Two-peaked synchronization in day/night expression rhythms of the fibrinogen gene cluster in the mouse liver.
Genes expressed with day/night rhythms in the mouse liver were searched for by microarray analysis using an in-house array harboring mouse liver cDNAs. The rhythmic expression with a single peak and trough level was confirmed by RNA blot analysis for 3beta-Hsd and Gabarapl1 genes exhibiting a peak in the light phase and Spot14, Hspa8, Hspa5, and Hsp84-1 genes showing a peak in the dark phase. On the other hand, mRNA levels for all of the three fibrinogen subunits, Aalpha, Bbeta and gamma, exhibited two peaks each in the light and dark phases in a synchronized manner. This two-peaked rhythmic pattern of fibrinogen genes as well as the single peak-trough pattern of other genes was diminished or almost completely lost in the liver of Clock mutant mice, suggesting that the two-peaked expression is also under the control of oscillation-generating genes. In constant darkness, the first peak of the expression rhythm of fibrinogen genes was almost intact, but the second peak disappeared. Therefore, although the first peak in the subjective day is a component of the innate circadian rhythm, the second peak seems to require light stimuli. Fasting in constant darkness caused shifts of time phases of the circadian rhythms. Protein levels of the fibrinogen subunits in whole blood also exhibited circadian rhythms. In the mouse and human loci of the fibrinogen gene cluster, a number of sequence elements resembling circadian transcription factor-binding sites were found. The fibrinogen gene locus provides a unique system for the study of two-peaked day/night rhythms of gene expression in a synchronized form.
Department of Biochemistry, Chiba University Graduate School of Medicine, Chiba 260-8670, Japan.
Eiko
E
Sakao
Akinori
A
Ishihara
Kazumasa
K
Horikawa
Masashi
M
Akiyama
Makoto
M
Arai
Masaki
M
Kato
Naohiko
N
Seki
Kohji
K
Fukunaga
Atsuko
A
Shimizu-Yabe
Katsuro
K
Iwase
Satoko
S
Ohtsuka
Takeyuki
T
Sato
Yoichi
Y
Kohno
Shigenobu
S
Shibata
Masaki
M
Takiguchi
D000818:Animals; D002874:Chromosome Mapping; D033481:Chromosomes, Mammalian; D002940:Circadian Rhythm / Q000502:physiology*; D000091342:Endoplasmic Reticulum Chaperone BiP; D005340:Fibrinogen / Q000235:genetics*; D005786:Gene Expression Regulation / Q000502:physiology; D008099:Liver / Q000502:physiology*; D008297:Male; D051379:Mice; D005810:Multigene Family / Q000502:physiology; D020411:Oligonucleotide Array Sequence Analysis
D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; C000717248:Hspa5 protein, mouse; D005340:Fibrinogen