title: Circadian profiling of the transcriptome in NIH/3T3 fibroblasts: comparison with rhythmic gene expression in SCN2.2 cells and the rat SCN.
abstract: To screen for output signals that may distinguish the pacemaker in the mammalian suprachiasmatic nucleus (SCN) from peripheral-type oscillators in which the canonical clockworks are similarly regulated in a circadian manner, the rhythmic behavior of the transcriptome in forskolin-stimulated NIH/3T3 fibroblasts was analyzed and compared relative to SCN2.2 cells in vitro and the rat SCN. Similar to the circadian profiling of the SCN2.2 and rat SCN transcriptomes, NIH/3T3 fibroblasts exhibited circadian fluctuations in the expression of the core clock genes, Per2, Cry1, and Bmal1, and 323 functionally diverse transcripts, many of which regulate cellular communication. Overlap in rhythmic transcripts among NIH/3T3 fibroblasts, SCN2.2 cells, and the rat SCN was limited to these clock genes and four other genes that mediate fatty acid and lipid metabolism or function as nuclear factors. Compared with NIH/3T3 cells, circadian gene expression in SCN oscillators was more prevalent among genes mediating glucose metabolism and neurotransmission. Coupled with evidence for the rhythmic regulation of the inducible isoform of nitric oxide synthase (iNos) in SCN2.2 cells and the rat SCN but not in fibroblasts, studies examining the effects of a NOS inhibitor on metabolic rhythms in cocultures containing SCN2.2 cells and untreated NIH/3T3 cells suggest that the gaseous neurotransmitter nitric oxide may play a key role in SCN pacemaker function. This comparative analysis of circadian gene expression in SCN and non-SCN cells may have important implications in the selective analysis of circadian signals involved in the coupling of SCN oscillators and regulation of rhythmicity in downstream cells.
authors.affiliation: Department of Neuroscience and Experimental Therapeutics, Texas A&M University Health Science Center, College of Medicine, College Station, Texas 77843-1114, USA.
authors.forename: Gus J
authors.initials: GJ
authors.lastname: Menger
authors.forename: Gregg C
authors.initials: GC
authors.lastname: Allen
authors.forename: Nichole
authors.initials: N
authors.lastname: Neuendorff
authors.forename: Sang-Soep
authors.initials: SS
authors.lastname: Nahm
authors.forename: Terry L
authors.initials: TL
authors.lastname: Thomas
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Cassone
authors.forename: David J
authors.initials: DJ
authors.lastname: Earnest
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002940:Circadian Rhythm / Q000235:genetics*; D016000:Cluster Analysis; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects; D051379:Mice; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D041681:NIH 3T3 Cells; D009569:Nitric Oxide / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000032:analysis*; D051381:Rats; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D009569:Nitric Oxide; D019331:NG-Nitroarginine Methyl Ester