scholarly journals Patterns of genetic differentiation and the footprints of historical migrations in the Iberian Peninsula

2018 ◽  
Author(s):  
Clare Bycroft ◽  
Ceres Fernandez-Rozadilla ◽  
Clara Ruiz-Ponte ◽  
Inés Quintela-García ◽  
Ángel Carracedo ◽  
...  
Keyword(s):  
Population Structure ◽  
Genetic Differentiation ◽  
Iberian Peninsula ◽  
Association Studies ◽  
Demographic History ◽  
African Ancestry ◽  
Population History ◽  
Human Populations ◽  
Fine Scale ◽  
The North

Genetic differences within or between human populations (population structure) has been studied using a variety of approaches over many years. Recently there has been an increasing focus on studying genetic differentiation at fine geographic scales, such as within countries. Identifying such structure allows the study of recent population history, and identifies the potential for confounding in association studies, particularly when testing rare, often recently arisen variants. The Iberian Peninsula is linguistically diverse, has a complex demographic history, and is unique among European regions in having a centuries-long period of Muslim rule. Previous genetic studies of Spain have examined either a small fraction of the genome or only a few Spanish regions. Thus, the overall pattern of fine-scale population structure within Spain remains uncharacterised. Here we analyse genome-wide genotyping array data for 1,413 Spanish individuals sampled from all regions of Spain. We identify extensive fine-scale structure, down to unprecedented scales, smaller than 10 Km in some places. We observe a major axis of genetic differentiation that runs from east to west of the peninsula. In contrast, we observe remarkable genetic similarity in the north-south direction, and evidence of historical north-south population movement. Finally, without making particular prior assumptions about source populations, we show that modern Spanish people have regionally varying fractions of ancestry from a group most similar to modern north Moroccans. The north African ancestry results from an admixture event, which we date to 860 - 1120 CE, corresponding to the early half of Muslim rule. Our results indicate that it is possible to discern clear genetic impacts of the Muslim conquest and population movements associated with the subsequent Reconquista.

scholarly journals The genetic scenario of Mercheros: an under-represented group within the Iberian Peninsula

BMC Genomics ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
André Flores-Bello ◽  
Neus Font-Porterias ◽  
Julen Aizpurua-Iraola ◽  
Sara Duarri-Redondo ◽  
David Comas
Keyword(s):  
Iberian Peninsula ◽  
Demographic History ◽  
Ethnically Diverse ◽  
Human Populations ◽  
Minority Ethnic Group ◽  
Fine Scale ◽  
Genome Wide ◽  
Wide Range ◽  
Y Chromosome Str ◽  
Western Eurasia

Abstract Background The general picture of human genetic variation has been vastly depicted in the last years, yet many populations remain broadly understudied. In this work, we analyze for the first time the Merchero population, a Spanish minority ethnic group that has been scarcely studied and historically persecuted. Mercheros have been roughly characterised by an itinerant history, common traditional occupations, and the usage of their own language. Results Here, we examine the demographic history and genetic scenario of Mercheros, by using genome-wide array data, whole mitochondrial sequences, and Y chromosome STR markers from 25 individuals. These samples have been complemented with a wide-range of present-day populations from Western Eurasia and North Africa. Our results show that the genetic diversity of Mercheros is explained within the context of the Iberian Peninsula, evidencing a modest signal of Roma admixture. In addition, Mercheros present low genetic isolation and intrapopulation heterogeneity. Conclusions This study represents the first genetic characterisation of the Merchero population, depicting their fine-scale ancestry components and genetic scenario within the Iberian Peninsula. Since ethnicity is not only influenced by genetic ancestry but also cultural factors, other studies from multiple disciplines are needed to further explore the Merchero population. As with Mercheros, there is a considerable gap of underrepresented populations and ethnic groups in publicly available genetic data. Thus, we encourage the consideration of more ethnically diverse population panels in human genetic studies, as an attempt to improve the representation of human populations and better reconstruct their fine-scale history.

scholarly journals Fine-scale population structure and demographic history of British Pakistanis

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Elena Arciero ◽  
Sufyan A. Dogra ◽  
Daniel S. Malawsky ◽  
Massimo Mezzavilla ◽  
Theofanis Tsismentzoglou ◽  
...  
Keyword(s):  
Population Structure ◽  
Disease Risk ◽  
Demographic History ◽  
Population History ◽  
Genomic Diversity ◽  
Fine Scale ◽  
Effective Population ◽  
Scale Population ◽  
The Impact ◽  
British Pakistanis

AbstractPrevious genetic and public health research in the Pakistani population has focused on the role of consanguinity in increasing recessive disease risk, but little is known about its recent population history or the effects of endogamy. Here, we investigate fine-scale population structure, history and consanguinity patterns using genotype chip data from 2,200 British Pakistanis. We reveal strong recent population structure driven by the biraderi social stratification system. We find that all subgroups have had low recent effective population sizes (Ne), with some showing a decrease 15‒20 generations ago that has resulted in extensive identity-by-descent sharing and homozygosity, increasing the risk of recessive disorders. Our results from two orthogonal methods (one using machine learning and the other coalescent-based) suggest that the detailed reporting of parental relatedness for mothers in the cohort under-represents the true levels of consanguinity. These results demonstrate the impact of cultural practices on population structure and genomic diversity in Pakistanis, and have important implications for medical genetic studies.

scholarly journals Genetic landscapes reveal how human genetic diversity aligns with geography

2017 ◽  
Author(s):  
Benjamin Marco Peter ◽  
Desislava Petkova ◽  
John Novembre
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Genetic Differentiation ◽  
Rare Variants ◽  
Disease Risk ◽  
Geographic Distance ◽  
Population History ◽  
Human Populations ◽  
Complex Processes ◽  
Scale Population

Geographic patterns in human genetic diversity carry footprints of population history1,2 and provide insights for genetic medicine and its application across human populations3,4. Summarizing and visually representing these patterns of diversity has been a persistent goal for human geneticists5–10, and has revealed that genetic differentiation is frequently correlated with geographic distance. However, most analytical methods to represent population structure11–15 do not incorporate geography directly, and it must be considered post hoc alongside a visual summary. Here, we use a recently developed spatially explicit method to estimate “effective migration” surfaces to visualize how human genetic diversity is geographically structured (the EEMS method16). The resulting surfaces are “rugged”, which indicates the relationship between genetic and geographic distance is heterogenous and distorted as a rule. Most prominently, topographic and marine features regularly align with increased genetic differentiation (e.g. the Sahara desert, Mediterranean Sea or Himalaya at large scales; the Adriatic, interisland straits in near Oceania at smaller scales). In other cases, the locations of historical migrations and boundaries of language families align with migration features. These results provide visualizations of human genetic diversity that reveal local patterns of differentiation in detail and emphasize that while genetic similarity generally decays with geographic distance, there have regularly been factors that subtly distort the underlying relationship across space observed today. The fine-scale population structure depicted here is relevant to understanding complex processes of human population history and may provide insights for geographic patterning in rare variants and heritable disease risk.

scholarly journals Fine-scale population structure and demographic history of British Pakistanis

2020 ◽  
Author(s):  
Elena Arciero ◽  
Sufyan A. Dogra ◽  
Massimo Mezzavilla ◽  
Theofanis Tsismentzoglou ◽  
Qin Qin Huang ◽  
...  
Keyword(s):  
Population Structure ◽  
Disease Risk ◽  
Demographic History ◽  
Population History ◽  
Genomic Diversity ◽  
Fine Scale ◽  
Effective Population ◽  
Scale Population ◽  
The Impact ◽  
British Pakistanis

AbstractPrevious genetic and public health research in the Pakistani population has focused on the role of consanguinity in increasing recessive disease risk, but little is known about its recent population history or the effects of endogamy. Here, we investigate fine-scale population structure, history and consanguinity patterns using genetic and questionnaire data from >4,000 British Pakistani individuals, mostly with roots in Azad Kashmir and Punjab. We reveal strong recent population structure driven by the biraderi social stratification system. We find that all subgroups have had low effective population sizes (Ne) over the last 50 generations, with some showing a decrease in Ne 15-20 generations ago that has resulted in extensive identity-by-descent sharing and increased homozygosity. Using new theory, we show that the footprint of regions of homozygosity in the two largest subgroups is about twice that expected naively based on the self-reported consanguinity rates and the inferred historical Ne trajectory. These results demonstrate the impact of the cultural practices of endogamy and consanguinity on population structure and genomic diversity in British Pakistanis, and have important implications for medical genetic studies.

scholarly journals Fine-scale population structure of Malays in Peninsular Malaysia and Singapore and implications for association studies

2015 ◽  
Vol 9 (1) ◽  
Author(s):  
Boon-Peng Hoh ◽  
Lian Deng ◽  
Mat Jusoh Julia-Ashazila ◽  
Zakaria Zuraihan ◽  
Ma’amor Nur-Hasnah ◽  
...  
Keyword(s):  
Population Structure ◽  
Association Studies ◽  
Peninsular Malaysia ◽  
Fine Scale ◽  
Scale Population

scholarly journals Contributions of common genetic variants to risk of schizophrenia among individuals of African and Latino ancestry

2019 ◽  
Vol 25 (10) ◽  
pp. 2455-2467 ◽  
Author(s):  
Tim B. Bigdeli ◽  
◽  
Giulio Genovese ◽  
Penelope Georgakopoulos ◽  
Jacquelyn L. Meyers ◽  
...  
Keyword(s):  
Genetic Variants ◽  
Association Studies ◽  
Large Fraction ◽  
African Ancestry ◽  
Common Variant ◽  
Human Populations ◽  
Polygenic Risk Score ◽  
Genome Wide Association Studies ◽  
Genome Wide ◽  
Common Genetic Variants

Abstract Schizophrenia is a common, chronic and debilitating neuropsychiatric syndrome affecting tens of millions of individuals worldwide. While rare genetic variants play a role in the etiology of schizophrenia, most of the currently explained liability is within common variation, suggesting that variation predating the human diaspora out of Africa harbors a large fraction of the common variant attributable heritability. However, common variant association studies in schizophrenia have concentrated mainly on cohorts of European descent. We describe genome-wide association studies of 6152 cases and 3918 controls of admixed African ancestry, and of 1234 cases and 3090 controls of Latino ancestry, representing the largest such study in these populations to date. Combining results from the samples with African ancestry with summary statistics from the Psychiatric Genomics Consortium (PGC) study of schizophrenia yielded seven newly genome-wide significant loci, and we identified an additional eight loci by incorporating the results from samples with Latino ancestry. Leveraging population differences in patterns of linkage disequilibrium, we achieve improved fine-mapping resolution at 22 previously reported and 4 newly significant loci. Polygenic risk score profiling revealed improved prediction based on trans-ancestry meta-analysis results for admixed African (Nagelkerke’s R2 = 0.032; liability R2 = 0.017; P < 10−52), Latino (Nagelkerke’s R2 = 0.089; liability R2 = 0.021; P < 10−58), and European individuals (Nagelkerke’s R2 = 0.089; liability R2 = 0.037; P < 10−113), further highlighting the advantages of incorporating data from diverse human populations.

scholarly journals Human demographic history impacts genetic risk prediction across diverse populations

2016 ◽  
Author(s):  
Alicia R. Martin ◽  
Christopher R. Gignoux ◽  
Raymond K. Walters ◽  
Genevieve L. Wojcik ◽  
Benjamin M. Neale ◽  
...  
Keyword(s):  
Risk Prediction ◽  
Large Scale ◽  
Disease Risk ◽  
Association Studies ◽  
Demographic History ◽  
Population History ◽  
Risk Scores ◽  
Genome Wide Association Studies ◽  
Summary Statistics ◽  
Medical Genomics

AbstractThe vast majority of genome-wide association studies are performed in Europeans, and their transferability to other populations is dependent on many factors (e.g. linkage disequilibrium, allele frequencies, genetic architecture). As medical genomics studies become increasingly large and diverse, gaining insights into population history and consequently the transferability of disease risk measurement is critical. Here, we disentangle recent population history in the widely-used 1000 Genomes Project reference panel, with an emphasis on populations underrepresented in medical studies. To examine the transferability of single-ancestry GWAS, we used published summary statistics to calculate polygenic risk scores for six well-studied traits and diseases. We identified directional inconsistencies in all scores; for example, height is predicted to decrease with genetic distance from Europeans, despite robust anthropological evidence that West Africans are as tall as Europeans on average. To gain deeper quantitative insights into GWAS transferability, we developed a complex trait coalescent-based simulation framework considering effects of polygenicity, causal allele frequency divergence, and heritability. As expected, correlations between true and inferred risk were typically highest in the population from which summary statistics were derived. We demonstrated that scores inferred from European GWAS were biased by genetic drift in other populations even when choosing the same causal variants, and that biases in any direction were possible and unpredictable. This work cautions that summarizing findings from large-scale GWAS may have limited portability to other populations using standard approaches, and highlights the need for generalized risk prediction methods and the inclusion of more diverse individuals in medical genomics.

scholarly journals Ancient ancestry informative markers for identifying fine-scale ancient population structure in Eurasians

2018 ◽  
Author(s):  
Umberto Esposito ◽  
Ranajit Das ◽  
Mehdi Pirooznia ◽  
Eran Elhaik
Keyword(s):  
Population Structure ◽  
Ancient Dna ◽  
Principal Component ◽  
Population History ◽  
Fine Scale ◽  
Ancestry Informative Markers ◽  
Ancient Population ◽  
Human Genomes ◽  
Rapid Accumulation ◽  
Time Periods

AbstractThe rapid accumulation of ancient human genomes from various areas and time periods potentially allows the expansion of studies of biodiversity, biogeography, forensics, population history, and epidemiology into past populations. However, most ancient DNA (aDNA) data were generated through microarrays designed for modern-day populations known to misrepresent the population structure. Past studies addressed these problems using ancestry informative markers (AIMs). However, it is unclear whether AIMs derived from contemporary human genomes can capture ancient population structure and whether AIM finding methods are applicable to ancient DNA (aDNA) provided that the high missingness rates in ancient, oftentimes haploid, DNA can also distort the population structure. Here, we define ancient AIMs (aAIMs) and develop a framework to evaluate established and novel AIM-finding methods in identifying the most informative markers. We show that aAIMs identified by a novel principal component analysis (PCA)-based method outperforms all competing methods in classifying ancient individuals into populations and identifying admixed individuals. In some cases, predictions made using the aAIMs were more accurate than those made with a complete marker set. We discuss the features of the ancient Eurasian population structure and strategies to identify aAIMs. This work informs the design of population microarrays and the interpretation of aDNA results.

scholarly journals Large-scale geographic survey provides insights into the colonization history of a major aphid pest on its cultivated apple host in Europe, North America and North Africa

2020 ◽  
Author(s):  
S.G. Olvera-Vazquez ◽  
C. Remoue ◽  
A. Venon ◽  
A. Rousselet ◽  
O. Grandcolas ◽  
...  
Keyword(s):  
Gene Flow ◽  
North America ◽  
Genetic Differentiation ◽  
North Africa ◽  
Large Scale ◽  
Demographic History ◽  
High Genetic Diversity ◽  
The North ◽  
The Us ◽  
History Of

With frequent host shifts involving the colonization of new hosts across large geographical ranges, crop pests are good models for examining the mechanisms of rapid colonization. The microbial partners of pest insects may be involved or affected by colonization, which has been little studied so far. We investigated the demographic history of the rosy apple aphid, Dysaphis plantaginea, a major pest of the cultivated apple (Malus domestica) in Europe, North Africa and North America, as well as the diversity of its endosymbiotic bacterial community. We genotyped a comprehensive sample of 714 colonies from Europe, Morocco and the US using mitochondrial (CytB and CO1), bacterial (16s rRNA and TrnpB), and 30 microsatellite markers. We detected five populations spread across the US, Morocco, Western and Eastern Europe, and Spain. Populations showed weak genetic differentiation and high genetic diversity, except the Moroccan and the North American that are likely the result of recent colonization events. Coalescent-based inferences releaved high levels of gene flow among populations during the colonization, but did not allow determining the sequence of colonization of Europe, America and Morroco by D. plantaginea, likely because of the weak genetic differentiation and the occurrence of gene flow among populations. Finally, we found that D. plantaginea rarely hosts any other endosymbiotic bacteria than its obligate nutritional symbiont Buchnera aphidicola. This suggests that secondary endosymbionts did not play any role in the rapid spread of the rosy apple aphid. These findings have fundamental importance for understanding pest colonization processes and implications for sustainable pest control programs.

Sign in / Sign up

Export Citation Format

Share Document