Given the elevated expression of Edn2 and Gfap apparent in the retina of Prom1-KO mice, we hypothesized that ET-2, the mature form of the Edn2 product (Goldman, 2014), might induce the GFAP expression apparent in association with retinal degeneration in the Prom1-deficient animals. Here, GFAP is linked to retinal degeneration.