A new, albino-beige mouse: giant granules in retinal pigment epithelium

Albino-beige mice were produced in order to combine two experimentally useful characteristics, albinism and lysosomal dysfunction, in the same animal. The retinal pigment epithelium of albino-beige mice formed giant intracellular granules. Exposure of albino-beige mice to white light of 150 foot-candles for 3 to 10 hr induced marked phagocytosis of rod outer segment fragments by the retinal pigment epithelium, resulting in intracellular accumulations of undigested disk membranes within the giant granules. Additional, incompletely processed membranes accumulated as the mice aged or were exposed to 150 foot-candle light for longer periods. Such accumulations of ingested membranes were not observed in the pigment epithelium of exposed or aging albino mice heterozygous for the beige gene. Because of its altered processing of ingested outer segment membranes, this new albino mouse should be useful for studying the possible roles of the retinal pigment epithelium in the maintenance of photoreceptor cells and in their recovery from light damage and other insults.