A NULL MUTATION IN THE PHOTORECEPTOR GUANYLATE-CYCLASE GENE CAUSES THE RETINAL DEGENERATION CHICKEN PHENOTYPE

The retinas of the retinal degeneration (rd) chicken are fully develop ed and possess normal morphology at hatching but fail to respond to li ght stimulation. Analyses of retinal cGMP, the internal messenger of p hototransduction, show that the amount of cGMP in predegenerate, fully developed rd/rd photoreceptors is 5-10 times less than that seen in n ormal photoreceptor cells, We show that the low levels of cGMP in rd c hicken retina are a consequence of a null mutation in the photorecepto r guanylate cyclase (GC1) gene, Thus, the rd chicken is a model for hu man Leber's congenital amaurosis. Absence of GC1 in rd retina prevents phototransduction and affects survival of rods and cones but does not interfere with normal photoreceptor development.