title: Regulation of melanopsins and Per1 by α -MSH and melatonin in photosensitive Xenopus laevis melanophores.
abstract: α-MSH and light exert a dispersing effect on pigment granules of Xenopus laevis melanophores; however, the intracellular signaling pathways are different. Melatonin, a hormone that functions as an internal signal of darkness for the organism, has opposite effects, aggregating the melanin granules. Because light functions as an important synchronizing signal for circadian rhythms, we further investigated the effects of both hormones on genes related to the circadian system, namely, Per1 (one of the clock genes) and the melanopsins, Opn4x and Opn4m (photopigments). Per1 showed temporal oscillations, regardless of the presence of melatonin or α-MSH, which slightly inhibited its expression. Melatonin effects on melanopsins depend on the time of application: if applied in the photophase it dramatically decreased Opn4x and Opn4m expressions, and abolished their temporal oscillations, opposite to α-MSH, which increased the melanopsins' expressions. Our results demonstrate that unlike what has been reported for other peripheral clocks and cultured cells, medium changes or hormones do not play a major role in synchronizing the Xenopus melanophore population. This difference is probably due to the fact that X. laevis melanophores possess functional photopigments (melanopsins) that enable these cells to primarily respond to light, which triggers melanin dispersion and modulates gene expression.
authors: Department of Physiology, Institute of Biosciences, University of São Paulo, R. do Matão, Travessera 14, No. 101, 05508-900 São Paulo, SP, Brazil.
authors: Maria Nathália de Carvalho Magalhães
authors: MN
authors: Moraes
authors: Department of Physiology, Institute of Biosciences, University of São Paulo, R. do Matão, Travessera 14, No. 101, 05508-900 São Paulo, SP, Brazil.
authors: Luciane Rogéria
authors: LR
authors: dos Santos
authors: Department of Physiology, Institute of Biosciences, University of São Paulo, R. do Matão, Travessera 14, No. 101, 05508-900 São Paulo, SP, Brazil.
authors: Nathana
authors: 0000-0002-3196-7797
authors: N
authors: Mezzalira
authors: Department of Physiology, Institute of Biological Sciences, Federal University of Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil.
authors: Maristela Oliveira
authors: MO
authors: Poletini
authors: Department of Physiology, Institute of Biosciences, University of São Paulo, R. do Matão, Travessera 14, No. 101, 05508-900 São Paulo, SP, Brazil.
authors: Ana Maria de Lauro
authors: AM
authors: Castrucci
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002940:Circadian Rhythm / Q000235:genetics; D005786:Gene Expression Regulation; D008027:Light; D008547:Melanophores / Q000378:metabolism; D008550:Melatonin / Q000235:genetics / Q000378:metabolism*; D056950:Period Circadian Proteins / Q000235:genetics / Q000378:metabolism*; D010860:Pigments, Biological / Q000235:genetics / Q000378:metabolism; D017299:Rod Opsins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis; D000521:alpha-MSH / Q000096:biosynthesis* / Q000235:genetics; D000099210:Melanopsin
chemical_list: D008550:Melatonin; D056950:Period Circadian Proteins; D010860:Pigments, Biological; D017299:Rod Opsins; D029867:Xenopus Proteins; D000521:alpha-MSH; D000099210:Melanopsin; C539025:Per1 protein, Xenopus