Dissecting evolution and disease using comparative vertebrate genomics

An endothelial regulatory module links blood pressure regulation with elite athletic performance

The control of transcription is crucial for homeostasis in mammals. A previous selective sweep analysis of horse racing performance revealed a 19.6 kb candidate regulatory region 50 kb downstream of the Endothelin3 (EDN3) gene. Here, the region was narrowed to a 5.5 kb span of 14 SNVs, with elite and sub-elite haplotypes analyzed for association to racing performance, blood pressure and plasma levels of EDN3 in Coldblooded trotters and Standardbreds. Comparative analysis of human HiCap data identified the span as an enhancer cluster active in endothelial cells, interacting with genes relevant to blood pressure regulation. Coldblooded trotters with the sub-elite haplotype had significantly higher blood pressure compared to horses with the elite performing haplotype during exercise. Alleles within the elite haplotype were part of the standing variation in pre-domestication horses, and have risen in frequency during the era of breed development and selection. These results advance our understanding of the molecular genetics of athletic performance and vascular traits in both horses and humans.

Xenopus tropicalis osteoblast-specific open chromatin regions reveal promoters and enhancers involved in human skeletal phenotypes and shed light on early vertebrate evolution

While understanding the genetic underpinnings of osteogenesis has far-reaching implications for skeletal diseases and evolution, a comprehensive characterization of the osteoblastic regulatory landscape in non-mammalian vertebrates is still lacking. Here, we compared the ATAC-Seq profile of Xenopus tropicalis (Xt) osteoblasts to a variety of non mineralizing control tissues, and identified osteoblast-specific nucleosome free regions (NFRs) at 527 promoters and 6747 distal regions. Sequence analyses, Gene Ontology, RNA-Seq and ChIP-Seq against four key histone marks confirmed that the distal regions correspond to bona fide osteogenic transcriptional enhancers exhibiting a shared regulatory logic with mammals. We report 425 regulatory regions conserved with human and globally associated to skeletogenic genes. Of these, 35 regions have been shown to impact human skeletal phenotypes by GWAS, including one trps1 enhancer and the runx2 promoter, two genes which are respectively involved in trichorhinophalangeal syndrome type I and cleidocranial dysplasia. Intriguingly, 60 osteoblastic NFRs also align to the genome of the elephant shark, a species lacking osteoblasts and bone tissue. To tackle this paradox, we chose to focus on dlx5 because its conserved promoter, known to integrate regulatory inputs during mammalian osteogenesis, harbours an osteoblast-specific NFR in both frog and human. Hence, we show that dlx5 is expressed in Xt and elephant shark odontoblasts, supporting a common cellular and genetic origin of bone and dentine. Taken together, our work (i) unravels the Xt osteogenic regulatory landscape, (ii) illustrates how cross-species comparisons harvest data relevant to human biology and (iii) reveals that a set of genes including bnc2, dlx5, ebf3, mir199a, nfia, runx2 and zfhx4 drove the development of a primitive form of mineralized skeletal tissue deep in the vertebrate lineage.

Evolutionary origin of germline pathogenic variants in human DNA mismatch repair genes

BACKGROUND

Mismatch repair (MMR) system is evolutionarily conserved for genome stability maintenance. Germline pathogenic variants (PVs) in MMR genes that lead to MMR functional deficiency are associated with high cancer risk. Knowing the evolutionary origin of germline PVs in human MMR genes will facilitate understanding the biological base of MMR deficiency in cancer. However, systematic knowledge is lacking to address the issue. In this study, we performed a comprehensive analysis to know the evolutionary origin of human MMR PVs.

METHODS

We retrieved MMR gene variants from the ClinVar database. The genomes of 100 vertebrates were collected from the UCSC genome browser and ancient human sequencing data were obtained through comprehensive data mining. Cross-species conservation analysis was performed based on the phylogenetic relationship among 100 vertebrates. Rescaled ancient sequencing data were used to perform variant calling for archeological analysis.

RESULTS

Using the phylogenetic approach, we traced the 3369 MMR PVs identified in modern humans in 99 non-human vertebrate genomes but found no evidence for cross-species conservation as the source for human MMR PVs. Using the archeological approach, we searched the human MMR PVs in over 5000 ancient human genomes dated from 45,045 to 100 years before present and identified a group of MMR PVs shared between modern and ancient humans mostly within 10,000 years with similar quantitative patterns.

CONCLUSION

Our study reveals that MMR PVs in modern humans were arisen within the recent human evolutionary history.

Lymphocyte pathway analysis using naturally lymphocyte-deficient fish

Comparative phylogenetic analyses are of potential value to establish the essential components of genetic networks underlying physiological traits. For species that naturally lack particular lymphocyte lineages, we show here that this strategy readily distinguishes trait-specific actors from pleiotropic components of the genetic network governing lymphocyte differentiation. Previously, three of the four members of the DNA polymerase X family have been implicated in the junctional diversification process during the somatic assembly of antigen receptors. Our phylogenetic analysis indicates that the presence of terminal deoxynucleotidyl transferase is strictly associated with the facility of V(D)J recombination, whereas PolL and PolM genes are retained even in species lacking Rag-mediated somatic diversification of antigen receptor genes.

Evolutionary constraint and innovation across hundreds of placental mammals

Zoonomia is the largest comparative genomics resource for mammals produced to date. By aligning genomes for 240 species, we identify bases that, when mutated, are likely to affect fitness and alter disease risk. At least 332 million bases (~10.7%) in the human genome are unusually conserved across species (evolutionarily constrained) relative to neutrally evolving repeats, and 4552 ultraconserved elements are nearly perfectly conserved. Of 101 million significantly constrained single bases, 80% are outside protein-coding exons and half have no functional annotations in the Encyclopedia of DNA Elements (ENCODE) resource. Changes in genes and regulatory elements are associated with exceptional mammalian traits, such as hibernation, that could inform therapeutic development. Earth's vast and imperiled biodiversity offers distinctive power for identifying genetic variants that affect genome function and organismal phenotypes.

Analysis of the P. lividus sea urchin genome highlights contrasting trends of genomic and regulatory evolution in deuterostomes

Sea urchins are emblematic models in developmental biology and display several characteristics that set them apart from other deuterostomes. To uncover the genomic cues that may underlie these specificities, we generated a chromosome-scale genome assembly for the sea urchin Paracentrotus lividus and an extensive gene expression and epigenetic profiles of its embryonic development. We found that, unlike vertebrates, sea urchins retained ancestral chromosomal linkages but underwent very fast intrachromosomal gene order mixing. We identified a burst of gene duplication in the echinoid lineage and showed that some of these expanded genes have been recruited in novel structures (water vascular system, Aristotle's lantern, and skeletogenic micromere lineage). Finally, we identified gene-regulatory modules conserved between sea urchins and chordates. Our results suggest that gene-regulatory networks controlling development can be conserved despite extensive gene order rearrangement.

Current advances in primate genomics: novel approaches for understanding evolution and disease

Primate genomics holds the key to understanding fundamental aspects of human evolution and disease. However, genetic diversity and functional genomics data sets are currently available for only a few of the more than 500 extant primate species. Concerted efforts are under way to characterize primate genomes, genetic polymorphism and divergence, and functional landscapes across the primate phylogeny. The resulting data sets will enable the connection of genotypes to phenotypes and provide new insight into aspects of the genetics of primate traits, including human diseases. In this Review, we describe the existing genome assemblies as well as genetic variation and functional genomic data sets. We highlight some of the challenges with sample acquisition. Finally, we explore how technological advances in single-cell functional genomics and induced pluripotent stem cell-derived organoids will facilitate our understanding of the molecular foundations of primate biology.

Chromosome-scale genome assembly of the African giant pouched rat (Cricetomys ansorgei) and evolutionary analysis reveals evidence of olfactory specialization

The Southern giant pouched rat, Cricetomys ansorgei, is a large rodent best known for its ability to detect landmines using its impressive sense of smell. Their powerful chemosensory abilities enable subtle discrimination of chemical social signals, and female pouched rats demonstrate a unique reproductive physiology hypothesized to be mediated by pheromonal mechanisms. Thus, C. ansorgei represents a novel mammalian model for chemosensory physiology, social behavior, and pheromonal control of reproductive physiology. We present the first chromosome-scale genomic sequence of the pouched rat encoding 22,671 protein coding genes, including 1571 olfactory receptors, and provide a glance into the evolutionary history of this species. Functional enrichment analysis reveals genetic expansions specific to the pouched rat are enriched for functions related to olfactory specialization. Overall, this assembly is of reference-quality, and will serve as a useful and informative genomic sequence on which we can confidently base future molecular research involving the pouched rat.

Reproducible acquisition, management and meta-analysis of nucleotide sequence (meta)data using q2-fondue

MOTIVATION

The volume of public nucleotide sequence data has blossomed over the past two decades and is ripe for re- and meta-analyses to enable novel discoveries. However, reproducible re-use and management of sequence datasets and associated metadata remain critical challenges. We created the open source Python package q2-fondue to enable user-friendly acquisition, re-use and management of public sequence (meta)data while adhering to open data principles.

RESULTS

q2-fondue allows fully provenance-tracked programmatic access to and management of data from the NCBI Sequence Read Archive (SRA). Unlike other packages allowing download of sequence data from the SRA, q2-fondue enables full data provenance tracking from data download to final visualization, integrates with the QIIME 2 ecosystem, prevents data loss upon space exhaustion and allows download of (meta)data given a publication library. To highlight its manifold capabilities, we present executable demonstrations using publicly available amplicon, whole genome and metagenome datasets.

AVAILABILITY AND IMPLEMENTATION

q2-fondue is available as an open-source BSD-3-licensed Python package at https://github.com/bokulich-lab/q2-fondue. Usage tutorials are available in the same repository. All Jupyter notebooks used in this article are available under https://github.com/bokulich-lab/q2-fondue-examples.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Evolution of γ chain cytokines: mechanisms, methods and applications

The common γ chain family of cytokines and their receptors play fundamental roles in the immune system. Evolutionary studies of γ chain cytokines have elegantly illustrated how the immune system adapts to ever-changing environmental conditions. Indeed, these studies have revealed the uniqueness of cytokine evolution, which exhibits strong positive selection pressure needed to adapt to rapidly evolving threats whilst still conserving their receptor binding capabilities. In this review, we summarise the evolutionary mechanisms that gave rise to the characteristically diverse family of γ chain cytokines. We also speculate on the benefits of studying cytokine evolution, which may provide alternative ways to design novel cytokine therapeutic strategies. Additionally, we discuss current evolutionary models that elucidate the emergence of distinct cytokines (IL-4 and IL-13) and cytokine receptors (IL-2Rα and IL-15Rα). Finally, we address and reflect on the difficulties associated with evolutionary studies of rapidly evolving genes and describe a variety of computational methods that have revealed numerous aspects of cytokine evolution.

Vision-related convergent gene losses reveal SERPINE3's unknown role in the eye

Despite decades of research, knowledge about the genes that are important for development and function of the mammalian eye and are involved in human eye disorders remains incomplete. During mammalian evolution, mammals that naturally exhibit poor vision or regressive eye phenotypes have independently lost many eye-related genes. This provides an opportunity to predict novel eye-related genes based on specific evolutionary gene loss signatures. Building on these observations, we performed a genome-wide screen across 49 mammals for functionally uncharacterized genes that are preferentially lost in species exhibiting lower visual acuity values. The screen uncovered several genes, including SERPINE3, a putative serine proteinase inhibitor. A detailed investigation of 381 additional mammals revealed that SERPINE3 is independently lost in 18 lineages that typically do not primarily rely on vision, predicting a vision-related function for this gene. To test this, we show that SERPINE3 has the highest expression in eyes of zebrafish and mouse. In the zebrafish retina, serpine3 is expressed in Müller glia cells, a cell type essential for survival and maintenance of the retina. A CRISPR-mediated knockout of serpine3 in zebrafish resulted in alterations in eye shape and defects in retinal layering. Furthermore, two human polymorphisms that are in linkage with SERPINE3 are associated with eye-related traits. Together, these results suggest that SERPINE3 has a role in vertebrate eyes. More generally, by integrating comparative genomics with experiments in model organisms, we show that screens for specific phenotype-associated gene signatures can predict functions of uncharacterized genes.

Chick fetal organ spheroids as a model to study development and disease

BACKGROUND

Organ culture models have been used over the past few decades to study development and disease. The in vitro three-dimensional (3D) culture system of organoids is well known, however, these 3D systems are both costly and difficult to culture and maintain. As such, less expensive, faster and less complex methods to maintain 3D cell culture models would complement the use of organoids. Chick embryos have been used as a model to study human biology for centuries, with many fundamental discoveries as a result. These include cell type induction, cell competence, plasticity and contact inhibition, which indicates the relevance of using chick embryos when studying developmental biology and disease mechanisms.

RESULTS

Here, we present an updated protocol that enables time efficient, cost effective and long-term expansion of fetal organ spheroids (FOSs) from chick embryos. Utilizing this protocol, we generated FOSs in an anchorage-independent growth pattern from seven different organs, including brain, lung, heart, liver, stomach, intestine and epidermis. These three-dimensional (3D) structures recapitulate many cellular and structural aspects of their in vivo counterpart organs and serve as a useful developmental model. In addition, we show a functional application of FOSs to analyze cell-cell interaction and cell invasion patterns as observed in cancer.

CONCLUSION

The establishment of a broad ranging and highly effective method to generate FOSs from different organs was successful in terms of the formation of healthy, proliferating 3D organ spheroids that exhibited organ-like characteristics. Potential applications of chick FOSs are their use in studies of cell-to-cell contact, cell fusion and tumor invasion under defined conditions. Future studies will reveal whether chick FOSs also can be applicable in scientific areas such as viral infections, drug screening, cancer diagnostics and/or tissue engineering.

Whole-Genome Sequence Data Suggest Environmental Adaptation of Ethiopian Sheep Populations

Great progress has been made over recent years in the identification of selection signatures in the genomes of livestock species. This work has primarily been carried out in commercial breeds for which the dominant selection pressures are associated with artificial selection. As agriculture and food security are likely to be strongly affected by climate change, a better understanding of environment-imposed selection on agricultural species is warranted. Ethiopia is an ideal setting to investigate environmental adaptation in livestock due to its wide variation in geo-climatic characteristics and the extensive genetic and phenotypic variation of its livestock. Here, we identified over three million single nucleotide variants across 12 Ethiopian sheep populations and applied landscape genomics approaches to investigate the association between these variants and environmental variables. Our results suggest that environmental adaptation for precipitation-related variables is stronger than that related to altitude or temperature, consistent with large-scale meta-analyses of selection pressure across species. The set of genes showing association with environmental variables was enriched for genes highly expressed in human blood and nerve tissues. There was also evidence of enrichment for genes associated with high-altitude adaptation although no strong association was identified with hypoxia-inducible-factor (HIF) genes. One of the strongest altitude-related signals was for a collagen gene, consistent with previous studies of high-altitude adaptation. Several altitude-associated genes also showed evidence of adaptation with temperature, suggesting a relationship between responses to these environmental factors. These results provide a foundation to investigate further the effects of climatic variables on small ruminant populations.

The influence of evolutionary history on human health and disease

Nearly all genetic variants that influence disease risk have human-specific origins; however, the systems they influence have ancient roots that often trace back to evolutionary events long before the origin of humans. Here, we review how advances in our understanding of the genetic architectures of diseases, recent human evolution and deep evolutionary history can help explain how and why humans in modern environments become ill. Human populations exhibit differences in the prevalence of many common and rare genetic diseases. These differences are largely the result of the diverse environmental, cultural, demographic and genetic histories of modern human populations. Synthesizing our growing knowledge of evolutionary history with genetic medicine, while accounting for environmental and social factors, will help to achieve the promise of personalized genomics and realize the potential hidden in an individual's DNA sequence to guide clinical decisions. In short, precision medicine is fundamentally evolutionary medicine, and integration of evolutionary perspectives into the clinic will support the realization of its full potential.

A comparative genomics multitool for scientific discovery and conservation

The Zoonomia Project is investigating the genomics of shared and specialized traits in eutherian mammals. Here we provide genome assemblies for 131 species, of which all but 9 are previously uncharacterized, and describe a whole-genome alignment of 240 species of considerable phylogenetic diversity, comprising representatives from more than 80% of mammalian families. We find that regions of reduced genetic diversity are more abundant in species at a high risk of extinction, discern signals of evolutionary selection at high resolution and provide insights from individual reference genomes. By prioritizing phylogenetic diversity and making data available quickly and without restriction, the Zoonomia Project aims to support biological discovery, medical research and the conservation of biodiversity.

A whole-genome alignment of 240 phylogenetically diverse species of eutherian mammal—including 131 previously uncharacterized species—from the Zoonomia Project provides data that support biological discovery, medical research and conservation.

Building the vertebrate codex using the gene breaking protein trap library

One key bottleneck in understanding the human genome is the relative under-characterization of 90% of protein coding regions. We report a collection of 1200 transgenic zebrafish strains made with the gene-break transposon (GBT) protein trap to simultaneously report and reversibly knockdown the tagged genes. Protein trap-associated mRFP expression shows previously undocumented expression of 35% and 90% of cloned genes at 2 and 4 days post-fertilization, respectively. Further, investigated alleles regularly show 99% gene-specific mRNA knockdown. Homozygous GBT animals in ryr1b, fras1, tnnt2a, edar and hmcn1 phenocopied established mutants. 204 cloned lines trapped diverse proteins, including 64 orthologs of human disease-associated genes with 40 as potential new disease models. Severely reduced skeletal muscle Ca²⁺ transients in GBT ryr1b homozygous animals validated the ability to explore molecular mechanisms of genetic diseases. This GBT system facilitates novel functional genome annotation towards understanding cellular and molecular underpinnings of vertebrate biology and human disease.

Predicting gene regulatory regions with a convolutional neural network for processing double-strand genome sequence information

With advances in sequencing technology, a vast amount of genomic sequence information has become available. However, annotating biological functions particularly of non-protein-coding regions in genome sequences without experiments is still a challenging task. Recently deep learning-based methods were shown to have the ability to predict gene regulatory regions from genome sequences, promising to aid the interpretation of genomic sequence data. Here, we report an improvement of the prediction accuracy for gene regulatory regions by using the design of convolution layers that efficiently process genomic sequence information, and developed a software, DeepGMAP, to train and compare different deep learning-based models (https://github.com/koonimaru/DeepGMAP). First, we demonstrate that our convolution layers, termed forward- and reverse-sequence scan (FRSS) layers, integrate both forward and reverse strand information, and enhance the power to predict gene regulatory regions. Second, we assessed previous studies and identified problems associated with data structures that caused overfitting. Finally, we introduce visualization methods to examine what the program learned. Together, our FRSS layers improve the prediction accuracy for gene regulatory regions.

What animals can teach us about evolution, the human genome, and human disease

During the past 20 years, since I started as a postdoc, the world of genetics and genomics has changed dramatically. My main research goal throughout my career has been to understand human disease genetics, and I have developed comparative genomics and comparative genetics to generate resources and tools for understanding human disease. Through comparative genomics I have worked to sequence enough mammals to understand the functional potential of each base in the human genome as well as chosen vertebrates to study the evolutionary changes that have given many species their key traits. Through comparative genetics, I have developed the dog as a model for human disease, characterising the genome itself and determining a list of germ-line loci and somatic mutations causing complex diseases and cancer in the dog. Pulling all these findings and resources together opens new doors for understanding genome evolution, the genetics of complex traits and cancer in man and his best friend.

The Genome of the Great Gerbil Reveals Species-Specific Duplication of an MHCII Gene

The great gerbil (Rhombomys opimus) is a social rodent living in permanent, complex burrow systems distributed throughout Central Asia, where it serves as the main host of several important vector-borne infectious pathogens including the well-known plague bacterium (Yersinia pestis). Here, we present a continuous annotated genome assembly of the great gerbil, covering over 96% of the estimated 2.47-Gb genome. Taking advantage of the recent genome assemblies of the sand rat (Psammomys obesus) and the Mongolian gerbil (Meriones unguiculatus), comparative immunogenomic analyses reveal shared gene losses within TLR gene families (i.e., TLR8, TLR10, and the entire TLR11-subfamily) for Gerbillinae, accompanied with signs of diversifying selection of TLR7 and TLR9. Most notably, we find a great gerbil-specific duplication of the MHCII DRB locus. In silico analyses suggest that the duplicated gene provides high peptide binding affinity for Yersiniae epitopes as well as Leishmania and Leptospira epitopes, putatively leading to increased capability to withstand infections by these pathogens. Our study demonstrates the power of whole-genome sequencing combined with comparative genomic analyses to gain deeper insight into the immunogenomic landscape of the great gerbil and its close relatives.

Contrasting Patterns of Rapid Molecular Evolution within the p53 Network across Mammal and Sauropsid Lineages

Cancer is a threat to multicellular organisms, yet the molecular evolution of pathways that prevent the accumulation of genetic damage has been largely unexplored. The p53 network regulates how cells respond to DNA-damaging stressors. We know little about p53 network molecular evolution as a whole. In this study, we performed comparative genetic analyses of the p53 network to quantify the number of genes within the network that are rapidly evolving and constrained, and the association between lifespan and the patterns of evolution. Based on our previous published data set, we used genomes and transcriptomes of 34 sauropsids and 32 mammals to analyze the molecular evolution of 45 genes within the p53 network. We found that genes in the network exhibited evidence of positive selection and divergent molecular evolution in mammals and sauropsids. Specifically, we found more evidence of positive selection in sauropsids than mammals, indicating that sauropsids have different targets of selection. In sauropsids, more genes upstream in the network exhibited positive selection, and this observation is driven by positive selection in squamates, which is consistent with previous work showing rapid divergence and adaptation of metabolic and stress pathways in this group. Finally, we identified a negative correlation between maximum lifespan and the number of genes with evidence of divergent molecular evolution, indicating that species with longer lifespans likely experienced less variation in selection across the network. In summary, our study offers evidence that comparative genomic approaches can provide insights into how molecular networks have evolved across diverse species.

Exploring the genetics of trotting racing ability in horses using a unique Nordic horse model

Background

Horses have been strongly selected for speed, strength, and endurance-exercise traits since the onset of domestication. As a result, highly specialized horse breeds have developed with many modern horse breeds often representing closed populations with high phenotypic and genetic uniformity. However, a great deal of variation still exists between breeds, making the horse particularly well suited for genetic studies of athleticism. To identify genomic regions associated with athleticism as it pertains to trotting racing ability in the horse, the current study applies a pooled sequence analysis approach using a unique Nordic horse model.

Results

Pooled sequence data from three Nordic horse populations were used for F_ST analysis. After strict filtering, F_ST analysis yielded 580 differentiated regions for trotting racing ability. Candidate regions on equine chromosomes 7 and 11 contained the largest number of SNPs (n = 214 and 147, respectively). GO analyses identified multiple genes related to intelligence, energy metabolism, and skeletal development as potential candidate genes. However, only one candidate region for trotting racing ability overlapped a known racing ability QTL.

Conclusions

Not unexpected for genomic investigations of complex traits, the current study identified hundreds of candidate regions contributing to trotting racing ability in the horse. Likely resulting from the cumulative effects of many variants across the genome, racing ability continues to demonstrate its polygenic nature with candidate regions implicating genes influencing both musculature and neurological development.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5484-9) contains supplementary material, which is available to authorized users.

Functional Annotation of Animal Genomes (FAANG): Current Achievements and Roadmap

Functional annotation of genomes is a prerequisite for contemporary basic and applied genomic research, yet farmed animal genomics is deficient in such annotation. To address this, the FAANG (Functional Annotation of Animal Genomes) Consortium is producing genome-wide data sets on RNA expression, DNA methylation, and chromatin modification, as well as chromatin accessibility and interactions. In addition to informing our understanding of genome function, including comparative approaches to elucidate constrained sequence or epigenetic elements, these annotation maps will improve the precision and sensitivity of genomic selection for animal improvement. A scientific community-driven effort has already created a coordinated data collection and analysis enterprise crucial for the success of this global effort. Although it is early in this continuing process, functional data have already been produced and application to genetic improvement reported. The functional annotation delivered by the FAANG initiative will add value and utility to the greatly improved genome sequences being established for domesticated animal species.

Evolutionary conservation of Y Chromosome ampliconic gene families despite extensive structural variation

Despite claims that the mammalian Y Chromosome is on a path to extinction, comparative sequence analysis of primate Y Chromosomes has shown the decay of the ancestral single-copy genes has all but ceased in this eutherian lineage. The suite of single-copy Y-linked genes is highly conserved among the majority of eutherian Y Chromosomes due to strong purifying selection to retain dosage-sensitive genes. In contrast, the ampliconic regions of the Y Chromosome, which contain testis-specific genes that encode the majority of the transcripts on eutherian Y Chromosomes, are rapidly evolving and are thought to undergo species-specific turnover. However, ampliconic genes are known from only a handful of species, limiting insights into their long-term evolutionary dynamics. We used a clone-based sequencing approach employing both long- and short-read sequencing technologies to assemble ∼2.4 Mb of representative ampliconic sequence dispersed across the domestic cat Y Chromosome, and identified the major ampliconic gene families and repeat units. We analyzed fluorescence in situ hybridization, qPCR, and whole-genome sequence data from 20 cat species and revealed that ampliconic gene families are conserved across the cat family Felidae but show high transcript diversity, copy number variation, and structural rearrangement. Our analysis of ampliconic gene evolution unveils a complex pattern of long-term gene content stability despite extensive structural variation on a nonrecombining background.

Whole-genome comparison of endogenous retrovirus segregation across wild and domestic host species populations

Although recent advances in sequencing and computational analyses have facilitated use of endogenous retroviruses (ERVs) for deciphering coevolution among retroviruses and their hosts, sampling effects from different host populations present major challenges. Here we utilize available whole-genome data from wild and domesticated European rabbit (Oryctolagus cuniculus sp.) populations, sequenced as DNA pools by paired-end Illumina technology, for identifying segregating reference as well as nonreference ERV loci, to reveal their variation along the host phylogeny and domestication history. To produce new viruses, retroviruses must insert a proviral DNA copy into the host nuclear DNA. Occasional proviral insertions into the host germline have been passed down through generations as inherited ERVs during millions of years. These ERVs represent retroviruses that were active at the time of infection and thus present a remarkable record of historical virus-host associations. To examine segregating ERVs in host populations, we apply a reference library search strategy for anchoring ERV-associated short-sequence read pairs from pooled whole-genome sequences to reference genome assembly positions. We show that most ERVs segregate along host phylogeny but also uncover radiation of some ERVs, identified as segregating loci among wild and domestic rabbits. The study targets pertinent issues regarding genome sampling when examining virus-host evolution from the genomic ERV record and offers improved scope regarding common strategies for single-nucleotide variant analyses in host population comparative genomics.

Population genomics of wild Chinese rhesus macaques reveals a dynamic demographic history and local adaptation, with implications for biomedical research

Background

The rhesus macaque (RM, Macaca mulatta) is the most important nonhuman primate model in biomedical research. We present the first genomic survey of wild RMs, sequencing 81 geo-referenced individuals of five subspecies from 17 locations in China, a large fraction of the species’ natural distribution.

Results

Populations were structured into five genetic lineages on the mainland and Hainan Island, recapitulating current subspecies designations. These subspecies are estimated to have diverged 125.8 to 51.3 thousand years ago, but feature recent gene flow. Consistent with the expectation of a larger body size in colder climates and smaller body size in warmer climates (Bergman's rule), the northernmost RM lineage (M. m. tcheliensis), possessing the largest body size of all Chinese RMs, and the southernmost lineage (M. m. brevicaudus), with the smallest body size of all Chinese RMs, feature positively selected genes responsible for skeletal development. Further, two candidate selected genes (Fbp1, Fbp2) found in M. m. tcheliensis are involved in gluconeogenesis, potentially maintaining stable blood glucose levels during starvation when food resources are scarce in winter. The tropical subspecies M. m. brevicaudus showed positively selected genes related to cardiovascular function and response to temperature stimuli, potentially involved in tropical adaptation. We found 118 single-nucleotide polymorphisms matching human disease-causing variants with 82 being subspecies specific.

Conclusions

These data provide a resource for selection of RMs in biomedical experiments. The demographic history of Chinese RMs and their history of local adaption offer new insights into their evolution and provide valuable baseline information for biomedical investigation.

Adding resolution and dimensionality to comparative genomics: moving from reference genomes to clade genomics

The main goal and promise of comparative genomics has been to create a comprehensive catalog of genomic information and function across the phenomenal diversity of living systems. A recent study has demonstrated the evolutionary insights possible by generating high-quality whole-genome assemblies from multiple species of a clade.

Large-Scale Analysis of Genetic and Clinical Patient Data

Biomedical data science has experienced an explosion of new data over the past decade. Abundant genetic and genomic data are increasingly available in large, diverse data sets due to the maturation of modern molecular technologies. Along with these molecular data, dense, rich phenotypic data are also available on comprehensive clinical data sets from health care provider organizations, clinical trials, population health registries, and epidemiologic studies. The methods and approaches for interrogating these large genetic/genomic and clinical data sets continue to evolve rapidly, as our understanding of the questions and challenges continue to emerge. In this review, the state-of-the-art methodologies for genetic/genomic analysis along with complex phenomics will be discussed. This field is changing and adapting to the novel data types made available, as well as technological advances in computation and machine learning. Thus, I will also discuss the future challenges in this exciting and innovative space. The promises of precision medicine rely heavily on the ability to marry complex genetic/genomic data with clinical phenotypes in meaningful ways.

Diversification of the functions of proglucagon and glucagon receptor genes in fish

The teleost fish-specific genome duplication gave rise to a great number of species inhabiting diverse environments with different access to nutrients and life histories. This event produced duplicated gcg genes, gcga and gcgb, for proglucagon-derived peptides, glucagon and GLP-1 and duplicated gcgr receptor genes, gcgra and gcgrb, which play key roles connecting the consumption of nutrients with glucose metabolism. We conducted a systematic survey of the genomes from 28 species of fish (24 bony (Superclass Osteichthyes), 1 lobe-finned (Class Sarcoperygii), 1 cartilaginous (Superclass Chondrichthyes), and 2 jawless (Superclass Agnatha)) and find that almost all surveyed ray-finned fish contain gcga and gcgb genes with different coding potential and duplicated gcgr genes, gcgra and gcgrb that form two separate clades in the phylogenetic tree consistent with the accepted species phylogeny. All gcgb genes encoded only glucagon and GLP-1 and gcga genes encoded glucagon, GLP-1, and GLP-2, indicating that gcga was subfunctionalized to produce GLP-2. We find a single glp2r, but no glp1r suggesting that duplicated gcgrb was neofunctionalized to bind GLP-1, as demonstrated for the zebrafish gcgrb (Oren et al., 2016). In functional experiments with zebrafish gcgrb and GLP-1 from diverse fish we find that anglerfish GLP-1a, encoded by gcga, is less biologically active than the gcgb anglerfish GLP-1b paralog. But some other fish (zebrafish, salmon, and catfish) gcga GLP-1a display similar biological activities, indicating that the regulation of glucose metabolism by GLP-1 in ray-finned fish is species-specific. Searches of genomes in cartilaginous fish identified a proglucagon gene that encodes a novel GLP-3 peptide in addition to glucagon, GLP-1, and GLP-2, as well as a single gcgr, glp2r, and a new glucagon receptor-like receptor whose identity still needs to be confirmed. The sequence of the shark GLP-1 contained an N-terminal mammalian-like extension that in mammals undergoes a proteolytic cleavage to release biologically active GLP-1. Our results indicate that early in vertebrate evolution diverse regulatory mechanisms emerged for the control of glucose metabolism by proglucagon-derived peptides and their receptors and that in ray-finned fish they included subfunctionalization and neofunctionalization of these genes.

Identifying co-opted transposable elements using comparative epigenomics

The human genome gives rise to different epigenomic landscapes that define each cell type and can be deregulated in disease. Recent efforts by ENCODE, the NIH Roadmap and the International Human Epigenome Consortium (IHEC) have made significant advances towards assembling reference epigenomic maps of various tissues. Notably, these projects have found that approximately 80% of human DNA was biochemically active in at least one epigenomic assay while only approximately 10% of the sequence displayed signs of purifying selection. Given that transposable elements (TEs) make up at least 50% of the human genome and can be actively transcribed or act as regulatory elements either for their own purposes or be co-opted for the benefit of their host; we are interested in exploring their overall contribution to the "functional" genome. Traditional methods used to identify functional DNA have relied on comparative genomics, conservation analysis and low throughput validation assays. To discover co-opted TEs, and distinguish them from noisy genomic elements, we argue that comparative epigenomic methods will also be important.