An immunohistochemical study of an autosomal dominant feline rod/cone dysplasia (Rdy cats)

An autosomal dominant, early onset feline model of rod/cone dysplasia has b een described. The clinical features, light and electron microscopy, and th e electrophysiology were documented. Mie have now examined in more detail t he histopathological and immunohistochemical changes during the early phase of the disease using antibodies against opsin, synaptophysin, glial fibril lary acidic protein (GFAP) and an epithelial marker (MNF118). We have also demonstrated programmed cell death by a modified TUNEL (Terminal deoxynucle otidyl transferase, Uridine triphosphate, Nick End Labelling) technique. In the Rdy cats, there was significant photoreceptor degeneration between 5 and 17 weeks of age. The TUNEL-labeled cell and pyknotic cell counts in th e outer nuclear layer peaked at around 9 weeks of age. Accumulation of opsi n in the entire outer nuclear layer of the retina was noted with opsin-immu nolabeled rod neurite sprouting. There was a reduction in synaptophysin imm unoreactivity in the outer plexiform layer. The Muller cells were activated and expressed GFAP. No significant change of immunolabeling of MNF118 was found. These findings closely parallel those seen in human RP. (C) 1999 Aca demic Press.