ABCR abbreviation for ATP-binding cassette transporter retina; other name: rim protein. A protein found in the disc membrane of the outer segment of photoreceptor cells of the retina. It consists of 2273 amino acids, and is presumed to function in the transport of retinoids. Mutations in the ABCR gene, at 1p21-p23, are associated with Stargardt and age-related macular dystrophies.