The ovary knows more than you think! New views on clock genes and the positive feedback control of luteinizing hormone.

The molecular revolution in recent decades has transformed many areas of systems physiology. Perhaps in no field has the impact been more significant than in the area of biological clocks. The great success story in this case has been the discovery of clock genes that through a process of coordinated feedback between transcription and translation are able to produce an oscillation that controls many forms of circadian behaviors (1, 2). The paper by Nakao et al. (3) that appears in this issue illustrates clearly how studies based on clock gene expression have the potential to transform our thinking about a classic problem in reproductive neuroendocrinology, in this case the mechanisms controlling the positive feedback of ovarian steroid hormones on LH secretion that results in the LH surge needed for ovulation. To appreciate the significance of this paper, a bit of background on clocks and clock genes should be provided first.