Identification of novel light-induced genes in the suprachiasmatic nucleus.
BACKGROUND
The transmission of information about the photic environment to the circadian clock involves a complex array of neurotransmitters, receptors, and second messenger systems. Exposure of an animal to light during the subjective night initiates rapid transcription of a number of immediate-early genes in the suprachiasmatic nucleus of the hypothalamus. Some of these genes have known roles in entraining the circadian clock, while others have unknown functions. Using laser capture microscopy, microarray analysis, and quantitative real-time PCR, we performed a comprehensive screen for changes in gene expression immediately following a 30 minute light pulse in suprachiasmatic nucleus of mice.


RESULTS
The results of the microarray screen successfully identified previously known light-induced genes as well as several novel genes that may be important in the circadian clock. Newly identified light-induced genes include early growth response 2, proviral integration site 3, growth-arrest and DNA-damage-inducible 45 beta, and TCDD-inducible poly(ADP-ribose) polymerase. Comparative analysis of promoter sequences revealed the presence of evolutionarily conserved CRE and associated TATA box elements in most of the light-induced genes, while other core clock genes generally lack this combination of promoter elements.


CONCLUSIONS
The photic signalling cascade in the suprachiasmatic nucleus activates an array of immediate-early genes, most of which have unknown functions in the circadian clock. Detected evolutionary conservation of CRE and TATA box elements in promoters of light-induced genes suggest that the functional role of these elements has likely remained the same over evolutionary time across mammalian orders.
Porterfield
Veronica M
VM
School of Biomedical Sciences, Kent State University, Kent, OH 44242 USA. vporterf@kent.edu
Piontkivska
Helen
H
Mintz
Eric M
EM
D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics; D015870:Gene Expression; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D017781:Genes, Immediate-Early; D007834:Lasers; D008027:Light; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D042282:Microdissection; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013493:Suprachiasmatic Nucleus / Q000502:physiology*; D016385:TATA Box / Q000235:genetics; D014158:Transcription, Genetic
D017362:Cyclic AMP Response Element-Binding Protein