講師資料
Talks：
Peripheral Circadian Clocks Emerge Before the SCN via SNIC in Mouse Embryos
外周晝夜節律時鐘在小鼠胚胎中透過 SNIC 分岔先於視交叉上核出現
Name：
Jihwan Myung（明智煥）
Position：
Associate Professor
Affiliation：
Laboratory of Braintime, Graduate Institute of Mind, Brain and Consciousness (GIMBC), Taipei Medical University
Email：
Photo：
Research Interests：
Circadian biology (molecular biology and behavior),
Computational neuroscience (nonlinear dynamics, entrainment, chemical kinetics)
Selected Publications：
1. Vitet, H., Truong, V. H., Myung, J. (2025). Choroid Plexus Hosts the Earliest Detectable Circadian Clock in the Brain. bioRxiv, 2025-09.
2. Sládek, M., Houdek, P., Myung, J., Semenovykh, K., Dočkal, T., Sumová, A. (2024). The circadian clock in the choroid plexus drives rhythms in multiple cellular processes under the control of the suprachiasmatic nucleus. Fluids and Barriers of the CNS, 21(1), 46.
3. Myung J, Schmal C, Hong S, Tsukizawa Y, et al. (2018). The choroid plexus is an important circadian clock component. Nature Communications. 9: 1062.Myung J, Hong S, DeWoskin D, De Schutter E, et al. (2015). GABA-mediated repulsive coupling between circadian clock neurons in the SCN encodes seasonal time. Proceedings of National Academy of Sciences USA. 112: E3920-E3929.
Abstract：
The mammalian circadian system has traditionally been viewed as hierarchical, with the suprachiasmatic nucleus (SCN) serving as the central pacemaker that synchronizes peripheral clocks throughout the body. This framework has shaped our understanding of how circadian oscillators develop during embryogenesis. However, with PER2::LUC and Bmal1-ELuc bioluminescence imaging and circadian time-series qPCR across mouse embryogenesis, we report a different developmental sequence. In the brain, we found that the fourth ventricular choroid plexus (4VCP) exhibits the first detectable circadian oscillations by E11.5 to E12.5, about three days before the SCN clock emerges at E15.5. Similarly, in peripheral tissues, time-differential imaging revealed that the embryonic heart initiates autonomous circadian rhythms prior to SCN development. Oscillations of genes that regulate cardiac excitability are detectable by E13.5, and heart rate rhythms phase-lock to PER2::LUC peaks well before the establishment of sympathetic or parasympathetic innervation. These early peripheral clocks display an abrupt, nonlinear onset pattern consistent with a saddle-node on invariant circle (SNIC) bifurcation, with initial periods that diverge near onset. In the 4VCP, Bmal1-ELuc oscillations start at E13.5, coincident with differentiation markers. The earlier PER2::LUC relative to Bmal1-ELuc suggests a molecular sequence consistent with SNIC and contrasts with the Hopf-type dynamics typical of mature circadian clocks. The SNIC bifurcation pattern supports a developmental model where key peripheral clocks emerge abruptly at defined embryonic stages through autonomous bifurcation events, independent of SCN control. These results provide new insights that may improve clinical care approaches for preterm neonates.

Keywords: Circadian clock emergence, SNIC bifurcation, Choroid plexus, Embryonic cardiac rhythm, Suprachiasmatic nucleus 
2025年會：