Abstract
BackgroundThe master clock within the hypothalamic suprachiasmatic nucleus (SCN) synchronizing clocks in peripheral tissues is entrained by the environmental condition, such as the light-dark (LD) cycle. The mechanisms of circadian clockwork are similar in both SCN and peripheral tissues. The aim of the present work was to observe the profiles of clock genes expression in mouse central and peripheral tissues within postnatal day 5 (P5). The daily expression of four clock genes mRNA (Bmal1, Per2, Cry1 and Rev-erb alpha) in mouse SCN and heart was measured at P1, P3 and P5 by real-time PCR.ResultsAll the studied mice clock genes began to express in a circadian rhythms manner in heart and SCN at P3 and P5 respectively. Interestingly, the daily rhythmic phase of some clock genes shifted during the postnatal days. Moreover, the expressions of clock genes in heart were not synchronized with those in SCN until at P5.ConclusionThe data showed the gradual development of clock genes in SCN and a peripheral tissue, and suggested that development of clock genes differed between in the SCN and the heart. Judging from the mRNA expression, it was possible that the central clock synchronized the peripheral clock as early as P5.
Highlights
In mammals, the circadian pacemaker is in the hypothalamic suprachiasmatic nucleus (SCN), which regulates most physiological and behavioral circadian rhythms with a period of approximately 24 hours [1,2]
For Rev-erba mRNA expression, the level at ZT0 was significantly higher than ZT4, ZT8, ZT12 (P < 0.01) and ZT16 (P < 0.05)
For Per2, there was no clear circadian rhythm, the one-way ANOVA revealed some variation throughout the day, it’s level at ZT16 was higher than those at ZT4, ZT8, ZT12 and ZT20 (P < 0.05)
Summary
The circadian pacemaker is in the hypothalamic suprachiasmatic nucleus (SCN), which regulates most physiological and behavioral circadian rhythms with a period of approximately 24 hours [1,2]. The master circadian system is mainly entrained to the 24-h day by light-dark (LD) cycle [3]. The SCN synchronizes the peripheral clocks via incompletely understood nervous and humoral signals so that they achieve optimal phase relationships in daily environmental cycle [6,7,8]. The master clock within the hypothalamic suprachiasmatic nucleus (SCN) synchronizing clocks in peripheral tissues is entrained by the environmental condition, such as the light-dark (LD) cycle. The aim of the present work was to observe the profiles of clock genes expression in mouse central and peripheral tissues within postnatal day 5 (P5). The daily expression of four clock genes mRNA (Bmal, Per, Cry and Rev-erb alpha) in mouse SCN and heart was measured at P1, P3 and P5 by real-time PCR
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