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Agnes SJOSTRAND

MNHN, rue Buffon

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Status : PhD student

Research team

- Population Genetics

Interdisciplinary Research Themes

- Population Genetics
- Biological anthropology
- Modelling
- Statistics

Research Interests

I am interested in human individuals’ adaptation to their environment and how the constraints imposed by it act / have acted on different populations of the planet during the species’ history. What especially interests me in the case of the Human is that the constraints can come from the outside, for example from culture, complexifying the interpretation of results.

During my master, I started developing a method that enabled the detection of positive selection traces specific to sub-populations of species. This method based on the study of haplotypical structures enables the study of selection events due to the each population’s specific environment. Applied to human data, this method is especially responsive to selection for milk digestion in adults in European and Massaï populations.

I also studied in a second work experience alcohol digestion in two Central Asian populations, different both in genetic origins and lifestyle (Kirghizes and Tadjiks). Finally, another work experience enabled me to develop human phylogeny models from re-sequencing data, with the aim to shed light on relations between H. sapiens and H. neanderthalensis.

I am currently working towards a joint PhD with Uppsala University on taste perceptions in populations in relation with their environment and livelihood. This project aims to study four populations in two world regions : The Central African forest (Bakas and Nzimés), and Central Asia (Kirghizes and Tadjiks). These two regions vary in both their climates and diversity in alimentary resources but their people are also different in their livelihoods : Bakas hunter gatherers, Kirghizes nomadic herders, Tadjiks and Nzimés farmers. By studying both sensitivity to taste (sweet, salty, acid, sour, unami) and genes (genetic diversity, selection tests, association studies), I study different perceptions and try to understand how taste perceptions have adapted to environments and lifestyles.

Thesis topic
Origins and Adaptation in Humans : a Case Study of Taste and Lifestyle
In this thesis, I use population genetics and statistical approaches to investigate early human demography, infer local adaptation in diverse sets of populations, and study the genetic basis for taste perception.

In the first paper, I examine the genomic evidence for a severe bottleneck, which has been suggested based on paleontological and climate studies to coincide with the emergence of anatomically modern humans. Using a Bayesian approach, I evaluate the genetic evidence of a bottleneck between 190,000 and 130,000 years ago and find that the data is in favor of a model without bottleneck at this time point.

I further develop a method to detect local adaptation based on frequencies of private haplotypes. I first show, using simulated data, that this method can detect local adaption. Applied to large-scale human genotype data, this method detects known signals of positive selection in human data such as the positive selection around the lactase gene in Europeans and East Africans. Also, this method permits to improve knowledge on potential adaptation events in humans as it finds several regions potentially selected that were not previously described. I further investigate patterns of adaptation in whole genome data based on a diverse set of African populations. The results from the regions potentially selected show that diet and pathogens are the common driving forces of adaptation in all studied populations.

There is evidence that taste perception have evolved in concert with diet, environment, and the organismal needs in humans. For this reason, I study taste perception in populations differing on lifestyle (hunter-gatherers, farmers and nomad herders). I present taste perception phenotypes for all tastes (sweet, bitter, sour, salty and umami) and relate them to high density genotype data. I show that taste and taste-involved genes have evolved with lifestyle. By performing an association study, I also show that variation in taste perception involves more genes than only the taste receptors genes.

In this thesis, by analyzing human genetic data with a population genetics approaches, I covered several topics of human ancient demography and adaptation and show the utility of using large-scale genetic data to better understand human history."

Doctoral School

Diversité du Vivant, Université Paris VI.

Evelyne Heyer (Directrice de thèse) Mattias Jakobsson (Directeur de thèse) Michael Blum (Directeur de thèse)

Jury : David Comas (Rapporteur et "opponent") Lluis Quintana-Murci (Rapporteur) Åsa Johansson (Examinatrice) Denis Pierron (Examinateur) Thierry Wirth (Examinateur)

Current Publications

Sjöstrand AE., Sjödin P, Jakobsson M. “Private Haplotypes as selection detectors” Sjöstrand AE, Heyer E. “Population genetics of Alcohol Dehydrogenase 1B in Central Asia”

Publications

Per Sjödin, Agnès E. Sjöstrand, Mattias Jakobsson, and Michael G.B. Blum Resequencing Data Provide No Evidence for a Human Bottleneck in Africa during the Penultimate Glacial Period Mol Biol Evol (2012) 29(7) : 1851-1860 doi:10.1093/molbev/mss061