Update from the end of year 2 of research underway by Dr. Iivanainen of University of Helsinki to hopefully lead to a genetic test to aid breeders in controlling hip dysplasia.
The overall objective of our study is to perform a genome wide association study (GWAS) of canine hip dysplasia (CHD) in German Shepherds using a large sample cohort (200 cases and 200 controls). CHD is a common problem in many breeds. The dysplasia phenotype is graded from radiographs. In this study, we use the standards of Fédération Cynologique Internationale (FCI) ranging from A (healthy) to E (severely dysplastic). Each hip joint is graded individually. As the disease progresses also the risk for hip joint arthrosis – a painful and incurable condition – increases. The identification of genetic risk factors would enable the development of genetic tests to aid the breeders in controlling the disease. Four hundred animals consisting of carefully matched pairs of healthy and affected individuals should provide enough power for the association study to uncover the major genetic risk factors for this degenerative disease.
At present, we have collected a study cohort of 1141 dogs including 411 cases and 730 controls. From the study cohort, we have thus far genotyped 167 severe (“D” or “E” hip joints) and 38 mild (“C” or “D” hip joints) cases and matched controls (“A” hip joints) for all of them (see the figure below).
Figure. The present size of the total sample cohort (with C-, D-, or E-graded cases and Agraded controls), balanced cohort (with C-, D- or E-graded cases and individually matched Agraded controls), and the number of determined genotypes from the balanced cohort in relation to the overall objective of genome-wide association study using 200 dysplastic and 200 control dogs.
Since last report in June 2015, we have collected an independent second cohort (833 dogs, four breeds) and performed larger genome-wide association study with 526 dogs. Several clusters of SNPs suggestive of association were detected in eight chromosomes. The validation of these SNPs will take place in 2016 using the independent second cohort.