CV Science

Claude Gronfier PhD Neuroscience, Senior Research Scientist (Associate Professor), tenure

Course and current status

EDUCATION:

1991         Bachelor (L)     Cellular Biology & Physiology                        University of Dijon, France

1992         Master's (M1)    Animal Physiology                                        University of Dijon, France

1993         D.E.A. (M2)      Pharmacology and Pharmacochemistry         University of Strasbourg, France

1997         D.U.            Statistical Methodology                                University of Strasbourg, France

1998         Ph.D. (D)          Neuroscience                                               University of Strasbourg, France

2014         HDR                 Non-visual Photobiology in Humans              University Claude Bernard, Lyon

ACADEMIC APPOINTENTS:

1999-03    Research Fellow in Medicine, "Training in Sleep Circadian and Respiratory Neurobiology", Mentor Prof. Charles A. Czeisler, Chief Division of Sleep Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston MA, USA

2003/08    Research Scientist, INSERM U846 (H Kennedy), Department of Chronobiology, Bron France

2008-        Senior Research Associate (CR1, Associate Professor, tenure), INSERM U846, Department of Chronobiology, Bron France

2018-        Senior Research Scientist (CRCN), Lyon Neuroscience Research Center, INSERM U1028, Waking team, Lyon, France

PROFESSIONAL SOCIETY RESPONSABILITIES:

2004-08    European Sleep Research Society (ESRS), Scientific Committee, elected (2004-2008)

2007-16    French Society for Sleep Research and Medicine (SFRMS), Scientific Committee (2007-2015), Advisory board (2008-2016), nominated

2007-Curr Working Group “Chronobiology”, French Society for Sleep Research and Medicine, Founder and head

2008-11    Society for Light Treatment and Biological Rhtyhms (SLTBR), Board, elected (2008) 

2009-Curr Center for Environmental Therapeutics, Board of Scientific Advisors, elected (2007)

2012-        French Speaking Society of Chronobiology (SFC), Board, elected (2012)

2016-21    GDR Sommeil (Sleep Research Taskforce), Steering Committee

2016         Vice-President, French Speaking Society of Chronobiology (SFC), elected (2016)

2017-19    Organizer/Chair, Congress of the European Biological Rhythm Society, Lyon 2019

2021-25        President, French Speaking Society of Chronobiology (SFC), Board, elected (2012)

EDITORIAL BOARDS:

Journal of Pineal Research (IF 15.6), Frontiers in Neuroscience (Sleep and Circadian Rhythms, Sleep and Vigilance (new), Clocks & Sleep (new) 

Scientific summary

The light we perceive in our everyday life is not only as the main time cue of the biological circadian timing system (a.k.a., the biological clock), but also as an absolutely necessary stimulus of non-visual functions during daytime, and a detrimental stimulus prior to or during nighttime. 

Indeed, many physiological activities such as the sleep-wake cycle, timing and structure of sleep, alertness and sleepiness, hormone levels, neurobehavioral performance, cardiovascular function, and cell cycle regulation, are under the control of the circadian (circa: "close to", dian: "a day") clock, which in mammals is located in the suprachiasmatic nucleus (SCN) in the hypothalamus. Two major properties characterize the circadian clock: (1) the rhythmicity is endogenous, driven by molecular loops (clock genes) within SCN cells which in turn generate self-sustained oscillations of neuronal firing, that are close to but not exactly of 24 hours; (2) the endogenous rhythmicity is maintained in synchrony with the 24-h day by photic inputs from the 24-h light/dark cycle, by daily resetting (advance or the delay) of the clock. Lesion of the SCN abolishes expression of circadian rhythms (no rhythmicity is observed), whereas removal of photic input only abolishes light entrainment of the clock (free running of near 24-h rhythms is observed). In humans, the importance of synchronization of the biological clock is particularly noticeable in jet-lag (after a trans-meridian travel) and in shift-work, where major decrements in many physiological functions (hormones, blood pressure, temperature, cardiovascular system, etc.), neurobehavioral performance (memory, cognitive processes), daytime alertness and sleep are commonly described. Similar—but chronic—symptoms are also observed during aging, in blindness, in neurodegenerative diseases (Alzheimer's and Parkinson diseases), and in cancer. The mechanisms responsible for these decrements are unclear. 

The photic (light) information—necessary to entrain the clock to the 24-h day, is transmitted from the eye to the SCN via a monosynaptic pathway: the retinohypothalamic tract, that is distinct from the optic pathways involved in vision. The response of the circadian system depends on intensity, timing, duration, and spectral characteristics (wavelengths) of light. In addition to the classical photoreceptors (rods and cones) a subset of intrinsically light-sensitive retinal ganglion cells expressing the photopigment melanopsin are involved in circadian photoreception. These cells project mainly to the SCN, but also to structures involved in non-image-forming (a.k.a. non-visual) functions such as the pupillary light reflex (OPN), alertness and sleep (VLPO), cognition and memory (hippocampus), and mood (amygdala, VTA). The peak sensitivity of the melanopsin photopigment is ~ 480 nm (blue-green) in both rodents and humans. Although it is accepted that both photoreceptive systems (classical and non-classical photoreceptors) are involved in circadian photoreception, their interactions and relative contribution are unknown. Furthermore, the functional consequences of inappropriate light exposure on and non-visual and circadian physiology have not been systematically investigated. The therapeutic use of light exists for some disorders (in particular circadian rhythm sleep disorders and mood disorders), but the mechanisms and the neurobiological pathways involved are not totally clear.

The projects of my team investigate the concept that light exposure and its timing are crucial to wakefulness, sleep, and health. They focus on the photobiological mechanisms involved in circadian entrainment; the mechanisms involved in the alertness-activating/sleepiness-inhibiting effects of light; how light exposure in real-life conditions, such as in night work, or at night (ALAN) alter sleep, circadian physiology, and health; whether the timing and quality of light exposure in our everyday life be a predictor of disorders related to sleep and circadian rhythms; to which extent the circadian system or its sensitivity to light can be altered in pathologies (ADHD and Smith Magenis Syndrome) and explain some of the symptoms observed; and how can the non-visual properties of light be used efficiently and practically to avoid or alleviate disorders. 

Check out our published work: https://orcid.org/0000-0002-6549-799X 

Check out our current thoughts/team: : https://www.crnl.fr/en/user/165