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Forutan M, Ansari Mahyari S, Baes C, Melzer N, Schenkel FS, Sargolzaei M. Inbreeding and runs of homozygosity before and after genomic selection in North American Holstein cattle. BMC Genomics 2018; 19:98. [PMID: 29374456 PMCID: PMC5787230 DOI: 10.1186/s12864-018-4453-z] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 01/15/2018] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND While autozygosity as a consequence of selection is well understood, there is limited information on the ability of different methods to measure true inbreeding. In the present study, a gene dropping simulation was performed and inbreeding estimates based on runs of homozygosity (ROH), pedigree, and the genomic relationship matrix were compared to true inbreeding. Inbreeding based on ROH was estimated using SNP1101, PLINK, and BCFtools software with different threshold parameters. The effects of different selection methods on ROH patterns were also compared. Furthermore, inbreeding coefficients were estimated in a sample of genotyped North American Holstein animals born from 1990 to 2016 using 50 k chip data and ROH patterns were assessed before and after genomic selection. RESULTS Using ROH with a minimum window size of 20 to 50 using SNP1101 provided the closest estimates to true inbreeding in simulation study. Pedigree inbreeding tended to underestimate true inbreeding, and results for genomic inbreeding varied depending on assumptions about base allele frequencies. Using an ROH approach also made it possible to assess the effect of population structure and selection on distribution of runs of autozygosity across the genome. In the simulation, the longest individual ROH and the largest average length of ROH were observed when selection was based on best linear unbiased prediction (BLUP), whereas genomic selection showed the largest number of small ROH compared to BLUP estimated breeding values (BLUP-EBV). In North American Holsteins, the average number of ROH segments of 1 Mb or more per individual increased from 57 in 1990 to 82 in 2016. The rate of increase in the last 5 years was almost double that of previous 5 year periods. Genomic selection results in less autozygosity per generation, but more per year given the reduced generation interval. CONCLUSIONS This study shows that existing software based on the measurement of ROH can accurately identify autozygosity across the genome, provided appropriate threshold parameters are used. Our results show how different selection strategies affect the distribution of ROH, and how the distribution of ROH has changed in the North American dairy cattle population over the last 25 years.
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Affiliation(s)
- Mehrnush Forutan
- Department of Animal Science, College of Agriculture, Isfahan University of Technology, Khomeyni Shahr, Iran
- Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, Canada
| | - Saeid Ansari Mahyari
- Department of Animal Science, College of Agriculture, Isfahan University of Technology, Khomeyni Shahr, Iran
| | - Christine Baes
- Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, Canada
| | - Nina Melzer
- Institute of Genetics and Biometry, Leibniz Institute for Farm Animal Biology, Dummerstorf, Germany
| | - Flavio Schramm Schenkel
- Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, Canada
| | - Mehdi Sargolzaei
- Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, Canada
- Semex Alliance, Guelph, Canada
- HiggsGene Solutions Inc., Guelph, Canada
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152
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Mastrangelo S, Ciani E, Sardina MT, Sottile G, Pilla F, Portolano B. Runs of homozygosity reveal genome-wide autozygosity in Italian sheep breeds. Anim Genet 2018; 49:71-81. [PMID: 29333609 DOI: 10.1111/age.12634] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2017] [Indexed: 02/03/2023]
Abstract
The availability of dense single nucleotide polymorphism (SNP) assays allows for the determination of autozygous segments based on runs of consecutive homozygous genotypes (ROH). The aim of the present study was to investigate the occurrence and distribution of ROH in 21 Italian sheep breeds using medium-density SNP genotypes in order to characterize autozygosity and identify genomic regions that frequently appeared in ROH within individuals, namely ROH islands. After filtering, the final number of animals and SNPs retained for analyses were 502 and 46 277 respectively. A total of 12 302 ROH were identified. The mean number of ROH per breed ranged from 10.58 (Comisana) to 44.54 (Valle del Belice). The average length of ROH across breeds was 4.55 Mb and ranged from 3.85 Mb (Biellese) to 5.51 Mb (Leccese). Valle del Belice showed the highest value of inbreeding on the basis of ROH (FROH = 0.099), whereas Comisana showed the lowest (FROH = 0.016), and high standard deviation values revealed high variability in autozygosity levels within each breed. Differences also existed in the length of ROH. Analysis of the distribution of ROH according to their size showed that, for all breeds, the majority of the detected ROH were <10 Mb in length, with a few long ROH >25 Mb. The levels of ROH that we estimated here reflect the inbreeding history of the investigated sheep breeds. These results also highlight that ancient and recent inbreeding have had an impact on the genome of the Italian sheep breeds and suggest that several animals have experienced recent autozygosity events. Comisana and Bergamasca appeared as the less consanguineous breeds, whereas Barbaresca, Leccese and Valle del Belice showed ROH patterns typically produced by recent inbreeding. Moreover, within the genomic regions most commonly associated with ROH, several candidate genes were detected.
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Affiliation(s)
- S Mastrangelo
- Dipartimento Scienze Agrarie, Alimentari e Forestali, University of Palermo, 90128, Palermo, Italy
| | - E Ciani
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica University of Bari, 70124, Bari, Italy
| | - M T Sardina
- Dipartimento Scienze Agrarie, Alimentari e Forestali, University of Palermo, 90128, Palermo, Italy
| | - G Sottile
- Dipartimento Scienze Economiche, Aziendali e Statistiche, University of Palermo, 90128, Palermo, Italy
| | - F Pilla
- Dipartimento Agricoltura, Ambiente e Alimenti, University of Molise, 86100, Campobasso, Italy
| | - B Portolano
- Dipartimento Scienze Agrarie, Alimentari e Forestali, University of Palermo, 90128, Palermo, Italy
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153
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Peripolli E, Stafuzza NB, Munari DP, Lima ALF, Irgang R, Machado MA, Panetto JCDC, Ventura RV, Baldi F, da Silva MVGB. Assessment of runs of homozygosity islands and estimates of genomic inbreeding in Gyr (Bos indicus) dairy cattle. BMC Genomics 2018; 19:34. [PMID: 29316879 PMCID: PMC5759835 DOI: 10.1186/s12864-017-4365-3] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 12/04/2017] [Indexed: 11/10/2022] Open
Abstract
Background Runs of homozygosity (ROH) are continuous homozygous segments of the DNA sequence. They have been applied to quantify individual autozygosity and used as a potential inbreeding measure in livestock species. The aim of the present study was (i) to investigate genome-wide autozygosity to identify and characterize ROH patterns in Gyr dairy cattle genome; (ii) identify ROH islands for gene content and enrichment in segments shared by more than 50% of the samples, and (iii) compare estimates of molecular inbreeding calculated from ROH (FROH), genomic relationship matrix approach (FGRM) and based on the observed versus expected number of homozygous genotypes (FHOM), and from pedigree-based coefficient (FPED). Results ROH were identified in all animals, with an average number of 55.12 ± 10.37 segments and a mean length of 3.17 Mb. Short segments (ROH1–2 Mb) were abundant through the genomes, which accounted for 60% of all segments identified, even though the proportion of the genome covered by them was relatively small. The findings obtained in this study suggest that on average 7.01% (175.28 Mb) of the genome of this population is autozygous. Overlapping ROH were evident across the genomes and 14 regions were identified with ROH frequencies exceeding 50% of the whole population. Genes associated with lactation (TRAPPC9), milk yield and composition (IRS2 and ANG), and heat adaptation (HSF1, HSPB1, and HSPE1), were identified. Inbreeding coefficients were estimated through the application of FROH, FGRM, FHOM, and FPED approaches. FPED estimates ranged from 0.00 to 0.327 and FROH from 0.001 to 0.201. Low to moderate correlations were observed between FPED-FROH and FGRM-FROH, with values ranging from −0.11 to 0.51. Low to high correlations were observed between FROH-FHOM and moderate between FPED-FHOM and FGRM-FHOM. Correlations between FROH from different lengths and FPED gradually increased with ROH length. Conclusions Genes inside ROH islands suggest a strong selection for dairy traits and enrichment for Gyr cattle environmental adaptation. Furthermore, low FPED-FROH correlations for small segments indicate that FPED estimates are not the most suitable method to capture ancient inbreeding. The existence of a moderate correlation between larger ROH indicates that FROH can be used as an alternative to inbreeding estimates in the absence of pedigree records. Electronic supplementary material The online version of this article (10.1186/s12864-017-4365-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Elisa Peripolli
- Faculdade de Ciências Agrárias e Veterinárias, Departamento de Zootecnia, UNESP Univ Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, 14884-900, Brazil
| | - Nedenia Bonvino Stafuzza
- Faculdade de Ciências Agrárias e Veterinárias, Departamento de Ciências Exatas, UNESP Univ Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, 14884-900, Brazil
| | - Danísio Prado Munari
- Faculdade de Ciências Agrárias e Veterinárias, Departamento de Ciências Exatas, UNESP Univ Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, 14884-900, Brazil.,Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ), Lago Sul, 71605-001, Brazil
| | - André Luís Ferreira Lima
- Centro de Ciências Agrárias, Departamento de Zootecnia e Desenvolvimento Rural, Universidade Federal de Santa Catarina, Florianópolis, 88034-000, Brazil
| | - Renato Irgang
- Centro de Ciências Agrárias, Departamento de Zootecnia e Desenvolvimento Rural, Universidade Federal de Santa Catarina, Florianópolis, 88034-000, Brazil
| | - Marco Antonio Machado
- Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ), Lago Sul, 71605-001, Brazil.,Embrapa Gado de Leite, Juiz de Fora, 36038-330, Brazil
| | | | - Ricardo Vieira Ventura
- Faculdade de Zootecnia e Engenharia de Alimentos, Universidade de São Paulo, Pirassununga, 13635-900, Brazil.,Beef Improvement Opportunities, Elora, ON, N0B 1S0, Canada.,University of Guelph, Centre for Genetic Improvement of Livestock, ABScBG, Guelph, N1G 2W1, Canada
| | - Fernando Baldi
- Faculdade de Ciências Agrárias e Veterinárias, Departamento de Zootecnia, UNESP Univ Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, 14884-900, Brazil.,Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ), Lago Sul, 71605-001, Brazil
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154
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Druml T, Neuditschko M, Grilz-Seger G, Horna M, Ricard A, Mesarič M, Cotman M, Pausch H, Brem G. Population Networks Associated with Runs of Homozygosity Reveal New Insights into the Breeding History of the Haflinger Horse. J Hered 2017; 109:384-392. [DOI: 10.1093/jhered/esx114] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 12/23/2017] [Indexed: 02/04/2023] Open
Affiliation(s)
- Thomas Druml
- Institute of Animal Breeding and Genetics, University of Veterinary Sciences Vienna, Vienna, Austria
| | | | | | - Michaela Horna
- Department of Animal Husbandry, Slovak University of Agriculture in Nitra, Nitra-Chrenová, Slovak Republic
| | - Anne Ricard
- Institut National de la Recherche Agronomique, UMR 1313 Génétique Animale et Biologie Intégrative, Jouy-en-Josas, France
- Institut Français du Cheval et de l’Equitation, Recherche et Innovation, Exmes, France
| | - Matjaz Mesarič
- Clinic for Reproduction and Large Animals, Veterinary Faculty, University of Lubljana, Cesta v Mestni log, Ljubljana, Slovenia
| | - Marco Cotman
- Institute of Preclinical Sciences, Veterinary Faculty, University of Ljubljana, Cesta v Mestni log, Ljubljana, Slovenia
| | | | - Gottfried Brem
- Institute of Animal Breeding and Genetics, University of Veterinary Sciences Vienna, Vienna, Austria
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155
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Solé M, Gori AS, Faux P, Bertrand A, Farnir F, Gautier M, Druet T. Age-based partitioning of individual genomic inbreeding levels in Belgian Blue cattle. Genet Sel Evol 2017; 49:92. [PMID: 29273000 PMCID: PMC5741860 DOI: 10.1186/s12711-017-0370-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 12/13/2017] [Indexed: 11/21/2022] Open
Abstract
Background
Inbreeding coefficients can be estimated either from pedigree data or from genomic data, and with genomic data, they are either global or local (when the linkage map is used). Recently, we developed a new hidden Markov model (HMM) that estimates probabilities of homozygosity-by-descent (HBD) at each marker position and automatically partitions autozygosity in multiple age-related classes (based on the length of HBD segments). Our objectives were to: (1) characterize inbreeding with our model in an intensively selected population such as the Belgian Blue Beef (BBB) cattle breed; (2) compare the properties of the model at different marker densities; and (3) compare our model with other methods.
Results When using 600 K single nucleotide polymorphisms (SNPs), the inbreeding coefficient (probability of sampling an HBD locus in an individual) was on average 0.303 (ranging from 0.258 to 0.375). HBD-classes associated to historical ancestors (with small segments ≤ 200 kb) accounted for 21.6% of the genome length (71.4% of the total length of the genome in HBD segments), whereas classes associated to more recent ancestors accounted for only 22.6% of the total length of the genome in HBD segments. However, these recent classes presented more individual variation than more ancient classes. Although inbreeding coefficients obtained with low SNP densities (7 and 32 K) were much lower (0.060 and 0.093), they were highly correlated with those obtained at higher density (r = 0.934 and 0.975, respectively), indicating that they captured most of the individual variation. At higher SNP density, smaller HBD segments are identified and, thus, more past generations can be explored. We observed very high correlations between our estimates and those based on homozygosity (r = 0.95) or on runs-of-homozygosity (r = 0.95). As expected, pedigree-based estimates were mainly correlated with recent HBD-classes (r = 0.56). Conclusions Although we observed high levels of autozygosity associated with small HBD segments in BBB cattle, recent inbreeding accounted for most of the individual variation. Recent autozygosity can be captured efficiently with low-density SNP arrays and relatively simple models (e.g., two HBD classes). The HMM framework provides local HBD probabilities that are still useful at lower SNP densities. Electronic supplementary material The online version of this article (10.1186/s12711-017-0370-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Marina Solé
- Unit of Animal Genomics, GIGA-R & Faculty of Veterinary Medicine, University of Liège, B34 (+1) Avenue de l'Hôpital 1, 4000, Liège, Belgium.
| | - Ann-Stephan Gori
- Unit of Animal Genomics, GIGA-R & Faculty of Veterinary Medicine, University of Liège, B34 (+1) Avenue de l'Hôpital 1, 4000, Liège, Belgium.,Awé Coopérative (Association Wallonne de l'Élevage) - Recherche et Développement, Rue des Champs Elysées 4, 5590, Ciney, Belgium
| | - Pierre Faux
- Unit of Animal Genomics, GIGA-R & Faculty of Veterinary Medicine, University of Liège, B34 (+1) Avenue de l'Hôpital 1, 4000, Liège, Belgium
| | - Amandine Bertrand
- Unit of Animal Genomics, GIGA-R & Faculty of Veterinary Medicine, University of Liège, B34 (+1) Avenue de l'Hôpital 1, 4000, Liège, Belgium
| | - Frédéric Farnir
- BBASV, FARAH-PAD & Faculty of Veterinary Medicine, University of Liège, Quartier Vallée 2, Avenue de Cureghem, (B43 +3), 4000, Liège, Belgium
| | - Mathieu Gautier
- INRA, UMR CBGP (Centre de Biologie pour la Gestion des Populations), Campus International de Baillarguet, 34988, Montferrier sur Lez, France.,IBD (Institut de Biologie Computationnelle), 34095, Montpellier, France
| | - Tom Druet
- Unit of Animal Genomics, GIGA-R & Faculty of Veterinary Medicine, University of Liège, B34 (+1) Avenue de l'Hôpital 1, 4000, Liège, Belgium
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156
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Blant A, Kwong M, Szpiech ZA, Pemberton TJ. Weighted likelihood inference of genomic autozygosity patterns in dense genotype data. BMC Genomics 2017; 18:928. [PMID: 29191164 PMCID: PMC5709839 DOI: 10.1186/s12864-017-4312-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 11/16/2017] [Indexed: 12/14/2022] Open
Abstract
Background Genomic regions of autozygosity (ROA) arise when an individual is homozygous for haplotypes inherited identical-by-descent from ancestors shared by both parents. Over the past decade, they have gained importance for understanding evolutionary history and the genetic basis of complex diseases and traits. However, methods to infer ROA in dense genotype data have not evolved in step with advances in genome technology that now enable us to rapidly create large high-resolution genotype datasets, limiting our ability to investigate their constituent ROA patterns. Methods We report a weighted likelihood approach for inferring ROA in dense genotype data that accounts for autocorrelation among genotyped positions and the possibilities of unobserved mutation and recombination events, and variability in the confidence of individual genotype calls in whole genome sequence (WGS) data. Results Forward-time genetic simulations under two demographic scenarios that reflect situations where inbreeding and its effect on fitness are of interest suggest this approach is better powered than existing state-of-the-art methods to infer ROA at marker densities consistent with WGS and popular microarray genotyping platforms used in human and non-human studies. Moreover, we present evidence that suggests this approach is able to distinguish ROA arising via consanguinity from ROA arising via endogamy. Using subsets of The 1000 Genomes Project Phase 3 data we show that, relative to WGS, intermediate and long ROA are captured robustly with popular microarray platforms, while detection of short ROA is more variable and improves with marker density. Worldwide ROA patterns inferred from WGS data are found to accord well with those previously reported on the basis of microarray genotype data. Finally, we highlight the potential of this approach to detect genomic regions enriched for autozygosity signals in one group relative to another based upon comparisons of per-individual autozygosity likelihoods instead of inferred ROA frequencies. Conclusions This weighted likelihood ROA inference approach can assist population- and disease-geneticists working with a wide variety of data types and species to explore ROA patterns and to identify genomic regions with differential ROA signals among groups, thereby advancing our understanding of evolutionary history and the role of recessive variation in phenotypic variation and disease. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-4312-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Alexandra Blant
- Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB, Canada
| | - Michelle Kwong
- Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB, Canada
| | - Zachary A Szpiech
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, USA
| | - Trevor J Pemberton
- Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB, Canada.
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157
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Mastrangelo S, Tolone M, Sardina MT, Sottile G, Sutera AM, Di Gerlando R, Portolano B. Genome-wide scan for runs of homozygosity identifies potential candidate genes associated with local adaptation in Valle del Belice sheep. Genet Sel Evol 2017; 49:84. [PMID: 29137622 PMCID: PMC5684758 DOI: 10.1186/s12711-017-0360-z] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 11/07/2017] [Indexed: 11/23/2022] Open
Abstract
Background Because very large numbers of single nucleotide polymorphisms (SNPs) are now available throughout the genome, they are particularly suitable for the detection of genomic regions where a reduction in heterozygosity has occurred and they offer new opportunities to improve the accuracy of inbreeding (\documentclass[12pt]{minimal}
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\begin{document}$$F$$\end{document}F) estimates. Runs of homozygosity (ROH) are contiguous lengths of homozygous segments of the genome where the two haplotypes inherited from the parents are identical. Here, we investigated the occurrence and distribution of ROH using a medium-dense SNP panel to characterize autozygosity in 516 Valle del Belice sheep and to identify the genomic regions with high ROH frequencies. Results We identified 11,629 ROH and all individuals displayed at least one ROH longer than 1 Mb. The mean value of \documentclass[12pt]{minimal}
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\begin{document}$$F$$\end{document}F estimated from ROH longer than1 Mb was 0.084 ± 0.061. ROH that were shorter than 10 Mb predominated. The highest and lowest coverages of Ovis aries chromosomes (OAR) by ROH were on OAR24 and OAR1, respectively. The number of ROH per chromosome length displayed a specific pattern, with higher values for the first three chromosomes. Both number of ROH and length of the genome covered by ROH varied considerably between animals. Two hundred and thirty-nine SNPs were considered as candidate markers that may be under directional selection and we identified 107 potential candidate genes. Six genomic regions located on six chromosomes, corresponding to ROH islands, are presented as hotspots of autozygosity, which frequently coincided with regions of medium recombination rate. According to the KEGG database, most of these genes were involved in multiple signaling and signal transduction pathways in a wide variety of cellular and biochemical processes. A genome scan revealed the presence of ROH islands in genomic regions that harbor candidate genes for selection in response to environmental stress and which underlie local adaptation. Conclusions These results suggest that natural selection has, at least partially, a role in shaping the genome of Valle del Belice sheep and that ROH in the ovine genome may help to detect genomic regions involved in the determinism of traits under selection. Electronic supplementary material The online version of this article (10.1186/s12711-017-0360-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Salvatore Mastrangelo
- Dipartimento Scienze Agrarie, Alimentari e Forestali, Università degli Studi di Palermo, 90128, Palermo, Italy.
| | - Marco Tolone
- Dipartimento Scienze Agrarie, Alimentari e Forestali, Università degli Studi di Palermo, 90128, Palermo, Italy
| | - Maria T Sardina
- Dipartimento Scienze Agrarie, Alimentari e Forestali, Università degli Studi di Palermo, 90128, Palermo, Italy
| | - Gianluca Sottile
- Dipartimento di Scienze Economiche, Aziendali e Statistiche, Università degli Studi di Palermo, 90128, Palermo, Italy
| | - Anna M Sutera
- Dipartimento Scienze Agrarie, Alimentari e Forestali, Università degli Studi di Palermo, 90128, Palermo, Italy
| | - Rosalia Di Gerlando
- Dipartimento Scienze Agrarie, Alimentari e Forestali, Università degli Studi di Palermo, 90128, Palermo, Italy
| | - Baldassare Portolano
- Dipartimento Scienze Agrarie, Alimentari e Forestali, Università degli Studi di Palermo, 90128, Palermo, Italy
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158
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Signer-Hasler H, Burren A, Neuditschko M, Frischknecht M, Garrick D, Stricker C, Gredler B, Bapst B, Flury C. Population structure and genomic inbreeding in nine Swiss dairy cattle populations. Genet Sel Evol 2017; 49:83. [PMID: 29115934 PMCID: PMC5674839 DOI: 10.1186/s12711-017-0358-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 10/26/2017] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Domestication, breed formation and intensive selection have resulted in divergent cattle breeds that likely exhibit their own genomic signatures. In this study, we used genotypes from 27,612 autosomal single nucleotide polymorphisms to characterize population structure based on 9214 sires representing nine Swiss dairy cattle populations: Brown Swiss (BS), Braunvieh (BV), Original Braunvieh (OB), Holstein (HO), Red Holstein (RH), Swiss Fleckvieh (SF), Simmental (SI), Eringer (ER) and Evolèner (EV). Genomic inbreeding (F ROH) and signatures of selection were determined by calculating runs of homozygosity (ROH). The results build the basis for a better understanding of the genetic development of Swiss dairy cattle populations and highlight differences between the original populations (i.e. OB, SI, ER and EV) and those that have become more popular in Switzerland as currently reflected by their larger populations (i.e. BS, BV, HO, RH and SF). RESULTS The levels of genetic diversity were highest and lowest in the SF and BS breeds, respectively. Based on F ST values, we conclude that, among all pairwise comparisons, BS and HO (0.156) differ more than the other pairs of populations. The original Swiss cattle populations OB, SI, ER, and EV are clearly genetically separated from the Swiss cattle populations that are now more common and represented by larger numbers of cows. Mean levels of F ROH ranged from 0.027 (ER) to 0.091 (BS). Three of the original Swiss cattle populations, ER (F ROH: 0.027), OB (F ROH: 0.029), and SI (F ROH: 0.039), showed low levels of genomic inbreeding, whereas it was much higher in EV (F ROH: 0.074). Private signatures of selection for the original Swiss cattle populations are reported for BTA4, 5, 11 and 26. CONCLUSIONS The low levels of genomic inbreeding observed in the original Swiss cattle populations ER, OB and SI compared to the other breeds are explained by a lesser use of artificial insemination and greater use of natural service. Natural service results in more sires having progeny at each generation and thus this breeding practice is likely the major reason for the remarkable levels of genetic diversity retained within these populations. The fact that the EV population is regionally restricted and its small census size of herd-book cows explain its high level of genomic inbreeding.
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Affiliation(s)
- Heidi Signer-Hasler
- School of Agricultural, Forest and Food Sciences, Bern University of Applied Sciences, Zollikofen, Switzerland
| | - Alexander Burren
- School of Agricultural, Forest and Food Sciences, Bern University of Applied Sciences, Zollikofen, Switzerland
| | | | - Mirjam Frischknecht
- School of Agricultural, Forest and Food Sciences, Bern University of Applied Sciences, Zollikofen, Switzerland
- Qualitas AG, Zug, Switzerland
| | | | | | | | | | - Christine Flury
- School of Agricultural, Forest and Food Sciences, Bern University of Applied Sciences, Zollikofen, Switzerland
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159
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Purfield DC, McParland S, Wall E, Berry DP. The distribution of runs of homozygosity and selection signatures in six commercial meat sheep breeds. PLoS One 2017; 12:e0176780. [PMID: 28463982 PMCID: PMC5413029 DOI: 10.1371/journal.pone.0176780] [Citation(s) in RCA: 155] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 04/17/2017] [Indexed: 11/18/2022] Open
Abstract
Domestication and the subsequent selection of animals for either economic or morphological features can leave a variety of imprints on the genome of a population. Genomic regions subjected to high selective pressures often show reduced genetic diversity and frequent runs of homozygosity (ROH). Therefore, the objective of the present study was to use 42,182 autosomal SNPs to identify genomic regions in 3,191 sheep from six commercial breeds subjected to selection pressure and to quantify the genetic diversity within each breed using ROH. In addition, the historical effective population size of each breed was also estimated and, in conjunction with ROH, was used to elucidate the demographic history of the six breeds. ROH were common in the autosomes of animals in the present study, but the observed breed differences in patterns of ROH length and burden suggested differences in breed effective population size and recent management. ROH provided a sufficient predictor of the pedigree inbreeding coefficient, with an estimated correlation between both measures of 0.62. Genomic regions under putative selection were identified using two complementary algorithms; the fixation index and hapFLK. The identified regions under putative selection included candidate genes associated with skin pigmentation, body size and muscle formation; such characteristics are often sought after in modern-day breeding programs. These regions of selection frequently overlapped with high ROH regions both within and across breeds. Multiple yet uncharacterised genes also resided within putative regions of selection. This further substantiates the need for a more comprehensive annotation of the sheep genome as these uncharacterised genes may contribute to traits of interest in the animal sciences. Despite this, the regions identified as under putative selection in the current study provide an insight into the mechanisms leading to breed differentiation and genetic variation in meat production.
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Affiliation(s)
- Deirdre C. Purfield
- Animal & Grassland Research and Innovation Center, Teagasc, Moorepark, Fermoy, Co. Cork, Ireland
- * E-mail:
| | - Sinead McParland
- Animal & Grassland Research and Innovation Center, Teagasc, Moorepark, Fermoy, Co. Cork, Ireland
| | - Eamon Wall
- Sheep Ireland, Bandon, Co. Cork, Ireland
| | - Donagh P. Berry
- Animal & Grassland Research and Innovation Center, Teagasc, Moorepark, Fermoy, Co. Cork, Ireland
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160
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Brito LF, Kijas JW, Ventura RV, Sargolzaei M, Porto-Neto LR, Cánovas A, Feng Z, Jafarikia M, Schenkel FS. Genetic diversity and signatures of selection in various goat breeds revealed by genome-wide SNP markers. BMC Genomics 2017; 18:229. [PMID: 28288562 PMCID: PMC5348779 DOI: 10.1186/s12864-017-3610-0] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 03/07/2017] [Indexed: 01/08/2023] Open
Abstract
Background The detection of signatures of selection has the potential to elucidate the identities of genes and mutations associated with phenotypic traits important for livestock species. It is also very relevant to investigate the levels of genetic diversity of a population, as genetic diversity represents the raw material essential for breeding and has practical implications for implementation of genomic selection. A total of 1151 animals from nine goat populations selected for different breeding goals and genotyped with the Illumina Goat 50K single nucleotide polymorphisms (SNP) Beadchip were included in this investigation. Results The proportion of polymorphic SNPs ranged from 0.902 (Nubian) to 0.995 (Rangeland). The overall mean HO and HE was 0.374 ± 0.021 and 0.369 ± 0.023, respectively. The average pairwise genetic distance (D) ranged from 0.263 (Toggenburg) to 0.323 (Rangeland). The overall average for the inbreeding measures FEH, FVR, FLEUT, FROH and FPED was 0.129, −0.012, −0.010, 0.038 and 0.030, respectively. Several regions located on 19 chromosomes were potentially under selection in at least one of the goat breeds. The genomic population tree constructed using all SNPs differentiated breeds based on selection purpose, while genomic population tree built using only SNPs in the most significant region showed a great differentiation between LaMancha and the other breeds. We hypothesized that this region is related to ear morphogenesis. Furthermore, we identified genes potentially related to reproduction traits, adult body mass, efficiency of food conversion, abdominal fat deposition, conformation traits, liver fat metabolism, milk fatty acids, somatic cells score, milk protein, thermo-tolerance and ear morphogenesis. Conclusions In general, moderate to high levels of genetic variability were observed for all the breeds and a characterization of runs of homozygosity gave insights into the breeds’ development history. The information reported here will be useful for the implementation of genomic selection and other genomic studies in goats. We also identified various genome regions under positive selection using smoothed FST and hapFLK statistics and suggested genes, which are potentially under selection. These results can now provide a foundation to formulate biological hypotheses related to selection processes in goats. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3610-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Luiz F Brito
- Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, Ontario, Canada.
| | - James W Kijas
- CSIRO Agriculture & Food, Brisbane, Queensland, Australia
| | - Ricardo V Ventura
- Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, Ontario, Canada.,Beef Improvement Opportunities, Guelph, Ontario, Canada
| | - Mehdi Sargolzaei
- Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, Ontario, Canada.,The Semex Alliance, Guelph, Ontario, Canada
| | | | - Angela Cánovas
- Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, Ontario, Canada
| | - Zeny Feng
- Department of Mathematics and Statistics, University of Guelph, Guelph, Ontario, Canada
| | - Mohsen Jafarikia
- Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, Ontario, Canada.,Canadian Centre for Swine Improvement Inc., Ottawa, Ontario, Canada
| | - Flávio S Schenkel
- Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, Ontario, Canada
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161
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Peripolli E, Munari DP, Silva MVGB, Lima ALF, Irgang R, Baldi F. Runs of homozygosity: current knowledge and applications in livestock. Anim Genet 2016; 48:255-271. [PMID: 27910110 DOI: 10.1111/age.12526] [Citation(s) in RCA: 174] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/23/2016] [Indexed: 12/17/2022]
Abstract
This review presents a broader approach to the implementation and study of runs of homozygosity (ROH) in animal populations, focusing on identifying and characterizing ROH and their practical implications. ROH are continuous homozygous segments that are common in individuals and populations. The ability of these homozygous segments to give insight into a population's genetic events makes them a useful tool that can provide information about the demographic evolution of a population over time. Furthermore, ROH provide useful information about the genetic relatedness among individuals, helping to minimize the inbreeding rate and also helping to expose deleterious variants in the genome. The frequency, size and distribution of ROH in the genome are influenced by factors such as natural and artificial selection, recombination, linkage disequilibrium, population structure, mutation rate and inbreeding level. Calculating the inbreeding coefficient from molecular information from ROH (FROH ) is more accurate for estimating autozygosity and for detecting both past and more recent inbreeding effects than are estimates from pedigree data (FPED ). The better results of FROH suggest that FROH can be used to infer information about the history and inbreeding levels of a population in the absence of genealogical information. The selection of superior animals has produced large phenotypic changes and has reshaped the ROH patterns in various regions of the genome. Additionally, selection increases homozygosity around the target locus, and deleterious variants are seen to occur more frequently in ROH regions. Studies involving ROH are increasingly common and provide valuable information about how the genome's architecture can disclose a population's genetic background. By revealing the molecular changes in populations over time, genome-wide information is crucial to understanding antecedent genome architecture and, therefore, to maintaining diversity and fitness in endangered livestock breeds.
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Affiliation(s)
- E Peripolli
- Departamento de Zootecnia, Faculdade de Ciências Agrárias e Veterinárias, UNESP Univ Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, 14884-900, Brazil
| | - D P Munari
- Departamento de Ciências Exatas, Faculdade de Ciências Agrárias e Veterinárias, UNESP Univ Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, 14884-900, Brazil.,Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ), Lago Sul, 71605-001, Brazil
| | - M V G B Silva
- Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ), Lago Sul, 71605-001, Brazil.,Embrapa Gado de Leite, Juiz de Fora, 36038-330, Brazil
| | - A L F Lima
- Departamento de Zootecnia e Desenvolvimento Rural, Centro de Ciências Agrárias, Universidade Federal de Santa Catarina, Florianópolis, 88034-000, Brazil
| | - R Irgang
- Departamento de Zootecnia e Desenvolvimento Rural, Centro de Ciências Agrárias, Universidade Federal de Santa Catarina, Florianópolis, 88034-000, Brazil
| | - F Baldi
- Departamento de Zootecnia, Faculdade de Ciências Agrárias e Veterinárias, UNESP Univ Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, 14884-900, Brazil.,Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ), Lago Sul, 71605-001, Brazil
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162
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Marras G, Rossoni A, Schwarzenbacher H, Biffani S, Biscarini F, Nicolazzi EL. zanardi: an open-source pipeline for multiple-species genomic analysis of SNP array data. Anim Genet 2016; 48:121. [DOI: 10.1111/age.12485] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/04/2016] [Indexed: 11/27/2022]
Affiliation(s)
- Gabriele Marras
- Bioinformatics Core Facility; Fondazione Parco Tecnologico Padano; Loc. Cascina Codazza Lodi LO 26900 Italy
| | - Attilio Rossoni
- Associazione Nazionale Allevatori di Razza Bruna; Bussolengo VR 37012 Italy
| | | | | | - Filippo Biscarini
- Bioinformatics Core Facility; Fondazione Parco Tecnologico Padano; Loc. Cascina Codazza Lodi LO 26900 Italy
| | - Ezequiel L. Nicolazzi
- Bioinformatics Core Facility; Fondazione Parco Tecnologico Padano; Loc. Cascina Codazza Lodi LO 26900 Italy
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163
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Manunza A, Noce A, Serradilla JM, Goyache F, Martínez A, Capote J, Delgado JV, Jordana J, Muñoz E, Molina A, Landi V, Pons A, Balteanu V, Traoré A, Vidilla M, Sánchez-Rodríguez M, Sànchez A, Cardoso TF, Amills M. A genome-wide perspective about the diversity and demographic history of seven Spanish goat breeds. Genet Sel Evol 2016; 48:52. [PMID: 27455838 PMCID: PMC4960707 DOI: 10.1186/s12711-016-0229-6] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 06/29/2016] [Indexed: 12/19/2022] Open
Abstract
Background The main goal of the current work was to infer the demographic history of seven Spanish goat breeds (Malagueña, Murciano-Granadina, Florida, Palmera, Mallorquina, Bermeya and Blanca de Rasquera) based on genome-wide diversity data generated with the Illumina Goat SNP50 BeadChip (population size, N = 176). Five additional populations from Europe (Saanen and Carpathian) and Africa (Tunisian, Djallonké and Sahel) were also included in this analysis (N = 80) for comparative purposes. Results Our results show that the genetic background of Spanish goats traces back mainly to European breeds although signs of North African admixture were detected in two Andalusian breeds (Malagueña and Murciano-Granadina). In general, observed and expected heterozygosities were quite similar across the seven Spanish goat breeds under analysis irrespective of their population size and conservation status. For the Mallorquina and Blanca de Rasquera breeds, which have suffered strong population declines during the past decades, we observed increased frequencies of large-sized (ROH), a finding that is consistent with recent inbreeding. In contrast, a substantial part of the genome of the Palmera goat breed comprised short ROH, which suggests a strong and ancient founder effect. Conclusions Admixture with African goats, genetic drift and inbreeding have had different effects across the seven Spanish goat breeds analysed in the current work. This has generated distinct patterns of genome-wide diversity that provide new clues about the demographic history of these populations. Electronic supplementary material The online version of this article (doi:10.1186/s12711-016-0229-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Arianna Manunza
- Department of Animal Genetics, Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Campus Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain
| | - Antonia Noce
- Department of Animal Genetics, Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Campus Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain
| | | | - Félix Goyache
- Área de Genética y Reproducción Animal, SERIDA-Deva, Camino de Rioseco 1225, Gijón, 33394, Spain
| | - Amparo Martínez
- Departamento de Genética, Universidad de Córdoba, 14071, Córdoba, Spain
| | - Juan Capote
- Instituto Canario de Investigaciones Agrarias, 38108, La Laguna, Tenerife, Spain
| | | | - Jordi Jordana
- Departament de Ciència Animal i dels Aliments, Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain
| | - Eva Muñoz
- Departamento de Genética, Universidad de Córdoba, 14071, Córdoba, Spain
| | - Antonio Molina
- Departamento de Genética, Universidad de Córdoba, 14071, Córdoba, Spain
| | - Vincenzo Landi
- Departamento de Genética, Universidad de Córdoba, 14071, Córdoba, Spain
| | - Agueda Pons
- Unitat de Races Autòctones, Servei de Millora Agrària i Pesquera (SEMILLA), 07198, Son Ferriol, Spain
| | - Valentin Balteanu
- Faculty of Animal Science and Biotechnologies and Institute of Life Sciences, University of Agricultural Sciences and Veterinary Medicine, 400372, Cluj-Napoca, Romania
| | - Amadou Traoré
- Institut de l'Environnement et Recherches Agricoles, 04 BP 8645, Ouagadougou 04, Burkina Faso
| | - Montse Vidilla
- Associació de Ramaders de Cabra Blanca de Rasquera, Rasquera, 43513, Spain
| | | | - Armand Sànchez
- Department of Animal Genetics, Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Campus Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain.,Departament de Ciència Animal i dels Aliments, Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain
| | - Tainã Figueiredo Cardoso
- Department of Animal Genetics, Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Campus Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain
| | - Marcel Amills
- Department of Animal Genetics, Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Campus Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain. .,Departament de Ciència Animal i dels Aliments, Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain.
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164
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Gurgul A, Szmatoła T, Topolski P, Jasielczuk I, Żukowski K, Bugno-Poniewierska M. The use of runs of homozygosity for estimation of recent inbreeding in Holstein cattle. J Appl Genet 2016; 57:527-530. [DOI: 10.1007/s13353-016-0337-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 09/24/2015] [Accepted: 01/08/2016] [Indexed: 01/06/2023]
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165
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Genomic inbreeding estimation in small populations: evaluation of runs of homozygosity in three local dairy cattle breeds. Animal 2016; 10:746-54. [PMID: 27076405 DOI: 10.1017/s1751731115002943] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
In the local breeds with small population size, one of the most important problems is the increase of inbreeding coefficient (F). High levels of inbreeding lead to reduced genetic diversity and inbreeding depression. The availability of high-density single nucleotide polymorphism (SNP) arrays has facilitated the quantification of F by genomic markers in farm animals. Runs of homozygosity (ROH) are contiguous lengths of homozygous genotypes and represent an estimate of the degree of autozygosity at genome-wide level. The current study aims to quantify the genomic F derived from ROH (F ROH) in three local dairy cattle breeds. F ROH values were compared with F estimated from the genomic relationship matrix (F GRM), based on the difference between observed v. expected number of homozygous genotypes (F HOM) and the genomic homozygosity of individual i (F MOL i ). The molecular coancestry coefficient (f MOL ij ) between individuals i and j was also estimated. Individuals of Cinisara (71), Modicana (72) and Reggiana (168) were genotyped with the 50K v2 Illumina BeadChip. Genotypes from 96 animals of Italian Holstein cattle breed were also included in the analysis. We used a definition of ROH as tracts of homozygous genotypes that were >4 Mb. Among breeds, 3661 ROH were identified. Modicana showed the highest mean number of ROH per individual and the highest value of F ROH, whereas Reggiana showed the lowest ones. Differences among breeds existed for the ROH lengths. The individuals of Italian Holstein showed high number of short ROH segments, related to ancient consanguinity. Similar results showed the Reggiana with some extreme animals with segments covering 400 Mb and more of genome. Modicana and Cinisara showed similar results between them with the total length of ROH characterized by the presence of large segments. High correlation was found between F HOM and F ROH ranged from 0.83 in Reggiana to 0.95 in Cinisara and Modicana. The correlations among F ROH and other estimated F coefficients were generally lower ranged from 0.45 (F MOL i -F ROH) in Cinisara to 0.17 (F GRM-F ROH) in Modicana. On the basis of our results, recent inbreeding was observed in local breeds, considering that 16 Mb segments are expected to present inbreeding up to three generations ago. Our results showed the necessity of implementing conservation programs to control the rise of inbreeding and coancestry in the three Italian local dairy cattle breeds.
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166
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Karimi K, Esmailizadeh Koshkoiyeh A, Asadi Fozi M, Porto-Neto LR, Gondro C. Prioritization for conservation of Iranian native cattle breeds based on genome-wide SNP data. CONSERV GENET 2015. [DOI: 10.1007/s10592-015-0762-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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167
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Zhang Q, Calus MPL, Guldbrandtsen B, Lund MS, Sahana G. Estimation of inbreeding using pedigree, 50k SNP chip genotypes and full sequence data in three cattle breeds. BMC Genet 2015. [PMID: 26195126 PMCID: PMC4509611 DOI: 10.1186/s12863-015-0227-7] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Background Levels of inbreeding in cattle populations have increased in the past due to the use of a limited number of bulls for artificial insemination. High levels of inbreeding lead to reduced genetic diversity and inbreeding depression. Various estimators based on different sources, e.g., pedigree or genomic data, have been used to estimate inbreeding coefficients in cattle populations. However, the comparative advantage of using full sequence data to assess inbreeding is unknown. We used pedigree and genomic data at different densities from 50k to full sequence variants to compare how different methods performed for the estimation of inbreeding levels in three different cattle breeds. Results Five different estimates for inbreeding were calculated and compared in this study: pedigree based inbreeding coefficient (FPED); run of homozygosity (ROH)-based inbreeding coefficients (FROH); genomic relationship matrix (GRM)-based inbreeding coefficients (FGRM); inbreeding coefficients based on excess of homozygosity (FHOM) and correlation of uniting gametes (FUNI). Estimates using ROH provided the direct estimated levels of autozygosity in the current populations and are free effects of allele frequencies and incomplete pedigrees which may increase in inaccuracy in estimation of inbreeding. The highest correlations were observed between FROH estimated from the full sequence variants and the FROH estimated from 50k SNP (single nucleotide polymorphism) genotypes. The estimator based on the correlation between uniting gametes (FUNI) using full genome sequences was also strongly correlated with FROH detected from sequence data. Conclusions Estimates based on ROH directly reflected levels of homozygosity and were not influenced by allele frequencies, unlike the three other estimates evaluated (FGRM, FHOM and FUNI), which depended on estimated allele frequencies. FPED suffered from limited pedigree depth. Marker density affects ROH estimation. Detecting ROH based on 50k chip data was observed to give estimates similar to ROH from sequence data. In the absence of full sequence data ROH based on 50k can be used to access homozygosity levels in individuals. However, genotypes denser than 50k are required to accurately detect short ROH that are most likely identical by descent (IBD).
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Affiliation(s)
- Qianqian Zhang
- Department of Molecular Biology and Genetics, Center for Quantitative Genetics and Genomics, Aarhus University, Tjele, DK-8830, Denmark. .,Animal Breeding and Genomics Centre, Wageningen UR Livestock Research, Wageningen, 6700 AH, The Netherlands.
| | - Mario P L Calus
- Animal Breeding and Genomics Centre, Wageningen UR Livestock Research, Wageningen, 6700 AH, The Netherlands.
| | - Bernt Guldbrandtsen
- Department of Molecular Biology and Genetics, Center for Quantitative Genetics and Genomics, Aarhus University, Tjele, DK-8830, Denmark.
| | - Mogens S Lund
- Department of Molecular Biology and Genetics, Center for Quantitative Genetics and Genomics, Aarhus University, Tjele, DK-8830, Denmark.
| | - Goutam Sahana
- Department of Molecular Biology and Genetics, Center for Quantitative Genetics and Genomics, Aarhus University, Tjele, DK-8830, Denmark.
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