Salamander blue-sensitive cones lost during metamorphosis.

The tiger salamander lives in shallow water with bright light in the aquatic phase, and in dim tunnels or caves in the terrestrial phase. In the aquatic phase, there are five types of photoreceptors--two types of rods and three types of cones. Our previous studies showed that the green rods and blue-sensitive cones contain the same visual pigment and have the same absorbance spectra; however, the green rods have a larger photon-catch area and thus have higher light sensitivity than the blue-sensitive cones.

Downregulation of cone-specific gene expression and degeneration of cone photoreceptors in the Rpe65-/- mouse at early ages.

Purpose: RPE65 is essential for the generation of 11-cis retinal. Rod photoreceptors in the RPE65-knockout (Rpe65(-/-)) mouse are known to degenerate slowly with age. This study was designed to examine cone photoreceptors and the expression of cone-specific genes in the Rpe65(-/-) mouse.

Does constitutive phosphorylation protect against photoreceptor degeneration in Rpe65-/- mice?

Despite the presence of this virgin opsin, Rpe65-/- rods are behaving like dark-adapted rods. These results argue that opsin which has not been exposed to 11-cis retinal and is constitutively phosphorylated, does not generate the activity generally associated with the bleached apoprotein. However, increased light-independent activation of transducin (due to bleached opsin) could be demonstrated after the addition of exogenous 11-cis retinal.

A novel Xenopus SWS2, P434 visual pigment: structure, cellular location, and spectral analyses.

Purpose: The purpose of this study was to clone and characterize the green rod pigment in Xenopus laevis.

Methods: The cDNA for the Xenopus "green rod" pigment was cloned and sequenced from Xenopus retina mRNA by reverse transcription polymerase chain reaction and the 5' end cloned by rapid amplification of the cDNA ends. The cellular localization of the Xenopus opsin was determined by immunolabeling of flat-mounted retinas using a specific antibody against this opsin.

Correlation of regenerable opsin with rod ERG signal in Rpe65-/- mice during development and aging.

Purpose: RPE65 has been shown to be essential for the production of 11-cis retinal by the retinal pigment epithelium. Mutations in RPE65 are known to be associated with severe forms of early-onset retinal dystrophy. This project was designed to determine the amount of regenerable opsin in Rpe65-/- mice during development and aging, and to examine the function of this rhodopsin by electroretinography (ERG).