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Laboratory of Reproductive Physiology and Biotechnology, Department of Animal and Marine Bioresource Sciences, Graduate School of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
¹ Molecular Medicine Research Labs, Drug Discovery Research, Astellas Pharma Inc., Miyukigaoka 21, Tsukuba-shi, Ibaraki 305-8585, Japan

(Requests for offprints should be addressed to M-a Hattori; Email: mhattori{at}agr.kyushu-u.ac.jp)

The circadian clock, regulating hormonal secretion and metabolisms in accordance with the environmental light–dark cycle, resides in almost all peripheral tissues as well as in the superchiasmatic nucleus. Clock gene expression has been found to be noncyclic during spermatogenesis and the differentiation of thymocytes. However, currently little is known about how cell differentiation could affect circadian clockwork. We performed this study using the in vitro real-time oscillation monitoring system to examine the clockwork in several types of differentiating cells originated from reproductive tissues of transgenic rats (constructed with Period gene 2 (Per2) promoter-destabilized luciferase reporter gene). After treatment with dexamethasone (DXM), persistent oscillation of Per2 expression was observed in both gonadotropin-induced and pregnant ovarian luteal cells, proliferative uterine stromal cells (USCs), and nondifferentiating testicular interstitial cells, with a cyclic period of ~24 h. In contrast to these cell types, only one cycle of oscillation was sustained in granulosa cells undergoing differentiation. Additionally, Per2 oscillation was irregular in USCs undergoing decidualization induced by medroxyprogesterone acetate plus N6, 2-O-dibutyryl adenosine 3':5'-cyclic monophosphate. Furthermore, no oscillation of Per2 expression was evoked by DXM in Leydig cells and thymocytes. In conclusion, the present study characterized the oscillation of Per2 gene expression in several types of ovarian, uterine, and testicular cells, and it is strongly suggested that circadian clockwork is affected during cellular differentiation.

This article has been cited by other articles:

				P.-J. He, M. Hirata, N. Yamauchi, and M.-a. Hattori Up-regulation of Per1 expression by estradiol and progesterone in the rat uterus J. Endocrinol., September 1, 2007; 194(3): 511 - 519. [Abstract] [Full Text] [PDF]