Retriever du Labrador
HeredityIn the breed Labrador Retriever, a variant in the ABCA4 gene has been identified to be associated with a canine form of the Stargardt disease, causing clinical signs similar to the human disease. The ABCA4 gene encodes for a membrane transporter protein located in the outer segments of rod and cone photoreceptors and plays an important role in the visual cycle. The described variant leads to an increased lipofuscin accumulation in the retinal pigment epithelium (RPE) and to a degeneration of both cone and rod photoreceptors. Therefore, affected dogs are visually impaired under daylight and dimlight conditions. Further symptoms are: focal hypertrophy and hyperplasia in the retinal pigment epithelium, the pupils are dilated under daylight, pupillary light and dazzle reflexes are abnormal while menace responses are present.