Melanopsin-Containing Retinal Ganglion Cells: Architecture, Projections, and Intrinsic Photosensitivity

  title={Melanopsin-Containing Retinal Ganglion Cells: Architecture, Projections, and Intrinsic Photosensitivity},
  author={Samer Hattar and Hsi Wen Liao and M. Takao and David M. Berson and King-Wai Yau},
  pages={1065 - 1070}
The primary circadian pacemaker, in the suprachiasmatic nucleus (SCN) of the mammalian brain, is photoentrained by light signals from the eyes through the retinohypothalamic tract. Retinal rod and cone cells are not required for photoentrainment. Recent evidence suggests that the entraining photoreceptors are retinal ganglion cells (RGCs) that project to the SCN. The visual pigment for this photoreceptor may be melanopsin, an opsin-like protein whose coding messenger RNA is found in a subset of… 

Central projections of melanopsin‐expressing retinal ganglion cells in the mouse

Staining patterns after monocular enucleation revealed that the projections of these cells are overwhelmingly crossed except for the projection to the SCN, which is bilaterally symmetrical, and that other ganglion cells do contribute at least some retinal input to these targets.

Melanopsin is expressed in PACAP-containing retinal ganglion cells of the human retinohypothalamic tract.

Given the expression of melanopsin in PACAP-containing RGCs of the human RHT, this photoreceptor is a likely first base in the chain of events leading to photoentrainment of both normal and blind people.

A Broad Role for Melanopsin in Nonvisual Photoreception

The results suggest that melanopsin expression defines a subset of RGCs that play a broad role in theregulation of nonvisual photoreception, providing collateralized projections that contribute to circadian entrainment, negative masking, the regulation of sleep-wake states, and the pupillary light reflex.

Immunohistochemical evidence of a melanopsin cone in human retina.

The presence of melanopsin in human cones suggests image and non-image-forming roles in visual responses at both the cone input and ganglion cell output stages and their involvement in a broad spectrum of irradiance detection functions in the visual system.

Melanopsin and non-melanopsin expressing retinal ganglion cells innervate the hypothalamic suprachiasmatic nucleus

It appears that the rod/cone system of photoreceptors may provide signals to the SCN circadian system independent of intrinsically light-sensitive melanopsin ganglion cells.

Melanopsin Regulates Visual Processing in the Mouse Retina

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.

Melanopsin, the photopigment of intrinsically photosensitive retinal ganglion cells

Melanopsin (gene symbol: Opn4) is the G protein-coupled photopigment that confers photosensitivity upon intrinsically photosensitive retinal ganglion cells (ipRGCs). ipRGCs are the third class of

Melanopsin—Shedding Light on the Elusive Circadian Photopigment

Although melanopsin is clearly the leading candidate for the elusive photopigment of the circadian system, further research is needed to resolve the mystery posed by its absorbance spectrum and to fully elucidate its role in circadian photoentrainment.



The Photopigment Melanopsin Is Exclusively Present in Pituitary Adenylate Cyclase-Activating Polypeptide-Containing Retinal Ganglion Cells of the Retinohypothalamic Tract

Cloned rat melanopsin photopigment cDNA is cloned and in situ hybridization histochemistry combined with immunohistochemistry and colocalization studies reveal that melanops in was found exclusively in the PACAP-containing retinal ganglion cells located at the surface of somata and dendrites.

A Novel Human Opsin in the Inner Retina

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.

Melanopsin in cells of origin of the retinohypothalamic tract

It is shown that most retinal ganglion cells that project to the SCN express the photopigment melanopsin, which mediates circadian entrainment in mice.

The retinohypothalamic tract originates from a distinct subset of retinal ganglion cells

The retinal ganglion cells giving rise to retinohypothalamic projections in the rat were identified using retrograde transport of horseradish peroxidase (HRP) or Fluoro Gold injected into the

Phototransduction by Retinal Ganglion Cells That Set the Circadian Clock

It is shown that retinal ganglion cells innervating the SCN are intrinsically photosensitive, and depolarized in response to light even when all synaptic input from rods and cones was blocked.

A retinohypothalamic projection in the rat

The retinohypothalamic tract in the rat appears to arise from the ganglion cells of the retina and to terminate on the smaller dendritic branches of the neurons of the suprachiasmatic nucleus.

Responses of neurones of the rat suprachiasmatic nucleus to retinal illumination under photopic and scotopic conditions

Light acting either via rod or cone pathways could have powerful, opposing actions on SCN neurones, and the presence of these neuronal responses suggests a role for rod and cone photoreceptors in SCN function.

Origins of crossed and uncrossed retinal projections in pigmented and albino mice

The extent of the binocular cortical field in albino mice, as revealed by recording from single cells, was almost normal; although the input from the ipsilateral eye was weaker than normal, most

Retinal projections in mice with inherited retinal degeneration: Implications for circadian photoentrainment

Pseudorabies virus is used as a neuroanatomical tract tracer in mice to address a series of questions about which retinal cells mediate circadian responses to light and the nature of the retinohypothalamic projection.