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Fulltext A genomic exploration of the early evolution of extant cats and their sabre-toothed relatives [version 2; peer review: 2 approved]

Westbury MV, Barnett R, Sandoval-Velasco M, Gower G, Vieira FG, de Manuel M, et al.

Open Res Eur, 2021 Jun 21;1:25.
PMID: 35098251 DOI: 10.12688/openreseurope.13104.2

Background: The evolutionary relationships of Felidae during their Early-Middle Miocene radiation is contentious. Although the early common ancestors have been subsumed under the grade-group Pseudaelurus, this group is thought to be paraphyletic, including the early ancestors of both modern cats and extinct sabretooths.
Methods: Here, we sequenced a draft nuclear genome of Smilodon populator, dated to 13,182 ± 90 cal BP, making this the oldest palaeogenome from South America to date, a region known to be problematic for ancient DNA preservation. We analysed this genome, together with genomes from other extinct and extant cats to investigate their phylogenetic relationships.
Results: We confirm a deep divergence (~20.65 Ma) within sabretoothed cats. Through the analysis of both simulated and empirical data, we show a lack of gene flow between Smilodon and contemporary Felidae.
Conclusions: Given that some species traditionally assigned to Pseudaelurus originated in the Early Miocene ~20 Ma, this indicates that some species of Pseudaelurus may be younger than the lineages they purportedly gave rise to, further supporting the hypothesis that Pseudaelurus was paraphyletic.
MobiSeq: De novo SNP discovery in model and non-model species through sequencing the flanking region of transposable elements

Rey-Iglesia A, Gopalakrishan S, Carøe C, Alquezar-Planas DE, Ahlmann Nielsen A, Röder T, et al.

Mol Ecol Resour, 2019 Mar;19(2):512-525.
PMID: 30575257 DOI: 10.1111/1755-0998.12984

In recent years, the availability of reduced representation library (RRL) methods has catalysed an expansion of genome-scale studies to characterize both model and non-model organisms. Most of these methods rely on the use of restriction enzymes to obtain DNA sequences at a genome-wide level. These approaches have been widely used to sequence thousands of markers across individuals for many organisms at a reasonable cost, revolutionizing the field of population genomics. However, there are still some limitations associated with these methods, in particular the high molecular weight DNA required as starting material, the reduced number of common loci among investigated samples, and the short length of the sequenced site-associated DNA. Here, we present MobiSeq, a RRL protocol exploiting simple laboratory techniques, that generates genomic data based on PCR targeted enrichment of transposable elements and the sequencing of the associated flanking region. We validate its performance across 103 DNA extracts derived from three mammalian species: grey wolf (Canis lupus), red deer complex (Cervus sp.) and brown rat (Rattus norvegicus). MobiSeq enables the sequencing of hundreds of thousands loci across the genome and performs SNP discovery with relatively low rates of clonality. Given the ease and flexibility of MobiSeq protocol, the method has the potential to be implemented for marker discovery and population genomics across a wide range of organisms-enabling the exploration of diverse evolutionary and conservation questions.
Fulltext High diversity of picornaviruses in rats from different continents revealed by deep sequencing

Hansen TA, Mollerup S, Nguyen NP, White NE, Coghlan M, Alquezar-Planas DE, et al.

Emerg Microbes Infect, 2016 Aug 17;5(8):e90.
PMID: 27530749 DOI: 10.1038/emi.2016.90

Outbreaks of zoonotic diseases in humans and livestock are not uncommon, and an important component in containment of such emerging viral diseases is rapid and reliable diagnostics. Such methods are often PCR-based and hence require the availability of sequence data from the pathogen. Rattus norvegicus (R. norvegicus) is a known reservoir for important zoonotic pathogens. Transmission may be direct via contact with the animal, for example, through exposure to its faecal matter, or indirectly mediated by arthropod vectors. Here we investigated the viral content in rat faecal matter (n=29) collected from two continents by analyzing 2.2 billion next-generation sequencing reads derived from both DNA and RNA. Among other virus families, we found sequences from members of the Picornaviridae to be abundant in the microbiome of all the samples. Here we describe the diversity of the picornavirus-like contigs including near-full-length genomes closely related to the Boone cardiovirus and Theiler's encephalomyelitis virus. From this study, we conclude that picornaviruses within R. norvegicus are more diverse than previously recognized. The virome of R. norvegicus should be investigated further to assess the full potential for zoonotic virus transmission.
Fulltext Population genomics of grey wolves and wolf-like canids in North America

Sinding MS, Gopalakrishan S, Vieira FG, Samaniego Castruita JA, Raundrup K, Heide Jørgensen MP, et al.

PLoS Genet, 2018 11;14(11):e1007745.
PMID: 30419012 DOI: 10.1371/journal.pgen.1007745

North America is currently home to a number of grey wolf (Canis lupus) and wolf-like canid populations, including the coyote (Canis latrans) and the taxonomically controversial red, Eastern timber and Great Lakes wolves. We explored their population structure and regional gene flow using a dataset of 40 full genome sequences that represent the extant diversity of North American wolves and wolf-like canid populations. This included 15 new genomes (13 North American grey wolves, 1 red wolf and 1 Eastern timber/Great Lakes wolf), ranging from 0.4 to 15x coverage. In addition to providing full genome support for the previously proposed coyote-wolf admixture origin for the taxonomically controversial red, Eastern timber and Great Lakes wolves, the discriminatory power offered by our dataset suggests all North American grey wolves, including the Mexican form, are monophyletic, and thus share a common ancestor to the exclusion of all other wolves. Furthermore, we identify three distinct populations in the high arctic, one being a previously unidentified "Polar wolf" population endemic to Ellesmere Island and Greenland. Genetic diversity analyses reveal particularly high inbreeding and low heterozygosity in these Polar wolves, consistent with long-term isolation from the other North American wolves.
Fulltext Contaminating viral sequences in high-throughput sequencing viromics: a linkage study of 700 sequencing libraries

Asplund M, Kjartansdóttir KR, Mollerup S, Vinner L, Fridholm H, Herrera JAR, et al.

Clin Microbiol Infect, 2019 Oct;25(10):1277-1285.
PMID: 31059795 DOI: 10.1016/j.cmi.2019.04.028

OBJECTIVES: Sample preparation for high-throughput sequencing (HTS) includes treatment with various laboratory components, potentially carrying viral nucleic acids, the extent of which has not been thoroughly investigated. Our aim was to systematically examine a diverse repertoire of laboratory components used to prepare samples for HTS in order to identify contaminating viral sequences.
METHODS: A total of 322 samples of mainly human origin were analysed using eight protocols, applying a wide variety of laboratory components. Several samples (60% of human specimens) were processed using different protocols. In total, 712 sequencing libraries were investigated for viral sequence contamination.
RESULTS: Among sequences showing similarity to viruses, 493 were significantly associated with the use of laboratory components. Each of these viral sequences had sporadic appearance, only being identified in a subset of the samples treated with the linked laboratory component, and some were not identified in the non-template control samples. Remarkably, more than 65% of all viral sequences identified were within viral clusters linked to the use of laboratory components.
CONCLUSIONS: We show that high prevalence of contaminating viral sequences can be expected in HTS-based virome data and provide an extensive list of novel contaminating viral sequences that can be used for evaluation of viral findings in future virome and metagenome studies. Moreover, we show that detection can be problematic due to stochastic appearance and limited non-template controls. Although the exact origin of these viral sequences requires further research, our results support laboratory-component-linked viral sequence contamination of both biological and synthetic origin.
Fulltext Genomes of Pleistocene Siberian Wolves Uncover Multiple Extinct Wolf Lineages

Ramos-Madrigal J, Sinding MS, Carøe C, Mak SST, Niemann J, Samaniego Castruita JA, et al.

Curr Biol, 2021 01 11;31(1):198-206.e8.
PMID: 33125870 DOI: 10.1016/j.cub.2020.10.002

Extant Canis lupus genetic diversity can be grouped into three phylogenetically distinct clades: Eurasian and American wolves and domestic dogs.1 Genetic studies have suggested these groups trace their origins to a wolf population that expanded during the last glacial maximum (LGM)1-3 and replaced local wolf populations.4 Moreover, ancient genomes from the Yana basin and the Taimyr peninsula provided evidence of at least one extinct wolf lineage that dwelled in Siberia during the Pleistocene.35 Previous studies have suggested that Pleistocene Siberian canids can be classified into two groups based on cranial morphology. Wolves in the first group are most similar to present-day populations, although those in the second group possess intermediate features between dogs and wolves.67 However, whether this morphological classification represents distinct genetic groups remains unknown. To investigate this question and the relationships between Pleistocene canids, present-day wolves, and dogs, we resequenced the genomes of four Pleistocene canids from Northeast Siberia dated between >50 and 14 ka old, including samples from the two morphological categories. We found these specimens cluster with the two previously sequenced Pleistocene wolves, which are genetically more similar to Eurasian wolves. Our results show that, though the four specimens represent extinct wolf lineages, they do not form a monophyletic group. Instead, each Pleistocene Siberian canid branched off the lineage that gave rise to present-day wolves and dogs. Finally, our results suggest the two previously described morphological groups could represent independent lineages similarly related to present-day wolves and dogs.
Fulltext Interspecific Gene Flow Shaped the Evolution of the Genus Canis

Gopalakrishnan S, Sinding MS, Ramos-Madrigal J, Niemann J, Samaniego Castruita JA, Vieira FG, et al.

Curr Biol, 2018 11 05;28(21):3441-3449.e5.
PMID: 30344120 DOI: 10.1016/j.cub.2018.08.041

The evolutionary history of the wolf-like canids of the genus Canis has been heavily debated, especially regarding the number of distinct species and their relationships at the population and species level [1-6]. We assembled a dataset of 48 resequenced genomes spanning all members of the genus Canis except the black-backed and side-striped jackals, encompassing the global diversity of seven extant canid lineages. This includes eight new genomes, including the first resequenced Ethiopian wolf (Canis simensis), one dhole (Cuon alpinus), two East African hunting dogs (Lycaon pictus), two Eurasian golden jackals (Canis aureus), and two Middle Eastern gray wolves (Canis lupus). The relationships between the Ethiopian wolf, African golden wolf, and golden jackal were resolved. We highlight the role of interspecific hybridization in the evolution of this charismatic group. Specifically, we find gene flow between the ancestors of the dhole and African hunting dog and admixture between the gray wolf, coyote (Canis latrans), golden jackal, and African golden wolf. Additionally, we report gene flow from gray and Ethiopian wolves to the African golden wolf, suggesting that the African golden wolf originated through hybridization between these species. Finally, we hypothesize that coyotes and gray wolves carry genetic material derived from a "ghost" basal canid lineage.
Fulltext Genomic Adaptations and Evolutionary History of the Extinct Scimitar-Toothed Cat, Homotherium latidens

Barnett R, Westbury MV, Sandoval-Velasco M, Vieira FG, Jeon S, Zazula G, et al.

Curr Biol, 2020 Dec 21;30(24):5018-5025.e5.
PMID: 33065008 DOI: 10.1016/j.cub.2020.09.051

Homotherium was a genus of large-bodied scimitar-toothed cats, morphologically distinct from any extant felid species, that went extinct at the end of the Pleistocene [1-4]. They possessed large, saber-form serrated canine teeth, powerful forelimbs, a sloping back, and an enlarged optic bulb, all of which were key characteristics for predation on Pleistocene megafauna [5]. Previous mitochondrial DNA phylogenies suggested that it was a highly divergent sister lineage to all extant cat species [6-8]. However, mitochondrial phylogenies can be misled by hybridization [9], incomplete lineage sorting (ILS), or sex-biased dispersal patterns [10], which might be especially relevant for Homotherium since widespread mito-nuclear discrepancies have been uncovered in modern cats [10]. To examine the evolutionary history of Homotherium, we generated a ∼7x nuclear genome and a ∼38x exome from H. latidens using shotgun and target-capture sequencing approaches. Phylogenetic analyses reveal Homotherium as highly divergent (∼22.5 Ma) from living cat species, with no detectable signs of gene flow. Comparative genomic analyses found signatures of positive selection in several genes, including those involved in vision, cognitive function, and energy consumption, putatively consistent with diurnal activity, well-developed social behavior, and cursorial hunting [5]. Finally, we uncover relatively high levels of genetic diversity, suggesting that Homotherium may have been more abundant than the limited fossil record suggests [3, 4, 11-14]. Our findings complement and extend previous inferences from both the fossil record and initial molecular studies, enhancing our understanding of the evolution and ecology of this remarkable lineage.
Fulltext The evolutionary history of extinct and living lions

de Manuel M, Barnett R, Sandoval-Velasco M, Yamaguchi N, Garrett Vieira F, Zepeda Mendoza ML, et al.

Proc Natl Acad Sci U S A, 2020 May 19;117(20):10927-10934.
PMID: 32366643 DOI: 10.1073/pnas.1919423117

Lions are one of the world's most iconic megafauna, yet little is known about their temporal and spatial demographic history and population differentiation. We analyzed a genomic dataset of 20 specimens: two ca. 30,000-y-old cave lions (Panthera leo spelaea), 12 historic lions (Panthera leo leo/Panthera leo melanochaita) that lived between the 15th and 20th centuries outside the current geographic distribution of lions, and 6 present-day lions from Africa and India. We found that cave and modern lions shared an ancestor ca. 500,000 y ago and that the 2 lineages likely did not hybridize following their divergence. Within modern lions, we found 2 main lineages that diverged ca. 70,000 y ago, with clear evidence of subsequent gene flow. Our data also reveal a nearly complete absence of genetic diversity within Indian lions, probably due to well-documented extremely low effective population sizes in the recent past. Our results contribute toward the understanding of the evolutionary history of lions and complement conservation efforts to protect the diversity of this vulnerable species.
Fulltext Arctic-adapted dogs emerged at the Pleistocene-Holocene transition

Sinding MS, Gopalakrishnan S, Ramos-Madrigal J, de Manuel M, Pitulko VV, Kuderna L, et al.

Science, 2020 06 26;368(6498):1495-1499.
PMID: 32587022 DOI: 10.1126/science.aaz8599

Although sled dogs are one of the most specialized groups of dogs, their origin and evolution has received much less attention than many other dog groups. We applied a genomic approach to investigate their spatiotemporal emergence by sequencing the genomes of 10 modern Greenland sled dogs, an ~9500-year-old Siberian dog associated with archaeological evidence for sled technology, and an ~33,000-year-old Siberian wolf. We found noteworthy genetic similarity between the ancient dog and modern sled dogs. We detected gene flow from Pleistocene Siberian wolves, but not modern American wolves, to present-day sled dogs. The results indicate that the major ancestry of modern sled dogs traces back to Siberia, where sled dog-specific haplotypes of genes that potentially relate to Arctic adaptation were established by 9500 years ago.
Fulltext High-Throughput Sequencing-Based Investigation of Viruses in Human Cancers by Multienrichment Approach

Mollerup S, Asplund M, Friis-Nielsen J, Kjartansdóttir KR, Fridholm H, Hansen TA, et al.

J Infect Dis, 2019 09 13;220(8):1312-1324.
PMID: 31253993 DOI: 10.1093/infdis/jiz318

BACKGROUND: Viruses and other infectious agents cause more than 15% of human cancer cases. High-throughput sequencing-based studies of virus-cancer associations have mainly focused on cancer transcriptome data.
METHODS: In this study, we applied a diverse selection of presequencing enrichment methods targeting all major viral groups, to characterize the viruses present in 197 samples from 18 sample types of cancerous origin. Using high-throughput sequencing, we generated 710 datasets constituting 57 billion sequencing reads.
RESULTS: Detailed in silico investigation of the viral content, including exclusion of viral artefacts, from de novo assembled contigs and individual sequencing reads yielded a map of the viruses detected. Our data reveal a virome dominated by papillomaviruses, anelloviruses, herpesviruses, and parvoviruses. More than half of the included samples contained 1 or more viruses; however, no link between specific viruses and cancer types were found.
CONCLUSIONS: Our study sheds light on viral presence in cancers and provides highly relevant virome data for future reference.

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