Whole-Genome Sequencing Reveals Lactase Persistence Adaptation in European Dogs.

Coexistence and cooperation between dogs and humans over thousands of years have supported convergent evolutionary processes in the two species. Previous studies found that Eurasian dogs evolved into a distinct geographic cluster. In this study, we used the genomes of 242 European dogs, 38 Southeast Asian indigenous (SEAI) dogs, and 41 gray wolves to identify adaptation of European dogs . We report 86 unique positively selected genes in European dogs, among which is LCT (lactase). LCT encodes lactase, which is fundamental for the digestion of lactose. We found that an A-to-G mutation (chr19:38,609,592) is almost fixed in Middle Eastern and European dogs. The results of two-dimensional site frequency spectrum (2D SFS) support that the mutation is under soft sweep . We inferred that the onset of positive selection of the mutation is shorter than 6,535 years and behind the well-developed dairy economy in central Europe. It increases the expression of LCT by reducing its binding with ZEB1, which would enhance dog's ability to digest milk-based diets. Our study uncovers the genetic basis of convergent evolution between humans and dogs with respect to diet, emphasizing the import of the dog as a biomedical model for studying mechanisms of the digestive system.

Ancient Hybridization with an Unknown Population Facilitated High-Altitude Adaptation of Canids.

Genetic introgression not only provides material for adaptive evolution but also confounds our understanding of evolutionary history. This is particularly true for canids, a species complex in which genome sequencing and analysis has revealed a complex history of admixture and introgression. Here, we sequence 19 new whole genomes from high-altitude Tibetan and Himalayan wolves and dogs and combine these into a larger data set of 166 whole canid genomes. Using these data, we explore the evolutionary history and adaptation of these and other canid lineages. We find that Tibetan and Himalayan wolves are closely related to each other, and that ∼39% of their nuclear genome is derived from an as-yet-unrecognized wolf-like lineage that is deeply diverged from living Holarctic wolves and dogs. The EPAS1 haplotype, which is present at high frequencies in Tibetan dog breeds and wolves and confers an adaptive advantage to animals living at high altitudes, was probably derived from this ancient lineage. Our study underscores the complexity of canid evolution and demonstrates how admixture and introgression can shape the evolutionary trajectories of species.

Genome-wide genetic structure and selection signatures for color in 10 traditional Chinese yellow-feathered chicken breeds.

BACKGROUND: Yellow-feathered chickens (YFCs) have a long history in China. They are well-known for the nutritional and commercial importance attributable to their yellow color phenotype. Currently, there is a huge paucity in knowledge of the genetic determinants responsible for phenotypic and biochemical properties of these iconic chickens. This study aimed to uncover the genetic structure and the molecular underpinnings of the YFCs trademark coloration. RESULTS: The whole-genomes of 100 YFCs from 10 major traditional breeds and 10 Huaibei partridge chickens from China were re-sequenced. Comparative population genomics based on autosomal single nucleotide polymorphisms (SNPs) revealed three geographically based clusters among the YFCs. Compared to other Chinese indigenous chicken genomes incorporated from previous studies, a closer genetic proximity within YFC breeds than between YFC breeds and other chicken populations is evident. Through genome-wide scans for selective sweeps, we identified RALY heterogeneous nuclear ribonucleoprotein (RALY), leucine rich repeat containing G protein-coupled receptor 4 (LGR4), solute carrier family 23 member 2 (SLC23A2), and solute carrier family 2 member 14 (SLC2A14), besides the classical beta-carotene dioxygenase 2 (BCDO2), as major candidates pigment determining genes in the YFCs. CONCLUSION: We provide the first comprehensive genomic data of the YFCs. Our analyses show phylogeographical patterns among the YFCs and potential candidate genes giving rise to the yellow color trait of the YFCs. This study lays the foundation for further research on the genome-phenotype cross-talks that define important poultry traits and for formulating genetic breeding and conservation strategies for the YFCs.

Genome wide analyses uncover allele-specific RNA editing in human and mouse.

RNA editing is one of the most common RNA level modifications that potentially generate amino acid changes similar to those resulting from genomic nonsynonymous mutations. However, unlike DNA level allele-specific modifications such as DNA methylation, it is currently unknown whether RNA editing displays allele-specificity across tissues and species. Here, we analyzed allele-specific RNA editing in human tissues and from brain tissues of heterozygous mice generated by crosses between divergent mouse strains and found a high proportion of overlap of allele-specific RNA editing sites between different samples. We identified three allele-specific RNA editing sites cause amino acid changes in coding regions of human and mouse genes, whereas their associated SNPs yielded synonymous differences. In vitro cellular experiments confirmed that sequences differing at a synonymous SNP can have differences in a linked allele-specific RNA editing site with nonsynonymous implications. Further, we demonstrate that allele-specific RNA editing is influenced by differences in local RNA secondary structure generated by SNPs. Our study provides new insights towards a better comprehension of the molecular mechanism that link SNPs with human diseases and traits.

Whole-Genome Sequencing of African Dogs Provides Insights into Adaptations against Tropical Parasites.

Natural selection in domestic dogs is of great interest in evolutionary biology since dogs have migrated to every inhabited continent of the world alongside humans, and adapted to diverse environments. Here, we explored their demographic history and genetic basis of adaptation to the tropical African environment using whole genome analyses of 19 African indigenous dogs from Nigeria. Demographic analysis suggests that the ancestors of these dogs migrated into Africa from Eurasia 14,000 years ago and underwent a severe founder effect before population expansion. Admixture analysis further reveals that African dog genomes contain about 1.88-3.50% introgression from African golden wolves (Canis anthus). Population genetic analysis identifies 50 positively selected genes linked with immunity, angiogenesis, ultraviolet protection, as well as insulin secretion and sensitivity that may contribute to adaptation to tropical conditions. One of the positively selected genes, adhesion G protein-coupled receptor E1 (ADGRE1), has also been found to be association with severe malaria resistance in African human populations. Functional assessments showed that ADGRE1 provides protective host defense against Plasmodium infections. This result, together with the fact that the inflammatory response to canine babesiosis is similar to complicated falciparum malaria in humans, support the dogs as a model for the study of malaria control and treatment.

Out of Southern East Asia of the Brown Rat Revealed by Large-Scale Genome Sequencing.

The geographic origin and migration of the brown rat (Rattus norvegicus) remain subjects of considerable debate. In this study, we sequenced whole genomes of 110 wild brown rats with a diverse world-wide representation. We reveal that brown rats migrated out of southern East Asia, rather than northern Asia as formerly suggested, into the Middle East and then to Europe and Africa, thousands of years ago. Comparison of genomes from different geographical populations reveals that many genes involved in the immune system experienced positive selection in the wild brown rat.

An Evolutionary Genomic Perspective on the Breeding of Dwarf Chickens.

The evolutionary history for dwarfism in chickens remains an enigma. Herein, we explore the evolution of the Serama, the smallest breed of chicken. Leveraging comparative population genomics, analyses identify several genes that are potentially associated with the growth and development of bones and muscles. These genes, and in particular both POU1F1 and IGF1, are under strong positive selection. Three allopatric dwarf bantams (Serama, Yuanbao, and Daweishan) with different breeding-histories, form distinct clusters and exhibit unique population structures. Parallel genetic mechanisms underlay their variation in body size. These findings provide insights into the multiple and complex pathways, depending on genomic variation, that chicken can take in response to aviculture selection for dwarfism.

Rapid Evolution of Genes Involved in Learning and Energy Metabolism for Domestication of the Laboratory Rat.

The laboratory rat, widely used in biomedical research, is domesticated from wild brown rat. The origin and genetic mechanism underlying domestication of the laboratory rat remain largely elusive. In the present study, large scale genomes supported a single origin for the laboratory rat, possibly from a sister group to wild rats from Europe/Africa/Middle East. Genomic and transcriptomic analyses uncovered many artificially selected genes (e.g., FOXP2, B3GAT1, and CLOCK) involved in the nervous system. These genes associate with learning ability and regulation of circadian rhythm, which likely enabled the successful domestication of the laboratory rat. Particularly, many genes, including mitochondrial genes responsible for energy metabolism, displayed a substantially increased expression in the brain of laboratory rats compared with wild rats. Our findings demystify the origin and evolution of this model animal, and provide insight into the process of its domestication.

A human-specific insertion promotes cell proliferation and migration by enhancing TBC1D8B expression.

Human-specific insertions play important roles in human phenotypes and diseases. Here we reported a 446-bp insertion (Insert-446) in intron 11 of the TBC1D8B gene, located on chromosome X, and traced its origin to a portion of intron 6 of the EBF1 gene on chromosome 5. Interestingly, Insert-446 was present in the human Neanderthal and Denisovans genomes, and was fixed in humans after human-chimpanzee divergence. We have demonstrated that Insert-446 acts as an enhancer through binding transcript factors that promotes a higher expression of human TBC1D8B gene as compared with orthologs in macaques. In addition, over-expression TBC1D8B promoted cell proliferation and migration through "a dual finger" catalytic mechanism (Arg538 and Gln573) in the TBC domain in vitro and knockdown of TBC1D8B attenuated tumorigenesis in vivo. Knockout of Insert-446 prevented cell proliferation and migration in cancer and normal cells. Our results reveal that the human-specific Insert-446 promotes cell proliferation and migration by upregulating the expression of TBC1D8B gene. These findings provide a significant insight into the effects of human-specific insertions on evolution.

Demographic history and genetic diversity of wild African harlequin quail (Coturnix delegorguei delegorguei) populations of Kenya.

Hunting wild African harlequin quails (Coturnix delegorguei delegorguei) using traditional methods in Western Kenya has been ongoing for generations, yet their genetic diversity and evolutionary history are largely unknown. In this study, the genetic variation and demographic history of wild African harlequin quails were assessed using a 347bp mitochondrial DNA (mtDNA) control region fragment and 119,339 single nucleotide polymorphisms (SNPs) from genotyping-by-sequencing (GBS) data. Genetic diversity analyses revealed that the genetic variation in wild African harlequin quails was predominantly among individuals than populations. Demographic analyses indicated a signal of rapid demographic expansion, and the estimated time since population expansion was found to be 150,000-350,000 years ago, corresponding to around the Pliocene-Pleistocene boundary. A gradual decline in their effective population size was also observed, which raised concerns about their conservation status. These results provide the first account of the genetic diversity of wild African harlequin quails of Siaya, thereby creating a helpful foundation in their biodiversity conservation.

Genomic Analyses of Unveil Helmeted Guinea Fowl (Numida meleagris) Domestication in West Africa.

Domestication of the helmeted guinea fowl (HGF; Numida meleagris) in Africa remains elusive. Here we report a high-quality de novo genome assembly for domestic HGF generated by long- and short-reads sequencing together with optical and chromatin interaction mapping. Using this assembly as the reference, we performed population genomic analyses for newly sequenced whole-genomes for 129 birds from Africa, Asia, and Europe, including domestic animals (n = 89), wild progenitors (n = 34), and their closely related wild species (n = 6). Our results reveal domestication of HGF in West Africa around 1,300-5,500 years ago. Scanning for selective signals characterized the functional genes in behavior and locomotion changes involved in domestication of HGF. The pleiotropy and linkage in genes affecting plumage color and fertility were revealed in the recent breeding of Italian domestic HGF. In addition to presenting a missing piece to the jigsaw puzzle of domestication in poultry, our study provides valuable genetic resources for researchers and breeders to improve production in this species.

Genomic regions under selection in the feralization of the dingoes.

Dingoes are wild canids living in Australia, originating from domestic dogs. They have lived isolated from both the wild and the domestic ancestor, making them a unique model for studying feralization. Here, we sequence the genomes of 10 dingoes and 2 New Guinea Singing Dogs. Phylogenetic and demographic analyses show that dingoes originate from dogs in southern East Asia, which migrated via Island Southeast Asia to reach Australia around 8300 years ago, and subsequently diverged into a genetically distinct population. Selection analysis identifies 50 positively selected genes enriched in digestion and metabolism, indicating a diet change during feralization of dingoes. Thirteen of these genes have shifted allele frequencies compared to dogs but not compared to wolves. Functional assays show that an A-to-G mutation in ARHGEF7 decreases the endogenous expression, suggesting behavioral adaptations related to the transitions in environment. Our results indicate that the feralization of the dingo induced positive selection on genomic regions correlated to neurodevelopment, metabolism and reproduction, in adaptation to a wild environment.

Phenotypic and morphometric differentiation of indigenous chickens from Kenya and other tropical countries augments perspectives for genetic resource improvement and conservation.

Indigenous chickens at the Swahili coast and other traditional migratory corridors in Kenya represent important populations that are inconclusively characterized. Using a comprehensive dataset of Kenyan indigenous chickens and additional mined data of chickens from 8 African and 5 Asian countries, we performed univariate and multivariate assessments to uncover the underlying phenotypic and morphometric variability. Kenyan indigenous chickens expressed differentiation of several qualitative and quantitative traits, both among different counties in the Swahili coast, and among coastal, western, and northern migratory corridors. There was a substantial population stratification of these chickens, particularly distinctive clustering of chickens from Marsabit, Lamu, and Kilifi counties. The pooled dataset further clarified a closer phenotypic and morphometric proximity of chickens within different geographical regions. We additionally revealed a preponderance of bantam and rumpless traits to hot and humid locales, and feathered shanks to cooler regions. Currently, most chicken breeding programs in developing countries rely on phenotypic and morphometric properties. Hence, the high chicken diversity and population stratification observed in our study, possibly shaped by natural and artificial selective pressures, reveal opportunities for complementary phenotypic and genotypic assessments to identify resources for effective breed improvement and conservation strategies of indigenous chickens in the tropics.

Origin of new genes after zygotic genome activation in vertebrate.

New genes are drivers of evolutionary innovation and phenotypic evolution. Expression of new genes in early development raises the possibility that new genes could originate and be recruited for functions in embryonic development, but this remains undocumented. Here, based on temporal gene expression at different developmental stages in Xenopus tropicalis, we found that young protein-coding genes were significantly enriched for expression in developmental stages occurring after the midblastula transition (MBT), and displayed a decreasing trend in abundance in the subsequent stages after MBT. To complement the finding, we demonstrate essential functional attributes of a young orphan gene, named as Fog2, in morphological development. Our data indicate that new genes could originate after MBT and be recruited for functions in embryonic development, and thus provide insights for better understanding of the origin, evolution, and function of new genes.

Identification of valid reference genes for mRNA and microRNA normalisation in prostate cancer cell lines.

RT-qPCR offers high sensitivity, for accurate interpretations of qPCR results however, normalisation using suitable reference genes is fundamental. Androgens can regulate transcriptional expression including reference gene expression in prostate cancer. In this study, we evaluated ten mRNA and six non-protein coding RNA reference genes in five prostate cell lines under varied dihydrotestosterone (DHT) treatments. We validated the effects of DHT-treatments using media containing charcoal-stripped serum prior to DHT stimulation on the test samples by Western blot experiments. Reference gene expression stability was analysed using three programs (geNorm, NormFinder and BestKeeper), and the recommended comprehensive ranking is provided. Our results reveal that ACTB and GAPDH, and miR-16 and miR-1228-3p are the most suitable mRNA and miRNA reference genes across all cell lines, respectively. Considering prostate cancer cell types, ACTB/GAPDH and ACTB/HPRT1 are the most suitable reference gene combinations for mRNA analysis, and miR-16/miR-1228-3p and RNU6-2/RNU43 for miRNA analysis in AR+, and AR- and normal cell lines, respectively. Comparison of relative target gene (PCA3 and miR-141) expression reveals different patterns depending on reference genes used for normalisation. To our knowledge, this is the first report on validation of reference genes under different DHT treatments in prostate cancer cells. This study provides insights for discovery of reliable DHT-regulated genes in prostate cells.

Correlations between mitochondrial DNA haplogroup D5 and chronic hepatitis B virus infection in Yunnan, China.

Mitochondrial abnormality is frequently reported in individuals with hepatitis B virus (HBV) infection, but the associated hosts' mitochondrial genetic factors remain obscure. We hypothesized that mitochondria may affect host susceptibility to HBV infection. In this study, we aimed to detect the association between chronic HBV infection and mitochondrial DNA in Chinese from Yunnan, Southwest China. A total of 272 individuals with chronic HBV infection (CHB), 310 who had never been infected by HBV (healthy controls, HC) and 278 with a trace of HBV infection (spontaneously recovered, SR) were analysed for mtDNA sequence variations and classified into respective haplogroups. Haplogroup frequencies were compared between HBV infected patients, HCs and SRs. Haplogroup D5 presented a higher frequency in CHBs than in HCs (P = 0.017, OR = 2.87, 95% confidence interval [CI] = (1.21-6.81)) and SRs (P = 0.049, OR = 2.90, 95% CI = 1.01-8.35). The network of haplogroup D5 revealed a distinct distribution pattern between CHBs and non-CHBs. A trend of higher viral load among CHBs with haplogroup D5 was observed. Our results indicate the risk potential of mtDNA haplogroup D5 in chronic HBV infection in Yunnan, China.

Fixed differences in the 3'UTR of buffalo PRNP gene provide binding sites for miRNAs post-transcriptional regulation.

Bovine spongiform encephalopathy, a member of transmissible spongiform encephalopathies, has not been reported in buffaloes, Bubalus bubalis. Prion protein (PrP), encoded by the prion protein gene (PRNP), is fundamental in the pathogenesis of transmissible spongiform encephalopathies. We previously showed that buffaloes express more PrP proteins but lower PRNP mRNA than cattle in several pivotal tissues like the obex. Therefore, we sought to establish whether genetic variability in PRNP 3'UTR, mediated by miRNA down-regulation, causes PrP expression differences between cattle and buffaloes. We annotated the 3'UTR of buffalo PRNP gene by 3'RACE experiment. A total of 92 fixed differences in the complete 3'UTR (~ 3 kb) were identified between 13 cattle and 13 buffaloes. Resequencing of UTR-C (g.786-1436) and UTR-B (g.778-1456) fragments confirmed that all mutations except g.1022T in cattle are fixed differences between 147 cattle and 146 buffaloes. In addition, analysis of the variation of ΔG between cattle and buffalo sequences reveals four remarkable differences. Two buffalo-specific insertion sites (a 28-bp insertion and an AG insertion in buffalo 3'UTR of PRNP g.970-997 and g. 1088-1089, respectively) and two mutants (g. 1007-1008 TG→CC) create compatible binding sites for miRNAs in buffalo 3'UTR. This was validated through luciferase reporter assays which demonstrated that miR-125b-5p, miR-132-3p, miR-145-5p, miR-331-3p, and miR-338-3p directly act on the fixed difference sites in buffalo 3'UTR. Additional expressional analyses show that these five miRNAs are coexpressed with PRNP in bovine obex tissues. Our study reveals a miRNAs regulated mechanism explaining the differences in prion expression between cattle and buffalo.

Genome-wide discovery of long intergenic noncoding RNAs and their epigenetic signatures in the rat.

Long intergenic noncoding RNAs (lincRNAs) play a crucial role in many biological processes. The rat is an important model organism in biomedical research. Recent studies have detected rat lincRNA genes from several samples. However, identification of rat lincRNAs using large-scale RNA-seq datasets remains unreported. Herein, using more than 100 billion RNA-seq reads from 59 publications together with RefSeq and UniGene annotated RNAs, we report 39,154 lincRNA transcripts encoded by 19,162 lincRNA genes in the rat. We reveal sequence and expression similarities in lincRNAs of rat, mouse and human. DNA methylation level of lincRNAs is higher than that of protein-coding genes across the transcription start sites (TSSs). And, three lincRNA genes overlap with differential methylation regions (DMRs) which associate with spontaneously hypertensive disease. In addition, there are similar binding trends for three transcription factors (HNF4A, CEBPA and FOXA1) between lincRNA genes and protein-coding genes, indicating that they harbour similar transcription regulatory mechanisms. To date, this is the most comprehensive assessment of lincRNAs in the rat genome. We provide valuable data that will advance lincRNA research using rat as a model.

PigVar: a database of pig variations and positive selection signatures.

Database URL: http://www.ibiomedical.net/pigvar/.

The RNA editome of Macaca mulatta and functional characterization of RNA editing in mitochondria.

RNA editing was first discovered in mitochondrial RNA molecular. However, whether adenosine-to-inosine (A-to-I) RNA editing has functions in nuclear genes involved in mitochondria remains elusive. Here, we retrieved 707,246 A-to-I RNA editing sites in Macaca mulatta leveraging massive transcriptomes of 30 different tissues and genomes of nine tissues, together with the reported data, and found that A-to-I RNA editing occurred frequently in nuclear genes that have functions in mitochondria. The mitochondrial structure, the level of ATP production, and the expression of some key genes involved in mitochondrial function were dysregulated after knocking down the expression of ADAR1 and ADAR2, the key genes encoding the enzyme responsible for RNA editing. When investigating dynamic changes of RNA editing during brain development, an amino-acid-changing RNA editing site (I234/V) in MFN1, a mediator of mitochondrial fusion, was identified to be significantly correlated with age, and could influence the function of MFN1. When studying transcriptomes of brain disorder, we found that dysregulated RNA editing sites in autism were also enriched within genes having mitochondrial functions. These data indicated that RNA editing had a significant function in mitochondria via their influence on nuclear genes.