A NOVEL DYSTROPHIN ISOFORM IS REQUIRED FOR NORMAL RETINAL ELECTROPHYSIOLOGY

Dystrophin is present in the outer plexiform layer of the retina and i s required for normal retinal function as measured by electroretinogra phy. We describe the identification of a novel isoform of dystrophin ( Dp260) present in the mouse retina. The unique 5' terminus of the mRNA originates from a newly identified exon and is spliced in frame to ex on 30 of the Duchenne muscular dystrophy (DMD) gene. The retinal isofo rm of dystrophin has 13 novel amino acids as its N-terminus followed b y most of the dystrophin rod domain and the cysteine-rich C-terminal d omains. Analysis of mouse tissues indicated this isoform of dystrophin is expressed in retina, brain and cardiac tissue. Comparison of retin al electrophysiology in mdx and mdx(Cv3) mouse suggests that Dp260 is required for normal retinal function.