Fetoplacental Circadian Rhythms Develop and Then Synchronize to the Mother In Utero

Area of Science:

• * Chronobiology and Developmental Biology
• * Mammalian Embryonic Development
• * Molecular and Cellular Biology

Background:

• * Circadian rhythms in gene expression and hormones are widespread but their prenatal origins are unclear.
• * Understanding the establishment of these rhythms is crucial for fetal health.
• * Maternal factors, like glucocorticoids, may influence fetal development and circadian timing.

Purpose of the Study:

• * To investigate the presence and synchronization of daily rhythms in utero.
• * To determine if fetoplacental circadian rhythms can be influenced by maternal factors.
• * To explore the role of glucocorticoids in synchronizing fetal and maternal circadian clocks.

Main Methods:

• * Longitudinal in utero bioluminescence imaging of PERIOD2 (PER2) protein rhythms in mouse fetoplacental units (embryonic days 8.5-17.5).
• * Monitoring PER2::LUCIFERASE expression restricted to the fetoplacental unit.
• * In vivo administration of corticosterone and in vitro experiments blocking glucocorticoid signaling.

Main Results:

• * Daily PER2 rhythms were detected in utero, stabilizing to early night by embryonic day 15.5.
• * Lack of daily PER2 variation in utero correlated with increased pregnancy failure.
• * Maternal corticosterone injections phase-dependently shifted fetoplacental PER2 rhythms; blocking glucocorticoid signaling reduced maternal-fetal synchrony.

Conclusions:

• * Daily circadian rhythms gradually develop in utero before birth.
• * These rhythms synchronize with the mother, potentially mediated by glucocorticoid signaling.
• * Proper establishment of in utero circadian rhythms may be essential for successful pregnancy.