ULTRASTRUCTURAL FEATURES OF RETINAL DYSTROPHY IN MUTANT VITILIGO MICE

Ultrastructural features of the retinal pigment epithelium and photore ceptor cells were studied in vitiligo (C57BL/6 mi(vit)/mi(vit)) mice. Eyes from 12-day- to 56-week-old animals were analysed. Abnormal photo receptors were seen in 12-day-old mice. By 3 weeks malformed outer seg ments were evident in the posterior and equatorial retina, but normal photoreceptors were present in the periphery. By 28 weeks, a marked gr adient in cell loss was evident, with a progressive increase in cell v iability along the posterior-peripheral axis. Viable intact photorecep tors were still present in the peripheral retina of 56-week-old mice. Melanosome content varied between adjacent pigment epithelium cells in both the posterior and peripheral retina. In the choroid, however, a steep posterior-peripheral gradient in melanosome content was evident with highest pigmentation in the periphery. In the optic nerve head re gion abnormal development of photoreceptors was correlated with prolif eration of abnormal pigment epithelium cells. Accumulation of rod oute r segment debris in the posterior and peripheral subretinal space prec eded photoreceptor cell death. Short pigment epithelial microvilli wit hout proper attachment to photoreceptors are suggestive of alterations in pigment-epithelium-photoreceptor interaction, which might affect p hotoreceptor differentiation and phagocytosis of rod outer segments by pigment epithelium cells. (C) 1995 Academic Press Limited.