collaborateurs

Pascale Gerbault

Maître-assistant(e) chez Anthropologie & Immunogénétique

  • T: +41 22 379 69 64
  • office 4-414 (Sciences II)

  • A genomic history of Aboriginal Australia. Nature 2016 Oct;538(7624):207-214. nature18299. 10.1038/nature18299.

    résumé

    The population history of Aboriginal Australians remains largely uncharacterized. Here we generate high-coverage genomes for 83 Aboriginal Australians (speakers of Pama-Nyungan languages) and 25 Papuans from the New Guinea Highlands. We find that Papuan and Aboriginal Australian ancestors diversified 25-40 thousand years ago (kya), suggesting pre-Holocene population structure in the ancient continent of Sahul (Australia, New Guinea and Tasmania). However, all of the studied Aboriginal Australians descend from a single founding population that differentiated ~10-32 kya. We infer a population expansion in northeast Australia during the Holocene epoch (past 10,000 years) associated with limited gene flow from this region to the rest of Australia, consistent with the spread of the Pama-Nyungan languages. We estimate that Aboriginal Australians and Papuans diverged from Eurasians 51-72 kya, following a single out-of-Africa dispersal, and subsequently admixed with archaic populations. Finally, we report evidence of selection in Aboriginal Australians potentially associated with living in the desert.

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  • Correction to: "Forward-in-Time, Spatially Explicit Modeling Software to Simulate Genetic Lineages Under Selection". Evol. Bioinform. Online 2015 ;11(Suppl 2):69. 10.4137/EBO.S39777. ebo-suppl.2-2015-069. PMC4939849.

    résumé

    [This corrects the article DOI: 10.4137/EBO.S33488.].

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  • Forward-in-Time, Spatially Explicit Modeling Software to Simulate Genetic Lineages Under Selection. Evol. Bioinform. Online 2015 ;11(Suppl 2):27-39. 10.4137/EBO.S33488. ebo-suppl.2-2015-027. PMC4768942.

    résumé

    SELECTOR is a software package for studying the evolution of multiallelic genes under balancing or positive selection while simulating complex evolutionary scenarios that integrate demographic growth and migration in a spatially explicit population framework. Parameters can be varied both in space and time to account for geographical, environmental, and cultural heterogeneity. SELECTOR can be used within an approximate Bayesian computation estimation framework. We first describe the principles of SELECTOR and validate the algorithms by comparing its outputs for simple models with theoretical expectations. Then, we show how it can be used to investigate genetic differentiation of loci under balancing selection in interconnected demes with spatially heterogeneous gene flow. We identify situations in which balancing selection reduces genetic differentiation between population groups compared with neutrality and explain conflicting outcomes observed for human leukocyte antigen loci. These results and three previously published applications demonstrate that SELECTOR is efficient and robust for building insight into human settlement history and evolution.

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  • Evolution of lactase persistence: an example of human niche construction. Philos. Trans. R. Soc. Lond., B, Biol. Sci. 2011 Mar;366(1566):863-77. 366/1566/863. 10.1098/rstb.2010.0268. PMC3048992.

    résumé

    Niche construction is the process by which organisms construct important components of their local environment in ways that introduce novel selection pressures. Lactase persistence is one of the clearest examples of niche construction in humans. Lactase is the enzyme responsible for the digestion of the milk sugar lactose and its production decreases after the weaning phase in most mammals, including most humans. Some humans, however, continue to produce lactase throughout adulthood, a trait known as lactase persistence. In European populations, a single mutation (-13910*T) explains the distribution of the phenotype, whereas several mutations are associated with it in Africa and the Middle East. Current estimates for the age of lactase persistence-associated alleles bracket those for the origins of animal domestication and the culturally transmitted practice of dairying. We report new data on the distribution of -13910*T and summarize genetic studies on the diversity of lactase persistence worldwide. We review relevant archaeological data and describe three simulation studies that have shed light on the evolution of this trait in Europe. These studies illustrate how genetic and archaeological information can be integrated to bring new insights to the origins and spread of lactase persistence. Finally, we discuss possible improvements to these models.

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  • Impact of selection and demography on the diffusion of lactase persistence. PLoS ONE 2009 ;4(7):e6369. 10.1371/journal.pone.0006369. PMC2711333.

    résumé

    The lactase enzyme allows lactose digestion in fresh milk. Its activity strongly decreases after the weaning phase in most humans, but persists at a high frequency in Europe and some nomadic populations. Two hypotheses are usually proposed to explain the particular distribution of the lactase persistence phenotype. The gene-culture coevolution hypothesis supposes a nutritional advantage of lactose digestion in pastoral populations. The calcium assimilation hypothesis suggests that carriers of the lactase persistence allele(s) (LCT*P) are favoured in high-latitude regions, where sunshine is insufficient to allow accurate vitamin-D synthesis. In this work, we test the validity of these two hypotheses on a large worldwide dataset of lactase persistence frequencies by using several complementary approaches.

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Mes principaux thèmes de recherche portent sur l'évolution de la diversité génétique dans les populations. J'utilise plus particulièrement des outils bioinformatiques et des modèles de simulation informatique afin d'intégrer différents types de données (par exemple données génétiques et archéologiques) dans l'inférence d'hypothèses évolutives. 

Mes travaux en cours portent sur la diversité de gènes HLA dans des populations africaines avec la Prof. Alicia Sanchez-Mazas (HLA-AFRICA).

Mes intérêts de recherche portent aussi sur les maladies infectieuses, et je co-supervise un projet de doctorat sur la distribution des tréponématoses (la syphilis et le pian) au Ghana (financement GCRF).