Clock genes show circadian rhythms in salivary glands.
Circadian rhythms are endogenous self-sustained oscillations with 24-hour periods that regulate diverse physiological and metabolic processes through complex gene regulation by "clock" transcription factors. The oral cavity is bathed by saliva, and its amount and content are modified within regular daily intervals. The clock mechanisms that control salivary production remain unclear. Our objective was to evaluate the expression and periodicity of clock genes in salivary glands. Real-time quantitative RT-PCR, in situ hybridization, and immunohistochemistry were performed to show circadian mRNA and protein expression and localization of key clock genes (Bmal1, Clock, Per1, and Per2), ion and aqua channel genes (Ae2a, Car2, and Aqp5), and salivary gland markers. Clock gene mRNAs and clock proteins were found differentially expressed in the serous acini and duct cells of all major salivary glands. The expression levels of clock genes and Aqp5 showed regular oscillatory patterns under both light/dark and complete-dark conditions. Bmla1 overexpression resulted in increased Aqp5 expression levels. Analysis of our data suggests that salivary glands have a peripheral clock mechanism that functions both in normal light/dark conditions and in the absence of light. This finding may increase our understanding of the control mechanisms of salivary content and flow.
Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor, MI, USA.
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Zheng
Y J
YJ
Seon
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J
McHugh
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Papagerakis
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P
Papagerakis
D056930:ARNTL Transcription Factors / Q000032:analysis; D000818:Animals; D027321:Anion Transport Proteins / Q000032:analysis; D017920:Antiporters / Q000032:analysis; D051402:Aquaporin 5 / Q000032:analysis; D020346:Aquaporins / Q000032:analysis; D056926:CLOCK Proteins / Q000032:analysis; D002256:Carbonic Anhydrases / Q000032:analysis; D057906:Circadian Clocks / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics*; D005786:Gene Expression Regulation / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D009077:Mucins / Q000032:analysis; D056950:Period Circadian Proteins / Q000032:analysis; D064606:SLC4A Proteins; D012463:Saliva / Q000737:chemistry; D012469:Salivary Glands / Q000378:metabolism*; D027982:Sodium-Bicarbonate Symporters / Q000032:analysis; D014157:Transcription Factors / Q000032:analysis
C496036:AQP5 protein, human; D056930:ARNTL Transcription Factors; C538960:BMAL1 protein, human; D027321:Anion Transport Proteins; D017920:Antiporters; D051402:Aquaporin 5; D020346:Aquaporins; C538961:Bmal1 protein, mouse; D009077:Mucins; C539022:PER1 protein, human; C421902:PER2 protein, human; C539023:Per1 protein, mouse; C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D064606:SLC4A Proteins; C491421:Smgc protein, mouse; D027982:Sodium-Bicarbonate Symporters; D014157:Transcription Factors; D056926:CLOCK Proteins; C538943:CLOCK protein, human; C538944:Clock protein, mouse; D002256:Carbonic Anhydrases