Tracing genetic resurrection of pointing dog breeds: Cesky Fousek as both survivor and rescuer

Evaluation of Genetic Diversity in Dog Breeds Using Pedigree and Molecular Analysis: A Review

Domestic dogs are important for many economic and social reasons, and they have become a well-known model species for human disease. According to research, dog breeds exhibit significant levels of inbreeding and genetic diversity loss, decreasing the population’s ability to adapt in certain conditions, and indicating the need of conservation strategies. Before the development of molecular markers, pedigree information was used for genetic diversity management. In recent years, genomic tools are frequently applied for accurate estimation of genetic diversity and improved genetic conservation due to incomplete pedigrees and pedigree errors. The most frequently used molecular markers include PCR-based microsatellite markers (STRs) and DNA sequencing-based single-nucleotide polymorphism markers (SNP). The aim of this review was to highlight genetic diversity studies on dog breeds conducted using pedigree and molecular markers, as well as the importance of genetic diversity conservation in increasing the adaptability and survival of dog breed populations.

Genomic and Transcriptomic Characterization of Atypical Recurrent Flank Alopecia in the Cesky Fousek

Non-inflammatory alopecia is a frequent skin problem in dogs, causing damaged coat integrity and compromised appearance of affected individuals. In this study, we examined the Cesky Fousek breed, which displays atypical recurrent flank alopecia (aRFA) at a high frequency. This type of alopecia can be quite severe and is characterized by seasonal episodes of well demarcated alopecic areas without hyperpigmentation. The genetic component responsible for aRFA remains unknown. Thus, here we aimed to identify variants involved in aRFA using a combination of histological, genomic, and transcriptomic data. We showed that aRFA is histologically similar to recurrent flank alopecia, characterized by a lack of anagen hair follicles and the presence of severely shortened telogen or kenogen hair follicles. We performed a genome-wide association study (GWAS) using 216 dogs phenotyped for aRFA and identified associations on chromosomes 19, 8, 30, 36, and 21, highlighting 144 candidate genes, which suggests a polygenic basis for aRFA. By comparing the skin cell transcription pattern of six aRFA and five control dogs, we identified 236 strongly differentially expressed genes (DEGs). We showed that the GWAS genes associated with aRFA are often predicted to interact with DEGs, suggesting their joint contribution to the development of the disease. Together, these genes affect four major metabolic pathways connected to aRFA: collagen formation, muscle structure/contraction, lipid metabolism, and the immune system.

Genetic Characterization of the Yugoslavian Shepherd Dog – Sharplanina, a Livestock Guard Dog from the Western Balkans

Yugoslavian Shepherd Dog - Sharplanina (YSD) is a livestock guard dog from the Western Balkans present in this region over a long time, but recognized by the Fédération Cynologique Internationale as a distinct breed as late as 1957. However, the information regarding the origin and the size of the breed’s foundation stock is still lacking. In order to contribute towards better understanding of the genetic make-up of the YSD and its foundation stock, we re-analyzed previously generated genetic profiles of 94 registered YSD dogs assessed with nine nuclear microsatellites. Studied individuals comprised 90 unrelated dogs and two pairs of full-sibs, sampled at four sampling sites: three dog shows and at a military training centre for dogs in Serbia. We supported earlier findings on high levels of genetic diversity in YSD (HE =0.728±0.027) and lack of inbreeding, and revealed substructure of the breed because we found two distinct gene pools in the Bayesian clustering analysis, indicated also by the excess of homozygotes (i.e., Wahlund effect) and outcomes of other analyses: linkage disequilibrium tests, Neighbour-Joining tree, principal coordinates and two-dimensional scaling analyses. The two gene pools were almost equally represented at each sampling site. One gene pool was composed of individuals with high genetic integrity, while the other gene pool was characterized with admixed ancestry, developed possibly via hybridization with native breeding stock outside the registry system, other breeds, such as the Caucasian Shepherd, and/or individuals admixed with wolves. Thus, we demonstrate rather complex and diverse ancestry implying a genetically heterogeneous foundation stock of the YSD.

Variation in breeding practices and geographic isolation drive subpopulation differentiation, contributing to the loss of genetic diversity within dog breed lineages

Background

Discrete breed ideals are not restricted to delimiting dog breeds from another, but also are key drivers of subpopulation differentiation. As genetic differentiation due to population fragmentation results in increased rates of inbreeding and loss of genetic diversity, detecting and alleviating the reasons of population fragmentation can provide effective tools for the maintenance of healthy dog breeds.

Results

Using a genome-wide SNP array, we detected genetic differentiation to subpopulations in six breeds, Belgian Shepherd, English Greyhound, Finnish Lapphund, Italian Greyhound, Labrador Retriever and Shetland Sheepdog, either due to geographical isolation or as a result of differential breeding strategies. The subpopulation differentiation was strongest in show dog lineages.

Conclusions

Besides geographical differentiation caused by founder effect and lack of gene flow, selection on champion looks or restricted pedigrees is a strong driver of population fragmentation. Artificial barriers for gene flow between the different subpopulations should be recognized, their necessity evaluated critically and perhaps abolished in order to maintain genetic diversity within a breed. Subpopulation differentiation might also result in false positive signals in genome-wide association studies of different traits.

Lay summary

Purebred dogs are, by definition, reproductively isolated from other breeds. However, similar isolation can also occur within a breed due to conflicting breeder ideals and geographic distances between the dog populations. We show here that both of these examples can contribute to breed division, with subsequent loss of genetic variation in the resulting breed lineages. Breeders should avoid creating unnecessary boundaries between breed lineages and facilitate the exchange of dogs between countries.