Melanopsin is a type of photopigment belonging to a larger family of light-sensitive retinal proteins called opsins and encoded by the gene Opn4.[5] In the mammalian retina, there are two additional categories of opsins, both involved in the formation of visual images: rhodopsin and photopsin (types I, II, and III) in the rod and cone photoreceptor cells, respectively.
In humans, melanopsin is found in intrinsically photosensitive retinal ganglion cells (ipRGCs).[6] It is also found in the iris of mice and primates.[7] Melanopsin is also found in rats, amphioxus, and other chordates.[8] ipRGCs are photoreceptor cells which are particularly sensitive to the absorption of short-wavelength (blue) visible light and communicate information directly to the area of the brain called the suprachiasmatic nucleus (SCN), also known as the central "body clock", in mammals.[9] 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).[10] According to one study, melanopsin has been found in eighteen sites in the human brain (outside 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.[11] Melanopsin is also expressed in human cones. However, only 0.11% to 0.55% of human cones express melanopsin and are exclusively found in the peripheral regions of the retina.[12] The human peripheral retina senses light at high intensities that is best explained by four different photopigment classes.[13]
- ^ a b c GRCh38: Ensembl release 89: ENSG00000122375 – Ensembl, May 2017
- ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000021799 – Ensembl, May 2017
- ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
- ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
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Hankins_2007was invoked but never defined (see the help page). - ^ Provencio I, Warthen DM (2012). "Melanopsin, the photopigment of intrinsically photosensitive retinal ganglion cells". Wiley Interdisciplinary Reviews: Membrane Transport and Signaling. 1 (2): 228–237. doi:10.1002/wmts.29.
- ^ Xue T, Do MT, Riccio A, Jiang Z, Hsieh J, Wang HC, et al. (November 2011). "Melanopsin signalling in mammalian iris and retina". Nature. 479 (7371): 67–73. Bibcode:2011Natur.479...67X. doi:10.1038/nature10567. PMC 3270891. PMID 22051675.
- ^ Angueyra JM, Pulido C, Malagón G, Nasi E, Gomez M (2012). "Melanopsin-expressing amphioxus photoreceptors transduce light via a phospholipase C signaling cascade". PLOS ONE. 7 (1): e29813. Bibcode:2012PLoSO...729813A. doi:10.1371/journal.pone.0029813. PMC 3250494. PMID 22235344.
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S Hattwas invoked but never defined (see the help page). - ^ Cite error: The named reference
pmid18804284was invoked but never defined (see the help page). - ^ Nissilä J, Mänttäri S, Tuominen H, Särkioja T, Takala T, Saarela S, et al. (2012). "P-780 – The abundance and distribution of melanopsin (OPN4) protein in human brain". European Psychiatry. 27: 1–8. doi:10.1016/S0924-9338(12)74947-7. S2CID 82045589.
- ^ Dkhissi-Benyahya O, Rieux C, Hut RA, Cooper HM (April 2006). "Immunohistochemical evidence of a melanopsin cone in human retina". Investigative Ophthalmology & Visual Science. 47 (4): 1636–1641. doi:10.1167/iovs.05-1459. PMID 16565403.
- ^ Horiguchi H, Winawer J, Dougherty RF, Wandell BA (January 2013). "Human trichromacy revisited". Proceedings of the National Academy of Sciences of the United States of America. 110 (3): E260–E269. Bibcode:2013PNAS..110E.260H. doi:10.1073/pnas.1214240110. PMC 3549098. PMID 23256158.