Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling of rat pineal Expt C

ABSTRACT: Biological processes are optimized by circadian and circannual biological timing systems. In vertebrates, the pineal gland plays an essential role in these systems by converting time into a hormonal signal, melatonin; in all vertebrates, circulating melatonin is elevated at night, independent of lifestyle. At night, sympathetic input to the pineal gland, originating from the circadian clock in the suprachiasmatic nucleus, releases norepinephrine. This adrenergic stimulation causes an elevation of cAMP, which is thought to regulate many of the dramatic changes in genes expression known to occur at night. In many aspects, the adrenergic/cAMP effects on gene expression can be recapitulated in primary organ culture. We have analyzed the rat pineal transcriptome at mid-day and mid-night to identify genes that exhibit night/day changes in expression. The pineal transcriptome was compared to that of other rat tissues processed in parallel. In addition, pineal glands were cultured in control conditions, or stimulated with norepinephrine, dibutyryl-cAMP (DBcAMP), or forskolin; the transcriptomes of these glands were then analyzed. Experiment Overall Design: Total RNA was extracted from various rat tissues, and from both in vivo and cultured rat pineal glands, for processing and hybridization to Affymetrix microarrays. Quadruplicates of pooled in vivo pineal glands were analyzed at each timepoint. Single day and night samples of retina, cortex, cerebellum, hypothalamus, liver, and heart were analyzed. Triplicates of control and treated cultured pineal glands were analyzed.

ORGANISM(S): Rattus norvegicus

SUBMITTER: David Klein

PROVIDER: E-GEOD-12343 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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.

Project description:The cone-rod homeobox gene (Crx) encodes Crx, a transcription factor selectively expressed in two cell types, retinal photoreceptors and the melatonin secreting pinealocytes of the pineal gland. In this report the role of Crx in regulating gene expression in the mammalian pineal gland was extended using Affymetrix GeneChip technology. Deletion of Crx results in broad modulation of the mouse pineal transcriptome, including a >2-fold downregulation of 543 genes and a >2-fold upregulation of 745 genes. In addition to Crx, there was a >10-fold downregulation of 13 other genes. Of special interest was the discovery of a link between Crx and the homeobox gene Hoxc4, which was upregulated ~20-fold in the Crx-/- pineal gland. Analysis of night and day expression of genes indicated that a set of 51 genes exhibited differential expression in control animals. Of these genes, only eight were also differentially expressed in Crx-/- animals. This group included Aanat, which encodes the enzyme that controls the daily rhythm in melatonin synthesis in the vertebrate pineal gland. Accordingly, Crx appears to be essential for the 24-hour rhythmic component of expression of some genes in the pineal gland. In the Crx-/- mouse pineal gland, 41 genes exhibited differential night/day expression that was not seen in control animals, suggesting that Crx may function to modulate rhythmic expression of these genes as well. Together, the results of this investigation indicate that Crx broadly modulates the pineal transcriptome, perhaps in part through suppressive effects on expression of the homeobox gene Hoxc4. Pineal glands from control (129sv) mice and Crx-/- mice were collected at ZT6 and ZT20 for RNA extraction and hybridization on Affymetrix mouse 430_2 chip. Each condition were performed as triplicats. SUPPLEMENTARY FILES: The GCOS signal intensity data were analyzed using ChipInspector (Genomatix) version 2.1. FDR= 0, p-value <0.05, cut off=1, region size = 300 bp and 4 and 5 significant probes. Log(2) fold change independently of time of day. Up regulated genes: genes which are up regulated in Crx-/- compared to the control; down regulated genes: genes which are down regulated in Crx-/- compared to the control.

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Transcription profiling of rat pineal Expt C

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