Power of a Labrador Retriever-Greyhound pedigree for linkage analysis of hip dysplasia and osteoarthritis.
OBJECTIVE
To estimate the number of dogs required to find linkage to heritable traits of hip dysplasia in dogs from an experimental pedigree.


METHODS
147 Labrador Retrievers, Greyhounds, and their crossbreed offspring.


METHODS
Labrador Retrievers with hip dysplasia were crossed with unaffected Greyhounds. Age at detection of femoral capital ossification, distraction index (DI), hip joint dorsolateral subluxation (DLS) score, and hip joint osteoarthritis (OA) were recorded. Power to find linkage of a single marker to a quantitative trait locus (QTL) controlling 100% of the variation in a dysplastic trait in the backcross dogs was determined.


RESULTS
For the DI at the observed effect size, recombination fraction of 0.05, and heterozygosity of 0.75, 35 dogs in the backcross of the F1 to the Greyhound generation would yield linkage at a power of 0.8. For the DLS score, 35 dogs in the backcross to the Labrador Retriever generation would be required for linkage at the same power. For OSS, 45 dogs in the backcross to the founding Labrador Retrievers would yield linkage at the same power. Fewer dogs were projected to be necessary to find linkage to hip OA. Testing for linkage to the DLS at 4 loci simultaneously, each controlling 25% of the phenotypic variation, yielded an overall power of 0.7 CONCLUSIONS AND CLINICAL SIGNIFICANCE: Based on this conservative single-marker estimate, this pedigree has the requisite power to find microsatellites linked to susceptibility loci for hip dysplasia and hip OA by breeding a reasonable number of backcross dogs.
Todhunter
Rory J
RJ
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Casella
George
G
Bliss
Stuart P
SP
Lust
George
G
Williams
Alma Jo
AJ
Hamilton
Samuel
S
Dykes
Nathan L
NL
Yeager
Amy E
AE
Gilbert
Robert O
RO
Burton-Wurster
Nancy I
NI
Mellersh
Cathryn C
CC
Acland
Gregory M
GM
D000375:Aging; D000818:Animals; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D004285:Dogs / Q000235:genetics*; D005260:Female; D018703:Founder Effect; D008040:Genetic Linkage; D020022:Genetic Predisposition to Disease; D006579:Heterozygote; D006619:Hip Dysplasia, Canine / Q000235:genetics*; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D010003:Osteoarthritis / Q000235:genetics*; D010375:Pedigree; D040641:Quantitative Trait Loci / Q000235:genetics; D018401:Sample Size