Using a forward genetics ENU mutagenesis screen for recessive mutations that affect circadian rhythmicity in the mouse, we isolated a long period (approximately 26 hr) circadian mutant named Overtime (Ovtm). Positional cloning and genetic complementation reveal that Ovtm is encoded by the F-box protein FBXL3, a component of the SKP1-CUL1-F-box-protein (SCF) E3 ubiquitin ligase complex. The Ovtm mutation causes an isoleucine to threonine (I364T) substitution leading to a loss of function in FBXL3, which interacts specifically with the CRYPTOCHROME (CRY) proteins. In Ovtm mice, expression of the PERIOD proteins PER1 and PER2 is reduced; however, the CRY proteins CRY1 and CRY2 are unchanged. The loss of FBXL3 function leads to a stabilization of the CRY proteins, which in turn leads to a global transcriptional repression of the Per and Cry genes. Thus, Fbxl3(Ovtm) defines a molecular link between CRY turnover and CLOCK/BMAL1-dependent circadian transcription to modulate circadian period.

We recently described an erythroid e-globin gene repressor activity, which we named DRED (direct repeat erythroid-de®nitive). We show that DRED binds with high af®nity to DR1 sites in the human embryonic (e-) and fetal (g-) globin gene promoters, but the adult b-globin promoter has no DR1 element. DRED is a 540 kDa complex; sequence determination showed that it contains the nuclear orphan receptors TR2 and TR4. TR2 and TR4 form a heterodimer that binds to the e and g promoter DR1 sites. One mutation in a DR1 site causes elevated g-globin transcription in human HPFH (hereditary persistence of fetal hemoglobin) syndrome, and we show that this mutation reduces TR2/TR4 binding in vitro. The two receptor mRNAs are expressed at all stages of murine and human erythropoiesis; their forced transgenic expression reduces endogenous embryonic ey-globin transcription. These data suggest that TR2/TR4 forms the core of a larger DRED complex that represses embryonic and fetal globin transcription in de®nitive erythroid cells, and therefore that inhibition of its activity might be an attractive intervention point for treating sickle cell anemia.

Body weight is regulated by interoceptive neural circuits that track energy need, but how the activity of these circuits is altered in obesity remains poorly understood. Here we describe the in vivo dynamics of hunger-promoting AgRP neurons during the development of diet-induced obesity in mice. We show that high-fat diet attenuates the response of AgRP neurons to an array of nutritionally-relevant stimuli including food cues, intragastric nutrients, cholecystokinin and ghrelin. These alterations are specific to dietary fat but not carbohydrate or protein. Subsequent weight loss restores the responsiveness of AgRP neurons to exterosensory cues but fails to rescue their sensitivity to gastrointestinal hormones or nutrients. These findings reveal that obesity triggers broad dysregulation of hypothalamic hunger neurons that is incompletely reversed by weight loss and may contribute to the difficulty of maintaining a reduced weight.

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The mechanism of circadian oscillations in mammals is cell autonomous and is generated by a set of genes that form a transcriptional autoregulatory feedback loop. While these “clock genes” are well conserved among animals, their specific functions remain to be fully understood and their roles in central versus peripheral circadian oscillators remain to be defined. We utilized the in vivo inducible tetracycline-controlled transactivator (tTA) system to regulate Clock gene expression conditionally in a tissue-specific and temporally controlled manner. Through the use of Secretogranin II to drive tTA expression, suprachiasmatic nucleus– and brain-directed expression of a tetO::ClockΔ19 dominant-negative transgene lengthened the period of circadian locomotor rhythms in mice, whereas overexpression of a tetO::Clockwt wild-type transgene shortened the period. Low doses (10 μg/ml) of doxycycline (Dox) in the drinking water efficiently inactivated the tTA protein to silence the tetO transgenes and caused the circadian periodicity to return to a wild-type state. Importantly, low, but not high, doses of Dox were completely reversible and led to a rapid reactivation of the tetO transgenes. The rapid time course of tTA-regulated transgene expression demonstrates that the CLOCK protein is an excellent indicator for the kinetics of Dox-dependent induction/repression in the brain. Interestingly, the daily readout of circadian period in this system provides a real-time readout of the tTA transactivation state in vivo. In summary, the tTA system can manipulate circadian clock gene expression in a tissue-specific, conditional, and reversible manner in the central nervous system. The specific methods developed here should have general applicability for the study of brain and behavior in the mouse.

Background/Aims: It is well established that many non-trophoblastic tumors secrete HCG (human chorionic gonadotropin) and that such secretion is correlated with the poor prognosis of tumor patients. This study aims to analyze the correlation between β-HCG expression and outcome of colorectal cancer (CRC) and understand its role in CRC pathology Methods: We detected the mRNA and protein expression of β-HCG in human CRC tissues with RT-qPCR and immunohistochemistry, and we compared the clinical-pathological characteristics, prognosis and progression between the β-HCG positive and negative groups. We also generated CRC cell lines with β-HCG over-expression as well as β-HCG stable knockout, and evaluated cell function and mechanism in vitro and in vivo. Results: Fifty out of 136 CRC patients (37%) expressed β-HCG at the invasive front. Clinical-pathological data showed that β-HCG was positively correlated with Dukes staging (P=0.031) and lymph node metastasis (P=0.012). Survival analysis suggested that the patients with high expression of β-HCG had poorer prognosis than those with low β-HCG expression (P=0.0289). β-HCG expression level was also positively correlated with tumor invasion in early-stage CRC patient tissues (P=0.0227). Additionally β-HCG promoted the migration and invasion of CRC in vitro and in vivo but had no effect on the proliferation of tumor cells. Conclusion: Our study demonstrated that β-HCG was ectopically expressed in the CRC patients and its high expression correlated with poor prognosis of early-stage CRC. Additionally it worked as an oncogene that promotes the migration and invasion of CRC by epithelial-mesenchymal transition (EMT).

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