Clock gene expression in the murine gastrointestinal tract: endogenous rhythmicity and effects of a feeding regimen.
OBJECTIVE
Based on observations that the gastrointestinal tract is subject to various 24-hour rhythmic processes, it is conceivable that some of these rhythms are under circadian clock gene control. We hypothesized that clock genes are present in the gastrointestinal tract and that they are part of a functional molecular clock that coordinates rhythmic physiologic functions.


METHODS
The effects of timed feeding and vagotomy on temporal clock gene expression (clock, bmal1, per1-3, cry1-2) in the gastrointestinal tract and suprachiasmatic nucleus (bmal, per2) of C57BL/6J mice were examined using real-time polymerase chain reaction and Western blotting (BMAL, PER2). Colonic clock gene localization was examined using immunohistochemistry (BMAL, PER1-2).


RESULTS
Clock immunoreactivity was observed in the myenteric plexus and epithelial crypt cells. Clock genes were expressed rhythmically throughout the gastrointestinal tract. Timed feeding shifted clock gene expression at the RNA and protein level but did not shift clock gene expression in the central clock. Vagotomy did not alter gastric clock gene expression compared with sham-treated controls.


CONCLUSIONS
The murine gastrointestinal tract contains functional clock genes, which are molecular core components of the circadian clock. Daytime feeding in nocturnal rodents is a strong synchronizer of gastrointestinal clock genes. This synchronization occurs independently of the central clock. Gastric clock gene expression is not mediated through the vagal nerve. The presence of clock genes in the myenteric plexus and epithelial cells suggests a role for clock genes in circadian coordination of gastrointestinal functions such as motility, cell proliferation, and migration.
Hoogerwerf
Willemijntje A
WA
Department of Internal Medicine, Division of Gastroenterology, University of Michigan, VA Ann Arbor Healthcare System, Ann Arbor, Michigan 48105, USA. willemij@umich.edu
Hellmich
Helen L
HL
Cornélissen
Germaine
G
Halberg
Franz
F
Shahinian
Vahakn B
VB
Bostwick
Jonathon
J
Savidge
Tor C
TC
Cassone
Vincent M
VM
D056930:ARNTL Transcription Factors; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002940:Circadian Rhythm / Q000235:genetics*; D003106:Colon / Q000166:cytology / Q000294:innervation / Q000378:metabolism*; D056931:Cryptochromes; D004847:Epithelial Cells / Q000378:metabolism*; D005247:Feeding Behavior; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism; D005753:Gastric Mucosa / Q000378:metabolism*; D005786:Gene Expression Regulation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009197:Myenteric Plexus / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D056950:Period Circadian Proteins; D013270:Stomach / Q000166:cytology / Q000294:innervation; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014628:Vagotomy; D014630:Vagus Nerve / Q000601:surgery
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins; D056931:Cryptochromes; D005420:Flavoproteins; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C538961:Bmal1 protein, mouse; C538964:Cry1 protein, mouse; C539023:Per1 protein, mouse; C513312:Per2 protein, mouse; C512645:Per3 protein, mouse; C538944:Clock protein, mouse