Population structure of Leonberger dogs

Presenter Anna Letko
Authors Letko A. (1), Minor K.M. (2), Mickelson J.R. (2), Seefried F.R. (3), Drögemüller C. (1)
Affiliations 1. Institute of Genetics, University of Bern, Switzerland, 2. Department of Veterinary and Biomedical Sciences, University of Minnesota, USA, 3. Qualitas AG, Zug, Switzerland
Presentation Type Poster


The Leonberger is a giant dog breed formed in the 1850s in Germany. This breed appears to have higher predisposition to neurodegenerative disorders and osteosarcoma than other breeds. Every second polyneuropathy-diagnosed Leonberger can be explained by dominantly inherited ARHGEF10 or GJA9 variants and a recently described recessive NAPEPLD variant identifies a juvenile-onset leukoencephalomyelopathy. Breeders also report shorter lifespan and lower fertility in Leonberger dogs. These problems, combined, imply inbreeding depression. We assessed the genetic diversity of the Leonberger population from extensive pedigree data (including more than 145,000 animals) as well as single nucleotide polymorphism (SNP) genotypes based on 170K array data of 1,175 dogs.
Pedigree analysis was done using open source software EVA v3.0. The completeness index over 5 generations of available pedigrees was above 99% for animals from the latest cohorts and exceeded 80% in 1935. We identified 18 founder animals in the population and a severe bottleneck during the 1940s with only 17 inbred dogs registered in 1946. Since the year 2000 approximately 4,400 dogs are born every year worldwide. The average litter size across cohorts was 6.5 puppies and a constant generation interval of 4 years was observed. The average inbreeding coefficient F was estimated to be 0.31 with a maxF of 0.60. The popular sire effect is apparent since a quarter of all sires produces two thirds of all offspring and the three top males sired more than 330 registered animals each. Additionally, SNP array data of 1,175 individuals sampled worldwide were investigated. These animals represent the current population of Leonberger well and therefore subpopulations were expected due to large geographic distances between breeders. However, principal component analysis was carried out and revealed no significant clustering. Additionally, a high level of homozygosity was observed.
Despite increasing population size observed in last cohorts, considerable genetic diversity has been lost due to the bottleneck in the last century. The use of popular sires and high level of inbreeding may have facilitated undesirable genetic traits to spread rapidly within the gene pool of the Leonberger population. Maintaining the genetic diversity is possible through informed selection decisions (especially to include more animals in breeding practice, avoid the use of popular sires and aim to minimize inbreeding) which would contribute to reduce the incidence of health problems.