Long-term monitoring of circadian rhythms in c-fos gene expression from suprachiasmatic nucleus cultures.
BACKGROUND
The AP-1 family of transcription factors has been implicated in the control of the expression of many genes in response to environmental signals. Previous studies have provided temporal profiles for c-fos expression by taking measurements from many animals at several points in time, but these studies provide limited information about dynamic changes in expression. Here, we have devised a method of continuously measuring c-fos expression.


RESULTS
A transgenic mouse line expressing the human c-fos promoter linked to the firefly luciferase reporter gene (fos/luc) was generated to continuously monitor c-fos gene expression. A second transgenic mouse line expressing luciferase under the control of the cytomegalovirus promoter (CMV/luc) served as a control. Luminescence originating from identifiable brain regions was imaged from fos/luc brain slice cultures. Expression of the fos/luc transgene accurately reflected transcriptional responses of the endogenous c-fos gene. Dynamic changes in fos/luc expression in suprachiasmatic nuclei (SCN) explant cultures were monitored continuously, and luminescence showed almost 24 hour rhythms lasting up to five circadian cycles. In contrast, bioluminescence monitored from CMV/luc SCN explant cultures was not rhythmic.


CONCLUSIONS
The fos/luc transgenic mouse will be useful for long-term, non-invasive monitoring of c-fos transcriptional responses to the changing cellular environment. Circadian rhythms in c-fos expression can be monitored non-invasively in real time from the SCN, clearly demonstrating that c-fos transcription is regulated by the circadian clock.
Geusz
M E
ME
NSF Center for Biological Timing, University of Virginia, Charlottesville 22903, USA. meg7u@virginia.edu
Fletcher
C
C
Block
G D
GD
Straume
M
M
Copeland
N G
NG
Jenkins
N A
NA
Kay
S A
SA
Day
R N
RN
D000818:Animals; D002940:Circadian Rhythm; D003587:Cytomegalovirus / Q000235:genetics; D017930:Genes, Reporter; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008163:Luminescent Measurements; D051379:Mice; D008822:Mice, Transgenic; D011401:Promoter Regions, Genetic; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*
D016760:Proto-Oncogene Proteins c-fos; D011993:Recombinant Fusion Proteins; D008156:Luciferases