Circadian Clock Genes and Photoperiodism: Comprehensive Analysis of Clock Gene Expression in the Mediobasal Hypothalamus, the Suprachiasmatic Nucleus, and the Pineal Gland of Japanese Quail under Various Light Schedules
Division of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan. Endocrinology
(Impact Factor: 4.5).
10/2003; 144(9):3742-8. DOI: 10.1210/en.2003-0435
In birds, the mediobasal hypothalamus (MBH) including the infundibular nucleus, inferior hypothalamic nucleus, and median eminence is considered to be an important center that controls the photoperiodic time measurement. Here we show expression patterns of circadian clock genes in the MBH, putative suprachiasmatic nucleus (SCN), and pineal gland, which constitute the circadian pacemaker under various light schedules. Although expression patterns of clock genes were different between long and short photoperiod in the SCN and pineal gland, the results were not consistent with those under night interruption schedule, which causes testicular growth. These results indicate that different expression patterns of the circadian clock genes in the SCN and pineal gland are not an absolute requirement for encoding and decoding of seasonal information. In contrast, expression patterns of clock genes in the MBH were stable under various light conditions, which enables animals to keep a steady-state photoinducible phase.
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- "tion - based oscillatory loop that serves as an internal bi - ological clock . The oscillatory loop involves BMAL1 , Clock , and Period ( PER ; Reppert and Weaver , 2002 ) . Expression of BMAL1 in chicken is modulated by the duration of light , and the expression patterns of the clock genes are affected by photoperiod in the SCN and pineal gland ( Yasuo et al . , 2003 ) . Luteinizing hormone acts additively with Clock / BMAL1 to enhance StAR gene expression and stimulates Per2 gene expression in the presence of Clock / BMAL1 . This latter observation is consistent with control of the timing of ovulation by the circadian rhythm ( Nakao et al . , 2007 ) . This background information led us to suspect t"
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ABSTRACT: We examined the effect of monochromatic light supplementation on pigeon reproductive performance and on the expression of the brain and muscle aryl hydrocarbon receptor nuclear translocator-like (BMAL1) protein in the hypothalamic-pituitary-gonadal (HPG) axis. White King pigeons were selected randomly from 4 lofts (510 pairs/loft) with 3 subgroups/loft. The lofts were exposed to one of 4 light treatments for 3 months administered in the morning and evening as follows: blue light (480 nm), green light (540 nm), red light (660 nm), and control white light. The laying rate, fertility rate, and birth rate were recorded. After 3 months, 48 birds were selected randomly from the 4 lofts (6 females and 6 males from each loft), sacrificed, and the HPG axis was isolated. Following exposure to red light, laying rate was greater than the control group (P = 0.013), but there were no significant differences in the fertility rate (P = 0.41) or birth rate (P = 0.66). Expression of BMAL1 in the hypothalamus was unaffected by the light regime but was greater in the pituitary of females exposed to red light (P = 0.046) and in the pituitary of males exposed to the control white light (P = 0.059). The change in BMAL1 expression in the pituitary of females was negatively correlated with birth rate in monochromatic light (P = 0.021). We suggest that reproductive performance of pigeons is improved by light supplementation in the morning and evening. According to these data, 100 pigeons exposed to red light could lay 26.68 more eggs per month than the control group. Additionally, BMAL1 expression in the HPG axis of pigeons exposed to monochromatic light correlated with birth rate.
© 2015 Poultry Science Association Inc.
Available from: Wayne I L Davies
- "Changes in photoperiod have also been shown to alter the pattern of Fos expression within the MBH and ME, reinforcing roles for these regions in transducing photoperiod into an endocrine response (Meddle and Follett, 1997). The expression of multiple clock genes within both the MBH and the suprachiasmatic nuclei (SCN) has suggested a location within the hypothalamus for the photoperiodic clock (Yasuo et al., 2003). In parallel with these findings, It has been known for many years that thyroid hormones play a critically important role in regulating the avian photoperiodic response (Follett and Nicholls, 1985) but a series of recent studies by Yoshimura and colleagues have placed these observations into a physiological context suggesting that long daylengths regulate thyroid hormone metabolism within the MBH itself (Nakao et al., 2008; Yoshimura et al., 2003). "
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ABSTRACT: Extraretinal photoreceptors located within the medio-basal hypothalamus regulate the photoperiodic control of seasonal reproduction in birds. An action spectrum for this response describes an opsin photopigment with a λmax of ∼492nm. Beyond this however, the specific identity of the photopigment remains unresolved. Several candidates have emerged including rod-opsin; melanopsin (OPN4); neuropsin (OPN5); and vertebrate ancient (VA) opsin. These contenders are evaluated against key criteria used routinely in photobiology to link orphan photopigments to specific biological responses. To date, only VA opsin can easily satisfy all criteria and we propose that this photopigment represents the prime candidate for encoding daylength and driving seasonal breeding in birds. We also show that VA opsin is co-expressed with both gonadotropin-releasing hormone (GnRH) and arginine-vasotocin (AVT) neurons. These new data suggest that GnRH and AVT neurosecretory pathways are endogenously photosensitive and that our current understanding of how these systems are regulated will require substantial revision.
Copyright © 2014. Published by Elsevier Inc.
Available from: Paul Pevet
- "Of note, daily variations in this gene have been highlighted in the SCN of a diurnal non-human primate, the capuchin monkey (Valenzuela et al., 2008). Furthermore, in other classes of vertebrates, Clock oscillations have also been found in diurnal birds such as the quail (Yasuo et al., 2003). Therefore, this comparative phylogenetic survey gives clues to our assertion. "
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ABSTRACT: A major challenge in the field of circadian rhythms is to understand the neural mechanisms controlling the oppositely phased temporal organization of physiology and behaviour between night- and day-active animals. Most identified components of the master clock in the suprachiasmatic nuclei (SCN), called circadian genes, display similar oscillations according to the time of day, independent of the temporal niche. This has led to the predominant view that the switch between night- and day-active animals occurs downstream of the master clock, likely also involving differential feedback of behavioral cues onto the SCN. The Barbary striped grass mouse, Lemniscomys barbarus is known as a day-active Muridae. Here we show that this rodent, when housed in constant darkness, displays a temporal rhythmicity of metabolism matching its diurnal behaviour (i.e., high levels of plasma leptin and hepatic glycogen during subjective midday and dusk, respectively). Regarding clockwork in their SCN, these mice show peaks in the mRNA profiles of the circadian gene Period1 (Per1) and the clock-controlled gene Vasopressin (Avp), which occur during the middle and late subjective day, respectively, in accordance with many observations in both diurnal and nocturnal species. Strikingly, expression of the circadian gene Clock in the SCN of the Barbary striped grass mouse was not constitutive as in nocturnal rodents, but it was rhythmic. As this is also the case for the other diurnal species investigated in the literature (sheep, marmoset, and quail), a hypothesis is that the transcriptional control of Clock within the SCN participates in the mechanisms underlying diurnality and noctumality.
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