title: Two light-activated neuroendocrine circuits arising in the eye trigger physiological and morphological pigmentation.
abstract: Two biological processes regulate light-induced skin colour change. A fast 'physiological pigmentation change' (i.e. circadian variations or camouflage) involves alterations in the distribution of pigment containing granules in the cytoplasm of chromatophores, while a slower 'morphological pigmentation change' (i.e. seasonal variations) entails changes in the number of pigment cells or pigment type. Although linked processes, the neuroendocrine coordination triggering each response remains largely obscure. By evaluating both events in Xenopus laevis embryos, we show that morphological pigmentation initiates by inhibiting the activity of the classical retinal ganglion cells. Morphological pigmentation is always accompanied by physiological pigmentation, and a melatonin receptor antagonist prevents both responses. Physiological pigmentation also initiates in the eye, but with repression of melanopsin-expressing retinal ganglion cell activity that leads to secretion of alpha-melanocyte-stimulating hormone (α-MSH). Our findings suggest a model in which eye photoperception links physiological and morphological pigmentation by altering α-MSH and melatonin production, respectively.
authors.affiliation: Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada.
authors.forename: Gabriel E
authors.initials: GE
authors.lastname: Bertolesi
authors.affiliation: Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada.
authors.forename: Carrie L
authors.initials: CL
authors.lastname: Hehr
authors.affiliation: Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada.
authors.forename: Hayden
authors.initials: H
authors.lastname: Munn
authors.affiliation: Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: McFarlane
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000503:physiopathology* / Q000528:radiation effects; D005123:Eye / Q000166:cytology / Q000503:physiopathology* / Q000528:radiation effects; D005260:Female; D008027:Light; D008550:Melatonin / Q000378:metabolism; D009490:Neurosecretory Systems / Q000503:physiopathology* / Q000528:radiation effects; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000528:radiation effects; D012880:Skin Pigmentation / Q000502:physiology*; D029867:Xenopus Proteins / Q000378:metabolism; D014982:Xenopus laevis / Q000502:physiology*; D000521:alpha-MSH / Q000378:metabolism
chemical_list: D029867:Xenopus Proteins; D000521:alpha-MSH; D008550:Melatonin
keywords: 
  Xenopus
  ; alpha-melanocyte-stimulating hormone; intrinsically photosensitive retinal ganglion cell; melatonin; retina