Comprehensive variation discovery and recovery of missing sequence in the pig genome using multiple de novo assemblies.

Uncovering genetic variation through resequencing is limited by the fact that only sequences with similarity to the reference genome are examined. Reference genomes are often incomplete and cannot represent the full range of genetic diversity as a result of geographical divergence and independent demographic events. To more comprehensively characterize genetic variation of pigs (Sus scrofa), we generated de novo assemblies of nine geographically and phenotypically representative pigs from Eurasia. By comparing them to the reference pig assembly, we uncovered a substantial number of novel SNPs and structural variants, as well as 137.02-Mb sequences harboring 1737 protein-coding genes that were absent in the reference assembly, revealing variants left by selection. Our results illustrate the power of whole-genome de novo sequencing relative to resequencing and provide valuable genetic resources that enable effective use of pigs in both agricultural production and biomedical research.

Deficient of LRRC8A attenuates hypoxia-induced necrosis in 3T3-L1 cells.

Under acute hypoxia, multiple ion channels on the cell membrane are activated, causing cell swelling and eventually necrosis. LRRC8A is an indispensable protein of the volume-regulated anion channel (VRAC), which participates in swelling and the acceleration of cell necrosis. In this study, we revealed a dynamic change in the expression level of the LRRC8 family during hypoxia in 3T3-L1 cells. The disruption of LRRC8A in 3T3-L1 cells was also associated with a significant anti-necrotic phenotype upon hypoxia accompanied by the reduced expression of necrosis-related genes. In vivo, differential expression of LRRC8 family members was also identified between high-altitude pigs and their low-altitude relatives. Taken these findings together, this study demonstrates the involvement of LRRC8A in hypoxia-induced cell necrosis.

Genetic variation and phylogenetic relationship between three serow species of the genus Capricornis based on the complete mitochondrial DNA control region sequences.

The molecular evidence of phylogenetic status regarding the Formosan serow (Capricornis swinhoei) is not robust and little is known about the genetic diversity of the Sumatran serow (Capricornis sumatraensis), which partly is due to the hardness in sample collection. Here we determined the sequences of the complete mitochondrial DNA control region (1,014 bp) of 19 Sumatran-serow individuals. Nine new haplotypes were defined based on 78 variable sites. Combined analysis with other 32 haplotypes downloaded from the public database, including 1 Sumatran-serow, 11 Formosan-serow and 20 Japanese-serow (Capricornis crispus) haplotypes, a relatively high level of nucleotide diversity was first observed in Sumatran serow (π = 0.0249). By comparative analysis with structural consensus sequences from other mammals, we have identified central, left and right domains and depicted the putative functional structure, including extend termination associated sequences and conserve sequence blocks, in mtDNA control region. The alignment of mtDNA control region revealed that both Sumatran and Japanese serow have two tandem repeats (TRs), but three TRs in Formosan serow. Phylogenetic analyses revealed that the Formosan serow is distinct species with the Japanese serow, but a sister group with the Sumatran serow. The divergence time estimated among three serow species revealed that Pleistocene climate changes and the uplift of Qinghai-Tibetan plateau might play an important role in the genetic differentiation of the serows. These results mainly provide the convinced evidence on the genetic relationship between three serow species.

Gene expression profiling reveals distinct features of various porcine adipose tissues.

BACKGROUND: The excessive accumulation of body fat is a major risk factor to develop a variety of metabolic diseases. To investigate the systematic association between the differences in gene expression profiling and adipose deposition, we used pig as a model, and measured the gene expression profiling of six variant adipose tissues in male and females from three pig breeds which display distinct fat level. RESULTS: We identified various differential expressed genes among breeds, tissues and between sexes, and further used a clustering method to identify sets of functionally co-expression genes linked to different obesity-related phenotypes. Our results reveal that the subcutaneous adipose tissues mainly modulate metabolic indicators, nonetheless, the visceral adipose tissues as well as the intermuscular adipose tissue were mainly associated with the impaired inflammatory and immune response. CONCLUSIONS: The present study provided the evidence of gene expression profiling that the subcutaneous adipose tissues are mainly affected the metabolism process, whereas the visceral and intermuscular adipose tissues should been term as the metabolic risk factors of obesity.

Small non-coding RNA transcriptome of four high-altitude vertebrates and their low-altitude relatives.

Animals that lived at high altitudes have evolved distinctive physiological traits that allow them to tolerate extreme high-altitude environment, including higher hemoglobin concentration, increased oxygen saturation of blood and a high energy metabolism. Although previous investigations performed plenty of comparison between high- and low-altitude mammals at the level of morphology, physiology and genomics, mechanism underlying high-altitude adaptation remains largely unknown. Few studies provided comparative analyses in high-altitude adaptation, such as parallel analysis in multiple species. In this study, we generated high-quality small RNA sequencing data for six tissues (heart, liver, spleen, lung, kidney and muscle) from low- and high-altitude populations of four typical livestock animals, and identified comparable numbers of miRNAs in each species. This dataset will provide valuable information for understanding the molecular mechanism of high-altitude adaptation in vertebrates.

Comparative transcriptomics of 5 high-altitude vertebrates and their low-altitude relatives.

Background: Species living at high altitude are subject to strong selective pressures due to inhospitable environments (e.g., hypoxia, low temperature, high solar radiation, and lack of biological production), making these species valuable models for comparative analyses of local adaptation. Studies that have examined high-altitude adaptation have identified a vast array of rapidly evolving genes that characterize the dramatic phenotypic changes in high-altitude animals. However, how high-altitude environment shapes gene expression programs remains largely unknown. Findings: We generated a total of 910 Gb of high-quality RNA-seq data for 180 samples derived from 6 tissues of 5 agriculturally important high-altitude vertebrates (Tibetan chicken, Tibetan pig, Tibetan sheep, Tibetan goat, and yak) and their cross-fertile relatives living in geographically neighboring low-altitude regions. Of these, ∼75% reads could be aligned to their respective reference genomes, and on average ∼60% of annotated protein coding genes in each organism showed FPKM expression values greater than 0.5. We observed a general concordance in topological relationships between the nucleotide alignments and gene expression-based trees. Tissue and species accounted for markedly more variance than altitude based on either the expression or the alternative splicing patterns. Cross-species clustering analyses showed a tissue-dominated pattern of gene expression and a species-dominated pattern for alternative splicing. We also identified numerous differentially expressed genes that could potentially be involved in phenotypic divergence shaped by high-altitude adaptation. Conclusions: These data serve as a valuable resource for examining the convergence and divergence of gene expression changes between species as they adapt or acclimatize to high-altitude environments.

Deciphering the microRNA transcriptome of skeletal muscle during porcine development.

MicroRNAs (miRNAs) play critical roles in many important biological processes, such as growth and development in mammals. Various studies of porcine muscle development have mainly focused on identifying miRNAs that are important for fetal and adult muscle development; however, little is known about the role of miRNAs in middle-aged muscle development. Here, we present a comprehensive investigation of miRNA transcriptomes across five porcine muscle development stages, including one prenatal and four postnatal stages. We identified 404 known porcine miRNAs, 118 novel miRNAs, and 101 miRNAs that are conserved in other mammals. A set of universally abundant miRNAs was found across the distinct muscle development stages. This set of miRNAs may play important housekeeping roles that are involved in myogenesis. A short time-series expression miner analysis indicated significant variations in miRNA expression across distinct muscle development stages. We also found enhanced differentiation- and morphogenesis-related miRNA levels in the embryonic stage; conversely, apoptosis-related miRNA levels increased relatively later in muscle development. These results provide integral insight into miRNA function throughout pig muscle development stages. Our findings will promote further development of the pig as a model organism for human age-related muscle disease research.

Deep sequencing of the transcriptome reveals inflammatory features of porcine visceral adipose tissue.

Functional differences in the different types of adipose tissue and the impact of their dysfunction on metabolism are associated with the regional distribution of adipose depots. Here we show a genome-wide comparison between the transcriptomes of one source of subcutaneous and two sources of visceral adipose tissue in the pig using an RNA-seq approach. We obtained ~32.3 million unique mapped reads which covered ~80.2% of the current annotated transcripts across these three sources of adipose tissue. We identified various genes differentially expressed between subcutaneous and visceral adipose tissue, which are potentially associated with the inflammatory features of visceral adipose tissue. These results are of benefit for understanding the phenotypic, metabolic and functional differences between different types of adipose tissue that are deposited in different body sites.

Genomic analyses identify distinct patterns of selection in domesticated pigs and Tibetan wild boars.

We report the sequencing at 131× coverage, de novo assembly and analyses of the genome of a female Tibetan wild boar. We also resequenced the whole genomes of 30 Tibetan wild boars from six major distributed locations and 18 geographically related pigs in China. We characterized genetic diversity, population structure and patterns of evolution. We searched for genomic regions under selection, which includes genes that are involved in hypoxia, olfaction, energy metabolism and drug response. Comparing the genome of Tibetan wild boar with those of neighboring Chinese domestic pigs further showed the impact of thousands of years of artificial selection and different signatures of selection in wild boar and domestic pig. We also report genetic adaptations in Tibetan wild boar that are associated with high altitudes and characterize the genetic basis of increased salivation in domestic pig.

An atlas of DNA methylomes in porcine adipose and muscle tissues.

It is evident that epigenetic factors, especially DNA methylation, have essential roles in obesity development. Here, using pig as a model, we investigate the systematic association between DNA methylation and obesity. We sample eight variant adipose and two distinct skeletal muscle tissues from three pig breeds living within comparable environments but displaying distinct fat level. We generate 1,381 Gb of sequence data from 180 methylated DNA immunoprecipitation libraries, and provide a genome-wide DNA methylation map as well as a gene expression map for adipose and muscle studies. The analysis shows global similarity and difference among breeds, sexes and anatomic locations, and identifies the differentially methylated regions. The differentially methylated regions in promoters are highly associated with obesity development via expression repression of both known obesity-related genes and novel genes. This comprehensive map provides a solid basis for exploring epigenetic mechanisms of adipose deposition and muscle growth.