title: Extensive Admixture and Selective Pressure Across the Sahel Belt.
abstract: Genome-wide studies of African populations have the potential to reveal powerful insights into the evolution of our species, as these diverse populations have been exposed to intense selective pressures imposed by infectious diseases, diet, and environmental factors. Within Africa, the Sahel Belt extensively overlaps the geographical center of several endemic infections such as malaria, trypanosomiasis, meningitis, and hemorrhagic fevers. We screened 2.5 million single nucleotide polymorphisms in 161 individuals from 13 Sahelian populations, which together with published data cover Western, Central, and Eastern Sahel, and include both nomadic and sedentary groups. We confirmed the role of this Belt as a main corridor for human migrations across the continent. Strong admixture was observed in both Central and Eastern Sahelian populations, with North Africans and Near Eastern/Arabians, respectively, but it was inexistent in Western Sahelian populations. Genome-wide local ancestry inference in admixed Sahelian populations revealed several candidate regions that were significantly enriched for non-autochthonous haplotypes, and many showed to be under positive selection. The DARC gene region in Arabs and Nubians was enriched for African ancestry, whereas the RAB3GAP1/LCT/MCM6 region in Oromo, the TAS2R gene family in Fulani, and the ALMS1/NAT8 in Turkana and Samburu were enriched for non-African ancestry. Signals of positive selection varied in terms of geographic amplitude. Some genomic regions were selected across the Belt, the most striking example being the malaria-related DARC gene. Others were Western-specific (oxytocin, calcium, and heart pathways), Eastern-specific (lipid pathways), or even population-restricted (TAS2R genes in Fulani, which may reflect sexual selection).
authors.affiliation: Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal Instituto de Patologia e Imunologia Molecular da Universidade do Porto (IPATIMUP), Porto, Portugal Instituto de Ciências Biomédicas Abel Salazar da Universidade do Porto (ICBAS), Porto, Portugal.
authors.forename: Petr
authors.initials: P
authors.lastname: Triska
authors.affiliation: Instituto de Patologia e Imunologia Molecular da Universidade do Porto (IPATIMUP), Porto, Portugal Department of Biology, CBMA (Centre of Molecular and Environmental Biology), University of Minho, Braga, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Soares
authors.affiliation: Unit of Human Evolutionary Genetics, Institut Pasteur, Paris, France Centre National de la Recherche Scientifique, Paris, France.
authors.forename: Etienne
authors.initials: E
authors.lastname: Patin
authors.affiliation: Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal Instituto de Patologia e Imunologia Molecular da Universidade do Porto (IPATIMUP), Porto, Portugal.
authors.forename: Veronica
authors.initials: V
authors.lastname: Fernandes
authors.affiliation: Archaeogenetics Laboratory, Institute of Archaeology of the Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: Viktor
authors.initials: V
authors.lastname: Cerny
authors.affiliation: Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal Instituto de Patologia e Imunologia Molecular da Universidade do Porto (IPATIMUP), Porto, Portugal Faculdade de Medicina da Universidade do Porto, Porto, Portugal lpereira@ipatimup.pt.
authors.forename: Luisa
authors.initials: L
authors.lastname: Pereira
mesh_terms: D000123:Acetyltransferases / Q000235:genetics; D000349:Africa; D018797:Cell Cycle Proteins; D004375:Duffy Blood-Group System / Q000235:genetics; D015894:Genome, Human; D006239:Haplotypes; D006482:Hemorrhagic Fevers, Viral / Q000235:genetics; D063426:Human Migration; D006801:Humans; D008288:Malaria / Q000235:genetics; D008581:Meningitis / Q000235:genetics; D064151:Minichromosome Maintenance Complex Component 6 / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D011506:Proteins / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics; D043562:Receptors, G-Protein-Coupled / Q000235:genetics; D012641:Selection, Genetic
chemical_list: C473745:ACKR1 protein, human; C490729:ALMS1 protein, human; D018797:Cell Cycle Proteins; D004375:Duffy Blood-Group System; D011506:Proteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C568609:TAS2R1 protein, human; D000123:Acetyltransferases; C116373:NAT8 protein, human; C103258:MCM6 protein, human; D064151:Minichromosome Maintenance Complex Component 6
keywords: Sahel; admixture; genome-wide diversity; selection