Opsins are members of theG protein-coupled receptor superfamily. In addition to the visual opsins, mammals possess severalphotoreceptive non-visual opsins that are expressed in tissues outside the eye. The opsin-3 gene is strongly expressed in brain andtestis and weakly expressed in liver,placenta, heart, lung, skeletal muscle,kidney, andpancreas. The gene is expressed in the skin[8] and may also be expressed in theretina. The protein has the canonical features of a photoreceptive opsin protein,[7] however in human skin, OPN3 is not photoreceptive and acts as a negative regulator ofmelanogenesis.[9]
When OPN3 analogues are expressed inneurons, activation by light inhibitsneurotransmitter release.[10][11] This makes these analogues useful tools foroptogenetic silencing, a method to study the impact of specific neurons on brain function.
^Halford S, Freedman MS, Bellingham J, Inglis SL, Poopalasundaram S, Soni BG, et al. (March 2001). "Characterization of a novel human opsin gene with wide tissue expression and identification of embedded and flanking genes on chromosome 1q43".Genomics.72 (2):203–208.doi:10.1006/geno.2001.6469.PMID11401433.
Halford S, Bellingham J, Ocaka L, Fox M, Johnson S, Foster RG, Hunt DM (2002). "Assignment of panopsin (OPN3) to human chromosome band 1q43 by in situ hybridization and somatic cell hybrids".Cytogenetics and Cell Genetics.95 (3–4):234–235.doi:10.1159/000059351.PMID12063405.S2CID24099335.
Kasper G, Taudien S, Staub E, Mennerich D, Rieder M, Hinzmann B, et al. (July 2002). "Different structural organization of the encephalopsin gene in man and mouse".Gene.295 (1):27–32.doi:10.1016/S0378-1119(02)00799-0.PMID12242008.
Alam NA, Gorman P, Jaeger EE, Kelsell D, Leigh IM, Ratnavel R, et al. (December 2003). "Germline deletions of EXO1 do not cause colorectal tumors and lesions which are null for EXO1 do not have microsatellite instability".Cancer Genetics and Cytogenetics.147 (2):121–127.doi:10.1016/S0165-4608(03)00196-1.PMID14623461.
