title: From blue light to clock genes in zebrafish ZEM-2S cells.
abstract: Melanopsin has been implicated in the mammalian photoentrainment by blue light. This photopigment, which maximally absorbs light at wavelengths between 470 and 480 nm depending on the species, is found in the retina of all classes of vertebrates so far studied. In mammals, melanopsin activation triggers a signaling pathway which resets the circadian clock in the suprachiasmatic nucleus (SCN). Unlike mammals, Drosophila melanogaster and Danio rerio do not rely only on their eyes to perceive light, in fact their whole body may be capable of detecting light and entraining their circadian clock. Melanopsin, teleost multiple tissue (tmt) opsin and others such as neuropsin and va-opsin, are found in the peripheral tissues of Danio rerio, however, there are limited data concerning the photopigment/s or the signaling pathway/s directly involved in light detection. Here, we demonstrate that melanopsin is a strong candidate to mediate synchronization of zebrafish cells. The deduced amino acid sequence of melanopsin, although being a vertebrate opsin, is more similar to invertebrate than vertebrate photopigments, and melanopsin photostimulation triggers the phosphoinositide pathway through activation of a G(q/11)-type G protein. We stimulated cultured ZEM-2S cells with blue light at wavelengths consistent with melanopsin maximal absorption, and evaluated the time course expression of per1b, cry1b, per2 and cry1a. Using quantitative PCR, we showed that blue light is capable of slightly modulating per1b and cry1b genes, and drastically increasing per2 and cry1a expression. Pharmacological assays indicated that per2 and cry1a responses to blue light are evoked through the activation of the phosphoinositide pathway, which crosstalks with nitric oxide (NO) and mitogen activated protein MAP kinase (MAPK) to activate the clock genes. Our results suggest that melanopsin may be important in mediating the photoresponse in Danio rerio ZEM-2S cells, and provide new insights about the modulation of clock genes in peripheral clocks.
authors.affiliation: Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil.
authors.forename: Bruno C R
authors.initials: BC
authors.lastname: Ramos
authors.affiliation: Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil.
authors.forename: Maria Nathália C M
authors.initials: MN
authors.lastname: Moraes
authors.affiliation: Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil; Department of Physiology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Maristela O
authors.initials: MO
authors.lastname: Poletini
authors.affiliation: Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil.
authors.forename: Leonardo H R G
authors.initials: LH
authors.lastname: Lima
authors.affiliation: Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil.
authors.forename: Ana Maria L
authors.initials: AM
authors.lastname: Castrucci
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D057906:Circadian Clocks / Q000235:genetics*; D056931:Cryptochromes / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D008027:Light; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009569:Nitric Oxide / Q000378:metabolism; D056950:Period Circadian Proteins / Q000235:genetics / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010775:Photic Stimulation; D012160:Retina / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D017299:Rod Opsins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000378:metabolism; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism; D000099210:Melanopsin
chemical_list: D056931:Cryptochromes; D005136:Eye Proteins; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020928:Mitogen-Activated Protein Kinases; D009569:Nitric Oxide; D056950:Period Circadian Proteins; D010716:Phosphatidylinositols; D017299:Rod Opsins; D029961:Zebrafish Proteins; D000099210:Melanopsin; C466244:cry1a protein, zebrafish; C539027:per1b protein, zebrafish; C498846:per2 protein, zebrafish