe and encountered a highly diverse set of environments to which they have had to adapt. Genome-wide scans of selection are powerful to detect selective sweeps. However, because of unknown fractions of undetected sweeps and false discoveries, the numbers of detected sweeps often poorly reflect actual numbers of selective sweeps in populations. The thousands of soft sweeps on standing variation recently evidenced in humans have also been interpreted as a majority of mis-classified neutral regions. In such a context, the extent of human adaptation remains little understood. We present a new rationale to estimate these actual numbers of sweeps expected over the last 100,000 years (denoted by X) from genome-wide population data, both considering hard sweeps and selective sweeps on standing variation. We implemented an approximate Bayesian computation framework and showed, based on computer simulations, that such a method can properly estimate X. We then jointly estimated the number of selective sweeps, their mean intensity and age in several 1000G African, European and Asian populations. Our estimations of X, found weakly sensitive to demographic misspecifications, revealed very limited numbers of sweeps regardless the frequency of the selected alleles at the onset of selection and the completion of sweeps. We estimated [~]80 sweeps in average across fifteen 1000G populations when assuming incomplete sweeps only and [~]140 selective sweeps in non-African populations when incorporating complete sweeps in our simulations. The method proposed may help to address controversies on the number of selective sweeps in populations, guiding further genome-wide investigations of recent positive selection.

evolutionary biology↗

bioRxiv2017

Evolutionary Genetics of a Disease Susceptibility Locus in CDHR3

Selective pressures imposed by pathogens have varied among human populations throughout their evolution, leading to marked inter-population differences at some genes mediating susceptibility to infectious and immune-related diseases. A common polymorphism resulting in a C529 versus T529 change in the Cadherin-Related Family Member 3 (CDHR3) receptor is associated with rhinovirus-C (RV-C) susceptibility and severe childhood asthma. Given the morbidity and mortality associated with RV-C dependent respiratory infections and asthma, we hypothesized that the protective variant has been under selection in the human population. Supporting this idea, a recent cross-species outbreak of RV-C among chimpanzees in Uganda, which carry the ancestral risk allele at this position, resulted in a mortality rate of 8.9%. Using publicly available genomic data, we sought to determine the evolutionary history and role of selection acting on this infectious disease susceptibility locus. The protective variant is the derived allele and is found at high frequency worldwide, with the lowest relative frequency in African populations and highest in East Asian populations. There is minimal population structure among haplotypes, and we detect genomic signatures consistent with a rapid increase in frequency of the protective allele across all human populations. However, given strong evidence that the protective allele arose in anatomically modern humans prior to their migrations out of Africa and that the allele has not fixed in any population, the patterns observed here are not consistent with a classical selective sweep. We hypothesize that patterns may indicate frequency-dependent selection worldwide. Irrespective of the mode of selection, our analyses show the derived allele has been subject to selection in recent human evolution.

genetics↗