Research Achievements - Original paper -
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The uterus sustains stable biological clock during pregnancy.
Shizuko Akiyama, Hidenobu Ohta, Shimpei Watanabe, Takahiro Moriya, Aya Hariu, Norimichi Nakahata, Hiroshi Chisaka, Tadashi Matsuda, Yoshitaka Kimura, Shigeru Tsuchiya, Hajime Tei, Kunihiro Okamura, Nobuo Yaegashi
The Tohoku journal of experimental medicine 221 ( 4 ) 287 - 98 2010.08
Research paper (journal)
Maternal circadian information has been reported to play an important role in fetal physiology and development. Hormones and nutrition have been mainly investigated as circadian cues from mother to fetus. However, the influences of circadian properties of the pregnant reproductive organs on fetuses have not been fully investigated. To gain an insight on the circadian functions of the reproductive organs, we examined molecular clocks in the pregnant rat uterus and placenta. By using a Period1-luciferase (Per1-luc) rat, whose tissues express luciferase corresponding to activation of Period1, a "key clock gene", we examined the uterus clock during non-pregnancy, on embryonic day 12 (E12), and on E22 (the end of pregnancy) in a light-dark (LD) cycle and constant darkness (DD). By in situ hybridization we further explored Per1 mRNA rhythms in the placenta on E12 and E22. The uterus in vitro showed clear circadian Per1-luc rhythms both in and out of pregnancy, having peaks at around the time corresponding to dusk in LD. Likewise, in DD, the uterus in vitro had the same Per1-luc rhythms. The decidua in LD showed circadian Per1 mRNA rhythms, peaking during night 6 h after dusk, while the decidua in DD showed the same Per1 mRNA rhythms only on E22. In contrast, the labyrinth showed no circadian Per1 mRNA rhythms in LD or DD during pregnancy. These results suggest that the uterus and decidua, a maternally-originated tissue of the placenta, but not the labyrinth, a fetus-originated tissue of the placenta, can provide the fetus with circadian information.
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Maternal Feeding Controls Fetal Biological Clock
Hidenobu Ohta, Shanhai Xu, Takahiro Moriya, Masayuki Iigo, Tatsuya Watanabe, Norimichi Nakahata, Hiroshi Chisaka, Takushi Hanita, Tadashi Matsuda, Toshihiro Ohura, Yoshitaka Kimura, Nobuo Yaegashi, Shigeru Tsuchiya, Hajime Tei, Kunihiro Okamura
PLOS ONE ( PUBLIC LIBRARY SCIENCE ) 3 ( 7 ) e2601 2008.07
Research paper (journal)
Background: It is widely accepted that circadian physiological rhythms of the fetus are affected by oscillators in the maternal brain that are coupled to the environmental light-dark (LD) cycle.
Methodology/Principal Findings: To study the link between fetal and maternal biological clocks, we investigated the effects of cycles of maternal food availability on the rhythms of Per1 gene expression in the fetal suprachiasmatic nucleus (SCN) and liver using a transgenic rat model whose tissues express luciferase in vitro. Although the maternal SCN remained phase-locked to the LD cycle, maternal restricted feeding phase-advanced the fetal SCN and liver by 5 and 7 hours respectively within the 22-day pregnancy.
Conclusions/Significance: Our results demonstrate that maternal feeding entrains the fetal SCN and liver independently of both the maternal SCN and the LD cycle. This indicates that maternal-feeding signals can be more influential for the fetal SCN and particular organ oscillators than hormonal signals controlled by the maternal SCN, suggesting the importance of a regular maternal feeding schedule for appropriate fetal molecular clockwork during pregnancy. -
Constant light disrupts the developing mouse biological clock
Hidenobu Ohta, Amanda C. Mitchell, Douglas G. McMahon
PEDIATRIC RESEARCH ( INT PEDIATRIC RESEARCH FOUNDATION, INC ) 60 ( 3 ) 304 - 308 2006.09
Research paper (journal)
The central biological clock of the brain, contained within the suprachiasmatic nuclei (SCN) of mammals, orchestrates an orderly "internal day" of physiology and behavior. The developing biological clock begins to respond to light at an early stage and a particular concern in humans is whether light exposure has disruptive effects on the developing biological clock of infants exposed to constant lighting conditions in neonatal intensive care units (NICUs). Worldwide, eighteen million, or 14%, of newborns estimated to be of low birth weight, are exposed to artificial lighting environments in hospital nurseries annually. Here, we have tested whether constant light (LL) exposure disrupts the developing biological clock of mice, using a circadian reporter transgenic mouse model in which the organization of the central biological clock can be assayed by real-time gene expression imaging. We now find that LL has both acute and long-term disruptive effects on developing biological clocks and that cyclic lighting conditions are critical for developing circadian clocks to coordinate their molecular circadian mechanisms. This suggests that, from the perspective of developing circadian organization in humans, cyclic light conditions in NICUs are likely to be most appropriate for infants.
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Daily rhythmicity of large-conductance Ca2+-activated K+ currents in suprachiasmatic nucleus neurons
GR Pitts, H Ohta, DG McMahon
BRAIN RESEARCH ( ELSEVIER SCIENCE BV ) 1071 ( 1 ) 54 - 62 2006.02
Research paper (journal)
Neurons within the suprachiasmatic nucleus (SCN) comprise the master circadian pacemaker in mammals. These neurons exhibit circadian rhythms in spontaneous action potential frequency and in the transcription of core circadian clock genes, including Period1 (Per1). Targeted electrophysiological recordings from SCN neurons marked with a green fluorescent protein (GFP) reporter of Per1 gene transcription have previously indicated that K+ currents are critically involved in the expression of neurophysiological rhythmicity. The present study examined the role of large conductance, Ca2+-activated K+ channels (BK) in the daily rhythmicity of mouse SCN neurons. BK-mediated currents were examined in Per1::GFP neurons under voltage clamp using iberiotoxin, a specific BK channel blocker. BK current was a greater proportion of whole-cell outward currents during the night than during the day. Analysis of iberiotoxin difference currents also demonstrated that BK current amplitude and density were greater during the night and that the day/night difference in steady state amplitude was not due to altered inactivation. Single cell RT-PCR demonstrated the presence of the BK channel transcript, KCNMA1, in Per1-expressing neurons. In situ hybridization analysis further showed that KCNMA1 mRNA was rhythmically expressed in the SCN under light:dark (LD) conditions, peaking during the middle of the night phase. Acute inhibition of BK currents blunted the circadian rhythm SCN neuron spike frequency. These results establish that BK channel function is elevated at night, thus altering SCN neuron activity. (C) 2005 Elsevier B.V. All rights reserved.
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Constant light desynchronizes mammalian clock neurons
H Ohta, S Yamazaki, DG McMahon
NATURE NEUROSCIENCE ( NATURE PUBLISHING GROUP ) 8 ( 3 ) 267 - 269 2005.03
Research paper (journal)
Circadian organization can be disrupted by constant light, resulting in behavioral arrhythmicity or 'splitting' of rhythms of activity and rest. By imaging molecular rhythms of individual clock neurons in explanted mouse clock nuclei, we now find that constant light desynchronizes clock neurons but does not compromise their ability to generate circadian rhythms. Cellular synchrony within clock nuclei is disrupted during arrhythmicity, whereas neurons in the left and right clock nuclei cycle in antiphase during 'splitting.'
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Characterization of genetically labeled catecholamine neurons in the mouse retina
DQ Zhang, JF Stone, TR Zhou, H Ohta, DG McMahon
NEUROREPORT ( LIPPINCOTT WILLIAMS & WILKINS ) 15 ( 11 ) 1761 - 1765 2004.08
Research paper (journal)
Mouse neurons were labeled transgenically with red fluorescent protein (RFP) driven by the tyrosine hydroxylase (TH) promoter and observed in living retinas and brain slices. Two types of retinal amacrine cells expressed TH::RFP. One type had large cell bodies, processes that ramified in SI of the inner plaxiform layer (IPL) and were TH immunoreactive, identifying them as dopaminergic neurons. A second type had smaller somas, ramified in S3 and lacked TH. Dopaminergic cells had large dendritic fields and exceptionally long axon-like processes, whereas type 2 cells were more compact. Neither cell type exhibited tracer coupling. Thus, murine retinal dopaminergic neurons exhibit functional anatomy similar to their primate counterparts and TH::RFP mice are useful for in situ characterization of catecholaminergic neurons.
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Periodic absence of nursing mothers phase-shifts circadian rhythms of clock genes in the suprachiasmatic nucleus of rat pups
H Ohta, S Honma, H Abe, K Honma
EUROPEAN JOURNAL OF NEUROSCIENCE ( BLACKWELL PUBLISHING LTD ) 17 ( 8 ) 1628 - 1634 2003.04
Research paper (journal)
Effects of absence of nursing mothers on the circadian pacemaker of their offspring were examined by measuring clock genes, the rat Per1 (rPer1) and rPer2 expression rhythms in the pup suprachiasmatic nuclei (SCN). Neonate rats born to mothers kept under a 12-h light : 12-h dark cycle (LD) were blinded immediately after birth and exposed to periodic maternal deprivation where pups were deprived of their mothers during the light phase of 12-h for the first week of life. At postnatal day 6, the periodic maternal deprivation completely phase- reversed the circadian rhythms in expression of the clock genes in the pup SCN and in spontaneous locomotor activity after the pups were weaned at postnatal day 21. The periodic maternal absence also altered the patterns of stress-related gene expressions such as corticotropine-releasing hormone, arginine vasopressin, and glucocorticoid receptor in particular brain areas of the mother-deprived pups at P6. These findings indicate that periodic absence of the nursing mother in the first week of life produces a resetting effect on the neonatal circadian clock and induces stress responses in the hypothalamus-pituitary-adrenal axis.
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Effects of nursing mothers on rPer1 and rPer2 circadian expressions in the neonatal rat suprachiasmatic nuclei vary with developmental stage
Hidenobu Ohta, Sato Honma, Hiroshi Abe, Ken-Ichi Honma
European Journal of Neuroscience ( 12 ) 15 ( 12 ) 1953 - 1960 2002
Research paper (journal)
The ability of nursing mothers to entrain the circadian pacemaker of rat pups was examined by measuring the rat Per1 (rPer1) and rPer2 expression levels in the suprachiasmatic nuclei (SCN). Newborn rats from mothers under a light-dark cycle (LD) were blinded immediately after birth and reared by foster mothers under either LD (LD blind pups) or reversed light-dark cycle (DL
DL blind pups). At postnatal day (P)6, small but significant phase differences were observed in the circadian gene expression rhythms of the SCN not only between the blind and sighted pups, but also between the two groups of blind pups, indicating the involvement of both free-running and maternal influence in phase-resetting the circadian rhythms of blind pups. However, from P6 to P13 the circadian rhythms of both LD and DL blind pups showed phase delays of similar extent, which suggests that the influence of nursing mothers was lost. From P13 to P20 (the day of weaning), the rPer1 and rPer2 rhythms phase-shifted in a different manner, the rPer2 rhythm being related more closely to the behavioural rhythm than was the rPer1. This finding suggests a differential influence of mothers on the rPer1 and rPer2 rhythms in the third week of life. It is concluded that the ability of nursing mothers to entrain pup circadian oscillation depends on the developmental stage. -
Continuous measurement of targeted promoter activity by a secreted bioluminescence reporter, Vargula hilgendorfii luciferase
Y Tanahashi, Y Ohmiya, S Honma, Y Katsuno, H Ohta, H Nakamura, K Honma
ANALYTICAL BIOCHEMISTRY ( ACADEMIC PRESS INC ) 289 ( 2 ) 260 - 266 2001.02
Research paper (journal)
The promoter activity of growth hormone (GH) was continuously monitored in rat pituitary adenoma cells (GH3) by a secreted bioluminescence reporter, Vargula hilgendorfii (Vh) luciferase. The sensitivity of the reporter was approximately 60-times higher than that of the firefly luciferase, GH3 cells were transfected with a plasmid containing a DNA sequence of the GH promoter (1.8 kb) and a full length of the Vh luciferase cDNA. Using the stable transformants, the Vh luciferase activity was monitored in the plate culture through the bioluminescence of Vh luciferase secreted into the culture medium. The reporter activity was well correlated with GH mRNA as well, as GH when the GH promoter activity was activated by thyroid hormone. To develop a continuous monitoring system of the promoter, the reporter activity was sequentially measured in the perfusion system. When the promoter activity of the stable transformants was suppressed by a transcription inhibitor, the reporter activity and GH in the perfusate were simultaneously decreased. The Vh luciferase reporter is a sensitive and convenient tool for continuous and prolonged measurement of promoter activity in living cell culture systems. (C) 2001 Academic Press.
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The observation of an ultradian rhythm of heart rate in low birth weight infants
H Ohta, K Cho, Y Matsumoto, T Matsuda, J Ohyu, S Fujimoto, K Honma
BIOLOGICAL RHYTHM RESEARCH ( TAYLOR & FRANCIS LTD ) 30 ( 5 ) 545 - 554 1999.12
Research paper (journal)
The relationship between ultradian rhythm of heart rate and schedules of body contact or feeding was studied in five low birth weight infants of conceptional ages of 34-36 weeks. The differential contribution of body contact and feeding to the formation of the ultradian rhythm of heart rate was evaluated by applying two different schedules of two- and three-hour periods for feeding with a single schedule of three hours for body contact during an observation period of seven days. A chi-square periodogram was used to calculate the period of ultradian rhythm. As a result, a three-hour ultradian rhythm of heart rates was detected in all subjects, which seems to correspond to either schedule of body contact or of feeding. However, no clear changes in the ultradian rhythm of heart rate were observed corresponding to changes in feeding schedules. The ultradian rhythm of heart: rate seems to correspond more to body contact than to feeding.
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Toriello-Carey syndrome with endocardial fibroelastosis
H Ohta, M Masuno, J Kimura, K Imaizumi, Y Kuroki, S Yasui, N Aida, Y Tanaka
AMERICAN JOURNAL OF MEDICAL GENETICS ( WILEY-LISS ) 87 ( 3 ) 271 - 272 1999.11
Research paper (journal)