Prime Editor-mediated Correction of a Pathogenic Mutation in Purebred Dogs

Canine hip dysplasia (HD) is a multifactorial disease caused by interactions between genetic and environmental factors. HD, which mainly occurs in medium- to large-sized dogs, is a disease that causes severe pain and requires surgical intervention. However, the procedure is not straight-forward, and the only way to ameliorate the situation is to exclude individual dogs with HD from breeding programs. Recently, prime editing (PE), a novel genome editing tool based on the CRISPR-Cas9 system, has been developed and validated in plants and mice. In this study, we successfully corrected a mutation related to HD in Labrador retriever dogs for the first time. We collected cells from a dog diagnosed with HD, corrected the mutation using PE, and generated mutation-corrected dogs by somatic cell nuclear transfer. The results indicate that PE technology can potentially be used as a platform to correct genetic defects in dogs.

Genome-wide association studies for canine hip dysplasia in single and multiple populations – implications and potential novel risk loci

Background Association mapping studies of quantitative trait loci (QTL) for canine hip dysplasia (CHD) can contribute to the understanding of the genetic background of this common and debilitating disease and might contribute to its genetic improvement. The power of association studies for CHD is limited by relatively small sample numbers for CHD records within countries, suggesting potential benefits of joining data across countries. However, this is complicated due to the use of different scoring systems across countries. In this study, we incorporated routinely assessed CHD records and genotype data of German Shepherd dogs from two countries (UK and Sweden) to perform genome-wide association studies (GWAS) within populations using different variations of CHD phenotypes. As phenotypes, dogs were either classified into cases and controls based on the Fédération Cynologique Internationale (FCI) five-level grading of the worst hip or the FCI grade was treated as an ordinal trait. In a subsequent meta-analysis, we added publicly available data from a Finnish population and performed the GWAS across all populations. Genetic associations for the CHD phenotypes were evaluated in a linear mixed model using 62,089 SNPs. Results Multiple SNPs with genome-wide significant and suggestive associations were detected in single-population GWAS and the meta-analysis. Few of these SNPs overlapped between populations or between single-population GWAS and the meta-analysis, suggesting that many CHD-related QTL are population-specific. More significant or suggestive SNPs were identified when FCI grades were used as phenotypes in comparison to the case-control approach. MED13 (Chr 9) and PLEKHA7 (Chr 21) emerged as novel positional candidate genes associated with hip dysplasia. Conclusions Our findings confirm the complex genetic nature of hip dysplasia in dogs, with multiple loci associated with the trait, most of which are population-specific. Routinely assessed CHD information collected across countries provide an opportunity to increase sample sizes and statistical power for association studies. While the lack of standardisation of CHD assessment schemes across countries poses a challenge, we showed that conversion of traits can be utilised to overcome this obstacle.

Study on canine hip dysplasia and its diagnosis by imaging and molecular genetics techniques

The present paper is a bibliographical research on canine hip dysplasia using imaging and molecular genetics techniques. Ever since the first description in 1935 made by Schnelle, canine hip dysplasia has remained one of the most diagnosed orthopedic conditions present in the dog breeds. The gold standard method of diagnosis of hip dysplasia is the radiological examination in hip-extended position. While the radiological examination focuses mainly on the individual for the diagnosis of this condition, methods of diagnosis of an entire population are sought, and these methods are represented by molecular genetics techniques. Naming the etiology of canine hip dysplasia and finding out the latest methods of genetically and radiologically diagnosis of canine hip dysplasia and the best alternatives of treatment for this disease. Canine hip dysplasia continues to be a major problem for owners, breeders and veterinarians. Currently, there are five standardized systems worldwide that deal with the grading of canine hip dysplasia. In addition to digital radiology, CT and ultrasonographic examination are feasible diagnosis methods. Even if the standard method of diagnosis remains the radiological examination in the present, the near future provides to be of the molecular genetic techniques.

The Use of Sixty Degree Rotation of the Acetabulum for Treatment of Dogs With Canine Hip Dysplasia. A Short Case Series

Triple pelvic osteotomy (TPO) is a prophylactic surgical procedure performed on dogs with canine hip dysplasia. The procedure is indicated in skeletally immature dogs without secondary osteoarthritis (OA). It has been suggested that 60° of rotation is excessive and is associated with poor outcome. The objective of the study was to assess the medium term outcome in dogs having undergone triple pelvic osteotomy (TPO) using 60° dedicated plates. Nine TPOs were performed in seven dogs with hip dysplasia. Eight of nine hips had 72–100% osseous union at the time of revisit. The mean time to final radiographic recheck was 200 days (range, 185–229 days). The mean time to follow-up was 11.5 months (range 11–12 months). All 7 dogs had regained full function and did not require supplemental analgesia. Pelvic canal narrowing was noted in the two dogs with bilateral surgeries, but no clinical consequences were noted according to owner's statement.If more than 40 degrees reduction angles at Ortolani test, 60° of rotation of the acetabulum can be used successfully in dogs with hip dysplasia. At the time of mid-term follow-up, all dogs in this case series had full function.

Early Diagnosis of Canine Hip Laxity: Correlation between Clinical Orthopedic Examinations and the FCI Scoring Method in a Closed Cohort of Rottweilers

Canine hip dysplasia is a multifactorial disorder characterized by hip laxity and osteoarthritis. The early diagnosis of hip laxity is an important topic in small animal orthopedics. This study aimed to evaluate the correlation between clinical orthopedic examinations and the Fédération Cynologique Internationale (FCI) scoring method. Thirty purebred Rottweilers were examined at approximately four (20 ± 2 weeks), eight (35 ± 2 weeks), and twelve months of age (54 ± 1 weeks), respectively. The Ortolani, Barlow, and Bardens tests and reduction/subluxation angle measurements were performed at each time. FCI scoring was conducted at the third examination time. Positive correlations were recorded between the reduction angle and Ortolani test, reduction angle and FCI score, and Ortolani test and FCI score for the second and third examination dates. No correlation was observed between the subluxation angle and other methods. Despite previous studies reporting 16–20 weeks as the earliest age for diagnosing hip laxity in dogs, in our study, early diagnosis was possible from the age of 35 ± 2 weeks. This difference might originate from the small sample size, low number of the dogs with severe grades of laxity, and breed differences.

An across-breed validation study of 46 genetic markers in canine hip dysplasia

Background Canine hip dysplasia (CHD) is a common disease, with a complex genetic background. Dogs with severe CHD sometimes also suffer from osteoarthritis (OA), an inflammatory, often painful and incurable condition. Previous studies have reported breed-specific genetic loci associated with different hip dysplasia and OA phenotypes. However, the independent replication of the known associations within or across breeds has been difficult due to variable phenotype measures, inadequate sample sizes and the existence of population specific variants. Results We execute a validation study of 46 genetic markers in a cohort of nearly 1600 dogs from ten different breeds. We categorize the dogs into cases and controls according to the hip scoring system defined by the Fédération Cynologique Internationale (FCI). We validate 21 different loci associated on fourteen chromosomes. Twenty of these associated with CHD in specific breeds, whereas one locus is unique to the across-breed study. We show that genes involved in the neddylation pathway are enriched among the genes in the validated loci. Neddylation contributes to many cellular functions including inflammation. Conclusions Our study successfully replicates many loci and highlights the complex genetic architecture of CHD. Further characterisation of the associated loci could reveal CHD-relevant genes and pathways for improved understanding of the disease pathogenesis.