Circadian clocks regulate numerous physiological processes that vary across the day-night (diurnal) cycle, but if and how the circadian clock regulates the adaptive immune system is mostly unclear. Interleukin-17-producing CD4+ T helper (Th17) cells are proinflammatory immune cells that protect against bacterial and fungal infections at mucosal surfaces. Their lineage specification is regulated by the orphan nuclear receptor RORγt. We show that the transcription factor NFIL3 suppresses Th17 cell development by directly binding and repressing the Rorγt promoter. NFIL3 links Th17 cell development to the circadian clock network through the transcription factor REV-ERBα. Accordingly Th17 lineage specification varies diurnally and is altered in Rev-erbα−/− mice. Light cycle disruption elevated intestinal Th17 cell frequencies and increased susceptibility to inflammatory disease. Thus, lineage specification of a key immune cell is under direct circadian control.

Summary The liver plays a pivotal role in metabolism and xenobiotic detoxification, processes that must be particularly efficient when animals are active and feed. A major question is how the liver adapts to these diurnal changes in physiology. Here, we show that, in mice, liver mass, hepatocyte size, and protein levels follow a daily rhythm, whose amplitude depends on both feeding-fasting and light-dark cycles. Correlative evidence suggests that the daily oscillation in global protein accumulation depends on a similar fluctuation in ribosome number. Whereas rRNA genes are transcribed at similar rates throughout the day, some newly synthesized rRNAs are polyadenylated and degraded in the nucleus in a robustly diurnal fashion with a phase opposite to that of ribosomal protein synthesis. Based on studies with cultured fibroblasts, we propose that rRNAs not packaged into complete ribosomal subunits are polyadenylated by the poly(A) polymerase PAPD5 and degraded by the nuclear exosome.

The RNA-binding protein fused-in-sarcoma (FUS) has been associated with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD), two neurodegenerative disorders that share similar clinical and pathological features. Both missense mutations and overexpression of wild-type FUS protein can be pathogenic in human patients. To study the molecular and cellular basis by which FUS mutations and overexpression cause disease, we generated novel transgenic mice globally expressing low levels of human wild-type protein (FUS WT ) and a pathological mutation (FUS R521G A myotrophic lateral sclerosis (ALS) is characterized by the degeneration of upper and lower motor neurons, leading to muscle weakness, paralysis, and death within 3-5 y of onset. Interestingly, ∼10-15% of ALS patients have clinical features of frontotemporal lobar degeneration (FTLD), marked by a decline in decision-making, behavioral control, emotion, and language, and as many as half have mild-to-moderate cognitive or behavioral abnormalities (1). FTLD comprises a group of heterogeneous diseases characterized by progressive neurodegeneration of the frontal and temporal lobes and clinically by frontotemporal dementia (FTD) with or without motor neuron disease. There is no cure or effective therapy for those who suffer from ALS or FTLD, and the mechanisms by which these diseases occur are not well understood.The clinical, pathological, and genetic overlap between ALS and FTLD suggests that there are mechanisms shared by these diseases. The RNA-binding proteins fused in sarcoma (FUS) and transactive response DNA-binding protein-43 (TDP-43) are the major protein components of inclusions that are characteristic of ALS and FTLD-U (FTLD with ubiquitinated inclusions) (2). More than 50 genetic FUS mutations have been identified in these related neurodegenerative disorders (3). Similarly, more than 40 dominant mutations in the TDP-43 gene have been linked to ALS cases and, to a lesser extent, to FTLD (4). The identification of mutations in the FUS and TDP-43 genes has provided insights for uncovering the disease mechanisms for ALS and FTLD.FUS is a ubiquitously expressed RNA-binding protein that exists in dynamic ribonucleoprotein complexes involved in pre-mRNA splicing, mRNA stability, and mRNA transport. FUS is a member of the FET family of proteins that bind RNAs (5) and contains an RNA recognition motif, three arginine-glycine-glycine (RGG) boxes, and a zinc finger (ZnF) (6). RGG2-ZnF-RGG3 is the major RNA-binding domain, which has a preference for GUrich sequences (7,8). The N terminus of FUS contains a lowcomplexity sequence domain involved in RNA granule formation (9). Nucleocytoplasmic shuttling of FUS occurs by a nonclassical proline-tyrosine nuclear localization signal (PY-NLS) and a nuclear export signal (NES) (10). Methylation of the C-terminal RGG3 domain of FUS is necessary for transportin 1 interaction and nuclear localization (11).The majority of clinical ALS/FTLD-associated FUS mutations occur in its C-terminal PY-NLS seque...

Many aspects of metabolism exhibit daily rhythmicity under the control of endogenous circadian clocks, and disruptions in circadian timing result in dysfunctions associated with the metabolic syndrome. Nocturnin (Noc) is a robustly rhythmic gene that encodes a deadenylase thought to be involved in the removal of polyA tails from mRNAs. Mice lacking the Noc gene display resistance to diet-induced obesity and hepatic steatosis, due in part to reduced lipid trafficking in the small intestine. In addition, Noc appears to play important roles in other tissues and has been implicated in lipid metabolism, adipogenesis, glucose homeostasis, inflammation and osteogenesis. Therefore, Noc is a potential key post-transcriptional mediator in the circadian control of many metabolic processes.

SUMMARYThe timing of food intake and nutrient utilization is critical to health and regulated partly by the circadian clock. Increased amplitude of circadian oscillations and metabolic output has been found to improve health in diabetic and obesity mouse models. Here, we report a function for the circadian deadenylase Nocturnin as a regulator of metabolic amplitude across the day/night cycle and in response to nutrient challenge. We show that mice lacking Nocturnin (Noct−/−) display significantly increased amplitudes of mRNA expression of hepatic genes encoding key metabolic enzymes regulating lipid and cholesterol synthesis, both over the daily circadian cycle and in response to fasting and refeeding. Noct−/− mice have increased plasma triglyceride throughout the night and increased amplitude of hepatic cholesterol levels. Therefore, posttranscriptional control by Nocturnin regulates the amplitude of these critical metabolic pathways, and loss of this activity results in increased metabolic flux and reduced obesity.