Abstract:
Aims: To validate the dog as an animal model of naturally occurring myopia by
identifying genetic and environmental factors which are associated with
myopia development in the Labrador Retriever.
Methods: A large pedigree of Labrador Retrievers was phenotyped for refractive error.
Using statistical (familial aggregation) analysis, refractive error data was used
to investigate the inheritance of the trait within the pedigree. DNA samples
were taken for later analysis. Potential environmental factors early in life were
also studied in relation to adult refractive error; including birth weight, growth
rate, season of birth, ocular pathology and litter size. DNA samples were
extracted and a pilot genetic association study was designed to identify genetic
loci for canine refractive error using a genome wide SNP array with a myopic
case group and a non-myopic control group.
Results: A significant prevalence (37%) of myopia was found within the pedigree
studied. Familial aggregation analysis demonstrated a significant genetic
contribution, as well as showing a strong environmental contribution.
Heritability of refractive error was 0.506. Smaller litters were shown to have
significantly higher levels of myopia. No association was found between any
environmental factors and adult refractive error, apart from season of birth in
one age tertile. A genetic pilot study was designed to test for genetic loci
which contribute to canine refractive error.
Conclusions: The Labrador Retriever is potentially an ideal animal model for the study of
human myopia; the condition is naturally occurring in dogs, develops in a
significant proportion of the population and can be phenotyped noninvasively.
This study is the first to demonstrate the inheritance of myopia in
any animal other than humans. The dog genome allows for myopia to be
studied at a molecular level and due to the domesticated nature of the dog,
breeding and environmental manipulations can also be conducted to identify
further aspects of myopia causatio