title: Runs of homozygosity and distribution of functional variants in the cattle genome.
abstract: BACKGROUND
  Recent developments in sequencing technology have facilitated widespread investigations of genomic variants, including continuous stretches of homozygous genomic regions. For cattle, a large proportion of these runs of homozygosity (ROH) are likely the result of inbreeding due to the accumulation of elite alleles from long-term selective breeding programs. In the present study, ROH were characterized in four cattle breeds with whole genome sequence data and the distribution of predicted functional variants was detected in ROH regions and across different ROH length classes.
  
  
  RESULTS
  On average, 19.5% of the genome was located in ROH across four cattle breeds. There were an average of 715.5 ROH per genome with an average size of ~750 kbp, ranging from 10 (minimum size considered) to 49,290 kbp. There was a significant correlation between shared short ROH regions and regions putatively under selection (p < 0.001). By investigating the relationship between ROH and the predicted deleterious and non-deleterious variants, we gained insight into the distribution of functional variation in inbred (ROH) regions. Predicted deleterious variants were more enriched in ROH regions than predicted non-deleterious variants, which is consistent with observations in the human genome. We also found that increased enrichment of deleterious variants was significantly higher in short (<100 kbp) and medium (0.1 to 3 Mbp) ROH regions compared with long (>3 Mbp) ROH regions (P < 0.001), which is different than what has been observed in the human genome.
  
  
  CONCLUSIONS
  This study illustrates the distribution of ROH and functional variants within ROH in cattle populations. These patterns are different from those in the human genome but consistent with the natural history of cattle populations, which is confirmed by the significant correlation between shared short ROH regions and regions putatively under selection. These findings contribute to understanding the effects of inbreeding and probably selection in shaping the distribution of functional variants in the cattle genome.
authors.affiliation: Department of Molecular Biology and Genetics, Center for Quantitative Genetics and Genomics, Aarhus University, Tjele, DK-8830, Denmark. Qianqian.zhang@mbg.au.dk.|Animal Breeding and Genomics Centre, Wageningen UR Livestock Research, Wageningen, 6700 AH, The Netherlands. Qianqian.zhang@mbg.au.dk.
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Molecular Biology and Genetics, Center for Quantitative Genetics and Genomics, Aarhus University, Tjele, DK-8830, Denmark. Bernt.guldbrandtsen@mbg.au.dk.
authors.forename: Bernt
authors.initials: B
authors.lastname: Guldbrandtsen
authors.affiliation: Animal Breeding and Genomics Centre, Wageningen UR Livestock Research, Wageningen, 6700 AH, The Netherlands. Mirte.bosse@wur.nl.
authors.forename: Mirte
authors.initials: M
authors.lastname: Bosse
authors.affiliation: Department of Molecular Biology and Genetics, Center for Quantitative Genetics and Genomics, Aarhus University, Tjele, DK-8830, Denmark. Mogens.lund@mbg.au.dk.
authors.forename: Mogens S
authors.initials: MS
authors.lastname: Lund
authors.affiliation: Department of Molecular Biology and Genetics, Center for Quantitative Genetics and Genomics, Aarhus University, Tjele, DK-8830, Denmark. Goutam.sahana@mbg.au.dk.
authors.forename: Goutam
authors.initials: G
authors.lastname: Sahana
mesh_terms: D000483:Alleles; D000818:Animals; D001947:Breeding; D002417:Cattle; D005828:Genetics, Population; D015894:Genome, Human; D005838:Genotype; D006720:Homozygote; D006801:Humans; D007178:Inbreeding; D020641:Polymorphism, Single Nucleotide / Q000235:genetics