Origin, genetic diversity, and genome structure of the domestic dog

Salivary protein homology between humans and dogs: Mass spectrometry-based proteomics analysis

OBJECTIVE

This benchmark study aimed to investigate sex-related differences based on the identification and characterization of the salivary proteome of healthy male and female dogs using mass spectrometry (MS) technique and a homology-driven approach to analyze salivary proteins in both human and dog species utilizing protein sequence alignment technique.

METHODS

Unstimulated whole saliva was collected from 10 healthy Beagles. After processing the samples and determining the total protein content, in-solution protein digestion was performed involving denaturation, reduction of disulfide bonds, alkylation, and removal of interfering compounds. Samples were analyzed using LC-ESI-MS/MS.

RESULTS

LC-ESI-MS/MS analysis identified 327 and 341 unique proteins in male and female dog saliva, respectively, of which 318 (97.25 %) in male dogs and 326 (95.60 %) in female dogs were characterized. Abundant shared proteins included albumin, BPI fold-containing family A member 2, and VWFD domain-containing protein. A notable uncharacterized protein, VWFD domain-containing protein, was among the most abundant in both sexes. Comparative analysis of 69 abundant shared proteins indicated an upregulation of CES5A, EFHD, GC, IGHM, LOC100653049, KRT10, LCP1, PGD, TPI1 in male dogs, while LOC100855593 was upregulated in female dogs. In total, 84 % (n = 229/274) and 86 % (n = 235/275) salivary proteins identified in male and female dogs, respectively, were homologous to human proteins, with an overall homology of 86 % (n = 364/423), including 15 with 100 % homology.

CONCLUSION

The study revealed clear differences in the salivary proteomics profile of healthy male and female dogs. However, most of the salivary proteins in both male and female dogs showed homology with human salivary proteins.

CLINICAL RELEVANCE

The identification of unique salivary proteome profiles in male and female dogs, coupled with substantial homology to human proteins, provides promising biomarkers for health assessment, highlighting its clinical significance for diagnostics and therapeutic exploration not only in veterinary and human dentistry, but across mammalian species.

Ethical Concerns about Fashionable Dog Breeding

The historical relationship between humans and dogs has involved selective breeding for various purposes, such as hunting, guarding, and service roles. However, over time, there has been a shift in preferences from functionality to aesthetics, which has influenced the diverse sizes, shapes, and coats of dog breeds. This review looks at fashionable dog breeding and questions the ethics of prioritising looks over health and behaviour. It aims to alert potential owners, breeders, and regulators to the importance of considering a dog's overall well-being, not just its appearance, which has resulted in fad breeding, leading to genetic disorders, health issues, and a loss of biodiversity. Ethical concerns arise from breeding brachycephalic breeds with respiratory conditions, inbreeding causing inherited disorders, and overbreeding popular breeds while shelter dogs remain unadopted. Additionally, the impact of cosmetic surgeries on popular dog breeds, as well as the neglect of behavioural traits in favour of physical characteristics and strict breeding practices are also considered. The current breeding model can have a negative impact on the emotional and cognitive well-being of dogs, resulting in issues such as aggression, anxiety, and other behavioural problems that can significantly reduce their overall quality of life. Unregulated breeding practices and the demand for rare breeds can lead to illegal breeding, compromising animal welfare. Prospective owners, veterinarians, kennel clubs, and legislators all need to play a responsible role in protecting animals.

Multiple Origins and Genomic Basis of Complex Traits in Sighthounds

Sighthounds, a distinctive group of hounds comprising numerous breeds, have their origins rooted in ancient artificial selection of dogs. In this study, we performed genome sequencing for 123 sighthounds, including one breed from Africa, six breeds from Europe, two breeds from Russia, and four breeds and 12 village dogs from the Middle East. We gathered public genome data of five sighthounds and 98 other dogs as well as 31 gray wolves to pinpoint the origin and genes influencing the morphology of the sighthound genome. Population genomic analysis suggested that sighthounds originated from native dogs independently and were comprehensively admixed among breeds, supporting the multiple origins hypothesis of sighthounds. An additional 67 published ancient wolf genomes were added for gene flow detection. Results showed dramatic admixture of ancient wolves in African sighthounds, even more than with modern wolves. Whole-genome scan analysis identified 17 positively selected genes (PSGs) in the African population, 27 PSGs in the European population, and 54 PSGs in the Middle Eastern population. None of the PSGs overlapped in the three populations. Pooled PSGs of the three populations were significantly enriched in "regulation of release of sequestered calcium ion into cytosol" (gene ontology: 0051279), which is related to blood circulation and heart contraction. In addition, ESR1, JAK2, ADRB1, PRKCE, and CAMK2D were under positive selection in all three selected groups. This suggests that different PSGs in the same pathway contributed to the similar phenotype of sighthounds. We identified an ESR1 mutation (chr1: g.42,177,149 T > C) in the transcription factor (TF) binding site of Stat5a and a JAK2 mutation (chr1: g.93,277,007 T > A) in the TF binding site of Sox5. Functional experiments confirmed that the ESR1 and JAK2 mutation reduced their expression. Our results provide new insights into the domestication history and genomic basis of sighthounds.

Dog breeds and conformations in the UK in 2019: VetCompass canine demography and some consequent welfare implications

INTRODUCTION

Growing concerns over health and welfare impacts from extreme phenotypes in dogs have created an urgent need for reliable demographic information on the national breed structures of dogs.

METHODS

This study included all dogs under primary veterinary care in the UK during 2019 at practices participating in VetCompass. Demographic data on these dogs were analysed to report on the frequency of common breeds and also to report on conformation, bodyweight, sex and neuter associations with these breeds.

RESULTS

The study included 2,237,105 dogs under UK veterinary care in 2019. Overall, 69.4% (n = 1,551,462) were classified as purebred, 6.7% (149,308) as designer-crossbred and 24.0% (536,335) as nondesigner-crossbred. Across 800 unique breed names, the most frequent breeds at any age were nondesigner-crossbred (n = 536,335, 24.0%), Labrador Retriever (154,222, 6.9%) and Jack Russell Terrier (101,294, 4.5%). Among 229,624 (10.3%) dogs aged under one year, the most frequent breeds were nondesigner-crossbred (n = 45,995, 20.0%), French Bulldog (16,036, 7.0%) and Cockapoo (14,321, 6.2%). Overall, based on breed characteristics, 17.6% (395,739) were classified as brachycephalic, 43.1% (969,403) as mesaticephalic and 8.3% (186,320) as dolichocephalic. Of 1,551,336 dogs that were classifiable based on breed, 52.6% (815,673) were chondrodystrophic. Of 1,462,925 dogs that were classifiable, there were 54.6% (n = 798,426) short haired, 32.6% (476,883) medium haired and 12.8% (186,934) long haired. Of 1,547,653 dogs that were classifiable for ear carriage, 24.5% (n = 379,581) were erect, 28.1% (434,273) were semi-erect, 19.7% (305,475) were v-shaped drop and 27.7% (428,324) were pendulous. Overall, there was a 1.09:1.00 ratio of male (n = 1,163,512; 52.2%) to female dogs (n = 1,067,552; 47.8%).

CONCLUSIONS

Health and welfare issues linked to popular breeds with extreme phenotypes suggest that there is much work to do to help owners to make more welfare-friendly decisions when choosing which type of dog to own.

Endotheliochorial placental glycosylation reflects evolutionary divergence between Felidae species (Felis catus and Panthera leo) and Canidae (Canisfamiliaris)

Endotheliochorial cat (Felis catus) and lion (Panthera leo) term placentae and one 6 week placenta (term 60-63 days) from a dog (Canis familiaris) were stained with a panel of 24 lectins to compare glycosylation at the feto-maternal interface. Glycan expression in lion and cat placentae was very similar apart from the occurrence of terminal α-galactose in the lion trophoblast. The dog differed in several respects, particularly in the trophoblast, consistent with species-specific glycotypes differing according to the degree of their evolutionary divergence. The data suggest that evolutionary effects on the glycotype are most readily observed in trophoblast.

Mutations, sex, and genetic diversity: New arguments for partially directed evolution

A review of the theories of the existence of sexes, genetic diversity, and the distribution of mutations among organisms shows that all these concepts are not a product of random evolution and cannot be explained within the framework of Darwinism. Most mutations are the result of the genome acting on itself. This is an organized process that is implemented very differently in different species, in different places in the genome. Because of the fact that it is not random, this process must be directed and regulated, albeit with complex and not fully understood laws. This means that an additional reason must be included in order to model such mutations during evolution. The assumption of directionality must not only be explicitly included in evolutionary theory but must also occupy a central place in it. In this study an updated model of partially directed evolution is constructed, which is capable of qualitatively explaining the indicated features of evolution. Experiments are described that can confirm or disprove the proposed model.

Activity patterns are associated with fractional lifespan, memory, and gait speed in aged dogs

Maintaining an active lifestyle is considered a hallmark of successful aging. Physical activity significantly reduces the risk of cognitive decline and Alzheimer's disease in humans. However, pain and lack of motivation are important barriers to exercise. Dogs are a remarkable model for translational studies in aging and cognition as they are prone to Canine Cognitive Dysfunction syndrome, which has many similarities with Alzheimer's disease. According to owner reports, changes in activity levels are characteristic of this syndrome, with decreased daytime activity, but also excessive pacing, especially at sleep time. We used physical activity monitors to record the activity of 27 senior dogs and evaluated the association between activity level and age, fractional lifespan, cognitive status measured by an owner questionnaire and cognitive tests. We also assessed the relationship between activity and joint/spinal pain, and the off/on leash gait speed ratio (a potential marker of gait speed reserve and motivation). We found that activity patterns in dogs are associated with fractional lifespan and working memory. Additionally, dogs with higher on/off leash gait speed are more active in the afternoon of weekdays. These results encourage future studies evaluating how physical activity can improve or delay cognitive impairment in senior dogs.

Zoonotic parasites associated with predation by dogs and cats

One of the most common behaviors of cats that have an indoor/outdoor lifestyle is to bring hunted "gifts" to their owners, represented by small mammals, reptiles and birds. Access to the outdoors by dogs and cats may represent a problematic issue, since they may be at risk of diseases, traffic accidents and ingestion of toxins. Yet, the impact of this population of roaming dogs and cats predating wildlife is another concerning issue that receives less attention. Despite these risks, most owners still prefer to give outdoor access to their pets to allow them to express their "natural instincts," such as hunting. Therefore, with a growing population of > 470 million dogs and 373 million cats worldwide, predation not only represents a threat to wildlife, but also a door of transmission for parasitic diseases, some of them of zoonotic concern. In this review, the role played by dogs, and especially cats, in the perpetuation of the biological life cycle of zoonotic parasites through the predation of rodents, reptiles and birds is discussed. Feral and domestics dogs and cats have contributed to the population collapse or extinction of > 63 species of reptiles, mammals and birds. Although the ecological impact of predation on wild populations is well documented, the zoonotic risk of transmission of parasitic diseases has not received significant attention. The parasitic diseases associated to predation vary from protozoan agents, such as toxoplasmosis, to cestodes like sparganosis and even nematodes such as toxocariasis. Raising awareness about predation as a risk of zoonotic parasitic infections in dogs and cats will aid to create responsible ownership and proper actions for controlling feral and free-roaming cat and dog populations worldwide.

An update on animal models of intervertebral disc degeneration and low back pain: Exploring the potential of artificial intelligence to improve research analysis and development of prospective therapeutics

Animal models have been invaluable in the identification of molecular events occurring in and contributing to intervertebral disc (IVD) degeneration and important therapeutic targets have been identified. Some outstanding animal models (murine, ovine, chondrodystrophoid canine) have been identified with their own strengths and weaknesses. The llama/alpaca, horse and kangaroo have emerged as new large species for IVD studies, and only time will tell if they will surpass the utility of existing models. The complexity of IVD degeneration poses difficulties in the selection of the most appropriate molecular target of many potential candidates, to focus on in the formulation of strategies to effect disc repair and regeneration. It may well be that many therapeutic objectives should be targeted simultaneously to effect a favorable outcome in human IVD degeneration. Use of animal models in isolation will not allow resolution of this complex issue and a paradigm shift and adoption of new methodologies is required to provide the next step forward in the determination of an effective repairative strategy for the IVD. AI has improved the accuracy and assessment of spinal imaging supporting clinical diagnostics and research efforts to better understand IVD degeneration and its treatment. Implementation of AI in the evaluation of histology data has improved the usefulness of a popular murine IVD model and could also be used in an ovine histopathological grading scheme that has been used to quantify degenerative IVD changes and stem cell mediated regeneration. These models are also attractive candidates for the evaluation of novel anti-oxidant compounds that counter inflammatory conditions in degenerate IVDs and promote IVD regeneration. Some of these compounds also have pain-relieving properties. AI has facilitated development of facial recognition pain assessment in animal IVD models offering the possibility of correlating the potential pain alleviating properties of some of these compounds with IVD regeneration.

Natural and human-driven selection of a single non-coding body size variant in ancient and modern canids

Domestic dogs (Canis lupus familiaris) are the most variable-sized mammalian species on Earth, displaying a 40-fold size difference between breeds.¹ Although dogs of variable size are found in the archeological record,^2-4 the most dramatic shifts in body size are the result of selection over the last two centuries, as dog breeders selected and propagated phenotypic extremes within closed breeding populations.⁵ Analyses of over 200 domestic breeds have identified approximately 20 body size genes regulating insulin processing, fatty acid metabolism, TGFβ signaling, and skeletal formation.^6-10 Of these, insulin-like growth factor 1 (IGF1) predominates, controlling approximately 15% of body size variation between breeds.⁸ The identification of a functional mutation associated with IGF1 has thus far proven elusive.^6,10,11 Here, to identify and elucidate the role of an ancestral IGF1 allele in the propagation of modern canids, we analyzed 1,431 genome sequences from 13 species, including both ancient and modern canids, thus allowing us to define the evolutionary history of both ancestral and derived alleles at this locus. We identified a single variant in an antisense long non-coding RNA (IGF1-AS) that interacts with the IGF1 gene, creating a duplex. While the derived mutation predominates in both modern gray wolves and large domestic breeds, the ancestral allele, which predisposes to small size, was common in small-sized breeds and smaller wild canids. Our analyses demonstrate that this major regulator of canid body size nearly vanished in Pleistocene wolves, before its recent resurgence resulting from human-imposed selection for small-sized breed dogs.

Genetic variations and dog breed identification using inter-simple sequence repeat markers coupled with high resolution melting analysis

The identification of differing physical characteristics of dogs is an uncomplicated and straightforward way to categorize dog breeds. However, many dog owners and veterinarians still struggle to distinguish between pure breed and mixed variations in certain breeds of dogs. Presently, the absence of the tools and methods needed to confirm a pure breed dog is a significant problem since the only method available to validate pure or mongrel breeds is the official pedigree system. Inter-simple sequence repeat markers have been successfully used to assess genetic variations and differentiations. Notably, inter-simple sequence repeat markers coupled with high resolution melting analysis were effectively used for the breed identification of 43 breeds of dogs (total 463 dogs). The 10 primers chosen for analysis resulted in a range of 31-78.6% of breed discrimination when using one primer, while a combination of two primers was able to successfully discriminate between all of the 43 dog breeds (100%). Shannon's index information (I = 2.586 ± 0.034) and expected heterozygosity (H e  = 0.908 ± 0.003) indicated a high level of genetic diversity among breeds. The fixation index (F st ) revealed a value of 10.4%, demonstrating that there was a high level of genetic subdivision between populations. This study showed that inter-simple sequence repeat marker analysis was effective in demonstrating high genetic diversity among varying breeds of dogs, while a combination of Inter-simple sequence repeat marker analysis and high resolution melting analysis could provide an optional technique for researchers to effectively identify breeds through genetic variations.

Body size, inbreeding, and lifespan in domestic dogs

Inbreeding poses a real or potential threat to nearly every species of conservation concern. Inbreeding leads to loss of diversity at the individual level, which can cause inbreeding depression, and at the population level, which can hinder ability to respond to a changing environment. In closed populations such as endangered species and ex situ breeding programs, some degree of inbreeding is inevitable. It is therefore vital to understand how different patterns of breeding and inbreeding can affect fitness in real animals. Domestic dogs provide an excellent model, showing dramatic variation in degree of inbreeding and in lifespan, an important aspect of fitness that is known to be impacted by inbreeding in other species. There is a strong negative correlation between body size and lifespan in dogs, but it is unknown whether the higher rate of aging in large dogs is due to body size per se or some other factor associated with large size. We used dense genome-wide SNP array data to calculate average inbreeding for over 100 dog breeds based on autozygous segment length and found that large breeds tend to have higher coefficients of inbreeding than small breeds. We then used data from the Veterinary medical Database and other published sources to estimate life expectancies for pure and mixed breed dogs. When controlling for size, variation in inbreeding was not associated with life expectancy across breeds. When comparing mixed versus purebred dogs, however, mixed breed dogs lived about 1.2 years longer on average than size-matched purebred dogs. Furthermore, individual pedigree coefficients of inbreeding and lifespans for over 9000 golden retrievers showed that inbreeding does negatively impact lifespan at the individual level. Registration data from the American Kennel Club suggest that the molecular inbreeding patterns observed in purebred dogs result from specific breeding practices and/or founder effects and not the current population size. Our results suggest that recent inbreeding, as reflected in variation within a breed, is more likely to affect fitness than historic inbreeding, as reflected in variation among breeds. Our results also indicate that occasional outcrosses, as in mixed breed dogs, can have a substantial positive effect on fitness.

Highly heritable and functionally relevant breed differences in dog behaviour

Variation across dog breeds presents a unique opportunity to investigate the evolution and biological basis of complex behavioural traits. We integrated behavioural data from more than 14 000 dogs from 101 breeds with breed-averaged genotypic data (n = 5697 dogs) from over 100 000 loci in the dog genome. We found high levels of among-breed heritability for 14 behavioural traits (the proportion of trait variance attributable to genetic similarity among breeds). We next identified 131 single nucleotide polymorphisms associated with breed differences in behaviour, which were found in genes that are highly expressed in the brain and enriched for neurobiological functions and developmental processes, suggesting that they may be functionally associated with behavioural differences. Our results shed light on the heritability and genetic architecture of complex behavioural traits and identify dogs as a powerful model in which to address these questions.

Dog10K: an international sequencing effort to advance studies of canine domestication, phenotypes and health

Dogs are the most phenotypically diverse mammalian species, and they possess more known heritable disorders than any other non-human mammal. Efforts to catalog and characterize genetic variation across well-chosen populations of canines are necessary to advance our understanding of their evolutionary history and genetic architecture. To date, no organized effort has been undertaken to sequence the world's canid populations. The Dog10K Consortium (http://www.dog10kgenomes.org) is an international collaboration of researchers from across the globe who will generate 20× whole genomes from 10 000 canids in 5 years. This effort will capture the genetic diversity that underlies the phenotypic and geographical variability of modern canids worldwide. Breeds, village dogs, niche populations and extended pedigrees are currently being sequenced, and de novo assemblies of multiple canids are being constructed. This unprecedented dataset will address the genetic underpinnings of domestication, breed formation, aging, behavior and morphological variation. More generally, this effort will advance our understanding of human and canine health.

The Australian dingo: untamed or feral?

BACKGROUND

The Australian dingo continues to cause debate amongst Aboriginal people, pastoralists, scientists and the government in Australia. A lingering controversy is whether the dingo has been tamed and has now reverted to its ancestral wild state or whether its ancestors were domesticated and it now resides on the continent as a feral dog. The goal of this article is to place the discussion onto a theoretical framework, highlight what is currently known about dingo origins and taxonomy and then make a series of experimentally testable organismal, cellular and biochemical predictions that we propose can focus future research.

DISCUSSION

We consider a canid that has been unconsciously selected as a tamed animal and the endpoint of methodical or what we now call artificial selection as a domesticated animal. We consider wild animals that were formerly tamed as untamed and those wild animals that were formerly domesticated as feralized. Untamed canids are predicted to be marked by a signature of unconscious selection whereas feral animals are hypothesized to be marked by signatures of both unconscious and artificial selection. First, we review the movement of dingo ancestors into Australia. We then discuss how differences between taming and domestication may influence the organismal traits of skull morphometrics, brain and size, seasonal breeding, and sociability. Finally, we consider cellular and molecular level traits including hypotheses concerning the phylogenetic position of dingoes, metabolic genes that appear to be under positive selection and the potential for micronutrient compensation by the gut microbiome.

CONCLUSIONS

Western Australian Government policy is currently being revised to allow the widespread killing of the Australian dingo. These policies are based on an incomplete understanding of the evolutionary history of the canid and assume the dingo is feralized. However, accumulated evidence does not definitively show that the dingo was ever domesticated and additional focused research is required. We suggest that incorporating ancient DNA data into the debate concerning dingo origins will be pivotal to understanding the evolutionary history of the canid. Further, we advocate that future morphological, behavioural and genetic studies should focus on including genetically pure Alpine and Desert dingoes and not dingo-dog hybrids. Finally, we propose that future studies critically examine genes under selection in the dingo and employ the genome from a wild canid for comparison.

Interspecific Gene Flow Shaped the Evolution of the Genus Canis

The evolutionary history of the wolf-like canids of the genus Canis has been heavily debated, especially regarding the number of distinct species and their relationships at the population and species level [1-6]. We assembled a dataset of 48 resequenced genomes spanning all members of the genus Canis except the black-backed and side-striped jackals, encompassing the global diversity of seven extant canid lineages. This includes eight new genomes, including the first resequenced Ethiopian wolf (Canis simensis), one dhole (Cuon alpinus), two East African hunting dogs (Lycaon pictus), two Eurasian golden jackals (Canis aureus), and two Middle Eastern gray wolves (Canis lupus). The relationships between the Ethiopian wolf, African golden wolf, and golden jackal were resolved. We highlight the role of interspecific hybridization in the evolution of this charismatic group. Specifically, we find gene flow between the ancestors of the dhole and African hunting dog and admixture between the gray wolf, coyote (Canis latrans), golden jackal, and African golden wolf. Additionally, we report gene flow from gray and Ethiopian wolves to the African golden wolf, suggesting that the African golden wolf originated through hybridization between these species. Finally, we hypothesize that coyotes and gray wolves carry genetic material derived from a "ghost" basal canid lineage.

Genomic Analyses Reveal the Influence of Geographic Origin, Migration, and Hybridization on Modern Dog Breed Development

There are nearly 400 modern domestic dog breeds with a unique histories and genetic profiles. To track the genetic signatures of breed development, we have assembled the most diverse dataset of dog breeds, reflecting their extensive phenotypic variation and heritage. Combining genetic distance, migration, and genome-wide haplotype sharing analyses, we uncover geographic patterns of development and independent origins of common traits. Our analyses reveal the hybrid history of breeds and elucidate the effects of immigration, revealing for the first time a suggestion of New World dog within some modern breeds. Finally, we used cladistics and haplotype sharing to show that some common traits have arisen more than once in the history of the dog. These analyses characterize the complexities of breed development, resolving longstanding questions regarding individual breed origination, the effect of migration on geographically distinct breeds, and, by inference, transfer of trait and disease alleles among dog breeds.

The oldest case yet reported of osteoarthritis in a dog: an archaeological and radiological evaluation

A century ago the remains of a dog skeleton were found in an archaeological double human burial, near Bonn-Oberkassel (Germany). Recent re-examination of the dog remains revealed that they were about 14,500 years old. Based on the growth plates, the animal was considered to be approximately 7·5 months old at the time of death. Based on the minimal humeral diameter, it was calculated that it was approximately 0·47 m tall at the shoulder and weighed approximately 15·7 kg. The right proximal ulna of this skeleton showed osteoarthritis, manifested by an osteophyte of 5×3×1·5 mm³ at its cranial edge, with no identified primary developmental causes for osteoarthritis. Osteochondritis dissecans, joint incongruity and trauma are possible aetiologies. The left ulna did not reveal any abnormalities.

The morphology of the mandibular coronoid process does not indicate that Canis lupus chanco is the progenitor to dogs

The domestication of wolves is currently under debate. Where, when and from which wolf sub-species dogs originated are being investigated both by osteoarchaeologists and geneticists. While DNA research is rapidly becoming more active and popular, morphological methods have been the gold standard in the past. But even today morphological details are routinely employed to discern archaeological wolves from dogs. One such morphological similarity between Canis lupus chanco and dogs was published in 1977 by Olsen and Olsen. This concerns the “turned back” anatomy of the dorsal part of the vertical ramus of the mandible that was claimed to be specific to domestic dogs and Chinese wolves C. lupus chanco, and “absent from other canids”. Based on this characteristic, C. lupus chanco was said to be the progenitor of Asian and American dogs, and this specific morphology has been continuously used as an argument to assign archaeological specimens, including non-Asian and non-American, to the dog clade. We challenged this statement by examining 384 dog skulls of 72 breeds and 60 skulls of four wolf sub-species. Only 20 % of dog mandibles and 80 % of C. lupus chanco showed the specific anatomy. In addition, 12 % of Canis lupus pallipes mandibles showed the “turned back” morphology. It can be concluded that the shape of the coronoid process of the mandible cannot be used as a morphological trait to determine whether a specimen belongs to a dog or as an argument in favour of chanco as the progenitor to dogs.

Why is the dog an ideal model for aging research?

With many caveats to the traditional vertebrate species pertaining to biogerontology investigations, it has been suggested that a most informative model is the one which: 1) examines closely related species, or various members of the same species with naturally occurring lifespan variation, 2) already has adequate medical procedures developed, 3) has a well annotated genome, 4) does not require artificial housing, and can live in its natural environment while being investigated, and 5) allows considerable information to be gathered within a relatively short period of time. The domestic dog unsurprisingly fits each criterion mentioned. The dog has already become a key model system in which to evaluate surgical techniques and novel medications because of the remarkable similarity between human and canine conditions, treatments, and response to therapy. The dog naturally serves as a disease model for study, obviating the need to construct artificial genetically modified examples of disease. Just as the dog offers a natural model for human conditions and diseases, simple observation leads to the conclusion that the canine aging phenotype also mimics that of the human. Genotype information, biochemical information pertaining to the GH/IGF-1 pathway, and some limited longitudinal investigations have begun the establishment of the domestic dog as a model of aging. Although we find that dogs indeed are a model to study aging and there are many independent pieces of canine aging data, there are many more "open" areas, ripe for investigation.

Whole Genome Association Study to Detect Single Nucleotide Polymorphisms for Behavior in Sapsaree Dog (Canis familiaris)

The purpose of this study was to characterize genetic architecture of behavior patterns in Sapsaree dogs. The breed population (n = 8,256) has been constructed since 1990 over 12 generations and managed at the Sapsaree Breeding Research Institute, Gyeongsan, Korea. Seven behavioral traits were investigated for 882 individuals. The traits were classified as a quantitative or a categorical group, and heritabilities (h(2)) and variance components were estimated under the Animal model using ASREML 2.0 software program. In general, the h(2) estimates of the traits ranged between 0.00 and 0.16. Strong genetic (r G ) and phenotypic (r P ) correlations were observed between nerve stability, affability and adaptability, i.e. 0.9 to 0.94 and 0.46 to 0.68, respectively. To detect significant single nucleotide polymorphism (SNP) for the behavioral traits, a total of 134 and 60 samples were genotyped using the Illumina 22K CanineSNP20 and 170K CanineHD bead chips, respectively. Two datasets comprising 60 (Sap60) and 183 (Sap183) samples were analyzed, respectively, of which the latter was based on the SNPs that were embedded on both the 22K and 170K chips. To perform genome-wide association analysis, each SNP was considered with the residuals of each phenotype that were adjusted for sex and year of birth as fixed effects. A least squares based single marker regression analysis was followed by a stepwise regression procedure for the significant SNPs (p<0.01), to determine a best set of SNPs for each trait. A total of 41 SNPs were detected with the Sap183 samples for the behavior traits. The significant SNPs need to be verified using other samples, so as to be utilized to improve behavior traits via marker-assisted selection in the Sapsaree population.

Down but not out: supine postures as facilitators of play in domestic dogs

We used two sets of videotaped data of playing domestic dog dyads to determine whether rolling over during play served as a signal of submission or whether it was a combat maneuver adopted as part of an ongoing play sequence. Our results provide strong support for the latter. In the absence of any overt indication of agonism, the frequency with which rollovers occurred was determined primarily by play bout length. The discrepancy in partner size had no effect on the probability that rollovers would occur and there was no evidence that smaller dogs were more likely to rollover or to sustain a supine posture for longer, if they did. The supine phase of rollovers was significantly skewed to short durations. Most rollovers were either defensive (evading a nape bite) or offensive (launching an attack). None could be categorized as submissive. We conclude that asymmetries in the performance of rollovers cannot be assumed to point to asymmetries in the relationships between play partners. This article is part of a Special Issue entitled: Canine Behavior.

Insights into morphology and disease from the dog genome project

Although most modern dog breeds are less than 200 years old, the symbiosis between man and dog is ancient. Since prehistoric times, repeated selection events have transformed the wolf into man's guardians, laborers, athletes, and companions. The rapid transformation from pack predator to loyal companion is a feat that is arguably unique among domesticated animals. How this transformation came to pass remained a biological mystery until recently: Within the past decade, the deployment of genomic approaches to study population structure, detect signatures of selection, and identify genetic variants that underlie canine phenotypes is ushering into focus novel biological mechanisms that make dogs remarkable. Ironically, the very practices responsible for breed formation also spurned morbidity; today, many diseases are correlated with breed identity. In this review, we discuss man's best friend in the context of a genetic model to understand paradigms of heritable phenotypes, both desirable and disadvantageous.

The complete mitochondrial genome of Belgium Malinois (Canis; Canidae)

In this study, the complete nucleotide sequence of Belgium Malinois mitochondrial genome was determined for the first time. Sequence analysis showed that the genome structure was in accordance with other dogs. It contained 22 tRNA genes, 2 ribosomal RNA genes, 13 protein-coding genes and 1 control region (D-loop region). The base composition was A (31.7%), G (14.1%), C (25.5%) and T (28.7%), so the percentage of A and T (60.4%) was higher than that of G and C. The complete mitochondrial genome sequence of the Belgium Malinois will shed a new light on further dog breeds study.

Prevalence of inherited disorders among mixed-breed and purebred dogs: 27,254 cases (1995-2010)

OBJECTIVE

To determine the proportion of mixed-breed and purebred dogs with common genetic disorders.

DESIGN

Case-control study.

ANIMALS

27,254 dogs with an inherited disorder.

PROCEDURES

Electronic medical records were reviewed for 24 genetic disorders: hemangiosarcoma, lymphoma, mast cell tumor, osteosarcoma, aortic stenosis, dilated cardiomyopathy, hypertrophic cardiomyopathy, mitral valve dysplasia, patent ductus arteriosus, ventricular septal defect, hyperadrenocorticism, hypoadrenocorticism, hypothyroidism, elbow dysplasia, hip dysplasia, intervertebral disk disease, patellar luxation, ruptured cranial cruciate ligament, atopy or allergic dermatitis, bloat, cataracts, epilepsy, lens luxation, and portosystemic shunt. For each disorder, healthy controls matched for age, body weight, and sex to each affected dog were identified.

RESULTS

Genetic disorders differed in expression. No differences in expression of 13 genetic disorders were detected between purebred dogs and mixed-breed dogs (ie, hip dysplasia, hypo- and hyperadrenocorticism, cancers, lens luxation, and patellar luxation). Purebred dogs were more likely to have 10 genetic disorders, including dilated cardiomyopathy, elbow dysplasia, cataracts, and hypothyroidism. Mixed-breed dogs had a greater probability of ruptured cranial cruciate ligament.

CONCLUSIONS AND CLINICAL RELEVANCE

Prevalence of genetic disorders in both populations was related to the specific disorder. Recently derived breeds or those from similar lineages appeared to be more susceptible to certain disorders that affect all closely related purebred dogs, whereas disorders with equal prevalence in the 2 populations suggested that those disorders represented more ancient mutations that are widely spread through the dog population. Results provided insight on how breeding practices may reduce prevalence of a disorder.

A candidate gene analysis of canine hypoadrenocorticism in 3 dog breeds

Canine hypoadrenocorticism is believed to be an immune-related condition. It is rare in the overall dog population but shows a breed-related predisposition with Standard poodles and Portuguese water dogs having a greater prevalence of the condition. It shares many similarities with human primary adrenal insufficiency and is believed to be a naturally occurring, spontaneous model for the human condition. Short haplotype blocks and low levels of linkage disequilibrium in the human genome mean that the identification of genetic contributors to the condition requires large sample numbers. Pedigree dogs have high linkage disequilibrium and long haplotypes within a breed, increasing the potential of identifying novel genes that contribute to canine genetic disease. We investigated 222 SNPs from 42 genes that have been associated or may be implicated in human Addison's disease. We conducted case-control analyses in 3 pedigree dog breeds (Labrador retriever: affected n = 30, unaffected = 76; Cocker Spaniel: affected n = 19, unaffected = 53; Springer spaniel: affected n = 26, unaffected = 46) and identified 8 associated alleles in genes COL4A4, OSBPL9, CTLA4, PTPN22, and STXBP5 in 3 pedigree breeds. Association with immune response genes PTPN22 and CTLA4 in certain breeds suggests an underlying immunopathogenesis of the disease. These results suggest that canine hypoadrenocorticism could be a useful model for studying comparative genetics relevant to human Addison's disease.

Genetic characterization, at the mitochondrial and nuclear DNA levels, of five Canary Island dog breeds

Many studies presenting genetic analysis of dog breeds have been conducted without the inclusion of island dog breeds, although isolation can be one of the main factors in their origin. Here we report the genetic analysis at the nuclear and mitochondrial DNA levels of five Canary Island dog breeds (Canarian Warren Hound, Canary Island Mastiff, Garafiano Shepherd, La Palma Rat-Hunter and El Hierro Wolfhound) to fill this gap and, at the same time, genetically characterize these breeds. We identified 168 alleles in autosomal microsatellites and 16 mitochondrial haplotypes. Observed and expected heterozygosities ranged from 0.556 to 0.783 and from 0.737 to 0.943 respectively. Furthermore, three haplotypes were newly described and exclusive to a particular breed (A17+ in the Canary Island Mastiff; A33+ in the Canarian Warren Hound; Bi in the La Palma Rat-Hunter). The outcome of our analyses also revealed different breed histories consistent with historical documents and hypothetical origin designations. Although mtDNA haplotypes showed poor breed discriminating power, autosomal markers allowed a clear clustering of each single population. We expect that our results, together with further analyses, will help to make the population histories of island dog breeds clearer.

Sequence comparison of prefrontal cortical brain transcriptome from a tame and an aggressive silver fox (Vulpes vulpes)

Background

Two strains of the silver fox (Vulpes vulpes), with markedly different behavioral phenotypes, have been developed by long-term selection for behavior. Foxes from the tame strain exhibit friendly behavior towards humans, paralleling the sociability of canine puppies, whereas foxes from the aggressive strain are defensive and exhibit aggression to humans. To understand the genetic differences underlying these behavioral phenotypes fox-specific genomic resources are needed.

Results

cDNA from mRNA from pre-frontal cortex of a tame and an aggressive fox was sequenced using the Roche 454 FLX Titanium platform (> 2.5 million reads & 0.9 Gbase of tame fox sequence; >3.3 million reads & 1.2 Gbase of aggressive fox sequence). Over 80% of the fox reads were assembled into contigs. Mapping fox reads against the fox transcriptome assembly and the dog genome identified over 30,000 high confidence fox-specific SNPs. Fox transcripts for approximately 14,000 genes were identified using SwissProt and the dog RefSeq databases. An at least 2-fold expression difference between the two samples (p < 0.05) was observed for 335 genes, fewer than 3% of the total number of genes identified in the fox transcriptome.

Conclusions

Transcriptome sequencing significantly expanded genomic resources available for the fox, a species without a sequenced genome. In a very cost efficient manner this yielded a large number of fox-specific SNP markers for genetic studies and provided significant insights into the gene expression profile of the fox pre-frontal cortex; expression differences between the two fox samples; and a catalogue of potentially important gene-specific sequence variants. This result demonstrates the utility of this approach for developing genomic resources in species with limited genomic information.

Inbreeding and genetic diversity in dogs: results from DNA analysis

This review assesses evidence from DNA analysis to determine whether there is sufficient genetic diversity within breeds to ensure that populations are sustainable in the absence of cross breeding and to determine whether genetic diversity is declining. On average, dog breeds currently retain approximately 87% of the available domestic canine genetic diversity. Requirements that breeding stock must be 'clear' for all genetic disorders may firstly place undue genetic pressure on animals tested as being 'clear' of known genetic disorders, secondly may contribute to loss of diversity and thirdly may result in the dissemination of new recessive disorders for which no genetic tests are available. Global exchange of genetic material may hasten the loss of alleles and this practice should be discussed in relation to the current effective population size of a breed and its expected future popularity. Genomic data do not always support the results from pedigree analysis and possible reasons for this are discussed.

Microdamage accumulation changes according to animal mass: an intraspecies investigation

The fatigue life of a structure is also influenced by its size. Statistically, a bone from a large animal is expected to bear a higher risk of stress fracture if compared to the same bone from a small animal of the same species. This is not documented in the dog, where individuals can have a 40 times difference in body mass. We investigated the effect of body size on cortical bone microdamage accumulation, cortical microstructural organization (porosity, osteon area, and osteocyte lacunar density), and turnover in dogs with a wide body mass range. The aim was to understand and mathematically model how the bone tissue copes with the microdamage accumulation linked to body mass increase. Calcified transverse cortical sections of 18 canine radii of remarkably different size were examined by means of a standard bulk-staining technique and histomorphometric standard algorithms. Relationships between the investigated histomorphometric variables age, sex and mass were analyzed by general linear multivariate models and exponential equations. Type and location of microdamage and bone turnover were not influenced by body mass. Gender did not influence any parameter. Age influenced bone turnover and activation frequency. Microcrack density was influenced by bone mass. Bones had a similar microstructural organization within the same species regardless of the subject's dimension. Microdamage accumulation is inversely related to bone mass, whereas bone turnover is mass-invariant. We theorize a mass-related change in the bone fracture toughness targeted to reach an optimal unique dimensionless curve for fatigue life.

Origins of the domestic dog and the rich potential for gene mapping

The unique breeding structure of the domestic dog makes canine genetics a useful tool to further the understanding of inherited diseases and gene function. Answers to the questions of when and where the dog was domesticated from the wolf are uncertain, but how the modern diversity of dog breeds was developed is documented. Breed development has resulted in many genetically isolated populations which are segregating for different alleles for disease and morphological and behavioral traits. Many genetic tools are available for dog research allowing investigation into the genetic basis of these phenotypes. Research into causes of diseases in dogs is relevant to humans and other species; comparative genomics is being used to transfer genetic information to them, including some studies on morphological and behavioral phenotypes. Because of the unique breed structure and well-maintained pedigrees, dogs represent a model organism containing a wealth of genetic information.

Animal evolution during domestication: the domesticated fox as a model

We review the evolution of domestic animals, emphasizing the effect of the earliest steps of domestication on its course. Using the first domesticated species, the dog (Canis familiaris), for illustration, we describe the evolutionary peculiarities during the historical domestication, such as the high level and wide range of diversity. We suggest that the process of earliest domestication via unconscious and later conscious selection of human-defined behavioral traits may accelerate phenotypic variations. The review is based on the results of a long-term experiment designed to reproduce early mammalian domestication in the silver fox (Vulpes vulpes) selected for tameability or amenability to domestication. We describe changes in behavior, morphology and physiology that appeared in the fox during its selection for tameability, which were similar to those observed in the domestic dog. Based on the data of the fox experiment and survey of relevant data, we discuss the developmental, genetic and possible molecular genetic mechanisms underlying these changes. We ascribe the causative role in evolutionary transformation of domestic animals to the selection for behavior and to the neurospecific regulatory genes it affects.

Genetic differentiation in pointing dog breeds inferred from microsatellites and mitochondrial DNA sequence

Recent studies presenting genetic analysis of dog breeds do not focus specifically on genetic relationships among pointing dog breeds, although hunting was among the first traits of interest when dogs were domesticated. This report compares histories with genetic relationships among five modern breeds of pointing dogs (English Setter, English Pointer, Epagneul Breton, Deutsch Drahthaar and German Shorthaired Pointer) collected in Spain using mitochondrial, autosomal and Y-chromosome information. We identified 236 alleles in autosomal microsatellites, four Y-chromosome haplotypes and 18 mitochondrial haplotypes. Average F(ST) values were 11.2, 14.4 and 13.1 for autosomal, Y-chromosome microsatellite markers and mtDNA sequence respectively, reflecting relatively high genetic differentiation among breeds. The high gene diversity observed in the pointing breeds (61.7-68.2) suggests contributions from genetically different individuals, but that these individuals originated from the same ancestors. The modern English Setter, thought to have arisen from the Old Spanish Pointer, was the first breed to cluster independently when using autosomal markers and seems to share a common maternal origin with the English Pointer and German Shorthaired Pointer, either via common domestic breed females in the British Isles or through the Old Spanish Pointer females taken to the British Isles in the 14th and 16th centuries. Analysis of mitochondrial DNA sequence indicates the isolation of the Epagneul Breton, which has been formally documented, and shows Deutsch Drahthaar as the result of crossing the German Shorthaired Pointer with other breeds. Our molecular data are consistent with historical documents.

Assortative mating and fragmentation within dog breeds

Background

There are around 400 internationally recognized dog breeds in the world today, with a remarkable diversity in size, shape, color and behavior. Breeds are considered to be uniform groups with similar physical characteristics, shaped by selection rooted in human preferences. This has led to a large genetic difference between breeds and a large extent of linkage disequilibrium within breeds. These characteristics are important for association mapping of candidate genes for diseases and therefore make dogs ideal models for gene mapping of human disorders. However, genetic uniformity within breeds may not always be the case. We studied patterns of genetic diversity within 164 poodles and compared it to 133 dogs from eight other breeds.

Results

Our analyses revealed strong population structure within poodles, with differences among some poodle groups as pronounced as those among other well-recognized breeds. Pedigree analysis going three generations back in time confirmed that subgroups within poodles result from assortative mating imposed by breed standards as well as breeder preferences. Matings have not taken place at random or within traditionally identified size classes in poodles. Instead, a novel set of five poodle groups was identified, defined by combinations of size and color, which is not officially recognized by the kennel clubs. Patterns of genetic diversity in other breeds suggest that assortative mating leading to fragmentation may be a common feature within many dog breeds.

Conclusion

The genetic structure observed in poodles is the result of local mating patterns, implying that breed fragmentation may be different in different countries. Such pronounced structuring within dog breeds can increase the power of association mapping studies, but also represents a serious problem if ignored.

In dog breeding, individuals are selected on the basis of morphology, behaviour, working or show purposes, as well as geographic population structure. The same processes which have historically created dog breeds are still ongoing, and create further subdivision within current dog breeds.

Molecular characterization of the canine mitochondrial DNA control region for forensic applications

The canine mitochondrial DNA (mtDNA) control region of 133 dogs living in the area around Innsbruck, Austria was sequenced. A total of 40 polymorphic sites were observed in the first hypervariable segment and 15 in the second, which resulted in the differentiation of 40 distinct haplotypes. We observed five nucleotide positions that were highly polymorphic within different haplogroups, and they represent good candidates for mtDNA screening. We found five point heteroplasmic positions; all located in HVS-I and a polythymine region in HVS-II, the latter often being associated with length heteroplasmy. In contrast to human mtDNA, the canine control region contains a hypervariable 10 nucleotide repeat region, which is located between the two hypervariable regions. In our population sample, we observed eight different repeat types, which we characterized by direct sequencing and fragment length analysis. The discrimination power of the canine mtDNA control region was 0.93, not taking the polymorphic repeat region into consideration.

Mitochondrial DNA analysis of the domestic dog: control region variation within and among breeds

The mitochondrial DNA (mtDNA) control regions of 125 domestic dogs (Canis familiaris) encompassing 43 breeds, as well as one coyote and two wolves were sequenced and subsequently examined for sequence variation in an effort to construct a reference dog mtDNA data set for forensic analysis. Forty informative variable sites were identified that described 45 haplotypes, 29 of which were observed only once. Substantial variation was found both within and among breeds in the mtDNA derived from tissue, indicating that analysis of the mtDNA derived from dog hairs could be a valuable, discriminating piece of evidence in forensic investigations. The dog data set single nucleotide polymorphisms (SNPs) ranged from having one to six changes on a phylogenetic tree. On average, there were 1.9 character changes for each variable position on the tree. The most variable sites (with four or more changes each, listed from the most changes to the fewest) observed were 15,639 (L=6), 16,672 (L=5), 15,955 (L=4), 15,627 (L=3), 16,431 (L=3), and 16,439 (L=3). These sites were consistent with other reports on variable positions in the dog mtDNA genome. A total of 26 SNPs were chosen to best identify all major clusters in the domestic dog data set. The descriptive analyses revealed that this data set is similar to other published canine data sets and further demonstrates that this domestic dog data set is a useful resource for forensic applications. This reference data set has been compiled and validated against the published dog genetic literature with an aim to aid forensic investigations that seek to incorporate mtDNA sequences and SNPs from trace evidence such as dog hair.

DLA-DRB1, DQA1, and DQB1 alleles and haplotypes in North American Gray Wolves

The canine major histocompatibility complex contains highly polymorphic genes, many of which are critical in regulating immune response. Since domestic dogs evolved from Gray Wolves (Canis lupus), common DLA class II alleles should exist. Sequencing was used to characterize 175 Gray Wolves for DLA class II alleles, and data from 1856 dogs, covering 85 different breeds of mostly European origin, were available for comparison. Within wolves, 28 new alleles were identified, all occurring in at least 2 individuals. Three DLA-DRB1, 8 DLA-DQA1, and 6 DLA-DQB1 alleles also identified in dogs were present. Twenty-eight haplotypes were identified, of which 2 three-locus haplotypes, and many DLA-DQA1/DQB1 haplotypes, are also found in dogs. The wolves studied had relatively few dog DLA alleles and may therefore represent a remnant population descended from Asian wolves. The single European wolf included carried a haplotype found in both these North American wolves and in many dog breeds. Furthermore, one wolf DQB1 allele has been found in Shih Tzu, a breed of Asian origin. These data suggest that the wolf ancestors of Asian and European dogs may have had different gene pools, currently reflected in the DLA alleles present in dog breeds.

Allometric scaling and biomechanical behavior of the bone tissue: an experimental intraspecific investigation

INTRODUCTION

Adaptation of bone to different loads has received much attention. This paper examines the consequences of differences in size on bones from the same animal species.

METHODS

The study was conducted on 32 canine radii. Their geometry, densitometry and mechanical properties were determined and one-way ANOVA was used to analyze their distribution by sex. Bending failure was observed during the mechanical test. The bones were then likened to thin beams and the mechanical parameters of interest were appraised via beam theory. A multiple linear regression model with stepwise analyses was employed to determine which parameters rule the mechanical characteristics. The relationships between the bone mass and the parameters investigated were analyzed by means of a model II regression in order to state how the scaling of the bone characteristics act on its mechanical behavior.

RESULTS

The linear regression model demonstrated that an animal's mass, its sex and the mineral content and the geometrical properties of its bones almost entirely predict their mechanical behavior. A close fit was found between the experimentally determined and the theoretical slopes of the log regressed allometric equations. The work to failure was found to scale almost linearly with the animal and bone mass and the macroscopical bone material properties were found to be mass invariant. The allometric equations showed that as the animal mass increases, employing proportionally the same amount of tissue, bones get proportionally shorter and proportionally distribute their tissue further from the cross-sectional centroid.

CONCLUSIONS

Our results suggest that dimensional analysis on the assumption of geometrical self-similarity and mechanical testing according to classic elastic solutions are reasonable in bones tested in accordance to our set up. The bone geometry is the parameter able to curb the energy effects of an animal mass increase. The allometric scaling of the bone length and the cross-sectional layout, without an increase in the amount of material proportionally employed, preserves linear with the animal mass the amount of energy necessary to fracture a bone and restrain the rise of stresses and strains in the cross-section.

Selective sweep mapping of genes with large phenotypic effects

Many domestic dog breeds have originated through fixation of discrete mutations by intense artificial selection. As a result of this process, markers in the proximity of genes influencing breed-defining traits will have reduced variation (a selective sweep) and will show divergence in allele frequency. Consequently, low-resolution genomic scans can potentially be used to identify regions containing genes that have a major influence on breed-defining traits. We model the process of breed formation and show that the probability of two or three adjacent marker loci showing a spurious signal of selection within at least one breed (i.e., Type I error or false-positive rate) is low if highly variable and moderately spaced markers are utilized. We also use simulations with selection to demonstrate that even a moderately spaced set of highly polymorphic markers (e.g., one every 0.8 cM) has high power to detect regions targeted by strong artificial selection in dogs. Further, we show that a gene responsible for black coat color in the Large Munsterlander has a 40-Mb region surrounding the gene that is very low in heterozygosity for microsatellite markers. Similarly, we survey 302 microsatellite markers in the Dachshund and find three linked monomorphic microsatellite markers all within a 10-Mb region on chromosome 3. This region contains the FGFR3 gene, which is responsible for achondroplasia in humans, but not in dogs. Consequently, our results suggest that the causative mutation is a gene or regulatory region closely linked to FGFR3.

Identification of microsatellite markers linked to progressive retinal atrophy in American Eskimo Dogs

OBJECTIVE

To identify microsatellite markers linked to progressive retinal atrophy (PRA) in American Eskimo Dogs.

SAMPLE POPULATION

Blood samples or buccal epithelial cells from 66 American Eskimo Dogs, including 53 PRA-unaffected and 13 PRA-affected dogs.

PROCEDURE

The genotypes of unaffected and affected dogs were determined by use of microsatellite markers spanning canine chromosome 9 (CFA09). Homozygosity mapping was used to detect linkage between markers and the gene locus for PRA.

RESULTS

Significant allelic association between marker alleles and the gene locus for PRA was detected for GALK1 and TK1, indicating linkage between these markers and the causative gene locus for PRA.

CONCLUSIONS AND CLINICAL RELEVANCE

These data indicate that PRA in American Eskimo Dogs is located on CFA09 and allow for the development of a microsatellite-based test to identify carrier (unaffected) and affected dogs before clinical signs appear.