Fig. 2
From: The choroid plexus is an important circadian clock component
The robust circadian clock in the CP is due to strong synchronization through gap junction coupling. a Single-cell level circadian oscillation of PER2::LUC activity in the CP (upper) and the SCN (lower). b Single-cell level oscillations of Bmal1-ELuc. In the SCN, each time series tracks changes of bioluminescence in a square region-of-interest (ROI) of single-cell size. ROIs of the same dimension are used on distinct regions in the CP as single cells were visually indistinct. c Immunohistochemistry against the gap junction subunit Cx43 shows its expression between cells of the CP. Scale bar indicates 50 μm. d For self-sustained oscillators exhibiting negative twist, an increasing (instantaneous) amplitude transiently leads to a decreasing (instantaneous) period as the oscillator returns to its steady-state oscillation. Isochrons represent lines in the phase space with identical oscillator phases as time t goes to infinity65 (see Methods). In systems without twist, isochrons form straight radial lines (thick black lines). In oscillators with negative twist, isochrons become bent or “twisted” (thick red line). In networks of interacting oscillators, coupling can expand the amplitude of single-cell oscillators and speed up the oscillation under negative twist (inset). See Supplementary Fig. 3 for detailed illustrations. e Cellular circadian oscillations in the entire 4V CP can be observed in vivo (upper left). In culture, Bmal1-ELuc oscillation shows spatial patterning of the peak phase of its circadian oscillation, which is statistically significant for the first 3–4 days (see Supplementary Fig. 4). The central region of the 4V CP phase leads (upper), which can be explained by the boundary value condition in the nearest neighbor coupling of gap junctions (lower)
