Protein of the day: Melanopsin

Melanopsin is a type of photopigment belonging to a larger family of light-sensitive retinal proteins called opsins and encoded by the gene Opn4. Two other opsins in the mammalian retina are both involved in the formation of visual images: rhodopsin and photopsin in the rod and cone photoreceptor cells, respectively.

In humans, melanopsins is found in intrinsically photosensitive retinal ganglion cells (ipRGCs), as well as the cerebral cortex of the brain and in epidermal skin. Melanopsin also is found rats, mice, amphioxus, and other chordates. ipRGCs are photoreceptor cells which are particularly sensitive to the absorption of short-wavelength visible light and communicate information directly to the area of the brain called the suprachiasmatic nucleus (SCN), otherwise known as the central "body clock" in mammals. Consequently, melanopsin plays an important non-image-forming role in the setting of circadian rhythms as well as other functions. Mutations in the Opn4 gene can lead to clinical disorders, such as Seasonal Affective Disorder (SAD). According to one study, melanopsin has been found in eighteen sites in the human brain (outside of the retinohypothalamic tract), intracellularly, in a granular pattern, in the cerebral cortex, the cerebellar cortex and several phylogenetically old regions, primarily in neuronal soma, not in nuclei. When you play with your phone or tablet in the evening, this is the one protein responsible with changing your circadian rhythm and messing up with your brain. 

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