Sequence analysis of ADAM9 in affected and carrier GITs revealed a deletion of exons 15 and 16 which alters the reading frame leading to a premature stop codon. This mutation was absent from 34 other dog breeds. A variable and, at times, very late onset of gPRA was confirmed in GITs by a relatively mild retinal degeneration at an advanced age. Hence, the identification of the genetic defect underlying gPRA in the GIT represents a suitable model for cone-rod dystrophy of humans, with superior potential to elucidate functional consequences of the recently described null mutations in the human ADAM9 gene.
ExperimentName: Canine model of Adam9 loss-of-function
NonHumanModel: Canis lupus familiaris
GeneAlteration: The affected dogs have homozygous disruption of the Adam9 gene by a deletion of regions from exons 15 and 16.
ModelPhenotype: HP:0001105 (Retinal atrophy), HP:0000529 (Progressive visual loss), HP:0000580 (Pigmentary retinopathy), HP:0000662 (Nyctalopia)
HumanPhenotype: HP:0011463 (Childhood onset), HP:0000548 (Cone/cone-rod dystrophy), HP:0007663 (Reduced visual acuity), HP:0001141 (Severely reduced visual acuity), HP:0007994 (Peripheral visual field loss), HP:0000545 (Myopia), HP:0000483 (Astigmatism), HP:0000523 (Subcapsular cataract)
ModelEvidence: The affected dogs have been described as having generalized progressive retinal atrophy. Complete loss of all retinal layers was observed in affected animals (Figures 1H-1P). This matches the mode of inheritance and progressive nature of the human disease state, as well as the retinal abnormalities and visual defects.
ModelVariant: The model harbors a targeted deletion that does not have an equivalent / orthologous variant reported in human patients.