Retinal dysfunction in basigin deficiency

PURPOSE. To examine the retina of basigin (Bsg) knockout mice by electrophy siological and histologic methods and thereby to determine the possible fun ction of Bsg in phototransduction and retinal development. METHODS. Scotopic and photopic electroretinograms (ERGs) were recorded from 11 wild-type, 12 heterozygous, and 8 homozygous Bsg gene knockout mice of different ages. The retinas were also examined by histologic and immunolabe ling methods. RESULTS. Bsg knockout mice of 5 to 41 weeks of age showed a decrease in the amplitude of all components of both the photopic and scotopic ERGs. In con trast. the fundus and the fluorescein fundus angiography and morphology of the retina at the light microscopic level appeared to be normal until 8 wee ks of age in Bsg knockout mice. Thereafter, the length of outer segment and outer nuclear layers decreased with increasing age. Immunohistochemical an alysis localized Bsg protein in a variety of cells in the retina, especiall y in the pigment epithelium, the upper outer plexiform layer and the inner segments of photoreceptor cells. CONCLUSIONS. The results demonstrated that both rod and cone function were severely affected from an early age by the targeted disruption of the Bsg g ene. In spite of abnormal ERGs, the photoreceptor cells maintained normal m orphology up to 8 weeks. Thereafter, the photoreceptor cells degenerated gr adually and were almost ablated by 41 weeks.