NCBI Summary:
This gene is a member of the Period family of genes and is expressed in a circadian pattern in the suprachiasmatic nucleus, the primary circadian pacemaker in the mammalian brain. Genes in this family encode components of the circadian rhythms of locomotor activity, metabolism, and behavior. Circadian expression in the suprachiasmatic nucleus continues in constant darkness, and a shift in the light/dark cycle evokes a proportional shift of gene expression in the suprachiasmatic nucleus. The specific function of this gene is not yet known.
General function
DNA binding, Transcription factor
Comment
Cellular localization
Nuclear
Comment
Ovarian function
Steroid metabolism
Comment
Circadian clock gene regulation of steroidogenic acute regulatory protein gene expression in pre-ovulatory ovarian follicles. Nakao N et al. It is now known that circadian clocks are localized not only in the central pacemaker but also in peripheral organs. An example of a clock-dependent peripheral organ is the ovary of domestic poultry where ovulation is induced by the positive feed-back action of ovarian progesterone on the neuroendocrine system to generate a pre-ovulatory release of LH during a daily 6-10 hr 'open period' of the ovulatory cycle. It has previously been assumed that the timing of ovulation in poultry is controlled solely by a clock-dependent mechanism within neuroendocrine system. Here, we question this assumption by demonstrating the expression of the clock genes, Per2 and 3, Clock and Bmal1 in pre-ovulatory follicles in laying quail. Diurnal changes in Per2 and 3 expression were seen in the largest pre-ovulatory follicle (F1), but not in smaller follicles. We next sought to identify clock-driven genes in pre-ovulatory follicles focusing on those involved in the synthesis of progesterone. One such gene was identified, encoding steroidogenic acute regulatory protein (StAR), which showed 24 hr changes in expression in the F1 follicle coinciding with those of Per2. Evidence that StAR gene expression is clock-driven was obtained by showing that its 5' flanking region contains E-box enhancers, which bind to CLOCK/BMAL1 heterodimers to activate gene transcription. We also showed that LH administration increased the promoter activity of chicken StAR. We therefore suggest that the timing of ovulation in poultry involves a LH- responsive F1 follicular clock that is involved in the timing of the pre-ovulatory release of progesterone.