セミナー

Last updated on 16 November, 2014.

セミナー

第1151回生物科学セミナー　(by Dr. Tomoko Yoshikawa) 2017年3月22日（水）
第1113回生物科学セミナー　(by Dr. Mario E. Guido) 2016年9月23日（金）
第1112回生物科学セミナー　(by Dr. Qing-Jun Meng) 2016年9月23日（金）
第1099回生物科学セミナー　(by Dr. Carl Hirschie Johnson) 2016年6月3日（火）
第1017回生物科学セミナー　(by Dr. Jürgen A. Ripperger) 2014年11月28日（金）
第995回生物科学セミナー　(by Dr. Satchidananda Panda) 2014年8月1日（金）
第987回生物科学セミナー　(by Dr. Kazuhiro Yagita) 2014年4月18日（金）
東京大学大学院理学系研究科生物化学専攻セミナー　(by Dr. Abdelhalim Azzi) 2014年3月31日（月）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. Trevor D. Lamb) 2011年7月25日（月）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. Masao Doi) 2011年7月6日（水）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. Tomoko Obara) 2010年12月25日（月）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. Kyungjin Kim) 2010年12月13日（月）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. David Whitmore) 2010年11月8日（月）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. Samer Hattar) 2010年6月4日（金）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. Takaoki Kasahara) 2010年6月4日（金）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. Daniel R. Storm) 2009年9月14日（月）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. David C. Klein) 2009年6月1日（月）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. Sato Honma) 2009年4月11日（土）
第110回平成21年春季　東京大学公開講座　2009年4月4日（土）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. Steven A. Brown) 2009年3月6日（金）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. Urs Albrecht) 2008年11月13日（火）
東京大学グローバルCOE『統合生命学』特別セミナー (by Dr. Paul E. Hardin) 2008年7月15日（火）

その他のセミナー

 第1151回生物科学セミナー
演者：吉川　朋子　博士
近畿大学医学部解剖学教室
演題：マウス視交叉上核には複数の概日振動体が存在するーその局在と機能
日時：平成29年3月22日（水）13：30〜15：00
視交叉上核(SCN)に存在する概日時計は、外界の光周期の変化に応答し、動物の行動や生理機能の季節応答を制御する。夜行性げっ歯類の行動リズムを調べた研究から、行動の概日リズムは、2つの概日振動体によって制御されるという「2振動体仮説」が古くから提唱されている 1。すなわち、活動の開始を制御する Evening(E)振動体、活動の終了を制御する Morning(M)振動体の2つが存在し、それらの位相関係により動物の活動期の位相と長さが決められると考えられている。しかし、E および M 振動体の存在は仮説のまま、その実態は明らかにされていなかった。近年、概日時計に関わる時計遺伝子の発現リズムをルシフェラーゼ発光によりイメージングし、概日時計の挙動を細胞レベルで追跡する技術が大きく進歩した。この技術を利用したマウス SCN の解析により、E および M 振動体は SCN 内で吻側と尾側に分かれて局在することが明らかになった2。さらに詳細な局在を明らかにするため、我々は SCN の水平断スライスの発光リズムをピクセルレベルで統計的に解析する方法を確立した。その結果、SCN を4つの振動領域に分けることができた。本セミナーでは、この4つの振動領域の局在と機能について紹介したい。参考文献
(1) Pittendrigh and Daan, J. Comp. Physiol. A 106, 333-355 (1976) (2) Inagaki et al., PNAS 104:7664-7669 (2007)

世話人：理学系研究科　深田吉孝

 第1113回生物科学セミナー
演者：Mario E. Guido
Universidad Nacional de Córdoba, Argentina
演題：Novel Inner Retinal Photoreceptors in Non-mammalian Vertebrates
日時：平成28年9月23日（金）16：30〜18：00
場所：東京大学理学部3号館3階327号室

The vertebrate retina contains three different types of photoreceptors: the visual photoreceptors cones and rods, and the intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing the photopigment melanopsin (Opn4) that converged through evolution to regulate visual and non-image forming tasks (Valdez et al 2009, 2013; Diaz et al 2015). In the chicken, there are two Opn4 genes: Opn4mand Opn4x, the mammalian and Xenopus orthologs respectively. We have previously shown that the chicken retina expressed both proteins with Opn4m confined to the GC layerand Opn4x expressed in the GC layer at first and in horizontal cells (HCs) at later developmental stages (Verra et al. 2011). Embryonic RGC primary cultures expressing both Opn4s respond to light through a photocascade involving phospholipase C activation and calcium mobilization (Contin et al 2006, 2010). Here, we further characterize primary cultures of both Opn4x (+)populations of inner retinal cells (RGCs and HCs) and investigate their intrinsic photosensitivity as well as the visual cycle. For this,we obtained highly enriched Opn4x (+) cells by a chemical gradient (Morera et al 2012) and immunopanning, and assessed positive light responses by calcium fluorescence imaging as compared with dark controls.The expression of different circadian markers: clock genes Bmal1, Clock, Per2 and Cry1,and the key melatonin synthesizing enzyme: arylalkylamine N-acetyltransferase, and non-visual photocascade components: G protein qandOpn4xappears very early in development. Positive light responsiveness were observed in both primary cultures fed exogenous all-trans retinal (atRal) as compared with dark controls. Moreover, RGCs were able to isomerize atRal into 11cRal in the presence of light and to further metabolize it to all-trans retinol and all-trans retinyl palmitate (Diaz et al 2016). Results support the idea of a light dependent mechanism for chromophore regeneration in addition to bistability and that non-visual Opn4 photoreceptors and endogenous clocks converge all together in these inner retinal cells inwhich ipRGCs and HCs acting as non-classical photoreceptors may cooperate to detect light that regulates diverse non-visual functions.

世話人：理学系研究科　深田吉孝

 第1112回生物科学セミナー
演者：Qing-Jun Meng
University of Manchester
演題：Understanding circadian rhythms in the musculoskeletal system towards therapies for osteoarthritis and low back pain
日時：平成28年9月23日（金）10：00〜11：30
場所：東京大学理学部3号館3階327号室

Osteoarthritis (OA) is the most prevalent joint disease, causing severe pain, deformity and a loss of mobility. Low back pain (LBP), frequently associated with degeneration of the intervertebral disc (IVD), is the No.1 cause of Years Lived with Disability, with over 80% of the population predicted to experience back pain within their lifetime. Age is a major risk factor for both skeletal conditions. However, the reasons why susceptibility to these conditions increases with age are poorly understood. Consequently, current treatments are limited focusing solely on symptomatic pain relief rather than correcting the underlying pathogenesis and aberrant cell biology. The circadian (24 hourly) clocks in the brain and periphery direct key aspects of physiology through rhythmic control of tissue-specific sets of downstream genes. Symptoms of both conditions are known to show time-of-day effect, suggesting a possible involvement of the clock mechanisms. Work from our group focuses on the roles of circadian clocks in the articular cartilage and IVD. We show that the daily rhythm in these tissues becomes dampened and out-of phase during ageing. Further, our data identify circadian clock disruption in cartilage and IVD as a new target of inflammation. Moreover, we show that mice with targeted knockout of an essential clock gene (BMAL1) in chondrocytes and disc cells have profound, yet tissue-specific degeneration in the articular cartilage and IVD. These findings implicate the local skeletal clock as a key regulatiory mechanism for tissue homeostasis.This new avenue of research holde potential to better understand, and eventually treat these debilitating conditions. In this seminar, I will summarize our key findings on skeletal clocks and their potential implications in health and disease of the joint/spine.

世話人：理学系研究科　深田吉孝

 第1099回生物科学セミナー
演者：Carl Hirschie Johnson
Vanderbilt University, Nashville, USA
演題：As Time Glows By: Circadian Rhythms from Molecules to Populations
日時：平成28年6月3日（火）16：20〜17：50
場所：東京大学理学部3号館3階326号室

"Chronobiologists" study biological oscillators, the most prominent being circadian rhythms that are circa-24 h "clocks" that act as biological timekeepers to help organisms adapt optimally to the daily light/dark (and temperature) cycles that result from the earth's rotation. Twenty-five years ago, chronobiologists did not believe that prokaryotic organisms (aka bacteria) had circadian oscillators. This idée fixe was overturned by discoveries from our laboratory and others that demonstrated a bona fide circadian clock system in prokaryotic cyanobacteria (aka blue-green algae). Since that time, tremendous strides have been accomplished in our understanding of this bacterial clock system, which has remained at the forefront of circadian rhythm research. For example, the cyanobacterial system provided the first rigorous tests of the adaptive significance of circadian clocks. Moreover, the cyanobacterial clock proteins KaiA, KaiB, and KaiC were the first to have their crystal structures solved. Most remarkable was the first demonstration of a biochemical oscillator reconstituted from purified KaiA, KaiB, and KaiC proteins in vitro. In a fundamental sense eukaryotic clock systems may be organized very similarly to the cyanobacterial system, including multiple oscillators that are coupled to promote resilience. Moreover, the cyanobacterial circadian program regulates gene activity and metabolic pathways, and it can be manipulated to improve the expression of practically useful bioproducts (e.g., biofuels, biopharmaceuticals) using cyanobacteria as bioreactors. Finally, we are extending our studies on the adaptive value of circadian rhythms in cyanobacteria to other bacteria that have KaiB and KaiC genes to illuminate the steps by which biological clocks may have evolved.

世話人：理学系研究科　深田吉孝

第1017回生物科学セミナー
演者：Jürgen A. Ripperger
Biochemistry, University of Fribourg, Switzerland
演題：Flexibility of the liver circadian oscillator
日時：平成26年11月28日（金）15：30〜17：00
場所：東京大学理学部3号館3階326号室

Circadian clocks allow organisms to synchronize their metabolism and physiology to the external photoperiod. They not only provide stable phase relationships between the organs, but also anticipate daily recurring events. Consequently, the system had to evolve specific adaptation mechanisms to adjust to changing photoperiods e.g., during the seasons. Previously, we identified an uncoupling mechanism of the liver circadian oscillator that maintained the anticipation of the light to dark transition under different photoperiods (Stratmann et al., Genes & Development 2010). A subsequent finding (Ukai-Tadenuma et al., Cell 2011) suggested that the uncoupling mechanism was part of a regulatory network. Here, I will describe our attempts to model the adjustment of the liver circadian oscillator based on the interaction of eight genes, which are part of the regulatory network, and assuming a single input into the system. Computational modeling will allow us to understand the critical processes underlying the flexibility of the liver circadian oscillator.

世話人：理学系研究科　深田吉孝

第995回生物科学セミナー
演者：Dr. Satchidananda Panda
Salk Institute for Biological Studies La Jolla, California, USA
演題：Balance between phase shift and coupling among the SCN neurons determines adaptation to ambient light dark condition.
日時：平成26年8月1日（金）15：00〜16：30
場所：東京大学理学部3号館3階326号室

Coupling among cell autonomous circadian oscillator neurons ensures robust rhythm in rest-activity that is relatively resistant to abrupt change in ambient light. The master regulator for such intercellular coupling is unknown. We took a genomic approach to find coupling mechanism with the hypothesis that light induced phase shift weakens coupling among SCN neurons and makes them labile to phase shift. We found that phase-shifting pulse of light transiently down-regulates Lhx1 expression in the SCN and its target coupling factors. Mice with reduced expression of Lhx1 in the oscillator neurons of the Suprachiasmatic nucleus have intact cell autonomous oscillators, but weakened coupling. This renders the mice susceptible to large phase shifts with change in ambient light and under constant darkness the activity-rest cycle dampens to arrhythmicity.

世話人：理学系研究科　深田吉孝

第987回生物科学セミナー
演者：八木田　和弘　教授
京都府立医科大学大学院医学研究科統合生理学
演題：概日時計の発生メカニズム：ES細胞にはなぜ時計がないのか？
日時：平成26年4月18日（金）15：00〜17：00
場所：東京大学理学部3号館3階326号室

　一生にわたって生体内で時を刻み続ける概日時計は、睡眠覚醒リズムをはじめ、内分泌やエネルギー代謝など、極めて多岐にわたる生理現象の日内変動（概日リズム）を制御している。概日リズムの中枢は、視床下部にある視交叉上核(SCN)であることが分かっているが、一方で、末梢組織のほとんどの体細胞にも概日時計が存在する。視交叉上核であれ末梢細胞であれ、哺乳類の概日時計は、初期胚には見られず、発生過程において獲得されることが知られている。しかし、全身の細胞に備わる概日時計がいつどのように形成されるのか、また、概日時計の発生はin vitroで再現できるのか、など概日時計の発生を制御する「原理・仕組み」はこれまでほとんど分かっていなかった。最近我々は、マウスES細胞を用いて、概日時計の成立過程を解析した。その結果、１）ES細胞には概日時計の振動は見られないこと、２）しかし、分化誘導培養によって概日時計が細胞自律性に形成されてくること、３）さらに、分化した体細胞をリプログラミングすることで、再び概日時計が消失すること、などを明らかにした。つまり、細胞レベルの概日時計の成立に個体発生は必要ではなく、個々の細胞自律的に約２４時間周期の時計が形成される事がわかった。しかも、この概日時計の成立は、細胞分化と密接に関連した生命現象であることが示され、概日時計と細胞分化の意外な接点が見いだされた。今回、さらに最近我々が明らかにした概日時計発生の分子メカニズムについて、多能性幹細胞や細胞分化制御との関連を含めて紹介したい。

世話人：理学系研究科　深田吉孝

東京大学大学院理学系研究科生物化専攻セミナー
演者：Dr. Adbelhalim Azzi
Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
演題：Day length reorganizes the SCN neuronal network
日時：平成26年3月31日（月）16：00〜17：30
場所：東京大学理学部3号館3階303号室

In mammals, daily behavior and physiology are controlled by the suprachiasmatic nuclei (SCN) of the hypothalamus (Master clock). The period lengths of these processes are partially controlled by genetic factors. However, previous studies have also shown that exposing genetically identical mice to light/dark cycles longer or shorter than 24 hours can result in long-lasting changes of endogenous free-running period (FRP) (“aftereffects”, Pittendrigh 1976). These changes in period, is referred to period “aftereffects” and can persist for months in constant conditions. We have shown that such aftereffects are dependent upon dynamic DNA methylation in the SCN (Azzi et al., Nat. Neurosci, 2014).
To understand the mechanistic underpinning of period aftereffects, 3-week-old PER2::LUC mice were entrained to non-24h light: dark cycles (T-cycles) of 22, 24 or 26 hours. As expected, behavioral period aftereffects were proportional to T-cycle length (22.5, 24, and 25 hours respectively). Also consistent with previous work (Aton 2004; Molyneux 2008), but far less easily explained, SCN period lengths in vitro recorded from T cycle-entrained mice displayed a negative correlation with behavioral period. Therefore, we hypothesized that non-24h light:dark cycles may change SCN network properties by altering intercellular coupling. Surprisingly, bioluminescence imaging revealed that SCN spatiotemporal organization is markedly affected by T-cycle length, with complete reversal of the phase relationship between dorsal and ventral SCN. Supporting the idea that interneuronal coupling plays an important role in aftereffects, period of SCN slices from mice with both long- and short-period aftereffects could be normalized to 23.5 hours by treatment with Tetrodotoxin (TTX), which blocks neuronal network. Importantly, we find that GABAergique signaling, which is involved in SCN interregional coupling, plays a crucial role in aftereffects. Period of SCN slices from mice with both long- and short-period aftereffects could be relaxed after treatment with GABA blocker.
These results indicate that entrainment to non-24h light dark cycle likely alters SCN organization through changes in network properties. Further experiments should provide insight into the mechanisms underlying this form of circadian plasticity.

世話人：理学系研究科　深田吉孝

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化学専攻セミナー
演者：Trevor D. Lamb　教授
John Curtin School of Medical Research, and ARC Centre of Excellence in Vision Science, Australian National University, Canberra, ACT 0200, Australia
演題：Phototransduction in rods and cones of the vertebrate retina
日時：平成23年7月25日（月）13：30〜15：30
場所：東京大学理学部3号館4階416号室

The rod and cone photoreceptor cells of the vertebrate retina transduce light into a neural signal using closely similar cellular and molecular mechanisms, though with a number of subtle differences that together endow the cell types with distinctive functional properties. Cones mediate vision over most light levels, providing relatively high-speed responses; importantly, they adapt over an enormously wide range of light intensities and never saturate during steady illumination. Rods operate under extremely low light conditions, and reliably detect individual photons of light; they saturate once the intensity of illumination exceeds twilight levels.
The molecular mechanism of transduction in vertebrate photoreceptors is understood in detail. Light-activated rhodopsin catalyses the activation of the G protein transducin, which in turn activates a PDE, thereby hydrolysing cyclic GMP and closing ion channels in the plasma membrane and shutting-off the “dark current” of cations. Using this knowledge it is possible to predict the waveform of the photoreceptor’s response to light.
Rods and cones differ anatomically, in the topology of the outer segment membrane. In addition there are differences in the proteins of phototransduction. Some of these proteins are expressed as rod- and cone-specific isoforms, whereas others are identically the same protein in rods and cones; in addition, the expression levels may differ significantly between rods and cones.
For some of these differences in cellular and molecular make-up of rods and cones, it is possible to predict differences in functional properties of the cell types. Soon it may be possible to account for all of the physiological differences betweens rods and cones.

Lamb, T.D. & Pugh, E.N. Jr (2006). Phototransduction, dark adaptation, and rhodopsin regeneration. The Proctor Lecture. Invest. Ophthalmol. Vis. Sci. 47, 5138-5152.

Lamb, T.D., Collin, S.P. & Pugh, E.N. Jr (2007). Evolution of the vertebrate eye: Opsins, photoreceptors, retina, and eye-cup. Nat. Rev. Neurosci. 8, 960-975.

世話人：理学系研究科　深田吉孝

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化専攻セミナー
演者：土居　雅夫　准教授
京都大学　大学院薬学研究科　医薬創成情報科学専攻　システムバイオロジー分野
演題：これからもっと増える生体リズム調節分子〜細胞時計からシステム時計の解析へ〜
日時：平成23年7月6日（水）15：00〜16：30
場所：東京大学理学部3号館4階416号室

生体リズムを調節する分子は一体どれだけ存在するのであろうか？個々の細胞の中で働く時計遺伝子の正体は明らかにされてきたが、多細胞生物のリズムは細胞集団の総和として出力されるものである。細胞が互いに連絡をとり、リズムを同期させる仕組みがなければ、全体のリズムは破綻してしまう。これまでの細胞時計の枠組みを越え、細胞間連絡に関わる新しいタイプのリズム調節分子の探索に向かって生物時計の研究はあらたな一歩を踏み出した。今回のセミナーでは脳内中枢時計Suprachiasmatic Nucleusにおいて細胞間コミュニケーションに関わるGタンパク質時刻調整メカニズム（Nature Commun.）や, 末梢時計の異常により引きおこる高血圧発症メカニズムについてヒトの臨床応用を見据えた研究の成果（Nature Med.）をご紹介したい。

Doi et al., Circadian regulation of intracellular G-protein signaling mediates intercellular synchrony and rhythmicity in the suprachiasmatic nucleus. Nature Commun. 2, 327, 2011.

Doi et al., Salt-sensitive hypertension in circadian clock-deficient Cry-null mice involves dysregulated adrenal Hsd3b6. Nature Med. 16, 67, 2010.

Doi et al., Impaired light-masking in dopamine D2 receptor-null mice. Nature Neurosci. 9, 732, 2006.

Doi et al., Circadian regulator CLOCK is a histone acetyltransferase. Cell 125, 497, 2006..2

Doi et al., Negative control of circadian clock regulator E4BP4 by casein kinase Ie-mediated phosphorylation. Curr. Biol. 14, 975, 2004.

Doi et al., Light-induced phase-delay of the chicken pineal circadian clock is associated with the induction of E4bp4, a potential transcriptional repressor of cPer2. PNAS 98, 8089, 2001.

世話人：理学系研究科　深田吉孝

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化専攻セミナー
演者：Dr. Tomoko Obara
Dept. of Cell Biology University of Oklahoma Health Science Center Oklahoma City, OK 73104, USA
演題：The Basal body protein Wtip regulates cilia mediated processes by modulating non-canonical Wnt signaling
日時：平成22年12月25日（土）11：00〜12：00
場所：東京大学理学部3号館4階416号室

Cilia are antennae-like organelle characterized by the presence of nine peripheral doublets of microtubules. They originate from the basal body, which is located just below the cell surface and is analogous to the centrioles. In the past few years the importance of cilia has been realized by the observation that many gene products mutated in human diseases are localized in the cilia and/or basal bodies/centrosomes. These so called ciliopathies share some common and unexpected clinical phenotypes such as polycystic kidney disease, nephronophthisis, Senior-Loken syndrome type5, orofaciodifital syndrome type I and Bardet-Biedl syndrome which made refocused to our understanding of various human diseases. Unfortunately, many of the underlying cellular signaling events still remain unclear.
Wilm Tumor suppressor gene (Wt1) interacting protein (Wtip) maps to human chromosome 19, a region linked to familial focal segmental glomerulosclerosis (FSGS). It contains three LIM and a PDZ binding domain. However, the precise in vivo function of the Wtip is still unknown. To elucidate the function of Wtip, we studied its function during the zebrafish embryonic development.
Unexpectedly, zebrafish Wtip protein was found to localize in the basal bodies/centrosomes. Using MO-mediated knockdown, wtip morphants revealed kidney cyst formation accompanied by cloaca obstruction, hydrocephalus, body axis curvature and heart edema, which are similar to our previous studies in the pkd2 morphants. We further characterized the phenotype in the pronephros and found out that Wtip is required to maintain planar cell polarity (PCP), cilia length, numbers and cilia proteins trafficking defects for Polycysin-2 and Ift88. In addition to the kidney defects, we also discovered that loss of wtip results left-right asymmetry and conversion extension cell movement defects such as widened rhombomeres, somites and a shortened body axis due to KV defects such as cilia length, number, KV’s cell shape accompanied by a defect in centrosome migration to the apical cell surface. Moreover, we explored whether these phenotypes caused by loss of wtip are due to PCP signaling, by analyzing potential association to the core PCP and basal body protein Vangl2 which is essential to maintain actin organization. Based on these data we propose that Wtip may provide a new player in ciliopathies modulating non-canonical Wnt signaling.
世話人：理学系研究科　小島大輔

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化専攻セミナー
演者：Dr. Kyungjin Kim
Department of Biological Sciences and Brain Research Center for the 21st Century Frontier Program in Neuroscience, Seoul National University, Seoul 151-742, Korea
演題：BioClock: From Molecule to Behavior
日時：平成22年12月13日（月）16：00〜17：30
場所：東京大学理学部3号館4階416号室

Central clock resides in the suprachiamatic nucleus (SCN) of the hypothalamus. Recent studies using genetic and molecular approaches have disclosed fundamental features of molecular circadian clockwork and the network of transcription-translation feedback loops of clock machinery functions not only in the SCN, but also in peripheral clocks in most peripheral tissues. I will discuss our recent findings with two different topics: 1) Adrenal peripheral clock: Adrenal gland has its own intrinsic clock and the peripheral clockwork is tightly linked to steroidogenesis by a StAR(steroidogenic acute regulatory protein). Examination with transgenic mice harboring the adrenal-specific disruption of clock machinery shows that the adrenal clock controls rhythmic StAR expression and glucocorticoid production. The adrenal local clock appears to play an important role in harmonizing circadianphysiology and behavior. 2) Ultradian rhythm of GnRH (Gonadotropin-Releasing Hormone) gene expression: Although pulsatile GnRH secretion from the hypothalamus is reported to be associated with the oscillatory GnRH gene expression, the cellular and molecular mechanism underlying the so-called ‘GnRH pulse generator’ remains to be explored. We generated transgenic mice carrying the rat GnRH promoter-driven destabilized luciferase reporter (GnRH-dsLuc), and monitored the GnRH promoter activity in individual GnRH neurons derived from postnatal hypothalamic slices by using a real-time bioluminescence recording system. GnRH gene expression is quite irregular, but shows robust ultradian oscillation in a cell-intrinsic manner. In vitro administration of kisspeptin, a potent neuropeptide of GnRH neurons amplifies pulsatile GnRH gene expression by augmenting the pulse amplitude. More importantly, rhythmic treatment of the kisspeptin synchronizes the regular oscillatory GnRH gene expression in the hypothalamus.

- Son GH et al. 2008. Adrenal peripheral clock controls the autonomous circadian rhythm of glucocortioid by causing rhythmic steroid production.
PNAS 105:20970-5.
- Lee Y et al. 2010. Coactivation of the CLOCK-BMAL1 complex by CBP mediates resetting of the circadian clock.
J Cell Sci. 123:3547-3557.
- Lee J et al. 2008. Dual modification of BMAL1 by SUMO2/3 and ubiquitin promotes circadian activation of CLOCK/BMAL1 complex.
Mol Cell Biol. 28:6056-65.
- Shim HS et al. 2007. Rapid activation of CLOCK by Ca²⁺-dependent protein kinase C mediates resetting of the mammalian circadian clock.
EMBO Rep. 8:366-71.
- Kwon I et al. 2006. BMAL1 shuttling controls transactivation and degradation of the CLOCK/BMAL1 heterodimer.
Mol Cell Biol. 26:7318-30.

世話人：理学系研究科　深田吉孝

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化専攻セミナー
演者：Dr. David Whitmore
　　　Deptment of Cell and Developmental Biology, University College London, London, UK
演題：Clock control of cell division: intimate links in zebrafish
日時：平成22年11月8日（月）11：00〜12：30
場所：東京大学理学部3号館4階416号室

Zebrafish are a useful model for the study of clock function, not least because they possess robust circadian oscillators within most of their tissues and cells. These tissues are themselves directly light responsive, and so the fish clock system appears to be highly decentralized with little, if any, need for a central, master clock, as in mammals. This light responsive property is also found in zebrafish cell lines, making them a unique system with which to study clock function. In addition, zebrafish are an excellent system to study the development of the circadian clock, as large numbers eggs are fertilized and develop outside the female, providing a major advantage to embryonic studies in mammals. Data relating to clocks in cell lines and during embryo development will be discussed further in this seminar. In contrast, we will describe new data regarding clock function in Astyanax mexicanus, the blind Mexican cavefish, and discuss some of the changes that have occurred following evolution in the dark. Another issue of significant interest relates to what cell biological processes the clock itself controls; what are the rhythmic, clock controlled outputs in zebrafish? Dr Tamai will present new data describing the very close molecular connection between the zebrafish clock and control of the cell cycle. In zebrafish cells and embryos, the clock drives very robust rhythms in both S- and M-phase timing of the cell cycle through the rhythmic regulation of key cell cycle regulators.

Dekens, M.P. and Whitmore, D. Autonomous onset of the circadian clock in the zebrafish embryo. (2008) EMBO J. 27: 2757-65.
Tamai, T.K., Young, L.C., and Whitmore, D. Light signalling to the zebrafish circadian clock by Cryptochrome 1a. (2007) PNAS 104: 14712-14717.
Carr, A.J. and Whitmore, D. (2005) Imaging of single light responsive clock cells reveals fluctuating free-running periods. Nat. Cell Biol. 7: 319-321.

世話人：理学系研究科　深田吉孝

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化専攻セミナー
演者：Dr. Samer Hattar
　　　Assistant Professor, Departments of Biology and Neuroscience (JHMI), Johns Hopkins University (Baltimore, USA)
演題：Rod photoreceptor retinal circuits impinge on melanopsin ipRGCs for influencing circadian photoentrainment
日時：平成22年6月4日（金）17：00〜18：30
場所：東京大学理学部3号館4階416号室

The discovery of atypical ganglion cell photoreceptors (melanopsin containing intrinsically photosensitive retinal ganglion cells; ipRGCs) in the mammalian retina has greatly advanced our understanding of how light influences several non-image forming visual functions independent of image formation. Some of the non-image forming functions are the adjustment of our internal circadian rhythms to the solar day, which influence our mood, alertness and even learning and memory. We have studied extensively the contribution of outer retinal photoreceptors to the regulation of circadian photoentrainment. We find that rods are the predominant photoreceptor type responsible for circadian photoentrainment from the outer retina, with cones playing a minor role in this function. We further determine how the rod photoreceptors send this information to ipRGCs at different light intensities. Our data reveal an unappreciated role for rods in circadian photoentrainment and determine the retinal circuits of how this response is achieved.

Güler AD, Ecker JL, Lall GS, Haq S, Altimus CM, Liao HW, Barnard AR, Cahill H, Badea TC, Zhao H, Hankins MW, Berson DM, Lucas RJ, Yau KW, Hattar S. (2008) Melanopsin cells are the principal conduits for rod-cone input to non-image-forming vision. Nature 453, 102-5.

世話人：理学系研究科　深田吉孝

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化専攻セミナー
演者：笠原和起博士
　　　理化学研究所脳科学総合研究センター　精神疾患動態研究チーム　副チームリーダー
演題：実験用マウスは飼育舎の中で独自の進化を遂げてメラトニンを作らないようになった
日時：平成22年6月4日（金）15：00〜16：30
場所：東京大学理学部3号館4階416号室

メラトニンは松果体において生合成されるホルモンであり、概日リズムや季節性繁殖応答の調節にかかわっていると考えられている。不思議なことに、実験用マウスの多くの系統がメラトニンを合成しない。さらに奇妙なことに、メラトニン合成系の最終酵素HIOMT（hydroxyindole O-methyltransferase）をコードする遺伝子が、ゲノム解読プロジェクトの完了宣言後でもマウスからは見つかっていなかった。我々は、ラットHIOMTの配列をヒントに、メラトニンを作るマウス系統C3H/HeからHiomt cDNAをクローニングすることに成功した。メラトニンを作れないC57BL/6系統にもHiomt遺伝子は存在し、アミノ酸置換を伴う点変異が2ヶ所存在していた。どちらの変異とも、酵素の発現を強く抑制した。FISH解析の結果、Hiomt遺伝子が性染色体の偽常染色体領域（PAR）に存在することを見出した。PARは組換え頻度が平均的な染色体領域よりも約100倍高いため、変異が生じやすい。このことが、実験用マウスの多くがHIOMT活性を失った原因のゲノム科学的な説明になろう。Hiomtの変異が飼育舎内のコロニーに固定された生理学的な（飼育者にとっては経営学的な）要因について調べたところ、メラトニンが作れないマウスでは精巣の発達が早くなることがわかった。数多くの系統のHiomt遺伝子を調べた結果からも、Hiomtの変異の固定が偶然のドリフトに起因する可能性は低く、次世代を早く誕生させる独自の進化が人間によって長年飼育された過程に起きたと推測された。

Kasahara T, Abe K, Mekada K, Yoshiki A, Kato T. (2010) Genetic variation of melatonin productivity in laboratory mice under domestication. PNAS 107, 6412-6417.

世話人：理学系研究科　深田吉孝

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化専攻セミナー
演者：Dr. Daniel R. Storm
　　　Department of Pharmacology, The University of Washington, Seattle, USA
演題：The Role of Signal Transduction Cross-Talk in Memory Formation
日時：平成21年9月14日（月）14：00〜16：00
場所：東京大学理学部3号館4階416号室

The central nervous system has the remarkable capacity to process and store enormous amounts of information. Consequently, there is intense interest in molecular and cellular mechanisms underlying the formation and persistence of memory. One of the transcriptional pathways required for consolidation of hippocampus-dependent memory is CRE-(cAMP, Ca2+, Response, Element) mediated transcription. Although a number of signal transduction systems contribute, calmodulin (CaM)-stimulated adenylyl cyclases and Erk/MAP kinases (MAPK) play a major role in Ca2+ activation of CRE-mediated transcription in neurons during formation of memory. Our lab has discovered that the nuclear translocation and activation of MAPK in neurons during contextual memory formation depends upon CaM-stimulated adenylyl cyclases. Furthermore, activation of MAPK also depends on proteolytic degradation of SCOP (SCN Circadian Oscillatory Protein) by calpain. Interestingly, the persistence of contextual memory is maintained by the circadian oscillation of the cAMP/MAPK/MSK1/CREB transcriptional pathway in area Ca1 of the hippocampus, an oscillation that depends upon CaM-stimulated adenylyl cyclases. The goal of this presentation is to show how all these signaling components act synergistically to produce memory traces in the hippocampus.

世話人：理学系研究科　深田吉孝／清水貴美子

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化専攻セミナー
演者：Dr. David C. Klein
　　　Senior Investigator, Section on Neuroendocrinology, National Institute of Child Health and Human Development, National Institutes of Health, USA
演題：Transcriptome Profiling of the Rodent Pineal Gland: The Impact
日時：平成21年6月1日（月）17：30〜19：00
場所：東京大学理学部3号館4階416号室

The pineal gland is characterized by a 24-hour activity cycle, which is best represented by the daily rhythm in melatonin production. The rhythm in circulating melatonin provides an indicator of time and is used in a variety of ways to coordinate physiological processes with daily and seasonal changes in environmental lighting. A recently completed study (1) of gene expression in the pineal gland has revealed the highly expressed genes in this tissue and has identified genes which exhibit daily changes in expression, including >600 genes with 2-fold or greater night/day differences. In some cases, the night/day differences are ~100-fold. These changes appear to be due primarily to adrenergic-cyclic AMP signaling. The findings of this effort have triggered investigations of a broad nature, including those related to development, to the molecular nature of pineal/retina similarity, to signal transduction, to the role of the thyroid hormone in pineal signal transduction and to the role of the pineal gland in the immune/inflammatory response. Current work is directed at identifying the conserved genetic features of the vertebrate pineal gland, based on studies of the transcriptomes of the zebrafish, mouse, rhesus and human pineal glands.

Reference:
1) Bailey MJ et al. (2009) Night/day changes in pineal expression of >600 genes: Central role of adrenergic/cAMP signaling. J. Biol. Chem. 284: 7606 -7622.

世話人：理学系研究科　深田吉孝

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化専攻セミナー
演者：本間さと教授
　　　北海道大学大学院医学研究科生理学講座
演題：季節を知る脳の時計：発光レポーターマウスを用いた解析
日時：平成21 年4 月11 日（土）14：00 ~ 15：30
場所：東京大学理学部3 号館4 階416 号室

生体の機能には、ミリ秒から年余に及ぶ様々な長さの周期をもつリズムがあり、その多くは、背後に時計機構（ペースメーカー）の存在が明らかとなっている。中でも、約24 時間の周期をもつサーカディアンリズムの発振機構、すなわち「生物時計」は、バクテリアからヒトまで共通に存在し、リズム発振の分子機構や、光による位相の調節なども基本的に一致している。このため、サーカディアンリズムは、地上の明暗サイクルの下で生存するため生物が進化の過程で獲得した生体戦略と考えられる。動物におけるサーカディアンリズム発振は、時計遺伝子の転写と蛋白産物による転写抑制の自律発振分子フィードバックループによると考えられる。近年の分子時計研究の急速な発展には、生物発光レポーター技術が大きく貢献している。時計遺伝子転写活性や蛋白レベルを生物発光により組織レベルで、あるいは細胞レベルで遺伝子発現を連続測定することが可能となった。そこで、各種発光レポーター技術と、発光レポーターマウスを用いて最近明らかにした日長の季節変化に応じて動物が活動時間を変えるメカニズムについて、長期間連続測定や解析法を含め、紹介したい。

世話人：理学系生物化学専攻深田吉孝

第110回平成21年春季　東京大学公開講座　2009年4月4日（土）
演者：深田吉孝
演題：時刻特異的な生命現象を生み出す体内時計

講演の様子

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化専攻セミナー
演者：Dr. Steven A. Brown
　　　Professor, Institute for Pharmacology and Toxicology, University of Zurich, Switzerland
演題：Layers of Clocks: Keeping Cellular Time in Different Frames
日時：平成21年3月6日（金）1６：０0〜1７：３0
場所：東京大学理学部旧1号館3階350号室

Human behavior is influenced by many genetic and environmental factors; it is therefore often difficult to study by reductionist approaches. However, in rare cases it can be linked directly to a biological process that can be understood at the cellular level. The circadian clock is one such instance: physiologically, it affects diverse processes such as sleep-wake time, activity patterns, body temperature, cardiac and respiratory rate, renal flow, and digestion. Molecularly, it is present in most cells of the body and modulates the transcription of about ten percent of our genes. Although this clock tells time at a daily level, recent research from my laboratory and others suggests that its mechanism is connected to biological clocks with other metrics. By directly controlling the transcription of some cell cycle genes, the circadian clock likely gates cell division, perhaps in order to segregate DNA replication from catabolic processes. Through shared components, it can be coordinately regulated with cellular senescence pathways. Finally, circadian clock function is itself governed by individual genetic differences and physiology, which explain its different behavior in ageing humans, and thus its subjection to each of our overall “lifetime” clocks. Together, this delicate interplay provides a mechanistic explanation for physiological timing in several frames.

Brown, S.A. et al. (2008) Molecular insights into Human Daily Behavior. Proc. Natl. Acad. Sci. USA, 105:1602-1607.

Brown, S.A. et al. (2005) PERIOD1-associated proteins modulate the negative limb of the mammalian circadian oscillator. Science 308:693-6.

哺乳類の概日時計は、中枢に存在する主振動体と末梢組織に存在する従属振動体群から構成されるが、Brown 博士は末梢組織である線維芽細胞の解析を通じて、ヒトの中枢組織における時計発振機構の理解を目指している。参考文献において Brown 博士はヒト線維芽細胞に内在する時計を可視化し、リアルタイムで観察する実験系を構築した。さらに、線維芽細胞における時計発振の性質が、ヒトの生活リズムの特徴をも反映していることを明らかにした。今回のセミナーでは、これらの成果と最新の研究についてBrown 博士に講演していただく。

世話人：理学系研究科　深田吉孝

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化専攻セミナー
演者：Dr. Urs Albrecht
　　　Dept. of Medicine, Div. of Biochemistry University of Fribourg, Switzerland
演題：Clocks, brain function and dysfunction
日時：平成20 年11月13 日（火）1５：３０ ~ 1７：０0
場所：東京大学理学部3 号館３４階４１６号室

It is estimated that about 20% of the population in industrialized countries are affected by mood disorders such as depression and eating disorders. One of the hallmarks of industrialized countries is the fact that the natural day/night regime is largely ignored due to the availability of artificial light sources. As a consequence activity well beyond the borders given by nature have become possible. Therefore synchronization of the circadian system by natural cues has become inefficient leading to a misalignement of periodic physiological processes, which can hamper normal brain function. This derailment of the circadian system is probably one of the reasons for the increased incidence of depression, excessive alcohol consumption and over-eating in modern society. Apart from its function in the clock mechanism in the suprachiasmatic nuclei, the clock gene Per2 appears to have additional functions in other areas of the brain. It is postulated that a food entrainable oscillator (FEO) resides in the brain, which is responsible for anticipatory activity in expectation of regularly scheduled meals. A mutation in Per2 leads to loss of food anticipatory activity in mice suggesting an important role of Per2 in the FEO. Interestingly, several studies have found that feeding behavior shares neurobiological mechanisms with the addictive properties of drugs of abuse. Because Per2 not only affects food anticipatory behavior but also modulates the effects of drugs of abuse we postulate that this gene and its protein influences the neurobiological circuitry that is common to feeding signals and drugs, both of which affect the reward system. Evidence will be presented highlighting a role of Per2 in alcohol consumption and cocaine addiction indicating an influence of the clock on glutamatergic as well as dopaminergic signaling. These findings provide a base for development of new approaches in medical treatment of neuropsychiatric disorders.

Spangel, R. et al. (2005) The clock gene Per2 influences the glutamatergic system and modulates alcohol consumption. Nat. Med. 11, 35-42

Hampp, G. et al. (2008) Regulation of Monoamine oxidase A by circadian-clock components implies clock influence on mood. Curr. Biol. 18, 678-683

世話人：理学系生物化学専攻深田吉孝

東京大学グローバルCOE『統合生命学』特別セミナー
東京大学大学院理学系研究科生物化専攻セミナー
演者：Dr. Paul E. Hardin
　　　Department of Biology and Center for Research on Biological Clocks, Texas A&M University, USA
演題：Regulation of transcriptional feedback within the Drosophila circadian clock
日時：平成20 年7月15 日（火）1６：３０ ~ 1８：０0
場所：東京大学理学部3 号館３階３２７号室

Transcriptional activation by CLOCK-CYC (CLK-CYC) heterodimers and feedback repression by PERIOD-TIMELESS (PER-TIM) heterodimers are essential for circadian oscillator function in Drosophila. The function of these transcriptional regulators is regulated by post-translational modifications that alter DNA binding, stability and chromatin modifications. We find that binding of CLK-CYC heterodimers containing hypophosphorylated CLK to E-box elements promotes chromatin modifications that enhance transcriptional activation of per, tim and other circadian oscillator components. PER protein then begins to accumulate, but in a delayed fashion due to DOUBLE-TIME (DBT) dependent phosphorylation and subsequent stabilization by TIM binding. PER-TIM-DBT complexes then enter the nucleus and bind to CLK-CYC, thus promoting the hyperphosphorylation of CLK, loss of CLK-CYC E-box binding, and transcriptional repression. Recent experiments using the PERΔ mutant, which is unable to bind DBT, and hypomorphic dbtar and dominant negative dbtK/R mutants suggest that DBT acts as a bridge to recruit other kinase(s) into PER-TIM-DBT-CLK-CYC complexes. Once these kinases enter DBT-PER-CLK complexes they phosphorylate PER and CLK, thereby promoting transcriptional repression. Subsequent phosphorylation of PER and CLK by DBT promotes PER and CLK degradation, thereby relieving transcriptional repression.

References:
Yu, W., H. Zheng, J. H. Houl and P. E. Hardin (2006) PER dependent rhythms in CLK phosphorylation and E-box binding regulate circadian transcription. Genes Dev. 20, 723-733.

Kim, E. Y., H. W, Ko, W. Yu, P. E. Hardin and I. Edery (2007) A DOUBLETIME kinase binding domain on the Drosophila PERIOD protein is essential for its hyperphosphorylation, transcriptional repression and circadian clock function. Mol. Cell. Biol. 27, 5014-5028.

世話人：理学系生物化学専攻深田吉孝