Variability of canine microsatellites within and between different dog breeds

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.

Genetic Diversity of Bosnian and Herzegovinian Autochthonous Dog Breed Bosnian Broken-Haired Hound-Barak

Fédération Cynologique Internationale (FCI) classifies a group of hound dogs in the sixth FCI group divided into three sections and three subsections that include 76 dog breeds. With the Istrian wire-haired hound, the Bosnian broken-haired hound-Barak is one of the two internationally recognized and standardized broken-haired hound breeds from the Balkans. However, genotyping of this breed has not been the subject of study so far. A total of 30 dogs (22 males and eight females) from different breeders from 17 locations in Bosnia and Herzegovina were selected for genotyping. All selected individuals had a valid pedigree issued by the Kennel Club in Bosnia and Herzegovina to ensure dogs were unrelated. Hairs with follicles were used for DNA extraction. Ten microsatellite loci from the commercial StockMarks® for Canine Genotyping Kit were amplified. Estimated genetic indices showed that Bosnian broken-haired hound-Barak harbors a high genetic variability. Phylogenetic relationships between Barak and the other 15 dog breeds, including Tornjak, another indigenous breed from Bosnia and Herzegovina, were assessed. An analysis showed clear differentiation of Barak, with Tornjak as the closest one among analyzed breeds. The results suggest that Barak, as we know it today, was developed during the formation of most modern breeds. Although Barak cannot yet be considered an endangered breed thanks to enthusiasts and hunters, the declining population trends impose the urgent need to establish an animal gene bank and programs for in situ conservation to protect and preserve this autochthonous breed of hound dog for future generations.

Evaluation of genetic diversity and management of disease in Border Collie dogs

Maintaining genetic diversity in dog breeds is an important consideration for the management of inherited diseases. We evaluated genetic diversity in Border Collies using molecular and genealogical methods, and examined changes to genetic diversity when carriers for Trapped Neutrophil Syndrome (TNS) and Neuronal Ceroid Lipofuscinosis (NCL) are removed from the genotyped population. Genotype data for 255 Border Collies and a pedigree database of 83,996 Border Collies were used for analysis. Molecular estimates revealed a mean multi-locus heterozygosity (MLH) of 0.311 (SD 0.027), 20.79% of the genome consisted of runs of homozygosity (ROH ) > 1 Mb, effective population size (N_e) was 84.7, and mean inbreeding (F) was 0.052 (SD 0.083). For 227 genotyped Border Collies that had available pedigree information (GenoPed), molecular and pedigree estimates of diversity were compared. A reference population (dogs born between 2005 and 2015, inclusive; N = 13,523; RefPop) and their ancestors (N = 12,478) were used to evaluate the diversity of the population that are contributing to the current generation. The reference population had a N_e of 123.5, a mean F of 0.095 (SD 0.082), 2276 founders (f), 205.5 effective founders (f_e), 28 effective ancestors (f_a) and 10.65 (SD 2.82) founder genomes (N_g). Removing TNS and NCL carriers from the genotyped population had a small impact on diversity measures (ROH > 1 Mb, MLH, heterozygosity), however, there was a loss of > 10% minor allele frequency for 89 SNPs around the TNS mutation (maximum loss of 12.7%), and a loss of > 5% for 5 SNPs around the NCL mutation (maximum 5.18%). A common ancestor was identified for 38 TNS-affected dogs and 64 TNS carriers, and a different common ancestor was identified for 33 NCL-affected dogs and 28 carriers, with some overlap of prominent individuals between both pedigrees. Overall, Border Collies have a high level of genetic diversity compared to other breeds.

Pedigree and Molecular Analyses in the Assessment of Genetic Variability of the Polish Greyhound

Simple Summary

The Polish Greyhound is an old Polish breed. The first descriptions of hunting with greyhounds can be found in the hunting literature of the 16th century, and the first detailed description of a greyhound comes from 1600. The Polish Greyhound probably originates from the Saluki-type Asian greyhounds. The population of this breed is very small and limited mainly to the territory of its country of origin (Poland). Pedigree books were opened for this breed in 1981. The narrow gene pool necessitated mating relatives, resulting in the appearance of various genetic diseases in the breed. The analysis of Polish Greyhound pedigrees registered in the pedigree books from the time of the registration of the breed and molecular tests facilitated calculation of the degree of relatedness in the breed and to design future breeding plans, taking into account that a 2.56% increase in inbreeding per complete generation will be observed if the current breeding program and similar matings are maintained.

Abstract

The aim of the study was to assess the genetic variability of the Polish Greyhound population based on pedigree analysis and molecular DNA testing and to determine the degree of relatedness among individuals in the population. Pedigree data of 912 Polish Greyhounds recorded in pedigree books since they were opened for this breed were analyzed. For molecular testing, DNA was obtained from cheek swabs taken from 235 dogs of the tested breed. A panel of 21 markers (Short Tandem Repeat—STR) was used. The mean inbreeding determined for the Polish Greyhound population based on pedigree analyses was low and amounted to 11.8%, but as many as 872 individuals of the 912 dogs in the studied population were inbred. A total of 83 founders (at least one unknown parent) were identified, among which 27 founders had both unknown parents. Full-sibling groups consisted of 130 individuals, with a minimum and maximum litter size of 2 and 16, respectively. The average litter size was 5.969. Gene diversity calculated based on the mean kinship matrix was 0.862 and the population mean kinship was 0.138. The founder genome equivalent based on the mean kinship matrix was 3.61; the founder genome surviving level was 12.34; the mean Ne was estimated at 21.76; and the Ne/N ratio was 0.135. The FIS inbreeding coefficient for 21 STR was negative, and the mean FIS value for all loci had a low negative value (−0.018). These values suggest a low level of inbreeding in the examined breed as well as the avoidance of mating related animals.

Genomic Characterization of the Istrian Shorthaired Hound

Istrian shorthaired hound is an old indigenous Croatian dog breed with historical traces of its origin, which date back to the 14th century. Due to its intelligence and great hunting abilities, it is considered an excellent hunting dog. Despite its ancient origin, there is no data on genetic diversity, population structure, and degree of inbreeding that could be used for advanced management and conservation of this breed. Our study aimed to provide a high-resolution population structure of the Istrian shorthaired hound using a 220K HD SNP array, to compare the obtained data with the genealogical records and to place the breed in a broader context of world dog populations. Relatively high population size and low inbreeding coefficient estimated from genealogical data indicate a preserved genetic diversity in this breed. The principle component analysis, the NeighborNet network, and TreeMix were used to determine the genetic relationship between the Istrian shorthaired hound and other breeds. The Istrian shorthaired hound was found to be genetically related to Italian hunting dogs sharing the same branch with the Segugio Italiano a Pelo Raso and Segugio Italiano a Pelo Forte. The ADMIXTURE analysis indicated that the Istrian shorthaired hound could be involved in the development of some other hunting dog breeds. The estimated effective population size (Ne) based on SNP data was similar to Ne calculated from genealogical data indicating the absence of bottlenecks and well-balanced use of breeding animals. The low genomic inbreeding coefficient, together with the higher number of short runs of homozygosity, observed in the Istrian shorthaired hound, confirms the ancient origin of the breed based on historical documents. The analysis of selective sweeps identified genomic regions with the strongest selection signals in the vicinity of the genes associated with cognitive performance and behavior. Genome analysis proved to be a useful tool for estimating population parameters and can be implemented in the conservation plan for this indigenous breed.

Polymorphism analyses of 19 STRs in Labrador Retriever population from China and its heterozygosity comparisons with other retriever breeds

Pure breed dogs of Western origin are increasingly more popular in China as is a need to differentiate breeds and individual dogs for personal and forensic reasons. Research on genetic diversities of the canine population in China is rarely conducted. In this study, genetic distributions and forensic efficiencies of 19 canine STR loci in Labrador Retriever population from China were evaluated by using one available commercial canine kit in China. This panel was used to genetically define 214 Labrador Retrievers in China, as an example of one of the most important Western breeds and to compare them with Labrador Retrievers from America based on three overlapping STR loci. Moreover, genetic relationship analyses between Labrador Retriever population and two reference populations in America were performed. All 19 STR loci were polymorphic and conformed to Hardy-Weinberg equilibrium in the studied population. The STR panel was able to discern individual dogs with a high degree of accuracy. Breed-wide genetic heterozygosity comparisons based on present and published allele frequencies revealed that the studied population had the lower genetic heterozygosity than canine populations in America. Principal component analysis among Labrador Retriever population and other reference populations showed that the studied Labrador Retrievers were genetically close to the retriever breeds in America. Population genetic structure analyses among these canine breeds further revealed genetic differentiations between the studied Labrador Retriever population and other compared breeds. In conclusion, these STR loci had relatively high forensic values in Labrador Retriever population in China, which could be employed for individual identification and kinship testing.

Genetic diversity and population structure of African village dogs based on microsatellite and immunity-related molecular markers

The village and street dogs represent a unique model of canine populations. In the absence of selective breeding and veterinary care, they are subject mostly to natural selection. Their analyses contribute to understanding general mechanisms governing the genetic diversity, evolution and adaptation. In this study, we analyzed the genetic diversity and population structure of African village dogs living in villages in three different geographical areas in Northern Kenya. Data obtained for neutral microsatellite molecular markers were compared with those computed for potentially non-neutral markers of candidate immunity-related genes. The neutral genetic diversity was similar to other comparable village dog populations studied so far. The overall genetic diversity in microsatellites was higher than the diversity of European pure breeds, but it was similar to the range of diversity observed in a group composed of many European breeds, indicating that the African population has maintained a large proportion of the genetic diversity of the canine species as a whole. Microsatellite marker diversity indicated that the entire population is subdivided into three genetically distinct, although closely related subpopulations. This genetical partitioning corresponded to their geographical separation and the observed gene flow well correlated with the communication patterns among the three localities. In contrast to neutral microsatellites, the genetic diversity in immunity-related candidate SNP markers was similar across all three subpopulations and to the European group. It seems that the genetic structure of this particular population of Kenyan village dogs is mostly determined by geographical and anthropogenic factors influencing the gene flow between various subpopulations rather than by biological factors, such as genetic contribution of original migrating populations and/or the pathogen-mediated selection. On the other hand, the study of oldest surviving dogs suggested a biological mechanism, i.e. a possible advantage of the overal heterozygosity marked by the the microsatellite loci analyzed.

African Indigenous Cattle: Unique Genetic Resources in a Rapidly Changing World

At least 150 indigenous African cattle breeds have been named, but the majority of African cattle populations remain largely uncharacterized. As cattle breeds and populations in Africa adapted to various local environmental conditions, they acquired unique features. We know now that the history of African cattle was particularly complex and while several of its episodes remain debated, there is no doubt that African cattle population evolved dramatically over time. Today, we find a mosaic of genetically diverse population from the purest Bos taurus to the nearly pure Bos indicus. African cattle are now found all across the continent, with the exception of the Sahara and the river Congo basin. They are found on the rift valley highlands as well as below sea level in the Afar depression. These unique livestock genetic resources are in danger to disappear rapidly following uncontrolled crossbreeding and breed replacements with exotic breeds. Breeding improvement programs of African indigenous livestock remain too few while paradoxically the demand of livestock products is continually increasing. Many African indigenous breeds are endangered now, and their unique adaptive traits may be lost forever. This paper reviews the unique known characteristics of indigenous African cattle populations while describing the opportunities, the necessity and urgency to understand and utilize these resources to respond to the needs of the people of the continent and to the benefit of African farmers.

Genomic analyses of modern dog breeds

A rose may be a rose by any other name, but when you call a dog a poodle it becomes a very different animal than if you call it a bulldog. Both the poodle and the bulldog are examples of dog breeds of which there are >400 recognized worldwide. Breed creation has played a significant role in shaping the modern dog from the length of his leg to the cadence of his bark. The selection and line-breeding required to maintain a breed has also reshaped the genome of the dog, resulting in a unique genetic pattern for each breed. The breed-based population structure combined with extensive morphologic variation and shared human environments have made the dog a popular model for mapping both simple and complex traits and diseases. In order to obtain the most benefit from the dog as a genetic system, it is necessary to understand the effect structured breeding has had on the genome of the species. That is best achieved by looking at genomic analyses of the breeds, their histories, and their relationships to each other.

Reference intervals for Greyhounds and Lurchers using the Sysmex XT-2000iV hematology analyzer

BACKGROUND

The need for breed-specific reference intervals (RIs) for Greyhounds has been identified. As Lurchers are a sighthound cross-breed, specific RIs may also be needed for these dogs. Hematologic RIs for Greyhounds and Lurchers using the Sysmex XT-2000iV hematology analyzer have not been established.

OBJECTIVES

The aims of this study were to establish RIs for Greyhounds using the Sysmex XT-2000iV, to investigate whether RIs for Greyhound and nonsighthound dogs could be transferred to Lurchers, and to establish new RIs for Lurchers if transference was not possible.

METHODS

Data were retrieved retrospectively from a database of blood donor dogs. Greyhound RIs were established using nonparametric methods based on a reference population of 179 dogs. For the RI transference study, 38 Lurchers were selected, following guidelines proposed by the Clinical and Laboratory Standards Institute. When transference was not appropriate, new RIs were generated using the robust method.

RESULTS

Greyhound RIs for the Sysmex hematology analyzer reflected known differences in this breed with a tendency toward higher RBC mass and lower WBC and platelet counts. RIs for hemoglobin concentration, HCT, MCV, MCH, MCHC, and WBC, neutrophil, lymphocyte, monocyte, and platelet counts for Greyhounds were suitable for transference to Lurchers. For RBC and eosinophil counts, new RIs were established.

CONCLUSION

Our study suggests that Lurchers share many hematologic characteristics with Greyhounds, but had higher reference limits for RBC and eosinophil counts.

Microsatellite characterization of Cimarron Uruguayo dogs

Various genetic markers, including microsatellites, have been used to analyze the genetic polymorphism and heterozygosity in canine breeds. In this work, we used nine microsatellite markers to investigate the genetic variability in Cimarron Uruguayo dogs, the only officially recognized native canine breed in Uruguay. DNA from 30 Cimarron Uruguayo dogs from northeastern and southern Uruguay was analyzed. The allelic frequencies for each microsatellite, the genetic variability and the consanguinity were calculated, as were the polymorphic information content (PIC) and the probability of exclusion (PE). All of the microsatellites studied were polymorphic. FH 2361, FH 2305 and PEZ 03 were the most informative, with PIC values > 0.7, in agreement with results for other canine breeds. The PE values for the markers were within the ranges previously described and were generally greater for microsatellites with higher PIC values. The heterozygosity value (0.649) was considered high since only nine microsatellites were analyzed. Compared with data for other breeds, the results obtained here indicate that Cimarron Uruguayo dogs have high genetic diversity.

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.

A Proposal for Standardization in Forensic Canine DNA Typing: Allele Nomenclature of Six Canine-Specific STR Loci

In this study a proposal for the allele nomenclature of six polymorphic short tandem repeat (STR) loci (PEZ3, PEZ6, PEZ8, PEZ10, FHC2161, and FHC2328) for canine genotyping (Canis lupus familiaris) is presented. The nomenclature is based on the sequence data of the polymorphic region of the microsatellite markers as recommended by the DNA commission of the International Society of Forensic Haemogenetics (ISFH) in 1994 for human DNA typing. To cover commonly and rarely occurring alleles, a selection of homozygous and heterozygous animals were analyzed and subjected to sequence studies. The alleles consisted of simple tri- and tetra-nucleotide repeat patterns as well as compound and highly complex repeat patterns. Several alleles revealing the same fragment size but different repeat structures were found. The allele designation described here was adopted to the number of repeats, including all variable regions within the amplified fragment. In a second step the most commonly occurring alleles were added to an allelic ladder for each marker allowing a reliable typing of all alleles differing in size. A total number of 142 unrelated dogs from surrounding municipal animal homes, private households, and canines in police duty were analyzed. The data were added to a population database providing allele frequencies for each marker.

The canine genome

The dog has emerged as a premier species for the study of morphology, behavior, and disease. The recent availability of a high-quality draft sequence lifts the dog system to a new threshold. We provide a primer to use the dog genome by first focusing on its evolutionary history. We overview the relationship of dogs to wild canids and discuss their origin and domestication. Dogs clearly originated from a substantial number of gray wolves and dog breeds define distinct genetic units that can be divided into at least four hierarchical groupings. We review evidence showing that dogs have high levels of linkage disequilibrium. Consequently, given that dog breeds express specific phenotypic traits and vary in behavior and the incidence of genetic disease, genomic-wide scans for linkage disequilibrium may allow the discovery of genes influencing breed-specific characteristics. Finally, we review studies that have utilized the dog to understand the genetic underpinning of several traits, and we summarize genomic resources that can be used to advance such studies. We suggest that given these resources and the unique characteristics of breeds, that the dog is a uniquely valuable resource for studying the genetic basis of complex traits.

The Kintamani Dog: Genetic Profile of an Emerging Breed from Bali, Indonesia

The Kintamani dog is an evolving breed indigenous to the Kintamani region of Bali. Kintamani dogs cohabitate with feral Bali street dogs, although folklore has the breed originating 600 years ago from a Chinese Chow Chow. The physical and personality characteristics of the Kintamani dog make it a popular pet for the Balinese, and efforts are currently under way to have the dog accepted by the Federation Cynologique Internationale as a recognized breed. To study the genetic background of the Kintamani dog, 31 highly polymorphic short tandem repeat markers were analyzed in Kintamani dogs, Bali street dogs, Australian dingoes, and nine American Kennel Club (AKC) recognized breeds of Asian or European origin. The Kintamani dog was identical to the Bali street dog at all but three loci. The Bali street dog and Kintamani dog were most closely aligned with the Australian dingo and distantly related to AKC recognized breeds of Asian but not European origin. Therefore, the Kintamani dog has evolved from Balinese feral dogs with little loss of genetic diversity.

Genetic variability of seven dog breeds based on microsatellite markers

The present study, compared the genetic variability of seven dog breeds and a test sample from Switzerland by means of 26 microsatellite markers. Five loci were excluded from further analyses because one was monomorphic, one not in Hardy-Weinberg equilibrium in all breeds and three in linkage disequilibrium with linked loci. The proportion of shared alleles at the individual level of the remaining 21 microsatellite markers combined with the neighbour-joining method allowed for the clustering of the large majority of the individuals in accordance to their breed. The results were confirmed by analyses using a Bayesian approach for clustering and a Monte Carlo re-sampling method for individual assignment or exclusion to a given population.

Individual assignment using microsatellite DNA reveals unambiguous breed identification in the domestic dog

Modern individual clustering methods utilising hypervariable nuclear microsatellite DNA polymorphisms are being increasingly applied in the field of population genetics. This study explores the efficiency of the clustering methods in identifying the breeds of origin of 250 domestic dog (Canis familiaris) individuals based on 10 microsatellite loci. An allele sharing distance (DAS) matrix and the corresponding neighbour-joining tree of individuals revealed monophyletic assemblages that corresponded perfectly with the breeds of origin of the dogs. Individual assignment tests using a Bayesian statistical approach, an allele frequency based method, and a DCE genetic distance based method were all extremely powerful. Most strikingly, the Bayesian method provided 100% assignment success of individuals into their correct breeds of origin and 100% exclusion success of individuals from all alternate reference populations with a high level of statistical confidence (P < 0.0001). A Bayesian Markov Chain Monte Carlo clustering approach revealed clear distinction of individuals into groups according to their breeds of origin, with a near-zero level of 'genetic admixture' among breeds. The results demonstrate that an FST of 0.18, mean expected gene diversity of 0.6 across 10 loci, and approximately 50 individuals per reference population suffice to provide maximum individual assignment success in C. familiaris. This refutes the traditional view that DNA based dog breed identification is not feasible at the individual level of resolution.

Evaluation of the present breeding programme against copper toxicosis in Danish Bedlington terriers

A breeding programme to eradicate copper toxicosis in Danish Bedlington terriers has been established based on a DNA marker test. Genotyping of both parents is compulsory and after 1 January 2000, only homozygous non-carriers are used for breeding. In this study, two groups of Bedlington terriers were genotyped at 18 microsatellite loci. One group represented the original population of Bedlington terriers before introducing the breeding programme (n = 23); the other represented a group of homozygous non-carriers (n = 24) available for breeding after year 2000. Allele numbers, allele frequencies, observed heterozygosities (Ho), expected heterozygosities (He), locus-specific coefficients of inbreeding (Fl) and Nei's genetic distance (D) was calculated. Individual coefficients of inbreeding (Fi) were calculated from the pedigrees and an assignment test was performed. Four rare alleles were lost in the group of homozygous non-carriers. No significant differences were observed between the mean values of allele numbers, Ho, He, Fl and Fi of the two populations of dogs. Nei's genetic distance between the two populations was 0.06 and 88% of the homozygous non-carriers were assigned correctly in the assignment test. The overall diversity of the breed was low (Ho = 0.41) and the breeders were advised to include the heterozygous carriers again.

Combined use of maternal, paternal and bi-parental genetic markers for the identification of wolf-dog hybrids

The identification of hybrids is often a subject of primary concern for the development of conservation and management strategies, but can be difficult when the hybridizing species are closely related and do not possess diagnostic genetic markers. However, the combined use of mitochondrial DNA (mtDNA), autosomal and Y chromosome genetic markers may allow the identification of hybrids and of the direction of hybridization. We used these three types of markers to genetically characterize one possible wolf-dog hybrid in the endangered Scandinavian wolf population. We first characterized the variability of mtDNA and Y chromosome markers in Scandinavian wolves as well as in neighboring wolf populations and in dogs. While the mtDNA data suggested that the target sample could correspond to a wolf, its Y chromosome type had not been observed before in Scandinavian wolves. We compared the genotype of the target sample at 18 autosomal microsatellite markers with those expected in pure specimens and in hybrids using assignment tests. The combined results led to the conclusion that the animal was a hybrid between a Scandinavian female wolf and a male dog. This finding confirms that inter-specific hybridization between wolves and dogs can occur in natural wolf populations. A possible correlation between hybridization and wolf population density and disturbance deserves further research.

PCR multiplexed microsatellite panels to expedite canine genetic disease linkage analysis

Modern dog breeds possess large numbers of genetic diseases for which there are currently few candidate genes or diagnostic tests. Linkage of a microsatellite marker to a disease phenotype is often the only available tool to aid in the development of screening tests for disease carriers. Detection of linkage to a specific disease phenotype requires screening of large numbers of markers across known affected and unaffected animals. To establish high throughput genome scanning this study placed 100 canine microsatellite markers, arranged by fragment size and fluorescent dye label, into 12 PCR multiplexed panels. The highest degree of multiplexing was 11 markers per panel while the lowest was five markers per panel; each panel was run in one gel lane on automated DNA sequencers. Selection of the markers was based upon chromosomal or linkage group locations, degree of polymorphism, PCR multiplex compatibility and ease of interpretation. The marker set has an average spacing of 22.25 centiMorgan (cM). Marker polymorphism was evaluated across 28 American Kennel Club (AKC) recognized breeds. The utility of buccal swab vs. blood samples was also validated in this study as all template DNA was derived from swabs obtained and submitted by participating dog breeders and owners. The PCR multiplexed microsatellite panels and sampling method described in this report will provide investigators with a cost effective and expedient means of pursuing linkage studies of specific canine genetic diseases.

Suitability of AFLP markers for the study of genetic relationships among Korean native dogs

To determine the genetic relationships among domestic dog breeds, we performed both a sequence comparison of mitochondrial DNA (mtDNA) and an amplified fragment length polymorphisms (AFLP) analysis. Three of four regions of mtDNA, cytochrome b, cytochrome oxidase subunit II, and 16S rRNA genes were highly homogeneous among dog breeds, whereas the other region, the control region, showed relatively high polymorphisms with a maximum percentage difference of 3.18%. However, the control region showed extensive polymorphism even within breeds, and the relationship tree derived from the data could not clearly delimit distinct breeds. 19 EcoRI/MseI primer combinations were used to generate AFLP markers among 25 dogs from 11 breeds including three Korean native dogs. These amplification reactions allowed the detection of more than 1900 amplification products of which 408 were identified as polymorphic bands. Unrooted neighbor-joining tree based on dissimilarity values showed that the Korean native dogs were clustered together with the Asian dogs and that the Asian originated dogs were clustered separately from Western originated dogs. A consensus tree using parsimony method also showed Korean native dogs were grouped separately from the other dogs with moderate bootstrap values. Taken together, it is concluded that AFLP analysis is a more informative tool for revealing genetic relationships among dog breeds than mtDNA sequence comparison.

Microsatellite polymorphism in closely related dogs

The effectiveness of microsatellites in parentage testing and individual identification has been proven in many species, including dogs. However, the use of these markers has not been extended to control for pedigrees in large populations of closely related animals. We have analyzed polymorphism in a set of 10 microsatellites over three generations of 360 pedigree rottweilers. Results were compared with two pure-bred populations of unrelated animals and with one population constituted by unrelated dogs of mixed breeds to measure polymorphism variation. We optimized this set of microsatellites to be analyzed by a semiautomated capillary electrophoresis method after amplification in two multiplex polymerase chain reactions (PCRs). The mean polymorphism information content (PIC) value in the rottweiler pedigree is 0.401 and the combined paternity exclusion probability (CPE) is 95.6%. These values are similar to those obtained in pure-bred populations of unrelated animals, and although polymorphism is reduced in relation to the pool population, we solved all paternity exclusions. In only a few cases did we have to use two additional microsatellites to solve individual identification of full-sib dogs.

Assessment of the population structure of five Finnish dog breeds with microsatellites

Genetic variabilities within and between Finnish populations of Golden Retrievers, German Shepherds, Wirehaired Dachshunds, Pembroke Welsh Corgis and Bedlington Terriers were quantified with microsatellite allele numbers, observed heterozygosities, expected heterozygosities, FIS estimates, FST estimates and DS distances. In a sample of 50 individuals from each, breed and ten polymorphic loci, the highest genetic diversity was exhibited in the Wirehaired Dachshunds and lowest in the Bedlington Terriers. Although statistically significant deviations from the Hardy-Weinberg (H-W) equilibrium were observed, they occurred at an unexpectedly low frequency. Most strikingly, the extremely small Bedlington Terrier population displayed genotypes in H-W proportions in all investigated loci. The H-W deviations always occurred with positive FIS estimates, which, on average, were not larger than values reported for free-living canids. Genetic differentiation between the breeds was very large. As a comparison, present estimates were, on average, over two times higher than previously observed between breeds of sheep, and over two times higher than the highest estimates reported between human populations. Moreover, the highest DS distances were only slightly lower than the lowest values inferred between humans and chimpanzees. Severe bottlenecks in the recent past of the examined breeds were not statistically supported. The presented data imply genetic isolation and intense artificial selection in the history of these breeds of dogs.

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

Comparative analysis of mammalian genomes provides important insight into the structure and function of genes. However, the comparative analysis of gene sequences from individuals of the same and different species also provides insight into the evolution of genes, populations, and species. We exemplify these two uses of genomic information. First, we document the evolutionary relationships of the domestic dog to other carnivores by using a variety of DNA-based information. A phylogenetic comparison of mitochondrial DNA sequences in dogs and gray wolves shows that dogs may have originated from multiple wolf populations at a time much earlier than suggested by the archaeologic record. We discuss previous theories about dog development and evolution in light of the new genetic data. Second, we review recent progress in dog genetic mapping due to the development of hypervariable markers and specific chromosome paints. Extensive genetic homology in gene order and function between humans and dogs has been discovered. The dog promises to be a valuable model for identifying genes that control morphologic differences between mammals as well as understanding genetically based disease.

A second-generation genetic linkage map of the domestic dog, Canis familiaris

Purebred strains, pronounced phenotypic variation, and a high incidence of heritable disease make the domestic dog uniquely suited to complement genetic analyses in humans and mice. A comprehensive genetic linkage map would afford many opportunities in dogs, ranging from the positional cloning of disease genes to the dissection of quantitative differences in size, shape, and behavior. Here we report a canine linkage map with the number of mapped loci expanded to 276 and 10-cM coverage extended to 75-90% of the genome. Most of the 38 canine autosomes are likely represented in the collection of 39 autosomal linkage groups. Eight markers were sufficiently informative to detect linkage at distances of 10-13 cM, yet remained unlinked to any other marker. Taken together, the results suggested a genome size of about 27 M. As in other species, the genetic length varied between sexes, with the female autosomal distance being approximately 1.4-fold greater than that of male meioses. Fifteen markers anchored well-described genes on the map, thereby serving as landmarks for comparative mapping in dogs. We discuss the utility of the current map and outline steps necessary for future map improvement.

A linkage map of the canine genome

A genetic linkage map of the canine genome has been developed by typing 150 microsatellite markers using 17 three-generation pedigrees, composed of 163 F2 individuals. One hundred and thirty-nine markers were linked to at least one other marker with a lod score > or = 3.0, identifying 30 linkage groups. The largest chromosome had 9 markers spanning 106.1 cM. The average distance between markers was 14.03 cM, and the map covers an estimated 2073 cM. Eleven markers were informative on the mapping panel, but were unlinked to any other marker. These likely represent single markers located on small, distinct canine chromosomes. This map will be the initial resource for mapping canine traits of interest and serve as a foundation for development of a comprehensive canine genetic map.