Background-Circadian rhythmicity of many aspects of cardiovascular function-blood pressure, coagulation and contractile function-is well established, as is diurnal variation in important clinical events, such as myocardial infarction and stroke. Here, we undertake studies to globally assess circadian gene expression in murine aorta. Methods and Results-Aortae from mice were harvested at 4-hour intervals for 2 circadian cycles (48 hours). Gene expression was assessed by expression profiling and

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... ubjected to a gene ontology bioinformatics analysis. Three hundred thirty transcripts exhibited a circadian pattern of oscillation in mouse aorta, including those intrinsic to the function of the molecular clock. In addition, many genes relevant to protein folding, protein degradation, glucose and lipid metabolism, adipocyte maturation, vascular integrity, and the response to injury are also included in this subset of roughly 7000 genes screened for circadian oscillation. Conclusions-Detection of functional cassettes of vascular genes that exhibit circadian regulation in the mouse will facilitate elucidation of the mechanisms by which the molecular clock may interact with environmental variables to modulate cardiovascular function and the response to therapeutic interventions. (Circulation. 2005;112:2716-2724.) Key Words: aorta Ⅲ circadian rhythm Ⅲ metabolism Ⅲ vasculature Ⅲ genes Data Analysis All protocols were conducted as described in the Affymetrix Gene-Chip Expression Analysis Technical Manual. Affymetrix Microarray Suite 4.0 was used to quantify expression levels for targeted genes; default values provided by Affymetrix were applied to all analysis parameters. Briefly, border pixels were removed, and the average intensity of pixels within the 75th percentile was computed for each ( P.M.); the Salk Institute for Biological Studies, La Jolla, Calif (S.P.); and Scripps Florida, Jupiter, Fla (J.B.H.). The online-only Data Supplement can be found at http://circ.ahajournals.org/cgi/content/full/CIRCULATIONAHA.105.568626/DC1.