Canine microsatellite polymorphisms as the resolution of an illegal animal death case in a Hungarian zoological gardens

Developmental validation of a novel multiple genotyping assay with 24 Canine STR loci

Canine individual identification and parentage testing are essential in various fields, including forensics and breeding programs. This study aimed to develop and validate the Canine 25 A kit, a multiplex polymerase chain reaction (PCR) system designed to address these critical requirements. This novel system enables the simultaneous amplification of 24 canine autosomal short tandem repeat (STR) loci and one sex-determining marker. Validation of the Canine 25 A kit was conducted following the Scientific Working Group on DNA Analysis Methods (SWGDAM) guidelines, demonstrating significant sensitivity, high inhibitor tolerance, canine specificity within a mixture, species specificity, and precision in genotype determination. The Canine 25 A kit was crucial in resolving several forensic cases, such as casework samples from a dog attack incident and parentage determination. Its effectiveness in genotyping these samples highlights its significance in forensic applications. Population genetic parameter analysis revealed a high discriminatory power, as indicated by the calculated combined discrimination power (CDP) values for each breed exceeding 0.999 999 999 999, while the combined power of exclusion (CPE) surpassed 0.9999. Overall, the Canine 25 A kit offers a precise and dependable tool for canine individual identification and parentage determination.

Construction of an in-house allelic ladder for Canine Genotypes™ Panel 2.1 Kit

Dogs (Canis lupus familiaris) are among the most common companion animals in the Republic of Korea. Recently, there have been many criminal cases of dog cruelty, injury, and theft, among others. This has increased the importance of dog-related biological evidence at crime scenes. The National Forensic Service of the Republic of Korea conducts short tandem repeat (STR) analysis using the Thermo Scientific Canine Genotypes™ Panel 2.1 Kit (Canine Kit) to identify individual dogs through forensic analysis. The Canine Kit was developed as a forensic STR kit for the identification of individual dogs. However, an allelic ladder was neither developed nor included in the commercial kit, leaving an issue of accurate genotyping. Primer details for the 18 markers used in the Canine Kit are proprietary information, and thus, unavailable to end-users. In this study, an allelic ladder was constructed with 160 fragments by combining 158 fragments of STR alleles obtained by nested PCR and two fragments artificially obtained from the sex-determination marker. By including the new allelic ladder in analysis of samples amplified with the Canine Kit, the accuracy and reliability of data analysis were improved. Application of this allelic ladder would be helpful for interlaboratory data sharing and standardization of canine genotype databases.

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.

Validation of two canine STR multiplex-assays following the ISFG recommendations for non-human DNA analysis

To gain general acceptance forensic DNA testing in animals needs to improve standardization of analysis methods and data interpretation. Recently, the International Society of Forensic Genetics (ISFG) took particular care of this topic by publishing recommendations for forensic non-human DNA analysis following the successful example of human DNA analysis in order to provide a basis for harmonization of the still existing inter-laboratory variability. By following these recommendations we demonstrate the performance of two short tandem repeat (STR) multiplexes for forensic identity testing of canine biological material. Thirteen STRs and two sex-specific markers were selected and validated according to the ISFG guidelines. Population genetic parameters were calculated based on 295 dog samples collected in Austria (124) and Germany (171). A repeat-based nomenclature of the mainly tetrameric STRs and corresponding allelic ladders are presented. All 146 different alleles included in the ladders were sequenced for correct allele calling. Additionally, a canine cell line (DH82-D3167) was evaluated as standard reference material.

Developmental validation of Mini-DogFiler for degraded canine DNA

Dogs (Canis lupus familiaris) are kept as pets in 39% of American households and are, therefore, a significant source of potentially probative biological evidence. As with any biological evidence, degradation can occur as a consequence of environmental exposure causing fracturing of the DNA and a resulting loss of intact template. Degraded human DNA analysis has benefited from the application of primer sets that amplify shorter nuclear sequences for core STR loci (miniSTRs), resulting in improved DNA profiles. This same approach was applied to our core canine STR loci. The 16-locus "DogFiler" panel was redesigned into three panels of miniSTRs for analysis of degraded canine DNA, with all primer pairs producing amplicons below 205 base pairs in length. These new miniSTR marker panels - known as Mini-DogFiler - were validated according to SWGDAM guidelines, and concordance with the original 16-locus multiplex was demonstrated through genotyping 1244 samples. The combination of these miniSTRs and a half-volume reaction increased the amplification success of degraded and low copy number canine biological samples resulting in a near three-fold increase in reportable alleles. This assemblage of miniSTRs along with the DogFiler panel and associated allelic ladder are the first non-human DNA profiling system to parallel the human forensic paradigm.

Developmental validation of DogFiler, a novel multiplex for canine DNA profiling in forensic casework

While the analysis of human DNA has been the focus of large-scale collaborative endeavors, non-human forensic DNA analysis has not benefited from the same funding streams and coordination of effort. Consequently, the development of standard marker panels, allelic ladders and allele-specific sequence data comparable to those established for human forensic genetics has lagged. To meet that need for domestic dogs, we investigated sequence data provided by the published 7.6X dog genome for novel short tandem repeat markers that met our criteria for sensitivity, stability, robustness, polymorphic information content, and ease of scoring. Fifteen unlinked tetranucleotide repeat markers were selected from a pool of 3113 candidate markers and assembled with a sex-linked marker into a multiplex capable of generating a full profile with as little as 60pg of nuclear DNA. An accompanying allelic ladder was assembled and sequenced to obtain detailed repeat motif data. Validation was carried out according to SWGDAM guidelines, and the DogFiler panel has been integrated into forensic casework and accepted in courts across the U.S. Applying various formulae for calculating random match probabilities for inbred populations, estimates for this panel of markers have proven to be comparable to those obtained in human forensic genetics. The DogFiler panel and the associated allelic ladder represent the first published non-human profiling system to fully address all SWGDAM recommendations.

A population genetic database of cat breeds developed in coordination with a domestic cat STR multiplex

A simple tandem repeat (STR) PCR-based typing system developed for the genetic individualization of domestic cat samples has been used to generate a population genetic database of domestic cat breeds. A panel of 10 tetranucleotide STR loci and a gender-identifying sequence tagged site (STS) were co-amplified in genomic DNA of 1043 individuals representing 38 cat breeds. The STR panel exhibits relatively high heterozygosity in cat breeds, with an average 10-locus heterozygosity of 0.71, which represents an average of 38 breed-specific heterozygosities for the 10-member panel. When the entire set of breed individuals was analyzed as a single population, a heterozygosity of 0.87 was observed. Heterozygosities obtained for the 10 loci range from 0.72 to 0.96. The power for genetic individualization of domestic cat samples of the multiplex is high, with a probability of match (p(m)) of 6.2E-14, using a conservative θ = 0.05.

Sequence determinants of human microsatellite variability

BACKGROUND

Microsatellite loci are frequently used in genomic studies of DNA sequence repeats and in population studies of genetic variability. To investigate the effect of sequence properties of microsatellites on their level of variability we have analyzed genotypes at 627 microsatellite loci in 1,048 worldwide individuals from the HGDP-CEPH cell line panel together with the DNA sequences of these microsatellites in the human RefSeq database.

RESULTS

Calibrating PCR fragment lengths in individual genotypes by using the RefSeq sequence enabled us to infer repeat number in the HGDP-CEPH dataset and to calculate the mean number of repeats (as opposed to the mean PCR fragment length), under the assumption that differences in PCR fragment length reflect differences in the numbers of repeats in the embedded repeat sequences. We find the mean and maximum numbers of repeats across individuals to be positively correlated with heterozygosity. The size and composition of the repeat unit of a microsatellite are also important factors in predicting heterozygosity, with tetra-nucleotide repeat units high in G/C content leading to higher heterozygosity. Finally, we find that microsatellites containing more separate sets of repeated motifs generally have higher heterozygosity.

CONCLUSIONS

These results suggest that sequence properties of microsatellites have a significant impact in determining the features of human microsatellite variability.

Estimating the probability of identity in a random dog population using 15 highly polymorphic canine STR markers

Dog DNA-profiling is becoming an important supplementary technology for the investigation of accident and crime, as dogs are intensely integrated in human social life. We investigated 15 highly polymorphic canine STR markers and two sex-related markers of 131 randomly selected dogs from the area around Innsbruck, Tyrol, Austria, which were co-amplified in three PCR multiplex reactions (ZUBECA6, FH2132, FH2087Ua, ZUBECA4, WILMSTF, PEZ15, PEZ6, FH2611, FH2087Ub, FH2054, PEZ12, PEZ2, FH2010, FH2079 and VWF.X). Linkage testing for our set of marker suggested no evidence for linkage between the loci. Heterozygosity (HET), polymorphism information content (PIC) and the probability of identity (P((ID)theoretical), P((ID)unbiased), P((ID)sib)) were calculated for each marker. The HET((exp))-values of the 15 markers lie between 0.6 (VWF.X) and 0.9 (ZUBECA6), P((ID)sib)-values were found to range between 0.49 (VWF.X) and 0.28 (ZUBECA6). Moreover, the P((ID)sib) was computed for sets of loci by sequentially adding single loci to estimate the information content and the usefulness of the selected marker sets for the identification of dogs. The estimated P((ID)sib) value of all 15 markers amounted to 8.5 x 10(-8). The presented estimations turned out to be a helpful approach for a reasonable choice of markers for the individualisation of dogs.

A proposed nomenclature for 15 canine-specific polymorphic STR loci for forensic purposes

We performed a population study on 15 polymorphic STR loci (FH2010, FH2079, PEZ2, VWF.X, FH2054, FH2087Ub, FH2611, WILMS-TF, PEZ12, PEZ15, PEZ6, FH2087Ua, ZUBECA4, ZUBECA6, FH2132) on 131 randomly selected dogs. Alleles were identified and grouped according to their estimated fragment length using fixed allelic bins encompassing one base-pair. The allele assignment was confirmed by sequence analysis of homozygote and cloned heterozygote alleles. In order to develop a uniform repeat-based nomenclature, extensive sequence analysis was performed on a selection of alleles from each STR locus. The proposed nomenclature refers to the internationally recognised recommendations for human-specific STR loci in forensic applications. The 15 canine-specific STR loci were grouped into 3 classes (simple STRs, compound STRs and complex/hypervariable STRs) according to their complexity and variability within the repeat structure. Finally, we evaluated the precision of fragment size estimation on a capillary electrophoresis platform and demonstrated reproducibility of fragment length estimation for single base-pair intermediate alleles.