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Chi Hoang Viet Vu, Motoko Kawashima, Akiko Ito, Kokoro Sano, Kazuo Tsubota; Analysis of Circadian Rhythm Gene Expression of Lacrimal Glands in Mice. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3078.
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© ARVO (1962-2015); The Authors (2016-present)
The molecular basis for diurnal variation in tear secretion is not fully understood. We hypothesized that local expression of circadian rhythm clock genes in the lacrimal gland (LG) may contribute to the 24-hour pattern of tear secretion. We investigated the circadian rhythm gene expression of LGs in mice.
Male C57BL/6JJcl mice were kept under a 12-h light / 12-h dark (LD) cycle, with the light on from 8:00 to 20:00 for 2 weeks. The mice were sacrificed and the LGs were removed at Zeitgeber time (ZT) 0, 4, 8, 12, 16, and 20 h for gene expression analysis (n=5 per group). ZT0 was defined as the time of light onset and ZT12 as the time of dark onset. Total RNA was extracted from the LGs of mice, then real time PCR was performed for CLOCK, BMAL1, PER1 and PER2 genes linked to circadian rhythm.
In the real time PCR, CLOCK expression significantly decreased at ZT8, ZT12, ZT16, and ZT20 compared to ZT0 (P<0.05, P<0.01, P<0.01, P<0.05, respectively). BMAL1 expression also significantly decreased at ZT4, ZT8, ZT12, ZT16, and ZT20 compared to ZT0 (P<0.01, P<0.01, P<0.01, P<0.01, P<0.01, respectively). Moreover PER1 expression significantly decreased at ZT20 compared to ZT0 (P<0.05), while, PER2 expression significantly increased at ZT8, ZT12, and ZT16 compared to ZT0 (P<0.01, P<0.01, P<0.01, respectively).
The expression levels of clock genes showed evident diurnal variations in the LG. Future studies are required to investigate how regulation of these clock genes may contribute to the daily circadian rhythm variation in tear secretion.
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