title: Ectopic Expression of Mouse Melanopsin inDrosophilaPhotoreceptors Reveals Fast Response Kinetics and Persistent Dark Excitation.
abstract: The intrinsically photosensitive M1 retinal ganglion cells (ipRGC) initiate non-image-forming light-dependent activities and express the melanopsin (OPN4) photopigment. Several features of ipRGC photosensitivity are characteristic of fly photoreceptors. However, the light response kinetics of ipRGC is much slower due to unknown reasons. Here we used transgenicDrosophila, in which the mouse OPN4 replaced the native Rh1 photopigment ofDrosophilaR1-6 photoreceptors, resulting in deformed rhabdomeric structure. Immunocytochemistry revealed OPN4 expression at the base of the rhabdomeres, mainly at the rhabdomeral stalk. Measurements of the early receptor current, a linear manifestation of photopigment activation, indicated large expression of OPN4 in the plasma membrane. Comparing the early receptor current amplitude and action spectra between WT and the Opn4-expressingDrosophilafurther indicated that large quantities of a blue absorbing photopigment were expressed, having a dark stable blue intermediate state. Strikingly, the light-induced current of the Opn4-expressing fly photoreceptors was ∼40-fold faster than that of ipRGC. Furthermore, an intense white flash induced a small amplitude prolonged dark current composed of discrete unitary currents similar to theDrosophilasingle photon responses. The induction of prolonged dark currents by intense blue light could be suppressed by a following intense green light, suggesting induction and suppression of prolonged depolarizing afterpotential. This is the first demonstration of heterologous functional expression of mammalian OPN4 in the genetically emendableDrosophilaphotoreceptors. Moreover, the fast OPN4-activated ionic current ofDrosophilaphotoreceptors relative to that of mouse ipRGC, indicates that the slow light response of ipRGC does not arise from an intrinsic property of melanopsin.
authors.affiliation: From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and.
authors.forename: Bushra
authors.initials: B
authors.lastname: Yasin
authors.affiliation: From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and.
authors.forename: Elkana
authors.initials: E
authors.lastname: Kohn
authors.affiliation: From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Peters
authors.affiliation: From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and.
authors.forename: Rachel
authors.initials: R
authors.lastname: Zaguri
authors.affiliation: From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and.
authors.forename: Shirley
authors.initials: S
authors.lastname: Weiss
authors.affiliation: the Department of Biosensorics, Institute of Physiology, University of Hohenheim, 70599 Stuttgart, Germany.
authors.forename: Krystina
authors.initials: K
authors.lastname: Schopf
authors.affiliation: From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and.
authors.forename: Ben
authors.initials: B
authors.lastname: Katz
authors.affiliation: the Department of Biosensorics, Institute of Physiology, University of Hohenheim, 70599 Stuttgart, Germany.
authors.forename: Armin
authors.initials: A
authors.lastname: Huber
authors.affiliation: From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and baruchm@ekmd.huji.ac.il.
authors.forename: Baruch
authors.initials: B
authors.lastname: Minke
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D002462:Cell Membrane / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology; D003116:Color; D003624:Darkness; D004330:Drosophila; D000066630:Ectopic Gene Expression; D007150:Immunohistochemistry; D007700:Kinetics; D008027:Light; D051379:Mice; D017785:Photons; D010786:Photoreceptor Cells; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism*; D010858:Pigmentation; D017299:Rod Opsins / Q000378:metabolism*; D000099210:Melanopsin
chemical_list: D017299:Rod Opsins; D000099210:Melanopsin
keywords: Drosophila; Early Receptor Potential; Opn4; electrophysiology; gene expression; photoreceptor; rhodopsin; single photon response