Project description:Porcine 60K BeadChip genotyping arrays (Illumina) are increasingly being applied in pig genomics to validate SNPs identified by re-sequencing or assembly-versus-assembly method. Here we report that more than 98% SNPs identified from the porcine 60K BeadChip genotyping array (Illumina) were consistent with the SNPs identified from the assembly-based method. This result demonstrates that whole-genome de novo assembly is a reliable approach to deriving accurate maps of SNPs.
Project description:Pestiviruses are highly variable RNA viruses. A growing number of novel pestiviruses has been discovered in domestic and wild species in the last two decades. Recently, a novel atypical porcine pestivirus (APPV) linked with the development of congenital tremor (CT) in neonatal pigs was described in Europe and the Americas. Here, the first Asian APPV complete polyprotein coding sequence was assembled from serum samples from newborn piglets affected with CT in Southern China, and termed APPV_GD. 14 organ samples from affected piglets were analyzed by quantitative RT-PCR (qRT-PCR) to investigate the tissue tropism of APPV, and 135 serum samples from pigs from 10 farms were used for identifying APPV in adult pigs. The highest genome loads were found in submaxillary lymph nodes, and PCR-based detection showed that APPV genomes were present in seven samples from five farms. A phylogenetic tree was constructed based on the full-length genomes of the pestiviruses, and APPV_GD appeared on a new branch with another newly discovered APPV. Nucleotide identity analysis demonstrated that APPV_GD shared the highest nucleotide sequence identity with a German APPV. Bayesian inference was performed using 25 partial sequences of the APPV NS5B gene (528 bp) isolated from four countries in recent years. According to this analysis, the most recent common ancestor (tMRCA) of the current APPV strains might have emerged in Germany and then diversified and spread to Asia, the Americas, and other countries in Europe. However, the result of bayesian inference could change when more APPV strains are isolated in the future. The present study is the first to report APPV in China and infers the origin and dissemination of the current strains of the virus.
Project description:The genus Pestivirus, which belongs to the family Flaviviridae, includes ssRNA+ viruses responsible for infectious diseases in swine, cattle, sheep, goats, and other domestic and wild animals. Recently, several putative pestiviruses species have been discovered and characterized in mammalian species (giraffe pestivirus, antelope pestivirus, HoBi virus, Bungowannah virus, and Linda virus); one of these is a genetically distinct pestivirus, named atypical porcine pestivirus (APPV), discovered using the next-generation sequencing technology. APPV has been detected in piglets with congenital tremor (CT) from four different continents, including North America, South America, Europe, and Asia. There is strong evidence that experimental inoculation and in field outbreaks involving APPV induce CT in piglets. Additionally, splay leg (SL) syndrome has been observed concurrently with CT, and it was induced by APPV in experimental studies and some field cases. Animals with a persistent and/or chronic infection condition can shed the virus over time. Viral-RNA is frequently detected in different tissues from CT-piglets; however, high loads of APPV are detected most consistently in central nervous tissue. Moreover, the APPV genome has been recently detected in semen and preputial swabs from boar studs, as well as in serum and tissue samples from wild boars and domestic adult pigs, all known to be clinically healthy. Phylogenetic analysis revealed that the APPV sequence (complete or partial polyprotein) exhibits high genetic diversity between viral strains detected in different countries and formed independent clusters according to geographic location. Additional studies are needed to evaluate the molecular detection and sero-prevalence of APPV around the world. Lastly, more research is needed to understand clinical presentations associated with APPV infection, as well as the economic losses related to the virus in pig production worldwide.
Project description:Atypical porcine pestivirus (APPV) has been identified as the main causative agent for congenital tremor (CT) type A-II in piglets, which is threatening the health of the global swine herd. However, the evolution of APPV remains largely unknown. In this study, phylogenetic analysis showed that APPV could be divided into three phylogroups (I, II, and III). Phylogroups I and II included viral strains from China, while phylogroup III contained strains from Europe, North America, and Asia. Phylogroups I and II are tentatively thought to be of Chinese origin. Next, compositional property analysis revealed that a high frequency of nucleotide A and A-end codons was used in the APPV genome. Intriguingly, the analysis of preferred codons revealed that the AGA[Arg] and AGG[Arg] were overrepresented. Dinucleotide CC was found to be overrepresented, and dinucleotide CG was underrepresented. Furthermore, it was found that the weak codon usage bias of APPV was mainly dominated by selection pressures versus mutational forces. The codon adaptation index (CAI), relative codon deoptimization index (RCDI), and similarity index (SiD) analyses showed that the codon usage patterns of phylogroup II and III were more similar to the one of a pig than phylogroup I, suggesting that phylogroup II and III may be more adaptive to pigs. Overall, this study provides insights into APPV evolution through phylogeny and codon usage pattern analysis.
Project description:In 2015, a new pestivirus was described in pig sera in the United States. This new "atypical porcine pestivirus" (APPV) was later associated with congenital tremor (CT) in newborn piglets. The virus appears to be distributed worldwide, but the limited knowledge of virus diversity and the use of various diagnostic tests prevent direct comparisons. Therefore, we developed an APPV-specific real-time RT-PCR assay in the 5'UTR of the viral genome to investigate both retro- and prospectively the strains present in Switzerland and their prevalence in domestic pigs. Overall, 1080 sera obtained between 1986 and 2018 were analyzed, revealing a virus prevalence of approximately 13% in pigs for slaughter, whereas it was less than 1% in breeding pigs. In the prospective study, APPV was also detected in piglets displaying CT. None of the samples could detect the Linda virus, which is another new pestivirus recently reported in Austria. Sequencing and phylogenetic analysis revealed a broad diversity of APP viruses in Switzerland that are considerably distinct from sequences reported from other isolates in Europe and overseas. This study indicates that APPV has already been widely circulating in Switzerland for many years, mainly in young animals, with 1986 being the earliest report of APPV worldwide.
Project description:Copy number variations (CNVs), which represent a significant source of genetic diversity in mammals, are currently being associated with phenotypes of clinical relevance, mostly in humans and mice. Notwithstanding, little is known about the extent of CNV that contributes to genetic variation in farm animals, including pig. This Nimblegen experiment reports a genome-wide high resolution map of copy number variation in the porcine genome. After remapping the initial CNV sequences to the latest genome assembly (Sus scrofa v.9), 84 CNV regions (CNVRs) were identified among the genomes of 21 related porcine samples from Duroc breed. We used a set of NimbleGen CGH arrays that tile across the assayable portion of the pig genome with approximately 2.1 million probes, at a 502 bp average probe spacing (Sus scrofa pre assembly version 6). These CNVRs covered 2 Mb of the genome, and ranged in size from 4 to 352 kb (median size of 12 kb). Together, this analysis provides a useful resource to assist with the assessment of CNVs in the contexts of porcine variation, health and productive efficiency.