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An Urban Experience
Quantitative diseases
Quantitative diseases are, as mentioned, caused by accumulation of disease predisposing genes. Since several genes are involved in the development of
these diseases and since they are also often under the influence of environmental factors it is more difficult to establish genetic testing for them. In spite of this, we
will undoubtedly see more tests developed in the future. Recently a test aimed at predicting the probability for developing hip dysplasia in Labrador retriever was established.[6] The test has been validated in 126 Danish Labrador retrievers with radiographic hip scores and estimated breeding values registered in the Danish Kennel Club. No significant statistical correlation between phenotypic scores and genotypic predisposition was detected.[7]
Conclusions and future perspectives
Genetic testing is an extremely valuable tool to combat inherited diseases. However, three important aspects have to be taken into consideration before a specific
test can be recommended to be included in a breeding scheme: (i) unless the test has unambiguously been proven to target the causative mutation it has to be validated in the population at hand; (ii) the relative impact on welfare of the disease which is targeted has to be considered in the context of the general health status
of the breed; (iii) considerations concerning selection intensity in order to avoid further reduction of genetic variation has to be made.
With the progress and decreasing costs in regard to full genome sequencing there will be a still growing number of tests on the market. Since dog owners and breeders show great enthusiasm with regard to genetic testing, genetic counseling is of great importance. Hence, there will be a future demand for veterinarians specialized within the area of Clinical Genetics.
[1] Proschowsky HF, Flagstad A, Cirera S, Jørgensen CB, and Fredholm M. Identification of a mutation in the CHAT gene of old Danish pointing dogs affected with Congenital Myasthenic Syndrome. Journal of Heredity, 2007, 98: 539-543.
[2] Parker, H.G., Kukekova, A.V., Akey, D.T., Goldstein, O., Kirkness, E.F., Baysac, K.C., et al. Breed relationships facilitate fine-mapping studies: a 7.8-kb deletion cosegregates with Collie eye anomaly across multiple dog breeds. Genome Research, 2007, Vol. 17 (11): 1562-1571.
[3] Fredholm M, Larsen RC, Jönsson M, Söderlund MA, Hardon T, Proschowsky HF. Discrepancy in compliance between the clinical and genetic diagnosis of choroidal hypoplasia in Danish Rough Collies and Shetland Sheepdogs. Animal Genetics, 2016, doi: 10.1111/age.12405
[4] Grall, A., Guaguère, E., Planchaist, S., Grond, S., Bourrat, E., Hausser, I., et al. PNPLA1 mutations
cause autosomal recessive congenital ichthyosis in golden retriever dogs and humans. Nature Genetics, 2012, Vol. 44 (2): 140-147.
[5] Jensen CN. Ichthyosis in the Golden Retriever: variation of clinical manifestation and breeding aspects in Golden Retrievers that are homozygous for the PNPLA-1 mutation. Master Thesis, 2014, University of Copenhagen.
[6] Bartolomé N., Segarra S., Artieda M., Francino O., Sánchez E., Szczypiorska M., Casellas J., Tejedor D., Cerdeira J., Martínez A., Velasco A., Sánchez A. A Genetic Predictive Model for Canine Hip Dysplasia: Integration of Genome Wide Association Study (GWAS) and Candidate Gene Approaches. PLoS One, 2015, doi: 10:e0122558.
[7] Bank A, Ström A. Validation of the Dysgen Hip Dysplasis DNA test in the Danish population of Labrador Retrievers. Master Thesis, 2016, University of Copenhagen.

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