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Description

Melanopsin (UniProt Q9UHM6, also known as Opsin-4) is encoded by the OPN4 (also known as MOP) gene (Gene ID 94233) in human. Opsins belong to the superfamily of G protein-coupled receptors (GPCRs). Melanopsin is a blue light-sensitive opsin protein that is capable of rendering cells intrinsically light responsive. Melanopsin expression defines a population of retinal ganglion cells that are intrinsically photosensitive (ipRGCs). Melanopsin allows mammals to measure irradiance for centrally mediated responses such as circadian entrainment. In addition, the information generated by melanopsin is used by the visual system as a signal for light adaptation. Using melanopsin-dependent phototransduction mechanism coupled with extrinsic signals originating with rods and cones, ipRGCs can encode light levels over many decimal orders, allowing the visual system to adapt to a broad range of light intensity from starlight to broad daylight.