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Circadian Transcriptome of the Chicken Pineal In Vitro

ABSTRACT: Chick pinealocytes exhibit all the characteristics of a complete circadian system, comprising photoreceptive inputs, molecular clockworks and an easily measured rhythmic output, melatonin biosynthesis. We used microarray analysis to investigate the expression of approximately 8000 genes within cultured pinealocytes subjected to both LD and DD cycles. We report that a reduced subset of genes were rhythmically expressed in vitro compared to those previously published in vivo, and that gene expression rhythms were lower in amplitude, although the functional distribution of the rhythmic transcriptome was largely similar. We also investigated the effects of 6-hour pulses of light or of norepinephrine on gene expression in free-running cultures during both subjective day and night. As expected, both light and norepinephrine inhibited melatonin production; however, the two treatments differentially up- or down-regulated specific sets of genes in a fashion that was dependent upon time of day. Our combined approach of utilizing a time of day study and a light/NE pulse microarray experiment allowed us to identify novel genes linking clock input to clock function within the pineal. We identified approximately 30 rhythmic, light-responsive, NE-insensitive genes with no previously known clock function, which may play a role in circadian regulation of the pineal. These are candidates for future functional genomics experiments to elucidate their potential role in pineal physiology. Keywords: circadian; avian; pineal; light; norepinephrine Microarray analysis was performed on pineal samples subjected to one of four experimental groups: cultures placed within a 12-hour light:12-hour dark cycle (LD); cultures placed in continuous darkness (DD); cultures subjected to a 6-hour light pulse beginning at either CT0 or CT12 (i.e., zero or 12 hours after the beginning of subjective day) or that received no light pulse; and cultures subjected to 6 hours of NE treatment beginning at either CT0 or CT12 or that received similarly administered vehicle. For LD and DD groups, time-course sampling was performed such that 6 samples were collected over the course of a day at 4-hour intervals. For the light pulse and NE administration groups, 2 samples were collected over the course of a day, either at CT6 or CT18 (i.e., 6 or 18 hours after the beginning of subjective day). Four biological replicates and two technical replicates (for each biological repeat) were performed for each sample. For the LD and DD groups, time-points ZT18 and CT18 served as the control reference for the time-course analysis. For the light pulse experiment, cultures that did not receive light served as the control. For the NE administration experiment, cultures that received vehicle served as the control. Dye swaps for performed for experimental samples from the light pulse and NE administration experiments.

ORGANISM(S): Gallus gallus

SUBMITTER: Stephen Karaganis

PROVIDER: E-GEOD-5292 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Circadian genomics of the chick pineal gland in vitro.

Karaganis Stephen P SP Kumar Vinod V Beremand Phillip D PD Bailey Michael J MJ Thomas Terry L TL Cassone Vincent M VM

BMC genomics 20080503

<h4>Background</h4>Chick pinealocytes exhibit all the characteristics of a complete circadian system, comprising photoreceptive inputs, molecular clockworks and an easily measured rhythmic output, melatonin biosynthesis. These properties make the in vitro pineal a particularly useful model for exploring circadian control of gene transcription in a pacemaker tissue, as well as regulation of the transcriptome by primary inputs to the clock (both photic and noradrenergic).<h4>Results</h4>We used mi ...[more]

PMID: 18454867

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Project description:There is growing appreciation that the feeling of well-being, alterations in mood and susceptibility to a variety of medical disorders depend on the proper expression of the master circadian clock and the synchrony among the other oscillators found in many peripheral tissues. To improve our understanding of the role of peripheral oscillators, an improved understanding of the molecular machinery sub-serving the circadian variation in gene expression is essential. Our long-term goal is to understand the molecular mechanisms that initiate circadian gene expression following external stimulation in the mammalian pineal gland. Are all or just some of the "circadian clock" genes induced by NE, cAMP, or cGMP? In this project we compare a series of gene expression patterns using DNA microarray in response to cAMP, cGMP and NE stimulation to understand why NE does not initiate circadian rhythms in the rat pineal gland. As a preliminary experiment we will compare gene expression 0, 1, and 4 h after start of chemical stimulation. A failure of NE to initiate circadian rhythms is due to failure of activation of certain "circadian clock" genes. We found that circadian rhythms are initiated by stimulation of cAMP or cGMP analogue in the rat pineal gland, while norepinephrine (NE) stimulation only moderately induce Period1 mRNA (one of "circadian clock" genes) 24 h after start of stimulation. From these results we hypothesize that external stimulation activates some "circadian clock" genes simultaneously, and that failure of circadian rhythm initiation following NE stimulation is due to insufficient "circadian clock" genes activations. Male rats of wistar strain are kept in 12h-12h light dark cycles at least for one week before start of experiments. Pineal glands are removed from animals and placed in the culture dish. Rat pineal glands are cultured for 3 days before chemical stimulation. On the day of experiment, the pineal cultures are stimulated using one of NE, cAMP and cGMP analogues for 1 or 4 h before harvest. The samples are immediately frozen and total RNA are extracted from each group which are from a pool of 8 pineal glands using Trizol reagent (Invitrogen). Concentrations of total RNA are determined using spectrophotometer, and six microgram of total RNA is aliquoted in each sample tube for further analysis. Since we already have Affymetrix Rat Genome U34A array GeneChips, we would like to send Chips as well as our total RNA samples. Experiment Overall Design: as above

Project description:Pineal function follows a 24-hour schedule, dedicated to the conversion of night and day into a hormonal signal, melatonin. In mammals, 24-hour changes in pineal activity are controlled by a neural pathway that includes the central circadian oscillator in the suprachiasmatic nucleus and the superior cervical ganglia (SCG), which innervate the pineal gland. In this study, we have generated the first next-generation RNA sequencing evidence of neural control of the daily changes in the pineal transcriptome. We found over 3000 pineal transcripts that are differentially expressed (p <0.001) on a night/day basis (70% of these genes increase at night, 376 with fold change >4 or <1/4), the majority of which had not been previously identified as such. Nearly all night/day differences were eliminated by neonatal removal or decentralization of the SCG, confirming the importance of neural input for differential night/day changes in transcript abundance. In contrast, very few non-rhythmic genes showed evidence of changes in expression due to the surgical procedure itself, which is consistent with the hypothesis that post neonatal neural stimulation is not required for cell fate determination and maintenance of phenotype. Many of the transcripts that exhibit marked differential night/day expression exhibited similar changes in response to in vitro treatment with norepinephrine, the SCG neurotransmitter which mediates pineal regulation. Similar changes were also seen following treatment with an analog of the norepinephrine second messenger, cyclic AMP. For the in vivo data, there were 8 biological conditions: day and night time points for each of four surgical groups: Control (Ctrl) Sham-surgery (Sham), Decentralized (DCN), and Ganglionectomized (SCGX). Samples were pooled into three biological replicates for each biological condition. For the in vitro data there were 3 biological conditions: Untreated control (CN), DBcAMP-treated (DB), and Norepinephrine-treated (NE). For the pineal enrichment comparison, three samples (i.e. no biological replicates) were used: pineal-day, pineal-night and mixed-tissue. For the mixed tissues sample, the following tissues from three rats sacrificed at ZT7 were used: cortex, cerebellum, midbrain, hypothalamus, hindbrain, spinal cord, retina, pituitary, heart, liver, lung, kidney, skeletal muscle, small intestine, adrenal gland. Total RNA was extracted from each tissue, and then equal amounts of each of the 15 tissues were combined for the final pooled sample.

Dataset Information

Circadian Transcriptome of the Chicken Pineal In Vitro

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Circadian genomics of the chick pineal gland in vitro.

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