Rhythmic expression of clock and clock-controlled genes in the rat oviduct

Abstract

The rhythmic expression of clock and clock-controlled genes in the rat oviduct was investigated by real time RT±PCR. per1, per2, Clock, Bmal1, cry1 and cry2 were all expressed in the oviduct. With 4-hourly sampling over 24 h in a normal photoperiod, analysis of variance indicated that per2 and Bmal1 had highly signi®cant sinusoidal-like changes with an amplitude of 3- and 10-fold respectively. Of the other clock genes, per1 and cry1 had non-signi®cant rhythm amplitudes of 2.5- and 1.8-fold respectively. Using the same experimental approach the rhythmic expression of Bmal1, per1 and per2 mRNA in the liver was found to be highly signi®cant with amplitudes of approximately 20-, 10- and 5-fold respectively. The expression of the clock-controlled transcription factors DBP and Rev-erb a showed signi®cant rhythmicity in the oviduct with 5-fold changes in amplitude for both genes. Plasminogen activator inhibitor-1 (PAI-1), which has been implicated in oviduct function during the preimplantation period, also had a signi®cant rhythm of expression (2.5-fold amplitude), peaking at the same time as the other clock-controlled genes, DBP and Rev-erb a. These results show for the ®rst time that the female reproductive tract is inherently rhythmic and suggests that the developing embryo may be subjected to rhythmic changes in the environment created by the oviduct during transition to the uterus.