title: Melanopsin ganglion cells extend dendrites into the outer retina during early postnatal development.
abstract: Melanopsin ganglion cells express the photopigment melanopsin and are the first functional photoreceptors to develop in the mammalian retina. They have been shown to play a variety of important roles in visual development and behavior in the early postnatal period (Johnson et al., 2010; Kirkby and Feller, 2013; Rao et al., 2013; Renna et al., 2011). Here, we probed the maturation of the dendritic arbors of melanopsin ganglion cells during this developmental period in mice. We found that some melanopsin ganglion cells (mainly the M1-subtype) transiently extend their dendrites not only into the inner plexiform layer (where they receive synaptic inputs from bipolar and amacrine cells) but also into the outer plexiform layer, where in mature retina, rod and cone photoreceptors are thought to contact only bipolar and horizontal cells. Thus, some immature melanopsin ganglion cells are biplexiform. This feature is much less common although still present in the mature retina. It reaches peak incidence 8-12 days after birth, before the eyes open and bipolar cells are sufficiently mature to link rods and cones to ganglion cells. At this age, some outer dendrites of melanopsin ganglion cells lie in close apposition to the axon terminals of cone photoreceptors and express a postsynaptic marker of glutamatergic transmission, postsynaptic density-95 protein (PSD-95). These findings raise the possibility of direct, monosynaptic connections between cones and melanopsin ganglion cells in the early postnatal retina. We provide a detailed description of the developmental profile of these processes and consider their possible functional and evolutionary significance.
authors.affiliation: Department of Biology, University of Akron, 185 E. Mill St., Akron, Ohio, 44325-3908.
authors.forename: Jordan M
authors.initials: JM
authors.lastname: Renna
authors.affiliation: Department of Neuroscience, Brown University, 185 Meeting Street, Providence, Rhode Island, 02912.
authors.forename: Deepa K
authors.initials: DK
authors.lastname: Chellappa
authors.affiliation: Department of Biology, University of Akron, 185 E. Mill St., Akron, Ohio, 44325-3908.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Ross
authors.affiliation: Department of Cell and Developmental Biology, University of Colorado School of Medicine, 12801 E. 17th Ave, RC1 South 12120, Aurora, Colorado, 80045.
authors.forename: Maureen E
authors.initials: ME
authors.lastname: Stabio
authors.affiliation: Department of Neuroscience, Brown University, 185 Meeting Street, Providence, Rhode Island, 02912.
authors.forename: David M
authors.initials: DM
authors.lastname: Berson
mesh_terms: D025042:Amacrine Cells / Q000166:cytology / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D003712:Dendrites / Q000502:physiology; D046169:Dermoscopy; D007150:Immunohistochemistry; D008810:Mice, Inbred C57BL; D018408:Patch-Clamp Techniques; D012160:Retina / Q000166:cytology* / Q000254:growth & development* / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000166:cytology* / Q000502:physiology; D017299:Rod Opsins / Q000378:metabolism*; D000099210:Melanopsin
chemical_list: D002795:Choline O-Acetyltransferase; D017299:Rod Opsins; D000099210:Melanopsin
keywords: biplexiform; ganglion cell; intrinsically photosensitive ganglion cells; melanopsin; retina