An eye on cone outer segments

The retinal degeneration slow (Rds) gene is required in rod photoreceptor cells for morphogenesis of outer segments (OSs) and cell survival. On page 59, Farjo et al. report that cone photoreceptor cells also develop abnormal OS structures in the absence of Rds, but they remain functional, suggesting that the protein may have different roles in the two cell types and hinting at ways to treat some degenerative eye disorders in humans.

Rods constitute more than 95% of the photoreceptor population in rodent retina, making the structure an imperfect model for the central portion of the human retina, called the macula, which is composed mostly of cones and is largely responsible for visual acuity. Recently, researchers created a knock-out mouse, Nrl^−/−, in which rod progenitor cells are transformed into cones, enabling...