Melanopsin phototransduction: slowly emerging from the dark.
- BiologyProgress in brain research
Melanopsin phototransduction: beyond canonical cascades
- BiologyThe Journal of experimental biology
Recent findings and discoveries are discussed that have challenged the prevailing view of melanopsin phototransduction as a single pathway that influences solely non-image forming functions.
Photon capture and signalling by melanopsin retinal ganglion cells
Fundamental parameters governing intrinsic light responses and associated spike generation of retinal ganglion cells are reported, finding that a flash causing a few hundred isomerized melanopsin molecules in a retina is sufficient for reaching threshold for the pupillary light reflex.
Diverse types of ganglion cell photoreceptors in the mammalian retina
- BiologyProgress in Retinal and Eye Research
Vertebrate ancient opsin and melanopsin: divergent irradiance detectors.
- BiologyPhotochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology
This review discusses the history of discovery for the vertebrate ancient (va) opsin and melanopsin genes, as well as focusing on the evolution, expression profile, functional role and broader physiological significance of each photopigment.
The Evolution and Function of Melanopsin in Craniates
The evolutionary history of the melanopsin gene, its diverse patterns of expression and transcriptional output, the functional roles so far determined, and the clinical significance of this critical and phylogenetically most ancient opsin-based system of irradiance detection are discussed.
MELANOPSIN PHOTOPIGMENT, LIGHT PHOTOTRANSDUCTION PATHWAY, AND PIGMENT REGENERATION
The structural relationship of melanopsin to invertebrate opsins provides clues to its evolutionary origin, and suggests that its function as a light sensitive pigment is likely different than classic visual photopigments in rod and cone photoreceptors.
Genetic Advances in Ophthalmology: The Role of Melanopsin-Expressing, Intrinsically Photosensitive Retinal Ganglion Cells in the Circadian Organization of the Visual System
- BiologySeminars in ophthalmology
This review will cover the role that melanopsin and ipRGCs play in the circadian organization of the visual system and note that both central and peripheral oscillators share an endogenous, circadian-driven, transcription–translation feedback loop that cycles with a periodicity of approximately 24 hours.
The active site of melanopsin: the biological clock photoreceptor.
- BiologyJournal of the American Chemical Society
These findings, analogous to spectral changes observed in the G89Q bovine rhodopsin mutant, suggest that single site mutations can convert photopigments into visual light sensors or nonvisual sensory photoreceptors.
Phototransduction and the Evolution of Photoreceptors
- BiologyCurrent Biology
SHOWING 1-10 OF 68 REFERENCES
Melanopsin forms a functional short-wavelength photopigment.
The experiments constitute the first direct demonstration that melanopsin forms a photopigment capable of activating a G-protein, but its spectral properties are not consistent with the action spectrum for circadian entrainment.
Melanopsin and rod–cone photoreceptive systems account for all major accessory visual functions in mice
The rod–cone and melanopsin systems together seem to provide all of the photic input for these accessory visual functions such as pupillary light reflex and circadian photo-entrainment.
Addition of human melanopsin renders mammalian cells photoresponsive
It is shown that heterologous expression of human melanopsin in a mouse paraneuronal cell line (Neuro-2a) is sufficient to render these cells photoreceptive and that melanopigment functions as a bistable pigment in this system, having an intrinsic photoisomerase regeneration function that is chromatically shifted to longer wavelengths.
Melanopsin Is Required for Non-Image-Forming Photic Responses in Blind Mice
It is observed that mice with both outer-retinal degeneration and a deficiency in melanopsin exhibited complete loss of photoentrainment of the circadian oscillator, pupillary light responses, photic suppression of arylalkylamine-N-acetyltransferase transcript, and acute suppression of locomotor activity by light, indicating the importance of both nonvisual and classical visual photoreceptor systems for nonvisual photic responses in mammals.
Illumination of the Melanopsin Signaling Pathway
It is found that expression of melanopsin in Xenopus oocytes results in light-dependent activation of membrane currents through the Gαq/Gα11 G protein pathway, with an action spectrum closely matching that of melanpsin-expressing ipRGCs and of behavioral responses to light in mice lacking rods and cones.
Diminished Pupillary Light Reflex at High Irradiances in Melanopsin-Knockout Mice
It is reported that in mice with the melanopsin gene ablated, RGCs retrograde-labeled from the suprachiasmatic nuclei were no longer intrinsically photosensitive, although their number, morphology, and projections were unchanged.
Melanopsin: An opsin in melanophores, brain, and eye.
- BiologyProceedings of the National Academy of Sciences of the United States of America
Melanopsin mRNA is expressed in hypothalamic sites thought to contain deep brain photoreceptors and in the iris, a structure known to be directly photosensitive in amphibians, and expression in retinal and nonretinal tissues suggests a role in vision and nonvisual photoreceptive tasks.
Induction of photosensitivity by heterologous expression of melanopsin
It is concluded that mammalian melanopsin is a functional sensory photopigment, that it is the photopigsment of ganglion-cell photoreceptors, and that these photoreCEPTors may use an invertebrate-like phototransduction cascade.
Non-rod, non-cone photoreception in rodents and teleost fish.
- BiologyNovartis Foundation symposium
Non-rod, non-cone ocular photoreceptors in mammals and fish are compared, and the criteria used to place candidate photopigment molecules into a functional context is examined.
Photoreceptors regulating circadian behavior: a mouse model.
- BiologyJournal of biological rhythms
The data suggest that circadian photoreception can be maintained by a very small number of rod or cone cells without outer segments, or, alternatively, is performed by an unrecognized class of photoreceptive cell within the mammalian retina.