title: Photoentrainment and pupillary light reflex are mediated by distinct populations of ipRGCs.
abstract: Intrinsically photosensitive retinal ganglion cells (ipRGCs) express the photopigment melanopsin and regulate a wide array of light-dependent physiological processes. Genetic ablation of ipRGCs eliminates circadian photoentrainment and severely disrupts the pupillary light reflex (PLR). Here we show that ipRGCs consist of distinct subpopulations that differentially express the Brn3b transcription factor, and can be functionally distinguished. Brn3b-negative M1 ipRGCs innervate the suprachiasmatic nucleus (SCN) of the hypothalamus, whereas Brn3b-positive ipRGCs innervate all other known brain targets, including the olivary pretectal nucleus. Consistent with these innervation patterns, selective ablation of Brn3b-positive ipRGCs severely disrupts the PLR, but does not impair circadian photoentrainment. Thus, we find that molecularly distinct subpopulations of M1 ipRGCs, which are morphologically and electrophysiologically similar, innervate different brain regions to execute specific light-induced functions.
authors.affiliation: Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: S-K
authors.initials: SK
authors.lastname: Chen
authors.forename: T C
authors.initials: TC
authors.lastname: Badea
authors.forename: S
authors.initials: S
authors.lastname: Hattar
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects*; D018398:Homeodomain Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D008959:Models, Neurological; D009847:Olivary Nucleus / Q000378:metabolism; D012025:Reflex, Pupillary / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects*; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects*; D017299:Rod Opsins / Q000235:genetics / Q000378:metabolism; D013493:Suprachiasmatic Nucleus / Q000378:metabolism; D050820:Transcription Factor Brn-3B / Q000172:deficiency / Q000378:metabolism; D000099210:Melanopsin
chemical_list: D018398:Homeodomain Proteins; D017299:Rod Opsins; D050820:Transcription Factor Brn-3B; D000099210:Melanopsin; C085559:Pou4f2 protein, mouse