Abstract

A main goal of cattle genomics is to identify DNA differences that account for variations in economically important traits. In this study, we performed whole-genome analyses of three important cattle breeds in Korea—Hanwoo, Jeju Heugu, and Korean Holstein—using the Illumina HiSeq 2000 sequencing platform. We achieved 25.5-, 29.6-, and 29.5-fold coverage of the Hanwoo, Jeju Heugu, and Korean Holstein genomes, respectively, and identified a total of 10.4 million single nucleotide polymorphisms (SNPs), of which 54.12% were found to be novel. We also detected 1,063,267 insertions–deletions (InDels) across the genomes (78.92% novel). Annotations of the datasets identified a total of 31,503 nonsynonymous SNPs and 859 frameshift InDels that could affect phenotypic variations in traits of interest. Furthermore, genome-wide copy number variation regions (CNVRs) were detected by comparing the Hanwoo, Jeju Heugu, and previously published Chikso genomes against that of Korean Holstein. A total of 992, 284, and 1881 CNVRs, respectively, were detected throughout the genome. Moreover, 53, 65, 45, and 82 putative regions of homozygosity (ROH) were identified in Hanwoo, Jeju Heugu, Chikso, and Korean Holstein respectively. The results of this study provide a valuable foundation for further investigations to dissect the molecular mechanisms underlying variation in economically important traits in cattle and to develop genetic markers for use in cattle breeding.

Highlights

  • Native cattle have been raised across the Korea peninsula since 2000 B.C [1]

  • Gene Ontology analysis of nonsynonymous single nucleotide polymorphisms (SNPs) and genic copy number variation (CNV) We identified numerous nonsynonymous SNPs, some of which may account for genetic variation in economically important traits in cattle

  • Including SNPs from Chikso, we extracted breed-specific nonsynonymous SNPs (nsSNPs) sets that did not overlap among breeds; we found 3,264, 3,563, 3,459, and 3,573 nsSNPs among 2,080, 2,209, 2,191, and 2,327 genes in Hanwoo, Jeju Heugu, Chikso, and Korean Holstein, respectively

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Summary

Introduction

Native cattle have been raised across the Korea peninsula since 2000 B.C [1]. There are currently four Korean native cattle breeds registered with the Food and Agricultural Organization: Hanwoo (Korean brown cattle), Jeju Heugu (Jeju black cattle), Chikso (Korean brindle cattle), and Heugu (Korean black cattle) [2]. A selective breeding program for Hanwoo was initiated in 1979, and it has contributed to significant increases in economically important traits, such as carcass yield and marbling scores [1,5]. Unlike Hanwoo, the other three native cattle breeds are threatened with extinction because of policies to unify cattle coat colors at the beginning of the 20th century. Those cattle breeds are currently being revaluated to conserve local genetic resources and to pioneer new niche markets to meet demands for safe meats from Korean native breeds in Korea. Since the initiation of the official dairy herd improvement program in 1979, Holsteins have been intensively selected for Korean environments. Milk traits have dramatically improved in the past 30 years; for example, yields of 4,681 kg of milk per cow per lactation can be achieved [6]

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