Significant dissociation of expression patterns of the basic helix–loop–helix transcription factors Dec1 and Dec2 in rat kidney

Mar 25, 2011The Journal of experimental biology

Different activity patterns of the related gene regulators Dec1 and Dec2 in rat kidney

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Abstract

Daytime restricted feeding induced circadian expression of Dec1 in rat kidney with an amplitude of 4.2 on day 7.

Dec1 and Dec2 show different expression patterns in the rat kidney under normal light-dark cycles, with Dec1 exhibiting arrhythmic expression and Dec2 showing rhythmic expression.
Daytime restricted feeding significantly altered the expression of Dec1 and Dec2, leading to rhythmic expression of Dec1 after 7 days.
A reversed feeding schedule combined with a reversed light-dark cycle caused Dec1 to revert to arrhythmic expression, while Dec2 remained rhythmic.
Injection of the glucocorticoid analogue dexamethasone at specific times resulted in rhythmic expression of Dec1, comparable to the effects of daytime restricted feeding.
Endogenous disruption of glucocorticoids through adrenalectomy eliminated the rhythmic expression of Dec1 induced by daytime restricted feeding.

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Dec1 and Dec2 are regulators of the mammalian molecular clock that show robust circadian rhythms in the suprachiasmatic nucleus and various peripheral tissues. Although the expression of Dec1 and Dec2 is altered by multiple stimuli in different organs, their transcriptional regulatory mechanisms have not been fully elucidated for the kidney. In the present study, we describe for the first time significant dissociation of expression patterns with arrhythmic expression of Dec1 and rhythmic expression of Dec2 in rat kidney under a normal light-dark (LD) cycle. Daytime restricted feeding (RF) significantly altered the expression patterns of these two clock genes, and even induced circadian expression of Dec1 with an amplitude of 2.2 on day 3 and 4.2 on day 7. However, when a reversed feeding schedule was coupled with a reversed LD cycle, the expression of Dec1 but not Dec2 reverted to being arrhythmic. Moreover, exogenous injection of the glucocorticoid analogue dexamethasone (Dex) at certain times of the day resulted in rhythmic expression of Dec1, which was similar to that seen following RF for 7 days. In contrast, endogenous disruption of glucocorticoids by adrenalectomy abolished RF-induced rhythmic expression of Dec1 in the kidney. These observations suggest the existence of a glucocorticoid gating mechanism in the circadian expression of Dec1 in rat kidney.

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Significant dissociation of expression patterns of the basic helix–loop–helix transcription factors Dec1 and Dec2 in rat kidney

Abstract

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