title: Human skin keratinocytes, melanocytes, and fibroblasts contain distinct circadian clock machineries.
abstract: Skin acts as a barrier between the environment and internal organs and performs functions that are critical for the preservation of body homeostasis. In mammals, a complex network of circadian clocks and oscillators adapts physiology and behavior to environmental changes by generating circadian rhythms. These rhythms are induced in the central pacemaker and peripheral tissues by similar transcriptional-translational feedback loops involving clock genes. In this work, we investigated the presence of functional oscillators in the human skin by studying kinetics of clock gene expression in epidermal and dermal cells originating from the same donor and compared their characteristics. Primary cultures of fibroblasts, keratinocytes, and melanocytes were established from an abdominal biopsy and expression of clock genes following dexamethasone synchronization was assessed by qPCR. An original mathematical method was developed to analyze simultaneously up to nine clock genes. By fitting the oscillations to a common period, the phase relationships of the genes could be determined accurately. We thereby show the presence of functional circadian machinery in each cell type. These clockworks display specific periods and phase relationships between clock genes, suggesting regulatory mechanisms that are particular to each cell type. Taken together, our data demonstrate that skin has a complex circadian organization. Oscillators are present not only in fibroblasts but also in epidermal keratinocytes and melanocytes and are likely to act in coordination to drive rhythmic functions within the skin.
authors.affiliation: Department of Neurobiology of Rhythms, Institute of Cellular and Integrative Neurosciences, CNRS UPR, Strasbourg, France.
authors.forename: Cristina
authors.initials: C
authors.lastname: Sandu
authors.forename: Marc
authors.initials: M
authors.lastname: Dumas
authors.forename: André
authors.initials: A
authors.lastname: Malan
authors.forename: Diariétou
authors.initials: D
authors.lastname: Sambakhe
authors.forename: Clarisse
authors.initials: C
authors.lastname: Marteau
authors.forename: Carine
authors.initials: C
authors.lastname: Nizard
authors.forename: Sylvianne
authors.initials: S
authors.lastname: Schnebert
authors.forename: Eric
authors.initials: E
authors.lastname: Perrier
authors.forename: Etienne
authors.initials: E
authors.lastname: Challet
authors.forename: Paul
authors.initials: P
authors.lastname: Pévet
authors.forename: Marie-Paule
authors.initials: MP
authors.lastname: Felder-Schmittbuhl
mesh_terms: D056926:CLOCK Proteins / Q000235:genetics; D002478:Cells, Cultured; D057906:Circadian Clocks / Q000235:genetics*; D005347:Fibroblasts / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D015603:Keratinocytes / Q000502:physiology*; D008544:Melanocytes / Q000502:physiology*; D012867:Skin / Q000166:cytology*
chemical_list: D056926:CLOCK Proteins; C538943:CLOCK protein, human