Figure 1.

Pathways contributing to cone visual pigment regeneration in the mammalian retina. Cone pigment regeneration is mediated by both the classic visual cycle as well as an intraretinal visual cycle involving Müller glia. Des1, an enzyme originally recognized for its involvement in de novo ceramide production, is reported to catalyze the isomerization of retinol and has been proposed to be the physiologic isomerase of the cone-specific, intraretinal visual cycle. Here, we tested this proposal through the use of Müller cell Des1 conditional knockout mice. Chemical intermediates of the classic visual cycle are omitted for simplicity.