PCR ANALYSIS OF DNA FROM 70-YEAR-OLD SECTIONS OF RODLESS RETINA DEMONSTRATES IDENTITY WITH THE MOUSE RD DEFECT

Rodless retina (gene symbol, r) was discovered in mice by Keeler 70 ye ars ago and was first described in this journal as an autosomal recess ive mutation leading to ''the absence of the visual cells (rods), the external nuclear layer, and the external molecular layer'' [Keeler, C. E. (1924) Proc. Natl. Acad. Sci. USA 10, 329-333]. The mutation was s tudied by Keeler and others in the United States and Europe over the n ext decade, but Keeler's stock was destroyed in 1939, and mice definit ively related to his by pedigree and progeny tests also appeared to ha ve been lost by the end of World War II. In the early 1950s Bruckner i n Basel recognized mice with a similar retinal phenotype. Investigator s in London and Strasbourg analyzed descendants of Bruckner's mice and concluded, on the basis of different pathogenesis from r, that they c arried a new mutation, which came later to be called retinal degenerat ion, rd. The relationship of r and rd has been unsettled ever since. N ow that the rd phenotype is known to be due to a nonsense mutation in the rod photoreceptor cGMP phosphodiesterase beta-subunit gene, we hop ed to settle the question by direct analysis of r DNA. DNA was liberat ed from 70-year-old histological sections of +/r and r/r eyes, the onl y extant r DNA, and the regions encompassing the nonsense mutation amp lified by the polymerase chain reaction (PCR). Sequence analysis of th e PCR products revealed the presence of the same nonsense mutation and two intron polymorphisms in r DNA. PCR and direct sequence analysis o f 11 strains of mice known to carry rd (or a similar allele) also reve aled the presence of the nonsense mutation and the same intron polymor phisms. The fact that all r and rd mice contain an identical defect an d intron polymorphisms in the phosphodiesterase beta-subunit gene sett les beyond reasonable doubt that a single mutation arising >70 years a go is now widely distributed through inbred mouse strains. Because of the extensive use of the name in publications of the past 40 years, we propose that the gene continue to be designated retinal degeneration, rd.