Population genetic analysis and genome-wide association study of patellar luxation in a Thai population of Pomeranian dogs

- Patellar luxation is equally common in male and female Pomeranians.
- Medial patellar luxation is a widespread hereditary disease in Pomeranians.
- The high heritability in the Pomeranian indicating that genetic factors are important.
- SC5 and, BMPR1B are good candidate genes of patellar luxation in Pomeranians.

The genetics of patellar luxation (PL) were investigated in Pomeranian dogs presented at the Small Animal Hospital, Faculty of Veterinary Science, Chulalongkorn University. A cohort of 339 Pomeranian dogs, part of a four-generation pedigree of 842 Pomeranians, was screened for PL from 2006 to 2013. PL was present in 77% of the screened dogs, with 84% having bilateral and 16% unilateral luxation. Medial PL was more common (95%) than lateral PL (2%) or bidirectional PL (3%). The risk of PL was similar in male and female dogs (female:male relative risk 1.11, 95% CI 0.98-1.25). The heritability of PL in the screened population was 0.44 ± 0.04 using a threshold model. A genome-wide association study of PL (48 cases and 48 controls) using a high-density SNP array indicated the possible involvement of 15 chromosomal regions, of which CFA05 and CFA32 remained associated in a larger study involving an additional 128 cases and 7 controls. Candidate genes in these regions may be involved in the pathogenesis of PL in Pomeranian dogs.