scholarly journals Strong selective sweeps before 45,000BP displaced archaic admixture across the human X chromosome

2018 ◽  
Author(s):  
L. Skov ◽  
M.C. Macià ◽  
E. Lucotte ◽  
M.I.A. Cavassim ◽  
D. Castellano ◽  
...  
Keyword(s):  
Natural Selection ◽  
X Chromosome ◽  
Selective Sweeps ◽  
High Frequencies ◽  
African Populations ◽  
Neanderthal Admixture ◽  
Archaic Admixture ◽  
Out Of Africa ◽  
Expected Proportion

AbstractThe X chromosome in non-African populations has less diversity and less Neanderthal introgression than expected. We analyzed X chromosome diversity across the globe and discovered seventeen chromosomal regions, where haplotypes of several hundred kilobases have recently reached high frequencies in non-African populations only. The selective sweeps must have occurred more than 45,000 years ago because the ancient Ust’-Ishim male also carries its expected proportion of these haplotypes. Surprisingly, the swept haplotypes are entirely devoid of Neanderthal introgression, which implies that a population without Neanderthal admixture contributed the swept haplotypes. It also implies that the sweeps must have happened after the main interbreeding event with Neanderthals about 55,000 BP. These swept haplotypes may thus be the only genetic remnants of an earlier out-of-Africa event.One Sentence SummaryAfter humans expanded out of Africa, the X chromosome experienced a burst of extreme natural selection that removed Neanderthal admixture.

scholarly journals A Microsatellite Variability Screen for Positive Selection Associated With the “Out of Africa” Habitat Expansion of Drosophila melanogaster

Genetics ◽  
2003 ◽  
Vol 165 (3) ◽  
pp. 1137-1148
Author(s):  
M O Kauer ◽  
D Dieringer ◽  
C Schlötterer
Keyword(s):  
X Chromosome ◽  
Theoretical Work ◽  
Selective Sweeps ◽  
Mapping Study ◽  
X Chromosomes ◽  
The Third ◽  
African Populations ◽  
Average Loss ◽  
Out Of Africa ◽  
Genomic Regions

Abstract We report a “hitchhiking mapping” study in D. melanogaster, which searches for genomic regions with reduced variability. The study's aim was to identify selective sweeps associated with the “out of Africa” habitat expansion. We scanned 103 microsatellites on chromosome 3 and 102 microsatellites on the X chromosome for reduced variability in non-African populations. When the chromosomes were analyzed separately, the number of loci with a significant reduction in variability only slightly exceeded the expectation under neutrality—six loci on the third chromosome and four loci on the X chromosome. However, non-African populations also have a more pronounced average loss in variability on the X chromosomes as compared to the third chromosome, which suggests the action of selection. Therefore, comparing the X chromosome to the autosome yields a higher number of significantly reduced loci. However, a more pronounced loss of variability on the X chromosome may be caused by demographic events rather than by natural selection. We therefore explored a range of demographic scenarios and found that some of these captured most, but not all aspects of our data. More theoretical work is needed to evaluate how demographic events might differentially affect X chromosomes and autosomes and to estimate the most likely scenario associated with the out of Africa expansion of D. melanogaster.

scholarly journals Fine-mapping the Favored Mutation in a Positive Selective Sweep

2017 ◽  
Author(s):  
Ali Akbari ◽  
Joseph J. Vitti ◽  
Arya Iranmehr ◽  
Mehrdad Bakhtiari ◽  
Pardis C. Sabeti ◽  
...  
Keyword(s):  
Selective Sweep ◽  
Population Genomics ◽  
Simulated Data ◽  
Human Populations ◽  
Selective Sweeps ◽  
1000 Genomes ◽  
Candidate Mutation ◽  
African Populations ◽  
Signature Of Selection ◽  
Out Of Africa

AbstractMethods to identify signatures of selective sweeps in population genomics data have been actively developed, but mostly do not identify the specific mutation favored by the selective sweep. We present a method, iSAFE, that uses a statistic derived solely from population genetics signals to pinpoint the favored mutation even when the signature of selection extends to 5Mbp. iSAFE was tested extensively on simulated data and in human populations from the 1000 Genomes Project, at 22 loci with previously characterized selective sweeps. For 14 of the 22 loci, iSAFE ranked the previously characterized candidate mutation among the 13 highest scoring (out of ∼ 21, 000 variants). Three loci did not show a strong signal. For the remaining loci, iSAFE identified previously unreported mutations as being favored. In these regions, all of which involve pigmentation related genes, iSAFE identified identical selected mutations in multiple non-African populations suggesting an out-of-Africa onset of selection. The iSAFE software can be downloaded from https://github.com/alek0991/iSAFE.

Ancient Genomics of Modern Humans: The First Decade

2018 ◽  
Vol 19 (1) ◽  
pp. 381-404 ◽  
Author(s):  
Pontus Skoglund ◽  
Iain Mathieson
Keyword(s):  
Genetic Diversity ◽  
Natural Selection ◽  
Phenotypic Diversity ◽  
Modern Human ◽  
Modern Humans ◽  
Human Genomes ◽  
African Populations ◽  
History Of ◽  
Out Of Africa ◽  
Genomic Basis

The first decade of ancient genomics has revolutionized the study of human prehistory and evolution. We review new insights based on prehistoric modern human genomes, including greatly increased resolution of the timing and structure of the out-of-Africa expansion, the diversification of present-day non-African populations, and the earliest expansions of those populations into Eurasia and America. Prehistoric genomes now document population transformations on every inhabited continent—in particular the effect of agricultural expansions in Africa, Europe, and Oceania—and record a history of natural selection that shapes present-day phenotypic diversity. Despite these advances, much remains unknown, in particular about the genomic histories of Asia (the most populous continent) and Africa (the continent that contains the most genetic diversity). Ancient genomes from these and other regions, integrated with a growing understanding of the genomic basis of human phenotypic diversity, will be in focus during the next decade of research in the field.

Chromosomal Patterns of Microsatellite Variability Contrast Sharply in African and Non-African Populations of Drosophila melanogaster

Genetics ◽  
2002 ◽  
Vol 160 (1) ◽  
pp. 247-256
Author(s):  
M Kauer ◽  
B Zangerl ◽  
D Dieringer ◽  
C Schlötterer
Keyword(s):  
Chromosomal Polymorphism ◽  
Background Selection ◽  
Selective Sweeps ◽  
X Chromosomes ◽  
Evolutionary Forces ◽  
Relative Contribution ◽  
African Populations ◽  
Neutral Variation ◽  
Colonization Process ◽  
The Subject

Abstract Levels of neutral variation are influenced by background selection and hitchhiking. The relative contribution of these evolutionary forces to the distribution of neutral variation is still the subject of ongoing debates. Using 133 microsatellites, we determined levels of variability on X chromosomes and autosomes in African and non-African D. melanogaster populations. In the ancestral African populations microsatellite variability was higher on X chromosomes than on autosomes. In non-African populations X-linked polymorphism is significantly more reduced than autosomal variation. In non-African populations we observed a significant positive correlation between X chromosomal polymorphism and recombination rate. These results are consistent with the interpretation that background selection shapes levels of neutral variability in the ancestral populations, while the pattern in derived populations is determined by multiple selective sweeps during the colonization process. Further research, however, is required to investigate the influence of inversion polymorphisms and unequal sex ratios.

Selection on X-linked Genes During Speciation in the Drosophila athabasca Complex

Genetics ◽  
1996 ◽  
Vol 144 (2) ◽  
pp. 689-703 ◽  
Author(s):  
Michael J Ford ◽  
Charles F Aquadro
Keyword(s):  
Computer Simulation ◽  
Natural Selection ◽  
Molecular Evolution ◽  
Restriction Site ◽  
Neutral Model ◽  
Background Selection ◽  
Selective Sweeps ◽  
Differential Migration ◽  
Site Survey ◽  
Low Levels

Abstract We present the results of a restriction site survey of variation at five loci in Drosophila athabasca, complimenting a previous study of the period locus. There is considerably greater differentiation between the three semispecies of D. athabasca at the period locus and two other X-linked genes (neon-transient-A and E74A) than at three autosomal genes (Xdh, Adh and RC98). Using a modification of the HKA test, which uses fixed differences between the semispecies and a test based on differences in Fst among loci, we show that the greater differentiation of the X-linked loci compared with the autosomal loci is inconsistent with a neutral model of molecular evolution. We explore several evolutionary scenarios by computer simulation, including differential migration of X and autosomal genes, very low levels of migration among the semispecies, selective sweeps, and background selection, and conclude that X-linked selective sweeps in at least two of the semispecies are the best explanation for the data. This evidence that natural selection acted on the X-chromosome suggests that another X-linked trait, mating song differences among the semispecies, may have been the target of selection.

scholarly journals Different historical generation intervals in human populations inferred from Neanderthal fragment lengths and patterns of mutation accumulation

2021 ◽  
Author(s):  
Moisès Coll Macià ◽  
Laurits Skov ◽  
Benjamin Marco Peter ◽  
Mikkel Heide Schierup
Keyword(s):  
Fragment Length ◽  
Human Populations ◽  
Female Age ◽  
Generation Interval ◽  
The Past ◽  
Geographical Regions ◽  
Neanderthal Admixture ◽  
Rate Of Decay ◽  
Out Of Africa ◽  
Insight Into

AbstractAfter the main out-of-Africa event, humans interbred with Neanderthals leaving 1-2% of Neanderthal DNA scattered in small fragments in all non-African genomes today1,2. Here we investigate the size distribution of these fragments in non-African genomes3. We find consistent differences in fragment length distributions across Eurasia with 11% longer fragments in East Asians than in West Eurasians. By comparing extant populations and ancient samples, we show that these differences are due to a different rate of decay in length by recombination since the Neanderthal admixture. In line with this, we observe a strong correlation between the average fragment length and the accumulation of derived mutations, similar to what is expected by changing the ages at reproduction as estimated from trio studies4. Altogether, our results suggest consistent differences in the generation interval across Eurasia, by up to 20% (e.g. 25 versus 30 years), over the past 40,000 years. We use sex-specific accumulations of derived alleles to infer how these changes in generation intervals between geographical regions could have been mainly driven by shifts in either male or female age of reproduction, or both. We also find that previously reported variation in the mutational spectrum5 may be largely explained by changes to the generation interval and not by changes to the underlying mutational mechanism. We conclude that Neanderthal fragment lengths provide unique insight into differences of a key demographic parameter among human populations over the recent history.

High frequencies in African and non-African populations of independent mutations in the mannose binding protein gene

1992 ◽  
Vol 1 (9) ◽  
pp. 709-715 ◽  
Author(s):  
R. J. Lipscombe ◽  
M. Sumiya ◽  
A. V. S. Hill ◽  
Y. L. Lau ◽  
R. J. Levinsky ◽  
...  
Keyword(s):  
Protein Gene ◽  
Binding Protein ◽  
High Frequencies ◽  
Mannose Binding Protein ◽  
African Populations ◽  
Mannose Binding ◽  
Binding Protein Gene

The 5q31 Region in Two African Populations as a Facet of Natural Selection by Infectious Diseases

2013 ◽  
Vol 49 (2) ◽  
pp. 279-288
Author(s):  
A. A. M. Elhassan ◽  
A. A. Hussein ◽  
H. S. Mohamed ◽  
K. Rockett ◽  
D. Kwiatkowski ◽  
...  
Keyword(s):  
Natural Selection ◽  
Infectious Diseases ◽  
African Populations

scholarly journals Genome-wide scans provide evidence for positive selection of genes implicated in Lassa fever

2012 ◽  
Vol 367 (1590) ◽  
pp. 868-877 ◽  
Author(s):  
Kristian G. Andersen ◽  
Ilya Shylakhter ◽  
Shervin Tabrizi ◽  
Sharon R. Grossman ◽  
Christian T. Happi ◽  
...  
Keyword(s):  
Natural Selection ◽  
Positive Selection ◽  
Lassa Fever ◽  
West African ◽  
Lassa Virus ◽  
Genome Wide ◽  
African Populations ◽  
Genome Wide Data ◽  
Differential Gene ◽  
Selection Of

Rapidly evolving viruses and other pathogens can have an immense impact on human evolution as natural selection acts to increase the prevalence of genetic variants providing resistance to disease. With the emergence of large datasets of human genetic variation, we can search for signatures of natural selection in the human genome driven by such disease-causing microorganisms. Based on this approach, we have previously hypothesized that Lassa virus (LASV) may have been a driver of natural selection in West African populations where Lassa haemorrhagic fever is endemic. In this study, we provide further evidence for this notion. By applying tests for selection to genome-wide data from the International Haplotype Map Consortium and the 1000 Genomes Consortium, we demonstrate evidence for positive selection in LARGE and interleukin 21 ( IL21 ), two genes implicated in LASV infectivity and immunity. We further localized the signals of selection, using the recently developed composite of multiple signals method, to introns and putative regulatory regions of those genes. Our results suggest that natural selection may have targeted variants giving rise to alternative splicing or differential gene expression of LARGE and IL21 . Overall, our study supports the hypothesis that selective pressures imposed by LASV may have led to the emergence of particular alleles conferring resistance to Lassa fever, and opens up new avenues of research pursuit.

scholarly journals Evidence for Natural Selection and Ethnic Diversity at the Adenylate cyclase 3 Gene Associated with Obesity and Type 2 Diabetes

2020 ◽  
Author(s):  
ISSEI YOSHIUCHI
Keyword(s):  
Type 2 Diabetes ◽  
Natural Selection ◽  
Adenylate Cyclase ◽  
Ethnic Diversity ◽  
European Ancestry ◽  
Loss Of Function ◽  
Obesity And Diabetes ◽  
African Populations ◽  
Diabetes And Obesity

Abstract Background: Diabetes and obesity cause serious complications worldwide, including stroke and cardiovascular disease, and are a global health burden. Diabetes is strongly related with obesity and both are significantly heritable. The prevalence of diabetes and obesity are higher in African populations than in European and Asian populations. In human evolution, natural selection is a key process of genetic survival over generations. Thus, the selection for diabetes- and obesity-related genes is a key mechanism for survival during times of feast and famine. Loss-of-function variations in the adenylate cyclase 3 ( ADCY3 ) gene are associated with obesity and diabetes, while mutations in ADCY3 are also associated with childhood obesity. ADCY3 -deficient mice showed severe obesity, impaired insulin sensitivity, and reduced physical activity. Here, we researched evidence for natural selection at ADCY3 . Methods: We used a three-step genetic method to identify natural selection at ADCY3 using data on four populations from the 1000 Genomes Project and HapMap: Utah residents with Northern and Western European ancestry (CEU), the Yoruba in Ibadan, Nigeria (YRI), Han Chinese in Beijing (CHB) and Japanese in Tokyo (JPT). First we used Wright’s F-statistics (Fst) as a measure of population differentiation to find ethnic diversity at ADCY3 . We then used a long-range haplotype (LRH) test to find significant long haplotypes, and then the integrated haplotype score (iHS) to find natural selection at ADCY3 . Results: We observed high Fst values and significant ethnic diversity at four ADCY3 body mass index (BMI)-associated variations (rs7586879, rs6545814, rs11676272 and rs10182181) between the non-African and African populations. Both LRH and iHS also provided evidence for natural selection at ADCY3 . Conclusions: These observations show evidence for natural selection and ethnic diversity at ADCY3 . Further exploration into the evolution of obesity- and Type 2 diabetes-associated genes is needed.

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