Visual pigment–deficient cones survive and mediate visual signaling despite the lack of outer segments

Abstract

Significance The study of visual pigments (rhodopsin in rods and cone opsins in cones) in vision has a long and illustrious history. It is well established that rhodopsin is required for rod phototransduction, outer segment formation, and rod viability. It is not known if the same is true for the cones. By using the cone opsin–deficient mice, we made the surprising observation that cones survive for at least 12 mo without cone opsins, suggesting that cone opsins are dispensable for cone viability. Furthermore, cone opsin–deficient cones continue to mediate visual signaling by relaying the rod signal through rod–cone gap junctions. Our finding represents a major difference between the two types of photoreceptors in vertebrates: rods and cones.