title: Changes in expression level of genes as a function of time of day in the liver of rats.
abstract: Daily, rhythmic variation in various biochemical, physiological, and behavioral events is a fundamental property of biological organization. Here, we report analysis of relative levels of gene expression in the liver of 16 Fischer 344 rats as a function of time of day. Expression levels were determined for 3906 genes using high-density oligonucleotide microarrays. Of the 3906 genes, 1171 (30%) were clearly expressed while 2735 (70%) were not expressed or the expression was too low to distinguish from background levels. The maximum estimated changes observed for most genes (1029, 88%) were less than 1.5-fold. Analysis of variance and the Kruskal-Wallis tests were used to identify 67 genes whose expression was significantly altered as a function of time of day. These significantly altered genes were classified according to their functions and fall into key cellular pathways including drug metabolism, ion transport, signal transduction, DNA binding and regulation of transcription, and immune response.
authors.affiliation: Center for Functional Genomics, National Center for Toxicological Research, US FDA, Jefferson, AR, USA. vdesai@nctr.fda.gov
authors.forename: Varsha G
authors.initials: VG
authors.lastname: Desai
authors.forename: Carrie L
authors.initials: CL
authors.lastname: Moland
authors.forename: William S
authors.initials: WS
authors.lastname: Branham
authors.forename: Robert R
authors.initials: RR
authors.lastname: Delongchamp
authors.forename: Hong
authors.initials: H
authors.lastname: Fang
authors.forename: Peter H
authors.initials: PH
authors.lastname: Duffy
authors.forename: Charlotte A
authors.initials: CA
authors.lastname: Peterson
authors.forename: Marjorie L
authors.initials: ML
authors.lastname: Beggs
authors.forename: James C
authors.initials: JC
authors.lastname: Fuscoe
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D015870:Gene Expression; D008099:Liver / Q000378:metabolism*; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D051381:Rats; D011916:Rats, Inbred F344