RT Journal Article SR Electronic T1 A Novel Human Opsin in the Inner Retina JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 600 OP 605 DO 10.1523/JNEUROSCI.20-02-00600.2000 VO 20 IS 2 A1 Ignacio Provencio A1 Ignacio R. Rodriguez A1 Guisen Jiang A1 William Pär Hayes A1 Ernesto F. Moreira A1 Mark D. Rollag YR 2000 UL http://www.jneurosci.org/content/20/2/600.abstract AB Here we report the identification of a novel human opsin, melanopsin, that is expressed in cells of the mammalian inner retina. The human melanopsin gene consists of 10 exons and is mapped to chromosome 10q22. This chromosomal localization and gene structure differs significantly from that of other human opsins that typically have four to seven exons. A survey of 26 anatomical sites indicates that, in humans, melanopsin is expressed only in the eye. In situ hybridization histochemistry shows that melanopsin expression is restricted to cells within the ganglion and amacrine cell layers of the primate and murine retinas. Notably, expression is not observed in retinal photoreceptor cells, the opsin-containing cells of the outer retina that initiate vision. The unique inner retinal localization of melanopsin suggests that it is not involved in image formation but rather may mediate nonvisual photoreceptive tasks, such as the regulation of circadian rhythms and the acute suppression of pineal melatonin. The anatomical distribution of melanopsin-positive retinal cells is similar to the pattern of cells known to project from the retina to the suprachiasmatic nuclei of the hypothalamus, a primary circadian pacemaker.