title: A circannual clock drives expression of genes central for seasonal reproduction.
abstract: Animals living in temperate zones anticipate seasonal environmental changes to adapt their biological functions, especially reproduction and metabolism. Two main physiological mechanisms have evolved for this adaptation: intrinsic long-term timing mechanisms with an oscillating period of approximately 1 year, driven by a circannual clock [1], and synchronization of biological rhythms to the sidereal year using day length (photoperiod) [2]. In mammals, the pineal hormone melatonin relays photoperiodic information to the hypothalamus to control seasonal physiology through well-defined mechanisms [3-6]. In contrast, little is known about how the circannual clock drives endogenous changes in seasonal functions. The aim of this study was to determine whether genes involved in photoperiodic time measurement (TSHβ and Dio2) and central control of reproduction (Rfrp and Kiss1) display circannual rhythms in expression under constant conditions. Male European hamsters, deprived of seasonal time cues by pinealectomy and maintenance in constant photoperiod, were selected when expressing a subjective summer or subjective winter state in their circannual cycle of body weight, temperature, and testicular size. TSHβ expression in the pars tuberalis (PT) displayed a robust circannual variation with highest level in the subjective summer state, which was positively correlated with hypothalamic Dio2 and Rfrp expression. The negative sex steroid feedback was found to act specifically on arcuate Kiss1 expression. Our findings reveal TSH as a circannual output of the PT, which in turn regulates hypothalamic neurons controlling reproductive activity. Therefore, both the circannual and the melatonin signals converge on PT TSHβ expression to synchronize seasonal biological activity.
authors: Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, Université de Strasbourg, 67084 Strasbourg, France; School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, Scotland, UK.
authors: Cristina
authors: C
authors: Sáenz de Miera
authors: Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, Université de Strasbourg, 67084 Strasbourg, France.
authors: Stefanie
authors: S
authors: Monecke
authors: Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, Université de Strasbourg, 67084 Strasbourg, France.
authors: Julien
authors: J
authors: Bartzen-Sprauer
authors: Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, Université de Strasbourg, 67084 Strasbourg, France.
authors: Marie-Pierre
authors: MP
authors: Laran-Chich
authors: Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, Université de Strasbourg, 67084 Strasbourg, France.
authors: Paul
authors: P
authors: Pévet
authors: School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, Scotland, UK; Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economy, University of Tromsø, 9037 Tromsø, Norway.
authors: David G
authors: DG
authors: Hazlerigg
authors: Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, Université de Strasbourg, 67084 Strasbourg, France. Electronic address: simonneaux@inci-cnrs.unistra.fr.
authors: Valérie
authors: V
authors: Simonneaux
mesh_terms: D000220:Adaptation, Biological / Q000502:physiology*; D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D006224:Cricetinae / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D059648:Kisspeptins / Q000378:metabolism; D008297:Male; D009929:Organ Size / Q000502:physiology; D017440:Photoperiod; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D013737:Testis / Q000033:anatomy & histology; D037322:Thyrotropin, beta Subunit / Q000378:metabolism*
chemical_list: D059648:Kisspeptins; D037322:Thyrotropin, beta Subunit