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1.  A Draft Sequence of the Neandertal Genome 
Science (New York, N.Y.)  2010;328(5979):710-722.
Neandertals, the closest evolutionary relatives of present-day humans, lived in large parts of Europe and western Asia before disappearing 30,000 years ago. We present a draft sequence of the Neandertal genome composed of more than 4 billion nucleotides from three individuals. Comparisons of the Neandertal genome to the genomes of five present-day humans from different parts of the world identify a number of genomic regions that may have been affected by positive selection in ancestral modern humans, including genes involved in metabolism and in cognitive and skeletal development. We show that Neandertals shared more genetic variants with present-day humans in Eurasia than with present-day humans in sub-Saharan Africa, suggesting that gene flow from Neandertals into the ancestors of non-Africans occurred before the divergence of Eurasian groups from each other.
PMCID: PMC5100745  PMID: 20448178
2.  The genetic history of Ice Age Europe 
Nature  2016;534(7606):200-205.
Modern humans arrived in Europe ~45,000 years ago, but little is known about their genetic composition before the start of farming ~8,500 years ago. We analyze genome-wide data from 51 Eurasians from ~45,000-7,000 years ago. Over this time, the proportion of Neanderthal DNA decreased from 3–6% to around 2%, consistent with natural selection against Neanderthal variants in modern humans. Whereas the earliest modern humans in Europe did not contribute substantially to present-day Europeans, all individuals between ~37,000 and ~14,000 years ago descended from a single founder population which forms part of the ancestry of present-day Europeans. A ~35,000 year old individual from northwest Europe represents an early branch of this founder population which was then displaced across a broad region, before reappearing in southwest Europe during the Ice Age ~19,000 years ago. During the major warming period after ~14,000 years ago, a new genetic component related to present-day Near Easterners appears in Europe. These results document how population turnover and migration have been recurring themes of European pre-history.
PMCID: PMC4943878  PMID: 27135931
3.  Massive migration from the steppe was a source for Indo-European languages in Europe 
Nature  2015;522(7555):207-211.
We generated genome-wide data from 69 Europeans who lived between 8,000–3,000 years ago by enriching ancient DNA libraries for a target set of almost 400,000 polymorphisms. Enrichment of these positions decreases the sequencing required for genome-wide ancient DNA analysis by a median of around 250-fold, allowing us to study an order of magnitude more individuals than previous studies1–8 and to obtain new insights about the past. We show that the populations of Western and Far Eastern Europe followed opposite trajectories between 8,000–5,000 years ago. At the beginning of the Neolithic period in Europe, 8,000–7,000 years ago, closely related groups of early farmers appeared in Germany, Hungary and Spain, different from indigenous hunter-gatherers, whereas Russia was inhabited by a distinctive population of hunter-gatherers with high affinity to a 24,000-year-old Siberian6. By 6,000–5,000 years ago, farmers throughout much of Europe had more hunter-gatherer ancestry than their predecessors, but in Russia, the Yamnaya steppe herders of this time were descended not only from the preceding eastern European hunter-gatherers, but also from a population of Near Eastern ancestry. Western and Eastern Europe came into contact 4,500 years ago, as the Late Neolithic Corded Ware people from Germany traced 75% of their ancestry to the Yamnaya, documenting a massive migration into the heartland of Europe from its eastern periphery. This steppe ancestry persisted in all sampled central Europeans until at least 3,000 years ago, and is ubiquitous in present-day Europeans. These results provide support for a steppe origin9 of at least some of the Indo-European languages of Europe.
PMCID: PMC5048219  PMID: 25731166
4.  A revised timescale for human evolution based on ancient mitochondrial genomes 
Current biology : CB  2013;23(7):553-559.
Recent analyses of de novo DNA mutations in modern humans have suggested a nuclear substitution rate that is approximately half that of previous estimates based on fossil calibration. This result has led to suggestions that major events in human evolution occurred far earlier than previously thought.
Here we use mitochondrial genome sequences from 10 securely dated ancient modern humans spanning 40,000 years as calibration points for the mitochondrial clock, thus yielding a direct estimate of the mitochondrial substitution rate. Our clock yields mitochondrial divergence times that are in agreement with earlier estimates based on calibration points derived from either fossils or archaeological material. In particular, our results imply a separation of non-Africans from the most closely related sub-Saharan African mitochondrial DNAs (haplogroup L3) of less than 62,000-95,000 years ago.
Though single loci like mitochondrial DNA (mtDNA) can only provide biased estimates of population split times, they can provide valid upper bounds; our results exclude most of the older dates for African and non-African split times recently suggested by de novo mutation rate estimates in the nuclear genome.
PMCID: PMC5036973  PMID: 23523248
5.  Genetic evidence for two founding populations of the Americas 
Nature  2015;525(7567):104-108.
Genetic studies have been consistent with a single common origin of Native American groups from Central and South America1-4. However, some morphological studies have suggested a more complex picture, whereby the northeast Asian affinities of present-day Native Americans contrast with a distinctive morphology seen in some of the earliest American skeletons, which share traits with present-day Australasians (indigenous groups in Australia, Melanesia, and island southeast Asia)5-8. Here we analyze genome-wide data to show that some Amazonian Native Americans descend partly from a Native American founding population that carried ancestry more closely related to indigenous Australians, New Guineans and Andaman Islanders than to any present-day Eurasians or Native Americans. This signature is not present to the same extent or at all in present-day Northern and Central Americans or a ~12,600 year old Clovis genome, suggesting a more diverse set of founding populations of the Americas than previously accepted.
PMCID: PMC4982469  PMID: 26196601
6.  Genome-wide patterns of selection in 230 ancient Eurasians 
Nature  2015;528(7583):499-503.
Ancient DNA makes it possible to directly witness natural selection by analyzing samples from populations before, during and after adaptation events. Here we report the first scan for selection using ancient DNA, capitalizing on the largest genome-wide dataset yet assembled: 230 West Eurasians dating to between 6500 and 1000 BCE, including 163 with newly reported data. The new samples include the first genome-wide data from the Anatolian Neolithic culture whose genetic material we extracted from the DNA-rich petrous bone and who we show were members of the population that was the source of Europe’s first farmers. We also report a complete transect of the steppe region in Samara between 5500 and 1200 BCE that allows us to recognize admixture from at least two external sources into steppe populations during this period. We detect selection at loci associated with diet, pigmentation and immunity, and two independent episodes of selection on height.
PMCID: PMC4918750  PMID: 26595274
7.  Complete genomes reveal signatures of demographic and genetic declines in the woolly mammoth 
Current biology : CB  2015;25(10):1395-1400.
The processes leading up to species extinctions are typically characterized by prolonged declines in population size and geographic distribution, followed by a phase in which populations are very small and may be subject to intrinsic threats, including loss of genetic diversity and inbreeding [1]. However, whether such genetic factors have had an impact on species prior to their extinction is unclear [2, 3]; examining this would require a detailed reconstruction of a species’ demographic history as well as changes in genome-wide diversity leading up to its extinction. Here, we present high-quality complete genome sequences from two woolly mammoths (Mammuthus primigenius). The first mammoth was sequenced at 17.1-fold coverage, and dates to ~4,300 years before present, constituting one of the last surviving individuals on Wrangel Island. The second mammoth, sequenced at 11.2-fold coverage, was obtained from a ~44,800 year old specimen from the Late Pleistocene population in northeastern Siberia. The demographic trajectories inferred from the two genomes are qualitatively similar and reveal a population bottleneck during the Middle or Early Pleistocene, and a more recent severe decline in the ancestors of the Wrangel mammoth at the end of the last glaciation. A comparison of the two genomes shows that the Wrangel mammoth has a 20% reduction in heterozygosity as well as a 28-fold increase in the fraction of the genome that is comprised of runs of homozygosity. We conclude that the population on Wrangel Island, which was the last surviving woolly mammoth population, was subject to reduced genetic diversity shortly before it became extinct.
PMCID: PMC4439331  PMID: 25913407
8.  Ancient mitochondrial DNA provides high-resolution time scale of the peopling of the Americas 
Science Advances  2016;2(4):e1501385.
Native American population history is reexamined using a large data set of pre-Columbian mitochondrial genomes.
The exact timing, route, and process of the initial peopling of the Americas remains uncertain despite much research. Archaeological evidence indicates the presence of humans as far as southern Chile by 14.6 thousand years ago (ka), shortly after the Pleistocene ice sheets blocking access from eastern Beringia began to retreat. Genetic estimates of the timing and route of entry have been constrained by the lack of suitable calibration points and low genetic diversity of Native Americans. We sequenced 92 whole mitochondrial genomes from pre-Columbian South American skeletons dating from 8.6 to 0.5 ka, allowing a detailed, temporally calibrated reconstruction of the peopling of the Americas in a Bayesian coalescent analysis. The data suggest that a small population entered the Americas via a coastal route around 16.0 ka, following previous isolation in eastern Beringia for ~2.4 to 9 thousand years after separation from eastern Siberian populations. Following a rapid movement throughout the Americas, limited gene flow in South America resulted in a marked phylogeographic structure of populations, which persisted through time. All of the ancient mitochondrial lineages detected in this study were absent from modern data sets, suggesting a high extinction rate. To investigate this further, we applied a novel principal components multiple logistic regression test to Bayesian serial coalescent simulations. The analysis supported a scenario in which European colonization caused a substantial loss of pre-Columbian lineages.
PMCID: PMC4820370  PMID: 27051878
Ancient DNA; Native America; colonization; Beringia
9.  EHDViz: clinical dashboard development using open-source technologies 
BMJ Open  2016;6(3):e010579.
To design, develop and prototype clinical dashboards to integrate high-frequency health and wellness data streams using interactive and real-time data visualisation and analytics modalities.
Materials and methods
We developed a clinical dashboard development framework called electronic healthcare data visualization (EHDViz) toolkit for generating web-based, real-time clinical dashboards for visualising heterogeneous biomedical, healthcare and wellness data. The EHDViz is an extensible toolkit that uses R packages for data management, normalisation and producing high-quality visualisations over the web using R/Shiny web server architecture. We have developed use cases to illustrate utility of EHDViz in different scenarios of clinical and wellness setting as a visualisation aid for improving healthcare delivery.
Using EHDViz, we prototyped clinical dashboards to demonstrate the contextual versatility of EHDViz toolkit. An outpatient cohort was used to visualise population health management tasks (n=14 221), and an inpatient cohort was used to visualise real-time acuity risk in a clinical unit (n=445), and a quantified-self example using wellness data from a fitness activity monitor worn by a single individual was also discussed (n-of-1). The back-end system retrieves relevant data from data source, populates the main panel of the application and integrates user-defined data features in real-time and renders output using modern web browsers. The visualisation elements can be customised using health features, disease names, procedure names or medical codes to populate the visualisations. The source code of EHDViz and various prototypes developed using EHDViz are available in the public domain at
Collaborative data visualisations, wellness trend predictions, risk estimation, proactive acuity status monitoring and knowledge of complex disease indicators are essential components of implementing data-driven precision medicine. As an open-source visualisation framework capable of integrating health assessment, EHDViz aims to be a valuable toolkit for rapid design, development and implementation of scalable clinical data visualisation dashboards.
PMCID: PMC4809078  PMID: 27013597
early warning systems; biomedical informatics; data visuzalization; clinical decision systems; clinical dashboard
10.  The genome sequence of a 45,000-year-old modern human from western Siberia 
Nature  2014;514(7523):445-449.
We present a high-quality genome sequence of a ~45,000-year-old modern human male from Siberia. This individual derives from a population that lived prior to – or simultaneously with – the separation of the populations in western and eastern Eurasia and carries a similar amount of Neandertal ancestry as present-day Eurasians. However, the genomic segments of Neandertal ancestry are substantially longer than those observed in present-day individuals, indicating that Neandertal gene flow into the ancestors of this individual occurred 7,000–13,000 years before he lived. We estimate an autosomal mutation rate of 0.4–0.6×10−9/site/year and a Y chromosomal mutation rate of 0.7–0.9×10−9/site/year based on the additional substitutions that have occurred in present-day non-Africans compared to this genome, and a mitochondrial mutation rate of 1.8–3.2 × 10−8/site/year based on the age of the bone.
PMCID: PMC4753769  PMID: 25341783
11.  An early modern human from Romania with a recent Neanderthal ancestor 
Nature  2015;524(7564):216-219.
Neanderthals are thought to have disappeared in Europe ~39,000–41,000 years ago but they have contributed one to three percent of the DNA of present-day people in Eurasia1. Here, we analyze DNA from a 37,000–42,000-year-old2 modern human from Peştera cu Oase, Romania. Although the specimen contains small amounts of human DNA, we use an enrichment strategy to isolate sites that are informative about its relationship to Neanderthals and present-day humans. We find that on the order of six to nine percent of the genome of the Oase individual is derived from Neanderthals, more than any other modern human sequenced to date. Three chromosomal segments of Neanderthal ancestry are over 50 centimorgans in size, indicating that this individual had a Neanderthal ancestor as recently as four to six generations back. However, the Oase individual does not share more alleles with later Europeans than with East Asians, suggesting that the Oase population did not contribute substantially to later humans in Europe.
PMCID: PMC4537386  PMID: 26098372
12.  Partial uracil–DNA–glycosylase treatment for screening of ancient DNA 
The challenge of sequencing ancient DNA has led to the development of specialized laboratory protocols that have focused on reducing contamination and maximizing the number of molecules that are extracted from ancient remains. Despite the fact that success in ancient DNA studies is typically obtained by screening many samples to identify a promising subset, ancient DNA protocols have not, in general, focused on reducing the time required to screen samples. We present an adaptation of a popular ancient library preparation method that makes screening more efficient. First, the DNA extract is treated using a protocol that causes characteristic ancient DNA damage to be restricted to the terminal nucleotides, while nearly eliminating it in the interior of the DNA molecules, allowing a single library to be used both to test for ancient DNA authenticity and to carry out population genetic analysis. Second, the DNA molecules are ligated to a unique pair of barcodes, which eliminates undetected cross-contamination from this step onwards. Third, the barcoded library molecules include incomplete adapters of short length that can increase the specificity of hybridization-based genomic target enrichment. The adapters are completed just before sequencing, so the same DNA library can be used in multiple experiments, and the sequences distinguished. We demonstrate this protocol on 60 ancient human samples.
PMCID: PMC4275898  PMID: 25487342
ancient DNA; authenticity; library preparation; barcodes; flexibility; target capture
13.  African Ancestry Analysis and Admixture Genetic Mapping for Proliferative Diabetic Retinopathy in African Americans 
To examine the relationship between proportion of African ancestry (PAA) and proliferative diabetic retinopathy (PDR) and to identify genetic loci associated with PDR using admixture mapping in African Americans with type 2 diabetes (T2D).
Between 1993 and 2013, 1440 participants enrolled in four different studies had fundus photographs graded using the Early Treatment Diabetic Retinopathy Study scale. Cases (n = 305) had PDR while controls (n = 1135) had nonproliferative diabetic retinopathy (DR) or no DR. Covariates included diabetes duration, hemoglobin A1C, systolic blood pressure, income, and education. Genotyping was performed on the Affymetrix platform. The association between PAA and PDR was evaluated using logistic regression. Genome-wide admixture scanning was performed using ANCESTRYMAP software.
In the univariate analysis, PDR was associated with increased PAA (odds ratio [OR] = 1.36, 95% confidence interval [CI] = 1.16–1.59, P = 0.0002). In multivariate regression adjusting for traditional DR risk factors, income and education, the association between PAA and PDR was attenuated and no longer significant (OR = 1.21, 95% CI = 0.59–2.47, P = 0.61). For the admixture analyses, the maximum genome-wide score was 1.44 on chromosome 1.
In this largest study of PDR in African Americans with T2D to date, an association between PAA and PDR is not present after adjustment for clinical, demographic, and socioeconomic factors. No genome-wide significant locus (defined as having a locus-genome statistic > 5) was identified with admixture analysis. Further analyses with even larger sample sizes are needed to definitively assess if any admixture signal for DR is present.
In African Americans with type 2 diabetes, proportion of African ancestry was associated with proliferative diabetic retinopathy (PDR) but the association was no longer present with adjustment for clinical/socioeconomic variables. No genome-wide significant loci were found with admixture scanning.
PMCID: PMC4477259  PMID: 26098467
genetics; diabetic retinopathy; proliferative diabetic retinopathy; African Americans; admixture; ancestry
14.  Calibrating the Human Mutation Rate via Ancestral Recombination Density in Diploid Genomes 
PLoS Genetics  2015;11(11):e1005550.
The human mutation rate is an essential parameter for studying the evolution of our species, interpreting present-day genetic variation, and understanding the incidence of genetic disease. Nevertheless, our current estimates of the rate are uncertain. Most notably, recent approaches based on counting de novo mutations in family pedigrees have yielded significantly smaller values than classical methods based on sequence divergence. Here, we propose a new method that uses the fine-scale human recombination map to calibrate the rate of accumulation of mutations. By comparing local heterozygosity levels in diploid genomes to the genetic distance scale over which these levels change, we are able to estimate a long-term mutation rate averaged over hundreds or thousands of generations. We infer a rate of 1.61 ± 0.13 × 10−8 mutations per base per generation, which falls in between phylogenetic and pedigree-based estimates, and we suggest possible mechanisms to reconcile our estimate with previous studies. Our results support intermediate-age divergences among human populations and between humans and other great apes.
Author Summary
The rate at which new heritable mutations occur in the human genome is a fundamental parameter in population and evolutionary genetics. However, recent direct family-based estimates of the mutation rate have consistently been much lower than previous results from comparisons with other great ape species. Because split times of species and populations estimated from genetic data are often inversely proportional to the mutation rate, resolving the disagreement would have important implications for understanding human evolution. In our work, we apply a new technique that uses mutations that have accumulated over many generations on either copy of a chromosome in an individual’s genome. Instead of an external reference point, we rely on fine-scale knowledge of the human recombination rate to calibrate the long-term mutation rate. Our procedure accounts for possible errors found in real data, and we also show that it is robust to a range of model violations. Using eight diploid genomes from non-African individuals, we infer a rate of 1.61 ± 0.13 × 10−8 single-nucleotide changes per base per generation, which is intermediate between most phylogenetic and pedigree-based estimates. Thus, our estimate implies reasonable, intermediate-age population split times across a range of time scales.
PMCID: PMC4642934  PMID: 26562831
15.  Global diversity, population stratification, and selection of human copy number variation 
Science (New York, N.Y.)  2015;349(6253):aab3761.
In order to explore the diversity and selective signatures of duplication and deletion human copy number variants (CNVs), we sequenced 236 individuals from 125 distinct human populations. We observed that duplications exhibit fundamentally different population genetic and selective signatures than deletions and are more likely to be stratified between human populations. Through reconstruction of the ancestral human genome, we identify megabases of DNA lost in different human lineages and pinpoint large duplications that introgressed from the extinct Denisova lineage now found at high frequency exclusively in Oceanic populations. We find that the proportion of CNV base pairs to single nucleotide variant base pairs is greater among non-Africans than it is among African populations, but we conclude that this difference is likely due to unique aspects of non-African population history as opposed to differences in CNV load.
PMCID: PMC4568308  PMID: 26249230
16.  Toward a new history and geography of human genes informed by ancient DNA 
Trends in genetics : TIG  2014;30(9):377-389.
Genetic information contains a record of the history of our species, and technological advances have transformed our ability to access this record. Many studies have used genome-wide data from populations today to learn about the peopling of the globe and subsequent adaptation to local conditions. Implicit in this research is the assumption that the geographic locations of people today are informative about the geographic locations of their ancestors in the distant past. However, it is now clear that long-range migration, admixture and population replacement subsequent to the initial out-of-Africa expansion have altered the genetic structure of most of the world’s human populations. In light of this, we argue that it is time to critically re-evaluate current models of the peopling of the globe, as well as the importance of natural selection in determining the geographic distribution of phenotypes. We specifically highlight the transformative potential of ancient DNA. By accessing the genetic make-up of populations living at archaeologically-known times and places, ancient DNA makes it possible to directly track migrations and responses to natural selection.
PMCID: PMC4163019  PMID: 25168683
17.  Dominance of Deleterious Alleles Controls the Response to a Population Bottleneck 
PLoS Genetics  2015;11(8):e1005436.
Population bottlenecks followed by re-expansions have been common throughout history of many populations. The response of alleles under selection to such demographic perturbations has been a subject of great interest in population genetics. On the basis of theoretical analysis and computer simulations, we suggest that this response qualitatively depends on dominance. The number of dominant or additive deleterious alleles per haploid genome is expected to be slightly increased following the bottleneck and re-expansion. In contrast, the number of completely or partially recessive alleles should be sharply reduced. Changes of population size expose differences between recessive and additive selection, potentially providing insight into the prevalence of dominance in natural populations. Specifically, we use a simple statistic, BR≡∑xipop1/∑xjpop2, where x i represents the derived allele frequency, to compare the number of mutations in different populations, and detail its functional dependence on the strength of selection and the intensity of the population bottleneck. We also provide empirical evidence showing that gene sets associated with autosomal recessive disease in humans may have a B R indicative of recessive selection. Together, these theoretical predictions and empirical observations show that complex demographic history may facilitate rather than impede inference of parameters of natural selection.
Author Summary
Dominance has played a central role in classical genetics since its inception. However, the effect of dominance introduces substantial technical complications into theoretical models describing dynamics of alleles in populations. As a result, dominance is often ignored in population genetic models. Statistical tests for selection built on these models do not discriminate between recessive and additive alleles. We show that historical changes in population size can provide a way to differentiate between recessive and additive selection. Our analysis compares two sub-populations with different demographic histories. History of our own species provides plenty of examples of sub-populations that went through population bottlenecks followed by re-expansions. We show that demographic differences, which generally complicate the analysis, can instead aid in the inference of features of natural selection.
PMCID: PMC4552954  PMID: 26317225
18.  No evidence that selection has been less effective at removing deleterious mutations in Europeans than in Africans 
Nature genetics  2015;47(2):126-131.
Non-African populations have experienced size reductions in the time since their split from West Africans, leading to the hypothesis that natural selection to remove weakly deleterious mutations has been less effective in the history of non-Africans. To test this hypothesis, we measured the per-genome accumulation of non-synonymous substitutions across diverse pairs of populations. We find no evidence for a higher load of deleterious mutations in non-Africans. However, we detect significant differences among more divergent populations, as archaic Denisovans have accumulated non-synonymous mutations faster than either modern humans or Neanderthals. To reconcile these findings with patterns that have been interpreted as evidence of less effective removal of deleterious mutations in non-Africans than in West Africans, we use simulations to show that the observed patterns are not likely to reflect changes in the effectiveness of selection after the populations split, and instead are likely to be driven by other population genetic factors.
PMCID: PMC4310772  PMID: 25581429
19.  A Re-Appraisal of the Early Andean Human Remains from Lauricocha in Peru 
PLoS ONE  2015;10(6):e0127141.
The discovery of human remains from the Lauricocha cave in the Central Andean highlands in the 1960’s provided the first direct evidence for human presence in the high altitude Andes. The skeletons found at this site were ascribed to the Early to Middle Holocene and represented the oldest known population of Western South America, and thus were used in several studies addressing the early population history of the continent. However, later excavations at Lauricocha led to doubts regarding the antiquity of the site. Here, we provide new dating, craniometric, and genetic evidence for this iconic site. We obtained new radiocarbon dates, generated complete mitochondrial genomes and nuclear SNP data from five individuals, and re-analyzed the human remains of Lauricocha to revise the initial morphological and craniometric analysis conducted in the 1960’s. We show that Lauricocha was indeed occupied in the Early to Middle Holocene but the temporal spread of dates we obtained from the human remains show that they do not qualify as a single contemporaneous population. However, the genetic results from five of the individuals fall within the spectrum of genetic diversity observed in pre-Columbian and modern Native Central American populations.
PMCID: PMC4464891  PMID: 26061688
20.  Leveraging population admixture to explain missing heritability of complex traits 
Nature genetics  2014;46(12):1356-1362.
Despite recent progress on estimating the heritability explained by genotyped SNPs (hg2), a large gap between hg2 and estimates of total narrow-sense heritability (h2) remains. Explanations for this gap include rare variants, or upward bias in family-based estimates of h2 due to shared environment or epistasis. We estimate h2 from unrelated individuals in admixed populations by first estimating the heritability explained by local ancestry (hγ2). We show that hγ2 = 2FSTCθ(1−θ)h2, where FSTC measures frequency differences between populations at causal loci and θ is the genome-wide ancestry proportion. Our approach is not susceptible to biases caused by epistasis or shared environment. We examined 21,497 African Americans from three cohorts, analyzing 13 phenotypes. For height and BMI, we obtained h2 estimates of 0.55 ± 0.09 and 0.23 ± 0.06, respectively, which are larger than estimates of hg2 in these and other data, but smaller than family-based estimates of h2.
PMCID: PMC4244251  PMID: 25383972
21.  Ancestry Informative Marker Panels for African Americans Based on Subsets of Commercially Available SNP Arrays 
Genetic epidemiology  2011;35(1):80-83.
Admixture mapping is a widely used method for localizing disease genes in African Americans. Most current methods for inferring ancestry at each locus in the genome use a few thousand single nucleotide polymorphisms (SNPs) that are very different in frequency between West Africans and European Americans, and that are required to not be in linkage disequilibrium in the ancestral populations. Modern SNP arrays provide data on hundreds of thousands of SNPs per sample, and to use these to infer ancestry, using many of the standard methods, it is necessary to choose subsets of the SNPs for analysis. Here we present panels of about 4,300 ancestry informative markers (AIMs) that are subsets respectively of SNPs on the Illumina 1 M, Illumina 650, Illumina 610, Affymetrix 6.0 and Affymetrix 5.0 arrays. To validate the usefulness of these panels, we applied them to samples that are different from the ones used to select the SNPs. The panels provide about 80% of the maximum information about African or European ancestry, even with up to 10% missing data.
PMCID: PMC4386999  PMID: 21181899
ancestry informative markers; admixture mapping; African American disease studies
22.  Non-crossover gene conversions show strong GC bias and unexpected clustering in humans 
eLife  null;4:e04637.
Although the past decade has seen tremendous progress in our understanding of fine-scale recombination, little is known about non-crossover (NCO) gene conversion. We report the first genome-wide study of NCO events in humans. Using SNP array data from 98 meioses, we identified 103 sites affected by NCO, of which 50/52 were confirmed in sequence data. Overlap with double strand break (DSB) hotspots indicates that most of the events are likely of meiotic origin. We estimate that a site is involved in a NCO at a rate of 5.9 × 10−6/bp/generation, consistent with sperm-typing studies, and infer that tract lengths span at least an order of magnitude. Observed NCO events show strong allelic bias at heterozygous AT/GC SNPs, with 68% (58–78%) transmitting GC alleles (p = 5 × 10−4). Strikingly, in 4 of 15 regions with resequencing data, multiple disjoint NCO tracts cluster in close proximity (∼20–30 kb), a phenomenon not previously seen in mammals.
eLife digest
The genetic information inside our cells is stored in the form of chromosomes, which are carefully packaged strands of DNA. Most human cells contain a pair of each chromosome: one inherited from the mother and another from the father. Typically, when a human cell divides, it duplicates all of its chromosomes and then places one copy of each into the two new cells.
However, a different process—known as ‘meiosis’—occurs when a human cell divides to make the cells involved in sexual reproduction (i.e., egg cells in females and sperm cells in males). First, the cell duplicates all of its chromosomes as before, but then it pairs the chromosomes originally from the mother with the equivalent chromosomes from the father. These paired chromosomes then swap sections of DNA. Next, the cell divides, and the resulting cells divide again; this produces four new cells that each contain a single, unique copy of every chromosome.
In the process of swapping sections of DNA between chromosomes, the DNA molecule inside the chromosome is broken and different sections of DNA are then joined together. This can occur by one of two methods: ‘crossover events’ that produce a final chromosome made up of long sequences from each of the contributing chromosomes; and ‘non-crossover events’, where only a small section of DNA is swapped between the chromosomes.
Research has tended to focus on DNA breaks and crossover events. Now, Williams et al. have looked at the genetic sequences transmitted by both parents to 49 humans—revealing information about a total of 98 meioses—and scoured them for evidence of non-crossover events. In addition to finding 103 sites where these events occurred, Williams et al. discovered that non-crossover events are more frequent around sites where crossover events also have a higher frequency. This suggests that the mechanism that initiates non-crossover events is shared with crossovers, and that non-crossover events primarily occur during meiosis. Unexpectedly, in some areas non-crossover events were found close to each other in ‘clusters’, which had not previously been seen in humans.
Non-crossover events will only produce an observable change if the chromosomes involved have differences in the sequence of the DNA section that is swapped between them. The number of such variable genetic positions that non-crossover events affect in a generation is roughly the same number as the number of newly generated random mutations to the DNA sequence in a generation. Examining the DNA sequences transferred during non-crossover events also shows that two different types of DNA bases (cytosine and guanine) are more likely to be transmitted by a non-crossover event than are the other two bases (adenine and thymine). This bias indicates that non-crossover events are an important factor in driving genome evolution. In the future, sequencing the entire genome—the total genetic material—of many different people could provide further insights into non-crossover events in humans.
PMCID: PMC4404656  PMID: 25806687
recombination; non-crossover; gene conversion; GC-bias; complex crossover; haplotypes; human
23.  Ancient human genomes suggest three ancestral populations for present-day Europeans 
Lazaridis, Iosif | Patterson, Nick | Mittnik, Alissa | Renaud, Gabriel | Mallick, Swapan | Kirsanow, Karola | Sudmant, Peter H. | Schraiber, Joshua G. | Castellano, Sergi | Lipson, Mark | Berger, Bonnie | Economou, Christos | Bollongino, Ruth | Fu, Qiaomei | Bos, Kirsten I. | Nordenfelt, Susanne | Li, Heng | de Filippo, Cesare | Prüfer, Kay | Sawyer, Susanna | Posth, Cosimo | Haak, Wolfgang | Hallgren, Fredrik | Fornander, Elin | Rohland, Nadin | Delsate, Dominique | Francken, Michael | Guinet, Jean-Michel | Wahl, Joachim | Ayodo, George | Babiker, Hamza A. | Bailliet, Graciela | Balanovska, Elena | Balanovsky, Oleg | Barrantes, Ramiro | Bedoya, Gabriel | Ben-Ami, Haim | Bene, Judit | Berrada, Fouad | Bravi, Claudio M. | Brisighelli, Francesca | Busby, George B. J. | Cali, Francesco | Churnosov, Mikhail | Cole, David E. C. | Corach, Daniel | Damba, Larissa | van Driem, George | Dryomov, Stanislav | Dugoujon, Jean-Michel | Fedorova, Sardana A. | Romero, Irene Gallego | Gubina, Marina | Hammer, Michael | Henn, Brenna M. | Hervig, Tor | Hodoglugil, Ugur | Jha, Aashish R. | Karachanak-Yankova, Sena | Khusainova, Rita | Khusnutdinova, Elza | Kittles, Rick | Kivisild, Toomas | Klitz, William | Kučinskas, Vaidutis | Kushniarevich, Alena | Laredj, Leila | Litvinov, Sergey | Loukidis, Theologos | Mahley, Robert W. | Melegh, Béla | Metspalu, Ene | Molina, Julio | Mountain, Joanna | Näkkäläjärvi, Klemetti | Nesheva, Desislava | Nyambo, Thomas | Osipova, Ludmila | Parik, Jüri | Platonov, Fedor | Posukh, Olga | Romano, Valentino | Rothhammer, Francisco | Rudan, Igor | Ruizbakiev, Ruslan | Sahakyan, Hovhannes | Sajantila, Antti | Salas, Antonio | Starikovskaya, Elena B. | Tarekegn, Ayele | Toncheva, Draga | Turdikulova, Shahlo | Uktveryte, Ingrida | Utevska, Olga | Vasquez, René | Villena, Mercedes | Voevoda, Mikhail | Winkler, Cheryl | Yepiskoposyan, Levon | Zalloua, Pierre | Zemunik, Tatijana | Cooper, Alan | Capelli, Cristian | Thomas, Mark G. | Ruiz-Linares, Andres | Tishkoff, Sarah A. | Singh, Lalji | Thangaraj, Kumarasamy | Villems, Richard | Comas, David | Sukernik, Rem | Metspalu, Mait | Meyer, Matthias | Eichler, Evan E. | Burger, Joachim | Slatkin, Montgomery | Pääbo, Svante | Kelso, Janet | Reich, David | Krause, Johannes
Nature  2014;513(7518):409-413.
We sequenced the genomes of a ~7,000 year old farmer from Germany and eight ~8,000 year old hunter-gatherers from Luxembourg and Sweden. We analyzed these and other ancient genomes1–4 with 2,345 contemporary humans to show that most present Europeans derive from at least three highly differentiated populations: West European Hunter-Gatherers (WHG), who contributed ancestry to all Europeans but not to Near Easterners; Ancient North Eurasians (ANE) related to Upper Paleolithic Siberians3, who contributed to both Europeans and Near Easterners; and Early European Farmers (EEF), who were mainly of Near Eastern origin but also harbored WHG-related ancestry. We model these populations’ deep relationships and show that EEF had ~44% ancestry from a “Basal Eurasian” population that split prior to the diversification of other non-African lineages.
PMCID: PMC4170574  PMID: 25230663
24.  Gibbon genome and the fast karyotype evolution of small apes 
Carbone, Lucia | Harris, R. Alan | Gnerre, Sante | Veeramah, Krishna R. | Lorente-Galdos, Belen | Huddleston, John | Meyer, Thomas J. | Herrero, Javier | Roos, Christian | Aken, Bronwen | Anaclerio, Fabio | Archidiacono, Nicoletta | Baker, Carl | Barrell, Daniel | Batzer, Mark A. | Beal, Kathryn | Blancher, Antoine | Bohrson, Craig L. | Brameier, Markus | Campbell, Michael S. | Capozzi, Oronzo | Casola, Claudio | Chiatante, Giorgia | Cree, Andrew | Damert, Annette | de Jong, Pieter J. | Dumas, Laura | Fernandez-Callejo, Marcos | Flicek, Paul | Fuchs, Nina V. | Gut, Marta | Gut, Ivo | Hahn, Matthew W. | Hernandez-Rodriguez, Jessica | Hillier, LaDeana W. | Hubley, Robert | Ianc, Bianca | Izsvák, Zsuzsanna | Jablonski, Nina G. | Johnstone, Laurel M. | Karimpour-Fard, Anis | Konkel, Miriam K. | Kostka, Dennis | Lazar, Nathan H. | Lee, Sandra L. | Lewis, Lora R. | Liu, Yue | Locke, Devin P. | Mallick, Swapan | Mendez, Fernando L. | Muffato, Matthieu | Nazareth, Lynne V. | Nevonen, Kimberly A. | O,Bleness, Majesta | Ochis, Cornelia | Odom, Duncan T. | Pollard, Katherine S. | Quilez, Javier | Reich, David | Rocchi, Mariano | Schumann, Gerald G. | Searle, Stephen | Sikela, James M. | Skollar, Gabriella | Smit, Arian | Sonmez, Kemal | Hallers, Boudewijn ten | Terhune, Elizabeth | Thomas, Gregg W.C. | Ullmer, Brygg | Ventura, Mario | Walker, Jerilyn A. | Wall, Jeffrey D. | Walter, Lutz | Ward, Michelle C. | Wheelan, Sarah J. | Whelan, Christopher W. | White, Simon | Wilhelm, Larry J. | Woerner, August E. | Yandell, Mark | Zhu, Baoli | Hammer, Michael F. | Marques-Bonet, Tomas | Eichler, Evan E. | Fulton, Lucinda | Fronick, Catrina | Muzny, Donna M. | Warren, Wesley C. | Worley, Kim C. | Rogers, Jeffrey | Wilson, Richard K. | Gibbs, Richard A.
Nature  2014;513(7517):195-201.
Gibbons are small arboreal apes that display an accelerated rate of evolutionary chromosomal rearrangement and occupy a key node in the primate phylogeny between Old World monkeys and great apes. Here we present the assembly and analysis of a northern white-cheeked gibbon (Nomascus leucogenys) genome. We describe the propensity for a gibbon-specific retrotransposon (LAVA) to insert into chromosome segregation genes and alter transcription by providing a premature termination site, suggesting a possible molecular mechanism for the genome plasticity of the gibbon lineage. We further show that the gibbon genera (Nomascus, Hylobates, Hoolock and Symphalangus) experienced a near-instantaneous radiation ~5 million years ago, coincident with major geographical changes in Southeast Asia that caused cycles of habitat compression and expansion. Finally, we identify signatures of positive selection in genes important for forelimb development (TBX5) and connective tissues (COL1A1) that may have been involved in the adaptation of gibbons to their arboreal habitat.
PMCID: PMC4249732  PMID: 25209798
25.  Modification of Multiple Sclerosis Phenotypes by African Ancestry at HLA 
Archives of neurology  2009;66(2):226-233.
In those with multiple sclerosis (MS), African American individuals have a more severe disease course, an older age at onset, and more often have clinical manifestations restricted to the optic nerves and spinal cord (opticospinal MS) than white persons.
To determine whether genetic variation influences clinical MS patterns.
Retrospective multicenter cohort study.
Six hundred seventy-three African American and 717 white patients with MS.
Main Outcome Measures
Patients with MS were geno-typed for HLA-DRB1 and HLA-DQB1 alleles. The proportion of European ancestry at HLA was estimated by genotyping single-nucleotide polymorphisms with known significant frequency differences in West African and European populations. These genotypes were correlated with the opticospinal disease phenotype, disability measures, and age at onset.
Subjects with DRB1*15 alleles were twice as likely to have typical MS rather than opticospinal MS (P = .001). Of the subjects with opticospinal MS or a history of recurrent transverse myelitis who were seropositive for anti–aquaporin 4 antibodies (approximately 5%), none carried DRB1*15 alleles (P = .008). Independently of DRB1* 15, African ancestry at HLA correlated with disability as measured by the Multiple Sclerosis Severity Score (P < .001) andriskof cane dependency (hazard ratio, 1.36; P < .001); DRB1*15 alleles were associated with a 2.1-year earlier age at onset (P < .001).
These data indicate that the role of HLA in MS is not limited to disease susceptibility but that genes embedded in this locus also influence clinical outcomes.
PMCID: PMC4334456  PMID: 19204159

Results 1-25 (98)