Open Access Highly Accessed Research article

A selective sweep of >8 Mb on chromosome 26 in the Boxer genome

Javier Quilez1*, Andrea D Short2, Verónica Martínez1, Lorna J Kennedy2, William Ollier2, Armand Sanchez1, Laura Altet1 and Olga Francino1

Author Affiliations

1 Molecular Genetics Veterinary Service (SVGM), Department of Animal and Food Science, Veterinary School, Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Barcelona, Spain

2 Centre for Integrated Genomic Medical Research (CIGMR), Stopford Building, Oxford Road, Manchester, M13 9PT, UK

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BMC Genomics 2011, 12:339  doi:10.1186/1471-2164-12-339

Published: 1 July 2011



Modern dog breeds display traits that are either breed-specific or shared by a few breeds as a result of genetic bottlenecks during the breed creation process and artificial selection for breed standards. Selective sweeps in the genome result from strong selection and can be detected as a reduction or elimination of polymorphism in a given region of the genome.


Extended regions of homozygosity, indicative of selective sweeps, were identified in a genome-wide scan dataset of 25 Boxers from the United Kingdom genotyped at ~20,000 single-nucleotide polymorphisms (SNPs). These regions were further examined in a second dataset of Boxers collected from a different geographical location and genotyped using higher density SNP arrays (~170,000 SNPs). A selective sweep previously associated with canine brachycephaly was detected on chromosome 1. A novel selective sweep of over 8 Mb was observed on chromosome 26 in Boxer and for a shorter region in English and French bulldogs. It was absent in 171 samples from eight other dog breeds and 7 Iberian wolf samples. A region of extended increased heterozygosity on chromosome 9 overlapped with a previously reported copy number variant (CNV) which was polymorphic in multiple dog breeds.


A selective sweep of more than 8 Mb on chromosome 26 was identified in the Boxer genome. This sweep is likely caused by strong artificial selection for a trait of interest and could have inadvertently led to undesired health implications for this breed. Furthermore, we provide supporting evidence for two previously described regions: a selective sweep on chromosome 1 associated with canine brachycephaly and a CNV on chromosome 9 polymorphic in multiple dog breeds.