bims-ciryme Biomed News
on Circadian rhythms and metabolism
Issue of 2022‒04‒24
two papers selected by
Gabriela Da Silva Xavier
University of Birmingham

  1. Cell Rep. 2022 Apr 19. pii: S2211-1247(22)00461-2. [Epub ahead of print]39(3): 110703
      The current model of the mammalian circadian clock describes cell-autonomous and negative feedback-driven circadian oscillation of Cry and Per transcription as the core circadian rhythm generator. However, the actual contribution of this oscillation to circadian rhythm generation remains undefined. Here we perform targeted disruption of cis elements indispensable for cell-autonomous Cry oscillation. Mice lacking overt cell-autonomous Cry oscillation show robust circadian rhythms in locomotor activity. In addition, tissue-autonomous circadian rhythms are robust in the absence of overt Cry oscillation. Unexpectedly, although the absence of overt Cry oscillation leads to severe attenuation of Per oscillation at the cell-autonomous level, circadian rhythms in Per2 accumulation remain robust. As a mechanism to explain this counterintuitive result, Per2 half-life shows cell-autonomous circadian rhythms independent of Cry and Per oscillation. The cell-autonomous circadian clock may therefore remain partially functional even in the absence of overt Cry and Per oscillation because of circadian oscillation in Per2 degradation.
    Keywords:  CP: Cell biology; circadian clock; circadian oscillator; circadian rhythm; clock gene; cryptochrome; period; protein degradation; protein half-life; transcription
  2. Proc Natl Acad Sci U S A. 2022 Apr 26. 119(17): e2109969119
      SignificanceDaily rhythms in the molecular clock, in calcium, and in electrical activity all interact to support the functions of circadian pacemaker neurons. However, the regulatory mechanisms that unify these properties are not defined. Here, we utilize the cellular resolution of the Drosophila circadian neural circuit with technological improvements in light-sheet imaging. We report that individual Drosophila pacemakers display two cophasic rhythms of daily calcium fluctuations. We previously described the first: slow changes in intracellular calcium. The second involves high-frequency calcium fluctuations that depend on the function of the T-type calcium channel. We propose that the fast rhythms, emerging sequentially across the 24-h day, correspond to spontaneous electrical activity patterns displayed by different pacemaker groups.
    Keywords:  Drosophila; ITPR; T-type calcium channel; calcium; circadian rhythms