Molecular mechanisms regulating animal seasonal breeding in response to changing photoperiod are not well understood. Rapid induction of gene expression of thyroid-hormone-activating enzyme (type 2 deiodinase, DIO2) in the mediobasal hypothalamus (MBH) of the Japanese quail (Coturnix japonica) is the earliest event yet recorded in the photoperiodic signal transduction pathway. Here we show cascades of gene expression in the quail MBH associated with the initiation of photoinduced secretion of luteinizing hormone. We identified two waves of gene expression. The first was initiated about 14 h after dawn of the first long day and included increased thyrotrophin (TSH) beta-subunit expression in the pars tuberalis; the second occurred approximately 4 h later and included increased expression of DIO2. Intracerebroventricular (ICV) administration of TSH to short-day quail stimulated gonadal growth and expression of DIO2 which was shown to be mediated through a TSH receptor-cyclic AMP (cAMP) signalling pathway. Increased TSH in the pars tuberalis therefore seems to trigger long-day photoinduced seasonal breeding.

The circadian clock is a fundamental property of living organisms and is involved in seasonal (photoperiodic) time measurement. Among vertebrates, birds have multiple circadian pacemakers in the eye, the pineal gland, and the suprachiasmatic nucleus (SCN), and have highly sophisticated photoperiodic mechanisms. However, because the removal of these circadian pacemakers fails to abolish the photoperiodic response, the existence of another "photoperiodic clock" has been suggested. Recent studies have revealed that the mediobasal hypothalamus (MBH) and the adjacent pars tuberalis (PT) of the pituitary gland constitute key components of the photoperiodic signal transduction machinery. In the present study, we generated a polyclonal antibody against the chicken circadian clock protein BMAL1 to examine BMAL1 distribution in the Japanese quail brain by using immunohistochemistry. BMAL1-like immunoreactivity (lir) was confirmed in the pineal gland and the medial SCN, which are critical circadian pacemakers. We also observed strong immunoreactivity in the MBH, including the ependymal cells (ECs), the infundibular nucleus (IN), the median eminence (ME), and the adjacent PT. Furthermore, semiquantitative analysis suggested that BMAL1-lir shows daily fluctuation in these regions. It is possible that circadian clocks in the photoperiodic signal transduction machinery such as the PT and the EC may be involved in the regulation of photoperiodism.

Elevated expression of the nucleoporin Nup88, a constituent of the nuclear pore complex, is seen in various types of malignant tumors, but whether this overexpression contributes to the malignant phenotype has yet to be determined. Here, we investigated the effect of the overexpression of Nup88 on the migration and invasion of cervical cancer HeLa cells. The overexpression of Nup88 promoted a slight but significant increase in both migration and invasion, whereas knockdown of Nup88 by RNA interference suppressed these phenotypes. The observed phenotypes in Nup88-overexpressing HeLa cells were not due to the progression of the epithelial-to-mesenchymal transition or activation of NF-κB, which are known to be important for cell migration and invasion. Instead, we identified an upregulation of matrix metalloproteinase-12 (MMP-12) at both the gene and protein levels in Nup88-overexpressing HeLa cells. Upregulation of MMP-12 protein by the overexpression of Nup88 was also observed in one other cervical cancer cell line and two prostate cancer cell lines but not 293 cells. Treatment with a selective inhibitor against MMP-12 enzymatic activity significantly suppressed the invasive ability of HeLa cells induced by Nup88 overexpression. Taken together, our results suggest that overexpression of Nup88 can stimulate malignant phenotypes including invasive ability, which is promoted by MMP-12 expression.

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