Dataset Information

Recovery of native genetic background in admixed populations using haplotypes, phenotypes, and pedigree information--using Cika cattle as a case breed.

ABSTRACT: The aim of this study was to obtain unbiased estimates of the diversity parameters, the population history, and the degree of admixture in Cika cattle which represents the local admixed breeds at risk of extinction undergoing challenging conservation programs. Genetic analyses were performed on the genome-wide Single Nucleotide Polymorphism (SNP) Illumina Bovine SNP50 array data of 76 Cika animals and 531 animals from 14 reference populations. To obtain unbiased estimates we used short haplotypes spanning four markers instead of single SNPs to avoid an ascertainment bias of the BovineSNP50 array. Genome-wide haplotypes combined with partial pedigree and type trait classification show the potential to improve identification of purebred animals with a low degree of admixture. Phylogenetic analyses demonstrated unique genetic identity of Cika animals. Genetic distance matrix presented by rooted Neighbour-Net suggested long and broad phylogenetic connection between Cika and Pinzgauer. Unsupervised clustering performed by the admixture analysis and two-dimensional presentation of the genetic distances between individuals also suggest Cika is a distinct breed despite being similar in appearance to Pinzgauer. Animals identified as the most purebred could be used as a nucleus for a recovery of the native genetic background in the current admixed population. The results show that local well-adapted strains, which have never been intensively managed and differentiated into specific breeds, exhibit large haplotype diversity. They suggest a conservation and recovery approach that does not rely exclusively on the search for the original native genetic background but rather on the identification and removal of common introgressed haplotypes would be more powerful. Successful implementation of such an approach should be based on combining phenotype, pedigree, and genome-wide haplotype data of the breed of interest and a spectrum of reference breeds which potentially have had direct or indirect historical contribution to the genetic makeup of the breed of interest.

SUBMITTER: Simcic M

PROVIDER: S-EPMC4414476 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Recovery of native genetic background in admixed populations using haplotypes, phenotypes, and pedigree information--using Cika cattle as a case breed.

Simčič Mojca M Smetko Anamarija A Sölkner Johann J Seichter Doris D Gorjanc Gregor G Kompan Dragomir D Medugorac Ivica I

PloS one 20150429 4

The aim of this study was to obtain unbiased estimates of the diversity parameters, the population history, and the degree of admixture in Cika cattle which represents the local admixed breeds at risk of extinction undergoing challenging conservation programs. Genetic analyses were performed on the genome-wide Single Nucleotide Polymorphism (SNP) Illumina Bovine SNP50 array data of 76 Cika animals and 531 animals from 14 reference populations. To obtain unbiased estimates we used short haplotype ...[more]

PMID: 25923207

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Project description:BACKGROUND: Comparison of recent patterns of recombination derived from linkage maps to historical patterns of recombination from linkage disequilibrium (LD) could help identify genomic regions affected by strong artificial selection, appearing as reduced recent recombination. Norwegian Red cattle (NRF) make an interesting case study for investigating these patterns as it is an admixed breed with an extensively recorded pedigree. NRF have been under strong artificial selection for traits such as milk and meat production, fertility and health. While measures of LD is also crucial for determining the number of markers required for association mapping studies, estimates of recombination rate can be used to assess quality of genomic assemblies. RESULTS: A dataset containing more than 17,000 genome-wide distributed SNPs and 2600 animals was used to assess recombination rates and LD in NRF. Although low LD measured by r2 was observed in NRF relative to some of the breeds from which this breed originates, reports from breeds other than those assessed in this study have described more rapid decline in r2 at short distances than what was found in NRF. Rate of decline in r2 for NRF suggested that to obtain an expected r2 between markers and a causal polymorphism of at least 0.5 for genome-wide association studies, approximately one SNP every 15 kb or a total of 200,000 SNPs would be required. For well known quantitative trait loci (QTLs) for milk production traits on Bos Taurus chromosomes 1, 6 and 20, map length based on historic recombination was greater than map length based on recent recombination in NRF. Further, positions for 130 previously unpositioned contigs from assembly of the bovine genome sequence (Btau_4.0) found using comparative sequence analysis were validated by linkage analysis, and 28% of these positions corresponded to extreme values of population recombination rate. CONCLUSION: While LD is reduced in NRF compared to some of the breeds from which this admixed breed originated, it is elevated over short distances compared to some other cattle breeds. Genomic regions in NRF where map length based on historic recombination was greater than map length based on recent recombination coincided with some well known QTL regions for milk production traits. Linkage analysis in combination with comparative sequence analysis and detection of regions with extreme values of population recombination rate proved to be valuable for detecting problematic regions in the Btau_4.0 genome assembly.

Project description:Domestic animals can serve as model systems of adaptive introgression and their genomic signatures. In part, their usefulness as model systems is due to their well-known histories. Different breeding strategies such as introgression and artificial selection have generated numerous desirable phenotypes and superior performance in domestic animals. The modern Danish Red Dairy Cattle is studied as an example of an introgressed population. It originates from crossing the traditional Danish Red Dairy Cattle with the Holstein and Brown Swiss breeds, both known for high milk production. This crossing happened, among other things due to changes in the production system, to raise milk production and overall performance. The genomes of modern Danish Red Dairy Cattle are heavily influenced by regions introgressed from the Holstein and Brown Swiss breeds and under subsequent selection in the admixed population. The introgressed proportion of the genome was found to be highly variable across the genome. Haplotypes introgressed from Holstein and Brown Swiss contained or overlapped known genes affecting milk production, as well as protein and fat content (CD14, ZNF215, BCL2L12, and THRSP for Holstein origin and ITPR2, BCAT1, LAP3, and MED28 for Brown Swiss origin). Genomic regions with high introgression signals also contained genes and enriched QTL associated with calving traits, body confirmation, feed efficiency, carcass, and fertility traits. These introgressed signals with relative identity-by-descent scores larger than the median showing Holstein or Brown Swiss introgression are mostly significantly correlated with the corresponding test statistics from signatures of selection analyses in modern Danish Red Dairy Cattle. Meanwhile, the putative significant introgressed signals have a significant dependency with the putative significant signals from signatures of selection analyses. Artificial selection has played an important role in the genomic footprints of introgression in the genome of modern Danish Red Dairy Cattle. Our study on a modern cattle breed contributes to an understanding of genomic consequences of selective introgression by demonstrating the extent to which adaptive effects contribute to shape the specific genomic consequences of introgression.

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Dataset Information

Recovery of native genetic background in admixed populations using haplotypes, phenotypes, and pedigree information--using Cika cattle as a case breed.

Publications

Recovery of native genetic background in admixed populations using haplotypes, phenotypes, and pedigree information--using Cika cattle as a case breed.

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