Primary Lens Luxation in Australian Tenterfield and Miniature Bull Terriers is Due to An Old ADAMTS17 Mutation and is an Additive Trait

Primary Lens Luxation (PLL) is an inherited disease common in Terrier breeds. A truncating mutation in the ADAMTS17 orthologue on CFA03 is reported to cause PLL in 17 breeds, mostly Terriers. This study investigated the mode of inheritance and penetrance of PLL, age of the ADAMTS17 mutation, and other possible causes of PLL in Australian Tenterfield Terriers and Miniature Bull Terriers. The ADAMTS17 mutation and 30 nearby microsatellites on CFA03 were genotyped in 66 Australian Tenterfield Terriers, and 74 Miniature Bull Terriers. Lifetime risk of developing clinical PLL in homozygote and heterozygous animals, penetrance of PLL in general population, and recurrence risk of the disease for offspring and siblings of an index case was estimated. The effect of the ADAMTS17 mutation on the risk of PLL was dose and age dependent, and best fitted an additive model. Primary lens luxation was fully penetrant in homozygotes over 6 years and incompletely penetrant with a significant risk of PLL in heterozygote animals. Microsatellite haplotype testing estimated the mutation to be an old mutation, consistent with its appearance on several different background haplotypes and suggesting it entered the tested Tenterfield Terrier population at least three times, and the tested Miniature Bull Terrier population once. Finite polygenic model and survival analyses suggested that the ADAMTS17 mutation is the main cause of PLL in these breeds, and if the PLL phenotype is controlled by factors other than this mutation, such as a second locus or an environmental effect, the effect is much less than that of this disease