Impairment of rod cGMP-gated channel alpha-subunit expression leads to photoreceptor and bipolar cell degeneration

PURPOSE. TO determine whether alterations in rod cGMP-gated channel functio n mediate retinal degeneration, a transgenic approach in which the alpha su bunit of the rod cGMP-gated channel is reduced by the expression of an anti sense RNA was used. METHODS. A 890-bp fragment of the 5' mouse rod cGMP-gated channel cDNA was cloned in the antisense orientation under the control of the strong bacteri al cytomegalovirus promoter. This antisense construct was used to generate transgenic mice in which the expression of the antisense transgene was meas ured by reverse transcription-polymerase chain reaction. Histologic, immuno cytochemical, and TdT-dUTP terminal nick-end labeling (TUNEL) analyses were performed on control and transgenic retina sections to determine the effec ts of antisense expression on specific cell types. RESULTS. The antisense RNA was able to inhibit the translation of the rod c hannel protein in an in vitro assay. Three transgenic mouse lines expressin g the antisense construct were obtained. Molecular analyses showed that the antisense is expressed in the eye of each transgenic mouse line, where it reduces rod cGMP-gated channel RNA expression. Histologic and immunocytoche mical data showed that transgenic retinas have a reduced number of photorec eptors and bipolar cells. TUNEL staining confirmed that photoreceptor and b ipolar cells degenerate along an apoptotic pathway. CONCLUSIONS. Impairment of rod cGMP-gated channel or subunit expression lea ds to photoreceptor and bipolar cell degeneration. These transgenic mice ar e the first model of retinal degeneration caused by an alteration in the ex pression of the rod cd;MP-gated channel. This model system can be used to t est therapies designed to slow or stalled retinal degenerations.