Identification of forensically informative SNPs in the domestic dog mitochondrial control region

Phylogeographic and population genetic structure of hound-like native dogs of the Mediterranean Basin

The dog was probably the first domesticated animal. Despite extensive archaeological and genetic investigations, the origin and the evolution of the extant dogs are still being debated. Dog breeds that have over time been selected for hunting share common ancestral traits. This study represents the first comprehensive attempt to survey at the genomic and mitochondrial level eight hound-like dogs breeds indigenous to the Mediterranean Basin to determine if they share common ancient origins. Results from the microsatellite analysis indicate that all the dog populations have a low inbreeding value.The Kelb tal-Fenek has a high divergence from the current Egyptian street population, however there is not enough evidence from this study to exclude completely the potential of an ancient common relationship. Overall, the mitochondrial results indicate high frequencies of haplogroups A and B and a low representation of haplogroup C, while only one Egyptian dog could be assigned to haplogroup D. Results reveal identities and shared clades, suggesting the conservation of ancient European mitotypes in the Mediterranean hound-like breeds, especially in the Egyptian population. Although none of the dog populations/breeds participating in this study indicate to be direct descendants of the Egyptian dogs, they still have a very close morphologically resemblance to those iconic Egyptian dogs often depicted in ancient art forms and share some genetic links with the current Egyptian population. Further research is required with other markers such us complete mitogenomes and SNP panels to confirm the complex history of the Mediterranean dogs involved in this study.

Analysis of Mitochondrial Genome from Labrador (Canis lupus familiaris) with Mammary Gland Tumour Reveals Novel Mutations and Polymorphisms

The aim of the study was to find associations between the process of neoplastic transformation and mtDNA mutations/polymorphisms, i.e. factors with potential prognostic significance, and to determine their impact on the biochemical properties, as well as structural, and functional properties of proteins. Blood and neoplastic tissue samples were collected from a 9-year-old Labrador dog with a diagnosed malignant mammary tumour. Next-generation genome sequencing (NGS) of the entire mitochondrial genome was performed using Illumina technology, and bioinformatics analyses were carried out. This is the first report demonstrating the application of NGS in the analysis of the canine mtDNA genome in neoplastic disease. The proposed strategy is innovative and promising. For the first time in the literature, the sequence of 29 genes was analysed to determine their association with the prevalence of tumour. In total, 32 polymorphic loci and 15 mutations were identified. For the first time, as many as 24 polymorphisms and all the mutations have been described to be associated with the neoplastic process in dogs. Most polymorphisms/mutations were found in the D-loop (31% of the polymorphisms and 93% of the mutations) and the COX1 gene sequence (16% of the polymorphisms). Blood or cancer heteroplasmy was noted in 93% of the mutations. Four of the 18 polymorphisms detected in the protein-coding genes were non-synonymous polymorphisms that have not been described in the literature so far (m.T7593C in COX2, m.G8807A in COX3, m.A9911G in ND4L, and m.T13299A in ND5) but resulted in changes in amino acids in proteins. These mutations and polymorphisms can affect mitochondrial functions and may be a result of cell adaptation to the changes in the environment occurring during carcinogenesis. The replacement of “wild type” mtDNA by a mutated molecule may be an important phenomenon accompanying carcinogenesis.

Complete mitochondrial genome database and standardized classification system for Canis lupus familiaris

To contribute to the complete mitogenome database of the species Canis lupus familiaris and shed more light on its origin, we have sequenced mitochondrial genomes of 120 modern dogs from worldwide populations. Together with all the previously published mitogenome sequences of acceptable quality, we have reconstructed a global phylogenetic tree of 555 C. l. familiaris mitogenomes and standardized haplogroup nomenclature. The phylogenetic tree presented here and available online at http://clf.mtdna.tree.cm.umk.pl/ could be further used by forensic and evolutionary geneticists as well cynologists, for data quality control and unambiguous haplogroup classification. Our in-depth phylogeographic analysis of all C. l. familiaris mitogenomes confirmed that domestic dogs may have originated in East Asia during the Mesolithic and Upper Paleolithic time periods and started to expand to other parts of the world during Neolithic times.

Local mitochondrial DNA haplotype databases needed for domestic dog populations that have experienced founder effect

Biological material from pets is often collected as evidence from crime scenes. Due to sample type and quality, mitochondrial DNA (mtDNA) is frequently evaluated to identify the potential contributor. MtDNA has a lower discriminatory power than nuclear DNA with multiple individuals in a population potentially carrying the same mtDNA sequence, or haplotype. The frequency distribution of mtDNA haplotypes in a population must be known in order to determine the evidentiary value of a match between crime scene evidence and the potential contributor of the biological material. This is especially important in geographic areas that include remote and/or isolated populations where founder effect may have lead to a decrease in genetic diversity and a non-random distribution of haplotypes relative to the population at large. Here we compared the haplotype diversity in dogs from the noncontiguous states of Alaska and Hawaii relative to the contiguous United States (US). We report a greater proportion of dogs carrying an A haplotype in Alaska relative to any other US population. Significant variation in the distribution of haplotype frequencies was discovered when comparing the haplotype diversity of dogs in Hawaii to that of the continental US. Each of these regions exhibits reduced genetic diversity relative to the contiguous US, likely due to founder effect. We recommend that specific databases be created to accurately represent the mitochondrial haplotype diversity in these remote areas. Furthermore, our work demonstrates the importance of local surveys for populations that may have experienced found effect.

Length heteroplasmy of the polyC-polyT-polyC stretch in the dog mtDNA control region

Previously, the mitochondrial control region of 214 Belgian dogs was sequenced. Analysis of this data indicated length heteroplasmy of the polyT stretch in the polyC-polyT-polyC stretch from positions 16661 to 16674. Nine polyC-polyT-polyC haplotype combinations were observed, consisting of seven major haplotypes (highest signal intensity) combined with minor haplotypes (lower signal intensity) one T shorter than the major haplotype in all but three dogs. The longer the polyT stretch, the smaller was the difference in signal intensity between the major and minor haplotype peaks. Additional sequencing, cloning, and PCR trap experiments were performed to further study the intra-individual variation of this mitochondrial DNA (mtDNA) region. Cloning experiments demonstrated that the proportion of clones displaying the minor haplotypes also increased with the length of the polyT stretch. Clone amplification showed that in vitro polymerase errors might contribute to the length heteroplasmy of polyT stretches with at least 10 Ts. Although major and minor polyC-polyT-polyC haplotypes did not differ intra-individually within and between tissues in this study, interpretation of polyT stretch variation should be handled with care in forensic casework.

Pet fur or fake fur? A forensic approach

BACKGROUND

In forensic science there are many types of crime that involve animals. Therefore, the identification of the species has become an essential investigative tool. The exhibits obtained from such offences are very often a challenge for forensic experts. Indeed, most biological materials are traces, hair or tanned fur. With hair samples, a common forensic approach should proceed from morphological and structural microscopic examination to DNA analysis. However, the microscopy of hair requires a lot of experience and a suitable comparative database to be able to recognize with a high degree of accuracy that a sample comes from a particular species and then to determine whether it is a protected one. DNA analysis offers the best opportunity to answer the question, 'What species is this?' In our work, we analyzed different samples of fur coming from China used to make hats and collars. Initially, the samples were examined under a microscope, then the mitochondrial DNA was tested for species identification. For this purpose, the genetic markers used were the 12S and 16S ribosomal RNA, while the hypervariable segment I of the control region was analyzed afterwards, to determine whether samples belonged to the same individual.

RESULTS

Microscopic examination showed that the fibres were of animal origin, although it was difficult to determine with a high degree of confidence which species they belonged to and if they came from a protected species. Therefore, DNA analysis was essential to try to clarify the species of these fur samples.

CONCLUSIONS

Macroscopic and microscopic analysis confirmed the hypothesis regarding the analyzed hair belonging to real animals, although it failed to prove with any kind of certainty which actual family it came from, therefore, the species remains unknown. Sequence data analysis and comparisons with the samples available in GenBank showed that the hair, in most cases, belonged to the Canidae family, and in one case only to Felidae.

Forensic informativity of ~3000 bp of coding sequence of domestic dog mtDNA

The discriminatory power of the noncoding control region (CR) of domestic dog mitochondrial DNA alone is relatively low. The extent to which the discriminatory power could be increased by analyzing additional highly variable coding regions of the mitochondrial genome (mtGenome) was therefore investigated. Genetic variability across the mtGenome was evaluated by phylogenetic analysis, and the three most variable ~1 kb coding regions identified. We then sampled 100 Swedish dogs to represent breeds in accordance with their frequency in the Swedish population. A previously published dataset of 59 dog mtGenomes collected in the United States was also analyzed. Inclusion of the three coding regions increased the exclusion capacity considerably for the Swedish sample, from 0.920 for the CR alone to 0.964 for all four regions. The number of mtDNA types among all 159 dogs increased from 41 to 72, the four most frequent CR haplotypes being resolved into 22 different haplotypes.

Dog mitochondrial genome sequencing to enhance dog mtDNA discrimination power in forensic casework

A Belgian dog population sample and several population studies worldwide have confirmed that only a limited number of mtDNA control region haplotypes is observed in the majority of dogs. The high population frequency of these haplotypes negatively impacts both the exclusion probability of dog mtDNA analysis and the evidential value of a match with one of these haplotypes in casework. Variation within the mtDNA coding region was explored to improve the discrimination power of dog mtDNA analysis. In the current study, the entire mitochondrial genome of 161 dogs was sequenced applying a quality assured strategy and resulted in a total of 119 different mitochondrial genome sequences. Our research was focused on those dogs with the six most common control region haplotypes from a previous Belgian population study. We identified 33 informative SNPs that successfully divide the six most common control region haplotypes into 32 clusters of mitochondrial genome sequences. Determining the identity of these 33 polymorphic sites in addition to control region sequencing in case of a match with one of these 6 control region haplotypes could augment the exclusion probability of forensic dog mtDNA analysis from 92.5% to 97.5%.

Population structure and genetic differentiation of livestock guard dog breeds from the Western Balkans

Livestock guard dog (LGD) breeds from the Western Balkans are a good example of how complex genetic diversity pattern observed in dog breeds has been shaped by transition in dog breeding practices. Despite their common geographical origin and relatively recent formal recognition as separate breeds, the Karst Shepherd, Sarplaninac and Tornjak show distinct population dynamics, assessed by pedigree, microsatellite and mtDNA data. We genotyped 493 dogs belonging to five dog breeds using a set of 18 microsatellite markers and sequenced mtDNA from 94 dogs from these breeds. Different demographic histories of the Karst Shepherd and Tornjak breeds are reflected in the pedigree data with the former breed having more unbalanced contributions of major ancestors and a realized effective population size of less than 20 animals. The highest allelic richness was found in Sarplaninac (5.94), followed by Tornjak (5.72), whereas Karst Shepherd dogs exhibited the lowest allelic richness (3.33). Similarly, the highest mtDNA haplotype diversity was found in Sarplaninac, followed by Tornjak and Karst Shepherd, where only one haplotype was found. Based on FST differentiation values and high percentages of animals correctly assigned, all breeds can be considered genetically distinct. However, using microsatellite data, common ancestry between the Karst Shepherd and Sarplaninac could not be reconstructed, despite pedigree and mtDNA evidence of their historical admixture. Using neighbour-joining, STRUCTURE or DAPC methods, Sarplaninac and Caucasian Shepherd breeds could not be separated and additionally showed close proximity in the NeighborNet tree. STRUCTURE analysis of the Tornjak breed demonstrated substructuring, which needs further investigation. Altogether, results of this study show that the official separation of these dog breeds strongly affected the resolution of genetic differentiation and thus suggest that the relationships between breeds are not only determined by breed relatedness, but in small populations even more importantly by stochastic effects.

Use of non-human DNA analysis in forensic science: a mini review

Analysis of non-human DNA in forensic science, first reported about two decades ago, is now commonplace. Results have been used as evidence in court in a variety of cases ranging from abduction and murder to patent infringement and dog attack. DNA from diverse species, including commonly encountered pets such as dogs and cats, to plants, viruses and bacteria has been used and the sheer potential offered by such analyses has been proven. In this review, using case examples throughout, we detail the considerable literature in this field.

Reviewing population studies for forensic purposes: Dog mitochondrial DNA

The identification of dog hair through mtDNA analysis has become increasingly important in the last 15 years, as it can provide associative evidence connecting victims and suspects. The evidential value of an mtDNA match between dog hair and its potential donor is determined by the random match probability of the haplotype. This probability is based on the haplotype’s population frequency estimate. Consequently, implementing a population study representative of the population relevant to the forensic case is vital to the correct evaluation of the evidence. This paper reviews numerous published dog mtDNA studies and shows that many of these studies vary widely in sampling strategies and data quality. Therefore, several features influencing the representativeness of a population sample are discussed. Moreover, recommendations are provided on how to set up a dog mtDNA population study and how to decide whether or not to include published data. This review emphasizes the need for improved dog mtDNA population data for forensic purposes, including targeting the entire mitochondrial genome. In particular, the creation of a publicly available database of qualitative dog mtDNA population studies would improve the genetic analysis of dog traces in forensic casework.

Analysis of mitochondrial DNA HVR1 haplotype of pure-bred domestic dogs in Japan

To develop DNA markers for forensic analysis, we examined the hypervariable region 1 (HVR1) sequences of 447 pure-bred domestic dogs (Canis lupus familiaris) that had been bred and raised in Japan. HVR1 is a 660-bp stretch of mitochondrial (mt) DNA. Among the 447 HVR1 sequences examined, we identified 58 haplotypes from 47 single nucleotide polymorphisms (SNPs) and two insertion-deletion (InDel) polymorphisms. The haplotype diversity inferred from inter-breed analysis (N=154, 88 breeds) was 0.929±0.011. Intra-breed analysis showed that the haplotype diversity of Golden Retrievers (N=53), Labrador Retrievers (N=67), Miniature Dachshunds (N=61), Toy Poodles (N=62), and Welsh Corgis (N=50) was 0.624±0.052, 0.722±0.029, 0.922±0.010, 0.877±0.020, and 0.443±0.084, respectively. The results of this genotype analysis were used to construct a dataset consisting of dog mtDNA HVR1 sequences for use in forensic applications in Japan.

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.

Pedigrees as a source of information in mtDNA studies of dogs and horses

The goal of this study was to demonstrate the usefulness of pedigree data in studies of mitochondrial DNA diversity in dogs and horses. Pedigree information allows for precisely choosing animals with distinct haplotypes for analysis, makes it possible to find rare haplotypes present exclusively in single individuals and helps to evaluate haplotype frequencies at the present and in the past. Estimating founder contributions to gene pools enables evaluating the parts of gene pools observed with the help of mtDNA analysis. An important aspect is also the financial benefits: using pedigree data, researchers can save a significant amount of time and money needed for sample collection and laboratory analysis.

Identification of single nucleotide polymorphisms within the mtDNA genome of the domestic dog to discriminate individuals with common HVI haplotypes

We sequenced the entire ∼16 kb canine mitochondrial genome (mtGenome) of 100 unrelated domestic dogs (Canis lupus familiaris) and compared these to 246 published sequences to assess hypervariable region I (HVI) haplotype frequencies. We then used all available sequences to identify informative single nucleotide polymorphisms (SNPs) outside of the control region for use in further resolving mtDNA haplotypes corresponding to common HVI haplotypes. Haplotype frequencies in our data set were highly correlated with previous ones (e.g., F(ST)=0.02, r=0.90), suggesting the total data set reasonably reflected the broader dog population. A total of 128 HVI haplotypes was represented. The 10 most common HVI haplotypes (n=184 dogs) represented 53.3% of the sample. We identified a total 71 SNPs in the mtGenomes (external to the control region) that resolved the 10 most common HVI haplotypes into 63 mtGenome subhaplotypes. The random match probability of the dataset based solely on the HVI sequence was 4%, whereas the random match probability of the mtGenome subhaplotypes was <1%. Thus, the panel of 71 SNPs identified in this study represents a useful forensic tool to further resolve the identity of individual dogs from mitochondrial DNA (mtDNA).

Automated DNA extraction of single dog hairs without roots for mitochondrial DNA analysis

Dogs are intensely integrated in human social life and their shed hairs can play a major role in forensic investigations. The overall aim of this study was to validate a semi-automated extraction method for mitochondrial DNA analysis of telogenic dog hairs. Extracted DNA was amplified with a 95% success rate from 43 samples using two new experimental designs in which the mitochondrial control region was amplified as a single large (± 1260 bp) amplicon or as two individual amplicons (HV1 and HV2; ± 650 and 350 bp) with tailed-primers. The results prove that the extraction of dog hair mitochondrial DNA can easily be automated to provide sufficient DNA yield for the amplification of a forensically useful long mitochondrial DNA fragment or alternatively two short fragments with minimal loss of sequence in case of degraded samples.

Belgian canine population and purebred study for forensics by improved mitochondrial DNA sequencing

In canine population studies for forensics, the mitochondrial DNA is profiled by sequencing the two hyper variable regions, HV1 and HV2 of the control region. In a first effort to create a Belgian population database some samples showed partially poor sequence quality. We demonstrated that a nuclear pseudogene was co-amplified with the mtDNA control region. Using a new combination of primers this adverse result was no longer observed and sequencing quality was improved. All former samples with poor sequence data were reanalyzed. Furthermore, the forensic canine population study was extended to 208 breed and mixed dogs. In total, 58 haplotypes were identified, resulting in an exclusion capacity of 0.92. The profile distribution of the Belgian population sample was not significantly different from those observed in population studies of three other countries. In addition to the total population study 107 Belgian registered pedigree dogs of six breeds were profiled. Per breed, the obtained haplotypes were supplemented with those from population and purebred studies. The combined data revealed that some haplotypes were more or less prominent present in particular dog breeds. The statistically significant differences in haplotype distribution between breeds and population sample can have consequences on mtDNA databasing and matching probabilities in forensics.

ISFG: recommendations regarding the use of non-human (animal) DNA in forensic genetic investigations

The use of non-human DNA typing in forensic science investigations, and specifically that from animal DNA, is ever increasing. The term animal DNA in this document refers to animal species encountered in a forensic science examination but does not include human DNA. Non-human DNA may either be: the trade and possession of a species, or products derived from a species, which is contrary to legislation; as evidence where the crime is against a person or property; instances of animal cruelty; or where the animal is the offender. The first instance is addressed by determining the species present, and the other scenarios can often be addressed by assigning a DNA sample to a particular individual organism. Currently there is little standardization of methodologies used in the forensic analysis of animal DNA or in reporting styles. The recommendations in this document relate specifically to animal DNA that is integral to a forensic science investigation and are not relevant to the breeding of animals for commercial purposes. This DNA commission was formed out of discussions at the International Society for Forensic Genetics 23rd Congress in Buenos Aires to outline recommendations on the use of non-human DNA in a forensic science investigation. Due to the scope of non-human DNA typing that is possible, the remit of this commission is confined to animal DNA typing only.