Eun-Seok Cho

Whole-genome resequencing analyses of five pig breeds, including Korean wild and native, and three European origin breeds

Pigs have been one of the most important sources of meat for humans, and their productivity has been substantially improved by recent strong selection. Here, we present whole-genome resequencing analyses of 55 pigs of five breeds representing Korean native pigs, wild boar and three European origin breeds. 1,673.1 Gb of sequence reads were mapped to the Swine reference assembly, covering ∼99.2% of the reference genome, at an average of ∼11.7-fold coverage. We detected 20,123,573 single-nucleotide polymorphisms (SNPs), of which 25.5% were novel. We extracted 35,458 of non-synonymous SNPs in 9,904 genes, which may contribute to traits of interest. The whole SNP sets were further used to access the population structures of the breeds, using multiple methodologies, including phylogenetic, similarity matrix, and population structure analysis. They showed clear population clusters with respect to each breed. Furthermore, we scanned the whole genomes to identify signatures of selection throughout the genome. The result revealed several promising loci that might underlie economically important traits in pigs, such as the CLDN1 and TWIST1 genes. These discoveries provide useful genomic information for further study of the discrete genetic mechanisms associated with economically important traits in pigs.

Copy number variations in Hanwoo and Yanbian cattle genomes using the massively parallel sequencing data.

Hanwoo is an indigenous Korean beef cattle breed, and it shared an ancestor with Yanbian cattle that are found in the Northeast provinces in China until the last century. During recent decades, those cattle breeds experienced different selection pressures. Here, we present genome-wide copy number variations (CNVs) by comparing Hanwoo and Yanbian cattle sequencing data. We used ~3.12 and ~3.07 billion sequence reads from Hanwoo and Yanbian cattle, respectively. A total of 901 putative CNV regions (CNVRs) were identified throughout the genome, representing 5,513,340bp. This is a smaller number than has been reported in previous studies, indicating that Hanwoo are genetically close to Yanbian cattle. Of the CNVRs, 53.2% and 46.8% were found to be gains and losses in Hanwoo. Potential functional roles of each CNVR were assessed by annotating all CNVRs and gene ontology (GO) enrichment analysis. We found that 278 CNVRs overlapped with cattle gene-sets (genic-CNVRs) that could be promising candidates to account for economically important traits in cattle. The enrichment analysis indicated that genes were significantly over-represented in GO terms, including developmental process, multicellular organismal process, reproduction, and response to stimulus. These results provide a valuable genomic resource for determining how CNVs are associated with cattle traits.

Genome-wide Copy Number Variation in a Korean Native Chicken Breed

College of Pharmacy, Dankook University, Cheonan 330-714, KoreaABSTRACT Copy number variation (CNV) is a form of structural variation that shows various numbers of copies in segments of the DNA. It has been shown to account for phenotypic variations in human diseases and agricultural production traits. Currently, most of chicken breeds in the poultry industry are based on European-origin breeds that have been mostly provided from several international breeding companies. Therefore, National Institute of Animal Science, RDA has been trying to restore and improve Korean native chicken breeds (12 lines of 5 breeds) for about 20 years. Thanks to the recent advance of sequencing technologies, genome-wide CNV can be accessed in the higher resolution throughout the genome of species of interest. However, there is no systematic study available to dissect the CNV in the native chicken breed in Korea. Here, we report genome-wide copy number variations identified from a genome of Korean native chicken (Line L) by comparing between the chicken reference sequence assembly (Gallus gallus) and a de novo sequencing assembly of the Korean native chicken (Line L). Throughout all twenty eight chicken autosomes, we identified a total of 501 CNVs; defined as gain and loss of duplication and deletion respectively. Furthermore, we performed gene ontology (GO) analysis for the putative CNVs using DAVID, leading to 68 GO terms clustered independently. Of the clustered GO terms, genes related to transcription and gene regulation were mainly detected. This study provides useful genomic resource to investigate potential biological impli- cations of CNVs with traits of interest in the Korean native chicken.(Key words : copy number variation, Korean native chicken, de novo sequencing)

Integrated transcriptomes throughout swine oestrous cycle reveal dynamic changes in reproductive tissues interacting networks

Female fertility is a highly regulated process involving the synchronized activities of multiple tissues. The underlying genomic regulation of the tissue synchronization is poorly understood. To understand this better we investigated the transcriptomes of the porcine ovary, endometrium, and oviduct at days 0, 3, 6, 9, 12, 15, or 18 of the oestrous cycle. We analysed the transcriptome profiles of the individual tissues and focus on the bridging genes shared by two or more tissues. The three tissue-networks were connected forming a triangular shape. We identified 65 bridging genes with a high level of connectivity to all other genes in the network. The expression levels showed negative correlations between the ovary and the other two tissues, and low correlations between endometrium and oviduct. The main functional annotations involved biosynthesis of steroid hormones, cell-to-cell adhesion, and cell apoptosis, suggesting that regulation of steroid hormone synthesis and tissue viability are major regulatory mechanisms.

Whole-genome association and genome partitioning revealed variants and explained heritability for total number of teats in a Yorkshire pig population

Objective The study was designed to perform a genome-wide association (GWA) and partitioning of genome using Illumina’s PorcineSNP60 Beadchip in order to identify variants and determine the explained heritability for the total number of teats in Yorkshire pig. Methods After screening with the following criteria: minor allele frequency, MAF≤0.01; Hardy-Weinberg equilibrium, HWE≤0.000001, a pair-wise genomic relationship matrix was produced using 42,953 single nucleotide polymorphisms (SNPs). A genome-wide mixed linear model-based association analysis (MLMA) was conducted. And for estimating the explained heritability with genome- or chromosome-wide SNPs the genetic relatedness estimation through maximum likelihood approach was used in our study. Results The MLMA analysis and false discovery rate p-values identified three significant SNPs on two different chromosomes (rs81476910 and rs81405825 on SSC8; rs81332615 on SSC13) for total number of teats. Besides, we estimated that 30% of variance could be explained by all of the common SNPs on the autosomal chromosomes for the trait. The maximum amount of heritability obtained by partitioning the genome were 0.22±0.05, 0.16±0.05, 0.10±0.03 and 0.08±0.03 on SSC7, SSC13, SSC1, and SSC8, respectively. Of them, SSC7 explained the amount of estimated heritability along with a SNP (rs80805264) identified by genome-wide association studies at the empirical p value significance level of 2.35E-05 in our study. Interestingly, rs80805264 was found in a nearby quantitative trait loci (QTL) on SSC7 for the teat number trait as identified in a recent study. Moreover, all other significant SNPs were found within and/or close to some QTLs related to ovary weight, total number of born alive and age at puberty in pigs. Conclusion The SNPs we identified unquestionably represent some of the important QTL regions as well as genes of interest in the genome for various physiological functions responsible for reproduction in pigs.

Association study analysis of phospholipase C zeta gene polymorphism forsperm motility and kinematic characteristics in liquid semen of Boar

For evaluating the boar semen quality, sperm motility (MOT) is an important parameter because the movement of spermatozoa indicates active metabolism, membrane integrity and fertilizing capacity. Phospholipase C zeta (PLCz) is important enzyme in spermatogenesis, but their effect has not been confirmed in pigs yet. Therefore, this study was aimed to analyze their association with sperm motility and kinematic characteristics. DNA samples from 124 Duroc pigs with records of sperm motility and kinematic characteristics [Total motile spermatozoa (MOT), Curvilinear velocity (VCL), Straight-line velocity (VSL), the ratio between VSL and VCL (LIN), Amplitude of Lateral Head displacement (ALH)] were subjected. A SNP in non-coding region of PLCz g.158 A > C was associated with MOT (p < 0.05), VCL (p < 0.01), LIN (p < 0.01) and ALH (p < 0.05) in Duroc population. Therefore, we suggest that the intron region of the porcine PLCz gene may be used as a molecular marker for Duroc boar semen quality, although its functional effect was not defined yet. Whether the association is due to the candidate gene or not require further verification. Thus, it will be of interest to continue association studies in the regions surrounding those genes.

Gene Expression Profiling by RNA Sequencing in Mature/Immature Oocytes of Chicken

Korean Bioinformation Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806, KoreaABSTRACT Chicken eggs undergo various physiological changes during egg maturation. To study genes associated with the egg maturation in pre-ovulation (immature) and post-ovulation (mature), we compared gene expression patterns between in the immature egg and mature egg using RNA sequencing data. Mature and immature eggs were obtained from a Heuksaek Jaerae-jong of Korean native chicken. Total RNAs obtained from the eggs were sequenced by Illumina HiSeq 2000 platform, and the generated sequence reads were mapped to Galgal4 reference sequence assembly using Tuxedo Protocol. From the comparison of the RNA sequencing data, 315 genes were differentially expressed between mature and immature eggs, and 46 genes were only detected in immature egg. Further gene ontology (GO) analysis was performed for the differentially expressed genes using DAVID, showing that 29 and 28 GO terms were independently clustered from mature and immature, respectively. From those clustered GO terms, genes related to germ cell development, sex differentiation and defense response to bacterium were mainly expressed in the immature egg, while genes related to regulation of apoptosis, steroid metabolic process and lipid homeostasis were mainly detected in the mature egg. Our results could contribute to understand egg maturation before and after ovulation, and develop genetic markers for improving egg quality and productivity.(Key words : egg maturation, RNA sequencing, gene ontology, differential gene expression)

Association of Three Polymorphisms in Porcine Ribosomal protein L27a (RPL27A) Gene with Meat-quality Traits

We identified molecular markers associated with meat-quality traits in the porcine RPL27A (ribosomal protein L27a) gene. Three single nucleotide polymorphisms (SNPs) were discovered in the porcine RPL27A gene: g.920T>C, g.1013T>C, and g.1046T>C. The g.920 T>C SNP was significantly associated with pH24 (P C and g.1046T>C SNPs were significantly associated with moisture (P < 0.05). Either the TTT or CCC haplotype was significantly associated with moisture, pH24 and collagen (P < 0.05, respectively). The genotypes of RPL27A associated with meat-quality traits were all located in intron 2. The three SNPs of the RPL27A found in this study will provide useful information for genetic characterization or association studies of meat-quality traits in other populations. Additionally, these markers could potentially be applied in pig breeding programs to improve meat-quality traits after validation in other populations.