title: Melanopsin signalling in mammalian iris and retina.
abstract: Non-mammalian vertebrates have an intrinsically photosensitive iris and thus a local pupillary light reflex (PLR). In contrast, it is thought that the PLR in mammals generally requires neuronal circuitry connecting the eye and the brain. Here we report that an intrinsic component of the PLR is in fact widespread in nocturnal and crepuscular mammals. In mouse, this intrinsic PLR requires the visual pigment melanopsin; it also requires PLCβ4, a vertebrate homologue of the Drosophila NorpA phospholipase C which mediates rhabdomeric phototransduction. The Plcb4(-/-) genotype, in addition to removing the intrinsic PLR, also essentially eliminates the intrinsic light response of the M1 subtype of melanopsin-expressing, intrinsically photosensitive retinal ganglion cells (M1-ipRGCs), which are by far the most photosensitive ipRGC subtype and also have the largest response to light. Ablating in mouse the expression of both TRPC6 and TRPC7, members of the TRP channel superfamily, also essentially eliminated the M1-ipRGC light response but the intrinsic PLR was not affected. Thus, melanopsin signalling exists in both iris and retina, involving a PLCβ4-mediated pathway that nonetheless diverges in the two locations.
authors: Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA. txue77@gmail.com
authors: T
authors: T
authors: Xue
authors: M T H
authors: MT
authors: Do
authors: A
authors: A
authors: Riccio
authors: Z
authors: Z
authors: Jiang
authors: J
authors: J
authors: Hsieh
authors: H C
authors: HC
authors: Wang
authors: S L
authors: SL
authors: Merbs
authors: D S
authors: DS
authors: Welsbie
authors: T
authors: T
authors: Yoshioka
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authors: Weissgerber
authors: S
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authors: Stolz
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authors: Flockerzi
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authors: Freichel
authors: M I
authors: MI
authors: Simon
authors: D E
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authors: Clapham
authors: K-W
authors: KW
authors: Yau
mesh_terms: D000818:Animals; D007498:Iris / Q000033:anatomy & histology / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects*; D055537:Light Signal Transduction / Q000502:physiology / Q000528:radiation effects*; D008322:Mammals / Q000502:physiology*; D051379:Mice; D054799:Phospholipase C beta / Q000378:metabolism; D010775:Photic Stimulation; D011323:Primates / Q000502:physiology; D012025:Reflex, Pupillary / Q000502:physiology / Q000528:radiation effects; D012160:Retina / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects*; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000528:radiation effects; D017299:Rod Opsins / Q000378:metabolism*; D000099210:Melanopsin
chemical_list: D054799:Phospholipase C beta; D017299:Rod Opsins; D000099210:Melanopsin; C518043:Plcb4 protein, mouse