Quantitative trait loci for hip dysplasia in a crossbreed canine pedigree

Canine hip dysplasia is a common developmental inherited trait characterized by hip laxity, subluxation or incongruity of the femoral head and acetabulum in affected hips. The inheritance pattern is complex and the mutations contributing to trait expression are unknown. In the study reported here, 240 microsatellite markers distributed in 38 autosomes and the X chromosome were genotyped on 152 dogs from three generations of a crossbred pedigree based on trait-free Greyhound and dysplastic Labrador Retriever founders. Interval mapping was undertaken to map the QTL underlying the quantitative dysplastic traits of maximum passive hip laxity (the distraction index), the dorsolateral subluxation score, and the Norberg angle. Permutation testing was used to derive the chromosome-wide level of significance at p < 0.05 for each QTL. Chromosomes 4, 9, 10, 11 (p < 0.01), 16, 20, 22, 25, 29 (p < 0.01), 30, 35, and 37 harbor putative QTL for one or more traits. Successful detection of QTL was due to the crossbreed pedigree, multiple-trait measurements, control of environmental background, and marked advancement in canine mapping tools.