PKCγ participates in food entrainment by regulating BMAL1.

Temporally restricted feeding (RF) can phase reset the circadian clocks in numerous tissues in mammals, contributing to altered timing of behavioral and physiological rhythms. However, little is known regarding the underlying molecular mechanism. Here we demonstrate a role for the gamma isotype of protein kinase C (PKCγ) in food-mediated entrainment of behavior and the molecular clock. We found that daytime RF reduced late-night activity in wild-type mice but not mice homozygous for a null mutation of PKCγ (PKCγ(-/-)). Molecular analysis revealed that PKCγ exhibited RF-induced changes in activation patterns in the cerebral cortex and that RF failed to substantially phase shift the oscillation of clock gene transcripts in the absence of PKCγ. PKCγ exerts effects on the clock, at least in part, by stabilizing the core clock component brain and muscle aryl hydrocarbon receptor nuclear translocator like 1 (BMAL1) and reducing its ubiquitylation in a deubiquitination-dependent manner. Taken together, these results suggest that PKCγ plays a role in food entrainment by regulating BMAL1 stability.

The expression pattern of three mast cell specific proteases during mouse development.

Mast cell chymases and tryptases are major constituents of mast cell granules exhibiting an intriguing but potentially confusing variety of forms and functions. Thanks to recent genetic and biochemical advances, a clearer picture of phylogenetic and functional relationships in this large group of mammalian enzymes is emerging. While different in vivo and in vitro studies characterize the function of these proteases in adult tissues, only sparse information is available about these enzymes during embryogenesis. In the present study, we followed the expression patterns of three different mast cell proteases--mcpt5 (chymase), mcpt6 and 7 (tryptases)--during the development of the mouse embryo. Using specific probe sets for Northern blot analysis, nested PCR and in situ hybridization we describe the expression patterns of the three proteases in different stages of the developing embryo. Furthermore, we try to localize the expression pattern of the three proteases to a certain region and subset of cells. Based on the spatial and temporal expression patterns of mcpt5, 6 and 7 we hypothesize that these molecules play specific and distinct roles in the prenatal and postnatal stages.

The circadian rhythm of glucocorticoids is regulated by a gating mechanism residing in the adrenal cortical clock.

In mammals, the master clock of the suprachiasmatic nuclei (SCN) and subordinate clocks found throughout the body coordinate circadian rhythms of behavior and physiology. We characterize the clock of the adrenal, an important endocrine gland that synchronizes physiological and metabolic rhythms. Clock gene expression was detected in the outer adrenal cortex prefiguring a role of the clock in regulating gluco- and mineral corticoid biogenesis. In Per2/Cry1 double mutant mice, which lack a circadian clock, hypothalamus/pituitary/adrenal axis regulation was defective. Organ culture and tissue transplantation suggest that the adrenal pacemaker gates glucocorticoid production in response to adrenocorticotropin (ACTH). In vivo the adrenal circadian clock can be entrained by light. Transcriptome profiling identified rhythmically expressed genes located at diverse nodes of steroid biogenesis that may mediate gating of the ACTH response by the adrenal clock.

Restoration of circadian rhythmicity in circadian clock-deficient mice in constant light.

In mammals, circadian rhythms in behavior and physiology are controlled by a central pacemaker, the SCN, and subordinated clocks throughout the body. On the molecular level, these clocks are based on transcriptional/translational feedback loops involving a set of clock genes that regulate their own transcription. Among the components driving the mammalian circadian clock are the Period 1 and 2 (Per1 and Per2) and Cryptochrome 1 and 2 (Cry1 and Cry2) genes. In the present study, the authors characterize the behavioral and molecular rhythms of Per2/Cry1 double mutant mice under 3 different lighting conditions. In an LD cycle, the activity of these animals is masked by light, while in DD, the mutants lose circadian rhythmicity but exhibit strong ultradian rhythms. In LL of higher intensity, circadian rhythms are restored on the behavioral level with a drastically shortened endogenous period. Furthermore, both in the SCN and in the periphery, clock gene rhythms are restored. Based on these observations and also on the fact that light-mediated induction of Per gene expression is preserved in these mutants, the authors propose a mechanism by which endogenous ultradian rhythms may relay timed light exposure to the SCN, leading to a reinitiation of self-sustained circadian rhythms in LL.

Expression of the protein kinase D (PKD) family during mouse embryogenesis.

The serine/threonine protein kinase D (PKD) family comprises of three members, PKD1 (PKCmu), PKD2 and PKD3 (PKCnu). Like the related C-type protein kinases (PKCs), PKDs are activated by diacylglycerol (DAG). PKDs have been implicated in numerous intracellular signaling pathways including vesicular transport, cell proliferation, survival, migration and immune responses. While experimental data on this recently discovered kinase family are starting to accumulate family member specific information is still sparse and only small effort has been taken to functionally differentiate the three PKDs. To address this issue we followed the expression patterns of PKD1, 2 and 3 during the development of the mouse embryo. Using specific probe sets for RT-PCR and in situ hybridization, we demonstrate shared and differential expression domains for the three PKD family members in both neuronal and non-neuronal tissues.