Circadian key component CLOCK/BMAL1 interferes with segmentation clock in mouse embryonic organoids

Abstract

In mammals, circadian clocks are strictly suppressed during early embryonic stages, as well as in pluripotent stem cells, by the lack of CLOCK/BMAL1-mediated circadian feedback loops. During ontogenesis, the innate circadian clocks emerge gradually at a late developmental stage, and with these, the circadian temporal order is invested in each cell level throughout a body. Meanwhile, in the early developmental stage, a segmented body plan is essential for an intact developmental process, and somitogenesis is controlled by another cell-autonomous oscillator, the segmentation clock, in the posterior presomitic mesoderm (PSM). In the present study, focusing upon the interaction between circadian key components and the segmentation clock, we investigated the effect of the CLOCK/BMAL1 on the segmentation clock Hes7 oscillation, revealing that the expression of functional CLOCK/BMAL1 severely interferes with the ultradian rhythm of segmentation clock in induced PSM and gastruloids. RNA sequencing analysis implied that the premature expression of CLOCK/BMAL1 affects the Hes7 transcription and its regulatory pathways. These results suggest that the suppression of CLOCK/BMAL1-mediated transcriptional regulation during the somitogenesis may be inevitable for intact mammalian development.

The Relevance of Circadian Clocks to Stem Cell Differentiation and Cancer Progression

“…Furthermore, when the NSCs were induced to dedifferentiate, the cells exhibited loss of circadian oscillations [ 25 ]. These findings and others suggest that ESC differentiation is important for establishing circadian clock functioning during brain development, including within the SCN [ 26 – 28 ].…”

The Clockwork Embryo: Mechanisms Regulating Developmental Rate

“…This may suggest that circadian clock components can be co-opted by the segmentation clock, although any potential functional relevance of Per1 oscillations in the segmentation process remains to be tested. Live imaging of a Per2-Luciferase reporter did not detect oscillatory activity in mouse presomitic mesoderm organoids (105), suggesting that ultradian oscillations are limited to Per1. The Per2 locus is adjacent to Hes6, which is not a component of the mouse segmentation clock (105), therefore strengthening the notion that Per1 only oscillates as a byproduct of Hes7 dynamics and not due to circadian clock activity.…”

“…Intriguingly, the genomic locus of the core circadian clock gene Per1 is located immediately adjacent to that of the core segmentation clock gene Hes7 (105). Such genomic architecture is conserved across higher vertebrates.…”

Target-triggered CRISPR–Cas13a autocatalysis-driven amplification strategy for one-step detection of circadian clock gene

“…Currently, BMAL1 mRNA was mainly identified based on polymerase chain reaction (PCR), 11,12 northern blotting, 13 microarray, 14 and RNA sequencing. 15 Despite some success, most of these methods still suffer from some drawbacks because of the tradeoffs between sensitivity, turnaround time, usability and costs. Therefore, it is essential to establish a new method for rapid, convenient, highly sensitive and selective detection of BMAL1 mRNA with the ultimate goal of understanding its biological functions.…”