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G. Ruan, D.–Q. Zhang, D.G. McMahon; Circadian Clock Gene Expression Profiling in the Mouse Retina . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3996.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: There is good evidence for the existence of one or multiple circadian clocks in the mammalian retina. However, the cellular localization of the clock(s) in the mammalian retina remains unclear so far. Here we studied the expression profiles at the single cell level of six central clock genes, namely of Per1, Per2, Cry1, Cry2, Clock, and Bmal1, in five cell types of the mouse retina. Methods: Totally 31 rods, 25 rod bipolar cells, 29 dopaminergic amacrine (DA) cells, 18 type 2 catecholamine cells, and 22 ganglion cells were harvested at Zeitgeber time 6 with our modified cell harvesting technique. Clock gene transcripts in these individual cells were studied using TaqMan real–time RT–PCR. Amplification products were further confirmed by agarose gel electrophoresis. The single–cell real–time PCR results were subject to Chi–square test and Fisher’s exact test. Results: We found all the six clock genes were expressed in the five cell populations. However, the clock gene expression pattern in rods was different from the pattern in inner retina cells. Rods expressed clock gene overall at a significantly lower frequency than the four types of inner retina cells (P<0.001). Also, except for Bmal1, expression frequency of each individual clock gene in the inner retina cells were significantly higher than those in rods (P<0.01). Furthermore, compared to rods, individual inner retina cells were more likely to express all the six clock genes or multiple clock genes that are sufficient to comprise a circadian oscillator (P<0.01). Conclusions: Our current results indicate that in the mammalian retina, multiple types of inner retinal neurons, including DA cells and ganglion cells, express sufficient gene components to be circadian clock neurons, whereas rod photoreceptors do not.
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